Global Climatological Analysis Toolkit

BACKGROUND 

Figure 1 Typical days based on SOM classifications for downscaled historical flow during May over Socorro, NM.
Figure 1 Typical days based on SOM classifications for downscaled historical flow during May over Socorro, NM.

RAL scientists continue to support the DoD’s National Ground Intelligence Center (NGIC) in its mission of assessing the consequences of the transport and dispersion of accidental and intentional releases of hazardous materials into the atmosphere. This is done by providing the agency with access to the RAL-developed GCAT (Global Climate Analysis Toolkit) system. GCAT is a fully automated dynamical downscaling system that allows NGIC scientists to remotely generate a high-resolution 30-year climatography for any region on the Earth. GCAT is based upon Climate Four-Dimensional Data Assimilation (CFDDA) technologies and can run with four domains, reaching a grid increment of 1.1-km. This enables NGIC to conduct transport and dispersion analyses at very fine scale.  GCAT has the capability to automatically classify WRF output fields into climatological regimes. The method is based on the Self Organizing Map (SOM) [1] artificial neural network pattern recognition technique. Figure 1 shows the results of a SOM classification, in which 30 months (May 1981-2010) of WRF 1.1km hourly outputs were used to estimate the main six regimes of the wind flow over the Energetic Materials Research and Testing Center in Socorro, NM. The six regimes that have been identified are given with their frequency of occurrence and their most representative days, which are chosen based on their Euclidian distance to each SOM node. Weather data valid for the representative days provides better forcing to NGIC’s transport and dispersion climatological studies, as they didn’t undergo averaging which can destroy important model physical properties (balance etc.) available with dynamical downscaling.

The Second-order Closure Integrated PUFF (SCIPUFF) transport and dispersion model is implemented for execution for each dynamical downscaling simulation upon user request. This way, SOMs can be built based on plume dosage, in addition to weather variables, when analyzing the past climate. The system makes use of the Climate Forecast System Reanalysis (CFSR) data set available on a 0.5-degree grid for initial and lateral boundary conditions.

FY2018 ACCOMPLISHMENTS

  • A new version of GCAT has been installed on DoD HPC facilities. This new version includes full operational capabilities for climo (reanalysis), Self Organizing Map (SOM), forecast, and “case study” jobs. The “case study” capability generates WRF model output, available for the download, for any events that occurred between Jan. 1, 1981 and yesterday, including a “last week event”. GCAT automatically uses real-time forecasts from the NCEP Global Forecasting System (GFS) to initialize WRF runs when a “case study” job is selected. Additional features include utilities for job status monitoring and data migration utilities. A key characteristic of the HPC port is that there will be no graphical user interface in the HPC port. All capabilities are executed through command line scripts, with the goal of simplifying long term software maintenance.
  • Multiple emission sources capability. On the new version of GCAT installed on HPC facilities, “Climo” and “Test case” jobs can run with multiple emission sources located in different locations of the domain with the same material. The ability to run SCIPUFF with multiple release points and the different materials in different locations has been added.

FY2019 PLANS

  • Ensemble intra-seasonal forecasting capability will be included in the new version running on HPC. This capability includes downloadingClimate Forecast System (CFS) every day for the 6 months ahead period which can be used as initial and boundary conditions for WRF high-resolution simulations. The user can select any period between today and 6 months ahead to perform WRF simulations to downscale CFS forecasts in any part of the world.
  • Testing a novel fast downscaling technique. NCAR will investigate the possibility of performing downscaling climatological analysis at a high resolution (~0.51 km) using a limited amount of computational resources. High resolution WRF simulations (~0.51 km) will be performed only for a period shorter than 30 years (12 year) while lower resolution simulations of the parent grid (~3 km) will cover the whole 30-year period. High resolution simulations will be extended to the 30-year period searching for matching analogs on the parent lower resolution grid. For this purpose, a combination of SOM and analog techniques will be used.

REFERENCES

[1]  Kohonen T (1995) Self-organizing maps. Springer-Verlag, Heidelberg

[2] Jun Yan (2010). som: Self-Organizing Map. R package version 0.3-5. http://CRAN.R-project.org/package=som

[3] Alessandrini S, Hacker J, Vandenberghe F Definition of typical-day dispersion patterns as a consequence of a hazardous release, Proceedings of 34th International Technical Meeting on Air Pollution Modelling, Montpellier, France, May 2015.\

[4] Ferrero, E., Vandenberghe, F., Alessandrini, S. and Mortarini, L., 2016, December. Comparison of WRF PBL Models in Low-Wind Speed Conditions Against Measured Data. In International Technical Meeting on Air Pollution Modelling and its Application (pp. 129-134). Springer, Cham.