title: Validation of integrated water vapor from OMI satellite instrument against reference GPS data at the Iberian Peninsula.
abstract: This paper shows the validation of integrated water vapor (IWV) measurements retrieved from the Ozone Monitoring Instrument (OMI), using as reference nine ground-based GPS stations in the Iberian Peninsula. The study period covers from 2007 to 2009. The influence of two factors, - solar zenith angle (SZA) and IWV -, on OMI-GPS differences was studied in detail, as well as the seasonal dependence. The pseudomedian of the relative differences is -1 ± 1% and the inter-quartile range (IQR) is 41%. Linear regressions calculated over each station show an acceptable agreement (R2up to 0.77). The OMI-GPS differences display a clear dependence on IWV values. Hence, OMI substantially overestimates the lower IWV data recorded by GPS (∼ 40%), while underestimates the higher IWV reference values (∼ 20%). In connection to this IWV dependence, the relative differences also show an evident SZA dependence when the whole range of IWV values are analyzed (OMI overestimates for high SZA values while underestimates for low values). Finally, the seasonal variation of the OMI-GPS differences is also associated with the strong IWV dependence found in this validation exercise.
authors.affiliation: Departamento de Física, Universidad de Extremadura, Badajoz, Spain; Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Badajoz, Spain. Electronic address: javier_vm@unex.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Vaquero-Martínez
authors.affiliation: Departamento de Física, Universidad de Extremadura, Badajoz, Spain; Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Badajoz, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Antón
authors.affiliation: Agencia Estatal de Meteorología (AEMET), Valladolid, Spain; Grupo de Óptica Atmosférica, Universidad de Valladolid, Valladolid, Spain.
authors.forename: José Pablo
authors.initials: JP
authors.lastname: Ortiz de Galisteo
authors.affiliation: Grupo de Óptica Atmosférica, Universidad de Valladolid, Valladolid, Spain.
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Cachorro
authors.affiliation: Smithsonian Astrophysical Observatory, Cambridge, MA, United States.
authors.forename: Huiqun
authors.initials: H
authors.lastname: Wang
authors.affiliation: Smithsonian Astrophysical Observatory, Cambridge, MA, United States.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: González Abad
authors.affiliation: Departamento de Física Aplicada, Universidad de Granada, Granada, Spain; Andalusian Institute for Earth System Research (IISTA-CEAMA), University of Granada, Autonomous Government of Andalusia, 18006, Granada, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Román
authors.affiliation: Departamento de Física, Instituto de Ciências da Terra, Escola de Ciências e Tecnología, Universidade de Évora, Évora, Portugal.
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Costa
keywords: GPS; IWV; OMI; Satellite; Validation; Water vapor