Soil Moisture‐Temperature Coupling in a Set of Land Surface Models

Abstract

The land surface controls the partitioning of water and energy fluxes and therefore plays a crucial role in the climate system. The coupling between soil moisture and air temperature, in particular, has been shown to affect the severity and occurrence of temperature extremes and heat waves. Here we study soil moisture‐temperature coupling in five land surface models, focusing on the terrestrial segment of the coupling in the warm season. All models are run off‐line over a common period with identical atmospheric forcing data, in order to allow differences in the results to be attributed to the models' partitioning of energy and water fluxes. Coupling is calculated according to two semiempirical metrics, and results are compared to observational flux tower data. Results show that the locations of the global hot spots of soil moisture‐temperature coupling are similar across all models and for both metrics. In agreement with previous studies, these areas are located in transitional climate regimes. The magnitude and local patterns of model coupling, however, can vary considerably. Model coupling fields are compared to tower data, bearing in mind the limitations in the geographical distribution of flux towers and the differences in representative area of models and in situ data. Nevertheless, model coupling correlates in space with the tower‐based results ( r = 0.5–0.7), with the multimodel mean performing similarly to the best‐performing model. Intermodel differences are also found in the evaporative fractions and may relate to errors in model parameterizations and ancillary data of soil and vegetation characteristics.

Evaluating the Contribution of Land‐Atmosphere Coupling to Heat Extremes in CMIP5 Models

“…Here we similarly found the IPSL models to better represent the observed behavior in the wet regions (with Ω EF, T max ranging from −3.9 to −0.2). These findings also agree with Gevaert et al () who showed that JULES and SURFEX (ISBA) have stronger ET‐temperature coupling in global offline simulations during the warm season compared to ORCHIDEE.…”

Land–atmospheric feedbacks during droughts and heatwaves: state of the science and current challenges

“…The advantage of performing coupled model simulations in which land parameters (i.e., vegetation cover and soil moisture) are intervened in one of the experiments is that differences with the control run are unambiguous in terms of causality . However, the degree of land–atmospheric coupling varies greatly from model to model, and the results of these experiments are difficult to validate using field measurements, even though recent studies have aimed for such a validation . On the other hand, ground and satellite measurements reflect the actual variability in our coupled system.…”

“…While this topic has received much interest in recent years, the adequate model representation of the terrestrial segment of the land–atmospheric coupling has arguably received less attention . In particular, the representation of evaporation in land surface schemes remains a bottleneck in land–atmospheric feedback studies . Above, we highlighted the strong dependency of land evaporation on soil properties and vegetation traits—such as stomatal/xylem conductance or rooting depth—which are largely unconstrained in climate and ecosystem models .…”

An Evaluation of Soil Moisture Anomalies from Global Model-Based Datasets over the People’s Republic of China

“…Several studies have used model-simulated soil moisture estimates to study regions over the globe, where soil moisture impacts the atmosphere significantly [1,4,14]. Additionally, these products have become a reliable source of information within merging schemes of satellite and ground observation datasets as references.…”