Geophysical trends from 12+ years of AIRS radiance trends

Wednesday, 17 December 2014
Sergio G Desouza-Machado, Lawrence Larrabee Strow, Andrew Tangborn, Christopher Hepplewhite and Howard Motteler, University of Maryland Baltimore County, Baltimore, MD, United States
AIRS has been providing low noise, stable top-of-the atmosphere
hyperspectral radiances since 2002. In this presentation we use two
radiance subsets; (1) clear-sky scenes over ocean and (2) all-sky
scenes along the nadir track. The linear trends of the AIRS spectral
radiances are used to retrieve a variety of geophysical trends using
an optimal estimation approach. These retrieved clear sky trends
compare favorably with ERA and MERRA re-analysis trends, and in-situ
trends for the minor gases. Preliminary analysis of all-sky trends
(using radiance time derivatives) agree better with ERA than either
MERRA or the AIRS Level-2 retrievals. Trends in cloud radiative
forcing are also examined using probability distribution functions
(pdfs) of the AIRS radiances for regional subsets. These are compared
to ERA simulated radiances. These radiance and radiance PDF trends
provide highly accurate measurements of atmospheric variability with
easily understood error characteristics, unlike Level 2 retrievals.
These analysis approaches should provide highly accurate measurements
of a variety of climate trends (temperature and humidity profiles,
land surface temperature, cloud radiative forcing) as the AIRS (or
AIRS + JPSS/CrIS) instrument time-series soon extends to 15+ years.