Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: A. R. Rodi x
  • Refine by Access: All Content x
Clear All Modify Search
A. R. Rodi
and
P. A. Spyers-Duran

Abstract

Full access
N. Prasad
,
A. R. Rodi
, and
A. J. Heymsfiield

Abstract

The evolution of precipitation in seeded wintertime orographically induced convective and stratiform clouds with embedded convection were studied using in situ observations and particle growth and trajectory models. The particle growth model of Heymsfield embedded in a kinematic flow field representative of the Sierra barrier was used to study the ice particle growth by diffusion, accretion and subsequent fall trajectories. The particles observed by the aircraft were classified into habits. The growth of observed particles were compared with the model predicted evolution. Using the aggregation model of Heymsfield, the observation of formation of aggregates in <10 minutes was verified. The key findings of this study were.. (i) Aggregates (>1 mm) form in 4–8 minutes after seeding a convective cloud. (ii) Riming is important close to the barrier in a stratiform cloud when large cloud droplets and liquid water up to 0.3 g m−3 are present. (iii) Diffusional growth is extremely important for temperatures near −15°C in these low liquid water content clouds. The particles grow to ∼2 mm when released from just colder than −15°C, and to ∼1 mm when falling from warmer than −15°C.

Full access
Jean-Louis Brenguier
,
A. R. Rodi
,
G. Gordon
, and
P. Wechsler

Abstract

A method for detecting malfunctions during collection of data with the forward-scattering spectrometer probe (FSSP) is discussed. Droplet spectra measured with the probe are not sufficient to alert operators of probe failures, such as those caused by fogging or icing of the optics. Exact solutions of the coincidence process and application of these formulas, using additional parameters provided by the FSSP, yield estimates of the transit time of the droplets through the laser beam. Comparison of these estimates with expected values derived from aircraft speed can be used to detect a variety of FSSP malfunctions. An example of such an analysis using data from a flight through supercooled cloud is presented.

Full access
M. Segal
,
J. R. Garratt
,
R. A. Pielke
,
W. E. Schreiber
,
A. Rodi
,
G. Kallos
, and
J. Weaver

Abstract

The present study provides a preliminary evaluation of mesoscale circulations forced by surface gradients of heating arising from irrigated areas adjacent to dry land, utilizing a combination of satellite, observational, and modeling approaches. The irrigated crop areas of northeast Colorado were chosen for the study. For the cases studied satellite surface infrared temperature data indicated a typical temperature contrast of approximately 10 K at noon, between the irrigated area and the adjacent dry land. Surface observations and aircraft measurements within the lower region of the atmospheric boundary layer indicated, in general, a significant temperature contrast and moisture difference, thereby implying a potential thermally driven circulation. The anticipated thermally induced flows, however, were reflected in the measurements only by modest changes in the wind speed and wind direction across the contrast location. It is suggested that the daytime, elevated, terrain-forced flow in the area, and the synoptic flow, combined to mask to varying degrees the thermally induced circulation due to the irrigated land-dry land area effect. Numerical model simulations which were carried out over the studied area support this hypothesis. In addition, the impact of the irrigated areas on the moisture within the boundary layer, as well as on potential convective cloud developments is discussed.

Full access
James W. Wilson
,
James A. Moore
,
G. Brant Foote
,
Brooks Martner
,
Alfred R. Rodi
,
Taneil Uttal
, and
James M. Wilczak

The Convection Initiation and Downburst Experiment (CINDE) was conducted in the Denver, Colorado area from 22 June to 7 August 1987 to study processes leading to the formation of deep convection and the physics of downbursts. A total of 6 Doppler radars, 87 mesonet stations, 3 research aircraft, 8 sounding systems and numerous photographic facilities were deployed within an 85 km × 85 km area. A comprehensive data set was obtained including measurements of convergence lines, downbursts, and tornadoes that occurred on 35, 22, and 11 days, respectively.

This paper describes the objectives of the experiment and the specific facilities employed. Highlights and preliminary results are presented for several studies underway to show the type of data collected and to illustrate the sorts of analyses being pursued. Examples chosen include the topics of cloud initiation on stationary convergence lines, terrain-induced circulations, downbursts, tornadoes, and tracking chaff in precipitation-filled regions.

Full access