Empirically-Derived Parameterizations of the Direct Aerosol Radiative Effect based on ORACLES Aircraft Observations [post]

Sabrina P. Cochrane, K. Sebastian Schmidt, Hong Chen, Peter Pilewskie, Scott Kittelman, Jens Redemann, Samuel LeBlanc, Kristina Pistone, Meloë Kacenelenbogen, Michal Segal Rozenhaimer, Yohei Shinozuka, Connor Flynn (+5 others)
2020 unpublished
Abstract. This work establishes an observationally-driven link from mid-visible aerosol optical depth (AOD) and other scene parameters to broadband shortwave irradiance (and by extension, the direct aerosol radiative effect, DARE), based on observations from the 2016 and 2017 field campaigns of ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS). Specifically, this is done by two parameterizations, one spanned by the mid-visible AOD and scene albedo below the aerosol layer,
more » ... d another one with a third input, the mid-visible aerosol single scattering albedo (SSA). These parameterizations build on the earlier concept of radiative forcing efficiency, which describes the dependence of DARE on the AOD, and extend it to make the dependence on the other two scene parameters explicit. The parameterizations are founded on 9 cases from the campaigns, for which we retrieve the spectral aerosol properties of SSA and asymmetry parameter (g) directly from the radiative fluxes, based on the method presented in Cochrane et al. (2019). These properties are used as the basis of the parameterizations, capturing the natural variability of the study region as sampled. The majority of the case-to-case variability within the ORACLES DARE dataset is attributable to the dependence on AOD and scene albedo. This is captured by the first parameterization, which is advantageous when satellite retrievals provide only limited information such as AOD and scene albedo. However, the second parameterization explains even more of the case-to-case variability by introducing the mid-visible SSA as third parameter. For both parameterizations, we provide the necessary coefficients, uncertainties, and code required for the user to reconstruct the parameterization for their use.
doi:10.5194/amt-2020-137 fatcat:7w6bpttlgzdolb2iqmr247eozq