Contribution to a comparative meteorology of n10untain areas

A COMPARATIVE METEOROLOGY OF MOUNTAIN AREAS 59the flux of sensible and oflatent heat (evaporation) and their relationship to each other (the Bowen ratio). This relationship fluctuates very greatly, often with box fluxes changing signs. Table 2B.l gives several interesting evaluations ofsuch measurements. Data have been computed for the mountains of Soviet Central Asia (Aisenshtat, 1966), the Karakoram Mountains (Untersteiner, 1958a,b), the Tien Shan (Skeib, 1962), the Himalaya (Haeckel et ai., 1970; Kraus, 1971), and for the Paramo in equatorial Ecuador (Korff, 1971). Schichlinski (1966) has determined the fluxes oflatent and sensible heat in the Caucasus, and found strong variations related to the duration of snow cover (table 2B.2). .\.,Table 2B.2. Heat fluxes and elevation in the Caucasus; yearly averages (ly day-i) (afterSchichlinski, 1966).Elevation(m) 200 600 1000 15°0 2000 2500 3 000 3500 4000 Greater Caucasus L·E 55 73 84 79 74 64 55 45 33 U L 74 62 50 39 29 21 14 7 2 Lenkoran Mountains L·E 112 99 79 58 38 22 (38·5°N,48·5°E) U L 4B 56 66 78 90 99 The sensible heat flux, with its horizontal variation, produces primarily thermallydriven circulations which make up the entire hierarchy of diurnal wind systems in ourmountains. However, as soon as these diurnal circulations produce rain in addition tothe clouds - and only this irreversible process is determinant - a heat source is producedwhich is strong enough to maintain thermal circulations even when the primary heatsources are long gone (Flohn, 197ob; Flohn and Fraedrich, 1966; Fraedrich, 1968).We must then consider the heat budget of the atmosphere rather than that of theearth's surface. Measurements from satellites are most useful for this study. Theradiation budget (Qatm) of the atmosphere is composed of different radiation fluxes justas the heat budget LlW of an air column is influenced by different horizontal andvertical heat fluxes:Q.tmSo(l-a p )-(S+H)s(l-as)+(Et- Gt). EoThe first two terms on the right are short-wave contributions, the last two are long-wave.LlW = Q.lm + U L+ L·P + div (! cppTV dZ)Where Q.tm is the radiation budget ofa vertical air column, LlW is the heat budget ofanair column, So is solar radiation at the upper boundary of the atmosphere, (S + H)s isglobal radiation at the earth's surface, (Et - Gt)s is effective terrestrial radiation,apis planetary albedo, a. is terrestrial (surface) albedo, Eo is the long-wave emission atthe upper boundary of the atmosphere (Eo and a p are measured by meteorologicalsatellites), Gt is downward long-wave radiation from the atmosphere, U L is sensibleheat flux at ground level, P is precipitation, L is latent heat ofcondensation, c p is specific