Characteristics of Updrafts and Downdrafts in the Rain-shadow region during September (2019)

Abstract

The collocated observations from the microwave radiometer profiler and wind profiler from the rain-shadow region of Western Ghats (Tuljapur) is used to study the characteristics of mass-flux and its dependencies on convective and dynamic characteristics. Various key parameters investigated are the characteristics of low- level jet, convective vertical velocity, area fraction and mass-flux profiles during the month of September from the monsoon period of 2019. While the updrafts increase in magnitude with altitude, downdrafts show increased magnitudes at lower altitudes. Downdrafts show significantly larger area fraction and mass-flux compared to updrafts attributing to the dominant stratiform regions with light precipitation, covering a large area. Downdrafts at lower altitudes show a clear diurnal variation, unlike updrafts which remain almost uniform throughout the day. The convective profiles are sensitive to environmental conditions. Strong updrafts are observed in humid and weak convective inhibition (CIN) conditions. Downdrafts are driven by precipitation loading and are strongly modulated by the presence of moisture and liquid water present in the atmospheric column. The presence of the strong low-level jet in this region generates a sheared environment for convection which affects the area fraction of the drafts. And also the strong jet favours intense updrafts at higher altitudes and the weak jet favours intense downdrafts at lower altitudes. The observations averaged over time can represent the convective profiles of a GCM- size grid that can be further used for the evaluation of mass-flux schemes of parameterisations in the models.