Title: Exploring topography-based methods for downscaling subgrid precipitation for use in Earth System Models

Abstract

Topography exerts major control on land surface processes. To improve representation of topographic impacts on land surface processes, a new topography-based subgrid structure has been introduced to the Energy Exascale Earth System Model to represent the subgrid heterogeneity of surface elevation. To take advantage of the new subgrid structure for improving land surface modeling, this study explores four variations of topography-based methods for downscaling grid precipitation to the corresponding subgrids. In the first three methods, the deviation of the subgrid precipitation from the grid’s is equal to the grid precipitation multiplied by the ratio of the elevation difference between the subgrid and grid mean to a specified elevation equals to the grid elevation, the difference between the maximum and minimum subgrid elevation, and the maximum subgrid elevation, respectively. The second method limits the ratio to 0.5 to avoid extreme values on mountains and the third method accounts for the slope effect. The fourth method is similar to the third method except that the Froude Number is used to limit the numerator in a blocking regime of the ambient flow. The downscaled precipitation is evaluated using the PRISM precipitation data over the U.S. using statistical metrics. Results show that by accountingmore » for topographic slope besides elevation, the third and fourth methods show clear advantages over the first and second methods. Furthermore, introducing the Froude Number in the fourth method improves downscaling skill and shows consistent advantages over the third method in areas with larger subgrid heterogeneity across different grids sizes.« less

Authors:

Tesfa, Teklu K. ^[1]; Leung, Lai-Yung  ^[1];

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• Search OSTI.GOV for ORCID "0000-0002-3221-9467"
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Ghan, Steven J.  ^[2]

• Search OSTI.GOV for author "Ghan, Steven J."
• Search OSTI.GOV for ORCID "0000-0001-8355-8699"
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+ Show Author Affiliations

1. BATTELLE (PACIFIC NW LAB)
2. EMERITUS PROGRAM

Publication Date:

2020-03-16

Research Org.:

Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1606318

Report Number(s):

PNNL-SA-146636

DOE Contract Number:  

AC05-76RL01830

Resource Type:

Journal Article

Journal Name:

Journal of Geophysical Research: Atmospheres

Additional Journal Information:

Journal Volume: 125; Journal Issue: 5

Country of Publication:

United States

Language:

English