The record of tornado fatalities in the United States for over two centuries (1808–2017) and decadal census records have been examined to search for historical trends. Particular attention has been given to the response to population growth and expansion into the tornado-prone regions of the country. The region selected includes the Tornado Alley of the central Great Plains, the Dixie Alley in the southeastern states, and the adjoining states in the Midwest that collectively encompass a 21-state rectangular region. The data record has been divided into two subintervals, Era A (1808–1915) and Era B (1916–2017), each of which consists of three equal-length periods. Era A is characterized by a growing and westward expanding population along with a basic absence of scientific knowledge, technology, and communications (for prediction, detection, and warning). This is followed by a renaissance of discovery and advancement in Era B that contributes to saving lives. The aforementioned periods are defined by a set of notable events that help to define the respective periods. A death per population index (DPI) is used to evaluate the 21 states in each era; there is a rise of mean DPI values to a maximum of 1.50 at the end of Era A and a subsequent fall to 0.21 at the end of Era B. It is also shown for all three periods in Era B that the deadliest tornado states, in ranked order, are Arkansas, Mississippi, Alabama, and Oklahoma. Suggestions are presented for ways to continue the decreasing trend in DPI, which would imply that the death rate increase is not as fast as the rate of population increase (or would even imply a decreasing death rate).
This study uses a set of idealized aquaplanet model experiments to investigate the linkage between the Asian summer monsoon circulation and tropopause fold activity. It is found that folds tend to occur on the northwestern side of the upper‐level anticyclone associated with the monsoon circulation and are generated due to intensified monsoon circulation and resulting intensified subsidence. In addition, the impact of tropopause folds on extreme rainfall events is also examined. It is found that while the likelihood of extreme rainfall is largely decreased at and upstream of the occurrence of folds, the likelihood is significantly increased downstream. This pattern of suppression of extreme rainfall upstream and promotion downstream also persists for about 1–2 days, which likely suggests a positive feedback between extreme rainfall downstream and tropopause folds. Finally, changes in tropopause folds with monsoon intensity are also discussed.
The different sources and varying grades of kieselguhr filter aids on offer commercially are discussed, and a standard scheme of analysis is suggested. This scheme is designed to cover in general the effect of kieselguhr on beer, the efficiency of filtration, and the presence of impurities in the kieselguhr. A number of analyses are quoted, and the inferences which can be drawn from them are indicated.
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