ASTRA - Atmospheric & Space Technology Research Associates, LLC

TIDDBIT Radar in Texas

Texas has been used as a test-bed for the development of the TIDDBIT radar. There have been no previous measurements of TIDs in Texas, and we are beginning to develop a climatology using our data. The system has a receiver in San Antonio and transmitters in Austin, Uvalde and St Hedwig (near Seguin) – see Figure 1.



Figure 1. The TIDDBIT System In Texas

Figure 2 shows a typical dataset from the Texas system, with well-correlated perturbations on each path. Using cross-spectral analysis and triangulation of the TIDDBIT signals, TID speeds and azimuths were obtained for each wave frequency, as shown in Figures 3a and 3b, respectively.

Figure 3 reveals a spectrum of waves with periods of 10 – 110 minutes, traveling at 200 – 400 m/s towards the southwest (-100 to -160deg E) TIDs with periods below the Brunt-Vaisala period (~7 minutes) are probably driven by acoustic waves, and their horizontal phase trace speeds are apparently much larger because they propagate vertically rather than horizontally. Because the HF Doppler system operated on two frequencies, we also were able to determine vertical phase trace speeds (not shown) in addition to the horizontal phase trace speeds.