American air mass properties
Willett, Hurd C.
MetadataShow full item record
In this paper the term Air Mass is applied to an extensive portion of the earth's atmosphere which approximates horizontal homogeneity. The formation of an air mass in this sense takes place on the earth's surface wherever the atmosphere remains at rest over an extensive area of uniform surface properties for a suffciently long time so that the properties of the atmosphere (vertical distribution of temperature and moisture) reach equilibrium with respect to the surface beneath. Such a region on the earth's surface is referred to as a source region of air masses. As examples of source regions we might cite the uniformly snow and ice covered northern portion of the continent of North America in winter, or the uniformly warm waters of the Gulf of Mexico and Caribbean Sea. Obviously the properties of an air mass in the source region will depend entirely upon the nature of the source region. The concept of the air mass is of importance not only in the source regions. Sooner or later a general movement of the air mass from the source region is certain to occur, as one of the large-scale air currents which we find continually moving across the synoptic charts. Because of the great extent of such currents and the conservatism of the air mass properties, it is usually easy to trace the movement of the air mass from day to day, while at the same time any modification of its properties by its new environment can be carefully noted. Since this modification is not likely to be uniform throughout the entire air mass, it may to a certain degree destroy the horizontal homogeneity of the mass. However, the horizontal differences produced within an air mass in this manner are small and continuous in comparison to the abrupt and discontinuous transition zones, or fronts, which mark the boundaries between air masses. Frontal discontinuities are intensified wherever there is found in the atmosphere convergent movement of air masses of different properties. Since the air masses from particular sources are found to possess at any season certain characteristic properties which undergo rather definite modification depending upon the trajectory of the air mass after leaving its source region, the investigation of the characteristic properties of the principal air mass types can be of great assistance to the synoptic meteorologist and forecaster. We owe this method of attack on the problems of synoptic meteorology to the Norwegian school of meteorologists, notably to T. Bergeron. Investigation of the properties of the principal air masses appearing in western Europe has been made in particular by O. Moese and G. Schinze. The purpose of this paper is to give the results of a similar investigation of the properties of the principal air masses of North America, and to comment on some of the striking differences which appear between conditions here and in Europe.
Showing items related by title, author, creator and subject.
Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers Manning, Cara C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)In this thesis, I use coastal measurements of dissolved O2 and inert gases to provide insight into the chemical, biological, and physical processes that impact the oceanic cycles of carbon and dissolved gases. Dissolved ...
Coral biomineralization, climate proxies and the sensitivity of coral reefs to CO2-driven climate change DeCarlo, Thomas M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Scleractinian corals extract calcium (Ca2+) and carbonate (CO2−3) ions from seawater to construct their calcium carbonate (CaCO3) skeletons. Key to the coral biomineralization process is the active elevation of the CO2−3 ...
Biological-physical interactions on Georges Bank : plankton transport and population dynamics of the ocean quahog, Arctica islandica Lewis, Craig V. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-06)Advective losses of bank water during winter because of strong wind forcing were hypothesized to be a significant factor limiting recruitment of Georges Bank cormnunities. This hypothesis was examined using biological-physical ...