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David Suchman

A prototype of NOAA's proposed Green Thumb agricultural information dissemination system was demonstrated at five different sites across Wisconsin during the period July–October 1979. Those viewing the system were asked to complete questionnaires on their reactions to what they saw. Over 90% of those responding would use the system if it were available, and most were willing to pay between $100 and $150 to purchase the box.

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David Suchman and David W. Martin

Abstract

In this study we explore the accuracy, representativeness and reproducibility of tracer winds in the area of the 1974 GARP Atlantic Tropical Experiment (GATE). These winds were generated by tracking clouds in Synchronous Meteorological Satellite (SMS) images displayed on the University of Wisconsin's Man-Computer Interactive Data Access System (McIDAS). Two questions are addressed: 1) How accurately can the cloud displacements be measured? and 2) To what extent do the cloud displacements represent the wind field?

Accuracy is evaluated in terms of data characteristics, McIDAS precision and consistency. We find that for full-resolution visible data neither navigation nor resolution errors significantly affect the tracking of clouds. An examination of consistency, defined as similarity of wind sets independently produced by several scientists tracking clouds from the same set of images, yields an rms reproducibility of 2 m s−1 for cirrus level and 1.3 m s−1 for cumulus level winds. This is smaller than the “random” error generally attributed to cloud winds. In addition, the vorticity and divergence fields are qualitatively reproducible.

The discussion of representativeness centers about cloud height determination, and relating cloud motion to winds. Representativeness is examined through 1) the internal consistency of consecutive sets; 2) the consistency of the cloud wind field, including divergence and vorticity with such features as clusters, vortices, and clear areas; and 3) the difference between proximate satellite and ship winds. These differences were all under 3 m s−1, which is close to the noise level of ship winds and better than radiosonde-radiosonde comparison. We conclude that the representativeness of cloud tracers to cumulus and cirrus level flow is good to within the accuracy of currently available ground truth data.

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Gregory L. Johnson and David Suchman

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In this study, the effect of variations in the time and space resolutions of satellite images on satellite-derived drift winds is examined.

Rapid-scan satellite data are used as a basis for computing cloud-tracked wind fields over the south central United States on three synoptically different days in 1978. Winds from 30, 15, 6 and 3 min intervals are produced, discussed and compared. The latter includes examination of flow patterns, comparisons of mean and standard deviation values for speed and direction, and a discussion of operator observations. Low-level clouds are tracked on three separate days, the cirrus level is tracked on two separate days.

Nearly 10 times as many low cloud winds were computed on days of rapid cloud growth and dissipation using a 3 min interval rather than the conventional 30 min interval; spatial coverage of vectors was also significantly greater. The difference in the number of cloud winds was less pronounced on days with longer cloud lifetimes. Cirrus clouds, with lifetimes much greater than those of low-level cumuli, could be tracked more easily with a 30 min interval which also produced a smoother wind field. Whether tracking cumulus or cirrus, viewing a 30 min interval sequence, as well as examining the synoptics to get a “feel” for the situation, always proved valuable before any tracking was performed. Short-interval sequences caught the mesoscale features which the longer intervals missed and consequently the resulting wind fields often differed. Much more operator time was needed for tracking on the rapid scan images, however.

It is recommended that the conventional 30 min interval with single-pixel tracking methods be used on cirrus clouds, while a shorter interval (6–10 min) be used on low-level clouds.

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David W. Martin, Brian Auvine, and David Suchman

Abstract

An evolutionary view is sought Of a single cloud cluster. This cluster was chosen less for intensity than for comprehensive observations. The aim is to describe the principal outside controls on the cluster, including its relationship with nearby clusters. This is accomplished by combining observations from satellites with those from ships and aircraft.

The cluster represented the deepest of four overlapping layers of moist convection present on this day. It—and its neighbors—tended to occur along rings of cumulus clouds, somewhat larger in size, which were formed by the collapse of older clusters. There was no evidence of a migratory cyclonic synoptic disturbance in the lower troposphere. On the contrary, the cluster occurred entirely within southwest monsoon flow. Abruptly, early in the afternoon, as its cumulonimbus towers became aligned across the front face, the cluster accelerated and intensified. It is argued that this change toward squall line structure and behavior was due to strengthening vertical shear in the upper troposphere, which, together with a layer of dry northeasterlies near 600 mb, increased the strength of evaporationally forced downdrafts under the cirrus shield. The change, a kind of metamorphosis, points to more variability in tropical cloud clusters than has commonly been recognized.

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David Suchman, Brian Auvine, and Barry Hinton

To examine whether the addition of satellite data to forecasting procedures helps forecasters make better forecasts, we studied a meteorological consulting firm and its clients before and after satellite data were used in the preparation of weather forecasts, and whether the clients benefited from this new data source. We found that the satellite data were most valuable when they could be looped to show evolving cloud patterns and enhanced to show brightness differences. The satellite data would have been even more useful if the dissemination system were more flexible and the images were not pregridded.

Our main conclusions are:

  1. Satellite data are most useful to forecasters in data-poor areas and also help to fine-tune forecasts in data-rich areas. Because even slight improvements in forecast accuracy can result in sizable savings for clients, the use of satellite data can produce a significant economic benefit.
  2. Working with satellite data is a valuable educational experience for forecasters and undoubtedly improves their forecasting skills.
  3. Any future satellite data delivery system should take into account the needs and facilities of the user community.

Finally, we have shown that it is possible, using real data in actual situations, to help determine some of the economic effects of a new tool and the ways it can be used to bring about greater public benefits.

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David D. Houghton, John E. Kutzbach, Michael McClintock, and David Suchman

Abstract

Sea temperature anomalies which departed from the December climatic mean by approximately 2C off the coast of Newfoundland were inserted into the NCAR six-layer, 5° mesh, general circulation model of the atmosphere in order to test the model's response to small perturbations in sea surface temperature. The response of the model to the anomalies was analyzed with respect to pressure patterns, heat flux, and cyclone frequency, path and intensity. This response was compared with a statistical analysis of the response of the atmosphere to similar sea temperature anomalies based on approximately 80 years of observations as described by Ratcliffe and Murray.

Analyses of the anomaly experiments are preceded by an analysis of the basic (control) statistics for both model and atmosphere. The most pronounced discrepancies between the two were noted in cyclone statistics. A calculation with double horizontal resolution greatly improved the model features. Detailed comparison was complicated by the fact that the model failed to achieve statistical stationarity.

The extensive verification data of Ratcliffe and Murray proved valuable in distinguishing meaningful anomaly responses from those that could be attributed to the many limitations in the model, including a pronounced natural variability. Both warm and cold anomaly cases were tested. Best agreement with observed data was obtained for the case of the warm anomaly; this agreement was most evident during the middle portions of the integrations and then only in the North Atlantic sector. The response in the case with a cold anomaly was not as satisfactory although there were clear distinctions between the warm and cold anomaly cases.

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David Suchman, David W. Martin, and Dhirendra N. Sikdar

Abstract

A technique is described for inferring vertical mass circulations within and around cloud clusters in the tropics. Following Sikdar and Suomi (1972), we model deep convection in terms of three layers—two active and one passive. An inflow layer extends from the sea surface to the top of the trade inversion; an outflow layer extends through the depth of the cumulonimbus anvil. High-density satellite cloud tracer winds define flow for the two active layers. (The intermediate layer is not observed; in that sense it is considered to be passive.) Using the divergence field computed from the satellite winds, vertical velocities are calculated through the top of the inflow layer, and the bottom of the outflow layer; vertical mass transports follow immediately.

This simple model is applied to two mature disturbances from the Global Atmospheric, Research Program Atlantic Tropical Experiment (GATE). Vertical velocities and mass transports were estimated for three times, at 3 h intervals. Vertical velocities on the scale of the clusters averaged 2–18 cm s−1, with highest values in the outflow layer. For both GATE clusters, maximum ascent appeared to occur several hours earlier at low levels than at high levels. Vertical velocity was smaller on the larger cluster circulation scale, but still positive leading to rather large upward transport of mass outside the clusters. Cluster-scale mass transports ranged from 15 to almost 35 mb h−1. An exception was inflow level transport for the more mature of the GATE clusters, which became slightly negative, implying a large middle tropospheric transport of mass into the cluster. Centers of divergence and upward mass transport were well matched to convective activity in the satellite pictures, even reflecting changes in position and intensity.

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David Suchman, Brian A. Auvine, and Barry H. Hinton

The clients of a meteorological consulting firm were studied to determine the effects of weather forecasts on their operations. We determined what weather conditions triggered certain operational decisions in three groups of clients—governmental bodies, gas utilities, and electric utilities. Then, using actual forecasts over a 2-year period, we calculated the monetary losses incurred as a result of incorrect forecasts. The results generally show losses in the thousands of dollars for each erroneous forecast. Thus, if the weather service is able to prevent even one set of poor decisions based on a forecast, the cost of the service would be returned and in many cases greatly exceeded. Other effects of the clients' use of the forecast are discussed qualitatively. These include nonmonetary gains to the clients and their customers through increased convenience, easier planning, and fewer breakdowns in service. At least some clients fail to realize these advantages through inefficient use of the forecast.

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