The Design Document page provides a description of the algorithms, implementation and planned testing including unit, verification, validation and performance testing. Please read Step 1.3 Performance Expectations that explains feature documentation requirements from the performance group point of view.
Design Document
In the table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation, 
- competed, 
- in progress, 
- not done
Overview table for the owner and an approver of this feature
1.Description | SNICAR-AD Shortwave Radiation for Sea Ice |
2.Owner | Cheng Dang (Unlicensed) |
| 3.Created | |
| 4.Equ | |
| 5.Ver | |
| 6.Perf | |
| 7.Val | |
| 8.Approver | |
| 9.Approved Date | |
| V2.0 | Pending |
Title: SNICAR-AD Shortwave Radiation for Sea Ice
Requirements and Design
E3SM Cryosphere Group
Date:
Summary
Requirements
Modify the sea-ice shortwave code to include a new subroutine SNICAR_AD that
- provides new input files for snow and ice optics adopted by ELM;
- expands the shortwave radiative calculation to 5 subdivided solar bands adopted by ELM;
- removes empirical adjustment for radiative-effective snow grain size;
- adopts a new algorithm to correct for the bias of near-infrared albedo and absorption when solar zenith angles are larger than 75 degrees.
Date last modified: Jun 1st, 2019
Contributors: Cheng Dang (Unlicensed)
Algorithmic Formulations
Design solution: described in the following article
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.
Date last modified: July 1st, 2019
Contributors: Cheng Dang (Unlicensed)
Design and Implementation
Implementation:
In ice_shortwace.F90, we add a new subroutine SNICAR_AD to compute the shortwave radiative properties of snow-covered sea ice, which can be turned on by setting config_use_snicar_ad = true in the namelist.
Source code: https://github.com/chengdang/MPAS-Model/tree/seaice/snowice_sw_snicar. The code modification is merged to the sea-ice developing branch, with default config_use_snicar_ad = false.
The pseudocode in ice_shortwave.F90
if snow-covered sea ice:
if (config_use_snicar_ad):
call snicar_ad
else
call default shortwave algorithm
end
end
subroutine snicar_ad
Verification and Unit Testing:
- The offline radiative transfer model has been tested against a multi-stream benchmark model. (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.)
- Results of the modified E3SM model are tested against E3SM_v1 released pre-industrial simulations:
- 30-year MPAS-analysis: https://portal.nersc.gov/project/m2833/cdang/30yr.mpas_analysis.m2m.SNICAR_AD_landseaice_vs_DECKv1b.piControl.ne30_oEC.edison/
- 30-year E3SM diagnostics: https://portal.nersc.gov/project/m2833/cdang/30yr.e3sm_diags.m2m.SNICAR_AD_landseaice.SNICAR_AD_seaice.ne30_oEC.edison/viewer/
- Results of the modified E3SM model will be tested against E3SM_v1 released historical simulations (Fully-coupled historical simulations are in progress).
Date last modified: July 1st, 2019
Contributors: Cheng Dang (Unlicensed)
Planned Validation Testing
Validation Testing:
- Results of the modified E3SM model are tested against observation provided by mpas-analysis and e3sm diagnostics.
- 30-year MPAS-analysis: https://portal.nersc.gov/project/m2833/cdang/30yr.mpas_analysis.m2o.SNICAR_AD_land_seaice.piControl.ne30_oEC.edison/
- 30-year E3SM diagnostics: to be added.
- Results of the modified E3SM model will be tested against observations/reanalysis/model simulations of snow depth, sea-ice concentration/fraction, dust and black carbon concentration (Fully-coupled historical simulations are in progress).
- BC/Dust in snow:
- The Arctic: Doherty et al., 2010
- China: Wang et al., 2013
- North America: Doherty et al., 2014
- Data summary: Dang et al., 2017
- Sea-ice concentration/extent: PIOMAS
- Snow depth: to be added.
- BC/Dust in snow:
Date last modified: July 1st, 2019
Contributors: Cheng Dang (Unlicensed)
Planned Performance Testing
Performance Testing:
The new implementation is not expected to have a significant impact on the computational cost/performance of E3SM.