Study On The Distributions, Variations And Climate Impacts Of The Water Vapor And Methane In Stratosphere

Stratosphere is an important part in climatic system. Although the changes of ozone and carbon dioxide are the principal factor affecting on the stratospheric temperature change, water vapor and methane also contribute to the change of stratosphere temperature. Because they are the important greenhouse gases that participate in the radiation, chemistry and dynamics process in stratosphere, so the study of water and methane has important scientific significanceIn this thesis, the methods including data analysis and numerical simulation are used to analyze the distribution and variation of H2O and CH4 in stratosphere and in the basis, their distribution and variation over China (especially over Qinghai-Xizang plateau) are also studied; And the mechanism of H2O and CH4 QBO in tropic stratosphere are discussed; The influence of H2O and CH4 change on stratosphere temperature are simulated using the NCAR interactive chemical dynamical radiative two dimensional model (SOCRATES), and the impact mechanism are also discussed.The following results and new recognition have been obtained.Firstly, The characteristic of vertical distribution of H2O in stratosphere and in mesosphere shows that the H2O mixing ratio decreases from the upper troposphere to tropopause quickly and reaches a minimum near the tropopause (the minimum is called as"hygropause"); and then it increases with height in the lower-middle stratosphere ,while it is disturbed significantly in the upper stratosphere and lower mesosphere; it decreases with altitude again and reaches another minimum near mesopause. The characteristic of vertical distribution of CH4 shows that it always decreases with height above 100hPa The meridional distribution shows that the bottom of tropic stratosphere is relatively"dry", so-called mixing barriers are seen near 20~30°N-S in the lower stratosphere,H2O mixing ratio is relatively less in Antarctic polar vortex during winter-spring. The seasonal variations of the meridional distributions of H2O and CH4 are distinctly in the middle-upper stratosphere. The spatial distribution features of CH4 are approximate mirror images of those in H2O in the most part of stratosphere, except in the tropical tropopause and Antarctic polar vortex. Usually, the high values of CH4 mixing ratio correspond to the low values of H2O mixing ratio, and the low values of CH4 mixing ratio correspond to the high values of H2O mixing ratio. Both H2O and CH4 meridional distributions in the mesosphere appear approximately opposite pattern in DJF and JJA. Longitudinal gradients of the two trace gases near 30°N in JJA are all small in the lower-middle stratosphere, but they are large in the upper troposphere and mesosphere. The H2O and CH4 distributions are strongly influenced by atmospheric dynamical and chemical processes, and H2O is also influenced by low temperature at tropic tropopause and in Antarctic polar vortex.Secondly, The long-term variations of H2O during 1992~2005 were analyzed, the results show that H2O mixing ratio appears obvious decreasing trend in the lower stratosphere, it appears increasing trend before the mid-1990 and decreasing trend after mid-1990 in the middle-upper stratosphere. The variable trends of CH4 mixing ratio are opposite with those of H2O in the upper stratosphere. CH4 mixing ratio presents slow increasing trend in the middle stratosphere. The variations of CH4 in both lower and upper stratosphere appear approximately opposite trends.The long-term variations of H2O and CH4 in both tropics and extratropical regions are approximately consistent,but there are some difference in variable extent in different latitude zones. The variable trends of O3 are approximately opposite with those of H2O and almost consistent with those of CH4 in the upper stratosphere, while the trends of O3 are approximately opposite with those of CH4 in the extratropical regions of lower stratosphere. Both H2O and temperature variable trends are almost consistent in the lower stratosphere, but they are opposite in the middle-upper stratosphere. Since the amount of H2O in lower stratosphere is very sensitive to the tropopause temperature, the obvious decreases of H2O near tropical tropopause during 1992~2005 are tightly related with decreases of tropical tropopause temperature. The long-term variations of residual meridional circulation in stratosphere strongly affect the variations of H2O and CH4.Thirdly, The vertical distribution of H2O and CH4 over Qinghai-Xizang plateau were analyzed and compared with those of other regions in the same latitude zone as well as equator, the results show that the amount of H2O transported to the upper troposphere and lower stratosphere over Qinghai-Xizang plateau in summer is more. Downward air motion over Qinghai-Xizang plateau is stronger in winter, so air in the upper troposphere is drier, and CH4 contents reduce in winter in the upper troposphere and lower stratosphere. Qinghai-Xizang plateau is an active and important area for stratosphere-troposphere exchange. The long-term variations of H2O over China (Qinghai-Xizang plateau) are approximately consistent with those of H2O in tropics and extratropical regions. The long-term variations of CH4 over China (Qinghai-Xizang plateau) are also approximately consistent with those of CH4 in tropics and extratropical regions in middle-upper stratosphere, while they have some difference in lower stratosphere.Fourthly, Data analysis results show that the vertical structure of H2O QBO in tropical stratosphere can be divided into three layers which are 8-1hpa,30-8hPa and 100-30hPa,and the QBO amplitude in 8-1hPa is larger than that of other two layers, and H2O QBO transport upward in 100-30hPa. The vertical structure of CH4 QBO in tropical stratosphere can be divided into two layers which are 10-1hpa and 20-10hPa, and the QBO amplitude in 10-1hPa is larger than that in 20-10hPa,and CH4 QBO transport downward below 1hPa.The diagnosis and simulations show that the H2O QBO in tropical stratosphere is caused by the coupled sub-dynamical, thermal and chemical process that were forced by the zonal wind QBO. H2O QBO in 8-1hPa was arouse by dynamical transfer, and both dynamical transfer and chemical action driven by temperature fluctuation together arise H2O QBO in 30-10hPa, and the temperature fluctuation in freezing layer and dynamical transfer together arise H2O QBO in 30-10hPa.The tropical tropopause temperature QBO also contribute to H2O QBO near tropospause. The CH4 QBO in tropical stratosphere is mostly produced by dynamical transfer due to the change of the residual circulation.Fifthly, The H2O climatic effect in stratosphere is simulated by SOCRATES, the results show that H2O long wave radiative cooling rate contributes 10-20 percentage of total cooling rate, and its long wave radiative cooling is obvious in stratosphere. When H2O content in stratosphere increases, the air temperature in stratosphere will decreases and the temperature decrease is larger in both high latitudes and upper stratosphere; When H2O content in lower stratosphere decreases, the air temperature in the middle-lower latitudes below 30km will increases. The photochemistry reaction relating with H2O increase will result in O3 decrease that take on very important action to temperature variations in the upper stratosphere. Radiative cooling rate would decreases and wouldn't hold cooling action because of temperature descend in the upper stratosphere, and then temperature descend result from O3 decrease. Long wave radiation increase produced by H2O content increase will result in temperature descend in the lower-middle stratosphere. The temperature variation is mainly dominated by radiation process in the lower stratosphere, and the effect of both radiative process and dynamical process on temperature descend are all important in the middle-upper stratosphere. The dynamical process at middle-high latitudes in the north hemisphere not only affect on temperature variation but also O3 content of these areas.O3 variation brought by H2O variation significantly acts on stratospheric temperature variation. The variations of residual meridional circulation are larger at arctic in January, and it influences temperature variation here strongly. The variations of residual meridional circulation in April, July and October are about tenth of that in January.Sixthly, The simulations of CH4 climatic effect show that CH4 has cooling effect through long wave radiation process in the middle-upper stratosphere, but cooling effect is much smaller than that of H2O and it is ignored over 60km.When CH4 mixing ratio increases, H2O content in stratosphere and mesosphere will increase, and O3 content in the upper stratosphere and mesosphere will decrease, and O3 content in most stratosphere and troposphere will increase.CH4 increases will result in stratospheric and mesospheric cooling and troposphere warming, but this warming is slight and cooling is relatively strong. The reason of stratospheric cooling result from H2O content increase arouse by CH4 increase, and mesospheric cooling result from both H2O increase and O3 decrease arouse by CH4 increase.