珠峰北坡绒布河谷地面风场变化的比较研究

Analysis of Surface Wind in the Rongbuk Valley on the Northern Slope of Mt. Qomolangma

利用2007年6月强化观测实验期间获得的大气观测资料和同时期的NCEP/NCAR大尺度再分析资料,结合2006年同期的分析结果,进一步研究了珠峰北坡绒布河谷地区的地面风场状况及其对南亚夏季风的响应,并与2006年的结果进行了比较。结果表明,2007年6月绒布河谷地区的风场也存在强弱变化,其逐日变化也与南亚夏季风指数有一定关系:在绒布河谷弱风期间,南亚夏季风强盛,在孟加拉湾和阿拉伯海地区形成的强烈涡旋可以把暖湿气流向西北方向输送,从而在河谷地区形成温度和湿度高值;在局地强风期间,南亚夏季风季风指数变化较大,此时绒布河谷地区的风场变化对季风的响应很小,可能主要为大气热力驱动。比较2006年和2007年的观测结果表明,南亚夏季风可以通过改变局地辐射和热力状况的改变而影响珠峰北坡绒布河谷地区地面环流的变化,但其影响程度随季风的强弱可能有所不同。

Using the observation data obtained in the Rongbuk Valley in June 2007 and the real-time NCEP/NCAR reanalysis data, the variation of surface wind and its possible responses to the South Asian summer monsoon （SASM） were analyzed. There also exist strong and weak surface wind periods in 2007, however, which is not so clearly related to the SASM index as that in 2006. In the weak surface wind （strong SASM） period, the strong low pressure prevailed in the Bangladeshi Bay and Arabian Sea regions, which could bring the warm-wet air to the Rongbuk Valley and form high values there. However, the surface wind in the Rongbuk Valley has a little response to the variation of SASM in the strong wind period, which could be mainly driven by the local thermal and radiation processes, From the observation data obtained in 2006 and 2007, we think that the SASM could have impacts on the local circulation in the Rongbuk Valley through the changes of local thermal and radiation conditions, however, the impacts varied with the strength of monsoon.