Satellite-derived vertical dependence of tropical tropospheric temperature trends

Tropical atmospheric temperatures in different tropospheric layers are retrieved using satellite-borne Microwave Sounding Unit (MSU) observations. We find that tropospheric temperature trends in the tropics are greater than the surface warming and increase with height. Our analysis indicates that the near-zero trend from Spencer and Christy's MSU channel-2 angular scanning retrieval for the tropical low-middle troposphere (T-2LT) is inconsistent with tropical tropospheric warming derived from their MSU T-2 and T-4 data. We show that the T-2LT trend bias can be largely attributed to the periods when the satellites had large local equator crossing time drifts that cause large changes in calibration target temperatures and large diurnal drifts.