Preprints
https://doi.org/10.5194/gmd-2021-55
https://doi.org/10.5194/gmd-2021-55

Submitted as: development and technical paper 26 Mar 2021

Submitted as: development and technical paper | 26 Mar 2021

Review status: a revised version of this preprint was accepted for the journal GMD and is expected to appear here in due course.

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

Dalei Hao1, Gautam Bisht1, Yu Gu2, Wei‐Liang Lee3, Kuo-Nan Liou2, and L. Ruby Leung1 Dalei Hao et al.
  • 1Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA
  • 2Joint Institute for Regional Earth System Science and Engineering and Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
  • 3Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan

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.

Dalei Hao et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-55', Anonymous Referee #1, 22 Apr 2021
  • RC2: 'Review Comment on gmd-2021-55', Anonymous Referee #2, 01 Jul 2021
    • AC2: 'Reply on RC2', Hao Dalei, 26 Jul 2021
    • AC3: 'summary of the major changes', Hao Dalei, 26 Jul 2021
  • AC3: 'summary of the major changes', Hao Dalei, 26 Jul 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-55', Anonymous Referee #1, 22 Apr 2021
  • RC2: 'Review Comment on gmd-2021-55', Anonymous Referee #2, 01 Jul 2021
    • AC2: 'Reply on RC2', Hao Dalei, 26 Jul 2021
    • AC3: 'summary of the major changes', Hao Dalei, 26 Jul 2021
  • AC3: 'summary of the major changes', Hao Dalei, 26 Jul 2021

Dalei Hao et al.

Model code and software

daleihao/E3SM: TOP-ELM Dalei Hao http://doi.org/10.5281/zenodo.4549401

Dalei Hao et al.

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Short summary
Topography exerts significant influences on the incoming solar radiation at the land surface. This study incorporated a well-validated sub-grid topographic parameterization in E3SM land model (ELM) version 1.0. The results demonstrates that sub-grid topography has non-negligible effects on surface energy budget, snow cover, and surface temperature over the Tibetan Plateau and the ELM simulations are sensitive to spatial scales.