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Summary
The new feature is tested with fully coupled E3SM simulation for both PI-control and historical layoutdeveloped based on a series of offline tests regarding snow/seaice radiative transfer models. For more details, please see the paper:
Dang, C., Zender, C. S., and Flanner, M. G.: Inter-comparison and improvement of 2-stream shortwave radiative transfer models for a unified treatment of cryospheric surfaces in ESMs, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-22, in review, 2019.
Verification Test 1
Verification Test 1: I
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nter-comparison of two-stream shortwave radiative transfer models in E3SM
Date last modified: Jun 17, 2019
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Provenance: (Run provenance Link, Code Tag, etc.)
Results:
The shortwave radiative transfer algorithm 1. Comparisons of three two-stream models (SNICAR used in ELM, dEdd-AD implemented used in MPAS-seaice, a new algorithm 2SD) against a 16-stream DISORT benchmark model show dEdd-AD produces more accurate snow radiative properties, especially under a cloudy sky.
Figure 6 . Error of Dang et al., 2019. The difference in diffuse snow albedo (δα = α2 – α16) computed using two-stream models , for (α2) and using 16-stream DISORT model (α16), for various snow depths and snow grain radii, with solar zenith angle of 60° at the top of the atmosphere (results from the proposed new model are showing in the middle row).
Reference: Dang, C., Zender, C. S., and Flanner, M. G.: Inter-comparison and improvement of 2-stream shortwave radiative transfer models for unified treatment of cryospheric surfaces in ESMs, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-22, in review, 2019.
2. Comparisons of different band options show that the 5-band scheme used by SNICAR effectively captures the spectral variation of snow albedo and therefore produces more accurate solar flux estimation for snow-covered sea ice. The left figure shows spectral snow albedo and band-averaged albedo for different options. The right figure shows the error of reflected shortwave flux computed using different band approximations, evaluated against the spectrally integrated reflected solar flux from 0.3 to 5 microns for every 10 nm. Proposed new model results for snow-covered sea ice are those shown for SNICAR.
Verification Test 2
Verification Test 2: Correction for direct albedo for large solar zenith angles
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Provenance: (Run provenance Link, Code Tag, etc.)
Results:
Figure 12 . Error of Dang et al., 2019: Error in semi-infinite snow albedo computed using dEdd-AD before (top row) and after (bottom row) incorporating corrections for near-IR albedo, for different solar zenith angles and snow grain radii.
Reference: Dang, C., Zender, C. S., and Flanner, M. G.: Inter-comparison and improvement of 2-stream shortwave radiative transfer models for unified treatment of cryospheric surfaces in ESMs, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-22, in review, 2019.