Combined influence of atmospheric physics and soil hydrology on the simulated meteorology at the SIRTA atmospheric observatory

Abstract

International audienceThe identification of the land-atmosphere interactions as one of the key source of uncertainty in climate models calls for process-level assessment of the coupled atmosphere/land continental surface system in numerical climate models. To this end, we propose a novel approach and apply it to evaluate the standard and new parametrizations of boundary layer/convection/clouds in the Earth System Model (ESM) of Institut Pierre Simon Laplace (IPSL), which differentiate the IPSL-CM5A and IPSL-CM5B climate change simulations produced for the Coupled Model Inter-comparison Project phase 5 exercise. Two different land surface hydrology parametrizations are also considered to analyze different land-atmosphere interactions. Ten-year simulations of the coupled land surface/atmospheric ESM modules are confronted to observations collected at the SIRTA (Site Instrumental de Recherche par Télédection Atmosphérique), located near Paris (France). For sounder evaluation of the physical parametrizations, the grid of the model is stretched and refined in the vicinity of the SIRTA, and the large scale component of the modeled circulation is adjusted toward ERA-Interim reanalysis outside of the zoomed area. This allows us to detect situations where the parametrizations do not perform satisfactorily and can affect climate simulations at the regional/continental scale, including in full 3D coupled runs. In particular, we show how the biases in near surface state variables simulated by the ESM are explained by (1) the sensible/latent heat partitionning at the surface, (2) the low level cloudiness and its radiative impact at the surface, (3) the parametrization of turbulent transport in the surface layer, (4) the complex interplay between these processes. We also show how the new set of parametrizations can improve these biases

ReOBS: a new approach to synthesize long-term multi-variable dataset and application to the SIRTA supersite

“…This information together with many other SIRTA-ReOBS variables have been used recently in various studies (Cheruy et al, 2012;Chiriaco et al, 2014;Bastin et al, 2016). We first show examples of the two main ReOBS variables build from lidar measurements (SRhisto and STRAThisto) and we then describe how these data are used to built cloud fraction profiles.…”

“…This synergy aspect has been exploited in previous studies using the SIRTA-ReOBS data; for instance to study the diurnal cycle, the annual cycle and the interannual variability but for multiple variables, (Cheruy et al, 2012 andBastin et al, 2016), to study the different components and scales of the mixing layer depth variability (Pal and Haeffelin, 2015), and to perform in addition a dynamical analysis (Dione et al, 2016 andChiriaco et al, 2014). Figure 9 illustrates a possible synergy of multi-variables.…”

“…The multivariable synergy is also illustrated with a focus on the boundary layer processes. As mentioned before, SIRTA-ReOBS has been already used in previous published studies: Cheruy et al (2012) and Bastin et al (2016) used SIRTA-ReOBS to evaluate simulations from GCMs and from RCMs, respectively. In these studies, using SIRTA-ReOBS has led to identifying the processes responsible of the model biases.…”

“…The SIRTA observatory has been collecting data for 15 years from active and passive remote sensing, in situ measurements at the surface, in the ground and in the planetary boundary layer (PBL). Early versions of the SIRTA ReOBS dataset have already been used in scientific studies that required the multi-variables and multi-temporal scales available in the SIRTA-ReOBS dataset (Cheruy et al, 2012;Chiriaco et al, 2014;Haeffelin, 2015, Bastin et al, 2016;Dione et al, 2017). The ReOBS method has also been tested for other supersites for some variables (classical meteorology, radiative fluxes, heat fluxes): Cabauw (in the Netherlands) and Chilbolton (in England) supersites in the framework of the EUCLIPSE European project (European Union Cloud Intercomparison, Process Study and Evaluation project), CO-PDD (Cézeaux -Opme -Puy De Dôme at Clermont Ferrand in France) and P2OA (Plateforme Pyrénéenne d'Observations Atmosphériques at Lannemezan in France) in Dione et al (2016).…”

The LAB-Net Soil Moisture Network: Application to Thermal Remote Sensing and Surface Energy Balance

“…Soil moisture (SM) is one of the most essential climate variables, as it affects the hydrological and meteorological response of land's surface, playing a main role in land-atmosphere interactions due to its control on evapotranspiration [1]. Global scale maps of SM are crucial for the initialization of Numerical Weather Prediction (NWP) models, climate change studies, surface-atmosphere interactions, and agricultural applications.…”