A regional modeling study on aerosol–radiation interaction during an unprecedented dust scenario
摘要
Using the regional model RegCM, the current study investigated the regional influence of dust-radiative effects during an unusual scenario of record-breaking dust storms in the 2018 pre-monsoon months. The simulated results exhibited excellent agreement with various observations and reanalysis datasets, indicating the model’s reasonable capability to mimic aerosol and meteorological parameters. The primary dry regions and the dust transportation paths across the Arabian Sea and the Indo-Gangetic Plain are the areas most affected by dust, with the Thar Desert region experiencing the highest overall load (1800–2200 mg m−2). In high albedo areas, dust particles switched the direct radiative forcing (DRF) sign from negative to positive (up to 25 W m−2) at the top of the atmosphere. Contrarily, the opposite responses of dust at shortwave (cooling) and longwave (heating) spectra offset each other and eventually lead to a net negative DRF (from − 10 to − 30 W m−2) at the surface. However, positive DRF (~ 30 W m−2) dominated over negative DRF (− 10 to − 25 W m−2), resulting in substantial atmospheric heating (0.2–0.6 K day−1). Although dust reduced cloud cover in the mid-troposphere through the semi-direct effect, it simultaneously encouraged stronger updrafts, lifting the extra moisture to even higher latitudes. Meanwhile, increased near-surface temperature (0.6–1.2 °C) and subsequent decline in surface pressure (− 0.6 hPa) over a widespread region further strengthened southwesterly winds and increased large-scale convergence. Thus, the intensified ‘Elevated Heat Pump’ effect substantially enhanced upward moisture transport (40–60 kg m−1 s−1), facilitating the production of deeper clouds and raising convective rainfall over the ocean and adjacent coastal regions.