Stable long-term retrieval of tropospheric temperature time series from the microwave sounding unit

Climatological time-series of tropospheric temperatures from the Microwave Sounding Unit (MSU) are potentially of great value in validating observations of climate change due to their excellent spatial and temporal coverage. However, the long-term trend signal is small relative to natural seasonal and inter-annual variability and inter-satellite biases, and is comparable to diurnal temperature drift arising from variation of the satellite local crossing time. Additional effects due to time-varying non-linear instrument response also contribute to instrument error. We discuss a consistent methodology for compensating for these factors and present an error model quantifying their significance in determination of long-term trends.