Vertical profiling of tropical precipitation using passive microwave observations and its implications regarding the crash of AF447

In a recent study (Haddad and Park, 2009), a method was proposed to use co-located simultaneous observations by the space-borne Tropical Rainfall Measuring Mission (TRMM) precipitation radar and microwave imager to train the microwave radiometer to retrieve vertical profiles of precipitation in the absence of radar observations. This radartrained passive-microwave approach was developed for mid-latitude precipitation regimes, where it was found that the inhomogeneity of the rain within the radiometer field of view was the main impediment to the estimation of the vertical distribution of rain. The approach constrains the brightness-temperature combinations used in the retrieval to lie in the orthogonal complement to the two main clear-sky principal components in brightness-temperature space. This note summarizes the results of applying this approach to observations over the Atlantic Inter-Tropical Convergence Zone during May 2009, and deriving estimates of the uncertainty in passive-microwave retrievals of the storm-top height and of the first vertical principal component of the rain. The results are illustrated on a serendipitous granule of data taken while the TRMM radar was unfortunately not operational, about twenty minutes after the last transmission from the ill-fated flight AF447.