Search Results

You are looking at 1 - 10 of 40 items for

  • Author or Editor: David D. Houghton x
  • All content x
Clear All Modify Search
David D. Houghton
Full access
David D. Houghton

Abstract

Calculations are made with the NCAR six-layer general circulation model to determine the time evolution of errors initially confined to a region 4000 km in diameter superimposed upon real global data. Three experiments are made to distinguish between the effects of an error located initially on the northern or southern sides of the jet stream or in the tropical area. Results show that the largest error centers generally evolve in the jet stream; however, the propagation rate is much less than advection effects would suggest. Coverage of the Northern Hemisphere is accomplished as much by propagation across the north pole and via the tropical belt as it is via the jet stream. It is not complete even after seven days. As a whole the tropics are more sensitive than the middle latitudes to initial errors. Cross-equatorial effects are most pronounced at and just east of the initial longitude of the error.

Full access
David D. Houghton
Full access
David D. Houghton
Full access
David D. Houghton
Full access
David D. Houghton

Abstract

An incompressible, stratified, hydrostatic, inviscid fluid model is used to demonstrate non-linear effects in the interaction of finite amplitude gravity waves. A statically stable density stratification is approximated by the superposition of ten homogeneous fluid layers with a very deep layer on top. Computations are made using a two-step Lax-Wendroff finite difference system. The solutions reveal intrawave distortions comparable to those predicted by analytical studies of one- and two-layer fluid models. During the interaction of two waves, the solutions show overall changes in wave speed which are of the same magnitude as the variations in wave speed that cause the intrawave distortions. These changes are related differently to the horizontal fluid velocities in the waves.

Full access
David D. Houghton

Abstract

A quasi-Lagrangian formulation for an inviscid barotropic fluid is presented and shown to afford a convenient basis for analysis of certain ageostrophic jet flows. Material fines serve as the references to delineate the north-south variations in the fluid, and Eulerian representation is used in the east west direction. Several desirable features are shown for the use of material lines in this manner. First, by orienting the lines approximately parallel to the jet axis, flows with finite horizontal curvature may be represented simply. This is illustrated by a development with east-west variations represented by only two harmonies and a mean. The solution of this semi-spectra model agrees closely with a non-spectral numerical solution for over three days. Second, the Lagrangian movement of the material lines gives an indication of non-linear adjustment motions and demonstrates a mixing in the fluid.

Full access
David D. Houghton

Abstract

No abstract available.

Full access
Richard D. Thomas Jr. and David D. Houghton

Abstract

This study examines the relationship between the radar echo parameters of area coverage and intensity, and the surface kinematic fields of divergence, divergence of moisture flux and relative vorticity. The study was limited to 11 cold frontal cases during the period March 1976–March 1977, and involved 99 echoes. Fine-resolution digitized radar data were used from two midwestern and one eastern United States sites. The data were analyzed on a computer-interactive video system. The area coverage did not correlate significantly with any of the surface parameters tested. However, the intensity parameters did show significant relationships with the surface parameters, the best being with relative vorticity. The correlations were higher when surface data from 1 h before the time of the echo were used, with coefficients as high as 0.5.

Full access
David D. Houghton and William S. Irvine Jr.

Abstract

The performance of the National Weather Service, Air Force and Navy large-scale numerical prediction models was studied for the case of a relatively small-scale but important weather-producing frontal system in the Midwest over the period 1200 GMT 5 October 1974 to 0000 GMT 7 October 1974. Forecasts were analyzed both for the operationally important parameters of precipitation, surface pressure and 500 mb heights and for such key diagnostic parameters as vertical motion and thermal and vorticity advection. Results showed the importance of resolving small synoptic-scale features in the initial conditions as well as the role of model resolution, basic dynamics formulation, and planetary boundary layer representation in the forecasts. There was a wide range of performance among the four models. The National Weather Service (NWS) Limited Fine Mesh Model clearly gave the best 24 h forecasts, compared to all the other models including the NWS Primitive Equation Model.

Full access