Solar Radiation Treatments in Snow and Sea-Ice

Charlie Zender, Cheng Dang Department of Earth System Science UC Irvine

Acknowledging:Andrew Roberts, Mark Flanner, Nicole Jeffery,

Elizabeth Hunke, Robert Pincus

On Web

ACME All-Hands MeetingPotomac, MD

June 5-7, 2017

1998 SHEBA Observation CICE model

Perovich et al., 2002Briegleb and Light, 2007

Opportunities for Improvement1. Harmonize land/ice with sea-ice snow RT2. Re-organize spectral bands3. Optical properties update4. Physical processes

Opportunities for Improvement1. Harmonize land/ice with sea-ice snow RT2. Re-organize spectral bands3. Optical properties update4. Physical processes

Harmonize land/ice with sea-ice RT1. CICE: delta-Eddington

○ 3 bands (1 visible, 2 NIR)○ Adding/Doubling, Gaussian integration○ Melt ponds, bare ice

2. ALM: SNow-ICe-Aerosol Radiative model (SNICAR)○ 5 bands (1 visible, 4 NIR)○ Delta-Hemispheric Mean, Tri-diagonal inversion○ Needs melt ponds, bare ice

Snow: Delta-Eddington vs. SNICAR

CICE agrees with SNICAR on broadband albedo CICE absorbs ~30% more internally (spectral resolution?)

Briegleb and Light, 2007

Opportunities for Improvement1. Harmonize land/ice with sea-ice snow RT2. Re-organize spectral bands3. Optical properties update4. Physical processes

Re-organize Spectral Bands1. RRTMG computes 14 solar bands

○ Coupler: Aggregates to 2 spectral bands■ Sends 4 fluxes, receives 4 albedos■ Vis+NIR direct+diffuse■ 4 2-D fields per spectral band

2. Surface models re-bin RRTMG to 2, 3, or 5 bands○ Assumes fixed sub-bin distribution in NIR○ RRTMG band straddles 0.7 um

3. Couple all 14 RRTMG bands?4. Re-bin so RRTMGP boundary at 0.7 um?

Spectral Bins

Roberts and Light (2016) A plan for CICE Delta-Eddington Version2

Opportunities for Improvement1. Harmonize land/ice with sea-ice snow RT2. Re-organize spectral bands3. Optical properties update4. Physical processes

Optical Properties Update

1. Newer Melt Pond Observations (Light et al.)2. Aerosol, chlorophyll (Wang, Ogunro, Jeffery,

Burrows, Deng, Dubey)

Ice Optical Constants (Warren and Brandt, 2008)

Optical Property of Snow

Single-scattering properties of snow (Dang, Brandt, and Warren 2015)

Mie Theory

Snow radiative transfer simulationSea ice: CICE Delta Eddington methodLand and ice sheet: SNICAR

Optical Properties of Bare Ice and Ponded Ice

SHEBA 1998multi-year sea ice

ICESCAPE 2010, 2011first-year sea ice

• Sea ice interior optical properties measured at finer spectral resolution• Optical properties of first-year sea ice more suitable for the simulation of

current summer Arctic sea ice

Light et al., 2015Briegleb and Light, 2007

Opportunities for Improvement1. Harmonize land/ice with sea-ice snow RT

○ CICE delta-Eddington○ SNow-ICe-Aerosol Radiative model (SNICAR)

2. Re-organize spectral bands○ CAM-SE: RRTMG with 14 solar bands○ ALM+CICE: Two bands (visible+NIR)

3. Optical properties update○ Melt ponds○ Impurities (including algae)

4. Physical processes○ Roughness, compaction, inclination, 3D, ....○ Angular distribution

Supplementary Slides

Sea Ice Algae

Lund-Hansen et al.,2015

Light absorption by BC and Chlorophyll in the Arctic Sea Ice

(Ogunro et al., 2017)Ehn and Mundy, 2013

Melt Pond

Arctic Melt Pond Fraction Trend in June2002 - 2011

(Istomina et al., 2015)

Schröder et al.,2014