The origin and evolution of dust clouds in Central Asia

Abstract

Data from a high resolution radiometer AVHRR (580–680 nm optical lengthwaves) installed on the “NOAA-11” satellite as well as TV (500–700 nm) and IR (8000–12000 nm) equipment of the Russia satellite “Meteor-2/16” were used to study the evolution of dust storms for 1–30 September 1989 in Tajikistan, Uzbekistan, Turkmenistan and Afghanistan. These data help to validate the hypothesis, that long-term dusted boundary layer (duration of the order of a day or more), but of comparatively not high optical density (4–10 km meteorological visibility range at the 20–50 km background), is formed after the northwest intrusions into a region of intensive cold fronts at the surface wind velocities of 7–15 m/s. Stability of dust clouds of vertical power to 3–3.5 km (up to an inversion level) is explained by an action of collective buoyancy factors at heating the dust particles of 2–4 μm in mean diameter by solar radiation. The more intensive intrusions stimulate a formation of simultaneously dust and water clouds. The last partially reduce the solar radiation (by the calculations of the order of 30–50%) and decrease the role of buoyancy factors. Thus, initiated is the intensive but short-term dusted boundary layer at horizontal visibility of 50–200 m.