https://hal-enpc.archives-ouvertes.fr/hal-00742382Lovejoy, S.S.LovejoyPinel, J.J.PinelSchertzer, DDSchertzerCEREVE - Centre d'Enseignement et de Recherche Eau Ville Environnement - AgroParisTech - ENPC - École des Ponts ParisTech - UPEC UP12 - Université Paris-Est Créteil Val-de-Marne - Paris 12Turbulent Flux based approaches to satellite precipitationHAL CCSD2008[SDE] Environmental SciencesEnpc, Ist2012-11-15 17:24:112022-08-05 14:38:112012-11-15 17:24:11enConference papers1Analysis of thousands of orbits of TRMM radar reflectivities have shown that over the range 4 to 20000 km, that their statistics are very close to those predicted for turbulent fluxes, i.e. they are conserved scale by scale and are therefore the outcomes of a pure multiplicative cascade processes (with deviations of the order of a few percent). If the rain rate is a power of the radar reflectivity (as is usually assumed), then this implies the same property for the rain rate. In contrast, analysis of the TRMM satellite passively sensed radiances in the visible, infra red and microwave bands show that they are qualitatively different, being quantitatively quite close to the statistics of turbulent passive "tracers". This difference implies that the conventional satellite rain techniques - in which the radiances are used directly for rain rate estimates - can at most be correctly calibrated at a single (subjectively chosen) scale/resolution. On the contrary if the (absolute) radiance gradients are used as estimates of the corresponding turbulent fluxes, then products of powers of the fluxes from different radiances will have qualitatively the correct type of statistics and it is straightforward to constrain them to have the same statistics as the precipitation over the entire scaling range. These flux based techniques are physically based on the underlying atmospheric cascade structure and have the advantage of potentially giving accurate precipitation estimates at any resolution over a wide range. Using the TRMM data, we compare and contrast various flux based techniques and compare them with conventional ones.