南亚高压南北位移对亚洲季风区上对流层-下平流层区域大气成分分布的影响

Influence of the South-North Displacement of South Asia High on the Distribution of Atmospheric Composition in the Upper Troposphere-Lower Stratosphere over the Asian Monsoon Region

利用欧洲中期数值预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)提供的ERA-Interim再分析资料和Aura卫星上微波临边探测器MLS(Microwave Limb Sounder)提供的大气成分资料,研究了南亚高压的南北位移与亚洲季风区上对流层-下平流层区域水汽、一氧化碳(CO)和臭氧(O3)分布之间的关系。结果表明:(1)在215 hPa,南亚高压偏北时,水汽和CO在伊朗高原、青藏高原东北部至中国东北地区比偏南时高,仅在孟加拉湾以北和中南半岛北部比偏南时低。在100 hPa,偏北时南亚高压控制范围内水汽比偏南时高,而CO则是偏南时偏高。下平流层68 hPa,南亚高压控制范围内偏北时的CO弱于偏南时。O3在不同高度的分布与CO相反。(2)南亚高压偏北时,高压西部及北部对流比偏南时强,30°N以北南亚高压强度也较强,将对流层低层空气向上输送,导致上对流层215 hPa的水汽和CO在伊朗高原、青藏高原东北部至中国东北地区比偏南时高,而O3被稀释成为低值中心。(3)在100 hPa,南亚高压偏南时,反气旋环流南部的位势高度偏高,同时反气旋环流中心垂直上升运动较强,将含丰富的水汽和CO以及低浓度O3的空气向上输送,导致100 hPa上CO的高值中心浓度比偏北强,O3的低值中心浓度比偏北低。而偏南时南亚高压控制区内对流层顶温度偏低,在“冷凝脱水”作用下,偏南时的水汽反而比偏北低。(4)100 hPa南亚高压偏南时强度比偏北弱,“围困”作用也弱,在上升运动作用下,将更多的高浓度水汽和CO以及低浓度O3空气向上输送到68 hPa。

Using the ERA-Interim reanalysis data provided by the European Centre for Medium-range Weather Forecasts(ECMWF)and the atmospheric composition data provided by the Microwave Limb Sounder(MLS),the impacts of the south-north displacement in the South Asia High(SAH)on the distribution of water vapor,ozone(O3)and carbon monoxide(CO)in the Upper Troposphere Lower Stratosphere(UTLS)of the Asian monsoon region are analyzed.The results show that:(1)Water vapor and CO at 200 hPa are higher over the Iranian plateau,northeastern Tibetan Plateau and northeastern China during northward displaced SAH(NSAH)than those during southward displaced SAH(SSAH),except in the north of the Bay of Bengal and in the northern part of the Indochina Peninsula.At 100 hPa,the water vapor in the SAH range during NSAH is higher than those during SSAH,while the CO is higher during SSAH than those during NSAH.At 68 hPa,CO in the SAH range during NSAH are weaker than those during SSAH.The distribution of ozone at different heights is roughly opposite to those of CO.(2)During NSAH the convection activities in the west and north side of SAH is stronger than those during SSAH and the intensity of SAH north of the 30°N is also stronger than those during SSAH.Stronger convection during NSAH leads to more lower-tropospheric air transporting upwards,resulting in the higher(lower)values of water vapor and CO(O3)at 215 hPa over the Iranian plateau and Qinghai-Tibet Plateau to the northeastern China than those during SSAH.(3)At 100 hPa,the geopotential height in the south of the anticyclonic circulation is higher and the vertical ascending motion is stronger during SSAH than those during NSAH.Thus,tropospheric air with high concentration water vapor and CO and low concentration ozone are transported upward.As a result,the concentration of 100-hPa CO(O3)at 100 hPa is stronger(lower)during SSAH than that during NSAH.For the water vapor,the tropopause temperature in the SAH area is lower during SSAH.Effected of“condensation and dehydration”,the 100-hPa water vapor in the SSAH is lower than that in the SSAH.(4)The“trapping”effect during SSAH is weaker than those during NSAH,causing the stronger ascending motion and transporting more air with higher(lower)concentrated CO(O3)to 68 hPa.