1. Introduction of PME real-time forecasting system
PME real-time four-dimensional data assimilation (FDDA) and forecasting system is a multi-scale, rapid-cycling mesoscale NWP (numerical weather prediction) model, which was originally developed to provide high-resolution weather analysis and short-term forecasts for the United States. In the past ten years, NCAR has applied and specialized this technology for use by 30+ national and international weather-critical applications. A highly successful example is a wind energy application recently developed for a major US utility company.
PME FDDA system is a mesoscale forecasting system based on WRF 3.3.1 and employs a time-continuous assimilation of a variety of synoptic and asynoptic observation data through observational nudging. The observation nudging uses relaxation terms based on the model error at observational stations, and the relaxation is such as to reduce this error. Each observation has a radius of influence, a time window, and a relaxation time scale determined by user-specified input. These determine where, when, and how much it affects the model solution. Typical model grid points need to be located within the radius of influence of several observations, and their contributions are weighted according to the distance from the observation(s). Before performing obs-nudging, an observation input file will be generated for each WRF domain. The observation file(s) contain chronological lists of the 3D positions and values of each observation, in a specific format.
2. Structure of the WRF real-time forecast system
2.1 Location of the model codes: the cycle_code directory
saudi-c3: /d1/pmefdda/builds/build_mm_nightly/wrfv3.3.1
The cycle_code directory contains all the model source codes.
2.2 Location of the executables: the datbin directory
saudi-c3: /home/pmeop/datbin
The datbin directory contains some of the utility files that download the GFS data, SST data and NCEP observation data.
2.3 Where to submit the job: the GMODJOBS directory
saudi-c3: /d1/pmefdda/GMODJOBS/GWPME/scripts/
All model jobs are placed under this directory using different job id names. For NCAR-PME real-time WRF runs, the job is named as GWPME. All model run control files can be found under this directory and this is also where all the model jobs are submitted.
The namelist files are located under:
saudi-c3: /d1/pmefdda/GMODJOBS/GWPME/namelists
2.4 Where the jobs are running and where to find the model data: the cycles directory
saudi-c3: /d2/pmefdda/cycles/
The cycles directories are the directories where the jobs are actually running and where the model data are stored. For the WRF real-time runs, the running directory is:
saudi-c3: /d2/pmefdda/cycles/GWPME/GRM
The scripts for doing post processing of the PME real-time forecasts are located under:
saudi-c3:/d1/pmefdda/builds/build_mm_nightly/wrfv3.3.1/cycle_code/POSTPROCS