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Global energy balance of the Earth-atmosphere system may change due to natural and man-made climate
variations. For example, changes in the outgoing longwave radiation (OLR) can be regarded as a crucial
indicator of climate variations. Clouds play an important role -still insufficiently assessed- in the global energy
balance on all spatial and temporal scales, and satellites provide an ideal platform to measure cloud and largescale
atmospheric variables simultaneously. The TOVS series of satellites were the first to provide this type of
information since 1979. OLR [Mehta and Susskind1], cloud cover and cloud top pressure [Susskind et al.2] are
among the key climatic parameters computed by the TOVS Pathfinder Path-A algorithm using mainly the
retrieved temperature and moisture profiles. AIRS, regarded as the 'new and improved TOVS', has a much
higher spectral resolution and greater S/N ratio, retrieving climatic parameters with higher accuracy.
First we present encouraging agreements between MODIS and AIRS cloud top pressure (Ctp) and
'effective' (Aeff, a product of infrared emissivity at 11 μm and physical cloud cover or Ac) cloud fraction
seasonal and interannual variabilities for selected months. Next we present validation efforts and preliminary
trend analyses of TOVS-retrieved Ctp and Aeff. For example, decadal global trends of the TOVS Path-A and
ISCCP-D2 Pc and Aeff/Ac values are similar. Furthermore, the TOVS Path-A and ISCCP-AVHRR [available
since 1983] cloud fractions correlate even more strongly, including regional trends.
We also present TOVS and AIRS OLR validation effort results and (for the longer-term TOVS Pathfinder
Path-A dataset) trend analyses. OLR interannual spatial variabilities from the available state-of-the-art CERES
measurements and both from the AIRS [Susskind et al.3,4] and TOVS OLR computations are in remarkably
good agreement. Global monthly mean CERES and TOVS OLR time series show very good agreement in
absolute values also. Finally, we will assess correlations among long-term trends of selected parameters,
derived simultaneously from the TOVS Pathfinder Path-A dataset.
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