Calculating motion velocity

IRIS Focus nowcasting uses the TREC algorithm to determine the predicted velocity of fields in the motion vector field (MVF).

TREC algorithm

The TREC (tracking radar echoes by correlation) algorithm is an iterative search method based on a maximum cross-correlation criteria used to estimate motion in a vector grid between consecutive images.

Figure 1. Calculating TREC
t0
Current time
tt0+Ʈ
Nowcasting predicted time
  1. Calculate the cross-correlation coefficient corresponding to the data within this subgrid and to a time in the future (Ʈ), tt0+Ʈ.
  2. Compute a motion vector between these locations.
  3. Repeat for each grid point or a subset of grid points in the data field.

References

For more information on TREC calculations, see the publically available references. For example:

  • Chornoboy, E. S., A. M. Matlin, and J. P. Morgan, 1994: Automatic storm tracking for air traffic control Lincoln Labs. J., 7, 427–448.
  • Li, L. W., W. Schmid, and J. Joss, 1995: Nowcasting of motion and growth of precipitation with radar over a complex orography. J. Appl. Meteor., 34, 1286–1299.
  • Mecklenburg, S., J. Joss, and W. Schmid, 2000: Improving the nowcasting of precipitation in an Alpine region with an enhanced radar echo tracking algorithm. J. Hydrol., 239, 46–68.
  • Rinehart, R. E., and E. T. Garvey, 1978: Three-dimensional storm motion detection by conventional weather radar. Nature, 273, 287–289.
  • Rinehart, R. E., 1981: A pattern-recognition technique for use with conventional weather radar to determine internal storm motions. Atmos. Technol., 13, 119–134.
  • Tuttle, J. D., and G. B. Foote, 1990: Determination of the boundary layer airflow from a single Doppler radar. J. Atmos. Oceanic Technol., 7, 218–232.
  • Wolfson, M. M., B. E. Forman, R. G. Hallowell and M. P. Moore, 1999: The growth and decay storm tracker. Preprints, Eighth Conf. on Aviation, Range, and Aerospace Meteorology, Dallas, TX, Amer. Meteor. Soc., 58–62.