April 22, 2023 1

April 22, 2023 2

Status of the Current SSMI/S Algorithm

A-priori fixed reference emissivity spectra

100% First-Year (FY) Ice – from observations 100 % Multi-Year (MY) Ice - from observations 100 Ocean Water (W) - from FASTEM-3 EM model for calm seas

and Tskin = 272 K

A-priori emissivity spectra for a range of fractions

Generated using the following expression at each imaging frequency/polarization

ελp = εwλp Cw + εfyλp Cfy + εmyλp Cmy and Ct = Cw + Cmy + Cfy

where εwλp εfyλp εmyλp are 100% W, FY and MY emissivities

Posteriori retrievals of sea ice concentration

Minimization of Euclidian distance between a-priori (stored in library) and posteriori (retrieved from MIRS) emissivities

April 22, 2023 3

Status of the Current SSMI/S Algorithm (con’t)

MIRS EDRs used

Retrieved emissivities at 19, 22, 37 and 92 GHz (V+H) compared with those in the library to find closest match

Retrieved Tskin used as constraint

Results Statistical inter-comparisons against AMSR-E are under way (Chris

Grassotti) – underestimation along edges & closed ice

Underestimation of high sea ice concentration compared to AMSU-MHS – persisted for the entire summer period of 2008 (June – October 2008)

Geophysical noise along coastal pixels due to land influences

April 22, 2023 4

More pronounced underestimations observed during mid-Summer (Arctic)

SSMI/S AMSU-MHS

April 22, 2023 5

Negative bias persists in early Fall 2008 over new ice (not as large, but extensive)

SSM/IS

April 22, 2023 6

New SSMI/S Retrieval Strategy

Use hybrid technique

Over multi-year ice (predominant in summer), do not use 89 GHz due to increased variability & surface effects

Over multi-year ice, use emissivity and polarization gradients up to 37 GHz as more “stable” radiometric parameters

Over first-year ice, use absolute emissivities in the 19-92 GHz window range as more stable radiometric parameters

Preliminary Results (not final) Much improved retrievals in Fall 2008 over both closed ice & ice edges More consistent to AMSU-MHS, superior over peripheral & first-year ice Geophysical noise along coastlines remains

April 22, 2023 7

Inter-comparisons between the current SSMI/S, N18 & Metop-A AMSU-MHS and new SSMI/S – very encouraging results

Current SSMI/S New SSMI/S

Current Metop-A

Current Metop-A Current AMSU-MHS

April 22, 2023 8

New SSMI/S Inter-comparison Examples for October 26, 2008 with the Operational North European Analysis Sea Ice Product

New SSMI/S (microwave only)Analysis (SSMI + NWP + manual intervention)

April 22, 2023 9

Much improved, consistent retrievals over Antartica as well. Appears less noisy than AMSU-MHS

Current SSMI/S New SSMI/S

Current NOAA 18Current Metop-A

April 22, 2023 10

Pending SSMI/S Work and expected remedies

Sea Ice Improve geophysical noise over coastlines Use geographical and geophysical constrains to reduce it as much as possible Make refinements to the algorithm for optimal accuracy based on feed-back from on-going evaluation work

SWE Improve current algorithm Use strategies applied to AMSU-MHS Flag tough SWE areas such as Greenland and Antarctica using geographical constrains