Assessment of intercalibration methods for satellite microwave humidity sounders
Article first published online: 20 MAY 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 10, pages 4906–4918, 27 May 2013
How to Cite
2013), Assessment of intercalibration methods for satellite microwave humidity sounders, J. Geophys. Res. Atmos., 118, 4906–4918, doi:10.1002/jgrd.50358., , , , and (
- Issue published online: 3 JUL 2013
- Article first published online: 20 MAY 2013
- Accepted manuscript online: 25 MAR 2013 04:28PM EST
- Manuscript Accepted: 20 MAR 2013
- Manuscript Revised: 18 MAR 2013
- Manuscript Received: 21 AUG 2012
 Three methods for intercalibrating humidity sounding channels are compared to assess their merits and demerits. The methods use the following: (1) natural targets (Antarctica and tropical oceans), (2) zonal average brightness temperatures, and (3) simultaneous nadir overpasses (SNOs). Advanced Microwave Sounding Unit-B instruments onboard the polar-orbiting NOAA 15 and NOAA 16 satellites are used as examples. Antarctica is shown to be useful for identifying some of the instrument problems but less promising for intercalibrating humidity sounders due to the large diurnal variations there. Owing to smaller diurnal cycles over tropical oceans, these are found to be a good target for estimating intersatellite biases. Estimated biases are more resistant to diurnal differences when data from ascending and descending passes are combined. Biases estimated from zonal-averaged brightness temperatures show large seasonal and latitude dependence which could have resulted from diurnal cycle aliasing and scene-radiance dependence of the biases. This method may not be the best for channels with significant surface contributions. We have also tested the impact of clouds on the estimated biases and found that it is not significant, at least for tropical ocean estimates. Biases estimated from SNOs are the least influenced by diurnal cycle aliasing and cloud impacts. However, SNOs cover only relatively small part of the dynamic range of observed brightness temperatures.