Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements

Temperature change of the lower troposphere ( LT) in the tropics ( 20 degrees S-20 degrees N) during the period 1979-2004 is examined using 58 radiosonde ( sonde) stations and the microwave-based satellite data sets of the University of Alabama in Huntsville ( UAH v5.2) and Remote Sensing Systems ( RSS v2.1). At the 29 stations that make both day and night observations, the average nighttime trend (+0.12 K decade(-1)) is 0.05 K decade(-1) more positive than that for the daytime (+0.07 K decade(-1)) in the unadjusted observations, an unlikely physical possibility indicating adjustments are needed. At the 58 sites the UAH data indicate a trend of +0.08 K decade(-1), the RSS data, +0.15. When the largest discontinuities in the sondes are detected and removed through comparison with UAH data, the trend of day and night releases combined becomes +0.09, and using RSS data, +0.12. Relative to several data sets, the RSS data show a warming shift, broadly occurring in 1992, of between +0.07 K and +0.13 K. Because the shift occurs at the time NOAA-12 readings began to be merged into the satellite data stream and large NOAA-11 adjustments were applied, the discrepancy appears to be due to bias adjustment procedures. Several comparisons are consistent with a 26-year trend and error estimate for the UAH LT product for the full tropics of +0.05 +/- 0.07, which is very likely less than the tropical surface trend of +0.13 K decade(-1).