PIn. II. Comparative evaluation of SSM/I and TMI precipitable water estimate for the Mediterranean Sea

Abstract

To estimate integrated precipitable water vapour along with liquid water path and water vapour effective profile (i.e. standard atmospheric profile approximation), utilising the SSM/I and TMI radiometers, an operative procedure was developed and assessed. This procedure is based on a fast nonlinear physical inversion algorithm (PIn) developed by the authors. A large data-set of near-coincident TMI and SSM/I data acquisitions were collected and used to supply the procedure. Retrieved parameters were compared against retrievals achieved with well-accepted statistical algorithms, and consistency between TMI and SSM/I retrievals was confirmed. As far as TMI and SSM/I precipitable water retrieving consistency is concerned, this research revealed a linear relationship up to 20 kg/m 2 and a general overestimate of TMI retrieving, for higher values. A new algorithm for obtaining integrated precipitable water from TMI brightness temperatures was introduced and the goodness of its accuracy was reported. The procedure proved to be reliable and portable and its integrated precipitable water vapour retrieving was assessed to be as accurate as the best radiometric retrieving algorithms, reported in literature. For SSM/I data, developed procedure liquid water path estimates seemed to be in good agreement with statistical retrievals. Eventually the procedure provided effective water vapour vertical profiles which belong to a deterministic distribution area characterised by an upper and lower limit; it was confirmed that SSM/I and TMI vertical profile distribution areas mainly overlap even if they are characterised by different sensitivities to profile parameters. Index Terms-Passive microwave remote sensing, Integrated precipitable water vapour, TMI, SSM/I, Data fusion, Liquid water path I. INTRODUCTION The knowledge of the water cycle in the atmosphere is very useful for several applications, such as: weather forecasting, latent heat flux estimate, sea-atmosphere interaction. An additional process now being accounted for in some circulation models is the role of moist convection in transporting not only heat and moisture, but also momentum and chemical species over large distances in the vertical. Important remotely sensed parameters, related to the water cycle, are water vapour (WV), liquid and ice water content along with atmospheric temperature and pressure. The knowledge of these parameters-especially if obtained along

An operational procedure for precipitable and cloud liquid water estimate in non-raining conditions over sea: study on the assessment of the nonlinear physical inversion algorithm

“…Data were selected for clear sky conditions over the Mediterranean sea. 2 In order to compare and validate the results of the refined PIn procedure, total PW retrievals were analysed against SSM/I empirical estimates carried out applying the widely accepted Schluessel and Emery statistical algorithms. 9 The authors produced different algorithms; we utilised the following one: …”

“…1 This module is supplied with a first guess of parameters to be retrieved, and satellite measured brightness temperatures of an entire satellite scene. 2 For the entire scene, the following parameter images are generated:…”

“…1 Starting from such technique, an operative Procedure (named PIn, for Physical Inversion) has been developed and assessed to estimate integrated precipitable water vapour along with liquid water path and water vapour effective profile, utilising both the SSM/I and TMI radiometers. 2 The consistency of water vapour (WV) and liquid water path (LWP), estimated from both radiometers was examined, utilising a fast nonlinear physical inversion scheme developed for this purpose. 2 The inversion model, as well as the procedure, have been conceived and tuned for the Mediterranean area.…”

“…2 The consistency of water vapour (WV) and liquid water path (LWP), estimated from both radiometers was examined, utilising a fast nonlinear physical inversion scheme developed for this purpose. 2 The inversion model, as well as the procedure, have been conceived and tuned for the Mediterranean area.…”

PIn. I. An operational nonlinear physical inversion algorithm for precipitable and cloud liquid water estimate in nonraining conditions over sea

“…Such operational procedure has been tested for a couple of deployed microwave sensors (i.e. TMI and SSM/I) [14], and is ready to be utilised for radiometers which will be shortly operational (e.g. SSMI/S, AMSR).…”