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Impact of humidity biases on light precipitation occurrence: observations versus simulations
Title: Impact of humidity biases on light precipitation occurrence: observations versus simulations
Authors: Bastin, SophieDrobinski, PhilippeChiriaco, MarjolaineBock, OlivierRoehrig, RomainGallardo, ClementeConte, DarioDomínguez Alonso, MartaLi, LaurentLionello, PieroParracho, Ana Claudia
Keywords: Humidity; Precipitation; GPS
Issue Date: 2019
Publisher: European Geosciences Union
Citation: Atmospheric Chemistry and Physics. 2019, 19(3), p. 1471–1490
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Abstract: 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.
Sponsorship : This work is a contribution to the HyMeX program (HYdrological cycle in The Mediterranean EXperiment) through INSU-MISTRALS support and the MEDCORDEX program (Coordinated Regional climate Downscaling EXperiment–Mediterranean region). This research has received funding from the French National Research Agency (ANR) project REMEMBER (grant ANR-12-SENV-001) and is a contribution to the VEGA project through LEFE/INSU support, to the EECLAT project through LEFE-INSU and CNES supports and to the GNSS4SWEC COST action ES1206 through EU support. It was supported by the IPSL group for regional climate and environmental studies, with granted access to the HPC resources of GENCI/IDRIS (under allocation i2011010227), by SIRTA Working Group “Climate studies” and by the national infrastructure ACTRIS-FR, identified on the French road map for Research Infrastructures, published by the Ministry of Research. The SIRTA-ReOBS effort also benefited from the support of the L-IPSL funded by ANR under the “Programme d'Investissements d'Avenir” (grant ANR-10-LABX-0018) and by the EUCLIPSE project funded by the European Commission under the Seventh Framework Program (grant no. 244067).
ISSN: 1680-7316
Appears in Collections:Artículos científicos 2019-2022

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