Impact of Soil Moisture on Afternoon Convection Triggering Over the Tibetan Plateau Based on 1-D Boundary Layer Model

摘要

The impact of soil moisture conditions on the triggering of afternoon convection over the Tibetan Plateau (TP) was investigated by applying the convective triggering potential (CTP) and humidity index framework developed by Findell and Eltahir (2003a, https://doi.org/10.1175/1525-7541(2003)0042.0.co;2, 2003b, https://doi.org/10.1175/1525-7541(2003)0042.0.co;2) using a slab model. Atmospheric sounding observations from May to September from 2015 to 2019 from 16 sites were used for the diagnosis. The results showed that the thresholds of CTP and humidity index in the lower-layer atmosphere (HI_(low)) are distinct from other regions such as the United States and India, suggesting an easier triggering potential for the TP due to its high altitude induced lower air density and higher buoyancy. The convection over the TP is mainly affected by the atmospheric background. The percentages of soil moisture-controlled cases is close to 50% mainly located in the broadly central TP. In addition, the positive feedback is mainly located in the center of the TP. Negative feedback appears in the southwest of the TP. Soil moisture is the most critical factor for precipitation triggering in soil moisture-precipitation feedback, while wind speed can also have certain influences. The impact of soil moisture on different outcomes has no significant correlation with land surface elevation differences. Negative feedback in the southwest of the TP appeals to a necessary enhancement requirement for sounding observations in the western TP.