Diurnal cycle of surface energy fluxes in high mountain terrain: High‐resolution fully coupled atmosphere‐hydrology modelling and impact of lateral flow

Abstract

Water and energy fluxes are inextricably interlinked within the interface of the land surface and the atmosphere. In the regional earth system models, the lower boundary parameterization of land surface neglects lateral hydrological processes, which may inadequately depict the surface water and energy fluxes variations, thus affecting the simulated atmospheric system through land‐atmosphere feedbacks. Therefore, the main objective of this study is to evaluate the hydrologically enhanced regional climate modelling in order to represent the diurnal cycle of surface energy fluxes in high spatial and temporal resolution. In this study, the Weather Research and Forecasting model (WRF) and coupled WRF Hydrological modelling system (WRF‐Hydro) are applied in a high alpine catchment in Northeastern Tibetan Plateau, the headwater area of the Heihe River. By evaluating and intercomparing model results by both models, the role of lateral flow processes on the surface energy fluxes dynamics is investigated. The model evaluations suggest that both WRF and coupled WRF‐Hydro reasonably represent the diurnal variations of the near‐surface meteorological fields, surface energy fluxes and hourly partitioning of available energy. By incorporating additional lateral flow processes, the coupled WRF‐Hydro simulates higher surface soil moisture over the mountainous area, resulting in increased latent heat flux and decreased sensible heat flux of around 20–50 W/m2 in their diurnal peak values during summertime, although the net radiation and ground heat fluxes remain almost unchanged. The simulation results show that the diurnal cycle of surface energy fluxes follows the local terrain and vegetation features. This highlights the importance of consideration of lateral flow processes over areas with heterogeneous terrain and land surfaces.

Large‐Scale Afforestation Enhances Precipitation by Intensifying the Atmospheric Water Cycle Over the Chinese Loess Plateau

“…Afforestation alters moisture and energy fluxes interchanged between the atmosphere and land surface by affecting surface characteristics (Baudena et al., 2021; Hagos et al., 2014; Z. Zhang et al., 2021). The Loess Plateau (LP) in China is an ideal platform to study the impact of large‐scale afforestation on the atmospheric water cycle, since it launched the world's largest afforestation program (Cao et al., 2019), the Grain for Green Program (GFGP) in 1999.…”

Improving predictions of land-atmosphere interactions based on a hybrid data assimilation and machine learning method

“…Because the water vapor from the East Asian monsoon was blocked by the Tibetan Plateau, most of the precipitation was concentrated in the southeastern part of the Qilian Mountains. Figure 15 shows that the high precipitation zone of the HRB was mainly located in the mountainous areas below 39.5 °N due to orographic lifting and convection (Liu et al, 2017;Zhang et al, 2021b). The main precipitation events were consistent between the WRF (OL) and WRF (DA-ML).…”

“…Therefore, there are some uncertainties in the precipitation simulation of the CMFD products in high-altitude mountainous areas (Zhang et al, 2021b). Strong wetting and cooling effects on vegetated areas were observed through the integration of LAI and SM, especially in the midstream oasis.…”

“…Although land surface models (LSMs) have been improved incrementally in the past decades, it is still challenging to effectively couple LSMs with atmospheric models to improve the description of land-atmosphere interactions (Chen and Dudhia, 2001;Liu et al, 2021). The success of the coupling depends not only on the sophisticated physical processes of the LSMs, but also on soil and vegetation characteristics and the accurate characterization of the water vapor fluxes at the land-atmosphere interface (Gentine et al, 2019;Zhang et al, 2021bZhang et al, , 2022.…”

“…Liu et al (2020) investigated the oasis-desert microclimate effects based on an improved CFD model and found that the oasis had a cold and wet island effect and wind shield effect. Zhang et al (2021b) applied the WRF-Hydro model in the HRB and emphasized the role of lateral flow in the regional precipitation circulation. These studies illustrate that mesoscale climate models can be used as essential tools to better understand regional climate and land-atmosphere interactions in the HRB.…”