A SYNOPTIC CLIMATOLOGICAL ANALYSIS OF SUMMERTIME PRECIPITATION INTENSITY IN THE EASTERN UNITED STATES

The spatial patterns of precipitation frequency and intensity over the eastern United States for summer from 1961 to 1990 are analyzed using a recently developed continental-scale air mass-based synoptic classification. This procedure, the spatial synoptic classification (SSC), is based on “seed” day identification of synoptic events and discriminant analysis to group together days that are within the same air-mass type. Results show differences in the types of precipitation associated with different air masses. Two air masses in particular-Moist Tropical and Moist Temperate-appear to be highly correlated with a majority of the precipitation, particularly in the southeast. The synoptic characteristics, daily intensity of rainfall, and radiosonde soundings during prevalence of these two air masses suggest that convective rainfall is common during Moist Tropical, and stratiform-type rainfall occurs during Moist Temperate. A simple stratification scheme based upon a synoptic-based air-mass delineation may be useful for studies that need to divide days into stratiform or convective regimes.     

VARIATIONS IN DEW-POINT TEMPERATURES IN THE SOUTHERN UNITED STATES

Atmospheric humidity as measured by dew-point temperatures is an important component of the climate of the southern United States. The South experiences the country's highest dew-point temperatures throughout the year. A gradient is established between moist air along the Gulf and Atlantic coasts inland toward the drier areas of northwestern Texas. This gradient is strongest in winter and weakest in summer when consistent southerly circulation maintains humid conditions throughout the region. Interannual variability also is largest in the winter and smallest in summer. Dew-point temperatures are strongly related to air temperatures in the non-summer season, but are more fundamentally linked to air mass and circulation changes. Recent increases in southerly flow in the spring and autumn seasons have led to a significant increase in dew-point temperatures in many portions of the region. However, there is no evidence at this time to suggest that increased evaporation from greenhouse warming has altered dew-point temperatures in the southern United States.     

REGIONAL DEMOGRAPHIC STRUCTURE OF THE UNITED STATES

This paper analyzes the surprisingly great variation in demographic character across the states, utilizing data on fertility, mortality, age, sex, mobility, household character, abortion, race and ethnicity. A fairly simple regional pattern is revealed that is less related to levels of economic development than to long-standing historical cultural differences.     

AN INTEGRATED APPROACH TO AIR MASS CLASSIFICATION IN THE NORTH CENTRAL UNITED STATES

Both subjective and objective schemes for air mass classification offer advantages to climatological studies. An integrated approach is developed and applied to 850 mb level data in the north central United States. Each air mass type was initially delimited by a subjective analysis. Final limits were then determined with an objective technique that separates temperature curves into normal components based on interpretation from the subjective method. Continental air was most frequent in all seasons except summer. The methodology also allows estimation of classification error.     

AVOIDING THE DEMISE OF GEOGRAPHY IN THE UNITED STATES

This is the second of two articles about challenges that confront geography departments in a changing academic environment. College enrollment trends and tightening budgets are placing geography programs in jeopardy because the discipline is not considered by society to be indispensable. Departmental survival in a period of retrenchment may depend upon successfully demonstrating utility and quality, identifying unfilled niches in individual institutions, developing new interdisciplinary organizational arrangements, or finding ways to strengthen geography's position in governmental definitions of useful academic training.     

THE INTRAMETROPOLITAN LOCATION OF SERVICES IN THE UNITED STATES

In metropolitan areas, firms trade-off land and information costs. Firms that gain the most from access to the knowledge and know-how of other firms in the same sector are willing and able to pay for expensive central city land. We found that legal services, advertising, and accounting and auditing services are the most centralized services in the 74 largest metropolitan areas of the United States. Maps of seven fast-growing business and professional services in Phoenix, Arizona, show that central city services are mainly located in the CBD. Using a logarithmic function, we found that service jobs are more decentralized in the larger metropolitan areas and in metropolitan areas outside the Northeast. Analysis of disaggregate service sectors shows significant intersectoral variation in this relationship.     

THE DIURANAL DISTRIBUTION OF LARGE HAIL OVER THE UNITED STATES

The diurnal course of large hail varies over the United States. The time of maximum of large hail changes from near 1500 hours on the east coast to between 1800 and 1900 hours on the Great Plains. The north-to-south differences are smaller except near the Gulf Coast, where secondary maxima occur. In some areas the time of maximum of large hail differs from the maxima times of tornadoes, heavy rain, and thunderstorms.     

THE DIURANAL DISTRIBUTION OF LARGE HAIL OVER THE UNITED STATES

The diurnal course of large hail varies over the United States. The time of maximum of large hail changes from near 1500 hours on the east coast to between 1800 and 1900 hours on the Great Plains. The north-to-south differences are smaller except near the Gulf Coast, where secondary maxima occur. In some areas the time of maximum of large hail differs from the maxima times of tornadoes, heavy rain, and thunderstorms.