Antonia Gambacorta EDR Validation Teleconference 2014-01-28, NOAA/NESDIS/STAR

1. An experiment using high resolution NPP CrIS measurements for trace gas retrievals: carbon monoxide impact study Antonia Gambacorta EDR Validation Teleconference 2014-01-28, NOAA/NESDIS/STAR

2. An experiment using higher resolution NPP CrIS measurements: impact on the retrieval of atmospheric trace gases in preparation for JPSS 1 (~2017) and 2 (~2022) THE Cross-Track Infrared Sounder (CrIS) on-board theSuomi National Polar-orbiting Partnership (SNPP) platform is a Fourier spectrometer covering the longwave (655-1095 cm-1), midwave (1210-1750 cm-1), and shortwave (2155-2550 cm-1) infrared spectral regions. Due to bandwidth restrictions, in current operations the interferogram raw data record (RDR) is truncated at a geometrical path L of 0.8 cm, 0.4 cm and 0.2 cm, and its Fourier transform is Nyquist sampled at 1/2L, that is 0.625 cm-1, 1.25 cm-1 and 2.5 cm-1 in the three bands, respectively. On March 12th, 2013 five orbits of the CrIS instrument (from 12 March 15:46 GMT until 13 March 00:31GMT) were configured to down-link full path interferograms truncated at a geometrical path L of 0.8 cm in all three bands and Fourier transformed into radiance spectra with Nyquist resolution 0.625 cm-1 across the full spectrum. Hamming apodization introduces a slight degradation in the spectral resolution, roughly equal to 0.6/L, causing an effective spectral resolution of 0.75 cm-1. Because carbon monoxide (CO) spectral sensitivity is found in the shortwave region, CO retrievals are expected to benefit the most from the high resolution mode, now increased by a factor of 4 with respect to the operational resolution. For the scope of this analysis then, we focus on the case study of CO retrievals. Published reference of this study: A. Gambacorta, C. Barnet, W. Wolf. T. King, L. Strow, X. Xiong, N. Nalli, M. Goldberg, “An experiment using NPP CrIShigh spectral resolution measurements for trace gas retrievals: carbon monoxideretrieval impact study”, IEEE Geoscience and Remote Sensing Letters, in press, 2014.

3. CO Sensitivity Analysis to 1% CO perturbation 2.5cm^-1 res 0.625 cm^-1 res 0.25cm ^-1 res • The large structure present in the high resolution spectrum carries the distinctive signature of the COabsorption lines (top). The high resolution CO channel selection (blue cross symbols, 32 in total) captures the cores and wings of the CO absorption lines, enabling full sounding of the CO absorption curve of growth. (RTA used for simulations: UMBC SARTA)

4. NUCAPS CO retrieval (~450mb)high resolution mode (top) vs operational low resolution mode (bottom) High Res CO retrievals Low Res CO retrievals High resolution mode retrievals show significantly more structure in the global distribution of CO abundance with respect to the low resolution mode. The extended regions of heightened CO peak values on the high resolution map (top) are indicative of anthropogenic emissions, biomass burning and atmospheric transport patterns. These key features of the source and sink climatology of carbon monoxide are predominantly missed in the low resolution retrieval map (bottom).

5. NUCAPS High RES (top), AIRS (second), IASI (third) and MOPITT (bottom) CO retrievals NUCAPS High RES AIRS IASI MOPITT NUCAPS high resolution CO retrievals show a significantly improved agreement to all three CO satellite products. The observed differences among the four instruments are consistent with what has been previously observed and have been mainly attributed to differences in instrumental spectral resolution, retrieval methods, a priori and thermal contrast diurnal cycle. This analysis intended to provide a performance demonstration of the NUCAPS high resolution CO product, in terms of both spatial variability and order of magnitude, in support for the need of high resolution radiance measurements.

6. NUCAPS High Res (top left), NUCAPS Low Res (top right)AIRS (bottom left) and IASI (bottom right) CO DOF comparison NUCAPS High Res DOF NUCAPS Low Res DOF IASI DOF AIRS DOF NUCAPS high resolution CO DOFS (top left) are observed to consistently improve across all latitudinal regimes, up to one order of magnitude, with respect to the low resolution mode (top right). The higher information content enables for a larger departure from the first guess, hence the increased spatial variability observed in the high resolution retrieval map. NUCAPS high resolution CO DOFS performance appears by far more comparable to both the AIRS and IASI CO DOFS performance.

7. Conclusions Only when operated in high resolution mode, NUCAPS CO retrievals prove comparable to the existing operational CO retrievals from the MOPITT, AIRS and IASI instruments, in terms of spatial variability, order of magnitude and DOFS. The results shown provide evidence in support for the need of high resolution CrIS measurements. This is a fundamental prerequisite in guaranteeing continuity to the afternoon orbit monitoring of atmospheric CO as part of a multi-satellite, uniformly integrated, long term data record of atmospheric trace gases. The modular architecture of the NOAA/NESDIS/STAR hyper spectral retrieval system has proven that there is no risk of disruption to the operational processing upon switching to high resolution mode.