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AIRS, IASI and CrIS Retrieval Records At Climate Scales - An Investigation into...

Smith, N. (2015), AIRS, IASI and CrIS Retrieval Records At Climate Scales - An Investigation into the Propagation of Systematic Uncertainty, J. Appl. Meteor. Climat., doi:10.1175/JAMC-D-14-0299.1.

Uncertainty requirements for climate observations are more stringent than for weather observations due to the scale dependency of natural variation. At present there is no space-based climate observing system, so weather observations have to be aggregated to study large-scale change. The management and minimization of uncertainty sources in weather observations are, therefore, a high priority. This work is a first attempt at investigating if a single long-term record can be assembled with temperature retrievals from three hyperspectral satellite sounders in polar orbit, the Atmospheric Infrared Sounder (AIRS on Aqua in PM orbit since 2002), Infrared Atmospheric Sounding Interferometer (IASI on Metop-A in AM orbit since 2006) and Cross-track Infrared Sounder (CrIS on Suomi-NPP in PM orbit since 2011). These instruments not only measure the vertical atmospheric structure but also atmospheric composition, thus providing coincident observations of many essential climate variables. Two main sources of known systematic differences, namely Local Sampling Time (LST) and instrument type (i.e., interferometer versus grating spectrometer), are characterized. For a five-year record it is shown that differences among these temperature soundings are height dependent – a multi-instrument data record could be assembled from measurements of the stratosphere but not yet for the troposphere where cloud effects are shown to be dominant and dependent on instrument type. Moreover, LST differences are limited to regional systematic effects in the lower-troposphere and boundary layer. This research is a step towards the development of transparent and geophysically consistent methods with which to assemble weather measurements into climate observations.

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Radiation Science Program (RSP)