青藏高原上空H2O和CH4的分布和变化趋势分析

采用UARS卫星1993—2004年卤素掩星试验的观测资料(HALOE),分析了青藏高原(下称高原)上空大气中H2O和CH4的分布和季节变化,也与同纬度其它地区作对比,找出它们的差异,并分析了H2O和CH4的多年变化趋势。结果表明:高原上空H2O混合比在对流层上层随高度迅速减少,在对流层顶和平流层底达到极小值,平流层里水汽混合比随高度增加。高原上空CH4混合比从140 hPa直至1 hPa随高度递减。在对流层上部和平流层下部H2O和CH4混合比季节差异最明显。高原上空H2O和CH4混合比与同纬度带其它地区相比有不少差异,这种差异在对流层上部和平流层下部更明显。分析还表明:高原上空对流层上部和平流层下部H2O和CH4的分布明显受到高原热力作用引起的垂直运动的影响,高原区域是平流层和对流层交换的活跃区。平流层中上层H2O和CH4的关系很密切,其原因主要是在平流层中上层CH4很容易被氧化成H2O。趋势分析表明,在对流层顶附近,水汽在1993—2004年呈下降趋势,而CH4在1998年以前和2001年以后也呈下降趋势;平流层中层1993—2000年H2O混合比呈增加趋势,CH4呈下降趋势,2000—2004年H2O混合比呈下降趋势,而CH4呈增加趋势。

Study on H2O and CH4 Distributions and Variations over Qinghai-Xizang Plateau Using HALOE Data

The H2O and CH4 data observed by HALOE in UARS satellite from 1993 to 2004 are used to analyze their distributions and variation features in stratosphere over Qinghai-Xizang Plateau,and compare with those in the same latitudes.Finally the trends of the H2O and CH4 in stratosphere over Qinghai-Xizang Plateau are also analyzed.The results show that the H2O mixing ratio decreases with height in upper troposphere quickly reaches a minimum near the tropopause and the bottom of stratosphere;and then it increases with height in stratosphere.The characteristic of vertical distribution of CH4 shows that it always decreases with height from 140 hPa to 1 hPa.The mixing ratio of H2O and CH4 in summer is higher than that in winter in upper-troposphere and lower-stratosphere.There is obvious difference between the mixing ratio of H2O and CH4 over Qinghai-Xizang Plateau and those over the same latitudes,especially in upper-troposphere and low-stratosphere.Vertical motion caused by the thermodynamics of the Qinghai-Xizang Plateau influences the distribution of H2O and CH4 significantly,and troposphere and stratosphere exchange is active over Qinghai-Xizang Plateau.Relation of H2O and CH4 is consanguineous in middle and upper stratospheres,this is because a principal source of stratosphere H2O is from the oxidation of CH4.The trend analyses show that the H2O mixing ratio decreased from 1993 to 2004 and CH4 mixing ratio decreased near tropopause before 1998 and after 2001.In middle stratosphere,the H2O mixing ratio increased before 2000 and then decreased after 2000;the CH4 mixing ratio decreased before 2000 and then increased after 2000.