Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.11765/7553
Validation of MODIS integrated water vapor product against reference GPS data at the Iberian Peninsula
Title: Validation of MODIS integrated water vapor product against reference GPS data at the Iberian Peninsula
Authors: Vaquero Martínez, JavierAntón, ManuelOrtiz de Galisteo, José Pablo ORCID RESEARCHERID Autor AEMETCachorro, Victoria E.João Costa, MaríaRomán, RobertoBennouna, Yasmine
Keywords: MODIS; Water vapor; IWV; GPS; Satellite
Issue Date: 2017
Citation: International Journal of Applied Earth Observation and Geoinformation. 2017, 63, p. 214–221
Publisher version: https://doi.org/10.1016/j.jag.2017.07.008
Abstract: In this work, the water vapor product from MODIS (MODerate-resolution Imaging Spectroradiometer) instrument, on-board Aqua and Terra satellites, is compared against GPS water vapor data from 21 stations in the Iberian Peninsula as reference. GPS water vapor data is obtained from ground-based receiver stations which measure the delay caused by water vapor in the GPS microwave signals. The study period extends from 2007 until 2012. Regression analysis in every GPS station show that MODIS overestimates low integrated water vapor (IWV) data and tends to underestimate high IWV data. R2 shows a fair agreement, between 0.38 and 0.71. Inter-quartile range (IQR) in every station is around 30%−45%. The dependence on several parameters was also analyzed. IWV dependence showed that low IWV are highly overestimated by MODIS, with high IQR (low precision), sharply decreasing as IWV increases. Regarding dependence on solar zenith angle (SZA), performance of MODIS IWV data decreases between 50◦ − 90◦ , while night-time MODIS data (infrared) are quite stable. The seasonal cycles of IWV and SZA cause a seasonal dependence on MODIS performance. In summer and winter, MODIS IWV tends to overestimate the reference IWV value, while in spring and autumn the tendency is to underestimate. Low IWV from coastal stations is highly overestimated (∼ 60%) and quite imprecise (IQR around 60%). On the contrary, high IWV data show very little dependence along seasons. Cloud-fraction (CF) dependence was also studied, showing that clouds display a negligible impact on IWV over/underestimation. However, IQR increases with CF, except in night-time satellite values, which are quite stable.
Sponsorship : This work was supported by the Spanish Ministry of Economy and Competitiveness through project CGL2014-56255-C2. Manuel Antón thanks Ministerio de Ciencia e Innovación and Fondo Social (RYC-2011- 08345) Europeo for the award of a postdoctoral grant (Ramón y Cajal).
URI: http://hdl.handle.net/20.500.11765/7553
ISSN: 0303-2434
Appears in Collections:Artículos científicos 2015-2018


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