APPLICATION OF THE POLAR-FRONT THEORY TO A SERIES OF AMERICAN WEATHER MAPS

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  • 1 U. S. Weather Bureau, Washington
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Abstract

SYNOPSIS

1. In order to show the applicability of the polar-front theory to the study of American weather a series of synoptic maps, comprising the period February 16–19, 1926, hss been subjected to a detailed analysis by the methods of the Norwegian Meteorological School. The type discussed below, a weak depression from the Northwest slowly approaching the lower Mississippi Valley, and there increasing in intensity under advection of warm, moist air from the Gulf and cold air from Canada, occurs frequently. It offers a good example for analysis, as the depression is built up of at least four different air masses. It is found that in spite of the few data from the West the history of the LOW can be satisfactorily outlined, at least in its general features.

2. The methods used in locating the fronts are discussed, several examples being given.

3. The upper-air data are discussed and employed for identification of the different air masses. The free-air temperatures prove very valuable for this purpose, since in the upper levels the air masses seem to a great extent to preserve their characteristic temperatures.

4. The aerological data are also used for a discussion of the stability of the atmosphere over the Gulf States. In this connection upper-air convection in the South is treated and reasons given why this kind of convection plays such an important rôle in the United States while it is almost without significance in Europe.

5. As a result of the analysis of the maps according to the polar-front theory it is found that several improvements in the character and amount of the observations in this country are highly desirable and some suggestions to that effect are offered.

Abstract

SYNOPSIS

1. In order to show the applicability of the polar-front theory to the study of American weather a series of synoptic maps, comprising the period February 16–19, 1926, hss been subjected to a detailed analysis by the methods of the Norwegian Meteorological School. The type discussed below, a weak depression from the Northwest slowly approaching the lower Mississippi Valley, and there increasing in intensity under advection of warm, moist air from the Gulf and cold air from Canada, occurs frequently. It offers a good example for analysis, as the depression is built up of at least four different air masses. It is found that in spite of the few data from the West the history of the LOW can be satisfactorily outlined, at least in its general features.

2. The methods used in locating the fronts are discussed, several examples being given.

3. The upper-air data are discussed and employed for identification of the different air masses. The free-air temperatures prove very valuable for this purpose, since in the upper levels the air masses seem to a great extent to preserve their characteristic temperatures.

4. The aerological data are also used for a discussion of the stability of the atmosphere over the Gulf States. In this connection upper-air convection in the South is treated and reasons given why this kind of convection plays such an important rôle in the United States while it is almost without significance in Europe.

5. As a result of the analysis of the maps according to the polar-front theory it is found that several improvements in the character and amount of the observations in this country are highly desirable and some suggestions to that effect are offered.

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