Sensitivity of Radiative Fluxes to Aerosols in the ALADIN-HIRLAM Numerical Weather Prediction System

• Published in: Atmosphere Vol. 11; no. 2; p. 205
• Main Authors: Rontu, Laura, Gleeson, Emily, Martin Perez, Daniel, Pagh Nielsen, Kristian, Toll, Velle
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2020
• Subjects: Aerosol effects; Aerosol optical depth; Aerosol optical properties; Aerosols; aladin-hirlam; Atmosphere; Atmospheric particulates; Black carbon; Black carbon aerosols; Broadband; Broadband radiation; cams; Clear sky; Climate; Climate models; direct radiative effect; Distribution; Dust storms; Fluxes; Geographical distribution; Heating; Loads (forces); Long wave radiation; musc; Numerical weather forecasting; nwp; Optical properties; Precipitation; Prediction models; Radiation; Radiation-cloud interactions; Radiative transfer; Real time; Sensitivity; Short wave radiation; Vertical distribution; Wavelength; Weather; Weather effects; Weather forecasting
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos11020205

The direct radiative effect of aerosols is taken into account in many limited-area numerical weather prediction models using wavelength-dependent aerosol optical depths of a range of aerosol species. We studied the impact of aerosol distribution and optical properties on radiative transfer, based on climatological and more realistic near real-time aerosol data. Sensitivity tests were carried out using the single-column version of the ALADIN-HIRLAM numerical weather prediction system, set up to use the HLRADIA simple broadband radiation scheme. The tests were restricted to clear-sky cases to avoid the complication of cloud–radiation–aerosol interactions. The largest differences in radiative fluxes and heating rates were found to be due to different aerosol loads. When the loads are large, the radiative fluxes and heating rates are sensitive to the aerosol inherent optical properties and the vertical distribution of the aerosol species. In such cases, regional weather models should use external real-time aerosol data for radiation parametrizations. Impacts of aerosols on shortwave radiation dominate longwave impacts. Sensitivity experiments indicated the important effects of highly absorbing black carbon aerosols and strongly scattering desert dust.