The objective of this project is to build a reliable trajectory analysis tool and a web-based user interface to be used by Texas Natural Resource Conservation Commission (TNRCC) and other researchers who participated in the Texas Air Quality Study (TexAQS) 2000. It is recognized that the trajectory analysis tool will be needed to help researchers from TNRCC, NOAA, DOE and universities to compare TexAQS2000 Field Study air quality measurements to emissions reported in the industry for the study period.

The base model of the trajectory analysis tool is the HYSPLIT_4 (HYbrid Single-Particle Lagrangian Integrated Trajectory version 4 (Draxler, 1999) of NOAA Air Resources Laboratory (ARL) with associated codes developed by University of Houston Air Quality Group ( Professor Daewon Byun and Dr. Seung-Bum Kim). Therefore, we name the tool as ARL/UH HYSPLIT trajectory model. For the input, gridded meteorological data on one of three conformal (Polar, Lambert, Mercator) map projections are required at a regular time interval. In addition, it supports computations of trajectories on a latitude-longitude grid. The input data are interpolated to an internal sub-grid to reduce memory requirement and to increase computational speed. Calculations for the backward and/or forward trajectories may be performed sequentially on multiple meteorological grids, usually specified from fine to coarse resolution.

NOAA The routine meteorological data fields required for the calculations may be obtained from existing archives or from forecast model outputs already formatted for input to the ARL/UH HYSPLIT trajectory model. The original HYSPLIT version 4 includes pre-processor programs to convert NOAA, NCAR (National Center for Atmospheric Research) re-analysis, ECMWF (European Centre for Medium-range Weather Forecasts), and NAVY COAMPS to a format compatible for direct input to the model. Recently, ARL has made available a preprocessor code for MM5 version 3 output. For this project, UH has implemented a code for CSU-RAMS (Colorado State University-Regional Atmospheric Modeling System) model output fields. The model's meteorological data set structure is in compressed and "direct-access" format. Each time period within the data file contains an index record that includes grid definitions to locate the spatial domain, check-sums for each record to ensure data integrity, variable identification, and level information. These data files require no conversion between computing platforms.

One of major features is that the model can be run interactively on the Web. The web-interface has been made and maintained by Dr. Seung-Bum Kim and Mr. Srivatsan Mani .

Trajectories

Meteorological Data

The meteorological input fields used by ARL/UH HYSPLIT trajectory model are required to be in "ARL packed" format. Thus, all meteorological data available should be converted this format before used in ARL/UH HYSPLIT trajectory model.