極域における雪氷中の光吸収性エアロゾルとその光学特性

概要

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Light absorbing aerosols such as black carbon (BC) and mineral dust deposited on snow/ice surface reduce albedo and accelerate snow/ice melting. Through the radiative transfer calculation for the atmosphere-snow system, light absorbing aerosol concentration which reduces the snow albedo by 0.01 is approximately several to several tens ppbw for BC and 103 to 104 ppbw for the mineral dust. BC concentrations have been measured from in-situ snow samples since 1980s and from ice core even for a longer period. Greenland ice core records show high BC concentration during 1850-1950 due to industrial activities, and the BC measurements for in-situ snow samples indicate high values during 1980s in a wide area of the Arctic except Greenland. These high BC concentrations are the level which reduces the snow albedo by more than 0.01. Climate modeling studies including the effect of BC and dust in snow show that globally annual-mean radiative forcing due to BC (or dust) is less than 0.1W/m2, while their regional effect for a specific period is much higher. However, there are many issues to be dealt with in modeling studies as well as the measurement techniques of light absorbing aerosols in snow/ice.