Observations of tropical cyclones with a 60, 118 and 183 GHz microwave sounder

Abstract

The Jet Propulsion Laboratory's High Altitude MMIC Sounding Radiometer (HAMSR) is a 25 channel microwave sounder with channels near the 60 GHz and 118 GHz oxygen lines and near the 183 GHz water vapor line. It participated in three hurricane field campaigns, CAMEX-4, TCSP and NAMMA The absolute calibration of the HAMSR brightness temperatures is shown to be better than 1.5 K. A non-linear iterative optimal estimation based retrieval algorithm is developed to retrieve atmospheric temperature and absolute humidity profiles. Comparisons of the retrieved profiles with coincident dropsonde profiles during NAMMA show excellent agreement at all altitudes, with the exception of a 30% residual dry bias in the absolute humidity profile above 4 km. The warm core structure of Hurricane Erin in 2001 and Hurricane Emily in 2005 is retrieved. The 60/118 GHz channels which have matched clear air weighting functions are used to assess convective intensity in the eye wall through the relative scatter darkening between the two channels.