30 April 2016 Assimilation of SAPHIR radiance: impact on hyperspectral radiances in 4D-VAR
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Abstract
Assimilation of a new observation dataset in an NWP system may affect the quality of an existing observation data set against the model background (short forecast), which in-turn influence the use of an existing observation in the NWP system. Effect of the use of one data set on the use of another data set can be quantified as positive, negative or neutral. Impact of the addition of new dataset is defined as positive if the number of assimilated observations of an existing type of observation increases, and bias and standard deviation decreases compared to the control (without the new dataset) experiment. Recently a new dataset, Megha Tropiques SAPHIR radiances, which provides atmospheric humidity information, is added in the Unified Model 4D-VAR assimilation system. In this paper we discuss the impact of SAPHIR on the assimilation of hyper-spectral radiances like AIRS, IASI and CrIS. Though SAPHIR is a Microwave instrument, its impact can be clearly seen in the use of hyper-spectral radiances in the 4D-VAR data assimilation systems in addition to other Microwave and InfraRed observation. SAPHIR assimilation decreased the standard deviation of the spectral channels of wave number from 650 -1600 cm-1 in all the three hyperspectral radiances. Similar impact on the hyperspectral radiances can be seen due to the assimilation of other Microwave radiances like from AMSR2 and SSMIS Imager.
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Indira Rani S., Indira Rani S., Amy Doherty, Amy Doherty, Nigel Atkinson, Nigel Atkinson, William Bell, William Bell, Stuart Newman, Stuart Newman, Richard Renshaw, Richard Renshaw, John P. George, John P. George, E. N. Rajagopal, E. N. Rajagopal, } "Assimilation of SAPHIR radiance: impact on hyperspectral radiances in 4D-VAR", Proc. SPIE 9880, Multispectral, Hyperspectral, and Ultraspectral Remote Sensing Technology, Techniques and Applications VI, 98800M (30 April 2016); doi: 10.1117/12.2222781; https://doi.org/10.1117/12.2222781
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