Physics of the air

Abstract

Air-mass and energy transportation is chiefly made by large lenses of cold air, the Mobile Polar Highs, the key factor of meridional air exchanges, which organize migratory units of circulation in troposphere low levels. Mobile Polar Highs (MPHs) originate in the downwards airmotion in high latitudes. The cold air injection organizes a dipolar vortex of very large size (2000/3000 km), the anticyclonic side of this vortex (precisely the MPH) is thin, about 1.5 km thick, by reason of cold air density. Mobile Polar Highs migrate roughly eastwards, with a meridional component towards the tropical zone, through the middle latitudes where they are responsible for weather variability and for rain-making conditions. Their own thermo-dynamic evolution and relief divide them into fragments, and they supply the low-layer of the trade circulation, and eventually the monsoon (previously trade) circulation of a cross-equatorial drift. Eastwards movement and disposition of relief govern the MPHs paths and determine distinct aerological domains; in one of these domains, China is precisely located at the eastern Asian exit of MPHs, stopped by the Himalaya/Tibet range, on their southern side during their eastwards migration. Power of the MPH, connected with its density, as observed in winter in the present conditions, is a function of the initial temperature, namely of the polar radiative conditions. It is precisely in the high latitudes that radiation balance and temperature changes are the most important, at all scales of time, from the seasonal to the palaeoclimatic scale, while in tropical latitudes the changes are comparatively always weak. Two modes of troposphere general circulatin are a result of this mechanism: (1) A rapid mode of circulation, connected with acold situation in polar latitudes, is characterized by strong and extended MPHs and strong wind at all latitudes and all levels. (2) A slow mode of circulation, connected with a warm situation in polar latitudes, is characterized by weak and less extended MPHs, and weak winds at all latitudes and all levels. Insolation and surface boundary conditions of high latitudes are the key control of MPHs dynamics, and therefore the key control of palaeoclimatic changes.