ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 4,2013 Table of Contents
2013, 39(4):401-409.
DOI: 10.7519/j.issn.1000-0526.2013.04.001
Abstract:
Quasi geostrophic theory is the core of atmospheric dynamics, providing a method of analyzing the evolution of large scale weather systems according to the basic principles of atmospheric dynamics. This theory can help forecasters understand the 3D structures of large scale weather systems in the middle and hight latitudes, analyze and predict the development and movement of weather systems, so it is taken as the theoretic foundation of short term weather forecasts. The theory has complete theoretic system but involves some approximations that are prone to misunderstanding some of its basic problems. Proceeding from basic dynamic knowledge this paper reviews and discusses the basic concepts, basic approximations, the kernel theory of the quasi geostrophic theory and its application to the forecasting processes. The contents include definitions of the quasi geostrophic motion and quasi geostrophic approximations, the scope of the quasi geostrophic motion theory, the large scale motion in synoptic charts, correlations between the quasi geostrophic motion theory and short term weather forecasting, judgment of the development and movement of upper troughs and ridges as well as surface cyclones by the quasi geostrophic theory in baroclinic two layer model, etc.
Quasi geostrophic theory is the core of atmospheric dynamics, providing a method of analyzing the evolution of large scale weather systems according to the basic principles of atmospheric dynamics. This theory can help forecasters understand the 3D structures of large scale weather systems in the middle and hight latitudes, analyze and predict the development and movement of weather systems, so it is taken as the theoretic foundation of short term weather forecasts. The theory has complete theoretic system but involves some approximations that are prone to misunderstanding some of its basic problems. Proceeding from basic dynamic knowledge this paper reviews and discusses the basic concepts, basic approximations, the kernel theory of the quasi geostrophic theory and its application to the forecasting processes. The contents include definitions of the quasi geostrophic motion and quasi geostrophic approximations, the scope of the quasi geostrophic motion theory, the large scale motion in synoptic charts, correlations between the quasi geostrophic motion theory and short term weather forecasting, judgment of the development and movement of upper troughs and ridges as well as surface cyclones by the quasi geostrophic theory in baroclinic two layer model, etc.
2013, 39(4):410-417.
DOI: 10.7519/j.issn.1000-0526.2013.04.002
Abstract:
South China (SC) suffered a rarely seen elevated thunderstorm on 27 February 2012. Based on meteorological observation data, Doppler weather radar data and NCEP/NCAR analysis data, the characteristics and causes of the elevated thunderstorm are analyzed. The results show that this convective weather with short time heavy rain, hail and thunderstorm which occurred behind a cold front was a typical elevated thunderstorm. There was a low level temperature inversion over SC, the atmospheric layer near surface was stable and the location of the convective weather was correlated well with the 850 hPa shear line. The east southward propagation of westerly trough and the southward movement of westerly jet in the mid high level together with reinforce of the 850 hPa low level moist southerly on the southern side of the Nanling Mountains created favorable atmospheric circulation conditions for development of the elevated convection. The conditional symmetric instability of the air over SC and the convective uplift mechanism of warm air including southward movement of cold air in boundary layer and upper level divergence contributed to the “elevated convection” weather. Different from the general thunderstorm that develops from the surface, the warm and moist air for this elevated thunderstorm began to lift convectively from the layer near 850 hPa which was above the temperature inversion, not beginning from the boundary layer.
South China (SC) suffered a rarely seen elevated thunderstorm on 27 February 2012. Based on meteorological observation data, Doppler weather radar data and NCEP/NCAR analysis data, the characteristics and causes of the elevated thunderstorm are analyzed. The results show that this convective weather with short time heavy rain, hail and thunderstorm which occurred behind a cold front was a typical elevated thunderstorm. There was a low level temperature inversion over SC, the atmospheric layer near surface was stable and the location of the convective weather was correlated well with the 850 hPa shear line. The east southward propagation of westerly trough and the southward movement of westerly jet in the mid high level together with reinforce of the 850 hPa low level moist southerly on the southern side of the Nanling Mountains created favorable atmospheric circulation conditions for development of the elevated convection. The conditional symmetric instability of the air over SC and the convective uplift mechanism of warm air including southward movement of cold air in boundary layer and upper level divergence contributed to the “elevated convection” weather. Different from the general thunderstorm that develops from the surface, the warm and moist air for this elevated thunderstorm began to lift convectively from the layer near 850 hPa which was above the temperature inversion, not beginning from the boundary layer.
2013, 39(4):418-426.
DOI: 10.7519/j.issn.1000-0526.2013.04.003
Abstract:
Using “the Northwest Pacific Tropical Cyclone Retrieval Yearbook System” data, NCEP/NCAR reanalysis data and Yunnan precipitation data, westbound landing tropical cyclones (TC) impacting the rainfall process of Yunnan during 1959-2007 are classified and analyzed in this paper.The results show that there are four types of circulation pattern including TC low circulation pattern, TC low outer circulation or inverted trough pattern, TC interacting with the two high convergence pattern, and TC low pressure interacting with trough cold air pattern. The ambient field characteristics show that when 100 hPa high pressure in South Asia is positioned to the west of 90°E, the strong divergence zone offered by the upper level easterly jet enhances the joining of the low level southwest monsoon flow with the TC circulation, and the difference of high and low level vorticities distributes negatively, making the TC low circulation maintained on land or slowing down the weakening. Abundant energy and moisture are provided for the rainstorms in Yunnan by the low level jet of southwest monsoon, subtropical high as well as the south low level jet accompanying TC. Severe precipitation often occurs on the left side of low level jet， near positive vorticity center of TC low or inverted trough. The atmospheric baroclinic instability increases with the advection of cold airs entering Yunnan, causing the enhancement of precipitation in the outer part of tropical cyclones.
Using “the Northwest Pacific Tropical Cyclone Retrieval Yearbook System” data, NCEP/NCAR reanalysis data and Yunnan precipitation data, westbound landing tropical cyclones (TC) impacting the rainfall process of Yunnan during 1959-2007 are classified and analyzed in this paper.The results show that there are four types of circulation pattern including TC low circulation pattern, TC low outer circulation or inverted trough pattern, TC interacting with the two high convergence pattern, and TC low pressure interacting with trough cold air pattern. The ambient field characteristics show that when 100 hPa high pressure in South Asia is positioned to the west of 90°E, the strong divergence zone offered by the upper level easterly jet enhances the joining of the low level southwest monsoon flow with the TC circulation, and the difference of high and low level vorticities distributes negatively, making the TC low circulation maintained on land or slowing down the weakening. Abundant energy and moisture are provided for the rainstorms in Yunnan by the low level jet of southwest monsoon, subtropical high as well as the south low level jet accompanying TC. Severe precipitation often occurs on the left side of low level jet， near positive vorticity center of TC low or inverted trough. The atmospheric baroclinic instability increases with the advection of cold airs entering Yunnan, causing the enhancement of precipitation in the outer part of tropical cyclones.
2013, 39(4):427-435.
DOI: 10.7519/j.issn.1000-0526.2013.04.004
Abstract:
By working on the relations between the typhoons seen in the region of 15°-35°N and 103°-130°E from May to September, 2000-2010 and the daily precipitation amount in Sichuan in the corresponding period, this paper points out the typhoon tracks most closely related to the recorded torrential rains in Sichuan were the west track, shift track and northwest track. Comparing the ambient field of clearly seen heavy rains and not clearly seen heavy rains under the background of similar typhoon tracks, it is found that the westerlies trough was active to the north of 40°N, a high ridge was in the Central Asian region, the high pressure over the mid latitude continent controlled the area from eastern Tibetan Plateau to much of Sichuan or in the central and eastern part of China was a broad trough, which shows an unfavorable ambient field for the occurrence of obvious torrential rains in Sichuan. However, over the area between Balkhash Lake and Baikal Lake there was a broad low trough, subtropical fronts were dense and reached the area around 36°N, the mid latitude ribbon ridge line was found over the area to the south of 30°N, and moreover, the mid high latitudes in China presented a posture of east high and west low and the meridional baroclinic trough in West China was the ambient field, favorable for the breakout of rainstorms in Sichuan. The analysis results suggest that the impact of typhoons on the weather in Sichuan mainly include three aspects: the first is the indirect influence through affecting subtropical high, the second is the direct influence of the circulation in the outer area of low pressure of typhoon, and the third is that typhoon plays the role of a carrier to convey the warm and moist air to Sichuan region, interacting with the low value systems in mid high latitudes and subtropical high.
By working on the relations between the typhoons seen in the region of 15°-35°N and 103°-130°E from May to September, 2000-2010 and the daily precipitation amount in Sichuan in the corresponding period, this paper points out the typhoon tracks most closely related to the recorded torrential rains in Sichuan were the west track, shift track and northwest track. Comparing the ambient field of clearly seen heavy rains and not clearly seen heavy rains under the background of similar typhoon tracks, it is found that the westerlies trough was active to the north of 40°N, a high ridge was in the Central Asian region, the high pressure over the mid latitude continent controlled the area from eastern Tibetan Plateau to much of Sichuan or in the central and eastern part of China was a broad trough, which shows an unfavorable ambient field for the occurrence of obvious torrential rains in Sichuan. However, over the area between Balkhash Lake and Baikal Lake there was a broad low trough, subtropical fronts were dense and reached the area around 36°N, the mid latitude ribbon ridge line was found over the area to the south of 30°N, and moreover, the mid high latitudes in China presented a posture of east high and west low and the meridional baroclinic trough in West China was the ambient field, favorable for the breakout of rainstorms in Sichuan. The analysis results suggest that the impact of typhoons on the weather in Sichuan mainly include three aspects: the first is the indirect influence through affecting subtropical high, the second is the direct influence of the circulation in the outer area of low pressure of typhoon, and the third is that typhoon plays the role of a carrier to convey the warm and moist air to Sichuan region, interacting with the low value systems in mid high latitudes and subtropical high.
2013, 39(4):436-442.
DOI: 10.7519/j.issn.1000-0526.2013.04.005
Abstract:
On the basis of the climatic and water resource records in the recent 50 years (1961-2010) over the Erhai Lake Basin, the climatic characteristics and the impact on water resources by different climate types are analyzed, and the relationship between water resources and basin rainfall, temperature are addressed to quantitatively estimate the water resources of Erhai Lake. The results suggest that the temperature of the Erhai Lake Basin in the 50 years shows an increasing tendency with fluctuation and climate is warming obviously. The first decade of the 21st century is the warmest in the recent 50 years in the Erhai Lake Basin. The annual rainfall shows a tendency to decrease in general. The water resources of Erhai Lake have a remarkable positive correlation with the annual rainfall, but significantly negative with temperature. The climate was mainly cold and wet in the 1960s and 1970s in the Erhai Lake Basin, but getting warm after into 1980s and especially warm and dry in the first decade into the 21st century. The Erhai Lake water resources are in dry year when it is warm dry year, but in humid year when cold wet, and in normal year when the climate is normal. According to the prediction of future climate in Erhai Lake Basin and through the climatic type calculated by regression equation of climate forecast, the water resources can be estimated qualitatively and forecasted quantitatively whether it is dry year or humid year.
On the basis of the climatic and water resource records in the recent 50 years (1961-2010) over the Erhai Lake Basin, the climatic characteristics and the impact on water resources by different climate types are analyzed, and the relationship between water resources and basin rainfall, temperature are addressed to quantitatively estimate the water resources of Erhai Lake. The results suggest that the temperature of the Erhai Lake Basin in the 50 years shows an increasing tendency with fluctuation and climate is warming obviously. The first decade of the 21st century is the warmest in the recent 50 years in the Erhai Lake Basin. The annual rainfall shows a tendency to decrease in general. The water resources of Erhai Lake have a remarkable positive correlation with the annual rainfall, but significantly negative with temperature. The climate was mainly cold and wet in the 1960s and 1970s in the Erhai Lake Basin, but getting warm after into 1980s and especially warm and dry in the first decade into the 21st century. The Erhai Lake water resources are in dry year when it is warm dry year, but in humid year when cold wet, and in normal year when the climate is normal. According to the prediction of future climate in Erhai Lake Basin and through the climatic type calculated by regression equation of climate forecast, the water resources can be estimated qualitatively and forecasted quantitatively whether it is dry year or humid year.
2013, 39(4):443-452.
DOI: 10.7519/j.issn.1000-0526.2013.04.006
Abstract:
Based on the daily sunshine hours data of 9 meteorological stations and daily solar radiation data of Urumqi Meteorological Station from 1961 to 2010 in Urumqi, Xinjiang, the monthly solar radiation of spring, summer, autumn, winter and year from 1961 to 2010 of each meteorological station was estimated by using of climatic methods, and the fundamental spatial temporal change trends of spring, summer, autumn, winter and annual sunshine hours and solar radiation were analyzed by using of linear trend, Mann Kendall test and three dimensional and quadratic trend surface simulation and inverse distance squared weighting residual error revision based on GIS. The main results show that spring, summer, autumn and annual sunshine hours and solar radiation in Urumqi are more in plain and valley areas than in Tianshan Mountain areas, but winter sunshine hours and solar radiation are more in Tianshan Mountain areas than in plain and valley areas. The variation trends of spring, summer sunshine hours and solar radiation are not so obvious, but sunshine hours and solar radiation of autumn, winter and year have significantly decreased in recent 50 years, and they had abrupt decrease in 1981 and 1991 respectively. And before and after the sudden change, the autumn, winter and annual sunshine hours and solar radiation had distinct regional differences. In general, the decrease range of sunshine hours and solar radiation shows the characteristics of “more in plain, but less in mountain areas”.
Based on the daily sunshine hours data of 9 meteorological stations and daily solar radiation data of Urumqi Meteorological Station from 1961 to 2010 in Urumqi, Xinjiang, the monthly solar radiation of spring, summer, autumn, winter and year from 1961 to 2010 of each meteorological station was estimated by using of climatic methods, and the fundamental spatial temporal change trends of spring, summer, autumn, winter and annual sunshine hours and solar radiation were analyzed by using of linear trend, Mann Kendall test and three dimensional and quadratic trend surface simulation and inverse distance squared weighting residual error revision based on GIS. The main results show that spring, summer, autumn and annual sunshine hours and solar radiation in Urumqi are more in plain and valley areas than in Tianshan Mountain areas, but winter sunshine hours and solar radiation are more in Tianshan Mountain areas than in plain and valley areas. The variation trends of spring, summer sunshine hours and solar radiation are not so obvious, but sunshine hours and solar radiation of autumn, winter and year have significantly decreased in recent 50 years, and they had abrupt decrease in 1981 and 1991 respectively. And before and after the sudden change, the autumn, winter and annual sunshine hours and solar radiation had distinct regional differences. In general, the decrease range of sunshine hours and solar radiation shows the characteristics of “more in plain, but less in mountain areas”.
2013, 39(4):453-459.
DOI: 10.7519/j.issn.1000-0526.2013.04.007
Abstract:
The observation data of visibility and relative humility during 2005-2010 from 9 weather stations located in Xiamen, Tong’an, Zhangzhou, Dongshan, Zhangpu, Longhai, Zhao’an, Jinjiang and Chongwu were used to analyze the annual, seasonal and daily variation characteristics of low visibility events seen in the coastal region of southern Fujian Province with the statistical method. Through comparative analyses, it was found that the annual average low visibility was about 6 km and the visibility was better when haze occurred than when mist or fog occurred. During the first half of the year, low visibility lasted for a longer time and the frequency was high. On the contrary, during the second half of the year, low visibility lasted shorter and the frequency was low. Usually, the visibility at 08:00 was the lowest and improved at 14:00 and 20:00. The visibility at 02:00 was better than at 08:00. But Dongshan and Chongwu had poorer visibility at 02:00 than at 08:00 in winter and spring. It is concluded that haze is the primary reason that causes the low visibility events in coastal areas in southern Fujian and the mist is the second reason. All the above reveals that the rapid developing economy in this region has significant impacts on the atmospheric visibility.
The observation data of visibility and relative humility during 2005-2010 from 9 weather stations located in Xiamen, Tong’an, Zhangzhou, Dongshan, Zhangpu, Longhai, Zhao’an, Jinjiang and Chongwu were used to analyze the annual, seasonal and daily variation characteristics of low visibility events seen in the coastal region of southern Fujian Province with the statistical method. Through comparative analyses, it was found that the annual average low visibility was about 6 km and the visibility was better when haze occurred than when mist or fog occurred. During the first half of the year, low visibility lasted for a longer time and the frequency was high. On the contrary, during the second half of the year, low visibility lasted shorter and the frequency was low. Usually, the visibility at 08:00 was the lowest and improved at 14:00 and 20:00. The visibility at 02:00 was better than at 08:00. But Dongshan and Chongwu had poorer visibility at 02:00 than at 08:00 in winter and spring. It is concluded that haze is the primary reason that causes the low visibility events in coastal areas in southern Fujian and the mist is the second reason. All the above reveals that the rapid developing economy in this region has significant impacts on the atmospheric visibility.
8 Product Interpretation of Refined Hourly Temperature Based on the Assimilation of WRF Model in LAPS
2013, 39(4):460-465.
DOI: 10.7519/j.issn.1000-0526.2013.04.008
Abstract:
Based on the assimilation of refined WRF model products in Local Analysis and Prediction System (LAPS), in order to meet the needs of the power system temperature forecast, several product interpretation forecast methods of hourly temperature were designed in Hubei Province and surrounding stations from 1 April to 20 July 2011. Compared with other several forecast models, results show that the WRF model has a good simulation of temperature trend, the temperature forecast accuracy score is around 50%, the forecast error in the daytime of 08-20 BT is less than that in the nighttimes, the accuracy score of maximum temperature is 54% and the accuracy score of minimum temperature is 44%. The forecast accuracy can be further improved through product interpretation of model output, so that the accuracy score reached to 60%-70%, that of maximum temperature got 57% and that of minimum temperature reached 74%. In addition, the MOS equation established hourly time can effectively reduce the forecast errors in nighttime of 20-07 BT. Furthermore, bringing maximum temperature factor into Kalman system equations can be further improved forecast accuracy.
Based on the assimilation of refined WRF model products in Local Analysis and Prediction System (LAPS), in order to meet the needs of the power system temperature forecast, several product interpretation forecast methods of hourly temperature were designed in Hubei Province and surrounding stations from 1 April to 20 July 2011. Compared with other several forecast models, results show that the WRF model has a good simulation of temperature trend, the temperature forecast accuracy score is around 50%, the forecast error in the daytime of 08-20 BT is less than that in the nighttimes, the accuracy score of maximum temperature is 54% and the accuracy score of minimum temperature is 44%. The forecast accuracy can be further improved through product interpretation of model output, so that the accuracy score reached to 60%-70%, that of maximum temperature got 57% and that of minimum temperature reached 74%. In addition, the MOS equation established hourly time can effectively reduce the forecast errors in nighttime of 20-07 BT. Furthermore, bringing maximum temperature factor into Kalman system equations can be further improved forecast accuracy.
XU Zhifang
,
HAO Min
,
ZHU Lijuan
,
GONG Jiandong
,
WAN Qilin
,
TAO Shiwei
,
XUE Jishan
,
CHEN Dehui
2013, 39(4):466-477.
DOI: 10.7519/j.issn.1000-0526.2013.04.009
Abstract:
The GRAPES_RAFS (Rapid Analysis and Forecast System) is based on GRAPES (Global and Regional Assimilation and Prediction System) model and GRAPES_3DVAR system, running on a high intermittent assimilation cycle to provide high resolution mesoscale analyses and short time numerical weather predication guidance for weather forecasting. The GRAPES_RAFS assimilates radiosonde observation and a lot of observations with high temporal and spatial resolution, such as aircraft, VAD wind profiles, surface station observation data, et al. Herein, the framework and flowchart of GRAPES_RAFS are technically described, and compared with the forecasting products of GRAPES_MESO, the short time nowcasting capability of this system and the critical techniques influencing its forecasting performance are also discussed. The research results show that the GRAPES_RAFS system is effective in providing more accurate short time nowcasting forecasts initialized with recent data than GRAPES_MESO system forecasts. The results also show that, 〖JP2〗high resolution observations, the background error covariance of GRAPES_3DVAR system,〖JP〗 the dynamical framework and physical processes of GRAPES model are keys to GRAPES_RAFS. The short time nowcasting performance of GRAPES_RAFS is a challenging task in the case that the assimilated observation data for GRAPES_RAFS are sparse.
The GRAPES_RAFS (Rapid Analysis and Forecast System) is based on GRAPES (Global and Regional Assimilation and Prediction System) model and GRAPES_3DVAR system, running on a high intermittent assimilation cycle to provide high resolution mesoscale analyses and short time numerical weather predication guidance for weather forecasting. The GRAPES_RAFS assimilates radiosonde observation and a lot of observations with high temporal and spatial resolution, such as aircraft, VAD wind profiles, surface station observation data, et al. Herein, the framework and flowchart of GRAPES_RAFS are technically described, and compared with the forecasting products of GRAPES_MESO, the short time nowcasting capability of this system and the critical techniques influencing its forecasting performance are also discussed. The research results show that the GRAPES_RAFS system is effective in providing more accurate short time nowcasting forecasts initialized with recent data than GRAPES_MESO system forecasts. The results also show that, 〖JP2〗high resolution observations, the background error covariance of GRAPES_3DVAR system,〖JP〗 the dynamical framework and physical processes of GRAPES model are keys to GRAPES_RAFS. The short time nowcasting performance of GRAPES_RAFS is a challenging task in the case that the assimilated observation data for GRAPES_RAFS are sparse.
2013, 39(4):478-485.
DOI: 10.7519/j.issn.1000-0526.2013.04.010
Abstract:
Based on the principle that the reflectivity at a water (or ice) absorbing band primarily depends on cloud particle size, the comparison of effective particle radius of water cloud is made, retrieved from the data of channel 3 (3.7 μm) of FY 3A Visible and Infrared Radiometer (VIRR) and the data of channel 6 (1.64 μm) and channel 7 (2.13 μm) of FY 3A Medium Resolution Spectral Imager (MERSI) using SBDART radiation transfer mode. The results show that the effective particle radius can be quantitatively retrieved by any of the three channels of 1.64, 2.13 and 3.7 μm. The reflectivity of channel 1.64 and 2.13 μm is more sensitive to the larger particles while channel 3.7 μm shows better sensitivity when optical thickness is smaller. The retrieve product of effective particle radius of the three channels have better correlations with the effective particle radius products of MODIS.
Based on the principle that the reflectivity at a water (or ice) absorbing band primarily depends on cloud particle size, the comparison of effective particle radius of water cloud is made, retrieved from the data of channel 3 (3.7 μm) of FY 3A Visible and Infrared Radiometer (VIRR) and the data of channel 6 (1.64 μm) and channel 7 (2.13 μm) of FY 3A Medium Resolution Spectral Imager (MERSI) using SBDART radiation transfer mode. The results show that the effective particle radius can be quantitatively retrieved by any of the three channels of 1.64, 2.13 and 3.7 μm. The reflectivity of channel 1.64 and 2.13 μm is more sensitive to the larger particles while channel 3.7 μm shows better sensitivity when optical thickness is smaller. The retrieve product of effective particle radius of the three channels have better correlations with the effective particle radius products of MODIS.
2013, 39(4):486-493.
DOI: 10.7519/j.issn.1000-0526.2013.04.011
Abstract:
Based on daily precipitation data of 2200 observation stations over China in 2009, precipitation at grid point is estimated by the method of moving window ordinary kriging and three technical experiments are designed in this article. The interpolation errors are compared between the overall search method and direction neighborhood method in the moving window ordinary kriging. The different effects of maximum influence radius and shielding on the interpolation error are also discussed. The sample point selection strategy of the direction neighborhood method is put forward to sort data points. The results show that compared with the overall search method for the traditional moving window ordinary kriging (MWK), direction neighborhood method has the notable advantages of more computational efficiency and high accuracy especially in the areas with dense sites. The results also show that good interpolation effect can be attained within the range from 4° to 5° meridional (zonal) arc length for most areas; and the shielding effect of precipitation is weak. Further more, better accuracy for precipitation estimation is presented when the ε value is equal to 0.1, but it is likely to get worse with the increase of ε value.
Based on daily precipitation data of 2200 observation stations over China in 2009, precipitation at grid point is estimated by the method of moving window ordinary kriging and three technical experiments are designed in this article. The interpolation errors are compared between the overall search method and direction neighborhood method in the moving window ordinary kriging. The different effects of maximum influence radius and shielding on the interpolation error are also discussed. The sample point selection strategy of the direction neighborhood method is put forward to sort data points. The results show that compared with the overall search method for the traditional moving window ordinary kriging (MWK), direction neighborhood method has the notable advantages of more computational efficiency and high accuracy especially in the areas with dense sites. The results also show that good interpolation effect can be attained within the range from 4° to 5° meridional (zonal) arc length for most areas; and the shielding effect of precipitation is weak. Further more, better accuracy for precipitation estimation is presented when the ε value is equal to 0.1, but it is likely to get worse with the increase of ε value.
2013, 39(4):494-499.
DOI: 10.7519/j.issn.1000-0526.2013.04.012
Abstract:
In order to improve China New Generation Weather Radar (CINRAD) low level detection performance and accuracy of the wind storm top height, this paper studies and designs a volume coverage pattern (VCP) for CINRAD using SRTM geographic information data. It aims to improve CINRAD detection ability in lower layers by adding the number of elevation angles in lower and middle layers as well as negative elevation angles. We took Fuzhou and Longyan radar as examples to compute elevation angles for precipitation mode, and derived their new observation mode VCP12. Observation experiment results show that radar detection ability in the lower atmosphere can be improved after low or negative elevation angles are added.
In order to improve China New Generation Weather Radar (CINRAD) low level detection performance and accuracy of the wind storm top height, this paper studies and designs a volume coverage pattern (VCP) for CINRAD using SRTM geographic information data. It aims to improve CINRAD detection ability in lower layers by adding the number of elevation angles in lower and middle layers as well as negative elevation angles. We took Fuzhou and Longyan radar as examples to compute elevation angles for precipitation mode, and derived their new observation mode VCP12. Observation experiment results show that radar detection ability in the lower atmosphere can be improved after low or negative elevation angles are added.
2013, 39(4):500-507.
DOI: 10.7519/j.issn.1000-0526.2013.04.013
Abstract:
In 2012, the annual mean temperature in China was 9.4℃, which was near normal but having some bigger fluctuations. The annual precipitation was 669.3 mm, 6.3% more than normal but with uneven spatial and temporal distribution. In 2012, many kinds of meteorological disasters occurred in China and some places were hit very seriously. There were many severe rainstorm events causing serious regional floods, mountain terrents and geological hazards. Very obvious floods were found successively in Yangtze River Basin, Yellow River Basin, Haihe River Basin, etc. Mountain terrents and geological hazards attacked Beijing, Gansu, Chongqing, Yunnan, Guizhou, Ningxia, Qinghai and Xinjiang. The typhoons named “Damrey”, “Saola” and “Haikui” landed in China in a raw within one week at the beginning of August, affecting 15 provinces (or autonomous regions and municipalities). Low temperature, overcast and rainy weathers in some local areas happened frequently, having severe influences on agriculture. Then, a wide range of snowstorms appeared in northern China for three times from November to December and some regions suffered seriously from snow hazards. In general, 2012 was a year with less meteorological disasters. Direct economic losses were significant though, the death toll and disater hit areas decreased notably.
In 2012, the annual mean temperature in China was 9.4℃, which was near normal but having some bigger fluctuations. The annual precipitation was 669.3 mm, 6.3% more than normal but with uneven spatial and temporal distribution. In 2012, many kinds of meteorological disasters occurred in China and some places were hit very seriously. There were many severe rainstorm events causing serious regional floods, mountain terrents and geological hazards. Very obvious floods were found successively in Yangtze River Basin, Yellow River Basin, Haihe River Basin, etc. Mountain terrents and geological hazards attacked Beijing, Gansu, Chongqing, Yunnan, Guizhou, Ningxia, Qinghai and Xinjiang. The typhoons named “Damrey”, “Saola” and “Haikui” landed in China in a raw within one week at the beginning of August, affecting 15 provinces (or autonomous regions and municipalities). Low temperature, overcast and rainy weathers in some local areas happened frequently, having severe influences on agriculture. Then, a wide range of snowstorms appeared in northern China for three times from November to December and some regions suffered seriously from snow hazards. In general, 2012 was a year with less meteorological disasters. Direct economic losses were significant though, the death toll and disater hit areas decreased notably.
2013, 39(4):508-515.
DOI: 10.7519/j.issn.1000-0526.2013.04.014
Abstract:
Anomalies of ocean and atmospheric circulations were analyzed and their impacts on temperature and precipitation anomalies were discussed. It is found that the warm condition was observed in the tropical central eastern Pacific Ocean during July to August 2012 and then it changed into normal condition, following the La Nina event which ended in March 2012. As a response of circulations to the warm oceanic condition, the western Pacific subtropical high was stronger and extended further west, controlling most southern part of China and causing temperature higher and precipitation less than normal there during September to October. From August to September, significant Indian Ocean dipole with a positive phase persisted in tropical Indian Ocean. Then, an anomalous anticyclone was excited over eastern tropical Pacific Ocean, with southwest airflows along its northwest edge affecting Southwest China and resulting in obvious autumn rainy season in its southern part. In 2012, onset of South China Sea summer monsoon was 1 pentad earlier than normal and the ending was 2 pentads later than normal, and the intensity was weaker than normal. And East Asian summer monsoon was observed the 4th strongest since 1951. Under the impact of anomalies of ocean and atmospheric circulation, colder than normal winter of 2011/2012 and autumn of 2012, warmer than normal spring and summer of 2012 appeared in China. Summer precipitation distribution shows more than normal precipitation in northern China and less than normal precipitation in southern China.
Anomalies of ocean and atmospheric circulations were analyzed and their impacts on temperature and precipitation anomalies were discussed. It is found that the warm condition was observed in the tropical central eastern Pacific Ocean during July to August 2012 and then it changed into normal condition, following the La Nina event which ended in March 2012. As a response of circulations to the warm oceanic condition, the western Pacific subtropical high was stronger and extended further west, controlling most southern part of China and causing temperature higher and precipitation less than normal there during September to October. From August to September, significant Indian Ocean dipole with a positive phase persisted in tropical Indian Ocean. Then, an anomalous anticyclone was excited over eastern tropical Pacific Ocean, with southwest airflows along its northwest edge affecting Southwest China and resulting in obvious autumn rainy season in its southern part. In 2012, onset of South China Sea summer monsoon was 1 pentad earlier than normal and the ending was 2 pentads later than normal, and the intensity was weaker than normal. And East Asian summer monsoon was observed the 4th strongest since 1951. Under the impact of anomalies of ocean and atmospheric circulation, colder than normal winter of 2011/2012 and autumn of 2012, warmer than normal spring and summer of 2012 appeared in China. Summer precipitation distribution shows more than normal precipitation in northern China and less than normal precipitation in southern China.
2013, 39(4):516-525.
DOI: 10.7519/j.issn.1000-0526.2013.04.015
Abstract:
During the first ten months of 2012, above average temperatures affected most of the globe’s land surface areas. This is the ninth warmest such period since records began in 1850. The 2011/2012 La Nina ended in the beginning of 2012, and the Arctic sea ice reached its lowest extent on 16 September. During 2012, notable climatic anomalies and extreme events were observed worldwide. Extreme low temperature and cold waves hit the Eurasian Continent during late January through mid February. Extremely severe floods never seen in the past 50 years occurred in the Valley of Amazon River in May. From June to September, North America suffered the most severe drought since 1956. Since June, tropical storms and typhoons attacked East Asia, Southeast Asia and the east coast of America. The global extreme warm events mainly appeared in the central and southern parts of Europe, central and southern parts of North America, southern part of South America, the western, southern and northeastern parts of Asia while the global extreme cold events were mainly experienced in most of Asia, the east of Europe and parts of eastern America. Besides, extremely severe rainfalls were seen in central Europe, western Africa, central and southern parts of South Americal, South Asia, Southeast Asia and southern part of Northeast Asia. Analyses show that, atmospheric circulation anomalies are the direct causes of above global significant weather and climate events. In addition, with global warming, the westerly basic flow becomes weakening and the meridional circulations in middle and high latitudes becomes strengthening, leading to the enhanced persistence of anomalous circulations and favorable dynamic conditions for the formation of climatic anomalies and extreme events.
During the first ten months of 2012, above average temperatures affected most of the globe’s land surface areas. This is the ninth warmest such period since records began in 1850. The 2011/2012 La Nina ended in the beginning of 2012, and the Arctic sea ice reached its lowest extent on 16 September. During 2012, notable climatic anomalies and extreme events were observed worldwide. Extreme low temperature and cold waves hit the Eurasian Continent during late January through mid February. Extremely severe floods never seen in the past 50 years occurred in the Valley of Amazon River in May. From June to September, North America suffered the most severe drought since 1956. Since June, tropical storms and typhoons attacked East Asia, Southeast Asia and the east coast of America. The global extreme warm events mainly appeared in the central and southern parts of Europe, central and southern parts of North America, southern part of South America, the western, southern and northeastern parts of Asia while the global extreme cold events were mainly experienced in most of Asia, the east of Europe and parts of eastern America. Besides, extremely severe rainfalls were seen in central Europe, western Africa, central and southern parts of South Americal, South Asia, Southeast Asia and southern part of Northeast Asia. Analyses show that, atmospheric circulation anomalies are the direct causes of above global significant weather and climate events. In addition, with global warming, the westerly basic flow becomes weakening and the meridional circulations in middle and high latitudes becomes strengthening, leading to the enhanced persistence of anomalous circulations and favorable dynamic conditions for the formation of climatic anomalies and extreme events.
2013, 39(4):526-530.
DOI: 10.7519/j.issn.1000-0526.2013.04.016
Abstract:
During the autumn of 2012, the surface air temperatures were below normal and the precipitation was above normal in most China, especially in the Northeast, North China, Jiangnan and South China. By analyzing the causes for the climatic anormaly, it is found that more precipitation in the Northeast and North China was closely related with the anomalous southeasterly moisture transport from the western North Pacific Ocean while precipitation anomalies in Jiangnan and South China were mainly influenced by the southwesterly warm and moist water vapor along the western boundary of the western North Pacific tropical high. Further analysis indicates that the sea surface temperature anomaly (SSTA) was the major extermal forcing factor for the climatic anomalies in the autumn of 2012. The significantly warm SSTA in the middle and high latitudes of the western North Pacific Ocean caused more precipitation in the Northeast and North China, whereas the positive tropical Indian Ocean dipole and weaker warm SSTA in the middle and eastern tropical Pacific Ocean were possibly conducive to more precipitation in Jiangnan and South China.
During the autumn of 2012, the surface air temperatures were below normal and the precipitation was above normal in most China, especially in the Northeast, North China, Jiangnan and South China. By analyzing the causes for the climatic anormaly, it is found that more precipitation in the Northeast and North China was closely related with the anomalous southeasterly moisture transport from the western North Pacific Ocean while precipitation anomalies in Jiangnan and South China were mainly influenced by the southwesterly warm and moist water vapor along the western boundary of the western North Pacific tropical high. Further analysis indicates that the sea surface temperature anomaly (SSTA) was the major extermal forcing factor for the climatic anomalies in the autumn of 2012. The significantly warm SSTA in the middle and high latitudes of the western North Pacific Ocean caused more precipitation in the Northeast and North China, whereas the positive tropical Indian Ocean dipole and weaker warm SSTA in the middle and eastern tropical Pacific Ocean were possibly conducive to more precipitation in Jiangnan and South China.
2013, 39(4):531-536.
DOI: 10.7519/j.issn.1000-0526.2013.04.017
Abstract:
The main characteristics of the general circulation of atmosphere in January 2013 are as follows: There are two polar vortex centers in the Northern Hemisphere with weaker strength and smaller scopes than normal years. Three waves appear in middle high latitudes. The Eurasia trough is located over West Siberia being farther north and leads to several streams of cold air to influence the north of China. The circulation in middle high latitudes varies from meridional circulation in the first dekad to the zonal circulation in the middle and last dekads of January. The subtropical high is near climatological normals. The East Asia trough is clearly stronger than usual. The south branch trough around 90°E is slightly weaker than the normal years. Monthly mean temperature in January over China is -5.2℃， 0.2℃ lower than the corresponding period of normal years. However, the 1st ten day mean temperature in January is 3℃ lower than the normal while, the last ten day temperature is 1.7℃ higher. Monthly mean precipitation (6.5 mm) is 50.8% less than the normal (13.2 mm). One cold surge process and three large scale haze and fog processes are experienced in this month. Low temperature, sleet and freezing rain hit the south of China while a snow disaster occurs in the north of China. Drought still continues in Yunnan, western Guizhou and southern Sichuan and some other places.
The main characteristics of the general circulation of atmosphere in January 2013 are as follows: There are two polar vortex centers in the Northern Hemisphere with weaker strength and smaller scopes than normal years. Three waves appear in middle high latitudes. The Eurasia trough is located over West Siberia being farther north and leads to several streams of cold air to influence the north of China. The circulation in middle high latitudes varies from meridional circulation in the first dekad to the zonal circulation in the middle and last dekads of January. The subtropical high is near climatological normals. The East Asia trough is clearly stronger than usual. The south branch trough around 90°E is slightly weaker than the normal years. Monthly mean temperature in January over China is -5.2℃， 0.2℃ lower than the corresponding period of normal years. However, the 1st ten day mean temperature in January is 3℃ lower than the normal while, the last ten day temperature is 1.7℃ higher. Monthly mean precipitation (6.5 mm) is 50.8% less than the normal (13.2 mm). One cold surge process and three large scale haze and fog processes are experienced in this month. Low temperature, sleet and freezing rain hit the south of China while a snow disaster occurs in the north of China. Drought still continues in Yunnan, western Guizhou and southern Sichuan and some other places.
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