Characterization of smoke and dust episode over West Africa: Comparison of MERRA-2 modeling with multiwavelength Mie-Raman lidar observations

Abstract

Observations of multiwavelength Mie-Raman lidar taken during the SHADOW field campaign are used to analyze a smoke-dust episode over West Africa on 24-27 December 2015. For the case considered, the dust layer extended from the ground up to approximately 2000ĝ€m while the elevated smoke layer occurred in the 2500-4000ĝ€m range. The profiles of lidar measured backscattering, extinction coefficients, and depolarization ratios are compared with the vertical distribution of aerosol parameters provided by the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The MERRA-2 model simulated the correct location of the near-surface dust and elevated smoke layers. The values of modeled and observed aerosol extinction coefficients at both 355 and 532ĝ€nm are also rather close. In particular, for the episode reported, the mean value of difference between the measured and modeled extinction coefficients at 355ĝ€nm is 0.01ĝ€kmĝ'1 with SD of 0.042ĝ€kmĝ'1. The model predicts significant concentration of dust particles inside the elevated smoke layer, which is supported by an increased depolarization ratio of 15ĝ€% observed in the center of this layer. The modeled at 355ĝ€nm the lidar ratio of 65ĝ€sr in the near-surface dust layer is close to the observed value (70ĝ€±ĝ€10)ĝ€sr. At 532ĝ€nm, however, the simulated lidar ratio (about 40ĝ€sr) is lower than measurements (55ĝ€±ĝ€8ĝ€sr). The results presented demonstrate that the lidar and model data are complimentary and the synergy of observations and models is a key to improve the aerosols characterization.