Water Vapor Distribution Characteristics In UTLS Region And The Discussion Of Water Vapor Transport And Dehydration Mechanisms In Asian Summer Monsoon Region

According to water vapor, ice water content (IWC), and temperature data from MLS, the distribution characteristics of water vapor in the upper troposphere and lower stratosphere (UTLS) and the main dehydration mechanisms have been presented. Water vapor and IWC measurements are relatively coincident well with the OLR at215hPa. At147hPa and above, however, the correlation is not so well, linked with the height of deep convections outflow at that level. Also, a north-west trend has been observed, determined by the anticyclone above the Asian Summer Monsoon (ASM) region. Deep convections in the ASM region loft water vapor in the upper troposphere, where confinement of water vapor by the anticyclone occurred, and then water vapor is transported to the stratosphere.Due to more concern about gas phase in the previous studies, we now consider solid phase as well, and add solid ice water content into the water vapor by reconciling the unit of ice water content. Total content in the ASM is larger than North American Monsoon (NAM) region at all levels. At lower level, water vapor contributes more for the mix content, while at higher level, IWC is about the same contribution with water vapor to the mix content.Different probability distributions at147hPa and100hPa of water vapor indicate different dehydration mechanisms. The peak probability of water vapor around west pool in the boreal winter is small compared to other regions, caused by low temperature at that time. The long-tail distribution around Tibet Plateau at147hPa displays a strong convective influence. The ice water content at the two levels both distribute high probabilities in the small values, influenced by depleting water vapor on crystal growth and sedimentation.We divide two temperature ranges for the correlation with IWC and water vapor. Cold region presents a "vertical-like" distribution, while warm region a "lateral-like" one. TP and WP both display an anti-correlation between IWC and water vapor at100hPa. IP and WP shows positive one between water vapor and temperature. In addition, IP shows anti-correlation with water vapor and IWC, while WP the positive one.Water vapor and temperature shows weak correlation in warm pool. The other three regions display an "L-shape" distribution at147hPa. At100hPa, these regions do not present expected positive correlation, but a triangular distribution characteristic. In addition, there are more observation results which cannot be explained by what we know now, which requires more observations and studies.In sum, water vapor distribution is influenced by deep convections in the upper troposphere, while is mainly controlled by temperature near the tropopause, which is corresponding to the two main dehydration mechanisms. Still, there are myriad questions in UTLS region, especially in the ASM region to be solved.