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Abstract:
The interplay of the Indian Monsoon and the Himalayas is vital to many climatological aspects of the Himalayan foothill and foreland regions. A unique climate feature in the Himalayan foothill and foreland regions is a bi-modal diurnal cycle of precipitation with high rainfall amounts in the afternoon and around midnight. The reason for this nighttime precipitation maximum is not yet fully understood, and current climate models and also reanalyses do not represent the regions’ diurnal precipitation cycle. Nevertheless, estimating realistic spatiotemporal precipitation patterns is crucial for the climate community (e.g., for impact modelling). This study reviews discussions in the literature, available observational findings, and simulation results with the regional climate models (RCM) COSMO-CLM & ICON_CLM. Our simulations indicate that the models are not able to recover the nighttime’s precipitation behaviour with currently typical horizontal RCM grid-spacings (e.g., 10 or 50 km), but they can do so with convection-permitting grid-spacing (~3 km), which sufficiently resolves the relevant and diverse orographic thermal winds together with the moist monsoonal flow characteristics in the area.
