L10 Design Document: MOSART One-way Coupling
The Design Document page provides a description of the algorithms, implementation and planned testing including unit, verification, validation and performance testing. Please read Step 1.3 Performance Expectations that explains feature documentation requirements from the performance group point of view.
Design Document
In the table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation, 
- competed, 
- in progress, 
- not done
Overview table for the owner and an approver of this feature
1.Description | One-ay coupling of MOSART river routing model to ALM |
| 2.Owner | Ruby Leung |
| 3.Created | |
| 4.Equ | |
| 5.Ver | |
| 6.Perf | |
| 7.Val | |
| 8.Approver | Peter Thornton, William Riley (Unlicensed) |
| 9.Approved Date | |
| V1.0 | Accepted |
Title: MOSART One-Way Coupling
Requirements and Design
ACME Land Group
Date:
Summary
This task includes:
1) Implementing a one-way coupling of the MOSART river routing model with ALM.
2) Evaluating the performance of the model using observations.
Requirements
Requirement: One-way coupling of MOSART with ALM
Date last modified:
Contributors: Hongyi Li, Anthony Craig, Ruby Leung
The MOSART river routing model has been developed and documented in Li et al. (2013) and evaluated globally as an offline model in Li et al. (2015). MOSART has been coupled with ALM through the flux coupler. ALM passes the runoff fields to MOSART, and MOSART passes back the river channel storage to ALM to maintain an overall water balance.
Li, H.-Y., L.R. Leung, A. Getirana, M. Huang, H. Wu, Y. Xu, J. Guo, and N. Voisin. 2015. “Evaluating Global Streamflow Simulations by a Physically-Based Routing Model Coupled With the Community Land Model.” J. Hydrometeor., 16, 948-971, doi:10.1175/JHM-D-14-0079.1.
Li, H., M.S. Wigmosta, H. Wu, M. Huang, Y. Ke, A.M. Coleman, and L.R. Leung. 2013. “A Physically Based Runoff Routing Model for Land Surface and Earth System Models.” J. Hydrometeor., 14(3), 808 – 828, doi: http://dx.doi.org/10.1175/JHM-D-12-015.1.
Requirement: Evaluation of the one-way coupled ALM-MOSART
Date last modified:
Contributors: Hongyi Li, Anthony Craig, Ruby Leung
Perform global simulations of ALM-MOSART and repeat similar analyses discussed in Li et al. (2015) for model evaluation.
Algorithmic Formulations
Design solution: Implementation of one-way coupling
Date last modified:
Contributors: Hongyi Li, Anthony Craig, Ruby Leung
Previously, CLM passes three runoff fields (QOVER, QDRAI, and QGWL) to RTM or MOSART. The last term, QGWL is not associated with a runoff generation process but is a residual term required to maintain water balance in glaciers, wetlands and lakes, and it can assume large negative values. RTM takes the total runoff (positive or negative), and returns the total channel storage (VOLR) to CLM to conserve the overall CLM water balance. In the previous implementation of MOSART, the total runoff is forced to be non-negative, but the total channel storage was calculated in the same way as done in RTM so it has no impact on the overall CLM water balance.
With the new implementation of MOSART in ALM, the three runoff terms are passed separately to MOSART:
1) If QGWL is negative, the negative values are passed directly to the ocean through the flux coupler. Only positive QGWL values are passed to MOSART and treated as runoff that directly goes to the main river channel.
2) ALM also passes QSUR and QSUB to MOSART that are routed through hillslope and tributary.
3) MOSART calculates total channel storage (main channel storage + tributary channel storage) and passes it back to ALM through the coupler.
Design solution: Metrics to evaluate MOSART simulated streamflow
Date last modified:
Contributors: Hongyi Li, Anthony Craig, Ruby Leung
This will follow the approach of Li et al. (2015) for global evaluation of simulated streamflow using GRDC data. In a nutshell, streamflow is evaluated separately in river basins influenced by human activities at different levels.
Design and Implementation
Implementation: One-way coupling of MOSART to ALM
Date last modified: // date
Contributors: Ruby Leung, Hongyi Li, Anthony Craig
In broad terms, the implementation of MOSART in ALM will follow the software engineering patterns established for previous implementation of MOSART within CLM. Significant differences include the level in the subgrid hierarchy at which ALM-to-MOSART coupling is realized, and the introduction of main channel and tributary storage terms passed back to ALM from MOSART.
Planned Verification and Unit Testing
Verification and Unit Testing: Verify one-way coupling of MOSART
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Contributors: Hongyi Li, Ruby Leung
Verification is performed by checking the fields that are passed from ALM to MOSART and vice versa through the flux coupler. MOSART has been verified previously through water balance check. The one-way coupled ALM-MOSART has been tested on Titan and passed the ACME_developer tests.
Planned Validation Testing
Validation Testing: Validate one-way coupling of MOSART
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Contributors: Hongyi Li, Ruby Leung
Validation is performed by comparing the MOSART simulated streamflow with observations.
Planned Performance Testing
Performance Testing: MOSART performance
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Contributors:
Performance will be evaluated using different number of processors on Titan.