1941: Meteorology

The military situation continued to be a stimulus to research in Meteorology. Greater emphasis was placed upon applied meteorology than upon theoretical owing to immediate Army and Navy requirements. Many meteorologists devote all of their time to research in behalf of defense. Some of the findings are temporarily retained as military secrets and hence may not be revealed until the end of the war.

Research.

Expansion of departments and institutes of Meteorology has gone on apace. As an illustration of the vigor of this activity, may be cited the Institute of Meteorology at the University of Chicago which opened in the middle of 1940 with fifteen students taking advanced training and concluding its first year with some sixty-five or more men in regular attendance. The researches of this institute have been extended to include the measurement and recording of cosmic ray intensities. A hydrodynamic laboratory has been planned and special studies of the circulation of the atmosphere with reference to improvements in long-range forecasting were brought under way.

Researches in the field of micro-meteorology have continued. These involve detailed observations made at stations spaced a few miles apart or lesser distances thus affording enough data when plotted to reveal the internal dynamics of air masses as they move across the earth's surface. These studies are contributing to a better knowledge of the behavior of atmospheric moisture and the allied problems of evaporation, floods and run-off.

Lightning Discharges.

New light has been shed upon the phenomenon of lightning discharges or 'strokes.' The Westinghouse laboratories became interested in determining 'safe places' for man during thunderstorms. Among their experiments was one involving the discharge of a bolt of artificial lightning with a strength of 3,000,000 volts against the steel top of an automobile. A driver was seated at the wheel and felt no effects. The current was discharged to the earth through a tire and left only a small burn on the metal top of the car at the point of contact. This experiment confirmed the well known fact that a metal cage serves as an electrical screen. Nevertheless, the results of applying a charge as great as that of natural lightning to a metal enclosure gave satisfaction to the observers. These same laboratories pursuing the study further, concluded that the out-of-doors is the most dangerous location for the human during a thunderstorm. Most deaths from lightning stroke occur in rural regions and on level open areas.

Ocean Currents.

At the Scripps Institution of Oceanography, La Jolla, Calif., investigations of the relation between ocean currents and weather continued to show progress. While for many years meteorologists have been familiar with the heating and cooling effects of ocean waters upon air masses, specific effects are now being determined. For example, certain currents radiate their heat irregularly instead of in a constant flow. The Kuroshio gives off large amounts of heat as it flows southward in the eastern Pacific. This uneven distribution of heat, combined with the effects of evaporation from the sea surface has its repercussions in the building up of low pressure areas over the ocean in winter. This pressure reaction in turn affects conditions over considerable areas of both the ocean and adjacent continents. Some apparent climatic changes, probably only cyclical, have been noted in the Galapagos Islands and along the dry west coast of South America, due to a shift in the Humboldt current. The temperature has risen and rainfall has increased.

Importance of Weather Forecasts during Wartime.

In 1939 the British attempted to prevent Germany from securing weather data from points in northern North America or over the northern part of the North Atlantic Ocean. The purpose was to handicap Germany in such military activities on the continent or the ocean as might be planned in relation to the weather. A question was raised as to the probable consequences of this effort. The answer seems to have been given late in 1941 by a U.S. Navy report, which related the capture of a German crew with equipment for making weather observations and for sending radio messages, while attempting to establish itself upon the east coast of Greenland. Since a forecast of the weather over the eastern Atlantic and western Europe depends largely upon the availability of data from places westward, that is, since northwestern European weather is the consequence of the westward drift of cyclones and anticyclones, absence of data from the North American region greatly handicaps European forecasters. In this somewhat negative manner, we have added convincing evidence that the assumptions just made, assumptions which have been held for many years, still hold true.

Tropical Meteorology.

The establishment of United States naval bases in the Caribbean has aroused new interest in tropical meteorology. These studies focus largely upon the origin, development, and movement of air masses in the tropics. An understanding of the great Azores permanent high pressure is especially pertinent in relation to the eastward movement of cyclones, particularly of hurricane proportions. The play of 'cold' and 'warm' fronts as affected by local atmospheric conditions and in turn their influence upon the local atmosphere are other phases of the complexities of tropical climates, particularly in the Caribbean area.

U. S. Weather Bureau.

The year 1941 marked the fiftieth anniversary of the U.S. Weather Bureau's civilian status. In 1891 it was transferred from the U.S. Army Signal Corps, where it has been since 1870, to the jurisdiction of the United States Department of Agriculture. In 1940 it was shifted to the Department of Commerce. During this half century, the Bureau expanded enormously. Originally there were less than 100 observing stations. Today there are 800 stations. In addition to forecasting the weather from day to day, many special services have been added, such as Flood, Hurricane and Special Frost forecasts. The Storm Warning Service has been greatly augmented. Some 50 radiosonde stations have been established where observations are made twice daily. Forecasts have been notably improved, thanks to a change from more or less empirical methods to more exact bases involving the now well known air-mass analysis.

Coincident with the completion of these years of service the Weather Bureau has changed the character of its daily map. Instead of drawing the map based on observations made at 7:30 A.M. it is prepared from data taken at 1:30 A.M. Only two isotherms, freezing and zero, are shown in place of isotherms for every ten degrees which appeared on older maps. More actual data are placed on the face of the map next to the station than have heretofore been recorded. Also cold and warm fronts are indicated. All of these improvements are in line with, and are the outgrowth of, general meteorological progress which the Weather Bureau has made especially during the past ten years. The map issued at headquarters in Washington will as heretofore show more detail than maps published at outlying stations.