COMPARISONS BETWEEN THE MICROWAVE SOUNDING UNIT TEMPERATURE RECORD AND THE SURFACE-TEMPERATURE RECORD FROM 1979 TO 1996 - REAL DIFFERENCES OR POTENTIAL DISCONTINUITIES

This paper reports a detailed comparison at the global, hemispheric, t hree 60 degrees-latitude zone, and grid-box scale between lower tropos pheric temperatures from the microwave sounding units (MSU2R) on board NOAA polar orbiting satellites and surface temperatures. The comparis ons reveal differences in the course of temperature trends over the 19 79-1996 period in the two sets of time series. The surface data warms relative to MSU2R by 0.19 degrees C per decade over this period, with much of the change occurring as a jump in the difference series, parti cularly during 1991 but also in 1981. The differences either reflect p roblems in one or both of the surface or MSU2R records or, if both rec ords are correct, a significant change in lapse rates in the lower par t of the atmosphere on a global scale particularly since mid-1991. Alt hough MSU2R data agree well with radiosonde data on global and hemisph eric scales over 1979-1996, surface and radiosonde data agree almost e xactly when their trends are compared over 1958-1993 and 1965-1996. Th e differences in the two data sets are discussed in terms of possible natural causes and data homogeneities.