ESTIMATES OF THE WATER-VAPOR BUDGET OF THE STRATOSPHERE FROM UARS HALOE DATA

The water vapor budget of the stratosphere is diagnosed from correlati on studies of the UARS Halogen Occultation Experiment sunset measureme nts of CH4 and H2O in the middle and upper stratosphere, where the cor relations are most significant and highly negative. Analyses were cond ucted for the years 1992-1994 using the methods of (1) linear regressi on and (2) deterministic differences (or variances of the data). It is assumed that there is conservation of total hydrogen according to a m ethane oxidation chemical mechanism. Results consist of the zonal mean seasonal distributions of the chemical yield of H2O molecules from ea ch molecule of CH4 (or the beta profile) and an estimate of the annual average value of H2O that enters the stratosphere from below (or [H2O ](e)), presumably at the tropical tropopause. Average seasonal beta va lues range from 1.6 to 2.4, and their zonal mean patterns are in good agreement with the theoretical model distribution of LeTexier et al., especially for the upper stratosphere. The range for annual average [H 2O](e) is 2.9 to 3.4 parts per million by volume (ppmv). When adjusted upward by 10% due to known negative biases of about 5% in both the mi dstratospheric CH4 and the H2O data, [H2O](e) becomes 3.2 to 3.7 ppmv and is more consistent with averages of in situ measurements of water vapor at low latitudes of the lower stratosphere. We also find coheren t patterns in the seasonal estimates of zonal average water vapor yiel d that are related to (1) the downward descent of air at winter polar latitudes, (2) the presence of dehydrated air at high latitudes of the southern hemisphere lower stratosphere, and (3) the ascent and relati ve isolation of the annual (January) minimum in tropical water vapor.