Collabora've Development Ricardo Todling NASA GMAO 2013 Joint DTC- EMC- JCSDA GSI Workshop 1
In the Beginning NCEP: SSI (late 1980 s) Spectral formula'on of background error cov Direct assimila'on of radiances DAO: PSAS (early 1990 s) Physical- space formula'on of background error cov Assimila'on of temperature retrievals (actually, geopoten'al height retrievals) NCEP: GSI (early 2000 s) GMAO: Abandoned PSAS (c. 2003), joined GSI dev 2
Non- intrusive collabora'on From the ini'al stages in the collabora'on we were faced with having to accommodate differences without being disrup've to each other s development. NCEP s global model: spectral GMAO s global model: grid- point + ESMF- based GMAO adopted the concept of non- intrusiveness: We did not want NCEP to have to carry components it did not use (neither did NCEP want to carry stuff it didn t need!) GMAO interfaced GSI with its GEOS- AGCM without ever having NCEP to compile a single code related to establishing that interface. For a while GSI carried a file single that provided the GMAO hook. We have since evolved to having absolutely NO visible GMAO- specific code at NCEP. This is how we advocate anyone to hook- up to GSI. 3
A Unified Analysis System In the mid- 90 s NCEP supported (as it s'll does) a mul'tude of applica'ons from global to various regional components. Global and Regional analyses were detached. The GSI grid- space formula'on of B allowed for unifica'on of the various regional analyses. Since all development for hooking up various regional applica'ons took place at NCEP, all happened inside the GSI code. Our view today prefers that these hooks be handled as couplers, and thus not be in GSI. 4
Non- intrusiveness vs contribu'on Non- intrusiveness should not be taken as need to hide development of general features and contribu'ons. If a feature is general, we want to see it made available to all users of GSI, regardless of their applica'on. Non- intrusiveness simply means that project- specific knobs should be avoided as much as possible. Example: 4DVAR Ø code should have general interface to allow users to hook- up their own TL and AD models. Example: Hybrid Ø code should have general interface to allow users to provide members at will (more on this later). 5
Diversity and Flexibility Suppor'ng mul'ple model interfaces GSI provides hooks to a mul'tude of models, but It should provide a single interface to the background and placing support to mul'ple models in external libraries Suppor'ng mul'ple observing systems GSI is rather flexible in this respect, but needs Acceptance of modern observa'on format (NetCDF) Avoidance of wired- in user- specific QC and obs choices Suppor'ng mul'ple assimila'on strategies The flexibility for this is in place, but needs Agen'on when it comes to choices of control vector 6
Rela'vely Flat GSI (to most) gsi.x GSI GFS NMMB RTMA WRF bufr crtm I/O sp w3 math system Presently, a single executable handles mul'ple background choices. May seem flexible but it s rather cumbersome for maintenance: GSI shouldn t need to change because changes had been made to how the background is read in. 7
GSI Split into Mul'ple Libraries GSI_Appl GSI_Coupler GSI_Solver User_Suff GFS_gsi.x NMMB_gsi.x RTMA_gsi.x WRF_gsi.x GEOS_gsi.x GSI_U'l GSI Core GSI_Obsvr bufr crtm I/O sp w3 ESMF/ WRF math system To a large extent the split displayed above already exists at GMAO. This split gives greater flexibility and reduces burden to maintain GSI CORE components. 8
GSI Split: Added Flexibility AGCM_Appl GSI_Coupler AGCM GEOSgcm.x This selng already Allows GMAO to Hook- up its AGCM with the GSI observer. GSI_U'l GSI_Obsvr bufr crtm I/O sp w3 ESMF/ WRF math system It already possible to build a real observer capable of calcula'ng observa'on residuals by having the GSI- observer called from within the atmospheric model. If desired, it is possible to have a single executable run perform both the model integra'on and GSI analysis. 9
Enhancing Flexibility Improved model/background interface The library split will amount to having a single entry point handling the background in the Core GSI; This will allow for flexible choice of background fields; for example, permilng GSI to be used to assimilate chemical cons'tuents without need of meteorological fields; Ensemble hybrid and 4dvar fields should become equally flexible; In the future, the GRID the analysis operates on should be made flexible and be defined at entry point (beyond simply regular). Improved observa'on handling There is need for generaliza'on of the observa'ons operators, to handle user- GRID; interpola'on to intermediate grid can be avoided Residual output should be made more flexible (NetCDF- based) Improved code robustness Improved consistency checks and op'ons handling Improved memory management Ques4on some have asked: Should GSI apply the ESMF- paradigm? 10
NOAA/EMC Partners & The GSI Commigee Members of CommiBee NASA GMAO NOAA ERSL/GSD NCAR/DTC NOAA OAR NOAA ESSL/MMM AFWA JCSDA CommiBee DuDes Manage dev/implementa'on Forum for discussion Meets twice a year Ac've year- round to eval mods Review each modifica'on Enforce code standards Evaluate large proposed mods Users not represented are encouraged to contributed via DTC 11
The GSI Commigee A Commigee made up of the current principal contributors to GSI has been created to manage development and implementa'on. The Commigee s primary responsibility is to serve as a forum for discussion of present and future development, coordina'ng mul'ple interests and avoiding redundant efforts. The Commigee meets at least twice a year. The Commigee is ac've year- round, evalua'ng & approving changes. Each change must be presented (submiged) to the Commigee and be approved before being officially accepted. Desire to make large changes to the code must be submiged to the Commigee in the form of a proposal for change. A prototype of the idea might help the Commigee come up with a decision. Those users not represented in the Commigee are s'll encouraged to submit proposal and changes to the Commigee, using the DTC connec'on. The Commigee tries to enforce the agreed- upon code standards, so remember those before submilng your changes. 12
Contribu'ng via DTC From Huang et al. (2011) Though some of us in the community have access to NCEP s repository, the reality is that many don t and should have no need to. The DTC maintains an up- to- date copy of GSI for public consump'on. The DTC has the capability to test user- specific changes to verify code integrity. The DTC has the mechanisms in place to allow, not only O2R, but also R2O transi'on. 13
A biased example: main GMAO contribu'ons GSI Infrastructure: GSI_Bundle: generaliza'on of control vector Stub- framework to allow for user- plug- ins In works New Observa'on Types: MOPITT CO SSMI/S (joint w/ NCEP) MLS temperature retrievals MLS moisture retrievals MLS radiances Doppler Wind Lidar (now on hold) Methodologies: 4DVAR framework (in collabora'on with Yannick Tremolet from ECMWF) GSI Adjoint (in collabora'on with Yannick Tremolet from ECMWF) Various minimiza'on op'ons, including Lanczos and BiCG procedures (GOCART) Aerosol influence on (IR) radiance assimila'on Capability to apply GSI adjoint for B- precond (via bicg single loop only) Capability to use sqrt(b)- precond within hybrid framework (joint w/ NCEP) Assimila'on of cloudy IR radiances Aircrat bias correc'on (joint w/ NCEP) 14
A Truly Global Analysis System Though GSI has literally been explored by people everywhere in the world, it has been largely a one- way road. Those par'cipa'ng in this Tutorial & Workshop should Keep in mind the great opportunity to contribute, via the DTC to a truly global and open analysis system. From hgp://www.dtcenter.org/com- GSI/users/overview/index.php 15
Closing Remarks GSI is truly the only publically available, free- of- charge, mature analysis system in the world. Collabora've work in GSI has proven rather successful. There are challenges: code serves research as well as opera'ons; keeping up with fast changing code is hard; the lager is required for new changes to be accepted; code might not meet your standards and wishes: which should be a good reason to become involved! It is exci'ng to be able to contribute to the U.S. Na'onal Data Assimila'on effort. Thanks are due to NOAA/NCEP/EMC for this. 16