Methodology for deriving deep-layer mean temperatures from combined satellite infrared and microwave observations

Deep-layer mean temperatures from Microwave Sounding Unit (MSU) observation s have been used by scientists to study trends and interannual variations o f tropospheric and lower-stratospheric temperature. The spatial resolution of MSU deep-layer mean temperatures is rather poor For studying trends in l ocalized regions. A method is developed in which infrared observations from the High-resolution InfraRed Sounder (HIRS) is used in combination with MS U to derive deep-layer mean temperatures with improved vertical and horizon tal resolution. Even though the relationship between infrared radiance and temperature is not linear, the layer associated with the mean temperature i s shown to be well defined with a small airmass dependency that is similar to MSU's airmass dependency. Preliminary validation of HIRS-MSU-derived lay er mean temperatures with radiosonde layer mean temperatures show similar p recision when compared to MSU-only derived temperatures.