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Walter A. Lyons

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Walter A. Lyons

Abstract

NASA's Earth Resources Technology Satellite (ERTS) now provides extremely high resolution (50–200 m) multi-spectral images of any given portion of the earth (between 81° north and south latitude) every 18 days. These are the best unmanned satellite data to date for the detailed study of mesoscale cloud patterns. An ERTS view of the southern basin of Lake Michigan at 1000 CST, 24 November 1972 reveals what certainly appears to be an example of inadvertent weather modification. Cold southwesterly air flow is producing the usual cumulus cloud activity over the relatively warm lake. What is unusual, however, is that the easily visible smoke plumes from a number of major industrial complexes in the Chicago-Gary, Ind., area appear to be markedly affecting the cumulus patterns. Cloud streets developing over Lake Michigan are observed to undergo enhancement when aligned with the industrial plumes. Specifically, the cumulus elements of the cloud streets become larger and brighter (and presumably thicker) than those forming in “unpolluted” air.

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Walter A. Lyons

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As part of an extensive mesoscale study of the Chicago lake breeze, ten summer months of data (1966–68) were used to compile a climatology of this phenomena and devise a simple forecasting technique. The lake breeze was found to occur at the Chicago shoreline on 36% of all days (out of a sample of 307). The time of onset ranged from before 0600 to 1&30 LST, with 0800–0900 LST being most frequent. The lake breeze front, defined as a narrow (1–2 km) band of convergence separating airflows with overland and overwater trajectories, was found to push inland anywhere from 1 block to over 40 km.

Experience verified that light gradient winds, strong insolation, and land air temperatures warmer than the lake water surface were the favorable conditions for formation. However, in an attempt to arrive at more objective forecasting scheme, the work of Biggs and Graves was extended to Lake Michigan.

A dimensionless number,
V2gCpT
is defined where V g, is the geostrophic wind speed from the 1200 GMT surface chart, C p the specific heat of dry air, and ΔT the difference (°C) between the maximum air temperatures at an inland location and the mean water temperature of the southern basin of the lake. Used as a hindcasting technique, it was found that a critical value of 10.0 emerged, above which a lake breeze would not be expected to occur at the shoreline. A hindcast accuracy between 90 and 95% was obtained by applying several additional criteria regarding the amount of cloudiness and the direction of the gradient flow with respect to the shoreline.
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Walter A. Lyons

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Walter A. Lyons
and
Cecil S. Keen

Abstract

Cloud-to-ground (CG) lightning observations from land-based lightning detection networks now allow monitoring this component of the electrical structure of tropical storms and hurricanes within a few hundred kilometers of the United States coastline. Several case studies confirm the long-held opinion that lightning is rather common within the outer rainbands. The general absence of CG lightning within the interior of mature tropical cyclones is also apparent. On the other hand, bursts of CG lightning near the circulation center of developing storms appear to precede periods of further deepening. The CG events are associated with convective supercells, whose anvil canopies can often obscure much of the underlying storm. Near-eyewall CG bursts preceding periods of intensification were noted in Hurricanes Diana (1984) and Florence (1988). A detailed case study of the 1987 unnamed tropical storm that struck the Texas-Louisiana coastline reveals that lightning was associated with two large supercells. These supercells appeared to be the trigger for the development of a closed circulation that formed several hours after the apparent low pressure center made landfall. Further studies of lightning may provide additional insight into the role of convective supercells in tropical storm intensification. It may also provide a useful diagnostic of impending deepening.

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Walter A. Lyons
and
Rudolph B. Husar

Abstract

An SMS/GOES 1 n mi visible image taken an 30 June 1975 reveals a massive area of atmospheric turbidity over the central and eastern United States. This was during the midpoint of a two-week air stagnation episode engulfing the Plains to the East Coast. It is shown that image “haziness” is correlated to midday surface visibility reports, which are in turn possibly correlated to sulfate aerosol concentrations. It appears that geosynchronous satellite data can play a major role in determining the areal extent of sulfate aerosol episodes.

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Walter A. Lyons
and
Henry S. Cole

Abstract

Limited ozone monitoring in the Milwaukee area by the Environmental Protection Agency in 1971 revealed surprisingly high values (19 pphm, maximum hourly average) and frequent exceedences of the 8 pphm federal standard. Since 1973 routine monitoring in southeastern Wisconsin has recorded hourly averages as high as 30 pphm, with frequent excursions beyond standard and episode alert dosage. In addition, high ozone readings at rural sites throughout Wisconsin have been noted.

These data are discussed with respect to changing concepts of the photochemical oxidant phenomenon. The Wisconsin data appear consistent with the view that long-range (≳200 km) transport of oxidants (and/or their precursors) is more the rule than the exception. It appears that entire anticyclones can become polluted, with widespread ozone levels approaching 8 pphm on the western side of the system. More importantly, along the western shore of Lake Michigan, adding to this general pattern, are lake-induced mesoscale wind systems which apparently result in large amounts of ozone (or precursors) being transported from the Chicago metropolitan area into southeastern Wisconsin. On a smaller scale, a pattern of high oxidant levels paralleling the lake shore from 1 to about 8 km inland is explained in terms of fumigation of oxidants stored aloft with the upper portion of a lake breeze or other onshore flows.

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Cecil S. Keen
and
Walter A. Lyons

Abstract

A classic lake breeze circulation cell that formed on the western shore of Lake Michigan on 4 September 1974 is studied in great detail. Wind measurements are made with surface anemometers and serial pibals, with air trajectories monitored via tetroons. Aircraft measurements map the thermal internal boundary layer and small and large aerosol distributions. Recirculation of pollutants is indicated from analysis of the tetroon data. Aerosol measurements suggest size sorting of small versus large particles as they are transported through the complex three-dimensional flow. These wind data also form the basis of a kinematic diagnostic study of mesoscale pollution transport in coastal areas, to be reported in a subsequent paper.

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Walter A. Lyons
and
Henry S. Cole

Abstract

Previous studies have shown that the lake breeze circulation cell which develops along the western shore of Lake Michigan during almost half of the warm season days has detrimental effects upon the air quality of the Gray-Chicago-Milwaukee area. However, stable onshore flow associated with a synoptic-scale pressure gradient occurs for an additional 15% of warm season days. This study examines the dispersion patterns during gradient, onshore flow. Fumigation and plume trapping, in particular, appear to cause serious degradation of air quality. Continuous fumigation of elevated plumes develops on days with strong insulation. Plume trapping occurs when a plume is emitted into a shallow layer of unstable air capped by a deep lid of stable air. This condition is frequent on overcast spring days.

Two days characterized by easterly gradient winds were studied: 27 May 1970, overcast; 25 June 1970, predominately sunny. The studies utilized meteorological data obtained from ground observers, ship's records, a wiresonde, and from aircraft photography.

A computer diffusion model incorporating the mesoscale meteorological characteristics for each day predicted ground level concentrations from several sources including a large coat burning power plant. The model for the fumigating power plant plume (25 June) yielded estimates in excess of 1.0 ppm SO2 7 km downwind of the plant.

Limited air monitoring data appear to confirm the diffusion model estimates and observations of plume behavior.

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Walter A. Lyons
and
Steven R. Pease

The Earth Resources Technology Satellite (ERTS-1) launched by NASA in July 1972 has been providing thousands of high resolution multi-spectral images of great interest to geographers, cartographers, hydrologists, agriculturists, etc. The meteorological content of these observations, however, has only been slightly realized. In particular, it has been found possible to detect the long-range (over 50-km) transport of suspected particulate plumes from the Chicago-Gary steel mill complex over Lake Michigan. The observed plumes are readily related to known steel mills, a cement plant, refineries, and fossil- fuel power plants. This has important ramifications when discussing the inter-regional transport of atmospheric pollutants, in this case from the Chicago Interstate to the Southeast Wisconsin Air Quality Control Region. Analysis reveals that the Multispectral Scanner Band 5 (0.6–0.7 μm) provides the best overall contrast between the smoke and the underlying water surface.

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