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Wayne M. Wendland

Abstract

A relationship is identified between the area of the North Atlantic with surface temperatures greater than 26.8°C and the frequency of tropical storms and hurricanes. The relationship is direct and near-exponential. When the mean monthly area with sea temperature of 26.8°C is less than about 8.5 × 106 km2, tropical storms and hurricanes do not occur.

Estimates of tropical storm frequency based on the above relationship are made for several episodes of the Holocene.

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Wayne M. Wendland

Abstract

Using 3 h wind data (1970–74) from nine first-order NWS stations in and around Illinois, monthly frequency histograms of wind speeds for each station, and for each half-day (0700–1800 and 1900–0600 LST) were constructed. The histogram class interval was 2 mph. To assess the wind power for electrical power generation, the mean speed for each class was adjusted from the speed at the anemometer height to 20 m by means of a logarithmic relationship.

The wind analysis showed that the maximum potential for wind-generated electricity in Illinois is found from Chicago to Springfield to north of St. Louis. Over 60% of all 3 h winds are ≥8 mph (3.6 m s−1) within that band, whereas values are <55% to the northwest and ∼40% to the southeast within Illinois. January–April are the months with the strongest winds. During winter, nighttime speeds are ∼75% of those during the day, whereas in summer they are ∼50%.

Annual wind-generated electric power was calculated for each site based on the published specifications for a commercially available 1.8 kW generator and the wind climatology. From 50 to 55% of a residential electrical demand could be produced by the wind within the maximum potential area of the state, whereas only 25–30% could be wind-generated in the area with the least potential.

Cost payback estimates are presented for each of the sites with various purchase and installation costs and assumed inflation rates.

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Wayne M. Wendland

The frequency and intensity of early winter (November) coldwaves were investigated for the north central United States. Twenty-two such storms occurred from 1901 to 1985, and were most frequent in the 1950s and early 1960s, and again from the mid 1970s to the present.

November coldwaves are most often the result of Colorado cyclones moving to the east northeast. On average, temperature declines of 22°C or more within 24 hours, falling to at least 0°C, impacted about 40 percent of the 12-state region. The storms were most often accompanied by strong winds, wind chill, heavy snow to the west, and thunderstorms to the east, i.e., the trappings of a severe winter storm. Many of these storms inflicted severe damage on land and on the Great Lakes, sometimes taking lives of those not anticipating such a severe “winter” storm in November.

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Wayne M. Wendland and Wayne Armstrong

Abstract

The replacement of liquid-in-glass (LIG) thermometers with electronic thermometers in the National Weather Service (NWS) cooperative (co-op) network and concern for homogeneous temporal temperature records prompted this comparison study between the two temperature sensors.

This study shows that the new National Weather Service maximum-minimum temperature sensors (MMTS) underestimate LIG maximum temperatures by as much as 0.6°C, but are virtually equal to LIG minimum temperatures. The magnitude of differences increases with increasing solar loading and decreased wind speeds, apparently due to better ventilation characteristics of the MMTS shelter compared to those of a cotton-region shelter.

Any comparison of MMTS records with the LIG record will therefore require wind and solar observations. Unfortunately, neither wind nor solar is measured at NWS co-op sites, requiring the use of data from the nearest observing station. Obviously, the time of change from LIG sensors to the MMTS is of paramount importance when evaluating long-term temperature change.

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Douglas M. A. Jones and Wayne M. Wendland

Abstract

Known sources of data from arrays of instantaneous precipitation intensity recorders in southern Germany, east-central Illinois, northeastern Illinois, central Florida, and Hilo, Hawaii are obtained. These data are analyzed for line averages of the percent frequency of occurrence of the exceedance of selected threshold precipitation intensities. The correlation coefficients of the precipitation intensity at sites at varying distances from a reference site are determined. The decay in correlation is found to be a function of climatic region and the type of precipitation: showery or continuous. Showery rains are found to be essentially uncorrelated about 12 km from the reference site while continuous rain exhibits no correlation beyond about 50 km.

Single-station intensity data collected at Urbana, Illinois; Paris, France; Inyanga, Zimbabwe; Bogor, Indonesia; Reading, United Kingdom; Island Beach, New Jersey; Miami, Florida; Franklin, North Carolina; and Majuro, Marshall Islands, are compared.

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Wayne M. Wendland and Neil S. Mcdonald

Abstract

Estimates of mean monthly surface streamlines for the Southern Hemisphere were prepared from gridded mean surface geostrophic winds, from ship and land-based observations collected over several decades. The streamlines were arbitrarily drawn 20° clockwise to the geostrophic direction over oceans, 35° over relatively flat land, and 65° over rough terrain. Except over southern Africa, these assumptions were supported by a comparison between geostrophic directions and those of nearby mean vector winds.

Four annual airstream sources were identified within the Southern Hemisphere: one each over the Indian, Pacific, and Atlantic Oceans, and a continental source over Antarctica. A fifth source region was identified over Australia during seven months centered on the Southern winter. Airstreams originating in the Northern Hemisphere penetrate into the Southern Hemisphere during summer, following the Intertropical Zone. During a mean year, 46% of the Southern Hemisphere experiences air originating from only one of four sources the Pacific Ocean being the greatest contributor (20%), followed by the Indian Ocean (12%), Atlantic Ocean (9%), and Antarctica (5%).

Model confluences were found in four areas 1) at about 65°S latitude, 2) a confluence from equatorial Africa southwest to the coast, continuing eastward into the Indian Ocean, 3) a north-south confluence parallel to the Andes and 4) an east-west confluence south of the Australian cost from April through October.

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Wayne M. Wendland and Reid A. Bryson

Abstract

Near-surface airstream source regions of the Northern Hemisphere have been identified using 16-year mean resultant winds from 3° latitude by 3° longitude grids. Tracing the airstreams back to their divergent centers reveals 19 different sources during various seasons of the year. Five of these sources(air originating over the North and South Pacific and Atlantic Oceans and air over Turkey) are resident in the Northern Hemisphere 12 months of the year. Another three (central Asian, Arctic and central East Asian air) exist for at least 11 months per year. The remaining 11 source regions are present from 1–9 months per year and their area of influence is much less than that of the 5 year-long sources.

In the mean, there are several favored locations for frontal zones, e.g., a north–south band in Mexico (dividing Atlantic from Pacific air), a north–south band in northern South America, and two northeast–southwest trending bands over the cast coasts of Asia and North America, representing the mean leading edges of continental airmasses.

Mean dew points demonstrate the character of the moisture discontinuity across several mean frontal boundaries. Gradients in moisture are apparent as one progresses from one airstream to another. These gradients are sharpest along confluences, coasts and mountain barriers, particularly when a confluence is near-coincident with a topographic boundary.

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Stanley A. Changnon, Wayne M. Wendland, and Joyce M. Changnon

A group of atmospheric scientists, members of two midwestern AMS chapters, were polled in 1982 and in 1992 about their perceptions of current climate trends and the climate-change issue. Most correctly assessed the recent trends in climate conditions, aware of the cooling-wet trend with considerable seasonal weather variability prior to 1982, and most were aware of the warming trend in 1992. In both 1983 and 1992, a large majority of the respondents believed that information being presented about the climate-change issue was generally confusing to them and to the lay public. Half of the respondents in 1992 believed that evidence that a change in climate will occur is convincing, whereas in 1982 only 20% believed that evidence was convincing. In response to the question about whether the enhanced greenhouse effect on climate had begun in 1992, half said yes and half said no.

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Pradnya S. Dharmadhikari, David M. Sharpe, and Wayne M. Wendland

Abstract

To examine whether crop climate modeling using data based on phonological stages is appropriate for identifying different climatic effects on corn yields, two phonological models and a model using monthly data are devised for portions of Illinois for the period 1951–80. Comparisons of thew models show that there are no significant differences among the three models for the area as a whole. However, geographical differences in the suitability of these models are observed. When only a limited number of variables are used, the phenological models perform better for a major part of the state compared to the model based on calendar month data. Therefore, a fourth model called the Parsimonious Model, using selected variables from one of the two phenological models, is presented. The variables used in the Parsimonious Model represent the major agroclimatic controls on corn. Parsimonious models for sample areas show that climate has different impacts on corn yield variability in northern versus southern Illinois. Yields in northern Illinois are found to be more sensitive to precipitation during early phenologic stages and in southern Illinois to temperatures during later phenologic stages.

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Stanley A. Changnon Jr., Wayne M. Wendland, and John L. Vogel

Abstract

Through a computer-based system, weather data from Illinois are collected daily, checked, and summarized into various climatic products within hours after collection. This system was controlled for two years to demonstrate system feasibility, determine user interest and product desires, and plan for statewide urge. This study focuses on usage of system products. The private sector (agribusiness news media, and private industry) was the most frequent and persistent user group, suggesting user-pay as a possible approach for funding such a system. State and federal agencies, farmers, and extension agents also use the system but primarily during weather stress periods. The characteristics of usage should help in the design and selection of products in other emerging state and regional systems for dissemination of climate data and information. The usage patterns also indicate how climate conditions impact various private and public sectors in a humid continental climate.

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