Moisture variability over Indian monsoon regions observed using high resolution radiosonde measurements

The strong southwesterly and northeasterly flow in the lower troposphere during June–September (southwest, SW) and October–December (northeast, NE) monsoons bring substantial moisture into Indian sector. In this observational study, moisture variability over Hyderabad which is completely influenced by SW monsoon, Chennai influenced by NE monsoon and Gadanki influenced mostly by NE monsoon and partly by SW monsoon is studied. For the first time we have characterized the vertical variations in moisture based on background wind shear. The moisture variability over Indian monsoon region is compared with western Pacific and found that moisture variations are similar to western Pacific except during monsoon season. The correlation between the total precipitable water and water vapor mixing ratio is found maximum in boundary layer (BL) and decreases in free atmosphere. In general, the total precipitable water between the 850 and 600 hPa is found higher than between 900 and 850 hPa. To investigate the origin of air masses, back trajectories were calculated with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and found that wet events are originated from lower altitudes and from the Bay of Bengal. The moisture variability is found the same during both wet and dry spells within the BL but differ significantly in the mid-troposphere suggesting that the moisture above the BL plays significant role in maintaining the precipitation conditions over Indian region.