Statistical temperature profile retrievals in clear-air using passive 118-GHz O2 observations

Linear statistical temperature profile retrievals from nadiral passive 118-GHz O₂ spectra are demonstrated using time- and space-coincident microwave observations and radiosonde profiles. Separate retrievals are demonstrated for winter and summer midlatitude conditions in clear air over land; observations during both day and night are included. The retrieval operator is a linear-statistical minimum mean-squared-error estimator. A purely statistical retrieval operator circumvents the effects of radiative transfer model uncertainties and biases in either the radiosonde or Millimeter-wave Temperature Sounder data. The retrieved profile rms errors are ~0.7-1.2 K for either the winter or summer tropospheres