Dynamics of mid-level stratiform clouds over the semi-arid regions of Western India: a post-monsoon case study

Abstract

Stratiform clouds, which form under stable atmospheric conditions, play a crucial role in negative cloud radiative forcing. Utilizing a combination of ground-based observations, satellite data, and reanalysis datasets, the study investigates the formation of stratiform clouds over Udaipur (24.58° N, 73.71° E, 598 m a.m.s.l) compared to Ahmedabad (23.02° N, 72.57° E, 56 m a.m.s.l) in the semi-arid region of Western India during the post-monsoon period. Ground-based Lidar observations indicated consistent cloud occurrences between 2 and 4 km over Udaipur during post-monsoon. Conversely, cloud occurrence over Ahmedabad is found to be lower despite the city having higher levels of columnar water vapor during this period. During the post-monsoon period of 2022–2023, the total cloud occurrence between 2 and 4 km altitude over Udaipur (~ 4.24%) was approximately double that observed over Ahmedabad (~ 2.02%). This disparity is linked to higher relative humidity near the 750 hPa level over Udaipur, sustained by surface moisture lifted to the 2–4 km range. Vertical moisture transport is facilitated by persistent low-level convergence at ~ 950 hPa and upper-level divergence at ~ 750 hPa, creating favorable conditions for vertical air motion and mid-level cloud formation. This study explores the influence of surface water bodies, orography, and local meteorological conditions on cloud dynamics in semi-arid urban areas. The insights from this study into cloud formation and atmospheric dynamics over the semi-arid Western-Indian region can contribute to improving regional weather forecasting.