Search Results

You are looking at 1 - 6 of 6 items for :

  • Author or Editor: William E. Johns x
  • Journal of Applied Meteorology and Climatology x
  • Refine by Access: All Content x
Clear All Modify Search
John E. George
and
William M. Gray

Abstract

Ten years of rawinsonde data for 30 stations in the western North Pacific have been composited relative to tropical cyclone center positions. This information is used to study tropical cyclone motion and surrounding parameter relationships. Tropical cyclone motion and lower troposphere surrounding actual and geostrophic flow fields from 1°–7° radius are very well correlated. This general correlation of surrounding flow features applies equally well for cyclones with different directions of motion, speeds of propagation, intensities and intensity changes. The 700 mb level best specifies cyclone speed. The 500 mb level best specifies cyclone direction. The steering flow concept of cyclone motion appears to be quite valid in the statistical sense. These results may be useful to tropical cyclone forecasters.

Full access
John E. George
and
William M. Gray

Abstract

Ten years of rawinsonde data for 30 stations in the western North Pacific have been composited relative to tropical cyclone center positions. This is the same data set described in a previous paper by the same authors. These data were used to study prior (12–72 h) differences in surrounding environmental fields between tropical cyclones which recurved and those which did not. Differences in the wind, height and temperature fields out to 21° radius to the north between these two classes of storms are presented. A strong recurvature correlation is found in the 200 mb wind and height fields at large radii to the north. It is suggested that an operational long-range (2–3 days) tropical cyclone recurvature forecast scheme can be developed using upper tropospheric wind-height data.

Full access
William E. Clements
,
John A. Archuleta
, and
Donald E. Hoard

Abstract

Wind and temperature data collected by an instrumented tethered balloon and a Doppler lidar in a deep valley are used to investigate the mean properties of the nocturnal drainage flow down the valley on four nights when the wind at ridgetop had an up-valley component. We examine the vertical structure of temperature and the vertical and horizontal structure of the drainage wind. An empirical description of the wind field is derived and used to estimate the mass flux resulting from the drainage flow. Mean properties of the flow are presented and relationships among some of the parameters are examined.

Full access
William E. Clements
,
John A. Archuleta
, and
Paul H. Gudiksen

Abstract

During September and October of 1984 the Department of Energy's Atmospheric Studies in Complex Terrain program conducted an intensive field study in the Brush Creek Valley of western Colorado. The overall objective of the study was to enhance the understanding of pollutant transport and diffusion associated with valley flows. Data collections were designed to investigate nocturnal and morning transition wind, turbulence, and temperature fields in the valley, in its tributaries, and on its side-slopes, and how these are affected by the free stream conditions above the valley. The release and sampling of atmospheric tracers were used to study transport and diffusion. The experimental design of this study is presented.

Full access
William P. Kustas
,
John H. Prueger
, and
Lawrence E. Hipps

Abstract

A riparian corridor along the Rio Grande dominated by the Eurasian tamarisk or salt cedar (Tamarix spp.) is being studied to determine water and energy exchange rates using eddy covariance instrumentation mounted on a 12-m tower. The potential of using remotely sensed data to extrapolate these local estimates of the heat fluxes to large sections of the Rio Grande basin is under investigation. In particular, remotely sensed (radiometric) surface temperature can be used to estimate partitioning of net radiation energy into sensible and latent heat fluxes from vegetated landscapes. An important issue that has not been addressed adequately in the application of radiometric surface temperature data is the effect of using different time-averaged quantities in heat transfer formulations. This study evaluates the impact on sensible heat flux estimation of using relatively short time-averaged (1 min) canopy temperatures measured from a fixed-head infrared radiometer with 1-, 10-, and 30-min time-averaged micrometeorological input data used in estimating the resistance to heat transfer. The results indicate that, with short time-averaged radiometric surface temperatures (essentially “instantaneous” from a satellite), variations in sensible heat flux strongly correlate to fluctuations in net radiation conditions. Under near-constant net radiation input, natural perturbations in surface temperature also contribute to variations in sensible heat flux but are typically an order of magnitude smaller. The resulting implications for computed heat flux estimates using data from remotely sensing platforms and validation with flux tower measurements along riparian corridors are discussed.

Full access
Carl N. Hodges
,
T. Lewis Thompson
,
John E. Groh
, and
William D. Sellers

Abstract

The University of Arizona has developed a sea water desalinization system which can economically utilize low temperature solar energy. The system consists of a horizontal plastic-covered solar collector, a packed-tower evaporator, and a finned-tube surface condenser. Incoming sea water is preheated in the surface condenser and then pumped to the solar collector where it is heated 5 to 10C. The heated sea water is pumped from the collector to the packed-tower evaporator, where a small fraction is evaporated into a circulating air stream and condensed as distilled water in the finned-tube surface condenser.

To evaluate the system a pilot plant has been constructed in cooperation with the University of Sonora at Puerto Peñasco on the Gulf of California. This plant is designed to produce between 2500 and 5000 gallons of fresh water daily.

The energy for evaporation in the system is derived from ocean water heated in the solar collector during the day. In order to allow design optimization for the entire plant the temperatures in the collector must be accurately predicted. It is shown that this can be done by a simple manipulation of the energy balance equation for the collector.

The resulting theory is applied to a number of cases involving a double glazing collector filled with 2 inches of water. Such a collector will utilize about 24 per cent of the available solar energy if the warm water in the collector in the late afternoon is flushed out and stored for nighttime use in the evaporator.

Full access