NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric ci...NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric circulation anomalies on the troposphere.Stratospheric temperature and water-vapor anomalies provided good leading indicators of this weather event.The period from December 1st 2007 to February 28th 2008 was divided into 18 pentads.During the 6th pentad,temperature decreased significantly at 10 hPa in the near-polar stratospheric region,and the decreasing trend strengthened and extended downward and southward to middle and lower latitudes.During the 14th-18th pentads,the temperature decrease reached its maximum and extended to 30°N.This coincided with the widespread freezing rain and snow event.By the end of January 2008,the temperature decrease ended in the near-polar stratospheric region,but continued in the mid-latitude area of the troposphere as the freezing rain and snow weather persisted.Similar to the temperature variations,positive anomalies of relative humidity in the stratospheric near-polar region also strengthened and extended downward and southward,coinciding with the freezing rain and snow event.Along with the significant relationship between the freezing rain and snow disaster and stratospheric circulation anomalies,the stratospheric polar vortex changed its shape in late December,intensifying and spreading downward from the top of the stratosphere and southward to the Asian continent,resulting in a deepening of the East Asian Trough and a strengthening of meridional circulation.Before the occurrence of the freezing rain and snow event,temperature and vapor increases in the stratosphere transferred downward to the troposphere,along with a stratospheric flow in the near-polar region southward to lower latitudes.展开更多
In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and groun...In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and ground radars resulting in a lack of necessary emergency information. To compensate for the failure of ground observations and to provide timely disaster information, the National Satellite Meteorological Center of China (NSMC) established a snow storm monitoring system for the 2008 Frost Disaster, which was based on the WRF Three Dimension Variational Assimilation and Forecast system (with NOAH as the land surface sub-process model) cooperatively developed by NSMC and the National Center for Atmospheric Research (NCAR), US. This system made full use of ATOVS and NCEP data to provide estimates of snow water equivalent every 6 hours during the storm. In this study, the ATOVS assimilation based snowstorm monitoring scheme was explored in detail, while the modeled results with and without ATOVS assimilation were compared against related observations. Results showed that the coupling of ATOVS assimilation into the proposed monitoring system evidently delineates weather characteristics of the snowstorm process more accurately, and demonstrated the feasibility of the system for snowstorm monitoring and forecasting. Through theoretical analyses and case discussion, this study proposes a reliable and practicable scheme to provide timely and accurate information on snow spatial distribution and temporal development for disaster mitigation, and illustrates a new application of ATOVS data.展开更多
采用样地调查和取样,研究了2008年初中国南方冰雪灾害对粤北天然次生林的损害特征及其产生的林冠残体量。结果表明,灾害对粤北天然林造成严重损害,林木受害特征主要是胸径较大的植株断枝、断梢和断干较多,胸径较小的容易压弯,坡度大的...采用样地调查和取样,研究了2008年初中国南方冰雪灾害对粤北天然次生林的损害特征及其产生的林冠残体量。结果表明,灾害对粤北天然林造成严重损害,林木受害特征主要是胸径较大的植株断枝、断梢和断干较多,胸径较小的容易压弯,坡度大的林分翻蔸受害率增加。灾后林地林冠残体总量为38.12~43.52 t hm-2,平均41.25 t hm-2;地表凋落叶11.79~12.87 t hm-2,平均12.47 t hm-2;灾害产生的枝、干木质残体量为24.27~30.65 thm-2,平均28.41 t hm-2。天然常绿阔叶林产生的林冠残体量较常绿与落叶混交林和杉木人工林大,造成林地林冠残体量骤增,一方面使林地存在严重安全隐患（如发生火灾和病虫害的风险增加）,另一方面大量的林冠残体归还林地、改变了森林生态系统的结构与功能。展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.41005021,40830955)Scientific Research Foundation of CUIT(Grant No.CSRF20102)Special Fund for Public Welfare Industry(meteorology)(Grant No.GYHY(QX)2007-6-37)
文摘NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric circulation anomalies on the troposphere.Stratospheric temperature and water-vapor anomalies provided good leading indicators of this weather event.The period from December 1st 2007 to February 28th 2008 was divided into 18 pentads.During the 6th pentad,temperature decreased significantly at 10 hPa in the near-polar stratospheric region,and the decreasing trend strengthened and extended downward and southward to middle and lower latitudes.During the 14th-18th pentads,the temperature decrease reached its maximum and extended to 30°N.This coincided with the widespread freezing rain and snow event.By the end of January 2008,the temperature decrease ended in the near-polar stratospheric region,but continued in the mid-latitude area of the troposphere as the freezing rain and snow weather persisted.Similar to the temperature variations,positive anomalies of relative humidity in the stratospheric near-polar region also strengthened and extended downward and southward,coinciding with the freezing rain and snow event.Along with the significant relationship between the freezing rain and snow disaster and stratospheric circulation anomalies,the stratospheric polar vortex changed its shape in late December,intensifying and spreading downward from the top of the stratosphere and southward to the Asian continent,resulting in a deepening of the East Asian Trough and a strengthening of meridional circulation.Before the occurrence of the freezing rain and snow event,temperature and vapor increases in the stratosphere transferred downward to the troposphere,along with a stratospheric flow in the near-polar region southward to lower latitudes.
基金supported by National Natural Science Foundation of China (Grant Nos.40705037 and 40801175)the Open Fund by Numerical Model Innovation Base of China Meteorological Administration (Agreement 2006-12)the R & D Special Fund for Public Welfare Industry (Meteorology GYHY(QX)2007-6-9)
文摘In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and ground radars resulting in a lack of necessary emergency information. To compensate for the failure of ground observations and to provide timely disaster information, the National Satellite Meteorological Center of China (NSMC) established a snow storm monitoring system for the 2008 Frost Disaster, which was based on the WRF Three Dimension Variational Assimilation and Forecast system (with NOAH as the land surface sub-process model) cooperatively developed by NSMC and the National Center for Atmospheric Research (NCAR), US. This system made full use of ATOVS and NCEP data to provide estimates of snow water equivalent every 6 hours during the storm. In this study, the ATOVS assimilation based snowstorm monitoring scheme was explored in detail, while the modeled results with and without ATOVS assimilation were compared against related observations. Results showed that the coupling of ATOVS assimilation into the proposed monitoring system evidently delineates weather characteristics of the snowstorm process more accurately, and demonstrated the feasibility of the system for snowstorm monitoring and forecasting. Through theoretical analyses and case discussion, this study proposes a reliable and practicable scheme to provide timely and accurate information on snow spatial distribution and temporal development for disaster mitigation, and illustrates a new application of ATOVS data.
文摘采用样地调查和取样,研究了2008年初中国南方冰雪灾害对粤北天然次生林的损害特征及其产生的林冠残体量。结果表明,灾害对粤北天然林造成严重损害,林木受害特征主要是胸径较大的植株断枝、断梢和断干较多,胸径较小的容易压弯,坡度大的林分翻蔸受害率增加。灾后林地林冠残体总量为38.12~43.52 t hm-2,平均41.25 t hm-2;地表凋落叶11.79~12.87 t hm-2,平均12.47 t hm-2;灾害产生的枝、干木质残体量为24.27~30.65 thm-2,平均28.41 t hm-2。天然常绿阔叶林产生的林冠残体量较常绿与落叶混交林和杉木人工林大,造成林地林冠残体量骤增,一方面使林地存在严重安全隐患（如发生火灾和病虫害的风险增加）,另一方面大量的林冠残体归还林地、改变了森林生态系统的结构与功能。
