Abstract
Abstract. Light-absorbing particles (LAPs) deposited on snow can decrease snow albedo and affect climate through snow-albedo radiative forcing. In this study, we use MODIS observations combined with a snow-albedo model (SNICAR – Snow, Ice, and Aerosol Radiative) and a radiative transfer model (SBDART – Santa Barbara DISORT Atmospheric Radiative Transfer) to retrieve the instantaneous spectrally integrated radiative forcing at the surface by LAPs in snow (RFMODISLAPs) under clear-sky conditions at the time of MODIS Aqua overpass across northeastern China (NEC) in January–February from 2003 to 2017. RFMODISLAPs presents distinct spatial variability, with the minimum (22.3 W m−2) in western NEC and the maximum (64.6 W m−2) near industrial areas in central NEC. The regional mean RFMODISLAPs is ∼45.1±6.8 W m−2 in NEC. The positive (negative) uncertainties of retrieved RFMODISLAPs due to atmospheric correction range from 14 % to 57 % (−14 % to −47 %), and the uncertainty value basically decreases with the increased RFMODISLAPs. We attribute the variations of radiative forcing based on remote sensing and find that the spatial variance of RFMODISLAPs in NEC is 74.6 % due to LAPs and 21.2 % and 4.2 % due to snow grain size and solar zenith angle. Furthermore, based on multiple linear regression, the BC dry and wet deposition and snowfall could explain 84 % of the spatial variance of LAP contents, which confirms the reasonability of the spatial patterns of retrieved RFMODISLAPs in NEC. We validate RFMODISLAPs using in situ radiative forcing estimates. We find that the biases in RFMODISLAPs are negatively correlated with LAP concentrations and range from ∼5 % to ∼350 % in NEC.
Highlights
Pure snow is the most strongly reflective natural substance at the surface of the Earth, and seasonal snow covers more than 30 % of the Earth’s land area (Painter et al, 1998)
Painter et al (2012a) successfully used the MODIS Dust Radiative Forcing in Snow (MODDRFS) model to retrieve surface radiative forcing by Light-absorbing particles (LAPs) in snow cover from Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data
We attempt to retrieve the radiative forcing by LAPs in snow across northeastern China (NEC) using MODIS datasets combined with the Snow, Ice, and Aerosol Radiation (SNICAR) model (Flanner et al, 2007, 2009) and the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model (Ricchiazzi et al, 1998); we estimate the uncertainties of radiative forcing from atmospheric correction and qualify the fractional contribution of each factor to the spatial variance of RFLMAOPDsIS
Summary
Pure snow is the most strongly reflective natural substance at the surface of the Earth, and seasonal snow covers more than 30 % of the Earth’s land area (Painter et al, 1998). Light-absorbing particles (LAPs), such as black carbon (BC), organic carbon (OC), and mineral dust, deposited on snow can effectively reduce snow albedo (Hadley and Kirchstetter, 2012; He et al, 2017, 2018; Li et al, 2016; Warren, 1982, 1984; Warren and Wiscombe, 1980) and enhance the absorption of solar radiation (Dang et al, 2017; Kaspari et al, 2014; Liou et al, 2011, 2014; Painter et al, 2012b). (2015) pointed out that widespread albedo decrease and the induced melting of Himalayan snow and ice Published by Copernicus Publications on behalf of the European Geosciences Union Ming at al. (2015) pointed out that widespread albedo decrease and the induced melting of Himalayan snow and ice Published by Copernicus Publications on behalf of the European Geosciences Union
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