Climatic Perspective Research Articles

The July 1995 Heat Wave in the Midwest: A Climatic Perspective and Critical Weather Factors

A brief but intense heat wave developed in the central and eastern United States in mid-July 1995, causing hundreds of fatalities. The most notable feature of this event was the development of very high dewpoint temperature (Td) over the southern Great Lakes region and the Upper Mississippi River Basin. At many locations, hourly values of Td set new records. The combination of high air and dewpoint temperatures resulted in daily average apparent temperatures exceeding 36°C over a large area on some days. A comparison with past heat waves shows that this was the most intense short-duration heat wave in at least the last 48 years at some locations in the southern Great Lakes region and Upper Mississippi River Basin. An analysis of historical data for Chicago, where the majority of fatalities occurred, indicates the intensity of this heat wave was exceeded only by a few periods in the 1910s and 1930s. Impacts in the Chicago urban center were exacerbated by an urban heat island that raised nocturnal temperatures by more than 2°C. An analysis of radiosonde data indicates that maximum daytime boundary layer mixing depths were only a few hundred meters in the core region of the heat wave. Simulations using a single-column version of a three-dimensional mesoscale model strongly suggest that this contributed to the very high values of Td since soil moisture in the central United States was near to above average and evapotransporation was likely high, causing a rapid moistening of the shallow boundary layer.

The emerging water crisis in Bulgaria

Climatic records for the last 15 years indicate that Bulgaria is experiencing a period of exceptionally low precipitation. During 1993, significant water supply problems emerged, approaching crisis proportions in Sofia, the nation's capital, by the end of 1994. The record-setting drought of 1993 can be explained from a synoptic climatic perspective. Whether consequences of the continuing drought could have been foreseen is arguable. That these consequences were fully realized only in 1994 may be understood through examination of Bulgarian water use since the end of the socialist era in 1989. If Bulgaria had experienced the same levels of industrial activity and irrigation as occurred in 1989, the current situation would have been national catastrophe, a situation that could quickly emerge in coming years should climatic patterns persist.

A Climatic Perspective on the 1993 Flooding Rains in the Upper Mississippi River Basin

ABSTRACT The major hydroclimatic cause of the 1993 Upper Mississippi River Basin flood was the persistence of heavy rains over a period of several months. As a result, precipitation totals for April-September 1993 were unprecedented, exceeding by a large margin any previous six-month precipitation total since 1895. Using standard hydrometeorological methods, the frequency of occurrence of these precipitation totals is expected to be less than once every 200 years. The core of the heavy rain area was located in Iowa and Missouri near the main stems of the Mississippi and Missouri Rivers. Thus, runof from many of the heavy rain events was deposited directly into these main stems. The persistence of the heavy rains maintained high soil moisture levels throughout the summer period. Thus, the heavy rains during the summer were accompanied by very high runoff rates. Also, the frequent rains were accompanied by many cloudy days. Primarily for this reason (and to a lesser extent because of lower temperatures), po...

Sodom, gomorrah and the other lost cities of the plain - a climatic perspective

Certain aspects of the biblical story of the Cities of the Plain have in recent years become widely accepted. Among them is the placing of those cities in the southern basin of the Dead Sea, the assumption that those cities are now covered by Dead Sea water and, in particular, the belief that their destruction was due to catastrophic geological causes, such as an earthquake. The Bible emphasizes the agricultural richness of the Jordan plain prior to the upheaval of Sodom and Gomorrah and its catastrophic transformation into a wasteland. Thus, stripped of ethical and religious overtones, the scenario is that of a rapid climatic change that converted a densely inhabited and richly watered area into an infertile salt playa. The region northeast and southeast of Jericho, which today is quite barren as a result of the upward movement of salty ground water but which contains some of the World's earliest known agricultural settlements, fits such a picture. Dating the Sodom event to approximately the 23rd-21st centuries B.C. supports the idea that a major climatic change that occurred between the Early and Middle Bronze Ages and which resulted in profound transformations in the Middle East such as the collapse of the Ancient Kingdom of Egypt, the invasion of the Fertile Crescent by the Semitic desert nomads, and the collapse of Early Bronze Age civilization in Palestine - is also responsible for the Sodom story. Although the data are far from complete, desiccation during this period is indicated by palynological evidence pointing to the decimation of forests in Northern Israel, paleobotanical evidence from Southern Israel, the deposition of salt layers in the Dead Sea, the abandonment of almost all settlements in the Negev Desert of Southern Israel, the Jordan valley and Southern Jordan, except those which were associated with perennial springs, and further afield the drastic lowering of the level of Lake Moeris in Lower Egypt. This scenario does not exclude the possibility that a major earthquake - which may have occurred during this period - was considered to be the cause of the final physical destruction of the Cities of the Plain, delivering a coup de grace to a collapsing society, and which became through the mists of time and legend, the only agent of destruction.

The lynx cycle: a climatic perspective

The lynx cycle: a climatic perspective

The Ecology of Aphis craccivora Koch and Subterranean Clover Stunt Virus in South-East Australia. III. A Regional Perspective of the Phenology and Migration of the Cowpea Aphid

Many workers have studied the migration of insects (see Johnson 1969), but few have attempted to place their observations into a regional and climatic perspective. In Australia, the cowpea aphid (Aphis craccivora Koch) is the most important vector of Subterranean Clover Stunt Virus (SCSV) to crop and pasture legumes. Its long-range migratory behaviour in Australia was first reported by Johnson (1957) who observed that large populations developed during the spring of certain years on medic (Medicago spp.) on the inland plains of north-central New South Wales (N.S.W.) and were blown eastward toward the coast on north-westerly winds. The reasons for the build-up of the cowpea aphid during certain years in that area are unknown. Hughes et al. (1964, 1965) and O'Loughlin (1963) conducted aphid trapping experiments over a wide area of southeast Australia, but derived few useful generalities. This paper examines the climatic limits for the development of cowpea aphid populations in south-east Australia, relating its migration and colonization to climate. Gutierrez, Morgan & Havenstein (1971) studied the ecology of the cowpea aphid in the temperate pasture regions of south-east Australia and found that aphid populations developed only in those areas where suitable conditions occurred for both the plant and the aphid. Pastures in this area are influenced by availability of moisture, while aphids do not survive during periods of ground-frost. By using a model of the aphid's population biology, Gutierrez et al. (1974) showed that the southern pasture areas were marginal for the aphid because the season was too short for the development of large populations. When, however, the attributes of a subtropical climate and host plant were incorporated into the model, the output suggested that the cowpea aphid could be an efficient migratory species. The results conformed to the hypotheses of Dingle (1972), who used static life-table parameters to demonstrate the biological attributes required by successful migrants.