92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012: 4:30 PM
Comparison of Annual Cycles of Earth Radiation
Room 355 (New Orleans Convention Center )
G. Louis Smith, Science Systems and Applications, Inc., Hampton, VA; and P. E. Mlynczak and G. L. Potter

The annual cycles of absorbed solar radiation (ASR), outgoing longwave radiation (OLR) and net radiation have been computed from an eight-year data set from the Clouds and Earth's Radiant Energy System (CERES) scanning radiometers aboard the Terra spacecraft. In support of the Terra and Aqua spacecraft science applications, Goddard Space Flight Center generates the Goddard Earth Observing System Atmospheric General Circulation Model (GEOS-5) data set, which includes the radiation budget components based on measured atmospheric parameters. These radiation fields are time and space dependent. The annual cycles of these model results were computed. In order to compare the annual cycles from these two data sets, the principal components (PCs) of each data set were computed to express the time variations, and the corresponding empirical orthogonal functions (EOFs) were computed to describe the geographic variations. Ocean has a long thermal response time compared to land, so ocean and land were separated for the analysis. The root-mean-square values for the annual cycles of the ASR, OLR and net radiation are extremely close for the two data sets. The first three PCs are likewise quite close, showing that the time responses and magnitudes over the globe are very similar. The agreement between the two sets of PCs is quantified by computing the matrix of inner products of the two data sets. The EOF maps are similar for most of the globe, but differ in a few places. The agreements of the EOF maps are likewise quantified. Additional analysis is required to determine the reasons for these anomalies. The method used presented here can be used to quantify the agreement/differences between data sets in terms of a number of features, permitting comparison at levels from a global annual mean to a details of time and space variations of two data sets. These measures enable objective comparison of several data sets.

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