Coupling Climate and Hydrological Models Interoperability Through Web Services

1. Coupling Climate and Hydrological ModelsInteroperability Through Web Services

2. Outline • Project Objective • Motivation • System Description • Components • Frameworks • System Driver • Logical Workflow • Data Flow • Architecture • Future Directions

3. Project Objective The development of a two-way coupled, distributed, service-based modeling system comprised of an atmospheric climate model using a standard ESMF interface and a hydrological model that utilizes standard interfaces from that domain.

4. Motivation and Background • Hydrological impact studies can be improved when forced with data from climate models; hydrological feedbacks can affect climate • Atechnology and scale gap exists: • Many hydrological models have limited scalability, run on desktop computers, and have watershed-sized domains • Manyclimate models are highly parallel, run on high performance supercomputers and have global domains • However, scales are slowly converging (e.g. high resolution climate models, hydrological systems of greater extent), and this provides opportunities to explore new coupled model configurations and modes of coupling

5. Approach • Leveraging frameworks (ESMF, OpenMI) that can operate as web services is a way to implement loose coupling between such systems – this has many advantages • Loose coupling can be implemented with minimal source code changes needed to run the models • Standard connectors between various frameworks and interfaces can be written, encouraging broad interoperability • A web service approach enables model components to be integrated with a heterogeneous network of other services (data retrieval and post-processing, etc.) • The web service approach is well understood • The approach leverages substantial investments in converting operational weather and water models to ESMF

6. System Description • SWAT (hydrology model) runs on a PC • CAM (climate model) runs on a high performance computer • Wrappers for both SWAT and CAM provide an OpenMI interface to each model • Driver (OpenMI Configuration Editor) uses OpenMI interface to timestep through models via wrappers Personal Computer Driver OpenMI SWAT CAM OpenMI Wrapper High Performance Computer • The CAM run is invoked through ESMF web services • CAM output data is streamed to a CAM wrapper via ESMF web services ESMF Web Services ESMF CAM Component

7. Components: SWAT • The hydrological model chosen for this project is the Soil Water Assessment Tool (SWAT) • It is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds • It was chosen for this project because it is widely used, open source, and has a standard interface (OpenMI)

8. Components: CAM • The atmospheric model chosen for this system is the Community Atmospheric Model (CAM5), part of the Community Climate System Model (CESM1.0.3) • It was chosen because it is widely used, open source, and has a standard interface (ESMF)

9. Frameworks: Earth System Modeling Framework • ESMF isa high-performance, flexible, operational-quality software infrastructure that increases the ease of use, performance portability, interoperability, and reuse inEarth science applications • It provides an architecture for composing complex, coupled modeling systems and can support fully unstructured, logically rectangular, and observational data structures • It is highly portable (24+ platforms), highly scalable (tested to 16K+ processors), and includes 4500+ tests and examples • Web services included in the ESMF distribution allow any networked ESMF component to be available as a web service.

10. Frameworks: OpenMI • The OpenMI Software Development Kit (SDK) is a software library that provides a standardized interface that focuses on time dependent data transfer • Primarily designed to work with systems that run simultaneously, but in a single-threaded environment [Gregerson et al., 2007] • The primary data structure in OpenMI is the ExchangeItem, which comes in the form of an InputExchangeItem and an OutputExchangeItem (single point, single timestep)

11. The system driver • Controls the application flow using a web service architecture • Implemented using OpenMI’s Configuration Editor • Convenient tool for the testing of the OpenMI implementations and model interactions

12. Hardware Architecture • The atmospheric model runs on a high performance platform, often split into Compute Notes and Login Nodes • Access to the Compute Nodes must be through the Login Nodes • Access to the Login Nodes is through the Virtual Server (Web Svcs) Personal Computer (Windows) High Performance Computer Virtual Linux Server • The Client contains the OpenMI and SWAT software, which run on a Windows platform. Login Nodes (kraken) Compute Nodes (kraken)

13. Software AchitectureClient • Configuration Editor is the driver… it is used to link the models and trigger the start of the run. • Hydrological model (SWAT 2005) is a version wrapped to work with OpenMI • Access to the atmospheric model (CAM) is done through “wrapper” code that accesses ESMF web services via an OpenMI interface Personal Computer (Windows) OpenMI Configuration Editor OpenMI SWAT 2005 CAM OpenMI Wrapper … to Web Services

14. Software ArchitectureServer HPC Login Nodes Linux Server (Web Svr) Tomcat/Axis2 Process Controller Registrar SOAP Svcs Job Scheduler • In some high performance systems, access to nodes can be restrictive. • Access to/from external systems can be controlled via “gateway” systems using web services. • Running applications (such as CAM Component Svc) on Compute Nodes must be handled by a job scheduler. HPC Compute Nodes Comp Svc Comp Svc Comp Svc CAM CAM CAM

15. Logical Flow - Startup When loading models into the Configuration Editor, each model is initialized. For CAM, this involves starting a “New Client” in the Process Controller, which submits a new CAM Component Service using the Job Scheduler. Personal Computer (Windows) Config Editor 1 HPC Login Nodes 1 3 Process Controller 5 OpenMI Registrar SWAT 2005 CAM Wrapper 4 Job Scheduler 7 2 Linux Server Comp Svc Web Svcs 6 HPC Compute Nodes CAM Initialize New Client New Client Submit Job Status = SUBMITTED Instantiate Job (Comp Svc) Status = READY

16. Logical Flow - Status The status of the CAM Component Service is checked often throughout the workflow. The status is stored in the Registrar, so it can be retrieved via the Process Controller. Personal Computer (Windows) Config Editor HPC Login Nodes 2 Process Controller 3 OpenMI Registrar SWAT 2005 CAM Wrapper Job Scheduler 1 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM Get Status Get Status Get State

17. Logical Flow - Initialize Before the models can be run, they need to be initialized. For CAM, the Initialize call is sent to the CAM Component Service via Web Services and the Process Controller. The CAM Component Svc updates it’s status in the Registrar prior to and after Initialization. Personal Computer (Windows) Config Editor 1 HPC Login Nodes 1 3 Process Controller OpenMI Registrar SWAT 2005 CAM Wrapper 5 Job Scheduler 4 6 2 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM Prepare Initialize Initialize Initialize Status = INITIALIZING Status = INIT_DONE

18. Logical Flow – Timestep (Run) For each Timestep in SWAT, the trigger to run a timestep in CAM is a Get Values request in the OpenMI Interface. The Run Timestep request is passed to the CAM Component Service and the Component Service sets the output data making it available for later retrieval (see Get Data). Personal Computer (Windows) Config Editor 1 HPC Login Nodes 4 Process Controller OpenMI 2 Registrar SWAT 2005 CAM Wrapper 6 Job Scheduler 5 8 3 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM 7 Get Values Get Values Run Timestep Run Timestep Run Timestep Status = RUNNING Set Output Data Status = TIMESTEP_DONE

19. Logical Flow – Timestep (Get Data) After each timestep run, the output data is then fetched from the CAM Component Service via the Web Services and Process Controller. The first time fetching data, a description of the data structure is requested. This description is then used for the remaining timesteps. Personal Computer (Windows) Config Editor HPC Login Nodes 2 Process Controller OpenMI Registrar SWAT 2005 5 CAM Wrapper 3 Job Scheduler 6 1 4 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM Get Data Desc* Get Data Desc* Get Data Desc* Get Data Get Data Get Data * one time only

20. Logical Flow - Finalize After all timesteps have completed, the models need to be finalized. For CAM, the Finalize call is sent to the CAM Component Service via Web Services and the Process Controller. The CAM Component Svc updates its status in the Registrar prior to and after finalization. Personal Computer (Windows) Config Editor 1 HPC Login Nodes 1 3 Process Controller OpenMI Registrar SWAT 2005 CAM Wrapper 5 Job Scheduler 4 6 2 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM Finish Finalize Finalize Finalize Status = FINALIZING Status = FINAL_DONE End Client (Next Slide)

21. Logical Flow – End Client After the Finalize call, the CAM Component Service is done, so the CAM Wrapper closes it out by calling End Client. This call results in the CAM Component Service completing it’s loop and exiting as well as the Process Controller removing all references to the client. Personal Computer (Windows) Config Editor HPC Login Nodes 2 Process Controller 5 OpenMI Registrar SWAT 2005 CAM Wrapper Job Scheduler 3 1 Linux Server Comp Svc Web Svcs HPC Compute Nodes CAM 4 End Client End Client Kill Server Exit Service Loop Status = COMPLETED

22. Logical Workflow Driver SWAT/OpenMI ATM/OpenMI Wrapper ESMF Web Services ESMF Component Initialize Initialize NewClient Prepare Prepare Initialize ESMF_GridCompInitialize GetValues GetValues RunTimestep ESMF_GridCompRun GetData ValueSet ValueSet Finish Finish Finalize ESMF_GridCompFinalize Dispose Dispose EndClient

23. Data FlowOne-Way Coupling High Performance Computer Personal Computer CAM/OpenMI Wrapper GetValues Output Exchange Item ESMF Component/CAM GetDataValues ESMF State SWAT/OpenMI Input Exchange Item • The data is pulled from the CAM Component to SWAT via the wrapper , initiated by the OpenMI GetValues call; this call is made once per timestep. • Data is exchanged between CAM and SWAT using the OpenMI Exchange Item structures that handle the translation from grid to point values

24. Data FlowTwo-Way Coupling High Performance Computer Personal Computer GetValues ESMF Component/CAM GetDataValues SWAT/OpenMI ESMF Export State CAM/OpenMI Wrapper Input Exchange Item ESMF Import State Output Exchange Item Import Input Exchange Item SetInputData • In two-way coupling, each model pulls the data from the other model using the OpenMI GetValues method. Extrapolation is used on the first timestep to break the deadlock between the two model requests. • OpenMI Input and Output Exchanges items are again used to exchange and translate the data. Output Exchange Item GetValues

25. Model Configurations • SWAT • Hydrology science information provided by Jon Goodall of University of S. Carolina • Lake Fork Watershed (TX) • Watershed Area: 486.830 km2 • Model run: 2 years, 1977 – 1978 • Timestep = 1 day • Weather Stations: • wea62 (33.03 N, 95.92 W) • wea43 (33.25 N, 95.78 W) • CAM • Global Atmospheric Model • Model run: 1 day • Timestep: 1800 sec • Dynamical Core: finite volume • Horizontal Grid: 10x15 • Export data variables: • surface air temperature • precipitation • wind speed • relative humidity • solar radiation

26. Future Tasks • Continue development of two-way coupling • Abstract data exchange within the ESMF wrapper code to accommodate configuration of different variables for different model implementations • Explore coupling via web services provided by other frameworks and analysis and visualization tools • Extend SWAT configurations for larger domains, and examine coupling to other hydrological and impacts models