The use of diagnostic and prognostic windfields for atmospheric transport calculations:an evaluation of the DIPOLE EAST 169 field experiment

Abstract

The United States Defense Threat Reduction Agency (DTRA) DIPOLE EAST 169 experiment took place at White Sands Missile Range (WSMR), New Mexico on 23 September 1999. The objective of the experiment was to validate the DTRA Hazard Prediction and Assessment Capability (HPAC) suite of models in a weakly forced, light wind environment. Specifically, DTRA diagnostic and prognostic models were used to produce wind fields that were passed to DTRA's transport model. The resultant transport calculations were compared with the ground truth data. A release of SF₆ was tracked by remote sensors to provide ground truth data. Test day weather conditions were gathered. Data from the WSMR Surface Automated Meteorological Site (SAMS) sites, a mobile profiling system, and from rawinsonde were collected and fed into the models.

A presentation of the general weather conditions that existed on the test day is first reviewed, followed by a discussion of the forecast profiles for the test site as well as a discussion of the weather condition that existed in the calculation domain as evidenced by the surface data. This provides the background conditions for the test such as the cloudy conditions that were experienced and the light winds throughout the domain. Included in this discussion is the presentation of the ground truth data collected by the Fourier Transfer Infrared Spectrometers (FTIRs) used to determine the location of the SF6 cloud centroid. The results of the transport model output based on input from the diagnostic and prognostic models are presented. Finally, the results of the actual SF6 cloud centroid are compared with the modelled results. The differences are discussed and potential causes for the differences considered. However, the overall model performance produced results that show that cloud tracking and calculations were within one grid unit of ground truth. Overall, the models produced reliable results for this limited study on a light wind case.