Subtropical anticyclone

C) and the low productivity SW Pacific subtropical anticyclonic gyre (Area K), Stoffers et al. (1981) showed that the siliceous oozes from the equatorial North Pacific have much higher contents of Mn, Ni, Cu and Ba but lower contents of Fe and Co than the red clays from the SW Pacific (Table 11.3). Sedimentation rates on a carbonate-free basis for the two areas are of the same order (1-3 mm ka for the equatorial North Pacific and 0.5-1 mm ka" for the SW Pacific). Differences in the transition metal contents of these sediments were therefore considered to be eontrolledby sediment type rather than sedimentation rate. Caleulations based on the equations of Bischoff et al. (1979) confirmed that the hydrogenous (authi-genic) eomponent was much higher in Area C (7.9%) than in Area K (3.2%) sediments. 

An element of the cyclone-anticyclone phenomenon that has particular importance for air pollution in several parts of the world is the semipermanent subtropical anticyclone, high-pressure regions centered over the major oceans. They are called semipermanent be-... 

On the eastern side of the subtropical anticyclones the inversion is strengthened by the southerly flow of cool, dry air (recall that in the Northern Hemisphere the rotation in an anticyclone is clockwise). Particularly in coastal areas the low-level air is cooled by contact with the cold ocean, an exchange that tends to strengthen the inversion. Since the air aloft, as well as the southbound low-level flow, is warming, there is little precipitation in these regions. Thus on the west coasts of continents it is common to find arid, desert-like conditions, such as the deserts of southern California, the Sahara in North Africa, the desert in western Australia, and the coastal plains of South America. 

In the summer, the subtropical high pressure belt with its typical anticyclonic weather types is displaced more and more to central and northern Europe, which is reflected by the strong warming of the months from August to September by about 0.2-0.3°C. Looking at the... 

Fig. 1-6. Mean zonal circulation in the northern hemisphere, 0-20 km. Distribution of wind velocities (in units of m/s) was taken from Labitzke (1980). W, Mean winds from the west E, mean winds from the east the heavy lines indicate the approximate location of the polar front, the broken lines the tropopause. The maximum wind speed coincides approximately with the subtropical jet stream. The location of the polar jet fluctuates considerably and does not show up in the average. The center is to illustrate wind directions near the earth surface (trade winds and westerlies) cyclones (C) and anticyclones (A) imbedded in the westerlies are only sketched the frontal systems associated with cyclones cannot be shown in this extremely simplified diagram.

De Vooys (1979) summarised the influences of environmental factors on the primary production in the world ocean as follows At lower latitudes, especially in subtropical regions, open ocean water contains little nitrogen and phosphorus and as a consequence these areas have a low primary production (about 30 g C m yr" ). In anticyclones the water column has a great stability, an absence of silt and low amounts of algae and often no water transport, together determining primary production. 

On the other hand, on the western side of the semipermanent anticyclone, inversions are less frequent and the low-level air from the tropics is warm and moist. As it cools on its path to the north, precipitation is heavy. Thus the eastern coasts of continents in the subtropics are warm and humid, such as the eastern coasts of South America and Africa. 

We can now see one of the reasons why Los Angeles is afflicted with air pollution problems. Its location on the west coast of North America in the subtropical region and on the eastern side of the Pacific anticyclone is one in which elevated inversions are frequent and strong. The lowest layer of air (the marine layer) is cooled because of its contact with the ocean. Air pollutants are trapped in the marine layer and prevented from vertically exchanging with upper-level air. Such a situation can lead to serious air pollution problems. The base of a subsidence inversion lies typically at an elevation of about 500 m, with the inversion layer extending another 500 to 1000 m upward. 

There is the relationship between the interannual variability in the index of the SCS Warm Water and the monsoon break over the SCS. The SCS Warm Water, and the warm pools in both the western equatorial Pacific and the Indian Oceans are in the same coupled system on a large scale, sharing a long period of oscillation of about 4.8 years. During the years when colder water occurs in the SCS, an atmospheric anticyclone maintains itself to the east of the Philippines in summer. A low frequency activity associated with the anticyclone results in low frequency oscillation in the precipitation field over this region, whereas the weak subtropical high over the western Pacific travels eastward in summer, which is responsible for the anomalous distribution of meridional vapor transport. 

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