Volume 48,Issue 1,2020 Table of Contents
2020, 48(1):1-8.
Abstract:
Based on the data observed by the Xband dualpolarization mobile radar located at Lingang owned by the Shanghai Meteorological Service, the fixed ground clutter echo of the East China Sea Bridge can be recognized with reflectivity, differential reflectivity and correlation coefficient. Then the Geodesics and HRAP algorithms are introduced to transform the position of fixed ground clutter echoes from polar coordinate to geographic coordinate. The GPSmeasured geographic position of Hulu Highway (East China Sea Bridge section) from the National Geomatics Center of China is regarded as the true value. These two algorithms are examined separately under two types of atmospheric conditions: the clear echo with low humidity and the precipitation echo with high humidity. The verification algorithms include two methods: the number of samples located inside the bridge polygon (polygon verification) and the distance from the bridge centerline (centerline verification). The result shows that the Geodesics algorithm performs better compared with the HRAP algorithm both in polygon verification and centerline verification, indicating its importance in the practical application of radar projection conversion.
Based on the data observed by the Xband dualpolarization mobile radar located at Lingang owned by the Shanghai Meteorological Service, the fixed ground clutter echo of the East China Sea Bridge can be recognized with reflectivity, differential reflectivity and correlation coefficient. Then the Geodesics and HRAP algorithms are introduced to transform the position of fixed ground clutter echoes from polar coordinate to geographic coordinate. The GPSmeasured geographic position of Hulu Highway (East China Sea Bridge section) from the National Geomatics Center of China is regarded as the true value. These two algorithms are examined separately under two types of atmospheric conditions: the clear echo with low humidity and the precipitation echo with high humidity. The verification algorithms include two methods: the number of samples located inside the bridge polygon (polygon verification) and the distance from the bridge centerline (centerline verification). The result shows that the Geodesics algorithm performs better compared with the HRAP algorithm both in polygon verification and centerline verification, indicating its importance in the practical application of radar projection conversion.
2020, 48(1):9-14.
Abstract:
Because of radar beam occluded seriously by terrain, the quality of echo data is greatly disturbed. In this paper, the DEM (Digital Elevation Model) data of SRTM (Shuttle Radar Topography Mission) task and Google Company are used to calculate the beam occlusion rate of Sband radar at low elevation angle at Nanjiao of Beijing, and the echo reflectance correction relationship for the partial occlusion area is established. In the process of a largescale stratiform precipitation in Beijing on 19 May 2018, the qualitative and quantitative comparative analysis of the radar quantitative estimation of rainfall before and after the beam occlusion correction and the observation results from three rain gauges on the ground are performed. The results show: (1) Beam occlusion correction helps improve the spatial continuity of the reflectivity factor. The reflectance difference between 0.5° and 1.5° of elevation angle after the beam occlusion correction is reduced as a whole, which is consistent with the vertical profile of the stratiform cloud precipitation. (2) On the same day, between 09:00 and 11:00, the accuracy of the radar Quantitative Precipitation Estimation (QPE) after beam correction is improved. Using the Grading Standard Error and the Normalized Mean Bias (NMB) to evaluate the error between QPEs before and after the beam occlusion correction and measured values from the rain gauge, the result shows that the reflectivity after beam correction is more consistent with the measured rainfall from the rain gauge.
Because of radar beam occluded seriously by terrain, the quality of echo data is greatly disturbed. In this paper, the DEM (Digital Elevation Model) data of SRTM (Shuttle Radar Topography Mission) task and Google Company are used to calculate the beam occlusion rate of Sband radar at low elevation angle at Nanjiao of Beijing, and the echo reflectance correction relationship for the partial occlusion area is established. In the process of a largescale stratiform precipitation in Beijing on 19 May 2018, the qualitative and quantitative comparative analysis of the radar quantitative estimation of rainfall before and after the beam occlusion correction and the observation results from three rain gauges on the ground are performed. The results show: (1) Beam occlusion correction helps improve the spatial continuity of the reflectivity factor. The reflectance difference between 0.5° and 1.5° of elevation angle after the beam occlusion correction is reduced as a whole, which is consistent with the vertical profile of the stratiform cloud precipitation. (2) On the same day, between 09:00 and 11:00, the accuracy of the radar Quantitative Precipitation Estimation (QPE) after beam correction is improved. Using the Grading Standard Error and the Normalized Mean Bias (NMB) to evaluate the error between QPEs before and after the beam occlusion correction and measured values from the rain gauge, the result shows that the reflectivity after beam correction is more consistent with the measured rainfall from the rain gauge.
2020, 48(1):15-22.
Abstract:
The paper introduces the types of antenna systems for wind profile radar products at home and abroad. After the comparative study of various antenna systems, a fivebeam finite phasesweep phased array microstrip antenna subarray is designed. This antenna system consists of 21 square elements； each subarray contains 16 array elements, 4×4 square symmetric division, and the array element adopts the eastwest/northsouth twopoint coaxial backfeed feeding; in both sides in the subarrays, the equalamplitude and equalphase feeding networks are designed to realize horizontal polarization in eastwest and northsouth directions. The standing wave of all array elements is less than 1.2, improving the antenna detection sensitivity. The area of the phased array antenna and the weight of the antenna array are reduced. Combined with the subarray division, the Taylor weighting of the phased array antenna system is optimized. The antenna has the twodimensional stepping sweep function to form five beams in the airspace. It is applied to the TWP3 boundary layer wind profiler radar to improve the overall performance. The radar detection height is greater than 5 km.
The paper introduces the types of antenna systems for wind profile radar products at home and abroad. After the comparative study of various antenna systems, a fivebeam finite phasesweep phased array microstrip antenna subarray is designed. This antenna system consists of 21 square elements； each subarray contains 16 array elements, 4×4 square symmetric division, and the array element adopts the eastwest/northsouth twopoint coaxial backfeed feeding; in both sides in the subarrays, the equalamplitude and equalphase feeding networks are designed to realize horizontal polarization in eastwest and northsouth directions. The standing wave of all array elements is less than 1.2, improving the antenna detection sensitivity. The area of the phased array antenna and the weight of the antenna array are reduced. Combined with the subarray division, the Taylor weighting of the phased array antenna system is optimized. The antenna has the twodimensional stepping sweep function to form five beams in the airspace. It is applied to the TWP3 boundary layer wind profiler radar to improve the overall performance. The radar detection height is greater than 5 km.
2020, 48(1):23-30.
Abstract:
In this paper, the spatial uniformity of natural rainfall is studied by using 10 m×20 m and 10 m×10 m observation networks with a resolution of 1 m. A rainfall test is carried out mainly by using selfmade rainfall cups. The applied mathematical methods include Christianson’s uniform coefficient, distribution uniformity coefficient, rainfall deviation coefficient, rainfall extreme ratio coefficient, and oneway ANOVA. At the same time, the problem of setting the interval of rainfall measuring instrument in dynamic comparison experiment is discussed. The results show that the spatial uniformity of natural rainfall in the observation field is good, and the uniformity index has good consistency; the wind has little effect on the spatial uniformity of rainfall in the observation field, but the difference of rainfall has some effect on the spatial uniformity; the installation interval of rainfall measuring instruments should be less than 5 m in the dynamic comparison experiment, and it is feasible for some smallscale rainfall measuring instruments to set up at a interval of 1 m, such as collecting cups.
In this paper, the spatial uniformity of natural rainfall is studied by using 10 m×20 m and 10 m×10 m observation networks with a resolution of 1 m. A rainfall test is carried out mainly by using selfmade rainfall cups. The applied mathematical methods include Christianson’s uniform coefficient, distribution uniformity coefficient, rainfall deviation coefficient, rainfall extreme ratio coefficient, and oneway ANOVA. At the same time, the problem of setting the interval of rainfall measuring instrument in dynamic comparison experiment is discussed. The results show that the spatial uniformity of natural rainfall in the observation field is good, and the uniformity index has good consistency; the wind has little effect on the spatial uniformity of rainfall in the observation field, but the difference of rainfall has some effect on the spatial uniformity; the installation interval of rainfall measuring instruments should be less than 5 m in the dynamic comparison experiment, and it is feasible for some smallscale rainfall measuring instruments to set up at a interval of 1 m, such as collecting cups.
2020, 48(1):31-39.
Abstract:
The initial profile, which is calculated by the eigenvector regression algorithm in the groundbased hyperspectral remote sensing, has a significant impact on the accuracy of the physical retrieval. Based on the eigenvector regression algorithm, the similarities and differences between the retrievals of temperature profiles and water vapor profiles are analyzed using the radiance data observed by AERI and coincident radiosonde profiles. The optimal number of principal components is analyzed when retrieving the temperature and water vapor profiles. Considering both the accuracy and the information contained in the eigenvectors, the optimal numbers of principal components are both set to 7. In order to improve the accuracy of remote sensing, the surface temperature, humidity and pressure are introduced as the influence factors. The experiment results show that the introduction of surface pressure has a better performance than the other two single meteorological elements and the assemble of factors composed of all three meteorological elements, especially for the accuracy and stability of temperature and water vapor profiles in the middle and lower parts of the boundary layer. With the decrease of altitude, the RMSE of temperature profiles decreases to a maximum of 1.5 K, and the RMSE of temperature profiles decreases to a maximum of 0.42 g/kg. At the same time, the impact of logarithmic water vapor mixing ratio on the retrieval of water vapor profiles is analyzed. The result shows that the introduction of the logarithmic profile has little effect on the accuracy of the retrieval. However, the accuracy of the water vapor profile gains more than 12% when converting mixing ratio to relative humidity.
The initial profile, which is calculated by the eigenvector regression algorithm in the groundbased hyperspectral remote sensing, has a significant impact on the accuracy of the physical retrieval. Based on the eigenvector regression algorithm, the similarities and differences between the retrievals of temperature profiles and water vapor profiles are analyzed using the radiance data observed by AERI and coincident radiosonde profiles. The optimal number of principal components is analyzed when retrieving the temperature and water vapor profiles. Considering both the accuracy and the information contained in the eigenvectors, the optimal numbers of principal components are both set to 7. In order to improve the accuracy of remote sensing, the surface temperature, humidity and pressure are introduced as the influence factors. The experiment results show that the introduction of surface pressure has a better performance than the other two single meteorological elements and the assemble of factors composed of all three meteorological elements, especially for the accuracy and stability of temperature and water vapor profiles in the middle and lower parts of the boundary layer. With the decrease of altitude, the RMSE of temperature profiles decreases to a maximum of 1.5 K, and the RMSE of temperature profiles decreases to a maximum of 0.42 g/kg. At the same time, the impact of logarithmic water vapor mixing ratio on the retrieval of water vapor profiles is analyzed. The result shows that the introduction of the logarithmic profile has little effect on the accuracy of the retrieval. However, the accuracy of the water vapor profile gains more than 12% when converting mixing ratio to relative humidity.
2020, 48(1):40-45.
Abstract:
In order to further evaluate the performance of the infrared thermometers of groundbased microwave radiometers to observe clouds, the cloud based height data measured by a MWP967KV infrared thermometer equipped in a groundbased microwave radiometer and a K/LLX502Btyped laser cloud detector, which were set up in the Guangzhou Field Experiment Site for Lightning Research and Tests from May to July of 2017 and 2018, are collected. At the same time, the manual observations of weather conditions and cloud types are used for classification. The performance of the infrared thermometer for cloud identification and cloud based height measurement is analyzed under different weather conditions and cloud types. The results show that the infrared thermometer in the groundbased microwave radiometer has good cloud recognition capability, and the accuracy rate is 80.4%. The failure to identify cloud mainly occurs in the cloudy situation due to the observation angle. The correlation coefficient of the cloud based height measured by the two instruments is 0.63, which means good consistency. The cloud based heights measured by the infrared thermometer are always higher than those of the laser cloud detector, and the consistency of cloud based heights measured by the two instruments at low clouds and overcast conditions is better than those measured at middle, high clouds and clouds conditions, because the observation principles are different. It is feasible for the infrared thermometers in the microwave radiometers to identify the clouds and measure cloud based heights, especially under low cloudy and overcast conditions.
In order to further evaluate the performance of the infrared thermometers of groundbased microwave radiometers to observe clouds, the cloud based height data measured by a MWP967KV infrared thermometer equipped in a groundbased microwave radiometer and a K/LLX502Btyped laser cloud detector, which were set up in the Guangzhou Field Experiment Site for Lightning Research and Tests from May to July of 2017 and 2018, are collected. At the same time, the manual observations of weather conditions and cloud types are used for classification. The performance of the infrared thermometer for cloud identification and cloud based height measurement is analyzed under different weather conditions and cloud types. The results show that the infrared thermometer in the groundbased microwave radiometer has good cloud recognition capability, and the accuracy rate is 80.4%. The failure to identify cloud mainly occurs in the cloudy situation due to the observation angle. The correlation coefficient of the cloud based height measured by the two instruments is 0.63, which means good consistency. The cloud based heights measured by the infrared thermometer are always higher than those of the laser cloud detector, and the consistency of cloud based heights measured by the two instruments at low clouds and overcast conditions is better than those measured at middle, high clouds and clouds conditions, because the observation principles are different. It is feasible for the infrared thermometers in the microwave radiometers to identify the clouds and measure cloud based heights, especially under low cloudy and overcast conditions.
2020, 48(1):46-51.
Abstract:
The research on the surface environmental parameters around stations using the GNSS reflected signals is one of the research hotspots in the field of remote sensing in recent years. Based on the characteristics of GPS SNR (SignaltoNoise Ratio) and signal amplitude, this paper studies the snow depth detection algorithm using GPS SNR observations. The comparison experiment uses the operational observation data of the survey GPS receiver located in the National Meteorological Observatory in Qiqihar of Heilongjiang Province to verify the groundbased GPS inversion snow depth algorithm. The GPS inversion snow depth algorithm is verified, and the experimental comparison results show that the snow depth of groundbased GPS inversion is in good agreement with the measured values, with a standard deviation of 204 cm and a correlation coefficient of 094. Therefore, snow depth detection can be performed using the groundbased GPS observations. Using the groundbased GPS inversion snow depth technology, the meteorological departments can further carry out snow cover environmental monitoring research based on the existing groundbased GPS water vapor monitoring network.
The research on the surface environmental parameters around stations using the GNSS reflected signals is one of the research hotspots in the field of remote sensing in recent years. Based on the characteristics of GPS SNR (SignaltoNoise Ratio) and signal amplitude, this paper studies the snow depth detection algorithm using GPS SNR observations. The comparison experiment uses the operational observation data of the survey GPS receiver located in the National Meteorological Observatory in Qiqihar of Heilongjiang Province to verify the groundbased GPS inversion snow depth algorithm. The GPS inversion snow depth algorithm is verified, and the experimental comparison results show that the snow depth of groundbased GPS inversion is in good agreement with the measured values, with a standard deviation of 204 cm and a correlation coefficient of 094. Therefore, snow depth detection can be performed using the groundbased GPS observations. Using the groundbased GPS inversion snow depth technology, the meteorological departments can further carry out snow cover environmental monitoring research based on the existing groundbased GPS water vapor monitoring network.
2020, 48(1):52-58.
Abstract:
In the ANUSPLIN thinplate smooth spline interpolation, the accuracy of interpolation results is mainly determined by choosing the independent covariates. This article selected the weather processes with poor visibility in heavy fogs and hazes from 2017 to 2019, using 183 visibility observation sites to interpolate visibility, and introduced the Himawari8 satellite channel data and DEM data as covariables to improve the visibility interpolation results. The visibility interpolation effects are compared and analyzed. The results show that the visibility interpolation effect of Himawari8 data and DEM data as covariables is significantly improved in accuracy, especially in the inversion of the boundary range and texture of fog and haze areas. The accuracy of interpolation using the covariate method and interpolation only using the observed values is greatly improved.
In the ANUSPLIN thinplate smooth spline interpolation, the accuracy of interpolation results is mainly determined by choosing the independent covariates. This article selected the weather processes with poor visibility in heavy fogs and hazes from 2017 to 2019, using 183 visibility observation sites to interpolate visibility, and introduced the Himawari8 satellite channel data and DEM data as covariables to improve the visibility interpolation results. The visibility interpolation effects are compared and analyzed. The results show that the visibility interpolation effect of Himawari8 data and DEM data as covariables is significantly improved in accuracy, especially in the inversion of the boundary range and texture of fog and haze areas. The accuracy of interpolation using the covariate method and interpolation only using the observed values is greatly improved.
2020, 48(1):59-67.
Abstract:
Based on the National Platform for Common Geospatial Information Services, the Yunnan Digital Country Project and the Mapinfo Public Data as data sources, the Kunming Fine Geographic Information System (GIS) is developed independently as fined as a town, highway, administrative village and natural village under the C# development environment, which solves the problem of lacking the fined GIS data in the baselevel meteorological services. This paper introduces the parsing and mapping processes of the standardformat base data and precautions, and realizes the operational application of the standardformat base data of weather radar in the baselevel meteorological service in China. During the operational application, it is founded that the echo intensity of the standardformat early base data from CC weather radar is seriously weakened; the fusion application of the Kunming Fined GIS and Kunming weather radar echo images can accurately locate the strong radar echo area, which can guide the refined meteorological service, and improve the capability of fine weather warning, shortterm and nearrefined forecasting and nowcasting and disaster prevention and mitigation.
Based on the National Platform for Common Geospatial Information Services, the Yunnan Digital Country Project and the Mapinfo Public Data as data sources, the Kunming Fine Geographic Information System (GIS) is developed independently as fined as a town, highway, administrative village and natural village under the C# development environment, which solves the problem of lacking the fined GIS data in the baselevel meteorological services. This paper introduces the parsing and mapping processes of the standardformat base data and precautions, and realizes the operational application of the standardformat base data of weather radar in the baselevel meteorological service in China. During the operational application, it is founded that the echo intensity of the standardformat early base data from CC weather radar is seriously weakened; the fusion application of the Kunming Fined GIS and Kunming weather radar echo images can accurately locate the strong radar echo area, which can guide the refined meteorological service, and improve the capability of fine weather warning, shortterm and nearrefined forecasting and nowcasting and disaster prevention and mitigation.
2020, 48(1):68-75.
Abstract:
FY4A is the first static meteorological satellite carrying a Lightning Mapping Imager (LMI), and the software implanted in the heavyloaded chips which can be renewed automatically by receiving the signals from the earth station in 2 ms, is able to complete the data processing for the multipleframe lightning signals in 400×600 pixel and generate the data in time, from lightning and ground marking objects. FY4A is a kind of SEU (Single Event Upset)sensitive device and needs to use numerous methods to make a SEU protection due to the complexity of the nearearth environment. In the construction project of the ground application system of Satellite FY4, in accordance with different effects of FPGA SEU on lightning detecting equipment, combined with data logical relationship amongst lightning affairs and systematic resources, we designed and arranged a singleevent (SE) testing program and achieved the FPGA (Field Programmable Gate Array) SEU abnormity automatic identification. Meanwhile, according to the characteristics of lightning observation and the efficient requirement of lightning detecting equipment, we use multiple comprehensive methods such as automatic judgment and order, dynamitic and timed refreshments, software and hardware recovery, etc., to secure an automatic recovery of FPGA SEU. Based on the above, the FY4A LMI has dramatically avoided the negative effect of SEU on lightning detecting equipment.
FY4A is the first static meteorological satellite carrying a Lightning Mapping Imager (LMI), and the software implanted in the heavyloaded chips which can be renewed automatically by receiving the signals from the earth station in 2 ms, is able to complete the data processing for the multipleframe lightning signals in 400×600 pixel and generate the data in time, from lightning and ground marking objects. FY4A is a kind of SEU (Single Event Upset)sensitive device and needs to use numerous methods to make a SEU protection due to the complexity of the nearearth environment. In the construction project of the ground application system of Satellite FY4, in accordance with different effects of FPGA SEU on lightning detecting equipment, combined with data logical relationship amongst lightning affairs and systematic resources, we designed and arranged a singleevent (SE) testing program and achieved the FPGA (Field Programmable Gate Array) SEU abnormity automatic identification. Meanwhile, according to the characteristics of lightning observation and the efficient requirement of lightning detecting equipment, we use multiple comprehensive methods such as automatic judgment and order, dynamitic and timed refreshments, software and hardware recovery, etc., to secure an automatic recovery of FPGA SEU. Based on the above, the FY4A LMI has dramatically avoided the negative effect of SEU on lightning detecting equipment.
2020, 48(1):76-80.
Abstract:
At present, there are two types of verification of platinum resistance temperature sensors in automatic meteorological stations in China,i.e., onsite verification and laboratory verification. As instructed in the related verification regulations (JJG (Meteorology) 0022015 Platinum Resistance Temperature Sensor of Automatic Weather Station), onsite verification and laboratory verification are separately performed for the same platinum resistance temperature sensor, and the measurement uncertainty is determined using the GUM (Guide to the Uncertainty in Measurement) method based on the results of both types of verification. The result shows that the uncertainty evaluation of onsite verification is higher than that of laboratory verification. The causes of differences in measurement uncertainty between the two types of verification are analyzed. It is suggested that the laboratory verification should be used in the verification of platinum resistance temperature sensors for automatic meteorological stations.
At present, there are two types of verification of platinum resistance temperature sensors in automatic meteorological stations in China,i.e., onsite verification and laboratory verification. As instructed in the related verification regulations (JJG (Meteorology) 0022015 Platinum Resistance Temperature Sensor of Automatic Weather Station), onsite verification and laboratory verification are separately performed for the same platinum resistance temperature sensor, and the measurement uncertainty is determined using the GUM (Guide to the Uncertainty in Measurement) method based on the results of both types of verification. The result shows that the uncertainty evaluation of onsite verification is higher than that of laboratory verification. The causes of differences in measurement uncertainty between the two types of verification are analyzed. It is suggested that the laboratory verification should be used in the verification of platinum resistance temperature sensors for automatic meteorological stations.
2020, 48(1):81-87.
Abstract:
Based on the NCEP GDAS/FNL data and MODIS satellite data, the synoptic situation and cloud microphysical characteristics of a cold front process from the Huanghuai region to Jiangnan region on 19 February 2013 are diagnosed. The circulation field and thick clouds, low temperature and enough liquid water were conducive to aircraft icing in most areas from Jianghuai to the southern Huanghuai region, including the southern Henan Province. The IC index method and Willam algorithm are used to forecast the probability and intensity of aircraft icing. Through the verification based on the nearest time aircraft reports, it is found that the resolution of MODIS satellite data by the Willam algorithm is much higher than that of NCEP GDAS/FNL data by the IC index method, and the prediction accuracy is higher also than that by the IC index method. Using two methods simultaneously in practical work is helpful to reliable early warning service for aircraft icing.
Based on the NCEP GDAS/FNL data and MODIS satellite data, the synoptic situation and cloud microphysical characteristics of a cold front process from the Huanghuai region to Jiangnan region on 19 February 2013 are diagnosed. The circulation field and thick clouds, low temperature and enough liquid water were conducive to aircraft icing in most areas from Jianghuai to the southern Huanghuai region, including the southern Henan Province. The IC index method and Willam algorithm are used to forecast the probability and intensity of aircraft icing. Through the verification based on the nearest time aircraft reports, it is found that the resolution of MODIS satellite data by the Willam algorithm is much higher than that of NCEP GDAS/FNL data by the IC index method, and the prediction accuracy is higher also than that by the IC index method. Using two methods simultaneously in practical work is helpful to reliable early warning service for aircraft icing.
2020, 48(1):88-96.
Abstract:
Using the data of conventional observation, automatic weather station (AWS) observation, and Doppler weather radar observation, the tornado activity characteristics in the Pearl River Delta and environmental conditions are studied. The work presents the tornado synoptic model and early warning indexes. The forecasting and warning method and procedures towards the tornado events in the Pearl River Delta are built and applied to two tornado events in 2018. The results indicate that on the base of the method, the tornado warning for Nanhai District of Foshan was successfully issued 58 minutes in advance for Typhoon Ewiniar on 8 June 2018. On 17 September 2018, another tornado warning for Sanshui District of Foshan was successfully issued 37 minutes in advance for Typhoon Mangkhut. It is proved that this method is feasible.
Using the data of conventional observation, automatic weather station (AWS) observation, and Doppler weather radar observation, the tornado activity characteristics in the Pearl River Delta and environmental conditions are studied. The work presents the tornado synoptic model and early warning indexes. The forecasting and warning method and procedures towards the tornado events in the Pearl River Delta are built and applied to two tornado events in 2018. The results indicate that on the base of the method, the tornado warning for Nanhai District of Foshan was successfully issued 58 minutes in advance for Typhoon Ewiniar on 8 June 2018. On 17 September 2018, another tornado warning for Sanshui District of Foshan was successfully issued 37 minutes in advance for Typhoon Mangkhut. It is proved that this method is feasible.
2020, 48(1):97-106.
Abstract:
Mesoscale models have the spinup problem in nowcasting (0 to 2 hour forecast), so extrapolation forecast has become an indispensable technical method for nowcasting. At present, the extrapolation vectors in INCA (Integrated Nowcasting through Comprehensive Analysis system) precipitation extrapolation prediction are deterministic and do not change with forecast time, which results in that the velocity and direction of precipitation movement do not change with the forecast time, which is inconsistent with the reality. It is necessary to consider the variations of extrapolation vectors with time and to make them as the disturbances of extrapolation vectors adding to deterministic extrapolation vectors. Extrapolated vector perturbations are determined by the variations of extrapolated vector with time, which is the deviation of extrapolated vectors at adjacent times. The adjacent 10minute extrapolated vector deviation during July 2017 of the INCA system is statistically calculated to represent the variation of extrapolated vectors with time. Extrapolation vectors are the current and future precipitation moving speed and direction. For easy understanding, if precipitation moves northeast, this paper stipulates that the direction of extrapolation vectors is northeast. The statistical results over the ChangjiangHuaihe Region demonstrate that the deviations are mainly in southwest and northeast. The larger the extrapolation velocities are, the greater the deviations velocities will be. Vast majority of precipitation occurs in front of troughs, so northeast extrapolation vectors account for 73%. 〖JP2〗Based on the statistical samples of extrapolated vector deviation, several extrapolated vector perturbations are generated randomly based on the distribution of extrapolated vector deviation, and several uncertain extrapolated vectors are obtained. The deterministic extrapolated prediction of INCA is changed to 0to2 hour extrapolated ensemble precipitation prediction. The ensemble forecast effects are verified by the Mean Square Error (MSE), TS score, BIAS score and Brier Skill score. The results demonstrate that the results of ensemble forecast are better than that of deterministic forecast with increasing forecast time. Therefore, the accuracy of precipitation extrapolation prediction can be improved by considering the variations of extrapolation vectors with time.〖JP〗
Mesoscale models have the spinup problem in nowcasting (0 to 2 hour forecast), so extrapolation forecast has become an indispensable technical method for nowcasting. At present, the extrapolation vectors in INCA (Integrated Nowcasting through Comprehensive Analysis system) precipitation extrapolation prediction are deterministic and do not change with forecast time, which results in that the velocity and direction of precipitation movement do not change with the forecast time, which is inconsistent with the reality. It is necessary to consider the variations of extrapolation vectors with time and to make them as the disturbances of extrapolation vectors adding to deterministic extrapolation vectors. Extrapolated vector perturbations are determined by the variations of extrapolated vector with time, which is the deviation of extrapolated vectors at adjacent times. The adjacent 10minute extrapolated vector deviation during July 2017 of the INCA system is statistically calculated to represent the variation of extrapolated vectors with time. Extrapolation vectors are the current and future precipitation moving speed and direction. For easy understanding, if precipitation moves northeast, this paper stipulates that the direction of extrapolation vectors is northeast. The statistical results over the ChangjiangHuaihe Region demonstrate that the deviations are mainly in southwest and northeast. The larger the extrapolation velocities are, the greater the deviations velocities will be. Vast majority of precipitation occurs in front of troughs, so northeast extrapolation vectors account for 73%. 〖JP2〗Based on the statistical samples of extrapolated vector deviation, several extrapolated vector perturbations are generated randomly based on the distribution of extrapolated vector deviation, and several uncertain extrapolated vectors are obtained. The deterministic extrapolated prediction of INCA is changed to 0to2 hour extrapolated ensemble precipitation prediction. The ensemble forecast effects are verified by the Mean Square Error (MSE), TS score, BIAS score and Brier Skill score. The results demonstrate that the results of ensemble forecast are better than that of deterministic forecast with increasing forecast time. Therefore, the accuracy of precipitation extrapolation prediction can be improved by considering the variations of extrapolation vectors with time.〖JP〗
2020, 48(1):107-114.
Abstract:
Based on the meteorological observation data, ERAInterim and NCEP/NCAR reanalysis data，two lowtemperature freezing rain/snow weather events affecting Liuzhou from 21 to 26 January 2016 and from 28 December 2018 to 2 January 2019 are compared. The results show that： during the two processes, the middle high latitude was in the pattern of two troughs and one ridge, and the blocking high pressure was 28 dagpm stronger than that in the same period of the normal year； the continuation of cold advection transportation and the supplement of cold air flow at upper levels was an important reason for the lower temperature in 2018 than in 2016; continuous moisture convergence in the middlelower layer, longterm inversion layer maintenance and strong inversion intensity made the duration and range of snowfall stronger in 2018 than in 2016; the strong northwest airflow in the middle layer made the cold air move southward rapidly during the process of 2016. The jet stream at 700 hPa and the wind speed convergence zone were more southern than normal at 850 hPa, resulting in the snowfall mainly in the southern Guangxi, while there was only a small amount of snow in Liuzhou, and the temperature was rising quickly.
Based on the meteorological observation data, ERAInterim and NCEP/NCAR reanalysis data，two lowtemperature freezing rain/snow weather events affecting Liuzhou from 21 to 26 January 2016 and from 28 December 2018 to 2 January 2019 are compared. The results show that： during the two processes, the middle high latitude was in the pattern of two troughs and one ridge, and the blocking high pressure was 28 dagpm stronger than that in the same period of the normal year； the continuation of cold advection transportation and the supplement of cold air flow at upper levels was an important reason for the lower temperature in 2018 than in 2016; continuous moisture convergence in the middlelower layer, longterm inversion layer maintenance and strong inversion intensity made the duration and range of snowfall stronger in 2018 than in 2016; the strong northwest airflow in the middle layer made the cold air move southward rapidly during the process of 2016. The jet stream at 700 hPa and the wind speed convergence zone were more southern than normal at 850 hPa, resulting in the snowfall mainly in the southern Guangxi, while there was only a small amount of snow in Liuzhou, and the temperature was rising quickly.
2020, 48(1):115-120.
Abstract:
Based on the metadata archive, the detection of inhomogeneity and the homogenization of raw dailymean wind speed data of 179 meteorological observation stations from 1951 to 2015 in the region of Beijing, Tianjin and Hebei Provinces are conducted. The results show: in the order of the ratio of contributions to inhomogeneity, the instrument switching accounts for 40%, the station relocating 34%, the schedule changing of the observational task 18%, environment changing around the station 8%. The wind speed decreased in both the raw data and the homogenized data, and the latter declined significantly faster. Their linear trends have the similar characteristics, with a distribution: there is a banded region of the fastest declining wind speed from northwest to southeast, and the second fastest declining area in the western Hebei, and the slowest declining area in the northeastern Hebei. The faster declining rate is found mainly in the areas north of 39°N in the homogenized data, which can accurately reflect the climatic change characteristic and is reliable.
Based on the metadata archive, the detection of inhomogeneity and the homogenization of raw dailymean wind speed data of 179 meteorological observation stations from 1951 to 2015 in the region of Beijing, Tianjin and Hebei Provinces are conducted. The results show: in the order of the ratio of contributions to inhomogeneity, the instrument switching accounts for 40%, the station relocating 34%, the schedule changing of the observational task 18%, environment changing around the station 8%. The wind speed decreased in both the raw data and the homogenized data, and the latter declined significantly faster. Their linear trends have the similar characteristics, with a distribution: there is a banded region of the fastest declining wind speed from northwest to southeast, and the second fastest declining area in the western Hebei, and the slowest declining area in the northeastern Hebei. The faster declining rate is found mainly in the areas north of 39°N in the homogenized data, which can accurately reflect the climatic change characteristic and is reliable.
2020, 48(1):121-126.
Abstract:
The magnitude of lightning current is an important parameter for studying the distribution of lightning in a region. This paper uses the lightning monitoring data of the ADTD lightning positioning system of Henan Province from 2008 to 2017 to fit the characteristic function of the formula recommended by the protocol method, IEEE working group and CIGRE working group. The results show that there are differences in the probability distribution of positive and negative lightning current values in Henan. The formula recommended by the IEEE Working Group is used to fit the probability distribution of the accumulated magnitude of the lightning current in Henan Province. At the same time, the expression of the probability distribution function of the accumulated magnitude of the lightning current in Henan Province is obtained. It provides an indispensable technical reference for studying the characteristics of lightning in Henan Province and carrying out lightning protection and disaster reduction.
The magnitude of lightning current is an important parameter for studying the distribution of lightning in a region. This paper uses the lightning monitoring data of the ADTD lightning positioning system of Henan Province from 2008 to 2017 to fit the characteristic function of the formula recommended by the protocol method, IEEE working group and CIGRE working group. The results show that there are differences in the probability distribution of positive and negative lightning current values in Henan. The formula recommended by the IEEE Working Group is used to fit the probability distribution of the accumulated magnitude of the lightning current in Henan Province. At the same time, the expression of the probability distribution function of the accumulated magnitude of the lightning current in Henan Province is obtained. It provides an indispensable technical reference for studying the characteristics of lightning in Henan Province and carrying out lightning protection and disaster reduction.
2020, 48(1):127-131.
Abstract:
By use of Chongqing lightning location data from 2007 to 2016 and the digital elevation model of this region, applying the GIS spatial analysis and mathematical and statistical methods, an analysis is made of the influence of topography on main lightning hazard factors. The results show that the altitude and slope direction have an impact on the CloudtoGround (CG) flash density, and the slope has a negative correlation with the CG flash density. The distribution of the ground flash intensity between different slope directions has obvious differences, and the altitude, slope and CG flash intensity are not correlated.
By use of Chongqing lightning location data from 2007 to 2016 and the digital elevation model of this region, applying the GIS spatial analysis and mathematical and statistical methods, an analysis is made of the influence of topography on main lightning hazard factors. The results show that the altitude and slope direction have an impact on the CloudtoGround (CG) flash density, and the slope has a negative correlation with the CG flash density. The distribution of the ground flash intensity between different slope directions has obvious differences, and the altitude, slope and CG flash intensity are not correlated.
2020, 48(1):132-140.
Abstract:
The power grid in Guangdong Province is densely distributed and covers a wide area. The surface environment is complex, so it is vulnerable to natural disasters. As one of the disasters, wildfires have a great impact on the electric transmission lines, and it is of great significance to realize the monitoring and early warning of wildfires in a timely and effective manner. In this paper, based on the principles of MODIS mountain fire identification, the satellite remote sensing monitoring of mountain fires in Guangdong is carried out. In order to improve the monitoring accuracy, the brightness and background brightness temperature of typical fire points in 2017 in Guangdong Province are calculated based on factors such as time, space and cloud coverage. According to the statistical results, the threshold value applicable to the local fire point identification is obtained. It is verified that the accuracy of this method can reach 905% in the automatic identification of fire spots in Guangdong Province and surrounding areas on 3 April 2017, and this method has played an early warning role in the monitoring of mountain fires in Guangdong Province.
The power grid in Guangdong Province is densely distributed and covers a wide area. The surface environment is complex, so it is vulnerable to natural disasters. As one of the disasters, wildfires have a great impact on the electric transmission lines, and it is of great significance to realize the monitoring and early warning of wildfires in a timely and effective manner. In this paper, based on the principles of MODIS mountain fire identification, the satellite remote sensing monitoring of mountain fires in Guangdong is carried out. In order to improve the monitoring accuracy, the brightness and background brightness temperature of typical fire points in 2017 in Guangdong Province are calculated based on factors such as time, space and cloud coverage. According to the statistical results, the threshold value applicable to the local fire point identification is obtained. It is verified that the accuracy of this method can reach 905% in the automatic identification of fire spots in Guangdong Province and surrounding areas on 3 April 2017, and this method has played an early warning role in the monitoring of mountain fires in Guangdong Province.
2020, 48(1):141-146.
Abstract:
By studying the cold and freezing damage to tea from budding period to leaf expansion period, this paper uses the daybyday meteorological data of February to April from 17 weather stations from 1987 to 2016 in Anxi County and the yield data of various tea growing regions in Anxi to determine the meteorological indicators of cold and freezing damage to tea trees for indexbased weather insurance, analyze the relationship between daily extreme low temperature and tea failure rate, as well as establish the cold and freezing damage index model of tea trees. Moreover, we calculate the incidence of cold and freezing damage of different severity in different tea growing regions in Anxi, apply the pure premium method to determine the premium, and based on the actual situation of policyguided agricultural insurance in Fujian Province, formulate the compensation thresholds and compensation standards for cold and freezing damage insurance in different growing regions of tea trees and design the insurance contract for tea cold and freezing damage weather indexes in Anxi County. The designed insurance products based on tea cold and freezing damage weather indexes take the objective meteorological data as the loss assessment basis, first time in agricultural insurance and can serve as an effective risk transfer means for tea growers. Moreover, it provides technical support for insurance companies to develop new insurance products.
By studying the cold and freezing damage to tea from budding period to leaf expansion period, this paper uses the daybyday meteorological data of February to April from 17 weather stations from 1987 to 2016 in Anxi County and the yield data of various tea growing regions in Anxi to determine the meteorological indicators of cold and freezing damage to tea trees for indexbased weather insurance, analyze the relationship between daily extreme low temperature and tea failure rate, as well as establish the cold and freezing damage index model of tea trees. Moreover, we calculate the incidence of cold and freezing damage of different severity in different tea growing regions in Anxi, apply the pure premium method to determine the premium, and based on the actual situation of policyguided agricultural insurance in Fujian Province, formulate the compensation thresholds and compensation standards for cold and freezing damage insurance in different growing regions of tea trees and design the insurance contract for tea cold and freezing damage weather indexes in Anxi County. The designed insurance products based on tea cold and freezing damage weather indexes take the objective meteorological data as the loss assessment basis, first time in agricultural insurance and can serve as an effective risk transfer means for tea growers. Moreover, it provides technical support for insurance companies to develop new insurance products.
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.