Determine how centers of action, migratory systems, and seasonal variations affect secondary air circulations, and determine how their vertical structure is affected by the mean temperature and vertical spacing of isobars.

SECONDARY CIRCULATION 

Now that you have a picture of the GEN-ERAL circulation of the atmosphere over Earth, the next step is to see how land and water areas offset the general circulation. The cir-culations caused by the effect of Earths SUR-FACES, its composition and contour, are known as SECONDARY CIRCULATIONS. These sec-ondary circulations give rise to winds that often cancel out the normal effect of the great wind systems.

There are two factors that cause the pressure belts of the primary circulation to break up into closed circulations of the secondary cir-culations. They are first, the nonuniform sur-face of the earth and second, the difference in heating and cooling of land and water. The surface temperature of oceans changes very little during the year. However, land areas sometimes undergo extreme temperature changes with the seasons. In the winter, large high pressure areas form over the cold land and low pressure areas form over the relatively warm oceans. The reverse is true in summer when highs are over water and lows form over the warm land areas. The result of this difference in heating and cool-ing of land and water surfaces is known as the thermal effect.

Circulation systems are also created by the interaction of wind belts of pressure systems or the variation in wind in combination with certain distributions of temperature and/or moisture. This is known as the dynamic effect. This effect rarely, if ever, operates alone in creating second-ary systems, as most of the systems are both created and maintained by a combination of the thermal and dynamic effects.

Learning Objective: Determine how centers of action, migratory systems, and seasonal variations affect secondary air circulations.

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing