Presentación realizada en: 8th G-VAP Workshop celebrado en la sede central de AEMET en Madrid, 13 al 14 de junio de 2019

Calbet, Xavier

English

Agencia Estatal de Meteorología

Consistency between Measurements13-14 June 2019GEWEX G-VAP WorkshopXavier Calbet, AEMET (xcalbeta@aemet.es)Consistency between Measurements● Different Measurement Systems should give the “same” (consistent) values of the parameter being measured● For Water Vapour, there are some examples where measurements are consistent and some in which they are not● Ideally, before measurements from different systems are combined they should be proven to be consistent → Otherwise combination becomes difficultExamples of NO ConsistencyBrogniez et al., AMT, 2016183 GHz BiasesExamples of NO ConsistencySaunders, EUMETSAT Conference, 2018OLCITCWVExamples of NO ConsistencyOEM IASI WV Retrievals need R matrix values much bigger than instrument noiseJ = ( y - F(x) )T R-1 ( y – F(x) ) + ( x – xa )T B-1 ( x – xa )Calbet, arxiv, 2012RExamples of ConsistencyConsistency between GRUAN sondes, LBLRTM and IASI Calbet et al., AMT, 2017Examples of ConsistencyConsistency between GRUAN and MW over homogeneous scenes Bobryshev et al., IEEE Trans. Geo. Rem. Sen., 2018What is going on?● Is there or is there NOT consistency?● Are we missing anything?● Perhaps the difference is in the homogeneity or inhomogeneity of the scenes → How much water vapour varies within the Field of View of the instrumentEffect of FOV inhomogeneityCan turbulence (= inhomogeneity) within the field of view cause significant biases in radiative transfer modelling at the 183 GHz band?Calbet et al., AMT, 2018Effect of FOV inhomogeneityCan turbulence=inhomogeneity within the Field of View cause significant biases in radiative transfer modelling in MW or IR?Effect of FOV inhomogeneityWhy can turbulence within the FOV cause big differences in BT?Retrieving Turbulence?● We can try Optimal Estimation Method (OEM) like techniques to retrieve the T and WV profiles and also WV Turbulence (= FOV inhomogeneity)● Do we retrieve anything reasonable?Retrieving Turbulence?● We try OEM with an R exactly equal to instrument noise → We know this has failed before = too unconstrained system● We use as background ECMWF analyses● What happens when retrieving also turbulence?Retrieving Turbulence?Retrieving Turbulence?How does it look spatially?Retrieving Turbulence?How does it look spatially? → Comparison with MSG seems consistentMSG IR Image 17:00Retrieving Turbulence?Radiance residuals? Retrievals done for MHS → MHS Residuals should be low → How about residuals for IASI?Summary● Ideally we should strive for consistency before combining different measurements● There are still some remaining inconsistencies between different WV measurements● Inhomogeneities within the FOV (turbulence) might explain the remaining inconsistencies● Retrievals with turbulence (inhomogeneities) provide different humidity values with respect to OEM● This would potentially allow the retrievals of turbulence, but would also complicate retrievals● High spatial resolution humidity fields would help in this puzzle

Consistency between Measurements

https://repositorio.aemet.es/bitstream/20.500.11765/12498/1/GVAP_WS8_01_Calbet.pdf

Consistency between Measurements

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Agencia Estatal de Meteorología