Reinitialised versus continuous regional climate simulations using ALARO-0 coupled to the land surface model SURFEXv5

Abstract

Abstract. Dynamical downscaling in a continuous approach using initial and boundary conditions from a reanalysis or a global climate model is a common method for simulating the regional climate. The simulation potential can be improved by applying an alternative approach of reinitialising the atmosphere, combined with either a daily reinitialised or a continuous land surface. We evaluated the dependence of the simulation potential on the running mode of the regional climate model ALARO coupled to the land surface model Météo-France SURFace EXternalisée (SUR-FEX), and driven by the ERA-Interim reanalysis. Three types of downscaling simulations were carried out for a 10-year period from 1991 to 2000, over a western European domain at 20 km horizontal resolution: (1) a continuous simulation of both the atmosphere and the land surface, (2) a simulation with daily reinitialisations for both the atmosphere and the land surface and (3) a simulation with daily reinitialisations of the atmosphere while the land surface is kept continuous. The results showed that the daily reinitialisation of the atmosphere improved the simulation of the 2 m temperature for all seasons. It revealed a neutral impact on the daily precipitation totals during winter, but the results were improved for the summer when the land surface was kept continuous. The behaviour of the three model configurations varied among different climatic regimes. Their seasonal cycle for the 2 m temperature and daily precipitation totals was very similar for a Mediterranean climate, but more variable for temperate and continental climate regimes. Commonly, the summer climate is characterised by strong interactions between the atmosphere and the land surface. The results for summer demonstrated that the use of a daily reinitialised atmosphere improved the representation of the partitioning of the surface energy fluxes. Therefore, we recommend using the alternative approach of the daily reinitialisation of the atmosphere for the simulation of the regional climate.

Numerical Study of the Interaction between Oasis and Urban Areas within an Arid Mountains-Desert System in Xinjiang, China

“…The climate model ALARO-0 is the newer version (version 0) of the Aire Limitée Adaptation Dynamique Développement International (ALADIN) model that has been updated with physical parameterizations to enable simulations at 3-10 km mesh-size [32,33]. The ALADIN model, which is the limited area model version of the global scale Action de Recherche Petite Echelle Grande Echelle Integrated Forecast system (ARPEGE-IFS) [34], has been further developed with updated parameterizations for the physics part, such as the microphysics processes, and widely used in weather prediction and regional climate modelling [33,[35][36][37][38][39]. ARPEGE-IFS, used both at Météo-France and ECMWF (European Centre for Medium-Range Weather Forecasts), is a global spectral model with a Gaussian grid for the gird-point calculations.…”

“…The Météo-France SURFace Externalisée land surface model (SURFEX) [42], which consists of the ISBA (Interactions between Soil, Biosphere and Atmosphere) [43] scheme for natural surfaces and the TEB (Town Energy Balance) [44] scheme for urban surfaces, has been implemented in the ALARO-0 model [45]. The combined ALARO-SURFEX model has shown its potential for representing the regional climate and land surface processes [38,[46][47][48].…”

“…The oasis expansion effects (OASIS_Eff), urbanization effects either under default (URBAN_Eff_Def) or current state (URBAN_Eff_New) of oasis land cover and their combined effects (COMBI_Eff) can be derived from the difference of New_NoURB-Def_NoURB, Def_URB-Def_NoURB, CTL-New_NoURB and CTL-Def_NoURB, respectively (see Table 1). All simulations were initialized on 1 March 2016 and a 3-month spin-up period was used before the start of the analysis on 1 June, in order to ensure model equilibrium between external forcing and internal dynamics, especially in terms of soil variables [38]. A period of 3 months was sufficient for the deep soil moisture to reach equilibrium state (not shown).…”

Bridging the Gap Between Policy‐Driven Land Use Changes and Regional Climate Projections

“…The CNRM‐CM5.1 global climate model has been dynamically downscaled to perform simulations with ALARO‐SURFEX. The downscaling approach consisted of a daily update of the initial conditions and a continuously evolving land surface (Berckmans et al, ). The model allowed for a spin‐up period of 3 months to let the atmosphere and land surface advance to an equilibrium state (see Berckmans et al, , for more details on the spin‐up period).…”

“…The downscaling approach consisted of a daily update of the initial conditions and a continuously evolving land surface (Berckmans et al, ). The model allowed for a spin‐up period of 3 months to let the atmosphere and land surface advance to an equilibrium state (see Berckmans et al, , for more details on the spin‐up period). First, a one‐way nesting was applied to perform simulations at 20‐km horizontal resolution with its center over western Europe at 46.47°N and 2.58°E and a dimension of 149 × 149 horizontal grid points and 46 vertical levels (Figure ).…”