Patterns of variability in the satellite microwave sounding unit temperature record: comparison with surface and reanalysis data

Principal component analysis is applied to global temperature records to study the differences in the patterns of variability between surface and troposphere. Surface, Microwave Sounding Unit (lower troposphere, channel 2 and channel 4) and National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis thickness data are studied in the common period 1979–2000. The patterns of variability are classified into geographical regions and compared. The series of their time coefficients are correlated to assess the existence of common and significant climate-change signals in the form of climatic trends. The objective is to identify the physical processes determining the records' variations and the differences between the surface and the satellite records that might be related to the discrepancy in their globally averaged trend. Major differences were found in the Tropics, where the surface warming is not paralleled in any other record. The surface record has two major patterns over the Tropics, one of which is connected to El Nino–southern oscillation. Satellite variability is instead described by only one pattern, most probably deriving from the merging of the two distinct patterns found for the near-surface records. In the eastern Antarctic a higher troposphere and lower stratosphere negative trend is found connected to ozone depletion. This signal prevails in the satellite record, despite evidence that it is confined only above 500 hPa. A pattern over Siberia is linked to the ‘Euro-Siberian oscillation’, i.e. the change in the pressure field determining the tracks of the Atlantic storms over the area Copyright © 2003 Royal Meteorological Society