Global atmospheric temperature and humidity profiles based on intersatellite calibrated HIRS measurement

An atmospheric temperature and humidity profile dataset is generated from intersatellite calibrated HIRS measurement onboard the NOAA polar satellites since 1979. To minimize the intersatellite biases, an intersatellite calibration is performed for three decades of HIRS measurement based on simultaneous nadir overpass observations. An algorithm is developed to account for the feature of varying biases with respect to brightness temperature. HIRS measurements from the NOAA series of polar orbiting satellites are calibrated to a baseline satellite to form a homogeneous database for deriving atmospheric temperature and humidity profiles. During the last thirty years, the atmospheric carbon dioxide concentration increased significantly. The increased carbon dioxide concentration has a large impact on the HIRS channel observations in the carbon dioxide band. The channels that are most affected by the carbon dioxide increase are the mid-atmosphere sensing channels such as channels 5 and 6. Simulation from a radiative transfer model shows that the increase in the carbon dioxide in the last thirty years can decrease the observation values of these two channels by more than 1 C. A neural network technique is applied to derive atmospheric temperature and humidity profiles that account for the observed carbon dioxide change over the last thirty years.