Implementation of Groundwater Lateral Flow and Human Water Regulation in CAS‐FGOALS‐g3

Abstract

Both groundwater lateral flow (GLF) and human water regulation (HWR) significantly impact hydrological processes, climate, and even socioeconomic sustainable development. Reasonably representing these processes in climate system models is vital for improving hydrological predication and climate modeling. In this study, schemes including GLF and HWR were implemented into the Flexible Global Ocean-Atmosphere-Land System model grid-point version 3 (CAS-FGOALS-g3) to investigate the hydroclimatic effects of GLF and HWR. Three groups of simulations using CAS-FGOALS-g3 were conducted for the period from 1976 to 2010. Comparisons between the simulations and the observations show their good performance in reproducing the hydrological processes. Results show that soil moisture and latent heat flux increased when GLF was included in the western United States, northern Australia, and northern South America, along with a shallower water table depth. The largest increases in latent flux are located in regions without water and energy limitations. Increased summer precipitation occurred in the western United States due to the wetting and cooling effects of GLF. Latent heat flux significantly increases in three key regions of the world (central United States, north China plain, and northern India), caused by wetting surface soil due to irrigation. The atmosphere also responded to HWR, with cooling at the 850 hPa level over northern India and Pakistan. Decreased precipitation occurred in India because the upward movement was weaker as a result of HWR. GLF can replenish the groundwater depression cone caused by overexploitation, especially in thick aquifers. Plain Language Summary Groundwater lateral flow and human water regulation significantly impact hydrological processes and climate. In this study, we implemented the schemes including groundwater lateral flow and human water regulation into the Flexible Global Ocean-Atmosphere-Land System model to investigate the hydroclimatic effects of groundwater lateral flow and human water regulation. Comparisons between the simulations and the observations show their good performance in reproducing the hydrological processes. Groundwater lateral flow can replenish the groundwater depression cone caused by overexploitation, especially in thick aquifers. Human water regulation weakens the upward movement in India and reduces the summer precipitation. Both groundwater lateral flow and human water regulation affect soil moisture and energy fluxes at the land surface. These results suggest that groundwater lateral flow and human water regulation, which are generally simplified or excluded in climate system models, may provide missing parts for modeling water and energy fluxes and improving water management.

The Importance of Scale‐Dependent Groundwater Processes in Land‐Atmosphere Interactions Over the Central United States

“…However, in July and August, hardly any MCSs formed. A potential clue to this behavior was that most MCSs in May and June were forced by large scale frontal passages and other synoptic disturbances, while in July and August MCSs were weakly forced by local mesoscale circulations, which are highly related to local and regional convective instabilities and thermal gradients that are heavily modulated by soil moisture and temperature (Dirmeyer et al., 2009;Koster et al., 2004; Trier et al., 2004, 2008).…”

“…However, its role in weather and climate models has often been ignored due to the complexity of including a reasonable representation in the land‐surface model employed. The development of GW models (Maxwell et al., 2007; Wang et al., 2020) and especially the recent work by Miguez‐Macho et al. (2007) has provided a GW parameterization that helps overcome this challenge.…”

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However, its role in weather and climate models has often been ignored due to the complexity of including a reasonable representation in the land-surface model employed. The development of GW models (Maxwell et al, 2007;Wang et al, 2020) and especially the recent work by Miguez-Macho et al (2007) has provided a GW parameterization that helps overcome this challenge. This is important as climate model simulations and weather forecasts over the midcontinental midlatitude regions of the world often contain a warm and dry bias that has been notoriously difficult to reduce, especially in the central United States (U.S.) (Cheruy et al, 2014;

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Land Surface Model CAS‐LSM: Model Description and Evaluation

“…Since multiple modules are involved, the evaluation here is not necessarily complete. For a more in‐depth evaluation of the different modules of CAS‐LSM, please refer to the accompanying manuscript of the CAS‐FGOALS Special Issue (Wang, Xie, Xie et al, 2020; Wang, Xie, Jia et al, 2020; Wang, Xie, Liu et al, 2020).…”

Coupling of the land surface model CAS-LSM with the climate system model CAS-FGOALS-g3

“…Recently, the Chinese Academy of Sciences (CAS-LSM) land-surface model was developed based on CLM 4.5 (Oleson, 2013), which includes groundwater lateral flow, human water regulation, soil freeze-thaw front dynamics, riverine dissolved inorganic nitrogen transport, anthropologic heat release, urban water usage, and urban planning (Gao et al, 2019;Wang et al, 2020bWang et al, , 2020aWang et al, , 2020c. CAS-LSM has been included in the evaluation project of the Land Surface, Snow and Soil Moisture Model Intercomparison Project (LS3MIP;van den Hurk et al, 2016).…”