摘要
利用NCEP/NCAR再分析月平均资料,通过构造青藏高原(下称高原)对流层顶气压指数以及选取1992年和1998年这两个高原对流层顶气压正、负异常最大值年份进行对比分析,研究了北半球夏季高原对流层顶气压异常变动的物理机制。结果表明:(1)高原对流层顶气压异常变动与平流层和对流层气温及位势高度异常有密切联系,同时,与地表温度异常也有较好的关系。1992年的地表温度异常偏低,使得高原对流层顶气压异常偏高;而1998年的地表温度与1992年的有很好的反位相关系,地表温度异常偏高,引起高原对流层顶气压异常偏低。(2)高原对流层顶气压异常变动与同区域OLR变化呈较好的正相关关系,进一步诊断850hPa和200hPa的高、低空环流及整层水汽配置,发现1992年高原对流层顶气压偏高对应着低空风场的反气旋式辐散以及高空风场的气旋式辐合,并且伴随着整层水汽辐散和南亚高压的异常偏弱,而1998年的情况与之相反。说明高原地区对流异常是1992年和1998年高原对流层顶气压异常变动的主要原因之一。(3)显著的整层大气非绝热加热差异也是导致1992年与1998年高原区域对流层顶气压显著差异的主要原因。
Using the monthly mean data from NCEP/NCAR reanalysis,the building tropopause pressure index and the selected years of 1992 and 1998 which are respectively the highest and lowest year of tropopause pressure anomaly over Tibetan Plateau to contrast and analyze,the mechanism of anomalous variation of tropopause pressure over Tibetan Plateau in summer is investigated.The results are summarized as follows：（1） Over Tibetan Plateau,the variations of tropopause pressure have been found well correlated with respectively the anomalous temperature and geopotential height in both troposphere and stratosphere.The anomalous tropopause pressure correlates well with the anomalous surface temperature over Tibetan Plateau.In 1992（1998）,the surface temperature is anomalous low（high）,tropopause pressure over Tibetan Plateau is anomalous high（low）.（2） Over Tibetan Plateau,the correlation of tropopause pressure and OLR is positive.Furthermore,for further diagnosing the circulation fields between 850 hPa and 200 hPa and the whole troposphere vapour field,it is found that the anomalous high tropopause pressure in 1992 is corresponding to the anticyclonic divergence in low level wind field and the cyclonic convergence in upper wind field,and coupled with divergence of the whole troposphere vapour fields and the South Asia high weakens at the same time.While in 1998,the case is just opposite to 1992.These facts indicate that the anomalous convection results in the significant difference of tropopause pressure over Tibetan Plateau in 1992 and 1998.（3）Furthermore,the vertically integrated heat budget anomaly is also responsible for explaining the tropopause pressure anomaly over Tibetan Plateau in 1992 and 1998.
出处
《高原气象》
CSCD
北大核心
2011年第3期559-567,共9页
Plateau Meteorology
基金
国家自然科学基金项目(40675025,41005046)
国家重点基础研究发展计划(2010CB428602)共同资助
关键词
青藏高原
对流层顶气压
物理机制
对流异常
Tibetan Plateau
Tropopause pressure
Physical mechanism
Convection anomaly
