Moisture transport enhanced by the nocturnal low-level jet in association with the passage of a monsoon depression over the Indian subcontinent

Abstract

Characteristics of moisture transport associated with a monsoon depression (MD) formed over the Bay of Bengal and later moved westward over central India are presented. The investigation is carried out mainly using the Weather Research and Forecast (WRF) cloud-resolving model simulations and the vertically integrated water vapor transport (IVT) to assess the path and features of the moisture transport. The model performance evaluation is carried out using micrometeorological and microwave radiometer observations from the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX). The results indicate that the strengthened LLJ during the nocturnal periods helps to enhance the moisture convergence in the lower troposphere and thus the rainfall, both before the formation of MD as well as during its passage over land. The moisture budget over a selected region along the path of the MD gave further insights on the moisture convergence, associated precipitation and related features during the study period. The analyses using IVT and LLJ strength are illustrated to be useful in identifying areas of intense convection.