Last-decade progress in understanding and modeling the  land surface processes on the Tibetan Plateau

Lu, Hui; Zheng, Donghai; Yang, Kun; Yang, Fan

doi:10.5194/hess-24-5745-2020

Cited by 35 publications

(29 citation statements)

References 113 publications

(119 reference statements)

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“…Uncertainties in remote sensing data may affect their reliability as ground truth for evaluating the ELM simulations. The MODIS land surface albedo products have shown good consistencies with ground measurements (Moustafa et al, 2017;Wang et al, 2004), but the semi-empirical kerneldriven-model-based algorithms used to derive the MODIS land surface albedo do not account for topography explicitly (Schaaf et al, 2002;Hao et al, 2020), which may lead to large errors over rugged terrain (Hao et al, 2018a, b). MODIS snow cover data have shown relatively poor performance when compared to ground measurements, especially over the regions of TP with higher elevation and shallower snow depth (Pu et al, 2007;Yang et al, 2015;Zhang et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

A parameterization of sub-grid topographical effects on solar radiation in the E3SM Land Model (version 1.0): implementation and evaluation over the Tibetan Plateau

Hao

Bisht

Gu³

et al. 2021

Geosci. Model Dev.

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Abstract. Topography exerts significant influences on the incoming solar radiation at the land surface. A few stand-alone regional and global atmospheric models have included parameterizations for sub-grid topographic effects on solar radiation. However, nearly all Earth system models (ESMs) that participated in the Coupled Model Intercomparison Project (CMIP6) use a plane-parallel (PP) radiative transfer scheme that assumes that the terrain is flat. In this study, we incorporated a well-validated sub-grid topographic (TOP) parameterization in the Energy Exascale Earth System Model (E3SM) Land Model (ELM) version 1.0 to quantify the effects of sub-grid topography on solar radiation flux, including the shadow effects and multi-scattering between adjacent terrain. We studied the role of sub-grid topography by performing ELM simulations with the PP and TOP schemes over the Tibetan Plateau (TP). Additional ELM simulations were performed at multiple spatial resolutions to investigate the role of spatial scale on sub-grid topographic effects on solar radiation. The Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to compare with the ELM simulations. The results show that topography has non-negligible effects on surface energy budget, snow cover, snow depth, and surface temperature over the TP. The absolute differences in surface energy fluxes for net solar radiation, latent heat flux, and sensible heat flux between TOP and PP exceed 20, 10, and 5 W m−2, respectively. The differences in land surface albedo, snow cover fraction, snow depth, and surface temperature between TOP and PP exceed 0.1, 0.1, 10 cm, and 1 K, respectively. The magnitude of the sub-grid topographic effects is dependent on seasons and elevations and is also sensitive to the spatial scales. Although the sub-grid topographic effects on solar radiation are larger with more spatial details at finer spatial scales, they cannot be simply neglected at coarse spatial scales. When compared to MODIS data, incorporating the sub-grid topographic effects overall reduces the biases of ELM in simulating surface energy balance, snow cover, and surface temperature, especially in the high-elevation and snow-covered regions over the TP. The inclusion of sub-grid topographic effects on solar radiation parameterization in ELM will contribute to advancing our understanding of the role of the surface topography on terrestrial processes over complex terrain.

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Section: Discussionmentioning

confidence: 99%

A parameterization of sub-grid topographical effects on solar radiation in the E3SM Land Model (version 1.0): implementation and evaluation over the Tibetan Plateau

Hao

Bisht

Gu³

et al. 2021

Geosci. Model Dev.

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“…This study is also based on empirical fitting relationships. Furthermore, empirical formulations of r s s have developed to estimate evaporation from bare soil in LSMs for long‐term ET simulation with large spatial scale (Chang et al., 2019; Dong et al., 2020; Lu et al., 2020; J. Tang & Riley, 2013; Yang et al., 2011). Although the MOD16‐STM algorithm based on empirical parameters performs better at five independent grassland sites, it is still necessary to improve the proposed algorithm by considering the physical processes of soil evaporation and with the help of more observations to enhance the performance of the model in the future studies.…”

Section: Discussionmentioning

confidence: 99%

Section: Benefits and Challenges Of Parameterizing R S Smentioning

confidence: 99%

An Enhanced MOD16 Evapotranspiration Model for the Tibetan Plateau During the Unfrozen Season

Ling

Chen

et al. 2021

JGR Atmospheres

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Evapotranspiration (ET) is composed of soil evaporation (ETs), canopy transpiration (ETc), and canopy intercepted water evaporation (ETw), and it plays an indispensable role in the water and energy cycles of land surface processes. More accurate estimations of variations in ET are essential for natural hazard monitoring and water resource management. An improved algorithm for ETs with soil moisture and texture (SMT) and an optimized ETc based on the MOD16 model (MOD16‐STM) are proposed for the cold, arid, and semiarid regions of the Tibetan Plateau (TP). The nonlinear relationships between the soil surface resistance (rss) and soil surface hydration state in different soil textures were redefined by using five flux tower measurements over the TP. The value of the mean potential stomatal conductance per unit leaf area (CL) used for ETc calculation in grasslands was optimized at 0.0038 (m s−1). The MOD16‐STM was compared with the MOD16 and a soil water index‐based Priestley‐Taylor algorithm (SWI‐PT) at five independent sites. The results showed that the half‐hourly, daily, and monthly estimations from the MOD16‐STM were closer to observations than those from the other two models. The results indicated that the MOD16‐STM increased R2 by 0.2/0.05 and the index of agreement by 0.37/0.23 and deceased RMSE by 43.89/42.77 W m−2 and the absolute mean bias (|MB|) by 46.23/45.89 W m−2, when compared to the results of the MOD16 at daily/monthly scales. The results suggested that the MOD16‐STM will produce more accurate ET estimates over the flux sites and has great potential for ET estimation and land surface model improvement for the TP region.

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“…TP, known as the Third Pole, plays an important role in regulating the earth climate system (Lu et al, 2020;Yang et al, 2009). TP has complex topographic features, where the central part is relatively flat, and the western and southern regions have remarkable terrain undulations (Figure 1).…”

Section: Model Setup and Experiments Designmentioning

confidence: 99%

A Parameterization of Sub-grid Topographical Effects on Solar Radiation in the E3SM Land Model (Version 1.0): Implementation and Evaluation Over the Tibetan Plateau

Hao

Bisht

Gu³

et al. 2021

Preprint

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Abstract. Topography exerts significant influences on the incoming solar radiation at the land surface. A few stand-alone regional and global atmospheric models have included parameterizations for sub-grid topographic effects on solar radiation. However, nearly all Earth System Models (ESMs) that participated in the Coupled Model Intercomparison Project (CMIP6) use a plane-parallel (PP) radiative transfer scheme that assumes the terrain is flat. In this study, we incorporated a well-validated sub-grid topographic (TOP) parameterization in the Energy Exascale Earth System Model (E3SM) Land Model (ELM) version 1.0 to quantify the effects of sub-grid topography on solar radiation flux, including the shadow effects and multi-scattering between adjacent terrain. The Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to evaluate the performance of ELM. We studied the role of sub-grid topography by performing ELM simulations with the PP and TOP schemes over the Tibetan Plateau (TP). Additional ELM simulations were performed at multiple spatial resolutions to investigate the role of spatial scale on sub-grid topographic effects on solar radiation. When compared to MODIS data, incorporating the sub-grid topographic effects overall reduces the biases of ELM in simulating surface energy balance, snow cover and surface temperature especially in the high-elevation and snow-cover regions over the TP. Topography has non-negligible effects on surface energy budget, snow cover, and surface temperature over the TP. The absolute differences in surface energy fluxes for net solar radiation, latent heat flux, and sensible heat flux between TOP and PP exceed 20 W/m2, 10 W/m2, and 5 W/m2, respectively. The differences in land surface albedo, snow cover fraction, and surface temperature between TOP and PP exceed 0.1, 20%, and 1K, respectively. The magnitude of the sub-grid topographic effects is dependent on seasons and elevations, and is also sensitive to the spatial scales. Although the sub-grid topographic effects on solar radiation are more significant with more spatial details at finer spatial scales, they cannot be simply neglected at coarse spatial scales. The inclusion of sub-grid topographic effects on solar radiation parameterization in ELM will contribute to advancing our understanding of the role of the surface topography on terrestrial processes over complex terrain.

show abstract

Last-decade progress in understanding and modeling the land surface processes on the Tibetan Plateau

Cited by 35 publications

References 113 publications

A parameterization of sub-grid topographical effects on solar radiation in the E3SM Land Model (version 1.0): implementation and evaluation over the Tibetan Plateau

A parameterization of sub-grid topographical effects on solar radiation in the E3SM Land Model (version 1.0): implementation and evaluation over the Tibetan Plateau

An Enhanced MOD16 Evapotranspiration Model for the Tibetan Plateau During the Unfrozen Season

A Parameterization of Sub-grid Topographical Effects on Solar Radiation in the E3SM Land Model (Version 1.0): Implementation and Evaluation Over the Tibetan Plateau

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