摘要
Based on the optical data for transmitted radiation through sea ice in the Arctic during the late autumn and early winterof 2007,the authors studied the arriving solar radiation,reflected radiation and transmitted radiation under very low solar altitude.Through the atmosphere,the light of the arriving solar radiation at short wavelength was weakened,with the spectral distribution ofdouble peaks centered at 490 nm and 683 nm.The magnitude of the peak at 683 nm even exceeded that at 490 nm under the very lowsolar radiation condition.The reflection was lower than that in summertime because of the thin thicknesses of ice and snow,allowinghigher ratio of heat to enter the sea ice and snow.When higher ratio of solar radiation entered sea ice in late autumn,the new icefreezing would be affected.The spectral reflectivity from snow surface was almost a constant,but the reflection without snow de-creased at longer wavelengths.In the transmission spectrum,the light of 490 nm was dominant.It indicates that the radiation atlonger wavelength was weakened by sea ice.Therefore,under the condition of low solar altitude,the radiation at shorter wavelengthwas weakened by the atmosphere while the radiation at longer wavelength was weakened by the sea ice.The combined effect of at-mosphere and sea ice made the solar radiation under sea ice much weaker.The absorption of sea ice for the longer-wavelength radiation allowed the sea ice to gain more heat to slow down the freezing process.
Based on the optical data for transmitted radiation through sea ice in the Arctic during the late autumn and early winter of 2007, the authors studied the arriving solar radiation, reflected radiation and transmitted radiation under very low solar altitude. Through the atmosphere, the light of the arriving solar radiation at short wavelength was weakened, with the spectral distribution of double peaks centered at 490 nm and 683nm. The magnitude of the peak at 683 nm even exceeded that at 490 nm under the very low solar radiation condition. The reflection was lower than that in summertime because of the thin thicknesses of ice and snow, allowing higher ratio of heat to enter the sea ice and snow. When higher ratio of solar radiation entered sea ice in late autumn, the new ice freezing would be affected. The spectral reflectivity from snow surface was almost a constant, but the reflection without snow decreased at longer wavelengths. In the transmission spectrum, the light of 490 nm was dominant. It indicates that the radiation at longer wavelength was weakened by sea ice, Therefore, under the condition of low solar altitude, the radiation at shorter wavelength was weakened by the atmosphere while the radiation at longer wavelength was weakened by the sea ice. The combined effect of atmosphere and sea ice made the solar radiation under sea ice much weaker. The absorption of sea ice for the longer-wavelength radiation allowed the sea ice to gain more heat to slow down the freezing process.
基金
supported by the key project of the National Nature Science Foundation of China‘Study on the structure of Arctic Circumpolar Boundary Current and its impact on climate change’(Grant No.40631006)
by the Chinese International Polar Year Project
supported by Professor David Barber atthe University of Manitoba of Canada
