ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 40,Issue 4,2014 Table of Contents
2014, 40(4):389-399.
DOI: 10.7519/j.issn.1000-0526.2014.04.001
Abstract:
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
2014, 40(4):400-411.
DOI: 10.7519/j.issn.1000-0526.2014.04.002
Abstract:
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
2014, 40(4):412-423.
DOI: 10.7519/j.issn.1000-0526.2014.04.003
Abstract:
By using the data of sounding and surface dense AWS, the Doppler weather radar, the satellite cloud images and the NCEP 1°×1° reanalysis data, forming mechanism of the rainstorm on 5 June 2012 in Hexi Corridor is analyzed. The results show that this rainstorm is caused by interactions of the plateau vortex shifting northwards, the cold air moving toward southeast from eastern Xinjiang and the upper level jet. The water vapor transported to the central western corridor is originated from the northwest air flow in eastern Xinjiang and the easterly air flow of north eastern plateau. The isentropic surface over the rainstorm area is steep, atmosphere is weak and unstable easily inducing the marked increase of vertical vorticity and convergence. The dry intrusion that occurs on the south side of plateau vortex from upper troposphere enhances the baroclinity of vortex, which is conducive to vortex development and moving northwards out of the Tibetan Plateau. The rainstorm happens in the confluence area of northwest air stream from eastern Xinjiang and east air stream on the north side of the plateau vortex and in the head part of the vortex comma cloud, and the most severe rainfall occurrs near the meso β scale rebellious wind area of Doppler radar radial velocity.
By using the data of sounding and surface dense AWS, the Doppler weather radar, the satellite cloud images and the NCEP 1°×1° reanalysis data, forming mechanism of the rainstorm on 5 June 2012 in Hexi Corridor is analyzed. The results show that this rainstorm is caused by interactions of the plateau vortex shifting northwards, the cold air moving toward southeast from eastern Xinjiang and the upper level jet. The water vapor transported to the central western corridor is originated from the northwest air flow in eastern Xinjiang and the easterly air flow of north eastern plateau. The isentropic surface over the rainstorm area is steep, atmosphere is weak and unstable easily inducing the marked increase of vertical vorticity and convergence. The dry intrusion that occurs on the south side of plateau vortex from upper troposphere enhances the baroclinity of vortex, which is conducive to vortex development and moving northwards out of the Tibetan Plateau. The rainstorm happens in the confluence area of northwest air stream from eastern Xinjiang and east air stream on the north side of the plateau vortex and in the head part of the vortex comma cloud, and the most severe rainfall occurrs near the meso β scale rebellious wind area of Doppler radar radial velocity.
2014, 40(4):424-432.
DOI: 10.7519/j.issn.1000-0526.2014.04.004
Abstract:
By using precipitation data collected every six hours by 2419 stations from April 1 to March 31 in 2013, precipitation forecast data of ECMWF and Japan high resolution model, and hourly rainfall data fusion by CMORPH (NOAA Climate Prediction Center Morphing Method) satellites and more than 30 thousand automatic stations based on contingency table and Taylor diagram statistical method, the precipitation forecasting capabilites of ECMWF and Japan high resolution model by every 6 h, 12 h, 24 h segment are comparatively analysed. The results show that: (1) Generally， ECMWF has an advantage over Japan high resolution model whose forecast dispersion is a bit larger. However, the forecast of ECMWF is relative steady, agreeing more with the observation. (2) The precipitation frequency predicted in weather forecasting by the two models is higher than the real case while the forecast of rainstorm frequency is lower than it. However as piecewise intervals increase, this situation is improved. (3) The 6 h fractional precipitation weather forecast score by ECMWF is lower than by the Japan 〖JP2〗model while the 12 h and 24 h fractional precipitation weather forecast scores of ECMWF are higher than those of Japan model, but its rainstorm forecast scores are all higher than those of the Japan model. (4) By changing forecast bias using threshold adjustment, the forecasting skill scores are improved to some extent. (5) Regarding the spatial distribution, the model can forecast precipitation more reasonably in coastal areas than in the northwestern area.〖JP〗
By using precipitation data collected every six hours by 2419 stations from April 1 to March 31 in 2013, precipitation forecast data of ECMWF and Japan high resolution model, and hourly rainfall data fusion by CMORPH (NOAA Climate Prediction Center Morphing Method) satellites and more than 30 thousand automatic stations based on contingency table and Taylor diagram statistical method, the precipitation forecasting capabilites of ECMWF and Japan high resolution model by every 6 h, 12 h, 24 h segment are comparatively analysed. The results show that: (1) Generally， ECMWF has an advantage over Japan high resolution model whose forecast dispersion is a bit larger. However, the forecast of ECMWF is relative steady, agreeing more with the observation. (2) The precipitation frequency predicted in weather forecasting by the two models is higher than the real case while the forecast of rainstorm frequency is lower than it. However as piecewise intervals increase, this situation is improved. (3) The 6 h fractional precipitation weather forecast score by ECMWF is lower than by the Japan 〖JP2〗model while the 12 h and 24 h fractional precipitation weather forecast scores of ECMWF are higher than those of Japan model, but its rainstorm forecast scores are all higher than those of the Japan model. (4) By changing forecast bias using threshold adjustment, the forecasting skill scores are improved to some extent. (5) Regarding the spatial distribution, the model can forecast precipitation more reasonably in coastal areas than in the northwestern area.〖JP〗
XU Guoqiang
,
WEI Rongqing
,
JIA Lihong
,
TANG Hao
,
ZHU Feng
,
LU Xinyu
,
ZHENG Xiaohui
,
WANG Deli
2014, 40(4):433-439.
DOI: 10.7519/j.issn.1000-0526.2014.04.005
Abstract:
To fully use the information of forecast products from numerical models, the errors of the products are analyzed. According to the results of the analysis, a refined forecast method is proposed and based on it a new Xinjiang refined numerical forecast system is developed. Preliminary tests are conducted and the results show that the new method has a positive effect on temperature forecasting in the area of Xinjiang. After adjustment of correction coefficients and usage of more observations at different time points, the corrected temperature is expected to be much closer to the observations. That is, the method can improve the accuracy of temperature forecasting and has operational application potential.
To fully use the information of forecast products from numerical models, the errors of the products are analyzed. According to the results of the analysis, a refined forecast method is proposed and based on it a new Xinjiang refined numerical forecast system is developed. Preliminary tests are conducted and the results show that the new method has a positive effect on temperature forecasting in the area of Xinjiang. After adjustment of correction coefficients and usage of more observations at different time points, the corrected temperature is expected to be much closer to the observations. That is, the method can improve the accuracy of temperature forecasting and has operational application potential.
2014, 40(4):440-449.
DOI: 10.7519/j.issn.1000-0526.2014.04.006
Abstract:
Daily meteorological data of Sichuan Basin and NCEP/ NCAR reanalysis data are employed to diagnose the influences of East Asian and plateau summer monsoon on the summer rainfall of Sichuan Basin. The results show that the summer rainfall series of the western and eastern basin and the correlation distribution of summer rainfall over the whole China have similar distribution with the rain pattern Ⅰand Ⅱ respectively. To further understand the effect of East Asian and plateau summer monsoon on the rainfall of the basin, regressive analysis is performed. First the circulation field related to East Asian summer monsoon is obtained, then after the part of East Asian summer monsoon is removed from the circulation field using the regression method, the circulation field related to plateau summer monsoon is yielded, which is statistically independent of East Asian summer monsoon. Using the 1961 and 1998 circulation fields as examples to analyze the influences of East Asian and plateau summer monsoon, it is found that both East Asian summer monsoon and plateau summer monsoon have important influences on the rainfall of Sichuan Basin, of which the rainfall of western part is mainly related to plateau monsoon, and the summer rainfall of eastern part mainly is related to both East Asian and plateau summer monsoon, but East Asian monsoon is predominant.
Daily meteorological data of Sichuan Basin and NCEP/ NCAR reanalysis data are employed to diagnose the influences of East Asian and plateau summer monsoon on the summer rainfall of Sichuan Basin. The results show that the summer rainfall series of the western and eastern basin and the correlation distribution of summer rainfall over the whole China have similar distribution with the rain pattern Ⅰand Ⅱ respectively. To further understand the effect of East Asian and plateau summer monsoon on the rainfall of the basin, regressive analysis is performed. First the circulation field related to East Asian summer monsoon is obtained, then after the part of East Asian summer monsoon is removed from the circulation field using the regression method, the circulation field related to plateau summer monsoon is yielded, which is statistically independent of East Asian summer monsoon. Using the 1961 and 1998 circulation fields as examples to analyze the influences of East Asian and plateau summer monsoon, it is found that both East Asian summer monsoon and plateau summer monsoon have important influences on the rainfall of Sichuan Basin, of which the rainfall of western part is mainly related to plateau monsoon, and the summer rainfall of eastern part mainly is related to both East Asian and plateau summer monsoon, but East Asian monsoon is predominant.
7 Distribution Characteristics of Dry Hot Wind and Its Response to Climate Change in Qinghai Plateau
2014, 40(4):450-457.
DOI: 10.7519/j.issn.1000-0526.2014.04.007
Abstract:
Based on 50 years’ meteorological data from 56 meteorological stations in Qinghai Province from 1961 to 2010, the spatial distribution, basic climate characteristics and occurence days of dry hot wind are analyzed. The results show that the Qaidam Basin is the main region for dry hot wind over Qinghai Plateau where Xiaozaohuo and Xunhua are the stations that frequently see the dry hot wind followed by Haidong Area. In the past 50 years, the number of 〖JP2〗dry hot wind days and its intensity have showed a rising trend. During 2001—2010, the annual average dry hot wind events were 29 times, and respectively 17 times and 11 times more than in 1960s and 1970s. In recent years, the dry hot wind days increased, which result from the obvious increase of average maximum temperature and the gradual decrease of the relative humidity.〖JP〗
Based on 50 years’ meteorological data from 56 meteorological stations in Qinghai Province from 1961 to 2010, the spatial distribution, basic climate characteristics and occurence days of dry hot wind are analyzed. The results show that the Qaidam Basin is the main region for dry hot wind over Qinghai Plateau where Xiaozaohuo and Xunhua are the stations that frequently see the dry hot wind followed by Haidong Area. In the past 50 years, the number of 〖JP2〗dry hot wind days and its intensity have showed a rising trend. During 2001—2010, the annual average dry hot wind events were 29 times, and respectively 17 times and 11 times more than in 1960s and 1970s. In recent years, the dry hot wind days increased, which result from the obvious increase of average maximum temperature and the gradual decrease of the relative humidity.〖JP〗
2014, 40(4):458-465.
DOI: 10.7519/j.issn.1000-0526.2014.04.008
Abstract:
Based on nearly 30 year’ observational data and automatic weather station data at different altitudes during 1980-2010, and using weather science theory and mathematical statistics, the precipitation distribution difference and its formation cause between Jiuhua Mountains and its surrounding hills are studied in this paper. The results show that: the spatio temporal distributions of precipitation in different regions are very uneven, and the average annual rainfall in Jiuhua Mountaions is 34.1% more than the surrounding areas, and precipitation mainly is concentrated in May to September. The formation cause mainly exists in the difference between the local water vapor transport conditions and the vertical motion condition in different regions and it affects precipitation when the terrain elevation is higher than 200 m, and rainfall increasing with the increase of altitude, and the enhancement effect on precipitation is the most obvious in 400-900 m height. The terrain effect on rainfall is more significant in mountains, and its average contribution rate is 37.6%. The greater the intensity of precipitation, the more obvious of its effect. Analysis on the differences and the causes of the different regional precipitation distribution offers an important reference to the regional forecasts of rainfall and water resources research applications.
Based on nearly 30 year’ observational data and automatic weather station data at different altitudes during 1980-2010, and using weather science theory and mathematical statistics, the precipitation distribution difference and its formation cause between Jiuhua Mountains and its surrounding hills are studied in this paper. The results show that: the spatio temporal distributions of precipitation in different regions are very uneven, and the average annual rainfall in Jiuhua Mountaions is 34.1% more than the surrounding areas, and precipitation mainly is concentrated in May to September. The formation cause mainly exists in the difference between the local water vapor transport conditions and the vertical motion condition in different regions and it affects precipitation when the terrain elevation is higher than 200 m, and rainfall increasing with the increase of altitude, and the enhancement effect on precipitation is the most obvious in 400-900 m height. The terrain effect on rainfall is more significant in mountains, and its average contribution rate is 37.6%. The greater the intensity of precipitation, the more obvious of its effect. Analysis on the differences and the causes of the different regional precipitation distribution offers an important reference to the regional forecasts of rainfall and water resources research applications.
2014, 40(4):466-472.
DOI: 10.7519/j.issn.1000-0526.2014.04.009
Abstract:
Based on the analysis of the monthly and daily traffic accidents rate of per 10 000 vehicle (TAR) and meteorological elements over two years (01/01/2007-30/01/2009) observed from Jingjintang Highway, the correlation analysis is done on diurnal variation between mean TAR and integrated meteorological parameter (IMP). The results show that the diurnal variation of accident in each month usually has two peaks. The mainly peak occurs during 05:00-07:00 BT, and the second peak during 21:00-23:00 BT. The maximum annual average accident can reach to 1.8 TAR. The mean hourly TAR in each month has some relationship in parabola, exponential, or linear with the IMP that means the TAR has the same trend with IMP. To improve traffic weather service for highway, a four level traffic weather risk and safety index is set up. The simulated forecast of diurnal IMP of two months is applied by utilizing a WRF based NWP outputs, whose mean monthly accuracy is 62.5% and 95.8% respectively. This result provides reasonable basis for highway safety management and has wide spread application value for highway traffic weather service in Huabei Region.
Based on the analysis of the monthly and daily traffic accidents rate of per 10 000 vehicle (TAR) and meteorological elements over two years (01/01/2007-30/01/2009) observed from Jingjintang Highway, the correlation analysis is done on diurnal variation between mean TAR and integrated meteorological parameter (IMP). The results show that the diurnal variation of accident in each month usually has two peaks. The mainly peak occurs during 05:00-07:00 BT, and the second peak during 21:00-23:00 BT. The maximum annual average accident can reach to 1.8 TAR. The mean hourly TAR in each month has some relationship in parabola, exponential, or linear with the IMP that means the TAR has the same trend with IMP. To improve traffic weather service for highway, a four level traffic weather risk and safety index is set up. The simulated forecast of diurnal IMP of two months is applied by utilizing a WRF based NWP outputs, whose mean monthly accuracy is 62.5% and 95.8% respectively. This result provides reasonable basis for highway safety management and has wide spread application value for highway traffic weather service in Huabei Region.
2014, 40(4):473-481.
DOI: 10.7519/j.issn.1000-0526.2014.04.010
Abstract:
The new scatterometer Advanced SCATterometer (ASCAT) onboard MetOP A satellite provides surface wind speed and direction over global oceans with a spatial resolution of 25 km and 12.5 km square over two swaths. The accuracy of ASCAT retrieved wind is determined through various speed and direction comparisons with moored buoys laid by China Meteorological Administration (CMA). The wind speed bias between ASCAT and buoys is 0.9 m·s-1. The average absolute error and root mean squared difference are 1.2 m·s-1 and 1.4 m·s-1, respectively. The ASCAT wind over China offshore sea is credible with the correlation coefficient of wind speed between ASCAT and buoys is 0.94. And the primary operational application of ASCAT winds is on processing gradually in National Meteorological Centre (NMC), which can provide text data and PNG figures quasi real time.
The new scatterometer Advanced SCATterometer (ASCAT) onboard MetOP A satellite provides surface wind speed and direction over global oceans with a spatial resolution of 25 km and 12.5 km square over two swaths. The accuracy of ASCAT retrieved wind is determined through various speed and direction comparisons with moored buoys laid by China Meteorological Administration (CMA). The wind speed bias between ASCAT and buoys is 0.9 m·s-1. The average absolute error and root mean squared difference are 1.2 m·s-1 and 1.4 m·s-1, respectively. The ASCAT wind over China offshore sea is credible with the correlation coefficient of wind speed between ASCAT and buoys is 0.94. And the primary operational application of ASCAT winds is on processing gradually in National Meteorological Centre (NMC), which can provide text data and PNG figures quasi real time.
HOU Wei
,
CHEN Yu
,
LI Ying
,
WANG Youmin
,
WANG Zunya
,
ZHU Xiaojin
,
ZHOU Bing
,
YE Dianxiu
,
ZHAO Shanshan
,
CAI Wenyue
,
YIN Yizhou
,
ZHONG Hailing
,
ZHAO Lin
2014, 40(4):482-493.
DOI: 10.7519/j.issn.1000-0526.2014.04.011
Abstract:
In 2013, the mean annual precipitation in China was 653.5 mm, 4％ higher than normal and slightly less than in 2012. The seasonal precipitation was below normal in winter, but above normal in spring, summer and fall. The annual mean temperature over China was the fourth highest since 1961, 0.6℃ higher than normal and 0.8℃ higher than in 2012. Mean temperature was lower than normal in winter, but persistently higher than normal in spring, summer, and fall. In 2013, the winter monsoon in East Asia was stronger than normal and the subtropical high intensity over the Northwest Pacific in summer was weaker clearly; the summer monsoon in the South China Sea broke out earlier but ended later with weak intensity. Besides, the first rainy season in South China began earlier and ended later with a larger amount of precipitation than normal. The beginning of Meiyu in the middle and low reaches of Yangtze River started later and ended earlier with less precipitation than normal. The rainy season in North China began earlier, bringing more precipitation than normal. The beginning of autumnal rain of Huaxi (Western China) started earlier and ended later with a smaller amount of precipitation than normal. The rainy season in Southwest China started earlier and ended later than normal with a small amount of precipitation. In 2013, the main meteorological disasters in China were rainstorms, typhoons, heat wave, bringing serious losses to local areas. In general, 2013 was a year with moderate meteorological disaster, and the economic losses were serious, but the death toll and disaster hit areas were fewer in amount.
In 2013, the mean annual precipitation in China was 653.5 mm, 4％ higher than normal and slightly less than in 2012. The seasonal precipitation was below normal in winter, but above normal in spring, summer and fall. The annual mean temperature over China was the fourth highest since 1961, 0.6℃ higher than normal and 0.8℃ higher than in 2012. Mean temperature was lower than normal in winter, but persistently higher than normal in spring, summer, and fall. In 2013, the winter monsoon in East Asia was stronger than normal and the subtropical high intensity over the Northwest Pacific in summer was weaker clearly; the summer monsoon in the South China Sea broke out earlier but ended later with weak intensity. Besides, the first rainy season in South China began earlier and ended later with a larger amount of precipitation than normal. The beginning of Meiyu in the middle and low reaches of Yangtze River started later and ended earlier with less precipitation than normal. The rainy season in North China began earlier, bringing more precipitation than normal. The beginning of autumnal rain of Huaxi (Western China) started earlier and ended later with a smaller amount of precipitation than normal. The rainy season in Southwest China started earlier and ended later than normal with a small amount of precipitation. In 2013, the main meteorological disasters in China were rainstorms, typhoons, heat wave, bringing serious losses to local areas. In general, 2013 was a year with moderate meteorological disaster, and the economic losses were serious, but the death toll and disaster hit areas were fewer in amount.
2014, 40(4):494-501.
DOI: 10.7519/j.issn.1000-0526.2014.04.012
Abstract:
Anomalies of oceanic and atmospheric circulations are analyzed and their impacts on temperature and precipitation anomalies of 2013 in China are discussed. The results show that the Arctic Oscillation (AO) experienced negative phase during the 2012/2013 winter. At 500 hPa, a “two troughs and one ridge” anomalous geopotential height pattern dominated the mid high latitudes in Eurasia, leading to an enhanced ridge and trough over Urals and East Asia, respectively, and further leading to be colder than normal situation over China. While the Siberian high exhibited strong intra seasonal variations, the temperature over China had two stage variations last winter, warmer in the early winter and colder in the late winter. Further research indicates that the reduced Arctic sea ice extent in the last autumn was responsible for the stronger East Asian winter monsoon. During the period from winter to summer 2013, the anomalous low sea surface temperature (SST) was observed in the tropical central and eastern Pacific, while abnormal high SST in tropical western Pacific and oceanic continent. As a response of atmospheric circulation to the anomalous tropical oceanic condition, the western Pacific subtropical high extended further north, leading to more precipitation over the northern part of China during the summer. Meanwhile, the northward extending of the western Pacific subtropical high dominated most southern part of China, causing higher temperature and less precipitation than normal in the region in summer. In 2013, onset of South China Sea summer monsoon was 2 pentads earlier than normal and the ending was 4 pentads later than normal, and the intensity was weaker than normal.
Anomalies of oceanic and atmospheric circulations are analyzed and their impacts on temperature and precipitation anomalies of 2013 in China are discussed. The results show that the Arctic Oscillation (AO) experienced negative phase during the 2012/2013 winter. At 500 hPa, a “two troughs and one ridge” anomalous geopotential height pattern dominated the mid high latitudes in Eurasia, leading to an enhanced ridge and trough over Urals and East Asia, respectively, and further leading to be colder than normal situation over China. While the Siberian high exhibited strong intra seasonal variations, the temperature over China had two stage variations last winter, warmer in the early winter and colder in the late winter. Further research indicates that the reduced Arctic sea ice extent in the last autumn was responsible for the stronger East Asian winter monsoon. During the period from winter to summer 2013, the anomalous low sea surface temperature (SST) was observed in the tropical central and eastern Pacific, while abnormal high SST in tropical western Pacific and oceanic continent. As a response of atmospheric circulation to the anomalous tropical oceanic condition, the western Pacific subtropical high extended further north, leading to more precipitation over the northern part of China during the summer. Meanwhile, the northward extending of the western Pacific subtropical high dominated most southern part of China, causing higher temperature and less precipitation than normal in the region in summer. In 2013, onset of South China Sea summer monsoon was 2 pentads earlier than normal and the ending was 4 pentads later than normal, and the intensity was weaker than normal.
2014, 40(4):502-509.
DOI: 10.7519/j.issn.1000-0526.2014.04.013
Abstract:
The possible precursors of the summer climate in 2013 are reviewed which are that in the winter of 2012/2013, ENSO neutral with slightly cold condition persists in the central and eastern tropical Pacific, the Arctic sea ice area is significantly less, and the snow cover over the Tibetan Plateau is less than normal. These features have an important impact on the following East Asia summer monsoon. By diagnosing and analyzing the possible influence of these precursors, the features of stronger East Asian summer monsoon and main rainfall belt locating the northern China are successfully captured in the prediction issued by the National Climate Centre of CMA in late March 2013. In addition, the onset date of the South China Sea summer monsoon is earlier, the Meiyu along the middle low reaches of Yangtze River Valley is less with later onset and short rainfall period, and the rainy season in North China is earlier and more than normal. These intra seasonal features are all successfully predicted. Finally, the imperfection in the summer climate prediction is discussed.
The possible precursors of the summer climate in 2013 are reviewed which are that in the winter of 2012/2013, ENSO neutral with slightly cold condition persists in the central and eastern tropical Pacific, the Arctic sea ice area is significantly less, and the snow cover over the Tibetan Plateau is less than normal. These features have an important impact on the following East Asia summer monsoon. By diagnosing and analyzing the possible influence of these precursors, the features of stronger East Asian summer monsoon and main rainfall belt locating the northern China are successfully captured in the prediction issued by the National Climate Centre of CMA in late March 2013. In addition, the onset date of the South China Sea summer monsoon is earlier, the Meiyu along the middle low reaches of Yangtze River Valley is less with later onset and short rainfall period, and the rainy season in North China is earlier and more than normal. These intra seasonal features are all successfully predicted. Finally, the imperfection in the summer climate prediction is discussed.
2014, 40(4):510-514.
DOI: 10.7519/j.issn.1000-0526.2014.04.014
Abstract:
During the autumn of 2013, the surface air temperature was higher than normal and the precipitation amount was above normal in most part of the Northeast China, especially from October to November. The diagnosing results show that the external forcing of higher sea surface temperature in Northwest Pacific Ocean and atmospheric circulation features, may lead to the climatic anomaly in Northeast China. The abnormal circulation pattern with obviously positive phase of Arctic Oscillation, and positive anomaly of geopotential height over Northeast China is unfavorable for cold air to move southward causing higher air temperature in Northeast China for the season. Meanwhile, in mid late Autumn, precipitation anomaly in the Northeast China is mainly influenced by the stronger southeasterly moisture transport from the western North Pacific Ocean.
During the autumn of 2013, the surface air temperature was higher than normal and the precipitation amount was above normal in most part of the Northeast China, especially from October to November. The diagnosing results show that the external forcing of higher sea surface temperature in Northwest Pacific Ocean and atmospheric circulation features, may lead to the climatic anomaly in Northeast China. The abnormal circulation pattern with obviously positive phase of Arctic Oscillation, and positive anomaly of geopotential height over Northeast China is unfavorable for cold air to move southward causing higher air temperature in Northeast China for the season. Meanwhile, in mid late Autumn, precipitation anomaly in the Northeast China is mainly influenced by the stronger southeasterly moisture transport from the western North Pacific Ocean.
2014, 40(4):515-520.
DOI: 10.7519/j.issn.1000-0526.2014.04.015
Abstract:
The following are the main characteristics of the general circulation of atmosphere in January 2014. There are two polar vortex centers in the Northern Hemisphere located more southward than normal years. The circulation presents latitudinal patterns in middle high latitudes. The south branch trough is averagely located near 70°E, being more westward than normal years. Besides, the subtropical high is a little weaker than normal years. The monthly mean precipitation is 6.2 mm, 53.0% less than the normal (13.2 mm). The monthly mean temperature is -3.4℃, 1.6℃ higher than the normal (-5.0℃). There is one cold air process nationwide and four rainfall processes in the month. Lack of rainfall has caused meteorological drought in the northern winter wheat region. Meanwhile, large scale fog and haze weather appear in the central and the east of China. Moreover, cryogenic snow weather hit the south of China.
The following are the main characteristics of the general circulation of atmosphere in January 2014. There are two polar vortex centers in the Northern Hemisphere located more southward than normal years. The circulation presents latitudinal patterns in middle high latitudes. The south branch trough is averagely located near 70°E, being more westward than normal years. Besides, the subtropical high is a little weaker than normal years. The monthly mean precipitation is 6.2 mm, 53.0% less than the normal (13.2 mm). The monthly mean temperature is -3.4℃, 1.6℃ higher than the normal (-5.0℃). There is one cold air process nationwide and four rainfall processes in the month. Lack of rainfall has caused meteorological drought in the northern winter wheat region. Meanwhile, large scale fog and haze weather appear in the central and the east of China. Moreover, cryogenic snow weather hit the south of China.
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ISSN:1000-0526 CN:11-2282/P