Showing papers by "Harry van Loon published in 1972"

The zonal harmonic standing waves in the southern hemisphere

Abstract: We have examined the zonal harmonic waves in the southern hemisphere by means of longterm average heights of constant-pressure surfaces from sea level to 100 mb and by daily 500-mb heights, and found that waves 1, 2, and 3 have significant standing components. Wave 1 at extratropical latitudes has one peak in the subpolar regions and another in the subtropics. The ridge of the subpolar region is in the Pacific and the ridge of the subtropical region is in the Atlantic Ocean. The phase changes near 40°S where the amplitude tends toward nought. In summer the wave is biggest near the tropopause but in winter it continues to grow into the stratosphere over the area where the temperature drops poleward. Wave 2 has a large standing component over Antarctica with its ridges over the highest parts of west and east Antarctica. There is a well-defined wave 3 between 25° and 60°S in all months, with ridges near the three lower-latitude continents. In addition the wave has a marked peak in the upper tropical troposphere in summer, which is in phase with that at higher latitudes.

Pressure in the Southern Hemisphere

Abstract: The general distribution of mean pressure at sea level over the Southern Hemisphere has been known since Buchan’s maps were published in 1869. Many others have since appeared, the best known of which are those in Hann’s textbook (1901), and in Shaw’s Manual of Meteorology (1927). Meinardus and Mecking (1911b) combined a series of daily synoptic maps (1 October 1901–31 March 1904) into monthly mean pressure maps of much of the area south of 305, which are still very valuable because of the careful analysis and of the many ships’ observations then, where few, if any, are taken now. Meinardus (1928, 1929) used this series in a study of the pressure which is instructive and unsurpassed, but often ignored. Pressure in the Southern Hemisphere has also been treated by Spitaler (1901), Reuter (1936), Wahl (1942), Gordon (1953), Vowinckel (1955), Schwerdtfeger and Prohaska (1956), Hofmeyr (1957a), van Loon (1961), and Pflugbeil (1967).

Cloudiness and Precipitation in the Southern Hemisphere

Abstract: The total cloudiness over all or part of the Southern Hemisphere has been discussed by Brooks (1927), Landsberg (1945), Vowinckel and van Loon (1957), Clapp (1964) and Sadler (1969), and is shown in the marine climatological atlases of Germany, the Netherlands, United Kingdom, and the United States of America. Figs. 6.1–6.3, which result from a subjective fusion of these sources, probably give a reasonable picture of the total cloudiness.

The Stratosphere in the Southern Hemisphere

Abstract: The stratosphere over the Southern Hemisphere was known only locally and mainly in its lowest levels until satellite measurements of radiance became a reality. As we are using these recent data in addition to midseason, monthly mean maps for 1969 as principal means of description, much of our material is unlikely to be representative of long-term conditions, and our conclusions cannot always be so firm as we may seem to express them. In addition, necessity limits us to deal chiefly with the lower half of the stratosphere, below 10 mb. We have tried, however, to ease these severe restrictions by referring as often as possible to the better known Northern Hemisphere for analogy and contrast. Some aspects of the mean state of the stratosphere below 100 mb have been dealt with in Chapters 3–5.

Half‐yearly wave in the stratosphere

Abstract: The dominant features of the half-yearly wave in the stratospheric temperature above the 50-mb level are an amplitude peak in equatorial latitudes, the maximums being in the transition seasons, and amplitude peaks at higher latitudes of either hemisphere, the maximums being in the extreme seasons. The low- and high-latitude peaks are separated by a circumpolar belt of low values in the subtropics where the phase changes rapidly. The half-yearly wave in the zonal thermal wind, at least as high as 5 mb, reaches a peak in the subtropics where the phase in the temperature wave reverses, and the half-yearly wave in the geostrophic and the observed zonal wind above 50 mb accordingly increases poleward to latitudes of 30°–35° from a minimum a few degrees north of the equator and upward. The wave in the zonal wind reaches another, but weaker, peak in the polar regions.

Wind in the Southern Hemisphere

Abstract: The two editions of “Upper Winds over the World,” by Brooks, Durst, Carruthers, Dewar and Sawyer (1950) and Heastie and Stephenson (1960), and the atlases by Dubentsov and Davidova (1964), Guterman (1967), van Loon, Taljaard, Jenne and Crutcher (1971), and Jenne, Crutcher, van Loon and Taljaard (1971) provide comprehensive descriptions of the wind in the Southern Hemisphere. Other studies of the wind on the scale of the hemisphere, but of smaller volume than those above, were made by Flohn (1950), Jenkinson (1955), Lamb (1959), Phillpot (1962), Obasi (1963) and van Loon (1964). There are regional studies of the Indian Ocean by Lockwood (1963) and Frost and Stephenson (1965); of the African region by Hofmeyr (1961, 1962); and of South America by Schwerdtfeger and Martin (1964). The outstanding observations of the upper winds at Kerguelen Island (49S, 70E) are described by Barbe, Dumas and Reininger (1967).

Temperature in the Southern Hemisphere

Abstract: The characteristics of the temperature which are needed to describe the mean state of the atmosphere in space and time are stressed in this chapter. The parts on changes in time are restricted to the annual march of the mean temperature as expressed by its first two harmonic components, and other changes have been omitted regardless of their amplitude and scale. Even such large-scale variations as those within the Southern Oscillation have been left out since they are associated with irregular time variations in the ocean and atmosphere.