B12 Activate Aerosol Shortwave Feedback in Sea Ice: Design Document

Owned by
Nicole Jeffery
Last updated: Oct 13, 2020
3 min read

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

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The first table in Design Document gives overview of this document, from this info the Design Documents Overview page is automatically created.

In the overview table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation

  • Equations: Document the equations that are being solved and describe algorithms
  • Verification Plans: Define tests that will be run to show that implementation is correct and robust. Involve unit tests to cover range of inputs as well as benchmarks.
  • Performance expectations: Explain the expected performance impact from this development
  • Validation Plans: Document what process-based, stand-alone component, and coupled model runs will be performed, and with what metrics will be used to assess validity

Use the symbols below (copy and paste) to indicate if the section is in progress or done or not started.

In the table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation,   (tick) - competed, (warning) - in progress, (error) - not done


Overview table for the owner and an approver of this feature

1.Description

Activate the black carbon and dust aerosols in sea ice and turn on shortwave feedbacks
2.OwnerNicole Jeffery
3.CreatedOct 13, 2020
4.Equ(error)
5.Ver(error)
6.Perf(error)
7.Val(error)
8.Approver
9.Approved Date
V2.0
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Table of Contents




Title: ...

Requirements and Design

E3SM CBGC Group

Date: 10/12/2020 

Summary

In v1 of E3SM, Hailong Wang led a  development feature (A13) which made compatible the treatment of light-absorbing particles deposited in snow and sea ice with the atmospheric MAM aerosol scheme.   This feature was accepted into v1.0 on October 2015 and used successfully in the land snow model.  However, the feature was never validated in MPAS-SI and so not activated in the v1 simulations.  We propose to validate the scheme in MPAS-SI by testing the code in fully coupled mode, comparing mass ratios of black carbon and dust in sea ice with observations, and contrasting the impact of aerosol inclusions on sea ice and snow volume with CESM.


Requirements

Requirement: Analysis of fully coupled simulations with appropriate flags activated and de-activated

  1. The current v2 code has a dust and black carbon capability already implemented in MPAS-SI.  To validate this capability, we require a fully coupled run of at least 30 years with black carbon, dust and radiative feedbacks activated in MPAS-SI namelist.MAM atmospheric aerosols are default in the current codebase.
  2. We also require a control run. This will be obtained from the v2 WC spin-up.
  3. Validate black carbon mass ratios with Doherty et al (JGR, 2015) in Arctic sea ice.
  4. Compare changes in sea ice volume, snow thickness, and ice extent with Holland et al 2012 (Journal of Climate)
  5. Some parameter tuning will likely be needed.

Date last modified: 10/13/2020
Contributors: Nicole Jeffery

Algorithmic Formulations

None.  Code implementation was completed  in v1, A13 Interactions With Surface Models - Aerosol Interactions with Ice Design Document

Date last modified:

Contributors: Nicole Jeffery


Design and Implementation

None.  See  A13 Interactions With Surface Models - Aerosol Interactions with Ice Design Document

Date last modified:
Contributors: Nicole Jeffery

Planned Verification and Unit Testing 

Verification and Unit Testing: restartability and parallelism

MPAS-SI already has regression, restartability and parallelism tests for aerosols in the testsuites (testsuite.aerosol_shortwave.xml) .  These are tested currently in MPAS-SI with each new PR.  Ocean-sea ice simulations with constant atmospheric aerosol fluxes were completed and tested for restartability, parallelism, and stability  during v1 development. 

Date last modified:    


Contributors: Nicole Jeffery


Planned Validation Testing 

Validation Testing: Comparison of fully coupled run with models and literature

Date last modified:10/13/2020

Contributors: Nicole Jeffery


In order to validate dynamic and seasonally varying aerosol fluxes on sea ice, we will use a 30 year fully coupled control 30 from the v2 WC spin-up and a 30 year fully coupled simulation with two black carbon tracer groups, four dust groups in the modal aerosol configuration with radiative feed-backs in MPAS-SI.   We expect only minor impact in the Southern Ocean and so focus validation on Arctic sea ice. Results will be compared with the following sources.

For black carbon mass ratios in Arctic sea ice:

Doherty, S. J., Steele, M., Rigor, I., and Warren, S. G. (2015), Interannual variations of light‐absorbing particles in snow on Arctic sea ice, J. Geophys. Res. Atmos., 120, 11,391– 11,400, doi:10.1002/2015JD024018.

For climate impacts of aerosols in Arctic sea ice:

Holland, M. M., D. A. Bailey, B. P. Briegleb, B. Light, and E. Hunke, 2012: Improved Sea Ice Shortwave Radiation Physics in CCSM4: The Impact of Melt Ponds and Aerosols on Arctic Sea Ice. J. Climate, 25, 1413–1430, https://doi.org/10.1175/JCLI-D-11-00078.1.

Planned Performance Testing 

Performance Testing: short-desciption-of-testing-here

Date last modified:10/13/2020
Contributors: Nicole Jeffery


We'll use the same fully coupled run to contrast computational expense. It is expected that additional aerosols in sea ice snow and ice layers will increase computational cost.  If prohibitive, we would consider reducing the cost by testing the impact of reduced set of dust/BC tracers.