Spatiotemporal characteristics of the atmospheric boundary layer height over India deduced from multi-platform measurements and re-analyses data

Abstract

Atmospheric Boundary Layer Height (Zi), a key characteristic of the boundary layer, is a crucial parameter in modelling cloud formation, weather, and air quality. Hence, its accuracy is vital for reliable modelling and forecasting. In this study, India’s first regional reanalysis dataset, the Indian Monsoon Data Assimilation and Analysis (IMDAA), is validated against multi-platform measurement datasets. It is found that Zi from IMDAA is in good agreement with radiosonde and satellite observations and performs better than the other reanalysis datasets. However, IMDAA significantly underestimates Zi (< 100 m) during December over humid subtropical climatic regions like Jammu and Gorakhpur, possibly due to high negative net radiation, overestimated cloud cover, and inaccuracies in surface energy partitioning in IMDAA. For the first time, a comprehensive characterization of the daily maximum Zi (referred to as Zi, max) is performed. The analysis of diurnal and seasonal variations of Zi, max revealed that the atmospheric boundary layer is fully developed (deepest) at ~ 15:30 IST across all seasons over most of the Indian region. Spatially, Zi, max reached its highest value of ~ 4500 m during the pre-monsoon season over central India. But during the monsoon, it reduces to ~ 2500 m, and the peak location gets shifted to northwest India. In addition, we report that it is the sensible heat flux that primarily drives the Zi, max rather than the Bowen ratio over central India. These results have large implications for Zi dynamics in regional numerical weather, climate, and air quality simulations.