Volume 35,Issue 1,2007 Table of Contents
2007, 35(1):1-8.
Abstract:
The major advances in the researches on the influences of the snow cover over the Tibetan Plateau on weather and climate are summarized. It is recognized that more snow will lead to weaker or later Asian summer monsoon, which is realized through snowmonsoon interaction. As for the relative significance of albedo and melted snow water, there is no, by now, consistent opinion. As an important landsurface forcing factor, snow cover has close relation with the factors of subtropic high, blocking, winter and summer monsoons, ENSO, sea surface temperature, etc. It has great significance that the snow cover over the Tibetan Plateau increases on the background of global warming. Studies on the interdecadal variations of snow over Tibetan Plateau will help understand the causes of the fact “flooding in South China and drought in North China", and also contribute to the improvement of precipitation forecast.
The major advances in the researches on the influences of the snow cover over the Tibetan Plateau on weather and climate are summarized. It is recognized that more snow will lead to weaker or later Asian summer monsoon, which is realized through snowmonsoon interaction. As for the relative significance of albedo and melted snow water, there is no, by now, consistent opinion. As an important landsurface forcing factor, snow cover has close relation with the factors of subtropic high, blocking, winter and summer monsoons, ENSO, sea surface temperature, etc. It has great significance that the snow cover over the Tibetan Plateau increases on the background of global warming. Studies on the interdecadal variations of snow over Tibetan Plateau will help understand the causes of the fact “flooding in South China and drought in North China", and also contribute to the improvement of precipitation forecast.
2007, 35(1):9-14.
Abstract:
The microphysical parameters of clouds, including the phase, droplet size distribution (DSD) and liquid water content (LWC), play important roles in climate change, radiation budget, weather modification, aviation safety, etc. The groundbased sounding technologies and the retrieval algorithms of hydrometeor phase, DSD and LWC in the cloud microphysical researches are summarized, and their prospects are discussed.
The microphysical parameters of clouds, including the phase, droplet size distribution (DSD) and liquid water content (LWC), play important roles in climate change, radiation budget, weather modification, aviation safety, etc. The groundbased sounding technologies and the retrieval algorithms of hydrometeor phase, DSD and LWC in the cloud microphysical researches are summarized, and their prospects are discussed.
2007, 35(1):15-19.
Abstract:
The weather and climate comply with the fluid dynamical equation and appear stochastic. In order to explore the relationship between weather and climate, the fractional derivative and integration are introduced. Physically, the stochastic degrees of weather and climate are different. It is proposed that the qth (0≤q≤1) derivative of climate is weather. When q = 1, it is the Hass elmann's result. The analysis based on observation data shows that climate anomaly has longer range correlation and better memory than weather. The probability density function of climate has a long tail, which can reflect the probability of extreme weather and climate.
The weather and climate comply with the fluid dynamical equation and appear stochastic. In order to explore the relationship between weather and climate, the fractional derivative and integration are introduced. Physically, the stochastic degrees of weather and climate are different. It is proposed that the qth (0≤q≤1) derivative of climate is weather. When q = 1, it is the Hass elmann's result. The analysis based on observation data shows that climate anomaly has longer range correlation and better memory than weather. The probability density function of climate has a long tail, which can reflect the probability of extreme weather and climate.
2007, 35(1):20-25.
Abstract:
The largescale strong convective storm and the local hail storms over Ningxia, Inner Mongolia, Shaanxi, Shanxi and Henan on 15 and 16 June 2004 are analyzed by using the potential vorticity method. The spatial structure of dry potential vorticity (PV) exhibits that the positive largevalue potential vorticity center inclined to west from upstream to storm zone; the positive potential vorticity center in the upper troposphere and the dense PV isoline zone with enhanced PV gradients in the lower/middle troposphere were overlapped in the storm area. The dry PV field in the lower troposphere shows that the coupling of the dense PV isoline zone and the wind shear was formed in the storm area. The wet potential vorticity field in the lower troposphere shows that the coupling of convective unstable tongue and the wet baroclinicty center and the dense isotimic area of MPV2 was formed in the storm area. Before the storm, the dense meridional PV isolines was formed over Hetao in 500 hPa, and the positive PV disturbance and the positive PV advection toward Hetao appeared at the same time in the strong north flow over the Mongolia area in 500 hPa, which is highly indicative for the occurrence of largescale strong convective storms on the Loess Plateau.
The largescale strong convective storm and the local hail storms over Ningxia, Inner Mongolia, Shaanxi, Shanxi and Henan on 15 and 16 June 2004 are analyzed by using the potential vorticity method. The spatial structure of dry potential vorticity (PV) exhibits that the positive largevalue potential vorticity center inclined to west from upstream to storm zone; the positive potential vorticity center in the upper troposphere and the dense PV isoline zone with enhanced PV gradients in the lower/middle troposphere were overlapped in the storm area. The dry PV field in the lower troposphere shows that the coupling of the dense PV isoline zone and the wind shear was formed in the storm area. The wet potential vorticity field in the lower troposphere shows that the coupling of convective unstable tongue and the wet baroclinicty center and the dense isotimic area of MPV2 was formed in the storm area. Before the storm, the dense meridional PV isolines was formed over Hetao in 500 hPa, and the positive PV disturbance and the positive PV advection toward Hetao appeared at the same time in the strong north flow over the Mongolia area in 500 hPa, which is highly indicative for the occurrence of largescale strong convective storms on the Loess Plateau.
2007, 35(1):26-30.
Abstract:
The characteristics of drought years are analyzed and the rainfall anomalies of the next 10 years are predicted on the basis of the rainfall data of 15 stations in South China from 1951 (1961) to 2003. The critical annualrainfall amount of each station is calculated by means of the range analysis method, and the assessment is made of severe and common drought years. The results show that the variation of annual rainfall in South China is highly periodic: common droughts occur once every 4.3 years and severe droughts every 14.3 years from 1961 to 2003. Some drought/flood forecasting methods are introduced, such as exponential function method, multiperiod characteristicvalue superposition method, nonlinear integrated climate forecasting method, and optimal teleconnection analysis method. The ensemble prediction for the next 10 years in South China is: the rainfall will be more than the normal in 2005, less than the normal from 2006 to 2008, and more than the normal again from 2009 to 2012.
The characteristics of drought years are analyzed and the rainfall anomalies of the next 10 years are predicted on the basis of the rainfall data of 15 stations in South China from 1951 (1961) to 2003. The critical annualrainfall amount of each station is calculated by means of the range analysis method, and the assessment is made of severe and common drought years. The results show that the variation of annual rainfall in South China is highly periodic: common droughts occur once every 4.3 years and severe droughts every 14.3 years from 1961 to 2003. Some drought/flood forecasting methods are introduced, such as exponential function method, multiperiod characteristicvalue superposition method, nonlinear integrated climate forecasting method, and optimal teleconnection analysis method. The ensemble prediction for the next 10 years in South China is: the rainfall will be more than the normal in 2005, less than the normal from 2006 to 2008, and more than the normal again from 2009 to 2012.
6 Characteristics of Maximum Temperature and High Temperature Days in Hebei Province in Past 50 years
2007, 35(1):31-35.
Abstract:
The interannual and interdecadal changes of maximum temperature and the number of high temperature days in Hebei Province and the regional differences of the changes are analyzed with the observational data in recent 50 years in Hebei. The results indicate that the average maximum temperatures in all parts and the whole province showed an increasing trend; the increasing rate of annual maximum temperature had a range of 0.5 to 1.0 ℃ in most parts of the province, but their warming rates are different. The maximum temperature in winter is the greatest and that in autumn is the smallest. The numbers of days with maximum temperature above 30 ℃ have been increasing from the 1960s to the 1990s for 70% stations. The most rapid warming occurred in the 1980s and 1990s, while the most obvious warming occurred in the eastern plain. The interdecadal change of the number of days with maximum temperature above 35 ℃ was slight, and the interannual change decreased at first and then increased and was smaller.
The interannual and interdecadal changes of maximum temperature and the number of high temperature days in Hebei Province and the regional differences of the changes are analyzed with the observational data in recent 50 years in Hebei. The results indicate that the average maximum temperatures in all parts and the whole province showed an increasing trend; the increasing rate of annual maximum temperature had a range of 0.5 to 1.0 ℃ in most parts of the province, but their warming rates are different. The maximum temperature in winter is the greatest and that in autumn is the smallest. The numbers of days with maximum temperature above 30 ℃ have been increasing from the 1960s to the 1990s for 70% stations. The most rapid warming occurred in the 1980s and 1990s, while the most obvious warming occurred in the eastern plain. The interdecadal change of the number of days with maximum temperature above 35 ℃ was slight, and the interannual change decreased at first and then increased and was smaller.
7 Characteristics of Tropical Cyclones Landed in Guangdong and Its Relationship with Subtropical High
2007, 35(1):36-39.
Abstract:
The number of tropical cyclones (TCs) landed in Guangdong in 2004 is less than those of normal years, and there were no tropical cyclone landed in the western Guangdong. The first landing day is later, and the last landing day is earlier than normal. The intensities of these tropical cyclones are weaker on the whole, so that their benefits is greater than damage for Guangdong Province. The characteristics of the tropical cyclones landed in Guangdong in July, August and September during 1951-2004 are analyzed, and the result shows that the number of landing TCs is related to the position and intensity of the Northwest Pacific subtropical high. Three favorable and three unfavorable circulation patterns of the subtropical high for TC landing are identified.
The number of tropical cyclones (TCs) landed in Guangdong in 2004 is less than those of normal years, and there were no tropical cyclone landed in the western Guangdong. The first landing day is later, and the last landing day is earlier than normal. The intensities of these tropical cyclones are weaker on the whole, so that their benefits is greater than damage for Guangdong Province. The characteristics of the tropical cyclones landed in Guangdong in July, August and September during 1951-2004 are analyzed, and the result shows that the number of landing TCs is related to the position and intensity of the Northwest Pacific subtropical high. Three favorable and three unfavorable circulation patterns of the subtropical high for TC landing are identified.
2007, 35(1):40-44.
Abstract:
There are 35 landfalling tropical cyclones in Zhejiang Province from 1949 to 2004. The average moving velocities and acceleration during 24 hours and 6 hours before landing are calculated. The results show that 60% of landfalling tropical cyclones move faster before landing; 28.4% move at the same speed, and 11.4% move more slowly. Analyzed are the atmospheric circulation, the steering flow, the structure and intensity changes of tropical cyclones before landing, so to find the reason why tropical cyclones move at different velocities before landing. It is found that the moving velocity of a tropical cyclone is closely correlated with the 500 hPa circulation pattern and the steering flow and is also related to the variation of the main inflow path, the mutual rotation of tropical cyclones and moving velocity variation.
There are 35 landfalling tropical cyclones in Zhejiang Province from 1949 to 2004. The average moving velocities and acceleration during 24 hours and 6 hours before landing are calculated. The results show that 60% of landfalling tropical cyclones move faster before landing; 28.4% move at the same speed, and 11.4% move more slowly. Analyzed are the atmospheric circulation, the steering flow, the structure and intensity changes of tropical cyclones before landing, so to find the reason why tropical cyclones move at different velocities before landing. It is found that the moving velocity of a tropical cyclone is closely correlated with the 500 hPa circulation pattern and the steering flow and is also related to the variation of the main inflow path, the mutual rotation of tropical cyclones and moving velocity variation.
2007, 35(1):45-48.
Abstract:
The climate changes and their characteristics over the northern Shaanxi plateau in recent 42 years are comprehensively analyzed on the basis of the data of mean air temperature, precipitation, relative humidity and wind speed of 16 stations from 1961 to 2002. The results show that the precipitation in recent 42 years decreased by －25.31 mm per 10 years, especially in autumn. The tempera ture increased by 0.26 ℃ per 10 years, and it was remarkably higher in winter. It was relatively cold and wet in the 1980s, and became worm and dry from the 1990s.
The climate changes and their characteristics over the northern Shaanxi plateau in recent 42 years are comprehensively analyzed on the basis of the data of mean air temperature, precipitation, relative humidity and wind speed of 16 stations from 1961 to 2002. The results show that the precipitation in recent 42 years decreased by －25.31 mm per 10 years, especially in autumn. The tempera ture increased by 0.26 ℃ per 10 years, and it was remarkably higher in winter. It was relatively cold and wet in the 1980s, and became worm and dry from the 1990s.
2007, 35(1):49-52.
Abstract:
An analysis is made statistically of the EastAsia monsoon intensity change regularities from 1951 to 2004, as well as the relation of EastAsian winter/summer monsoon intensity changes to winter temperature and summer precipitation in Hebei Province. The results indicate that during the stage of strong winter monsoon, the winter temperature of Hebei Province is somewhat lower than the normal, and vice versa. There is correlation between summer monsoon intensity and summer precipitation. In the years of strong summer monsoon, the summer precipitation tends to increase, and vice versa. The intensity of the summer monsoon has a relation with the arriving time of summer monsoon. When the summer monsoon comes early, the intensity of summer monsoon is strong, and vice versa.
An analysis is made statistically of the EastAsia monsoon intensity change regularities from 1951 to 2004, as well as the relation of EastAsian winter/summer monsoon intensity changes to winter temperature and summer precipitation in Hebei Province. The results indicate that during the stage of strong winter monsoon, the winter temperature of Hebei Province is somewhat lower than the normal, and vice versa. There is correlation between summer monsoon intensity and summer precipitation. In the years of strong summer monsoon, the summer precipitation tends to increase, and vice versa. The intensity of the summer monsoon has a relation with the arriving time of summer monsoon. When the summer monsoon comes early, the intensity of summer monsoon is strong, and vice versa.
2007, 35(1):53-56.
Abstract:
The influence of hail events on Tibet animal husbandry and agriculture is very serious, only next to that of frost and drought disasters. With the 30 year hail disaster data from meteorological stations over Tibetan plateau, the temporalspatial distribution characteristics of hail events are analyzed. The results show that hail events were concentrated mainly around the north and south parts of the Tibet; there was obvious seasonal variation; the diameters of hailstones were small; the duration of hail events was short; the hail damage was severer in the central Tibetan Plateau than in the agricultural region. According to the hazard index based on the size of hailstones and the duration of hail events, as well as vegetation type, the hazard regionlization of hail events in the Tibetan Plateau is conducted.
The influence of hail events on Tibet animal husbandry and agriculture is very serious, only next to that of frost and drought disasters. With the 30 year hail disaster data from meteorological stations over Tibetan plateau, the temporalspatial distribution characteristics of hail events are analyzed. The results show that hail events were concentrated mainly around the north and south parts of the Tibet; there was obvious seasonal variation; the diameters of hailstones were small; the duration of hail events was short; the hail damage was severer in the central Tibetan Plateau than in the agricultural region. According to the hazard index based on the size of hailstones and the duration of hail events, as well as vegetation type, the hazard regionlization of hail events in the Tibetan Plateau is conducted.
2007, 35(1):57-60.
Abstract:
An analysis is made of the temporalspatial distribution, seasonal variation and tendency of various tropopauses by means of statistical methods, and the distribution features of the tropopauses and the variation regularities of height and temperature are revealed, based on the upperair sounding data of seven stations from 1970 to 2001 over Qinghai Province. The results indicate that various tropopauses have different occurrence frequencies at different stations; the polar and tropic type tropopauses differ not only in heights, but also in seasonal variation; the highest tropopause corresponds to low temperature and the lowest corresponds to high temperature. The annual mean height (temperature) of tropic type tropopauses shows an increasing (decreasing) tendency. These are related with the decreasing of stratospheric ozone and temperature, as well as the rising of the troposphere in recent years.
An analysis is made of the temporalspatial distribution, seasonal variation and tendency of various tropopauses by means of statistical methods, and the distribution features of the tropopauses and the variation regularities of height and temperature are revealed, based on the upperair sounding data of seven stations from 1970 to 2001 over Qinghai Province. The results indicate that various tropopauses have different occurrence frequencies at different stations; the polar and tropic type tropopauses differ not only in heights, but also in seasonal variation; the highest tropopause corresponds to low temperature and the lowest corresponds to high temperature. The annual mean height (temperature) of tropic type tropopauses shows an increasing (decreasing) tendency. These are related with the decreasing of stratospheric ozone and temperature, as well as the rising of the troposphere in recent years.
2007, 35(1):61-65.
Abstract:
The evolutionary features of the whole tropospheric precipitable water, the intensity of vertical ascending motion in the lower layers over Hangzhou, and the surface precipitation in Hangzhou are analyzed by the NCEP/NCAR reanalysis grid data of humidity and vertical velocity, as well as the stationary data of precipitation in Hangzhou, from January 1951 to November 2003. The results show that there is significant interannual variation both in precipitable water and vertical ascending motion, and even though both precipitable water and vertical ascending motion are favorable, the precipitation would not certainly greater than normal, which means that atmospheric water resources have great potential. The longterm variation features of atmospheric precipitable water in June over Hangzhou are compared with those of other places at the same latitude over the world, and the results show that the precipitable water in the troposphere in June over Hangzhou and the other cities at the same latitude had a decreasing trend in the past 53 years.
The evolutionary features of the whole tropospheric precipitable water, the intensity of vertical ascending motion in the lower layers over Hangzhou, and the surface precipitation in Hangzhou are analyzed by the NCEP/NCAR reanalysis grid data of humidity and vertical velocity, as well as the stationary data of precipitation in Hangzhou, from January 1951 to November 2003. The results show that there is significant interannual variation both in precipitable water and vertical ascending motion, and even though both precipitable water and vertical ascending motion are favorable, the precipitation would not certainly greater than normal, which means that atmospheric water resources have great potential. The longterm variation features of atmospheric precipitable water in June over Hangzhou are compared with those of other places at the same latitude over the world, and the results show that the precipitable water in the troposphere in June over Hangzhou and the other cities at the same latitude had a decreasing trend in the past 53 years.
2007, 35(1):66-70.
Abstract:
The calculation model of the spatial distribution of water vapor pressure in Chongqing in real terrain is established on the basis of conventional meteorological data. The monthly and the annual mean spatial distributions of water vapor pressure in over Chongqing are calculated and the map drawing and particularly the spatial distribution of water vapor pressure over Chongqing in real terrain are completed. The analysis shows that water vapor pressure decreased with the increasing of sea level elevation; the minimums of water vapor pressure for all months appeared in the northeastern mountainous area; there is distinct seasonal change in water vapor pressure over Chongqing.
The calculation model of the spatial distribution of water vapor pressure in Chongqing in real terrain is established on the basis of conventional meteorological data. The monthly and the annual mean spatial distributions of water vapor pressure in over Chongqing are calculated and the map drawing and particularly the spatial distribution of water vapor pressure over Chongqing in real terrain are completed. The analysis shows that water vapor pressure decreased with the increasing of sea level elevation; the minimums of water vapor pressure for all months appeared in the northeastern mountainous area; there is distinct seasonal change in water vapor pressure over Chongqing.
2007, 35(1):71-76.
Abstract:
The variation of winter temperature in Dalian is analyzed by using the data set of the monthly mean global sea surface temperature (SST), NCEP/NCAR reanalysis data and winter temperature data in Dalian from 1960 to 2000. The possible relations between winter temperature anomalies in Dalian and prophase SST over the Indian Ocean are also studied. It is found that waters within 5°S－5 °N, 60°－75°E are the key areas of sea surface temperature anomaly (SSTA) that affect the winter temperature of these regions from April to July. Through the longterm airsea interactions, the prophase SSTA affected the later general circulation. There are significant differences in the sealevel pressure anomaly (SLPA), height anomaly at 500 hPa and zonal wind anomaly at 300 hPa fields in the warm/cold years in the key areas, especially notably differences in the Siberia high, East Asian trough, polarfront jet and the locations of polar vortices, resulting in winter temperature anomalies in Dalian.
The variation of winter temperature in Dalian is analyzed by using the data set of the monthly mean global sea surface temperature (SST), NCEP/NCAR reanalysis data and winter temperature data in Dalian from 1960 to 2000. The possible relations between winter temperature anomalies in Dalian and prophase SST over the Indian Ocean are also studied. It is found that waters within 5°S－5 °N, 60°－75°E are the key areas of sea surface temperature anomaly (SSTA) that affect the winter temperature of these regions from April to July. Through the longterm airsea interactions, the prophase SSTA affected the later general circulation. There are significant differences in the sealevel pressure anomaly (SLPA), height anomaly at 500 hPa and zonal wind anomaly at 300 hPa fields in the warm/cold years in the key areas, especially notably differences in the Siberia high, East Asian trough, polarfront jet and the locations of polar vortices, resulting in winter temperature anomalies in Dalian.
2007, 35(1):77-81.
Abstract:
The relationship between cloud cover variation and atmospheric circulation is analyzed with the JanuarytoDecember mean cloud cover data of four stations from 1961 to 2000 over the Qilian Mountain area by composite, correlation and spectral analysis methods. The results show that the cloud cover over the Qilian Mountain area is affected by the Western Pacific subtropical high, QinghaiX izang Plateau monsoon, zonal circulation, and solar activities. When the subtropical high area enlarges, moves northwards and intensifies the zonal circulation in midlatitudes, it thus induces the subtropical front to move northwards, decreases the times of the cold and warm air meeting over the Qilian Mountain area, and eventually causes the decreased cloud cover; and vice versa. The stronger (weaker) the plateau monsoon, the more (little) cloud cover over the Qilian Mountain.
The relationship between cloud cover variation and atmospheric circulation is analyzed with the JanuarytoDecember mean cloud cover data of four stations from 1961 to 2000 over the Qilian Mountain area by composite, correlation and spectral analysis methods. The results show that the cloud cover over the Qilian Mountain area is affected by the Western Pacific subtropical high, QinghaiX izang Plateau monsoon, zonal circulation, and solar activities. When the subtropical high area enlarges, moves northwards and intensifies the zonal circulation in midlatitudes, it thus induces the subtropical front to move northwards, decreases the times of the cold and warm air meeting over the Qilian Mountain area, and eventually causes the decreased cloud cover; and vice versa. The stronger (weaker) the plateau monsoon, the more (little) cloud cover over the Qilian Mountain.
2007, 35(1):82-87.
Abstract:
The extraordinary floodinducing rainfall in South China in June 2005 is analyzed synoptically on the basis of the conventional observation data and NCEP/NCAR reanalysis data. The results show that the heavy rainfall, which had two main rain belts and significant daily variations, was mainly associated with the active 500 hPa trough, 850 hPa shear line, lowlevel jet and crossequatorial flows. The westerly fluctuations related to the 500 hPa trough and 850 hPa shear line (tropical systems related to the strong southwesterly and crossequatorial flows) mostly account for the rain belt in the northern (southern) part of Guangdong province. As the activities of the westerly fluctuations decayed, the north rain belt decreased gradually. The southern rain belt had the peak periods of rainfall corresponding to the peak phrases of the meridional winds in the midlow layer over the southern coastal area, which indicates the impacts of the lowlevel jet. The occurring of heavy rainfall was induced by the strong cross equatorial flows, which provide sufficient water vapor for South China, and the end of heavy rainfall is featured by the buildup of the upperlevel easterly.
The extraordinary floodinducing rainfall in South China in June 2005 is analyzed synoptically on the basis of the conventional observation data and NCEP/NCAR reanalysis data. The results show that the heavy rainfall, which had two main rain belts and significant daily variations, was mainly associated with the active 500 hPa trough, 850 hPa shear line, lowlevel jet and crossequatorial flows. The westerly fluctuations related to the 500 hPa trough and 850 hPa shear line (tropical systems related to the strong southwesterly and crossequatorial flows) mostly account for the rain belt in the northern (southern) part of Guangdong province. As the activities of the westerly fluctuations decayed, the north rain belt decreased gradually. The southern rain belt had the peak periods of rainfall corresponding to the peak phrases of the meridional winds in the midlow layer over the southern coastal area, which indicates the impacts of the lowlevel jet. The occurring of heavy rainfall was induced by the strong cross equatorial flows, which provide sufficient water vapor for South China, and the end of heavy rainfall is featured by the buildup of the upperlevel easterly.
2007, 35(1):88-91.
Abstract:
The regional synoptic process with moderatetoheavy rain appeared in the eastern Chaidamu basin on 7 to 10 July 2005 is analyzed by means of the averaged field data. It is closely correlated with the branch trough separated from the Balkhash low trough and the lowvortex shear in the lower/middle troposphere over the Chaidamu basin, as well as the southwest warm/wet air around the subt ropical high. The convergence in the middle troposphere, the maintenance of divergence in the upper troposphere and high humidity, the coupling of strong vorticity and stability columns and the maintenance of the upper/lower jet flow are the main causes of the moderate to heavy synoptic weather process.
The regional synoptic process with moderatetoheavy rain appeared in the eastern Chaidamu basin on 7 to 10 July 2005 is analyzed by means of the averaged field data. It is closely correlated with the branch trough separated from the Balkhash low trough and the lowvortex shear in the lower/middle troposphere over the Chaidamu basin, as well as the southwest warm/wet air around the subt ropical high. The convergence in the middle troposphere, the maintenance of divergence in the upper troposphere and high humidity, the coupling of strong vorticity and stability columns and the maintenance of the upper/lower jet flow are the main causes of the moderate to heavy synoptic weather process.
2007, 35(1):92-95.
Abstract:
The temporal and spatial distribution characteristics of dusty weather in China in spring 2004 are analyzed on the basis of the data from surface synoptic maps (8 times per day) and T213 model products. The results show that there were 15 major dusty weather processes, more in March and less in April and May, and most of them were weak. Further research shows that because the temperature was higher and the precipitation was less than the normal value in the earlier months, the soil moisture was less and the soil surface was drier in spring in the northern China. When the cold air attacked North China frequently in March, more dusty days and severe dust storms occurred. After March, the dusty weather events decreased quickly because of less cold air activities and weaker dynamic condition.
The temporal and spatial distribution characteristics of dusty weather in China in spring 2004 are analyzed on the basis of the data from surface synoptic maps (8 times per day) and T213 model products. The results show that there were 15 major dusty weather processes, more in March and less in April and May, and most of them were weak. Further research shows that because the temperature was higher and the precipitation was less than the normal value in the earlier months, the soil moisture was less and the soil surface was drier in spring in the northern China. When the cold air attacked North China frequently in March, more dusty days and severe dust storms occurred. After March, the dusty weather events decreased quickly because of less cold air activities and weaker dynamic condition.
2007, 35(1):96-100.
Abstract:
An analysis is made of the climatological and variation characteristics of dust storms over the northern China on the basis of the data from 340 observation stations over the northern China from 1961 to 2003. The affected area of dust events is divided into three subregions: Northwest China, North China, and Northeast China and the regional climatic characteristics of dust storm eve nts are analyzed. The number of storm days shows a downward trend for most observation stations in the study area. Dust storms occurs more frequently in the western part of the northern China than in the eastern part, more in spring than in the other parts, more in the daytime than in the nighttime, and most frequently between 14:00 and 16:00 local time. Dust storms occur most frequently between 15:00 and 16:00 for Northwest China and around 14:00 in North China and Northeast China, more frequently in summer in Northwest China as compared to the other regions. There exist significant regional features in the daily, monthly and seasonal changes of dust storms in the northern China, most obviously in Northwest China.
An analysis is made of the climatological and variation characteristics of dust storms over the northern China on the basis of the data from 340 observation stations over the northern China from 1961 to 2003. The affected area of dust events is divided into three subregions: Northwest China, North China, and Northeast China and the regional climatic characteristics of dust storm eve nts are analyzed. The number of storm days shows a downward trend for most observation stations in the study area. Dust storms occurs more frequently in the western part of the northern China than in the eastern part, more in spring than in the other parts, more in the daytime than in the nighttime, and most frequently between 14:00 and 16:00 local time. Dust storms occur most frequently between 15:00 and 16:00 for Northwest China and around 14:00 in North China and Northeast China, more frequently in summer in Northwest China as compared to the other regions. There exist significant regional features in the daily, monthly and seasonal changes of dust storms in the northern China, most obviously in Northwest China.
2007, 35(1):101-106.
Abstract:
A case study is made of the dust storm occurred on 19, 20 April 2005 in the southern Hebei Province from the aspects of the climatic background, synoptic features, orographic effect and dynamical and thermodynamic mechanisms. The results indicate that before the occurrence of the storm, the local weak convergence, upward motion and unstable vertical structure drew local dusts up; the ups tream strong upward motion drew dusts up and then the upperair strong northwesterly transported the dusts to the downstream area horizontally; the dust storm occurred at the downstream area of the maximum positive helicity zone in the troposphere. The magnitude of the helicity in the troposphere is useful for the prediction of dust storms.
A case study is made of the dust storm occurred on 19, 20 April 2005 in the southern Hebei Province from the aspects of the climatic background, synoptic features, orographic effect and dynamical and thermodynamic mechanisms. The results indicate that before the occurrence of the storm, the local weak convergence, upward motion and unstable vertical structure drew local dusts up; the ups tream strong upward motion drew dusts up and then the upperair strong northwesterly transported the dusts to the downstream area horizontally; the dust storm occurred at the downstream area of the maximum positive helicity zone in the troposphere. The magnitude of the helicity in the troposphere is useful for the prediction of dust storms.
2007, 35(1):107-110.
Abstract:
The variation trend of the safe growth period for rice in recent 40 years over the southeastern Guizhou Province is analyzed on the basis of the daily mean air temperature data of 16 meteorological stations from 1961 to 2000. The results indicate that the rice safe growth period decreased by 7 days in recent 40 years over the southeastern Guizhou, by 10.6 days, 6.4 days, and 4.8 days for altitudes below 400 m, 400 to 600 m, over 800 m, respectively. On the contrary, at the altitudes between 600 m and 800 m, the growth period increased by 1.4 days. In the 1980s, the growth period decreased obviously with the minimum in 1980. In conclusion, the rice safe growth period took on an slight increasing trend at altitudes between 600 m and 800 m, and an obvious decreasing trend at altitu des below 600 m, as well as over 800 m.
The variation trend of the safe growth period for rice in recent 40 years over the southeastern Guizhou Province is analyzed on the basis of the daily mean air temperature data of 16 meteorological stations from 1961 to 2000. The results indicate that the rice safe growth period decreased by 7 days in recent 40 years over the southeastern Guizhou, by 10.6 days, 6.4 days, and 4.8 days for altitudes below 400 m, 400 to 600 m, over 800 m, respectively. On the contrary, at the altitudes between 600 m and 800 m, the growth period increased by 1.4 days. In the 1980s, the growth period decreased obviously with the minimum in 1980. In conclusion, the rice safe growth period took on an slight increasing trend at altitudes between 600 m and 800 m, and an obvious decreasing trend at altitu des below 600 m, as well as over 800 m.
2007, 35(1):111-114.
Abstract:
In order to explore whether AgI will pollute the environment after seeding, snow water sample data were collected in the snow enhancement experiment by using a ground AgI generator from December 2002 to March 2003 at Jianzishan Mountain of Beijing. Ag+ concentration and other chemistry components in the snow water are analyzed. The results show that Ag+ concentration varied obviously under different weather patterns. There is no direct linear relation between Ag+ concentration change and catalyst amount. The Ag+ concentration in the snow is far below the drinking water standards of China. There are obvious chemical char acteristics in the snow water: the concentrations of SO2-4 and NO-3 are the highest in the anions, and the concentrations of Ca2+ and NH+4 are the highest in the cations. The total ion concentration in the snow water is much lower than that of the heavily polluted fog water observed in the Beijing area.
In order to explore whether AgI will pollute the environment after seeding, snow water sample data were collected in the snow enhancement experiment by using a ground AgI generator from December 2002 to March 2003 at Jianzishan Mountain of Beijing. Ag+ concentration and other chemistry components in the snow water are analyzed. The results show that Ag+ concentration varied obviously under different weather patterns. There is no direct linear relation between Ag+ concentration change and catalyst amount. The Ag+ concentration in the snow is far below the drinking water standards of China. There are obvious chemical char acteristics in the snow water: the concentrations of SO2-4 and NO-3 are the highest in the anions, and the concentrations of Ca2+ and NH+4 are the highest in the cations. The total ion concentration in the snow water is much lower than that of the heavily polluted fog water observed in the Beijing area.
2007, 35(1):115-118.
Abstract:
The catalyst dosage in cloud seeding depends on the fields of temperature, water vapor, flow, background number concentration of hydrometeors, and spectral distributions of various particles in the seeded cloud. The formula for estimating the catalyst dosage of aircraft cloud seeding in stratiform clouds is put forward, on the basis of the supercooled cloud water content, saturation vapor density difference between ice and water surface, average accretion mass of ice crystal groups, effective diffusional scope of a catalyst, and nucleation rate. The equivalent masses of 50, 100, 150 μm for rain drop diameters are selected to represent the average accretion mass of ice crystal groups under different nucleation accretion mechanisms. For the homogeneous nucleation, the nucleation rate is taken as a constant of 1012 g-1, and for heterogeneous nucleation, taking the nucleation rates at temperature of －6 ℃，－8 ℃，－10 ℃ as examples, the dosages of catalyst are calculated according to the proposed formula. The estimated result agrees well with the widely used dosage according to foreign experiences. Also it is found that the dosage is obviously lower for most aircraft precipitation enhancement operations in China, compared with the estimated and recommended dosages.
The catalyst dosage in cloud seeding depends on the fields of temperature, water vapor, flow, background number concentration of hydrometeors, and spectral distributions of various particles in the seeded cloud. The formula for estimating the catalyst dosage of aircraft cloud seeding in stratiform clouds is put forward, on the basis of the supercooled cloud water content, saturation vapor density difference between ice and water surface, average accretion mass of ice crystal groups, effective diffusional scope of a catalyst, and nucleation rate. The equivalent masses of 50, 100, 150 μm for rain drop diameters are selected to represent the average accretion mass of ice crystal groups under different nucleation accretion mechanisms. For the homogeneous nucleation, the nucleation rate is taken as a constant of 1012 g-1, and for heterogeneous nucleation, taking the nucleation rates at temperature of －6 ℃，－8 ℃，－10 ℃ as examples, the dosages of catalyst are calculated according to the proposed formula. The estimated result agrees well with the widely used dosage according to foreign experiences. Also it is found that the dosage is obviously lower for most aircraft precipitation enhancement operations in China, compared with the estimated and recommended dosages.
2007, 35(1):119-122.
Abstract:
The analysis of satellite user requirements is the first and critical step to plan and manufacture meteorological satellites. To outline the frame of global meteorological satellites in the 21st century, WMO and CEOS began to collect user requirement information and establish global user databases for earth observing satellites from 1996, and devised the Rolling Requirements Review (RRR) process methods. The RRR process method and parts of the WMO/CEOS user database are introduced. The emphasis is put on the presentation and review of the establishing of satellite user requirements and its application in the quantitative evaluation of satellite observing capacity, to found a base for establishing the Chinese meteorological satellite user requirement database.
The analysis of satellite user requirements is the first and critical step to plan and manufacture meteorological satellites. To outline the frame of global meteorological satellites in the 21st century, WMO and CEOS began to collect user requirement information and establish global user databases for earth observing satellites from 1996, and devised the Rolling Requirements Review (RRR) process methods. The RRR process method and parts of the WMO/CEOS user database are introduced. The emphasis is put on the presentation and review of the establishing of satellite user requirements and its application in the quantitative evaluation of satellite observing capacity, to found a base for establishing the Chinese meteorological satellite user requirement database.
2007, 35(1):123-125.
Abstract:
A comparative analysis is made of the radiosonde－Lband radar system and the 59701 system by means of the onemonth synchronously observing data from the Jiuquan station, and the change of the data after the introduction of the Lband radar system is evaluated. The results indicate that generally speaking, the temperature, height, wind direction and velocity did not change obviously after using the Lband radar system; the relative humidity difference between the two systems increases with increasing altitude; the accuracy of the humidity records in the upper troposphere is improved obviously.
A comparative analysis is made of the radiosonde－Lband radar system and the 59701 system by means of the onemonth synchronously observing data from the Jiuquan station, and the change of the data after the introduction of the Lband radar system is evaluated. The results indicate that generally speaking, the temperature, height, wind direction and velocity did not change obviously after using the Lband radar system; the relative humidity difference between the two systems increases with increasing altitude; the accuracy of the humidity records in the upper troposphere is improved obviously.
2007, 35(1):126-129.
Abstract:
According to the structure and working principles of the darktube sunshine recorder, an introduction is made systematically to the method for inspecting the structure and installment errors of sunshine recorders by using sunlight path. It covers the shortages of the original methods in exhaustivity and accuracy. It is feasible to inspect the azimuth, level and latitude of the darktube sun shine recorder, as well as to inspect whether the installation is appropriate and the structure of the light screen is reasonable by using the sunlightpath method.
According to the structure and working principles of the darktube sunshine recorder, an introduction is made systematically to the method for inspecting the structure and installment errors of sunshine recorders by using sunlight path. It covers the shortages of the original methods in exhaustivity and accuracy. It is feasible to inspect the azimuth, level and latitude of the darktube sun shine recorder, as well as to inspect whether the installation is appropriate and the structure of the light screen is reasonable by using the sunlightpath method.
28 Common Methods for Reducing NPE Voltage for Lightning Protection Engineering of Information Systems
2007, 35(1):130-132.
Abstract:
An analysis is made of the mechanisms of high NPE voltage formation, which are induced by pure resistance, earth circuit loop, and common impedance, in connection with the common faults resulted from high NPE (neutral and protected earth conductor) voltage encountered in the operational lightning protection for the information system. The common causes for high NPE voltage and the m ethods for reducing NPE voltage are also discussed.
An analysis is made of the mechanisms of high NPE voltage formation, which are induced by pure resistance, earth circuit loop, and common impedance, in connection with the common faults resulted from high NPE (neutral and protected earth conductor) voltage encountered in the operational lightning protection for the information system. The common causes for high NPE voltage and the m ethods for reducing NPE voltage are also discussed.
2007, 35(1):133-138.
Abstract:
The A/D devices used in automatic weather stations and the authenticated devices are usually 12 bits or below, because the stability and accuracy of data conversion are determined by the bits of A/D devices, which cannot meet the needs of new meteorological equipment. Using the 24bit serial A/D device, AD7714, produced by Analog Devices Company, is used in the design of the new circuit s for the operational system. The functions and characteristics of AD7714, some of the source codes, and the AD7714based design methods of software and hardware are introduced. Besides, some technical problems encountered in practical application are discussed.
The A/D devices used in automatic weather stations and the authenticated devices are usually 12 bits or below, because the stability and accuracy of data conversion are determined by the bits of A/D devices, which cannot meet the needs of new meteorological equipment. Using the 24bit serial A/D device, AD7714, produced by Analog Devices Company, is used in the design of the new circuit s for the operational system. The functions and characteristics of AD7714, some of the source codes, and the AD7714based design methods of software and hardware are introduced. Besides, some technical problems encountered in practical application are discussed.
2007, 35(1):139-142.
Abstract:
The GPRS/CDMA wireless communication technology has many advantages, such as forever online, fast login, charge by amount of data, etc. This system is highly reliable, easy to install, and convenient to maintain. The Beijing Meteorological Bureau (BMB) developed a new GPS data transmission system based on GPRS/CDMA wireless communication technology to replace the former one based on modem and PSTN communication technology in October 2004. This new communication system collects data from GPS receivers located in the BMB GPS water vapor sensor network every half an hour automatically and has been put to operational use.
The GPRS/CDMA wireless communication technology has many advantages, such as forever online, fast login, charge by amount of data, etc. This system is highly reliable, easy to install, and convenient to maintain. The Beijing Meteorological Bureau (BMB) developed a new GPS data transmission system based on GPRS/CDMA wireless communication technology to replace the former one based on modem and PSTN communication technology in October 2004. This new communication system collects data from GPS receivers located in the BMB GPS water vapor sensor network every half an hour automatically and has been put to operational use.
2007, 35(1):143-147.
Abstract:
The characteristics and requirements of the intensive automatic weather station (AWS) network for meso and smallscale weather systems are analyzed in combination with the specific geographic conditions of Chengdu and the existing groundbased meteorological sounding technology. The characteristics of some new mobile communication networks and technology, such as GPRS, CDMA1X, etc., are compared, and their intrinsic relation in operationality is discussed. On the basis of the former experiences in the construction of the AWS network, a more rational datacollecting and application model is put forward.
The characteristics and requirements of the intensive automatic weather station (AWS) network for meso and smallscale weather systems are analyzed in combination with the specific geographic conditions of Chengdu and the existing groundbased meteorological sounding technology. The characteristics of some new mobile communication networks and technology, such as GPRS, CDMA1X, etc., are compared, and their intrinsic relation in operationality is discussed. On the basis of the former experiences in the construction of the AWS network, a more rational datacollecting and application model is put forward.
32 Construction, Installation and Maintenance of PrefecturalLevel Meteorological Communication Network
2007, 35(1):148-151.
Abstract:
The construction, installation and maintenance of the prefecturallevel wideband meteorological communication network are troduced from the aspects of communication line and network protocol selection, network topological structure design, and network equipment connection. Common faults encountered in the running of the communication network are analyzed and some useful hints for inspecting faults are given.
The construction, installation and maintenance of the prefecturallevel wideband meteorological communication network are troduced from the aspects of communication line and network protocol selection, network topological structure design, and network equipment connection. Common faults encountered in the running of the communication network are analyzed and some useful hints for inspecting faults are given.
2007, 35(1):152-156.
Abstract:
The metadata of 68 weather stations and the annual mean temperature series of 36 weather stations in Zhejiang Province are used to study the effect of observation environment variability on data homogeneity, and assessed by cumulative anomaly, boundary deviation and Ftest methods. The results show that from 1971 to 2004, the observation environment of the weather stations has changed d ramatically and the temperature temporal series of 39% stations were found heterogeneous, where the heterogeneity of about 36% stations are attributed to environment deterioration and that of about 57% stations to station relocation, which mainly occurred after the 1980s. The latitude and geographic environment differences before and after station relocation significantly influenced the homogeneity of temperature temporal series. More attention should be given to the effect of station relocation and environment variability.
The metadata of 68 weather stations and the annual mean temperature series of 36 weather stations in Zhejiang Province are used to study the effect of observation environment variability on data homogeneity, and assessed by cumulative anomaly, boundary deviation and Ftest methods. The results show that from 1971 to 2004, the observation environment of the weather stations has changed d ramatically and the temperature temporal series of 39% stations were found heterogeneous, where the heterogeneity of about 36% stations are attributed to environment deterioration and that of about 57% stations to station relocation, which mainly occurred after the 1980s. The latitude and geographic environment differences before and after station relocation significantly influenced the homogeneity of temperature temporal series. More attention should be given to the effect of station relocation and environment variability.
2007, 35(1):157-160.
Abstract:
The Automatic Precipitation ReportMaking Software for Meteorological Observation is developed for Shandong Province. The intelligentized filtration and manual checking, as well as report making, saving and printing, can conducted automatically, on the basis of the convention data files from automatic weather stations, taking time and precipitation as criteria. It can well meet the needs of the current precipitation report making operation, has a plain interface, is easy and convenient to use and has been put to operational use.
The Automatic Precipitation ReportMaking Software for Meteorological Observation is developed for Shandong Province. The intelligentized filtration and manual checking, as well as report making, saving and printing, can conducted automatically, on the basis of the convention data files from automatic weather stations, taking time and precipitation as criteria. It can well meet the needs of the current precipitation report making operation, has a plain interface, is easy and convenient to use and has been put to operational use.
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.