ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 10,2013 Table of Contents
2013, 39(10):1233-1246.
DOI: 10.7519/j.issn.1000-0526.2013.10.001
Abstract:
In the rainfall probabilistic forecasting, information from the end of the probability distribution function should be applied. Then better forecast about rain and the ability of probabilistic forecasting will be developed. Based on the Bayesian theory and probabilistic forecasting model of precipitation, observational and T213 ensemble prediction data are used as the different priori information sources and experiments about precipitation in Guangzhou, Nanjing, Wuhan and Chengdu are carried out. Differences on the forecasts that are dependent on different priori informations are compared. Also influence of priori information on the Bayesian precipitation probabilistic forecast model is analyzed. And then the model is developed as well. Furthermore, experiment based on Bayesian precipitation probabilistic forecasting which is dependent on model priori information is conducted. Results show that the priori information got from the ensemble prediction data is better. While the priori precipitation amount is more, the precipitation from the forecasting of model is also more and vice versa. Meanwhile, priori information has a strong impact on the Bayesian precipitation probabilistic forecast model. If the precipitation amount is much more, Bayesian ensemble probabilistic forecasting model can produce much more accurate prediction of rainy days. If the precipitation amount is little, prediction of no rain or light rain from the model is better.
In the rainfall probabilistic forecasting, information from the end of the probability distribution function should be applied. Then better forecast about rain and the ability of probabilistic forecasting will be developed. Based on the Bayesian theory and probabilistic forecasting model of precipitation, observational and T213 ensemble prediction data are used as the different priori information sources and experiments about precipitation in Guangzhou, Nanjing, Wuhan and Chengdu are carried out. Differences on the forecasts that are dependent on different priori informations are compared. Also influence of priori information on the Bayesian precipitation probabilistic forecast model is analyzed. And then the model is developed as well. Furthermore, experiment based on Bayesian precipitation probabilistic forecasting which is dependent on model priori information is conducted. Results show that the priori information got from the ensemble prediction data is better. While the priori precipitation amount is more, the precipitation from the forecasting of model is also more and vice versa. Meanwhile, priori information has a strong impact on the Bayesian precipitation probabilistic forecast model. If the precipitation amount is much more, Bayesian ensemble probabilistic forecasting model can produce much more accurate prediction of rainy days. If the precipitation amount is little, prediction of no rain or light rain from the model is better.
2013, 39(10):1247-1256.
DOI: 10.7519/j.issn.1000-0526.2013.10.002
Abstract:
Based on East China regional mesoscale numerical forecast model system (Shanghai Meteorological Bureau WRF ADAS Rapid Refresh, SMB WARR), the time lag ensemble forecasting experiment with 7 ensemble members is conducted and routinely updated every hour with hourly output through 6 h forecast length. Evaluation of the hourly area rain of Shanghai from June 17 to September 30, 2011 shows that ensemble mean has better performance than any other members at light to heavy rain levels but worse performance than some members at rainstorm level. Meanwhile, the skill of the latest forecast is not the best and the light to heavy rain could be well forecasted 6 h in ahead. Furthermore, the probability forecast has an advantage over the ensemble mean, and has good directions for the happening of rain in the very short range, also the large (little) probability is more useful at light to moderate rain levels (heavy rain to rainstorm levels) especially the latest forecast.
Based on East China regional mesoscale numerical forecast model system (Shanghai Meteorological Bureau WRF ADAS Rapid Refresh, SMB WARR), the time lag ensemble forecasting experiment with 7 ensemble members is conducted and routinely updated every hour with hourly output through 6 h forecast length. Evaluation of the hourly area rain of Shanghai from June 17 to September 30, 2011 shows that ensemble mean has better performance than any other members at light to heavy rain levels but worse performance than some members at rainstorm level. Meanwhile, the skill of the latest forecast is not the best and the light to heavy rain could be well forecasted 6 h in ahead. Furthermore, the probability forecast has an advantage over the ensemble mean, and has good directions for the happening of rain in the very short range, also the large (little) probability is more useful at light to moderate rain levels (heavy rain to rainstorm levels) especially the latest forecast.
2013, 39(10):1257-1264.
DOI: 10.7519/j.issn.1000-0526.2013.10.003
Abstract:
By taking sounding and auto station data as “standard data”, both subjective and objective verifications are carried out on the initials and predictions of numerical prediction model GRAPES and WRF to reveal the two models’ initial value quality, dynamical frame performance and rain parameterization in Southwest China to some extent. The results show that the initial geopotential height, wind speed and direction of GRAPES are somewhat better than WRF. In the predicting stage, however, the height and temperature RMS (Root Mean Square error) of GRAPES increase much faster than WRF. Besides, GRAPES predicts the 500 hPa height in Southwest China to be lower systematically, while WRF predicts higher height in Southwest China in a relatively big probability. The verification on the sorted weather processes exhibits that GRAPES is superior to WRF in vortex and shear initial analysis. But in predicting stage, WRF performances remarkably better than GRAPES as WRF predicts vortex, shear and trough in a higher correct rate. The analysis of sorted rainfall displays that for both models, rainfall prediction in vortex process is more difficult than the trough process, especially to GRAPES, but for WRF, rainfall prediction in shear process is the most difficult. This conclusion is accorded with two models’ capability in sorted weather process, so the rainfall parameterization effects in the two models are similar.
By taking sounding and auto station data as “standard data”, both subjective and objective verifications are carried out on the initials and predictions of numerical prediction model GRAPES and WRF to reveal the two models’ initial value quality, dynamical frame performance and rain parameterization in Southwest China to some extent. The results show that the initial geopotential height, wind speed and direction of GRAPES are somewhat better than WRF. In the predicting stage, however, the height and temperature RMS (Root Mean Square error) of GRAPES increase much faster than WRF. Besides, GRAPES predicts the 500 hPa height in Southwest China to be lower systematically, while WRF predicts higher height in Southwest China in a relatively big probability. The verification on the sorted weather processes exhibits that GRAPES is superior to WRF in vortex and shear initial analysis. But in predicting stage, WRF performances remarkably better than GRAPES as WRF predicts vortex, shear and trough in a higher correct rate. The analysis of sorted rainfall displays that for both models, rainfall prediction in vortex process is more difficult than the trough process, especially to GRAPES, but for WRF, rainfall prediction in shear process is the most difficult. This conclusion is accorded with two models’ capability in sorted weather process, so the rainfall parameterization effects in the two models are similar.
2013, 39(10):1265-1274.
DOI: 10.7519/j.issn.1000-0526.2013.10.004
Abstract:
“Haikui” (No.1211) is an intensified typhoon, but the remarkable differences of its intensity determination were presented by CMA, RSMC Tokyo and JTWC. Cloud image analysis shows that “Haikui” is a severe typhoon with the TBB below -70℃ for a long period in offshore area. Radar data reveals its symmetrical structure, clear eye and enlarged scope obviously before and after its landing. Long time lasting gale is also detected by the coastal observation stations, including automatic stations and inner island stations. The gust with the intensity above 13 grades lasts for 26 hours during the period. The maximum wind speed is 46.9 m·s-1, 39.4 m·s-1 and 36.8 m·s-1 measured respectively at Dongji Station, Dachen Station and Shipu Station. The vertical wind shear difference is 7-8 m·s-1 under the height of 500 m. These ground based observations show that “Haikui” has matched the standard of severe typhoon, and the intensity determination by CMA is reliable accordingly. Therefore, it is concluded that the determination of typhoon grade should depend on not only the Dvorak technique, but also the ground based detection data.
“Haikui” (No.1211) is an intensified typhoon, but the remarkable differences of its intensity determination were presented by CMA, RSMC Tokyo and JTWC. Cloud image analysis shows that “Haikui” is a severe typhoon with the TBB below -70℃ for a long period in offshore area. Radar data reveals its symmetrical structure, clear eye and enlarged scope obviously before and after its landing. Long time lasting gale is also detected by the coastal observation stations, including automatic stations and inner island stations. The gust with the intensity above 13 grades lasts for 26 hours during the period. The maximum wind speed is 46.9 m·s-1, 39.4 m·s-1 and 36.8 m·s-1 measured respectively at Dongji Station, Dachen Station and Shipu Station. The vertical wind shear difference is 7-8 m·s-1 under the height of 500 m. These ground based observations show that “Haikui” has matched the standard of severe typhoon, and the intensity determination by CMA is reliable accordingly. Therefore, it is concluded that the determination of typhoon grade should depend on not only the Dvorak technique, but also the ground based detection data.
2013, 39(10):1275-1283.
DOI: 10.7519/j.issn.1000-0526.2013.10.005
Abstract:
Using the Doppler radar and AWS data, this paper comprehensively analyzed three gust front processes which took place in Jiangsu Province on 16 May, in Beijing Tianjin Hebei region on 9 June and in Hebei Province on 10 July 2012. It turned out that the thunderstorm high which is formed by the continuous subsiding cold air, is the immediate cause of the formation of gust front. In the formation process of thunderstorm high, on the one hand, cold subsiding air stacks rapidly and forms thunderstorm high in a narrow area; on the other hand, the new monomers constantly replace the old, thus, stable downdraft in the storm develops thunderstorm high. Under the high pressure, strong divergence airflow and ambient air form the gust front. Gust front moves forward and enhances with the movement and enhancement of the thunderstorm high, and gradually disappears when thunderstorm high weakens. The greater temperature gradient and pressure gradient are, the stronger instantaneous high winds and gust front become. Instantaneous high wind speed that gust front produces is not always proportional to the intensity values of narrow band echo. MARC can indicate the emergence of gust front about half an hour, and the longer the convergence maintains, the longer the gust front maintains.
Using the Doppler radar and AWS data, this paper comprehensively analyzed three gust front processes which took place in Jiangsu Province on 16 May, in Beijing Tianjin Hebei region on 9 June and in Hebei Province on 10 July 2012. It turned out that the thunderstorm high which is formed by the continuous subsiding cold air, is the immediate cause of the formation of gust front. In the formation process of thunderstorm high, on the one hand, cold subsiding air stacks rapidly and forms thunderstorm high in a narrow area; on the other hand, the new monomers constantly replace the old, thus, stable downdraft in the storm develops thunderstorm high. Under the high pressure, strong divergence airflow and ambient air form the gust front. Gust front moves forward and enhances with the movement and enhancement of the thunderstorm high, and gradually disappears when thunderstorm high weakens. The greater temperature gradient and pressure gradient are, the stronger instantaneous high winds and gust front become. Instantaneous high wind speed that gust front produces is not always proportional to the intensity values of narrow band echo. MARC can indicate the emergence of gust front about half an hour, and the longer the convergence maintains, the longer the gust front maintains.
2013, 39(10):1284-1292.
DOI: 10.7519/j.issn.1000-0526.2013.10.006
Abstract:
Based on the fog observation data during 24-27 December 2006 (advection radiation fog), NCEP NC reanalysis data (2.5°×2.5°) and GDAS global meteorological data (1°×1°), detailed trajectory analysis of the boundary layer characteristics and water vapor transport of the fog is investigated, combined with the weather condition, meteorological elements and physical quantity field. The results show that: (1) there is thick inversion layer, even multi layer inversion throughout the dense fog event. Temperatures of different inversion tops in the middle and high levels are 2-5℃ higher than the surface temperature. The thickness of inversion layer is more than 200 m, and it gets to 500 m at 08:00 BT 26 December, indicating the atmosphere is very stable and conducive to the convergence of water vapor before the fog forms. However, it is not favorable for the divergence of water vapor after the formation of fog, which helps the development and maintenance of the fog, causing the fog to last about 64 hours with dense fog (visibility <50 m) about 37 hours; (2) The divergence of water vapor flux in low level is negative in the advection fog event. The upper air has persistent moisture convergence and the strongest moisture convergence appears at 02:00 BT 25 December, being -30×10-7 g·s-1·cm-2·hPa-1. The accumulation of low level water vapor makes fog form and develop while the divergence of water vapor flux speeds up its dissipation. 〖JP2〗The long lasting advection radiation fog is mainly caused by the continuous water vapor convergence; (3) The water vapor path is from the coastal area in easten China to Nanjing. The water vapor is continuously supplied from sea during the fog event, with the water vapor flux maximum getting to 2 g·s-1·hPa-1·cm-1. The sufficient supply and supplementary of water vapor determines the duration of the fog.
Based on the fog observation data during 24-27 December 2006 (advection radiation fog), NCEP NC reanalysis data (2.5°×2.5°) and GDAS global meteorological data (1°×1°), detailed trajectory analysis of the boundary layer characteristics and water vapor transport of the fog is investigated, combined with the weather condition, meteorological elements and physical quantity field. The results show that: (1) there is thick inversion layer, even multi layer inversion throughout the dense fog event. Temperatures of different inversion tops in the middle and high levels are 2-5℃ higher than the surface temperature. The thickness of inversion layer is more than 200 m, and it gets to 500 m at 08:00 BT 26 December, indicating the atmosphere is very stable and conducive to the convergence of water vapor before the fog forms. However, it is not favorable for the divergence of water vapor after the formation of fog, which helps the development and maintenance of the fog, causing the fog to last about 64 hours with dense fog (visibility <50 m) about 37 hours; (2) The divergence of water vapor flux in low level is negative in the advection fog event. The upper air has persistent moisture convergence and the strongest moisture convergence appears at 02:00 BT 25 December, being -30×10-7 g·s-1·cm-2·hPa-1. The accumulation of low level water vapor makes fog form and develop while the divergence of water vapor flux speeds up its dissipation. 〖JP2〗The long lasting advection radiation fog is mainly caused by the continuous water vapor convergence; (3) The water vapor path is from the coastal area in easten China to Nanjing. The water vapor is continuously supplied from sea during the fog event, with the water vapor flux maximum getting to 2 g·s-1·hPa-1·cm-1. The sufficient supply and supplementary of water vapor determines the duration of the fog.
2013, 39(10):1293-1303.
DOI: 10.7519/j.issn.1000-0526.2013.10.007
Abstract:
This paper investigates the relationship between air pollutant concentrations and seven meteorological parameters (wind speed, stable energy, Froude number, atmospheric boundary layer height, potential temperature lapse rate, transport index and gradient Richardson number) based on the near ground air pollutant concentrations and the high temporal and spatial resolution meteorological data from the Weather Research and Forecast (WRF) model and develops a regression model for predicting ground level daily mean PM10 (particulate matter with aerodynamic diameter less than 10 μm) and NO2 (nitrogen dioxide) concentrations for urban Lanzhou. The results show that in urban Lanzhou, pollutant concentrations correlate better with atmospheric boundary layer height and potential temperature lapse rate, and the correlations between NO2 and meteorological parameters are better than that between PM10 and meteorological parameters. The developed regression model performs better for NO2 than for PM10. The fitting degree of the developed regression model is higher in urban area than that in rural area, leading to the better performance in urban area. The overall performance of the regression model is as good as widely used comprehensive air quality models. The method provides a scientific basis for urban air quality forecasting and air pollution study.
This paper investigates the relationship between air pollutant concentrations and seven meteorological parameters (wind speed, stable energy, Froude number, atmospheric boundary layer height, potential temperature lapse rate, transport index and gradient Richardson number) based on the near ground air pollutant concentrations and the high temporal and spatial resolution meteorological data from the Weather Research and Forecast (WRF) model and develops a regression model for predicting ground level daily mean PM10 (particulate matter with aerodynamic diameter less than 10 μm) and NO2 (nitrogen dioxide) concentrations for urban Lanzhou. The results show that in urban Lanzhou, pollutant concentrations correlate better with atmospheric boundary layer height and potential temperature lapse rate, and the correlations between NO2 and meteorological parameters are better than that between PM10 and meteorological parameters. The developed regression model performs better for NO2 than for PM10. The fitting degree of the developed regression model is higher in urban area than that in rural area, leading to the better performance in urban area. The overall performance of the regression model is as good as widely used comprehensive air quality models. The method provides a scientific basis for urban air quality forecasting and air pollution study.
2013, 39(10):1304-1313.
DOI: 10.7519/j.issn.1000-0526.2013.10.008
Abstract:
The surface meteorological station data, regional automatic station data, MODIS 1B data and Landsat7 ETM+ satellite remote sensing data are used to study urban heat island in Shijiazhuang area. Temperature and land surface temperature data are used to study the impact of the urbanization on urban heat island, the temporal and spatial distribution of the urban heat island, etc. The result showed that: (1) The urban heat island in Shijiazhuang is increasing year by year, sharing the synchronous tendency with urbanization; (2) Temperature and land surface temperature data at the same time are used to study the spatial distribution of the urban heat island, which shows that the days of summer and autumn, and the nights of whole year have remarkable urban heat island (UHI) effect, but the cool island phenomenon sometimes appears in the spring day and the winter day; (3) The night temperature and land surface temperature (LST) were both correlated, the correlation coefficient is 0.80; (4) Landsat7 ETM+ data are used to study the effect of the different land cover categories on UHI, we found that NDVI and LST are negatively correlated. The smaller NDVI is, the higher LST is, and their negative correlation coefficient R2 is 0.72.
The surface meteorological station data, regional automatic station data, MODIS 1B data and Landsat7 ETM+ satellite remote sensing data are used to study urban heat island in Shijiazhuang area. Temperature and land surface temperature data are used to study the impact of the urbanization on urban heat island, the temporal and spatial distribution of the urban heat island, etc. The result showed that: (1) The urban heat island in Shijiazhuang is increasing year by year, sharing the synchronous tendency with urbanization; (2) Temperature and land surface temperature data at the same time are used to study the spatial distribution of the urban heat island, which shows that the days of summer and autumn, and the nights of whole year have remarkable urban heat island (UHI) effect, but the cool island phenomenon sometimes appears in the spring day and the winter day; (3) The night temperature and land surface temperature (LST) were both correlated, the correlation coefficient is 0.80; (4) Landsat7 ETM+ data are used to study the effect of the different land cover categories on UHI, we found that NDVI and LST are negatively correlated. The smaller NDVI is, the higher LST is, and their negative correlation coefficient R2 is 0.72.
2013, 39(10):1314-1324.
DOI: 10.7519/j.issn.1000-0526.2013.10.009
Abstract:
The climatic characteristics and causes of hazy weather in Wuxi, Jiangsu Province, are analyzed based on surface observations obtained from Wuxi Meteorological Office from 1980 to 2011 and Wuxi Statistic Yearbook data from 1991 to 2011. The results show that the number of haze days in Wuxi is in an increasing trend, especially in the late 5 years. The haze days appear most in winter, followed by spring, autumn and summer in succession. The haze processes that last for 10 consecutive days all go through high pressure, the rear of high pressure moving to the sea and the ground inverted trough. The air masses in middle and low levels are seen sinking in the back trajectories simulation during 10 consecutive days of haze and the extremely haze events, and the areas the air masses pass have higher pollutant concentration. The key factor for haze events in 1990s is the dust emission in industrial pollution, and then since 2004 industrial waste gas and vehicle exhaust increase year by year, causing the haze days to increase as well.
The climatic characteristics and causes of hazy weather in Wuxi, Jiangsu Province, are analyzed based on surface observations obtained from Wuxi Meteorological Office from 1980 to 2011 and Wuxi Statistic Yearbook data from 1991 to 2011. The results show that the number of haze days in Wuxi is in an increasing trend, especially in the late 5 years. The haze days appear most in winter, followed by spring, autumn and summer in succession. The haze processes that last for 10 consecutive days all go through high pressure, the rear of high pressure moving to the sea and the ground inverted trough. The air masses in middle and low levels are seen sinking in the back trajectories simulation during 10 consecutive days of haze and the extremely haze events, and the areas the air masses pass have higher pollutant concentration. The key factor for haze events in 1990s is the dust emission in industrial pollution, and then since 2004 industrial waste gas and vehicle exhaust increase year by year, causing the haze days to increase as well.
2013, 39(10):1325-1330.
DOI: 10.7519/j.issn.1000-0526.2013.10.010
Abstract:
Floodarea is a joint product of Geomer GmbH, Heidelberg, Germany. It is a 2 D dynamic flood evolution model, established based on GIS raster. In order to study the evaluation method of risk precipitation in small valley of mountain areas, a case study was performed for Shangqing River Valley, which lies in Fujian Province. Hourly area precipitation of the valley is calculated by using Thiessen polygon method of GIS and according to the rainy days of meteorological observing station. Coefficient of runoff formation and surface hydraulic power roughness is calculated with GIS on the basis of landscape in the valley. Based on precipitation data and digital elevation model data of 1:10000, the flood process which happened on June 18, 2010 is simulated with the “Floodarea” model. The water depth and water velocity is adjusted by means of changing coefficient of runoff formation and surface hydraulic power roughness, according to the differences between actual water depth and simulated water depth. The results show that tested by the research data after the flood process, the maximum water depth and its time are simulated well for the Shangqing River Valley. So the risk precipitation of different water depth grades in the valley can be calculated according to the simulated data.
Floodarea is a joint product of Geomer GmbH, Heidelberg, Germany. It is a 2 D dynamic flood evolution model, established based on GIS raster. In order to study the evaluation method of risk precipitation in small valley of mountain areas, a case study was performed for Shangqing River Valley, which lies in Fujian Province. Hourly area precipitation of the valley is calculated by using Thiessen polygon method of GIS and according to the rainy days of meteorological observing station. Coefficient of runoff formation and surface hydraulic power roughness is calculated with GIS on the basis of landscape in the valley. Based on precipitation data and digital elevation model data of 1:10000, the flood process which happened on June 18, 2010 is simulated with the “Floodarea” model. The water depth and water velocity is adjusted by means of changing coefficient of runoff formation and surface hydraulic power roughness, according to the differences between actual water depth and simulated water depth. The results show that tested by the research data after the flood process, the maximum water depth and its time are simulated well for the Shangqing River Valley. So the risk precipitation of different water depth grades in the valley can be calculated according to the simulated data.
2013, 39(10):1331-1336.
DOI: 10.7519/j.issn.1000-0526.2013.10.011
Abstract:
Quality validation methods and validating process of FY 2 geostationary meteorological satellite sea surface temperature (SST) products are introduced. The validation of operational SST product of FY2E and SST retrieval algorithms of FY2F are given out. At present, compared with foreign satellite SST, the accuracy of FY2 SST is poorer because of various reasons, such as the error statistics method, the retrieval algorithm and the system design, etc. In situ SST validation and cross product SST validation have their own advantages. In situ SST validation can give an objective evaluation of FY2 SST product. Analysis SST field has the advantages of global coverage, good timeliness and a more uniform quality. The cross product SST validation by analysis SST field for FY2 SST can meet the need of timeliness, which can also provide relative quality information. The geostationary satellite SST product validation information can provide a reference for product development and related users.
Quality validation methods and validating process of FY 2 geostationary meteorological satellite sea surface temperature (SST) products are introduced. The validation of operational SST product of FY2E and SST retrieval algorithms of FY2F are given out. At present, compared with foreign satellite SST, the accuracy of FY2 SST is poorer because of various reasons, such as the error statistics method, the retrieval algorithm and the system design, etc. In situ SST validation and cross product SST validation have their own advantages. In situ SST validation can give an objective evaluation of FY2 SST product. Analysis SST field has the advantages of global coverage, good timeliness and a more uniform quality. The cross product SST validation by analysis SST field for FY2 SST can meet the need of timeliness, which can also provide relative quality information. The geostationary satellite SST product validation information can provide a reference for product development and related users.
2013, 39(10):1337-1343.
DOI: 10.7519/j.issn.1000-0526.2013.10.012
Abstract:
Using the PMFT method developed by Environment Canada and the metadata collected by National Meteorological Information Centre of China Meteorological Administration, the inhomogeneity test and corrections are carried out to the monthly geopotential height data of 123 radiosonde stations in China. The result shows that shifts of instruments, update of sounding systems and change of radiation correction method are the main causes for the inhomogeneity in the regional sounding geopotential height data in China. With the height increasing, both the number of the inhomogeneous stations in two observation time and the mean magnitude of correction increase significantly. The correction values are negative at all mandatory levels, which indicates the radiosonde geopotential height data in China is higher systematically. The raw monthly mean geopotential height series of the 123 radiosonde stations in the tropopause and the higher levels of troposphere present decreasing trends, after correction, the trends change to increasing trends. In the middle and lower levels of the troposphere, the increasing trend of the geopotential height becomes more obvious after the correction.
Using the PMFT method developed by Environment Canada and the metadata collected by National Meteorological Information Centre of China Meteorological Administration, the inhomogeneity test and corrections are carried out to the monthly geopotential height data of 123 radiosonde stations in China. The result shows that shifts of instruments, update of sounding systems and change of radiation correction method are the main causes for the inhomogeneity in the regional sounding geopotential height data in China. With the height increasing, both the number of the inhomogeneous stations in two observation time and the mean magnitude of correction increase significantly. The correction values are negative at all mandatory levels, which indicates the radiosonde geopotential height data in China is higher systematically. The raw monthly mean geopotential height series of the 123 radiosonde stations in the tropopause and the higher levels of troposphere present decreasing trends, after correction, the trends change to increasing trends. In the middle and lower levels of the troposphere, the increasing trend of the geopotential height becomes more obvious after the correction.
2013, 39(10):1344-1349.
DOI: 10.7519/j.issn.1000-0526.2013.10.013
Abstract:
Using the data observed by the new generation Doppler weather radar in 4 years, the moving characteristics of radar echo are analyzed. It is found that: (1) the echo moving speeds are between 10.0 km·h-1 to 95.0 km·h-1, and the peak value is 45.0-50.0 km·h-1. The echo moving speeds are different in different months. The radar echoes have larger movement speed in late spring (May) and early autumn (September). The echo moving directions are between 120° to 360°, of which 80.6% concentrates betweem 210°-315°, and the moving directions mainly point to southwest, west and northwest; (2) The echo motion characteristics in the precipitation process can be summarized as four types: simple linear type, composite linear type, complex moving type and other types. The proportions of these types are 69.6%, 19.4%, 25.2% and 4.7% respectively. These studies can provide references for the scheme design of weather modification and nowcasting services.
Using the data observed by the new generation Doppler weather radar in 4 years, the moving characteristics of radar echo are analyzed. It is found that: (1) the echo moving speeds are between 10.0 km·h-1 to 95.0 km·h-1, and the peak value is 45.0-50.0 km·h-1. The echo moving speeds are different in different months. The radar echoes have larger movement speed in late spring (May) and early autumn (September). The echo moving directions are between 120° to 360°, of which 80.6% concentrates betweem 210°-315°, and the moving directions mainly point to southwest, west and northwest; (2) The echo motion characteristics in the precipitation process can be summarized as four types: simple linear type, composite linear type, complex moving type and other types. The proportions of these types are 69.6%, 19.4%, 25.2% and 4.7% respectively. These studies can provide references for the scheme design of weather modification and nowcasting services.
2013, 39(10):1350-1358.
DOI: 10.7519/j.issn.1000-0526.2013.10.014
Abstract:
Operational positioning, track and intensity forecast error of tropical cyclones (TCs) over Northwest Pacific in 2012 are evaluated. The results show that the performance of TC positioning remains the same as that in the previous years, with an average error by all methods is 23.4 km. The average track forecast errors of domestic subjective methods are 94.3 km (24 h), 168.2 km (48 h) and 284.2 km (72 h). Compared with 2011, the performance of 24 h track forecast made by the National Meteorological Centre of CMA has made great progress in 2012. The average track forecast errors of global models are 96.8 km (24 h), 177.2 km (48 h), 283.6 km (72 h), 382.3 km (96 h) and 583.6 km (120 h), of which the performances of some numerical weather prediction (NWP) systems are approaching to the mean level of subjective forecasts, but the best subjective method still has the positive skill compared with any NWP method. In addition, through comparing the track errors of advanced NWP models in other countries the track forecast ability of regional NWPs in China still has a large gap. The average absolute intensity errors of four typhoon operational centers at 24 h, 48 h and 72 h are 4.11~4.63 m·s-1, 6.10~6.90 m·s-1 and 6.84~8.71 m·s-1, respectively. There is always a systematic bias in some objective intensity forecast methods. These methods have predicted well for the 24 h landfall location of “Haikui”, but not so good for “Saola”.
Operational positioning, track and intensity forecast error of tropical cyclones (TCs) over Northwest Pacific in 2012 are evaluated. The results show that the performance of TC positioning remains the same as that in the previous years, with an average error by all methods is 23.4 km. The average track forecast errors of domestic subjective methods are 94.3 km (24 h), 168.2 km (48 h) and 284.2 km (72 h). Compared with 2011, the performance of 24 h track forecast made by the National Meteorological Centre of CMA has made great progress in 2012. The average track forecast errors of global models are 96.8 km (24 h), 177.2 km (48 h), 283.6 km (72 h), 382.3 km (96 h) and 583.6 km (120 h), of which the performances of some numerical weather prediction (NWP) systems are approaching to the mean level of subjective forecasts, but the best subjective method still has the positive skill compared with any NWP method. In addition, through comparing the track errors of advanced NWP models in other countries the track forecast ability of regional NWPs in China still has a large gap. The average absolute intensity errors of four typhoon operational centers at 24 h, 48 h and 72 h are 4.11~4.63 m·s-1, 6.10~6.90 m·s-1 and 6.84~8.71 m·s-1, respectively. There is always a systematic bias in some objective intensity forecast methods. These methods have predicted well for the 24 h landfall location of “Haikui”, but not so good for “Saola”.
2013, 39(10):1359-1368.
DOI: 10.7519/j.issn.1000-0526.2013.10.015
Abstract:
The physical effects assessment provides physical basis for the artificial precipitation test, so it has got more and more attentions. Based on the aircraft operations information in Zhangjiakou on May 1, 2009, this paper tries to find the contrast area from different heights to conduct the physical examination of the operational effects. The results show that: Making use of reduction to absurdity, the FSSP (range one) measurements of droplets are found to be dominated by ice phase and liquid phase when it is -10℃, and the rapidly growing moment of concentration of the particles is relatively consistent with the rapidly growing of the ice phase cloud particles. The actual results of observation are basically in agreement with cold cloud catalytic principle, and the enlargement of rainfall area has proved that this aircraft cloud seeding is effective to a certain extent.
The physical effects assessment provides physical basis for the artificial precipitation test, so it has got more and more attentions. Based on the aircraft operations information in Zhangjiakou on May 1, 2009, this paper tries to find the contrast area from different heights to conduct the physical examination of the operational effects. The results show that: Making use of reduction to absurdity, the FSSP (range one) measurements of droplets are found to be dominated by ice phase and liquid phase when it is -10℃, and the rapidly growing moment of concentration of the particles is relatively consistent with the rapidly growing of the ice phase cloud particles. The actual results of observation are basically in agreement with cold cloud catalytic principle, and the enlargement of rainfall area has proved that this aircraft cloud seeding is effective to a certain extent.
2013, 39(10):1369-1373.
DOI: 10.7519/j.issn.1000-0526.2013.10.016
Abstract:
Using the method of disaster risk assessment, this paper analyzes the disaster causing factors and hazard bearing body fragility of drought in Guilin and conducts comprehensive evaluations on drought disaster as well. The assessment result is that the southeast of Guilin is the high risk area of drought while the northwest is the low risk area. According to the drought risk assessment conclusions, the study on artificial precipitation is made. Due to the difference of altitude and thickness of minus temperature zone of precipitation clouds in difference seasons, the pattern of artificial precipitation operation may be divided into two, one for summer and autumn and the other for winter and spring. The general goal is to sow AgI Ice nucleus into the minus temperature area of rainfall clouds, catalyze the cloud and increase the surface precipitation.
Using the method of disaster risk assessment, this paper analyzes the disaster causing factors and hazard bearing body fragility of drought in Guilin and conducts comprehensive evaluations on drought disaster as well. The assessment result is that the southeast of Guilin is the high risk area of drought while the northwest is the low risk area. According to the drought risk assessment conclusions, the study on artificial precipitation is made. Due to the difference of altitude and thickness of minus temperature zone of precipitation clouds in difference seasons, the pattern of artificial precipitation operation may be divided into two, one for summer and autumn and the other for winter and spring. The general goal is to sow AgI Ice nucleus into the minus temperature area of rainfall clouds, catalyze the cloud and increase the surface precipitation.
2013, 39(10):1374-1378.
DOI: 10.7519/j.issn.1000-0526.2013.10.017
Abstract:
During the spring of 2013, the surface air temperature was 1℃ higher than normal and the average precipitation was 8.3% more than normal in China. However, obvious spatial and temporal inhomogeneity was observed in both temperature and precipitation with severe cold weathers persisting in Northeast China and regional drought occurring in North China. Long persistent negative phase of Arctic Oscillation (AO), active cold vortexes and more extensive than normal snow cover over the Northeast China caused the sustained low temperature in this region. And, weaker than normal Siberian high, anomalous high ridge and inadequate water vapor transport may be the primary causes for the drought in North China.
During the spring of 2013, the surface air temperature was 1℃ higher than normal and the average precipitation was 8.3% more than normal in China. However, obvious spatial and temporal inhomogeneity was observed in both temperature and precipitation with severe cold weathers persisting in Northeast China and regional drought occurring in North China. Long persistent negative phase of Arctic Oscillation (AO), active cold vortexes and more extensive than normal snow cover over the Northeast China caused the sustained low temperature in this region. And, weaker than normal Siberian high, anomalous high ridge and inadequate water vapor transport may be the primary causes for the drought in North China.
2013, 39(10):1379-1384.
DOI: 10.7519/j.issn.1000-0526.2013.10.018
Abstract:
The main characteristics of the general atmospheric circulation in July 2013 are as follows: the circulation presented an unusual pattern of higher pressure in the east and lower pressure in the west over Eurasia and the upper troughs were active. The northwestern Pacific subtropical high was stronger than normal. The monthly mean precipitation amount was 138.9 mm, which is 15.2% more than normal (120.6 mm). The monthly mean temperature was 22.4℃, being 0.5℃ higher than normal. There were 11 heavy rainfall processes with extreme precipitation records observed at some stations. Four tropical cyclones appeared over the South China Sea and the northwestern Pacific Ocean with three of them landed on China. Long lasting high temperature weather occurred in south and southwest of China while extreme high temperature events happened at 100 meteorological observing stations.
The main characteristics of the general atmospheric circulation in July 2013 are as follows: the circulation presented an unusual pattern of higher pressure in the east and lower pressure in the west over Eurasia and the upper troughs were active. The northwestern Pacific subtropical high was stronger than normal. The monthly mean precipitation amount was 138.9 mm, which is 15.2% more than normal (120.6 mm). The monthly mean temperature was 22.4℃, being 0.5℃ higher than normal. There were 11 heavy rainfall processes with extreme precipitation records observed at some stations. Four tropical cyclones appeared over the South China Sea and the northwestern Pacific Ocean with three of them landed on China. Long lasting high temperature weather occurred in south and southwest of China while extreme high temperature events happened at 100 meteorological observing stations.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P