Intercomparison and Improvement of Two-Stream Shortwave Radiative Transfer Schemes in Earth System Models for a Uunified Treatment of Cryospheric Surfaces

TitleIntercomparison and Improvement of Two-Stream Shortwave Radiative Transfer Schemes in Earth System Models for a Uunified Treatment of Cryospheric Surfaces
Publication TypeJournal Article
Year of Publication2019
JournalThe Cryosphere
Volume13
Number9
Pages2325-2343
Date Published09/2019
Abstract / Summary

Snow is an important climate regulator because it greatly increases the surface albedo of middle and high latitudes of the Earth. Earth system models (ESMs) often adopt two-stream approximations with different radiative transfer techniques, the same snow therefore has different solar radiative properties depending whether it is on land or on sea ice. Here we intercompare three two-stream algorithms widely used in snow models, improve their predictions at large zenith angles, and introduce a hybrid model suitable for all cryospheric surfaces in ESMs. The algorithms are those employed by the SNow ICe and Aerosol Radiative (SNICAR) module used in land models, dEdd–AD used in Icepack, the column physics used in the Los Alamos sea ice model CICE and MPAS-Seaice, and a two-stream discrete-ordinate (2SD) model. Compared with a 16-stream benchmark model, the errors in snow visible albedo for a direct-incident beam from all three two-stream models are small (75∘. These results are incorporated in a hybrid model SNICAR-AD, which can now serve as a unified solar radiative transfer model for snow in ESM land, land ice, and sea ice components.

URLhttp://dx.doi.org/10.5194/tc-13-2325-2019
DOI10.5194/tc-13-2325-2019
Journal: The Cryosphere
Year of Publication: 2019
Volume: 13
Number: 9
Pages: 2325-2343
Date Published: 09/2019

Snow is an important climate regulator because it greatly increases the surface albedo of middle and high latitudes of the Earth. Earth system models (ESMs) often adopt two-stream approximations with different radiative transfer techniques, the same snow therefore has different solar radiative properties depending whether it is on land or on sea ice. Here we intercompare three two-stream algorithms widely used in snow models, improve their predictions at large zenith angles, and introduce a hybrid model suitable for all cryospheric surfaces in ESMs. The algorithms are those employed by the SNow ICe and Aerosol Radiative (SNICAR) module used in land models, dEdd–AD used in Icepack, the column physics used in the Los Alamos sea ice model CICE and MPAS-Seaice, and a two-stream discrete-ordinate (2SD) model. Compared with a 16-stream benchmark model, the errors in snow visible albedo for a direct-incident beam from all three two-stream models are small (75∘. These results are incorporated in a hybrid model SNICAR-AD, which can now serve as a unified solar radiative transfer model for snow in ESM land, land ice, and sea ice components.

DOI: 10.5194/tc-13-2325-2019
Citation:
Dang, C, CS Zender, and MG Dang.  2019.  "Intercomparison and Improvement of Two-Stream Shortwave Radiative Transfer Schemes in Earth System Models for a Uunified Treatment of Cryospheric Surfaces."  The Cryosphere 13(9): 2325-2343.  https://doi.org/10.5194/tc-13-2325-2019.