Reference-Quality Emission and Backscatter Modeling for the Ocean

Abstract

(ISSI) met to discuss the challenge of developing a community reference-quality ocean emission and reflection model for use across a broad spectral range [microwave (MW) and infrared (IR), and possibly also visible] as well as supporting passive and active remote sensing. The need for this has been identified in various reports and international workshops. Notably, the European Commission Horizon2020 project, GAIA-CLIM 1 (see appendix for acronyms), identified that the lack of a reference-quality ocean emission and backscatter model was a major gap in our ability to provide absolute calibration of the satellite based observing system. The gap was also identified by the ECMWF-JCSDA-NWP SAF all-sky assimilation workshop in December 2015 and again in February 2020 and the twenty-first meeting of the International TOVS Working Group in December 2017. An international science team was proposed to ISSI, and accepted, to develop a new model capability with these goals and characteristics:

Assimilation of satellite data in numerical weather prediction. Part II: Recent years

“…It has been shown (Brooke et al, 2019) that model LST forecasts in semi-arid regions may be underestimated by more than 10 K during the day, making it difficult to assimilate surface-sensitive observations, even with a reasonable estimate of the emissivity. Progress and challenges in the modelling of surface emissivity over ocean are discussed by English et al (2020).…”

“…Progress and challenges in the modelling of surface emissivity over ocean are discussed by English et al . (2020).…”

“…Furthermore, the sea‐surface temperature is usually rather well known (errors typically well under 1 K). However the challenge to provide a single physically based model working from low MW frequencies (L‐band) through to sub‐mm (over 300 GHz) through to the IR, complete with uncertainty characterisation, remains a challenge (English et al ., 2020).…”

Polarimetric Portraits

“…Following thorough verification demonstrations, the jointly sponsored Coriolis mission (Coriolis, 2003) was launched in 2003, whose primary instrument, WindSat (Gaiser et al, 2004)-still operational as of this writing-includes the full Stokes vector among its primary data products. Oceanic geophysical data retrieval from space-based radiometric observations continues to mature (English et al, 2020). The European Space Agency's requirements document for the Copernicus Imaging Microwave Radiometer (CIMR) (ESA, 2019) includes the specific terminology "full Stokes," a noteworthy upgrade from the first version of that document in which full polarimetry was not a featured requirement.…”

Development of the SURface Fast Emissivity Model for Ocean (SURFEM‐Ocean) Based on the PARMIO Radiative Transfer Model

“…These discrepancies, and their related differences with satellite observations, are partly due to the dedicated applications of a given model (e.g., designed for a specific instrument or for a given geophysical variable). Within the International Space Science Institute (ISSI) framework, a team of experts discussed the latest development in sea surface modeling with recommendations on the next steps for the various aspects of the model (i.e., sea water dielectric constants, wave spectrum, foam coverage and emissivity) (S. English et al., 2020). The community has converged on a Passive and Active Reference Microwave to Infrared Ocean (PARMIO) model.…”