Abstract
Understanding the differences between regional simulations of land-atmosphere interactions and near-surface conditions is crucial for a more reliable representation of past and future climate. Here, we explore the effect of changes in the model's horizontal resolution on the simulated energy balance at the surface and near-surface conditions using the Weather Research and Forecasting (WRF) model. To this aim, an ensemble of twelve simulations using three different horizontal resolutions (25 km, 50 km and 100 km) and four different Land Surface Model (LSM) configurations over North America from 1980 to 2013 is developed. Our results show that finer resolutions lead to higher surface net shortwave radiation and maximum temperatures at mid- and high latitudes. At low latitudes over coastal areas, an increase in resolution leads to lower values of sensible heat flux and higher values of latent heat flux, as well as lower values of surface temperatures and higher values of precipitation and soil moisture in summer. The use of finer resolutions leads then to an increase in summer values of latent heat flux, convective and non-convective precipitation and soil moisture at low latitudes. The effect of the LSM choice is larger than the effect of horizontal resolution on the near-surface temperature conditions. By contrast, the effect of the LSM choice on the simulation of precipitation is weaker than the effect of horizontal resolution, showing larger differences among LSM simulations in summer and over regions with high latent heat flux. Comparison between observations and the simulation of daily maximum and minimum temperatures and accumulated precipitation indicates that the CLM4 LSM yields the lowest biases in maximum and minimum mean temperatures, but the highest biases in extreme temperatures. Increasing horizontal resolution leads to larger biases in accumulated precipitation over all regions particularly in summer. The reasons behind relate the partition between convective and non-convective precipitation, specially noticeable over western US.
Highlights
Most assessments of climate change impacts on ecosystems and societies are based on projections performed by regional climate models (RCMs) and/or earth system models (ESMs; IPCC, 2013, 2019)
The net radiation results from adding net shortwave and longwave radiations, whose mean values have similar spatial distributions but with opposite sign (Fig. 2a). This indicates that more shortwave radiation reaches the land surface than is reflected due to surface albedo, while the radiation emitted from the soil due to its surface temperature, is higher than the longwave radiation reaching the soil surface (Fig. 2a)
This study has shown the effect of changes in horizontal resolution and land surface model (LSM) choice on the simulation of energy fluxes at the surface and temperature and water conditions near the surface
Summary
Most assessments of climate change impacts on ecosystems and societies are based on projections performed by regional climate models (RCMs) and/or earth system models (ESMs; IPCC, 2013, 2019). Exploring inter-model differences in present climate simulations is necessary to understand their contribution to the spread in future climate projections and to better characterize or even reduce the uncertainty in the simulation of the response to a given scenario (Cubasch et al, 2013). Understanding intermodel differences is important for paleoclimatic studies relying on regional climate model simulations to bridge the gap between the local character of proxy reconstructions and ESM global simulations (e.g., PALEOLINK; GómezNavarro et al, 2018). Land–atmosphere interactions have been studied in the evaluation of climate model simulations, applying several metrics to characterize surface energy fluxes and near-surface conditions (Koven et al, 2013; Dirmeyer et al, 2013; Sippel et al, 2017; García-García et al, 2019)
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