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Impact of humidity biases on light precipitation occurrence: observations versus simulations / Sophie Bastin in Atmospheric chemistry and physics, vol 19 n° 3 (February 2019)  

Public [article]  inAtmospheric chemistry and physics > vol 19 n° 3 (February 2019) . - pp 1471 - 1490 Titre : Impact of humidity biases on light precipitation occurrence: observations versus simulations Type de document : Article/Communication Auteurs : Sophie Bastin, Auteur ; Philippe Drobinski, Auteur ; Marjolaine Chiriaco, Auteur ; Olivier Bock , Auteur ; Romain Roehrig, Auteur ; Clemente Gallardo, Auteur ; Dario Conte, Auteur ; Marta Domínguez Alonso, Auteur ; Laurent Li, Auteur ; Piero Lionello, Auteur ; Ana-Claudia Bernardes Parracho , Auteur Année de publication : 2019 Projets : HyMeX / Richard, Evelyne Article en page(s) : pp 1471 - 1490 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] bassin méditerranéen [Termes IGN] données GPS [Termes IGN] données météorologiques [Termes IGN] erreur systématique [Termes IGN] précipitation [Termes IGN] température de l'air [Termes IGN] teneur intégrée en vapeur d'eau Résumé : (auteur) This work uses a network of GPS stations over Europe from which a homogenized integrated water vapor (IWV) dataset has been retrieved, completed with colocated temperature and precipitation measurements over specific stations to (i) estimate the biases of six regional climate models over Europe in terms of humidity; (ii) understand their origins; and (iii) finally assess the impact of these biases on the frequency of occurrence of precipitation. The evaluated simulations have been performed in the framework of HYMEX/Med-CORDEX programs and cover the Mediterranean area and part of Europe at horizontal resolutions of 50 to 12 km. The analysis shows that models tend to overestimate the low values of IWV and the use of the nudging technique reduces the differences between GPS and simulated IWV. Results suggest that physics of models mostly explain the mean biases, while dynamics affects the variability. The land surface–atmosphere exchanges affect the estimation of IWV over most part of Europe, especially in summer. The limitations of the models to represent these processes explain part of their biases in IWV. However, models correctly simulate the dependance between IWV and temperature, and specifically the deviation that this relationship experiences regarding the Clausius–Clapeyron law after a critical value of temperature (Tbreak). The high spatial variability of Tbreak indicates that it has a strong dependence on local processes which drive the local humidity sources. This explains why the maximum values of IWV are not necessarily observed over warmer areas, which are often dry areas. Finally, it is shown over the SIRTA observatory (near Paris) that the frequency of occurrence of light precipitation is strongly conditioned by the biases in IWV and by the precision of the models to reproduce the distribution of IWV as a function of the temperature. The results of the models indicate that a similar dependence occurs in other areas of Europe, especially where precipitation has a predominantly convective character. According to the observations, for each range of temperature, there is a critical value of IWV from which precipitation starts to increase. The critical values and the probability of exceeding them are simulated with a bias that depends on the model. Those models, which generally present light precipitation too often, show lower critical values and higher probability of exceeding them. Numéro de notice : A2019-277 Affiliation des auteurs : Géodésie+Ext (mi2018-2019) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/acp-19-1471-2019 Date de publication en ligne : 04/02/2019 En ligne : https://doi.org/10.5194/acp-19-1471-2019 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95383 [article]