A subbasin-based framework to represent land surface processes in an Earth system model 1Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland WA, 99352, USA
2Base of the State Key Laboratory of Urban Environment Process and Digital Modelling, Department of Resource Environment and Tourism, Capital Normal University, 105 Xi San Huan Bei Lu, Beijing, 100048, China
3Department of Hydraulic Engineering, State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, 100084, China
Received: 10 Apr 2013 – Published in Geosci. Model Dev. Discuss.: 03 May 2013 Abstract. Realistically representing spatial heterogeneity and lateral land surface
processes within and between modeling units in Earth system models is
important because of their implications to surface energy and water
exchanges. The traditional approach of using regular grids as computational
units in land surface models may lead to inadequate representation of subgrid
heterogeneity and lateral movements of water, energy and carbon fluxes. Here
a subbasin-based framework is introduced in the Community Land Model (CLM),
which is the land component of the Community Earth System Model (CESM). Local
processes are represented in each subbasin on a pseudo-grid matrix with no
significant modifications to the existing CLM modeling structure. Lateral
routing of water within and between subbasins is simulated with the subbasin
version of a recently developed physically based routing model, Model for
Scale Adaptive River Transport (MOSART). The framework is implemented in two
topographically and climatically contrasting regions of the US: the Pacific
Northwest and the Midwest. The relative merits of this modeling framework, with
greater emphasis on scalability (i.e., ability to perform consistently across
spatial resolutions) in streamflow simulation compared to the grid-based
modeling framework are investigated by performing simulations at
0.125°, 0.25°, 0.5°, and 1° spatial resolutions.
Comparison of the two frameworks at the finest spatial resolution showed that
a small difference between the averaged forcing could lead to a larger difference
in the simulated runoff and streamflow because of nonlinear processes. More
systematic comparisons conducted using statistical metrics calculated between
each coarse resolution and the corresponding 0.125°-resolution
simulations showed superior scalability in simulating both peak and mean
streamflow for the subbasin based over the grid-based modeling framework.
Scalability advantages are driven by a combination of improved consistency in
runoff generation and the routing processes across spatial resolutions.
Revised: 14 Mar 2014 – Accepted: 25 Mar 2014 – Published: 20 May 2014
Citation: Tesfa, T. K., Li, H.-Y., Leung, L. R., Huang, M., Ke, Y., Sun, Y., and Liu, Y.: A subbasin-based framework to represent land surface processes in an Earth system model, Geosci. Model Dev., 7, 947-963, doi:10.5194/gmd-7-947-2014, 2014.