Dynamics of convective clouds near and below the lifting condensation level over a semi-arid Western-Indian region

The lifting condensation level (LCL) is a key parameter in estimating the convective cloud base height (CBH) and plays a crucial role in various meteorological processes. Under typical atmospheric conditions, the CBH coincides with or is positioned above the LCL. This study investigates the occurrence of clouds forming below the LCL over Ahmedabad, a semi-arid region in Western India, during 2022-2024. An analytical LCL formulation, derived from surface temperature and relative humidity, showed minimal bias compared to established empirical formulas when validated against radiosonde data. Convective clouds near the LCL are most frequent during the monsoon season. However, during the post-monsoon and winter months, anomalous cloud formations below the LCL were observed, with a mean CBH of 1044 +/- 135 m, predominantly between 0600 and 1200 UTC. These lowlevel clouds were associated with a strong thermal inversion below the LCL, occurring under surface temperatures ranging from 24 degrees C to 37 degrees C and relative humidity levels between 17 % and 49 %. The surface sensible heat flux during these clouds' occurrence was lower than that observed for clouds forming near the LCL but comparable to clear-sky conditions. Conversely, the surface latent heat flux was higher than in clear-sky conditions but lower than in cases where clouds formed near the LCL, averaging 147 +/- 74 W/m2. These findings highlight the role of thermodynamic stability and surface heat fluxes in modulating cloud formation processes in semi-arid environments. Improved understanding of clouds forming below the LCL is essential for enhancing weather prediction models and refining convective parameterization schemes in numerical weather and climate models, particularly in arid and semi-arid regions where cloud development significantly influences regional climate variability.