Particulate emissions can alter the physical and dynamical properties of cloud systems and, in turn, amplify rainfall events over orographic regions downwind of highly polluted urban areas. The Indo-Gangetic Plain, one of the most polluted regions of the world, is located upwind of the Himalayan foothills. The region, therefore, provides an opportunity for studying how aerosol effects, in connection with orographic forcing, affect extreme rainfall events. This study uses 17 years (2001–2017) of observed rain rate, aerosol optical depth (AOD), meteorological reanalysis fields and outgoing long-wave radiation to investigate high precipitation events on the foothills of the Himalayas. Composite analysis of all these co-located data sets for high precipitation events (daily rainfall > 95th percentile) is done to understand the inherent dynamics and linkages between the AOD and extreme events. Clear and robust associations are found between high precipitation events, high aerosol loading and high moist static energy values. Results show an average increase in AOD by 36 %, along with an average increase in low-level moist static energy (1000–850 hPa) by ≈ 1500 J kg⁻¹ inside the selected domain for high precipitation events. The finding highlights the crucial role of the aerosol direct radiative effect on high precipitation events over the Himalayan region.

Predictions of boundary layer meteorological parameters with accuracy are essential for achieving good weather and air quality regional forecast. In the present work, we have analyzed seven planetary boundary layer (PBL) parameterization schemes in a Weather Research and Forecasting (WRF) model over the Naples-Caserta region of Southern Italy. WRF model simulations were performed with 1-km horizontal resolution, and the results were compared against data collected by the small aircraft Sky Arrow Environmental Research Aircraft (ERA) during 7–9 October 2014. The selected PBL schemes include three first-order closure PBL schemes (ACM2, MRF, YSU) and four turbulent kinetic energy (TKE) closure schemes (MYJ, UW, MYNN2, and BouLac). A performance analysis of these PBL schemes has been investigated by validating them with aircraft measurements of meteorological parameters profiles (air temperature, specific humidity, wind speed, wind direction) and PBL height to assess their efficiency in terms of the reproduction of observed weather conditions. Results suggested that the TKE closure schemes perform better than first-order closure schemes, and the MYNN2 closure scheme is close to observed values most of the time. It is observed that the inland locations are better simulated than sea locations, and the morning periods are better simulated than those in the afternoon. The results are emphasizing that meteorology-induced variability is larger than the variability in PBL schemes.