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David R. Smith

Abstract

The boundary conditions for Rotunno's numerical model which simulates tornado-like vortices are examined. In particular, the lateral boundary condition for tangential velocity and the upper boundary condition for radial and tangential velocities are considered to determine if they have any significant impact on vortex development.

The choice of the lateral boundary condition did not appear to have any real effect on the development of the vortex over the range of swirl ratios studied (0.87–2.61).

The upper boundary conditions attempt to simulate both the presence and absence of the flow-straightening baffle. The boundary condition corresponding to the baffle in place produced a distinct boundary layer in the u and v field and very strong upflow and downflow within the vortex core. When this condition is removed, there is both radial and tangential motion throughout the domain and a reduction of the vertical velocity. At small swirl ratio (S = 0.87) this boundary condition has a profound impact on the narrow vortex, producing changes in the pressure field that intensifies the vortex. At higher swirl ratio the vortex is apparently broad enough to better adjust to the changes of the upper boundary condition and, thus, experiences little change in the development of the vortex.

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David R. Smith and Joseph M. Moran

The Fifth International Conference on School and Popular Meteorological and Oceanographic Education was held 5–9 July 1999 in Ballarat and Melbourne, Australia. Conference delegates included 105 teacher educators, meteorologists, oceanographers, and science communicators representing 13 nations. Principal themes of the conference were weather and ocean studies in the primary and secondary school classroom (K–12), professional development programs for teachers in meteorology and oceanography, using the Internet for schools and public education, and communicating environmental issues to the public. Oral presentations, workshops, poster sessions, and hands-on demonstrations provided information on programs for teacher enhancement, computer-aided instruction, and access to real-time weather information.

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David R. Smith and John T. Snow
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G. Louis Smith and David R. Doelling

Abstract

The effects of the earth’s oblateness on computation of its radiation budget from satellite measurements are evaluated. For the Clouds and the Earth’s Radiant Energy System (CERES) data processing, geolocations of the measurements are computed in terms of the geodetic coordinate system. Using this system accounts for oblateness in the computed solar zenith angle and length of day. The geodetic and geocentric latitudes are equal at the equator and poles but differ by a maximum of 0.2° at 45° latitude. The area of each region and zone is affected by oblateness as compared to geocentric coordinates, decreasing from zero at the equator to 1.5% at the poles. The global area receiving solar radiation is calculated using the equatorial and polar axes. This area varies with solar declination by 0.0005. For radiation budget computations, the earth oblateness effects are shown to be small compared to error sources of measuring or modeling.

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Doyle Cook and David R. Smith

Forecasts issued to the public during the 10-year period 1966–75 by the National Weather Service Forecast Office, Louisville, Ky., are compared with guidance forecasts produced by the National Meteorological Center for the same location. There was little overall change in the quality of forecasts issued to the public, but the guidance forecasts have improved to the extent that they are now of a quality comparable to those issued to the Louisville public.

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Steven B. Newman and David R. Smith

The Third International Conference on School and Popular Meteorological and Oceanographic Education was held 14–18 July 1993 in Toronto, Ontario, Canada. This conference was attended by approximately 150 educators, meteorologists, oceanographers, and government officials representing 12 countries. The themes of this conference were the role of meteorology and oceanography in the formal science education of students in grades K-12 and the enhancement of scientific literacy of the public in order to permit individuals to make better use of products and services provided by the national environmental services and the media. Sixty formal presentations plus two poster sessions and six workshops provided information on educational programs as well as a variety of classroom activities on meteorological and oceanographic topics.

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David R. Smith and Fred W. Leslie

Abstract

The Purdue Regional Objective Analysis of the Mesoscale (PROAM) is a successive correction type scheme for the analysis of surface meteorological data. The scheme is subjected to a series of experiments to evaluate its performance under a variety of analysis conditions. The tests include use of a known analytic temperature distribution to quantify error bounds for the scheme. Similar experiments were conducted using actual atmospheric data. Results indicate that the multiple pass technique increases the accuracy of the analysis. Furthermore, the tests suggest appropriate values for the analysis parameters in resolving disturbances for the data set used in this investigation.

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David R. Smith and Ira W. Geer
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John E. Zimmerman, Phillip J. Smith, and David R. Smith

Abstract

A study of the sensitivity of a weak winter extratropical cyclone to latent heat release (LHR) is presented using 48-h simulations of the cyclone's evolution derived from three versions of the LFM model: a MOIST simulation in which full model physics was employed, a DRY simulation in which all latent heating was removed, and a DOUBLE MOIST simulation in which the effect of latent heating on the temperature field was doubled. Results indicate that a deepening cyclone occurs in the DOUBLE MOIST simulation, a near steady-state cyclone in the MOIST simulation, and a filling cyclone in the DRY simulation. Thus, for this case the presence and intensity of LHR is of critical importance to this cyclone's intensification. In addition, using height tendency diagnoses, it is concluded that for this case in the lower troposphere the dominant LHR influence is direct, through the explicit diabatic heating forcing in the height tendency equation. In contrast, in the middle and upper troposphere this direct LHR role is no longer dominant, but rather shares its importance with the indirect effect, represented by the influence of LHR on the dynamical forcing mechanisms.

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David R. Smith, Michelle E. Pumphry, and John T. Snow

Abstract

An error analysis of the Purdue Regional Objective Analysis of the Mesoscale (PROAM) scheme is described. PROAM is an interactive, multiple iteration objective analysis package for surface meteorological data. It utilizes a Gaussian weighting function similar to that of Barnes. A problem with applying interpolation routines to surface data is that the surface station network has a highly nonuniform spatial distribution. Smith and Leslie have shown that this nonuniformity can impact the accuracy of the analysis. The objective of this investigation is to determine quantitatively the contribution that this nonuniformity of station locations has on the analysis of data for two different distributions of stations.

Experiments were done by varying the values of important analysis parameters in order to generate error curves for each parameter. Analytic functional representations for pressure and temperature were used to generate input data free of observational error, as well as to produce exact analyses. With exact fields available, root-mean-square errors and average grid point errors were calculated for analyses using uniform, actual and edited station distributions.

Results show that the PROAM scheme performs a better interpolation of the observations when the stations are more uniformly distributed. Root-mean-square and average grid point errors for analyzed fields decrease as the uniformity of the station distribution increases. Furthermore, elimination of some data stations (when several are clustered within a small area) can result in an analysis with smaller errors than a field with more stations but a less uniform distribution. The error analysis performed in this study suggests methods which can minimize errors in the analyzed fields.

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