Volume 36,Issue 5,2008 Table of Contents
2008, 36(5):515-519.
Abstract:
An analysis is made of the main causes, weather patterns, singlestation influencing factors and physical parameters of four severe convective weather events in 2004 in Zhengzhou by using routine meteorological data and 1°×1° reanalysis data of NCEP. The results show that it is favorable to the occurrence of severe convective weather that there is radiative warming at lower levels and coldadvection cooling at upper levels while under the control of northwest air flow or the North China low, in which convective energy increases quickly. The mesoscale convergence line appeared on the surface three hours ahead is the triggering mechanism of severe convection weather. The vertical distribution characteristics of singlestation 〖WTBX〗θ〖WTBZ〗se, atmospheric entropyremoving index, vertical wind shear, precipitable water, etc., can be used to judge the type of severe convection weather.
An analysis is made of the main causes, weather patterns, singlestation influencing factors and physical parameters of four severe convective weather events in 2004 in Zhengzhou by using routine meteorological data and 1°×1° reanalysis data of NCEP. The results show that it is favorable to the occurrence of severe convective weather that there is radiative warming at lower levels and coldadvection cooling at upper levels while under the control of northwest air flow or the North China low, in which convective energy increases quickly. The mesoscale convergence line appeared on the surface three hours ahead is the triggering mechanism of severe convection weather. The vertical distribution characteristics of singlestation 〖WTBX〗θ〖WTBZ〗se, atmospheric entropyremoving index, vertical wind shear, precipitable water, etc., can be used to judge the type of severe convection weather.
2008, 36(5):520-523.
Abstract:
The graded precipitation and rainy/fine forecasting experiments are conducted by means of several consensus methods such as majority voting, weighted scoring, and multivariable regression on precipitation caused by weather systems from west in Chengde. The results indicate that when there is relative high individual TS’s and slightly varied total forecasting performance, the majority voting method can improve the forecasting accuracy greatly; when the accuracies of various numerical forecasting methods for graded precipitation forecasting varied greatly, the weighted scoring method performed better; when there are enough samples, the refined repression method is more feasible for rainy/fine forecasting and graded precipitation forecast.
The graded precipitation and rainy/fine forecasting experiments are conducted by means of several consensus methods such as majority voting, weighted scoring, and multivariable regression on precipitation caused by weather systems from west in Chengde. The results indicate that when there is relative high individual TS’s and slightly varied total forecasting performance, the majority voting method can improve the forecasting accuracy greatly; when the accuracies of various numerical forecasting methods for graded precipitation forecasting varied greatly, the weighted scoring method performed better; when there are enough samples, the refined repression method is more feasible for rainy/fine forecasting and graded precipitation forecast.
2008, 36(5):524-528.
Abstract:
The nowcasting methods and techniques for largearea rainfall, such as Meiyufront heavy rainfall, are studied on the basis of CHINA/SA radar data. The techniques of multiscale filtering, segmentation, and radar echo matching are discussed according to the characteristics of heavy rainfall echoes. By using the life time of a certain scale echo to restrict the lead time, a forecast can be made for the rainfall at this scale, and total rainfall is obtained through composing. The results show that the accuracy of rainfall forecasting is improved, to some extent, while considering the differences in life time between the echoes of different scales and the moving characteristics.
The nowcasting methods and techniques for largearea rainfall, such as Meiyufront heavy rainfall, are studied on the basis of CHINA/SA radar data. The techniques of multiscale filtering, segmentation, and radar echo matching are discussed according to the characteristics of heavy rainfall echoes. By using the life time of a certain scale echo to restrict the lead time, a forecast can be made for the rainfall at this scale, and total rainfall is obtained through composing. The results show that the accuracy of rainfall forecasting is improved, to some extent, while considering the differences in life time between the echoes of different scales and the moving characteristics.
2008, 36(5):529-535.
Abstract:
The heavy rain process in the southern Guizhou Province during 24, 25 June 2007 was simulated successfully by using the threelevel nested mesoscale numerical model MM5 V3.5. By means of the simulated high resolution output data, the formation mechanisms of a heavy rain and the mesoscale low vortex were analyzed and diagnosed. It is shown that the model can successfully simulate the development of mesoscale systems and the distribution characteristics of precipitation. The development and maintenance of a mesoscale low vortex is the direct cause of the heavy rain. Heavy rainfall occurred in the southwest of a low vortex. A deep ascending motion column formed under the favorable condition: atmosphere positive vorticity, convergence, and strong ascending motion at lowerlevels, while atmosphere negative vorticity and divergence at upper levels. The mesoscale dynamical structure had a good relation to the occurrence time and location of heavy rainfall and was one of the dynamic mechanisms of maintaining and growing of the mesoscale low vortex. The area of heavy rainfall corresponded well to the strong ascending motion and the positive vortex areas.
The heavy rain process in the southern Guizhou Province during 24, 25 June 2007 was simulated successfully by using the threelevel nested mesoscale numerical model MM5 V3.5. By means of the simulated high resolution output data, the formation mechanisms of a heavy rain and the mesoscale low vortex were analyzed and diagnosed. It is shown that the model can successfully simulate the development of mesoscale systems and the distribution characteristics of precipitation. The development and maintenance of a mesoscale low vortex is the direct cause of the heavy rain. Heavy rainfall occurred in the southwest of a low vortex. A deep ascending motion column formed under the favorable condition: atmosphere positive vorticity, convergence, and strong ascending motion at lowerlevels, while atmosphere negative vorticity and divergence at upper levels. The mesoscale dynamical structure had a good relation to the occurrence time and location of heavy rainfall and was one of the dynamic mechanisms of maintaining and growing of the mesoscale low vortex. The area of heavy rainfall corresponded well to the strong ascending motion and the positive vortex areas.
2008, 36(5):536-540.
Abstract:
Local heavy rainfall occurred over the Qinling and Bashan mountainous area is one of typical meteorological disasters in the eastern Tibetan Plateau. According to the data from routine meteorological observation, the analysis of the heavy rainfall process from 1 to 10 July 2005 in the Qinling and Bashan mountainous area is conducted with the emphasis on the localarea heavy rainfall at the night of 8 July 2005. Using the new generation mesoscale model of the Weather Research and Forecast (WRFV2.1) model, the a mesoscale numerical simulation of the heavy storm rainfall during 8 July 2005 is carried out. It is found that the continuous rainy weather occurred in the favorable background：the existence of relatively stable subtropical high. The simulation results show that a mesoscale lowlevel jet can enhance and accelerate the occurrence and development of mesoscale systems; the convergence at low levels and divergence at higher levels are the dynamical conditions of rainfall systems.
Local heavy rainfall occurred over the Qinling and Bashan mountainous area is one of typical meteorological disasters in the eastern Tibetan Plateau. According to the data from routine meteorological observation, the analysis of the heavy rainfall process from 1 to 10 July 2005 in the Qinling and Bashan mountainous area is conducted with the emphasis on the localarea heavy rainfall at the night of 8 July 2005. Using the new generation mesoscale model of the Weather Research and Forecast (WRFV2.1) model, the a mesoscale numerical simulation of the heavy storm rainfall during 8 July 2005 is carried out. It is found that the continuous rainy weather occurred in the favorable background：the existence of relatively stable subtropical high. The simulation results show that a mesoscale lowlevel jet can enhance and accelerate the occurrence and development of mesoscale systems; the convergence at low levels and divergence at higher levels are the dynamical conditions of rainfall systems.
2008, 36(5):541-546.
Abstract:
According to the moist potential vorticity theory, three hailgale events occurred in Guangxi in April 2006 are diagnosed and analyzed in detail. The results show that the convective stability was very small around the area with dense moist potential temperature isopleths; the absolute vorticity increased during the process of cold air moving downward along the isoentrope surface, leading to the increasing of cyclonic vorticity, which is favorable to the occurrence of hail and gale weather. It is found that there is high MPV (moist potential vorticity) descending downward from the upper troposphere before the hail and gale events; and in the areas with dense barotropic MPV isopleths (around the zero line) and around baroclinic MPV negative centers on the 925 hPa level, heavy convection occurs at a higher probability.
According to the moist potential vorticity theory, three hailgale events occurred in Guangxi in April 2006 are diagnosed and analyzed in detail. The results show that the convective stability was very small around the area with dense moist potential temperature isopleths; the absolute vorticity increased during the process of cold air moving downward along the isoentrope surface, leading to the increasing of cyclonic vorticity, which is favorable to the occurrence of hail and gale weather. It is found that there is high MPV (moist potential vorticity) descending downward from the upper troposphere before the hail and gale events; and in the areas with dense barotropic MPV isopleths (around the zero line) and around baroclinic MPV negative centers on the 925 hPa level, heavy convection occurs at a higher probability.
2008, 36(5):547-550.
Abstract:
A set of practical skills for determining the intensities of tropical cyclones is summed up on the basis of experiences of more than 20 years, i.e., to estmate the tropical cyclone intensity, the shortterm moving trend and the influence on wind and rainfall. The impacts of the continent or large islands on cloud types of tropical cyclones are divided in four categories by severity: slight, moderate, serious, and severe. The basic cloud types of 10 kinds that can be used to estimate the shortterm movement of tropical cyclones, as well as the intensity, duration, and mode of influencing, are described. The structure of cloud types on cloud pictures is considerably indicative of the impacts of tropical cyclones on winds and rainfall.
A set of practical skills for determining the intensities of tropical cyclones is summed up on the basis of experiences of more than 20 years, i.e., to estmate the tropical cyclone intensity, the shortterm moving trend and the influence on wind and rainfall. The impacts of the continent or large islands on cloud types of tropical cyclones are divided in four categories by severity: slight, moderate, serious, and severe. The basic cloud types of 10 kinds that can be used to estimate the shortterm movement of tropical cyclones, as well as the intensity, duration, and mode of influencing, are described. The structure of cloud types on cloud pictures is considerably indicative of the impacts of tropical cyclones on winds and rainfall.
2008, 36(5):551-555.
Abstract:
An analysis is made of the characteristics of the spatialtemporal distribution of droughts and the change tendency based on statistical data of droughts in China in the last 60 years. The results indicate that the droughtattacked areas, droughtinundated area, and economic loss showed an increasing trend in the past 60 years, and the frequency of droughts also increased. Northwest China, North China, and Mongolia are severe droughtattacked regions, and Mongolia, Shan’xi, Shaanxi, Ningxia, Jilin are the most severe droughtattacked provinces. The fractal characteristics of drought disasters in the time series are studied, based on the fractal dimension theory, with the fractal dimension of drought in China being 1.73, which means that a severe flood disaster is a chaotic system.
An analysis is made of the characteristics of the spatialtemporal distribution of droughts and the change tendency based on statistical data of droughts in China in the last 60 years. The results indicate that the droughtattacked areas, droughtinundated area, and economic loss showed an increasing trend in the past 60 years, and the frequency of droughts also increased. Northwest China, North China, and Mongolia are severe droughtattacked regions, and Mongolia, Shan’xi, Shaanxi, Ningxia, Jilin are the most severe droughtattacked provinces. The fractal characteristics of drought disasters in the time series are studied, based on the fractal dimension theory, with the fractal dimension of drought in China being 1.73, which means that a severe flood disaster is a chaotic system.
2008, 36(5):556-560.
Abstract:
The temporal and spatial distribution characteristics and variation of heavy fog days in China are analyzed by using the data of visibility and relative humidity of 541 ground stations over China from 1961 to 2005. The results show that there is obviously more heavy fog days in the winter half year than in the summer half year, the most in November and the least June. The spatial distribution shows that the annual mean fog days are much more in the eastern China, and obviously less in the most parts of Inner Mongolia and the western China, with the annual mean number of fog days less than 1 day mostly. Heavy fogs occur frequently, and there was obvious increasing and fluctuating trends in annual fog days with a period of about 1.5 years in the middle and lower reaches of the Yangtze River and some parts of the Huanghuai region. The years of 1982, 1987, 1989 to 2000, and 2002 were morethannormal years, and 1967 was a lessthannormal year.
The temporal and spatial distribution characteristics and variation of heavy fog days in China are analyzed by using the data of visibility and relative humidity of 541 ground stations over China from 1961 to 2005. The results show that there is obviously more heavy fog days in the winter half year than in the summer half year, the most in November and the least June. The spatial distribution shows that the annual mean fog days are much more in the eastern China, and obviously less in the most parts of Inner Mongolia and the western China, with the annual mean number of fog days less than 1 day mostly. Heavy fogs occur frequently, and there was obvious increasing and fluctuating trends in annual fog days with a period of about 1.5 years in the middle and lower reaches of the Yangtze River and some parts of the Huanghuai region. The years of 1982, 1987, 1989 to 2000, and 2002 were morethannormal years, and 1967 was a lessthannormal year.
2008, 36(5):561-566.
Abstract:
The NCEP/NCAR and JTWC (Joint Typhoon Warning Center) reanalysis data are used to investigate the trends of the frequency, distribution and oscillation periods of maximum wind speed and environmentalwind vertical shear of tropical cyclones over the Northwestern Pacific from May to October, 1974 to 2004. Results show that there are contrary variation trends between maximum wind speed and environmentalwind vertical shear. The weak vertical shear is propitious to the development of tropical cyclones. The impact of the vertical shear on intensity variation of tropical cyclones at 12 hours before is the greatest. In strong TC years, the environmentalwind vertical shear is relatively small, and there are more tropical cyclones; while in weak TC years, the environmentalwind vertical shear is large, and there are less tropical cyclones.
The NCEP/NCAR and JTWC (Joint Typhoon Warning Center) reanalysis data are used to investigate the trends of the frequency, distribution and oscillation periods of maximum wind speed and environmentalwind vertical shear of tropical cyclones over the Northwestern Pacific from May to October, 1974 to 2004. Results show that there are contrary variation trends between maximum wind speed and environmentalwind vertical shear. The weak vertical shear is propitious to the development of tropical cyclones. The impact of the vertical shear on intensity variation of tropical cyclones at 12 hours before is the greatest. In strong TC years, the environmentalwind vertical shear is relatively small, and there are more tropical cyclones; while in weak TC years, the environmentalwind vertical shear is large, and there are less tropical cyclones.
2008, 36(5):567-569.
Abstract:
An analysis is made of the statistical characteristics of the spatial distribution, annual distribution and variation, and daily change of hailing days, as well as hailing duration, with the hail data of recent 46 years from 20 meteorological stations in Ningxia and NCEP/NCAR reanalysis data. The analysis shows that hailing days reached the peak in the 1980s; hail storms occurred mostly from April to September; the southern Ningxia was the most frequently attacked area by hail storms; the number of hailing days, the area of hailing in the same day, hailing duration, and the maximum diameter of hailstones all show a decreasing trend from the 1990s.
An analysis is made of the statistical characteristics of the spatial distribution, annual distribution and variation, and daily change of hailing days, as well as hailing duration, with the hail data of recent 46 years from 20 meteorological stations in Ningxia and NCEP/NCAR reanalysis data. The analysis shows that hailing days reached the peak in the 1980s; hail storms occurred mostly from April to September; the southern Ningxia was the most frequently attacked area by hail storms; the number of hailing days, the area of hailing in the same day, hailing duration, and the maximum diameter of hailstones all show a decreasing trend from the 1990s.
2008, 36(5):570-574.
Abstract:
The statistic characteristics of hourly precipitation are preliminarily analyzed on basis of automatic rain gauge records from 95 weather stations from April to October, 1999 to 2005 in the midsouthern Hebei Province. The spatial distributional characteristics and basic statistic regularities of hourly precipitation are obtained. It is found out that the distribution of hourly precipitation has obvious geographical and seasonal features; the intensity is generally the largest at dawn or in dusk, and the smallest in the morning. The color scale of the radar precipitation product is adjusted according to the distribution of rainfall measurement, whereby the interval is shorten in the small value range and lengthened in the large range, which can highlight the levels of little values in rainfall display, and can track the genesis, evolution, and movement of rainfall centers. The product has certain significance to the refine precipitation forecasting.
The statistic characteristics of hourly precipitation are preliminarily analyzed on basis of automatic rain gauge records from 95 weather stations from April to October, 1999 to 2005 in the midsouthern Hebei Province. The spatial distributional characteristics and basic statistic regularities of hourly precipitation are obtained. It is found out that the distribution of hourly precipitation has obvious geographical and seasonal features; the intensity is generally the largest at dawn or in dusk, and the smallest in the morning. The color scale of the radar precipitation product is adjusted according to the distribution of rainfall measurement, whereby the interval is shorten in the small value range and lengthened in the large range, which can highlight the levels of little values in rainfall display, and can track the genesis, evolution, and movement of rainfall centers. The product has certain significance to the refine precipitation forecasting.
2008, 36(5):575-580.
Abstract:
The temporal and spatial variation of summer precipitation and the daily variation of clouds and wind direction are analyzed with the 50year climate data from the topographiccloud experiment area in Qilian Mountain. The result shows that the precipitation in the experiment area increased from north to south with increasing altitude. The observed maximum annual precipitation is 511 mm, occuring in Wafangcheng at 2500 m (ASL). The amount of precipitation in July is the biggest, while that from June to August is about 57% of annual precipitation. There is obvious daily variation in wind direction in summer, with mountainvalley circulations dominating. The most frequent wind direction is northwest in daytime and south to southeast in nighttime. Valley winds after noon make vapor converged in the hillside of Qilian Mountain to produce ascending airflow, further convective clouds. As the result, the precipitation frequency is the highest, and two precipitation peaks appear in midnight and noon, respectively, corresponding to daily variations of low cloud, cumulus and cumulonimbus amounts. The climate change of 50 years shows that annual precipitation has an increasing trend; there were two wet periods and two dry periods from 1957 to 2004; it has been in wet periods from 1998 till now. The analyses of annual precipitation and the biggest entropy spectra of annual runoff show that there are obvious periods of 4.8 years and 3 years, and the annual precipitation at Minle has a good relationship with entropy spectra.
The temporal and spatial variation of summer precipitation and the daily variation of clouds and wind direction are analyzed with the 50year climate data from the topographiccloud experiment area in Qilian Mountain. The result shows that the precipitation in the experiment area increased from north to south with increasing altitude. The observed maximum annual precipitation is 511 mm, occuring in Wafangcheng at 2500 m (ASL). The amount of precipitation in July is the biggest, while that from June to August is about 57% of annual precipitation. There is obvious daily variation in wind direction in summer, with mountainvalley circulations dominating. The most frequent wind direction is northwest in daytime and south to southeast in nighttime. Valley winds after noon make vapor converged in the hillside of Qilian Mountain to produce ascending airflow, further convective clouds. As the result, the precipitation frequency is the highest, and two precipitation peaks appear in midnight and noon, respectively, corresponding to daily variations of low cloud, cumulus and cumulonimbus amounts. The climate change of 50 years shows that annual precipitation has an increasing trend; there were two wet periods and two dry periods from 1957 to 2004; it has been in wet periods from 1998 till now. The analyses of annual precipitation and the biggest entropy spectra of annual runoff show that there are obvious periods of 4.8 years and 3 years, and the annual precipitation at Minle has a good relationship with entropy spectra.
2008, 36(5):581-586.
Abstract:
A sanddust weather event in Northwest China was diagnosed and analyzed by means of the routine observation data and WRF model outputs. The results show that this event belongs to Mongolia Cold Trough, and the main cause of the sanddust event was the invasion of strong coldair mass on surface, in which the sanddust weather occurred at the rear of a ground cold front during the transit of the front. The development and movement of the upperlevel jet was indicative of sanddust weather. The vertical secondary circulation changed evidently at the same time, and ascending and descending air currents coexisted. The matchable divergence field enhanced the ascending and descending movement. The vorticity field was important because it could affect the Mongolia Cyclogenesis. The stable stratification and distinct lowlevel vertical wind shear were two features during the sanddust event. The WRF model performed well in predicting this event.
A sanddust weather event in Northwest China was diagnosed and analyzed by means of the routine observation data and WRF model outputs. The results show that this event belongs to Mongolia Cold Trough, and the main cause of the sanddust event was the invasion of strong coldair mass on surface, in which the sanddust weather occurred at the rear of a ground cold front during the transit of the front. The development and movement of the upperlevel jet was indicative of sanddust weather. The vertical secondary circulation changed evidently at the same time, and ascending and descending air currents coexisted. The matchable divergence field enhanced the ascending and descending movement. The vorticity field was important because it could affect the Mongolia Cyclogenesis. The stable stratification and distinct lowlevel vertical wind shear were two features during the sanddust event. The WRF model performed well in predicting this event.
2008, 36(5):587-591.
Abstract:
The climate characteristics, formation causes, and main circulation patterns of high temperature weather in Jieyang, Gangdong Province, are summarized on the basis of the analysis of high temperature weather from 1966 to 2006. The results indicate that the number of high temperature days in Jieyang has obvious time variation: below the normal before the 1990’s, steady around the normal from 1990 to 1997, obviously above the normal since 1998 with an increased intensity, which connected with not only global warming and urban heat island effect, but also regional atmospheric circulation abnormity. The major weather systems indusing high temperature weather in Jieyang include the subtropical high and tropical cyclones, the northwest air current of which enhances temperature increase. The former often results in longenduring high temperature weather, and the latter extreme high temperature.
The climate characteristics, formation causes, and main circulation patterns of high temperature weather in Jieyang, Gangdong Province, are summarized on the basis of the analysis of high temperature weather from 1966 to 2006. The results indicate that the number of high temperature days in Jieyang has obvious time variation: below the normal before the 1990’s, steady around the normal from 1990 to 1997, obviously above the normal since 1998 with an increased intensity, which connected with not only global warming and urban heat island effect, but also regional atmospheric circulation abnormity. The major weather systems indusing high temperature weather in Jieyang include the subtropical high and tropical cyclones, the northwest air current of which enhances temperature increase. The former often results in longenduring high temperature weather, and the latter extreme high temperature.
2008, 36(5):592-595.
Abstract:
An agricultural drought model based on water budget is established, considering rainfall and crop water requirement at the same time, the special needs of agricultural production in Guangxi, and the reality of agricultural drought monitoring, and accordingly a drought index grading system is developed. Both were used to analyze the spatialtemporal distribution characteristics of the occurrence frequency of rice and sugarcane droughts in growth season in Guangxi Province in the past 44 years (1961 to 2004). Good results are obtained by using the water budget model to calculate and analyze the historical droughts in Guangxi. The near realtime drought monitoring approach can be applied to the monitoring of droughts in Guangxi. The analysis results of the seasonal spatialtemporal characteristics conform to the actual situation.
An agricultural drought model based on water budget is established, considering rainfall and crop water requirement at the same time, the special needs of agricultural production in Guangxi, and the reality of agricultural drought monitoring, and accordingly a drought index grading system is developed. Both were used to analyze the spatialtemporal distribution characteristics of the occurrence frequency of rice and sugarcane droughts in growth season in Guangxi Province in the past 44 years (1961 to 2004). Good results are obtained by using the water budget model to calculate and analyze the historical droughts in Guangxi. The near realtime drought monitoring approach can be applied to the monitoring of droughts in Guangxi. The analysis results of the seasonal spatialtemporal characteristics conform to the actual situation.
2008, 36(5):596-600.
Abstract:
Crop Water Deficit Index (CWDI) is used as a drought monitoring index to explore its applicability in different agricultural areas. The daily, seasonal and annual CWDIs from 1971 to 2000 from 18 meteorological stations distributed in different climate regions are calculated. The seasonal and regional characteristics of CWDIs are primarily analyzed. Typical drought events of these 18 meteorological stations are verified by using the departures of CWDIs as monitoring indexes, and the results show that CWDI can reveal the status of crop’s water deficiency and drought events of these stations in growing season. CWDI is quite applicable for monitoring agricultural droughts in different regions.
Crop Water Deficit Index (CWDI) is used as a drought monitoring index to explore its applicability in different agricultural areas. The daily, seasonal and annual CWDIs from 1971 to 2000 from 18 meteorological stations distributed in different climate regions are calculated. The seasonal and regional characteristics of CWDIs are primarily analyzed. Typical drought events of these 18 meteorological stations are verified by using the departures of CWDIs as monitoring indexes, and the results show that CWDI can reveal the status of crop’s water deficiency and drought events of these stations in growing season. CWDI is quite applicable for monitoring agricultural droughts in different regions.
2008, 36(5):601-605.
Abstract:
The aridity index is calculated and the dryness/wetness characteristics are analyzed based on the daily meteorological data of 104 stations from 1961 to 2006 in the Huanghuaihai region. The Huanghuaihai region is divided into five dry/wet climatic types: wet, semiwet, semiwet and semidry, semidry and semiwet, and semidry regions. The “semidry” region has the largest area compared with the other regions. There is obvious latitudinal distribution in the five climatic regions. Differences of dry/wet characteristics among different seasons are analyzed and the results show that summer is the wettest while spring and winter are drier. Compared with the 1970s’ and 1990s’, the areas of “semidry” region in the 1960s’ and 1980s’ are relatively larger. The areas of “semiwet” and “semiwet and semidry” in the 1980s are the largest compared with those in the other time, which shows that the 1980s was a relative wet period in the Huaihe River valley. The analysis of annual aridity index variation in the Huanghuaihai region shows that there is an increase tendency in the difference between dry and wet regions; i.e., the dry region is becoming drier while the “semiwet and semidry” region, as well as “semiwet” region, is becoming wetter.
The aridity index is calculated and the dryness/wetness characteristics are analyzed based on the daily meteorological data of 104 stations from 1961 to 2006 in the Huanghuaihai region. The Huanghuaihai region is divided into five dry/wet climatic types: wet, semiwet, semiwet and semidry, semidry and semiwet, and semidry regions. The “semidry” region has the largest area compared with the other regions. There is obvious latitudinal distribution in the five climatic regions. Differences of dry/wet characteristics among different seasons are analyzed and the results show that summer is the wettest while spring and winter are drier. Compared with the 1970s’ and 1990s’, the areas of “semidry” region in the 1960s’ and 1980s’ are relatively larger. The areas of “semiwet” and “semiwet and semidry” in the 1980s are the largest compared with those in the other time, which shows that the 1980s was a relative wet period in the Huaihe River valley. The analysis of annual aridity index variation in the Huanghuaihai region shows that there is an increase tendency in the difference between dry and wet regions; i.e., the dry region is becoming drier while the “semiwet and semidry” region, as well as “semiwet” region, is becoming wetter.
2008, 36(5):606-608.
Abstract:
The drought monitoring model at seedling stage under the condition of lowcoverage vegetation is established based on NDVI with MODIS and soil moisture data. The model combines soil adjusted vegetation index (SAVI) with temperature condition index (TCI) on the basis of the correlation analysis of observed soil moisture and relative humidity. Comparison between thermal inertia method and SAVITCI method based on vegetation supply water index method is conducted. The results indicate that the SAVITCI method is better in monitoring largearea crops at seedling stage in Liaoning Province
The drought monitoring model at seedling stage under the condition of lowcoverage vegetation is established based on NDVI with MODIS and soil moisture data. The model combines soil adjusted vegetation index (SAVI) with temperature condition index (TCI) on the basis of the correlation analysis of observed soil moisture and relative humidity. Comparison between thermal inertia method and SAVITCI method based on vegetation supply water index method is conducted. The results indicate that the SAVITCI method is better in monitoring largearea crops at seedling stage in Liaoning Province
2008, 36(5):609-611.
Abstract:
The statistical characteristics and variation of climatic elements are analyzed on the basis of the meteorological observation data corresponding to the relevant periods of winter wheat growth from 1954 to 2007 in the southwestern Shandong Province, and the impacts of climate warming on the seeding time and overwintering period of winter wheat are studied with the correlative analysis method. The results show that compared with the period before 1980, the average air temperature at the seeding time of winter wheat increased by about 0.5 ℃, and the prewinter accumulated temperature increased by 17.8 ℃. The average air temperature in the overwintering period of winter wheat increased by 1.0 ℃. Owing to the combined impact of climate warming and variety renovation, the appropriate seeding time for winter wheat advanced 7 days or so compared to that before 1980. The findings provide references for ascertaining the appropriate seeding time, decreasing freezing damage, and growing strong seedlings of winter wheat.
The statistical characteristics and variation of climatic elements are analyzed on the basis of the meteorological observation data corresponding to the relevant periods of winter wheat growth from 1954 to 2007 in the southwestern Shandong Province, and the impacts of climate warming on the seeding time and overwintering period of winter wheat are studied with the correlative analysis method. The results show that compared with the period before 1980, the average air temperature at the seeding time of winter wheat increased by about 0.5 ℃, and the prewinter accumulated temperature increased by 17.8 ℃. The average air temperature in the overwintering period of winter wheat increased by 1.0 ℃. Owing to the combined impact of climate warming and variety renovation, the appropriate seeding time for winter wheat advanced 7 days or so compared to that before 1980. The findings provide references for ascertaining the appropriate seeding time, decreasing freezing damage, and growing strong seedlings of winter wheat.
2008, 36(5):612-621.
Abstract:
The effectiveness evaluation of precipitation enhancement is made of 12 aircraft cloud seeding operations over the central Hebai Province by means of such evaluation methods as the double contrast based on regional rainfall tendencies, the correlative regression analysis based on regional rainfall tendencies, the covariable multiple regression analysis based on regional rainfall tendencies, the floating control historical regression method, the ClusterAnalysis〖CD*2〗based Floating Control historical regression Method (CAFCM) using rainfall as a covariant, and the CAFCM using rainfall and atmospheric precipitable water as covariants, all of which show greater than 15% or higher relative enhancement of rainfall. The comparison between CAFCM and the other evaluation methods indicates that the CAFCM using rainfall and atmospheric precipitable water as covariants is better than the others, because it adopts cluster analysis, which improves greatly the rainfall correlativity between control and target areas, and increases the accuracy of natural rainfall estimations over the cloud seeding areas by using atmospheric precipitable water as a covariant.
The effectiveness evaluation of precipitation enhancement is made of 12 aircraft cloud seeding operations over the central Hebai Province by means of such evaluation methods as the double contrast based on regional rainfall tendencies, the correlative regression analysis based on regional rainfall tendencies, the covariable multiple regression analysis based on regional rainfall tendencies, the floating control historical regression method, the ClusterAnalysis〖CD*2〗based Floating Control historical regression Method (CAFCM) using rainfall as a covariant, and the CAFCM using rainfall and atmospheric precipitable water as covariants, all of which show greater than 15% or higher relative enhancement of rainfall. The comparison between CAFCM and the other evaluation methods indicates that the CAFCM using rainfall and atmospheric precipitable water as covariants is better than the others, because it adopts cluster analysis, which improves greatly the rainfall correlativity between control and target areas, and increases the accuracy of natural rainfall estimations over the cloud seeding areas by using atmospheric precipitable water as a covariant.
2008, 36(5):622-626.
Abstract:
An analysis is made of the characteristics of the oceanographic and weather backgrounds in winter on North Pacific Ocean, based on the fundamental principles of ship weatherocean routing and the factors influencing the routing design. It is pointed out that the routing design should consider climatic condition, marine condition and weather patterns, as well as short/midrange weather forecasts. Through making full use of favorable weather and marine conditions, such as winds，sea waves and sea currents, ships can not only avoid adverse weather (strong winds, high waves, etc.) to ensure navigation safety, but also save navigation time and costs.
An analysis is made of the characteristics of the oceanographic and weather backgrounds in winter on North Pacific Ocean, based on the fundamental principles of ship weatherocean routing and the factors influencing the routing design. It is pointed out that the routing design should consider climatic condition, marine condition and weather patterns, as well as short/midrange weather forecasts. Through making full use of favorable weather and marine conditions, such as winds，sea waves and sea currents, ships can not only avoid adverse weather (strong winds, high waves, etc.) to ensure navigation safety, but also save navigation time and costs.
2008, 36(5):627-630.
Abstract:
Through the precipitation simulation experiments using MM5V3 with various parameters for the lowlatitude plateau area, the operational system of the MM5 mesoscale numerical prediction model is established based on the SGI O350 minicomputer. Its precipitation prediction has a time resolution of less than 60 minutes and a horizontal resolution of less than 10 km. By integrating the radar, retrieved satellite data, conventional meteorological data, and intensive rainfall observation data with the weighting method, a refined rainfall field was generated. Based on the relation between weather background and Landslide/debrisflow disasters, the refined weatherbased monitoring and warning system of debris flow disasters for Yunnan Province is established with the PPES model, which has a time resolution of 12 hours and a horizontal resolution of 30 km, and can provide the weatherbased graded prediction products of Landslide/debrisflow disasters
Through the precipitation simulation experiments using MM5V3 with various parameters for the lowlatitude plateau area, the operational system of the MM5 mesoscale numerical prediction model is established based on the SGI O350 minicomputer. Its precipitation prediction has a time resolution of less than 60 minutes and a horizontal resolution of less than 10 km. By integrating the radar, retrieved satellite data, conventional meteorological data, and intensive rainfall observation data with the weighting method, a refined rainfall field was generated. Based on the relation between weather background and Landslide/debrisflow disasters, the refined weatherbased monitoring and warning system of debris flow disasters for Yunnan Province is established with the PPES model, which has a time resolution of 12 hours and a horizontal resolution of 30 km, and can provide the weatherbased graded prediction products of Landslide/debrisflow disasters
2008, 36(5):631-633.
Abstract:
By using Doppler weather radar radial velocity and the echo intensity, a heavy snowfall happened on 2 to 5 March 2007 in Hebei Province is analyzed. The results indicate that the characteristics are obvious at the different stages of rainfall development (formation, development, and dissipation). The lowerlevel convergence, warm advection, and “bull’s eyes”shaped structure on the velocity chart indicate severe snowfall, and the gradual disappearing of warm advection from low to high indicates the weakening of precipitation. If there is an echo center of over 30 dBz lasted for certain time, severe snowfall will happen possibly. Precipitation enhancement should be conducted at the enhancing stage of snowfall. The elevation of the rocket may refer to the height of the zerodegree layer.
By using Doppler weather radar radial velocity and the echo intensity, a heavy snowfall happened on 2 to 5 March 2007 in Hebei Province is analyzed. The results indicate that the characteristics are obvious at the different stages of rainfall development (formation, development, and dissipation). The lowerlevel convergence, warm advection, and “bull’s eyes”shaped structure on the velocity chart indicate severe snowfall, and the gradual disappearing of warm advection from low to high indicates the weakening of precipitation. If there is an echo center of over 30 dBz lasted for certain time, severe snowfall will happen possibly. Precipitation enhancement should be conducted at the enhancing stage of snowfall. The elevation of the rocket may refer to the height of the zerodegree layer.
2008, 36(5):634-638.
Abstract:
A primary description is made of the process of establishing the FY2D OLR inverse model, and the model comparison is conducted between NOAA and FY2D. The earthatmosphere infrared radiation transfer equation is introduced. The radiances and OLR at the top of atmosphere for 3812 sounding profiles, the channel radiance for FY2D window channel 1, 2 and water vapor channel, and the narrowband radiative flux of three FY2D channels for 3812 soundings are calculated, and the limbdarken correction equations for the 3 channel radiances are established. The FY2D OLR inverse model is devised based on the narrowband flux and OLR scattering graphs for 3812 soundings. By comparing the NOAA17 AVHRR channel 5 OLR inverse model with the FY2D window channel 2 OLR inverse model, it is concluded that the two satellites OLR inverse models are nearly the same. An example of the FY2D OLR product and the product quality examination is also given.
A primary description is made of the process of establishing the FY2D OLR inverse model, and the model comparison is conducted between NOAA and FY2D. The earthatmosphere infrared radiation transfer equation is introduced. The radiances and OLR at the top of atmosphere for 3812 sounding profiles, the channel radiance for FY2D window channel 1, 2 and water vapor channel, and the narrowband radiative flux of three FY2D channels for 3812 soundings are calculated, and the limbdarken correction equations for the 3 channel radiances are established. The FY2D OLR inverse model is devised based on the narrowband flux and OLR scattering graphs for 3812 soundings. By comparing the NOAA17 AVHRR channel 5 OLR inverse model with the FY2D window channel 2 OLR inverse model, it is concluded that the two satellites OLR inverse models are nearly the same. An example of the FY2D OLR product and the product quality examination is also given.
26 METOPonBoard SuperHigh Spectrum Resolution Infrared Atmospheric Sounding Interferometer (IASI)
2008, 36(5):639-642.
Abstract:
An introduction is made to the development background, instrument characteristics, development technology, and data product processing of satellite infrared atmospheric sounding interferometers, as well as the comparison with AIRS (Atmospheric Infrared Sounder), taking the superhigh spectrum sounding instrument IASI (Infrared Atmospheric Sounding Interferometer) loaded in the European METOP satellite as an example, to thoroughly understand the new characteristics of satellite infrared atmospheric sounding instruments. IASI based on the Michelson interferometer provides abundant information for atmospheric remote sensing, which can be used to retrieve the atmosphere, ocean, clouds, and atmosphere components. In addition, IASI can provide important references for highspectrum infrared vertical atmospheric sounding instruments that will be loaded in Chinese FY satellites.
An introduction is made to the development background, instrument characteristics, development technology, and data product processing of satellite infrared atmospheric sounding interferometers, as well as the comparison with AIRS (Atmospheric Infrared Sounder), taking the superhigh spectrum sounding instrument IASI (Infrared Atmospheric Sounding Interferometer) loaded in the European METOP satellite as an example, to thoroughly understand the new characteristics of satellite infrared atmospheric sounding instruments. IASI based on the Michelson interferometer provides abundant information for atmospheric remote sensing, which can be used to retrieve the atmosphere, ocean, clouds, and atmosphere components. In addition, IASI can provide important references for highspectrum infrared vertical atmospheric sounding instruments that will be loaded in Chinese FY satellites.
2008, 36(5):643-646.
Abstract:
It is found out from practice that the traditional method for measuring the horizontality of the antenna pedestals of CINRAD/SC weather radar is difficult to use at a common radar station, and the measurements contain obvious errors. The steps to improve, in combination with the revision and processing of the data to be checked, are presented. With the method, the checking process can be shortened and simplified obviously. The outcomes after treating with mathematical methods are more close to the true values. The method can also be used for other types of weather radars.
It is found out from practice that the traditional method for measuring the horizontality of the antenna pedestals of CINRAD/SC weather radar is difficult to use at a common radar station, and the measurements contain obvious errors. The steps to improve, in combination with the revision and processing of the data to be checked, are presented. With the method, the checking process can be shortened and simplified obviously. The outcomes after treating with mathematical methods are more close to the true values. The method can also be used for other types of weather radars.
2008, 36(5):647-652.
Abstract:
The realtime characteristics of vertical profiles of radar reflectivity during four weather processes from 2004 to 2007 are analyzed on the basis of the volume scan data from the Doppler radar at Shijiazhuang and the nearly simultaneous 10minute precipitation measurements from rain gauges, and meaningful results are gained. There were obvious bright bands on the zerotemperature layer in stratiform clouds or merging cloud echoes, but there was no bright band in shorttime rainstorms. Radar reflectivity vertical profiles varied greatly during a hailing process: before hailing with the maximum reflectivity at middle or upper levels, while hailing with the height of maximum reflectivity descending, and after hailing with the maximum reflectivity weakening. During snowing, bright bands of zerotemperature layer were not clear. In the mountain area west of Shijiazhuang, the precipitation and echo intensity in stratiform clouds or merging clouds are usually overestimated because of the impacts of the bright bands on the zerotemperature layer. Compared with the lowest elevation method, the estimated precipitation by using the vertical profile method is more accurate for shorttime heavy rainfall, and shows improvement for homogeneous rainfall. It is a useful and easy method for convective weather forecasting in the areas with large shield angles or without rain gauges
The realtime characteristics of vertical profiles of radar reflectivity during four weather processes from 2004 to 2007 are analyzed on the basis of the volume scan data from the Doppler radar at Shijiazhuang and the nearly simultaneous 10minute precipitation measurements from rain gauges, and meaningful results are gained. There were obvious bright bands on the zerotemperature layer in stratiform clouds or merging cloud echoes, but there was no bright band in shorttime rainstorms. Radar reflectivity vertical profiles varied greatly during a hailing process: before hailing with the maximum reflectivity at middle or upper levels, while hailing with the height of maximum reflectivity descending, and after hailing with the maximum reflectivity weakening. During snowing, bright bands of zerotemperature layer were not clear. In the mountain area west of Shijiazhuang, the precipitation and echo intensity in stratiform clouds or merging clouds are usually overestimated because of the impacts of the bright bands on the zerotemperature layer. Compared with the lowest elevation method, the estimated precipitation by using the vertical profile method is more accurate for shorttime heavy rainfall, and shows improvement for homogeneous rainfall. It is a useful and easy method for convective weather forecasting in the areas with large shield angles or without rain gauges
2008, 36(5):653-657.
Abstract:
The phenomenon and the characteristics of a comprehensive failure of CINRAD/SB radar at Changde are described. The causal analysis of failure indicates that the diagnosis and maintenance of weather radar need to be conducted in a comprehensive manner, such as using indicator lamp, breakdown alert, and radar performance data, as well as combining software with hardware methods. Meanwhile the understanding of the three calibration principles and their signal flows relevant to breakdowns can help analyze, isolate, and locate breakdowns more effectively and accurately.
The phenomenon and the characteristics of a comprehensive failure of CINRAD/SB radar at Changde are described. The causal analysis of failure indicates that the diagnosis and maintenance of weather radar need to be conducted in a comprehensive manner, such as using indicator lamp, breakdown alert, and radar performance data, as well as combining software with hardware methods. Meanwhile the understanding of the three calibration principles and their signal flows relevant to breakdowns can help analyze, isolate, and locate breakdowns more effectively and accurately.
2008, 36(5):658-660.
Abstract:
The calibration errors are analyzed in the aspects of radar parameter measurement,A/D transformation, video integration processing, precision and stability of measuring instruments, etc, through demonstrating the principles and method of CTL713C digital weather radar echo intensity calibration, and the possible error corresponding to each case is given, respectively. The possible calibration errors in echo intensity resulted from the measuring environment and manual operations are discussed, and the method for examining the accuracy of calibration results of radar echo intensity is described. The key issues in radar echo intensity calibration are summarized.
The calibration errors are analyzed in the aspects of radar parameter measurement,A/D transformation, video integration processing, precision and stability of measuring instruments, etc, through demonstrating the principles and method of CTL713C digital weather radar echo intensity calibration, and the possible error corresponding to each case is given, respectively. The possible calibration errors in echo intensity resulted from the measuring environment and manual operations are discussed, and the method for examining the accuracy of calibration results of radar echo intensity is described. The key issues in radar echo intensity calibration are summarized.
2008, 36(5):661-665.
Abstract:
By means of SNHT (Standard Normal Homogeneity Test) method, a statistical test is conducted on the mean annual wind velocity series of 36 weather stations from 1971 to 2004 in Zhejiang Province. It is found that interruptions existed in 23 stations of 36 samples, in which the heterogeneity in 13 stations is due to their relocation (at a proportion of 57%), in 5 stations due to the environment variation (22%), in one station due to the change of its wind observation equipment, another due to its observation regulation change (about 4%), and the reasons for interruptions in 3 stations are nor clear (13%). The relocation of stations is the main cause of heterogeneity in wind velocity data.
By means of SNHT (Standard Normal Homogeneity Test) method, a statistical test is conducted on the mean annual wind velocity series of 36 weather stations from 1971 to 2004 in Zhejiang Province. It is found that interruptions existed in 23 stations of 36 samples, in which the heterogeneity in 13 stations is due to their relocation (at a proportion of 57%), in 5 stations due to the environment variation (22%), in one station due to the change of its wind observation equipment, another due to its observation regulation change (about 4%), and the reasons for interruptions in 3 stations are nor clear (13%). The relocation of stations is the main cause of heterogeneity in wind velocity data.
2008, 36(5):666-669.
Abstract:
The comparison and analysis are conducted by means of AWS (Automatic Weather Station) and manually observed pressure data from six stations in Gansu, so to identify the change resulted from the renewal of observation instruments and assess objectively the continuity and accuracy of observation data. The results indicate that AWS and manual records are very close in annual and monthly averages; the probability distributions of errors in regular, average, maximum, and minimum records are basically identical and relatively concentrated. The statistical test indicates that there is no significant differences in regular, maximum, minimum, 24record mean, and 4record mean measurements; there is obvious daily variation in regular records with the greater errors in 09:00〖CD*2〗10:00 and 19:00〖CD*2〗22:00 and smaller in 12:00〖CD*2〗15:00 and 01:00〖CD*2〗05:00; and there exist obvious differences among the six stations, in one or two of which there are manifest systematic errors due to the properties of observation instruments.
The comparison and analysis are conducted by means of AWS (Automatic Weather Station) and manually observed pressure data from six stations in Gansu, so to identify the change resulted from the renewal of observation instruments and assess objectively the continuity and accuracy of observation data. The results indicate that AWS and manual records are very close in annual and monthly averages; the probability distributions of errors in regular, average, maximum, and minimum records are basically identical and relatively concentrated. The statistical test indicates that there is no significant differences in regular, maximum, minimum, 24record mean, and 4record mean measurements; there is obvious daily variation in regular records with the greater errors in 09:00〖CD*2〗10:00 and 19:00〖CD*2〗22:00 and smaller in 12:00〖CD*2〗15:00 and 01:00〖CD*2〗05:00; and there exist obvious differences among the six stations, in one or two of which there are manifest systematic errors due to the properties of observation instruments.
2008, 36(5):670-672.
Abstract:
The design of isopleth drawing and analyzing software based on VB for TV weather forecasting under the Windows environment is described. By using a modularized scheme, it has a succinct interface and is convenient to operate. The isopleth drawing of rectangular grids and the principles and techniques of adjusting isopleth control points are described in detail. The animated script files of isopleth drawing are generated with the fourth kind of grids from MICAPS data, and the process of weather development is displayed on the platform Weather 3D. The practice proved that the software runs stably and has good applicability and translatability.
The design of isopleth drawing and analyzing software based on VB for TV weather forecasting under the Windows environment is described. By using a modularized scheme, it has a succinct interface and is convenient to operate. The isopleth drawing of rectangular grids and the principles and techniques of adjusting isopleth control points are described in detail. The animated script files of isopleth drawing are generated with the fourth kind of grids from MICAPS data, and the process of weather development is displayed on the platform Weather 3D. The practice proved that the software runs stably and has good applicability and translatability.
2008, 36(5):673-675.
Abstract:
2008, 36(5):676-678.
Abstract:
External LinksChina Meteorological AdministrationCMA Meteorological Observation CentreChinese Academy of Meteorological SciencesBeijing Meteorological ServiceNational Satellite Meteorological Center
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.