Understanding inter-satellite biases of microwave humidity sounders using global simultaneous nadir overpasses

John, V. O., Holl, G., Buehler, S. A., Candy, B., Saunders, R. W. and Parker, D. E. (2012) Understanding inter-satellite biases of microwave humidity sounders using global simultaneous nadir overpasses. Journal of Geophysical Research, 117 (D2). D023051. ISSN 0148-0227 doi: 10.1029/2011JD016349

Abstract/Summary

Simultaneous nadir overpasses (SNOs) of polar-orbiting satellites are most frequent in polar areas but can occur at any latitude when the equatorial crossing times of the satellites become close owing to orbital drift. We use global SNOs of polar orbiting satellites to evaluate the intercalibration of microwave humidity sounders from the more frequent high-latitude SNOs. We have found based on sensitivity analyses that optimal distance and time thresholds for defining collocations are pixel centers less than 5 km apart and time differences less than 300 s. These stringent collocation criteria reduce the impact of highly variable surface or atmospheric conditions on the estimated biases. Uncertainties in the estimated biases are dominated by the combined radiometric noise of the instrument pair. The effects of frequency changes between different versions of the humidity sounders depend on the amount of water vapor in the atmosphere. There are significant scene radiance and thus latitude dependencies in the estimated biases and this has to taken into account while intercalibrating microwave humidity sounders. Therefore the results obtained using polar SNOs will not be representative for moist regions, necessitating the use of global collocations for reliable intercalibration.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/49058
Identification Number/DOI	10.1029/2011JD016349
Refereed	Yes
Divisions	No Reading authors. Back catalogue items Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	calibration, amsu, bias
Publisher	American Geophysical Union
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