Application of an optimal estimation inverse method to GPS/MET bending angle observations

Palmer et al. [2000] describes an optimal estimation inverse method for rad io occultation (RO) bending angle measurements to retrieve simultaneously t emperature, humidity, and surface pressure, outlines quality control proced ures for retrieved profiles; and investigates the results from numerical si mulations. Here we present retrievals that use bending angle observations f rom the Global Positioning System Meteorology (GPS/MET) satellite instrumen t and a priori information from the European Centre for Medium-Range Weathe r Forecasts analyses. Retrieved profiles are compared with correlative radi osondes, United Kingdom Meterological Office UKMO) model analyses, and retr ievals from the conventional inverse method, Retrieved temperature profiles are generally colder than analyses but agree with the conventional inverse method to within I K. Water vapor retrievals are generally drier than the UKMO analyses and wetter than the radiosonde profiles. Quality of retrieved surface pressure values are related to the extent to which RO observations reach into the troposphere. Low-latitude retrievals make large adjustments to surface pressure and tropospheric temperatures, which are directly link ed to the lack of water vapor above 300 hPa in the inverse model, consisten t with previous studies. A study of individual occultations at low and high latitude shows that the optimal retrievals are able to resolve small-scale atmospheric structure exhibited by the conventional inverse method and col located radiosondes, not shown by analyses.