热带副热带高度异常对长江流域和华北旱涝影响的数值模拟与分析

前期南亚高压的异常增强或者减弱,热带、副热带地区100 hPa高度的异常增高或者降低,热带西风的异常增强或者减弱,对长江流域和华北地区夏季的降水异常具有预示作用。文中设计了一系列的数值试验进行模拟研究,包括控制试验、敏感试验和4组合成试验。合成试验模拟结果表明,前期热带、副热带高度异常分布,能够再现长江流域、华北旱涝情况。前期南亚高压、热带、副热带高度、风异常对长江流域和华北地区夏季降水的异常均有预示作用。100 hPa叠加高度、风异常的敏感试验结果表明:前期南亚高压、热带与副热带地区100 hPa高度场和环流场的异常不仅可以预示、事实上能够引起长江流域和华北夏季降水的异常———前期南亚高压异常增强、热带、副热带地区100 hPa高度场异常增高、西风异常增强,易引起长江流域降水偏多、华北降水偏少;反之,则容易引起长江流域降水偏少、华北降水偏多。

SIMULATION AND ANALYSIS ABOUT THE EFFECTS OF GEOPOTENTIAL HEIGHT ANOMALY IN TROPICAL AND SUBTROPICAL REGION ON DROUGHTS OR FLOODS IN THE YANGTZE RIVER VALLEY AND NORTH CHINA

Previous study comes to the conclusion: based on the anomalies of the South Asian High(SAH),anomaly of 100 hPa geopotential height and 100 hPa circulation over tropical and subtropical region in previous year,we can predict precipitation anomaly in the Yangtze River Valley and North China.To test its validity,a series of experiments have been designed and operated.The experiments include controlled experiment,sensitive experiment(which has added anomalies into 100 hPa geopotential height and wind field) and four composite experiments.Experiments based on the composed initial field such as EPR-CF,EPR-CD,EPR-HF,and EPR-HD, can reproduce the floods or droughts in the Yangtze River Valley and North China.It suggests that anomalies of South Asian High,100 hPa geopotential height and circulation over tropical and subtropical region can probably imply summer precipitation anomalies in the two regions.Sensible experiment results show that anomalies of the SAH,100 hPa geopotential height and wind field in previous period is a signal of floods or droughts the following summer in the Yangtze River Valley and North China.And it is also one of the factors that have impact on summer precipitation anomaly in the two regions.Positive anomaly of 100 hPa geopotential height and the anomalous intensifying of the SAH and southwest flow will induce floods in the Yangtze River Valley and droughts in North China;while negative anomaly of 100 hPa geopotential height and anomalous weakening of the SAH and southwest flow will induce droughts in the Yangtze River Valley and floods in North China.