青藏高原5—10月地表潜热通量与青海同期降水之间的关系

Relationship Between Surface Latent Heat Flux over the Qinghai-Tibetan Plateau and Precipitation in Qinghai from May to October

利用1981—2015年ERA-Interim再分析资料和青海省43个观测站气象资料,采用气象经验正交函数分解(EOF)、相关分析法及合成分析等方法,对青藏高原(以下简称高原) 5—10月地表潜热通量的时空分布特征及其与青海省同期降水之间的关系进行了分析,结果表明:(1)高原地表潜热通量第1模态空间分布主要呈现高原东西部变化不一致的特征,青海东北部、高原西部和南部地区表现为正异常,其余地区为负异常;第1模态时间系数呈现显著下降趋势,并以2001年为界,前正后负,表明青海东北部及高原西部和南部地表潜热通量在2001年以前(后)增加(减少)。(2)高原地表潜热通量与青海省东北部降水存在显著的负相关关系,当高原地表潜热通量增加(减少)时,青海省东北部降水减少(增加)。(3)将通过0. 1显著性检验的区域作为研究二者之间关系的关键区(35. 0°～38. 5°N,98°～103. 0°E),以1个标准差为依据,挑选潜热通量高值年和低值年。结果表明,关键区内地表潜热通量在近35 a表现为显著下降的趋势,潜热通量高值年关键区降水增加,潜热通量低值年关键区东北部降水减少,其余地区降水增加,且在南部存在大于60 mm正异常中心;在潜热通量高(低)值年,关键区位势偏低(高),风速偏大(小),关键区南部水汽辐合较弱(强)。通过分析100 hP a南亚高压中心强度与300 hP a温度场,在地表潜热通量异常偏高(低)年,南亚高压强度略低(高),300 hP a暖中心略低(高),且南亚高压初上(撤离)高原较早。

In this study,the ERA-Interim reanalysis data and the observation data from 43 meteorology stations in Qinghai Province from 1981 to 2010 were used.The purposes of the study were to analyze the spatial and temporal distribution characteristics of the surface latent heat flux(short for slhf)over the Qinghai-Tibetan Plateau and its relationship with precipitation in Qinghai from May to October using the method of EOF(Empirical orthogonal functions),correlation analysis and composite analysis.The result showed that:(1)The spatial distribution of first order mode of slhf was different in the eastern and western regions of the plateau,the anomaly was positive in northeast Qinghai and the western and southern regions of the plateau but negative in other areas.The time coefficient of first order mode was in a significant downward trend,it was positive before 2001 but negative after that,which revealed that the slhf in northeast Qinghai and the western and southern parts of the plateau increased before 2001 but decreased after that;(2)There was a significant negative correlation between the slhf over the plateau and the precipitation in northeast Qinghai Province.When the slhf over the plateau was increased(or decreased),the precipitation in northeast Qinghai was reduced(or increased);(3)The area where it passed the significance test of 0.1 was regarded as the key area(35.0°-38.5°N,98°-103.0°E)to study the relationship between the two,and 1 standard deviation was used to select the high-value years and low-value years of slhf.The results revealed that the slhf in the key area in recent 35 years was in a significant decrease trend,the precipitation in the key area was increased in the high-value years of slhf,it was decreased in the northeastern part of the key area but increased in other regions,and there was a 60 mm positive anomaly center in the south;(4)In the high-value(or low-value)years of slhf,the potential of the key area was low(or high),the wind speed was high(or low),and the water vapor convergence was weak(or strong)in the south of the key area.Analysis of the intensity of the 100 h Pa South Asian High Center and the 300 h Pa temperature field revealed that the intensity of the South Asian High and the 300 hPa warm center were slightly lower(or higher)in the years when the slhf was abnormally high(or low),and the establishment(or retreat)of South Asian High was earlier.