Total Ozone Analysis Using SBUV/2 and CrIS
An algorithm using Total Ozone Analysis of Cross-track Infrared Sounder (CrIS) and Solar Backscatter UltraViolet Version 2 (SBUV/2) has been developed to generate combined UV and IR ozone retrievals. This algorithm is a new version of the current Total Ozone Analysis using Solar Back scatter Ultra Violet (SBUV/2) and Television InfraRed Observation Satellite (TIROS) Operational Version Sounder (TOVS) (TOAST).
Total and profile ozone from the SBUV/2 instrument are retrieved from radiance measurements at 12 discrete wavelengths in the ultraviolet (252 to 340 nm) (Bhartia et al., J. of Geophys. Res., 1996). The SBUV/2 data has gaps between its 14 orbits and over the pole during polar night because it is a nadir-viewing instrument. Ozone maps are generated using Cressman interpolation scheme. This interpolation scheme works well but spatial smoothing can mask Small-scale features and miss extremes.
The CrIS instrument on S-NPP [Han,Y. 2013] is a major step forward in the U.S. operational IR sounding capability previously provided by the HIRS instruments of the TIROS-N TOVS series. CrIS obtains good daily spatial coverage by using a cross-track scan mirror to cover a 2200-km wide swath with 30 earth-scene fields-of-regard (FOR). Each FOR consists of 9 fields-of-views (FOVs), aggregated into a 3x3 array of 14 km diameter spots in the nadir. CrIS is a plane mirror Michelson interferometer Fourier transform spectrometer, providing a spectral resolution of 0.625 cm-1 at the long-wave IR (LWIR) band from 650 to 1095 cm-1 which includes the ozone absorption band around 1040 cm-1. One CrIS EDR granule contains four cross-track swaths of 120 observations; the same orbits per day number as OMPS NP provides full global coverage. Unlike the HIRS retrieval product used in the current TOAST, CrIS retrieves not only ozone total amount but also a 100-layer ozone profile. This significant instrument improvement provides us more accurate ozone information within UTLS than that former TOAST HIRS provides.
The most significant improvement of the algorithm is in the IR-derived product replacement of the column amount retrievals from the High resolution InfraRed Sounder (HIRS) with the CrIS profile retrievals. This allows the algorithm to provide ozone not only global 1°x1° total amount map but also the same spatial resolution profile maps at 12 Umkehr layers. The new products have significantly increased accuracy in their troposphere ozone estimation.
The Ozone team continually monitors the performance of the various SBUV/2 and CrIS instruments and will vary the combination used in the distributed Enhanced TOAST product to provide the best quality product.