Search Results

You are looking at 1 - 2 of 2 items for :

  • Author or Editor: David D. Houghton x
  • Journal of Applied Meteorology and Climatology x
  • Refine by Access: All Content x
Clear All Modify Search
Kenneth B. Mielke
and
David D. Houghton

Abstract

An extensive statistical study was made of the properties of radar echo systems in the upper Midwest region of the United States. Mesoscale groupings of echoes with distance scales 10–100 km and time scales 3–10 h instead of individual echoes were considered in the expectation that the former would be more relevant to deterministic short range prediction models.

A total of 203 case histories for 1974 was analyzed. Statistics for the area and duration were determined for the three categories of echo systems: those associated with warm fronts, with cold fronts and with neither. Correlations with the positions of the frontal zones and relationships with upper air winds were also made.

Consistent with earlier studies, it was found that the larger echo systems tend to last longer and that the direction of motion was usually somewhat to the right of upper level winds. Results provided many quantitative relationships that would be useful for prediction schemes and for developing models that carry mesoscale precipitation areas as explicit parameters.

Full access
David D. Houghton
,
David P. Baumhefner
, and
Warren M. Washington

Abstract

The problem of obtaining initial values for vertical motion and the divergent component of horizontal velocity is examined for a global primitive equation model. Only diagnostic methods are considered, the emphasis being on uniform application over the globe rather than a high degree of accuracy. Results show that a very simple diagnostic equation similar in form to the omega equation provides for realistic values of vertical motion in high and middle latitudes and smooth variations across tropical latitudes. In terms of prediction accuracy, no improvement is noted by using the computed initial vertical motions instead of zero for the initial vertical motions in a six-layer, 5° mesh model. In both cases unrealistic oscillations occur during the first 12 hr.

Full access