Collaborative Research: Direct radiative forcing over central Greenland; Assessment of the coupled effect of light absorbing aerosols and snow albedo variability

PI将进行关键测量，以准确估计格陵兰岛中部冰盖上空气溶胶的直接辐射强迫。采样将在2011年春季至秋季的田间季节进行。 它将包括实时测量气溶胶物理和光学特性（尺寸分布、多波长散射系数、反向散射系数以及多波长吸收系数），以估计气溶胶单次散射系数和不对称参数g。还将进行波长相关光学深度#964;#955;以及光谱表面反射率Rs的额外测量。这些数据将作为辐射转移模型的输入，该模型将用于估计格陵兰上空大气层表面和顶部的直接气溶胶辐射作用力。直接辐射强迫的来源和源区将由采样气溶胶的化学成分确定。 据推测，灰尘，生物质燃烧和化石燃料燃烧气溶胶往往施加一个积极的直接辐射强迫比人为温室气体的许多倍。 额外的表征雪的雾，这发生在几个小时到几天的时间尺度，将确定它是否也对首脑会议的直接气溶胶强迫产生重大影响。将在高时间频率下确定表面雪颗粒特性和表面雪化学，以探索这些特性的变化与表面雪之间的联系。

The PIs will make key measurements needed to accurately estimate the direct radiative forcing by aerosols over the central Greenland ice sheet. Sampling will take place over a field season that will occur from the spring through fall of 2011. It will include real-time measurements of aerosol physical and optical properties (size distribution, multi-wavelength scattering, σsp, and backscattering, σbsp, coefficients as well as the multi-wavelength absorption coefficient, σap) needed to estimate the aerosol single scattering albedo, ω, and asymmetry parameter, g. Additional measurements of the wavelength-dependent optical depth, τλ, as well as the spectral surface reflectance, Rs will also be made. These data will serve as input to a radiative transfer model that will be used to estimate the direct aerosol radiative forcing at the surface and top of the atmosphere over Greenland. Sources and source regions of the direct radiative forcing will be determined by the chemical composition of the aerosols sampled. It is hypothesized that dust, biomass burning and fossil fuel combustion aerosols often exert a positive direct radiative forcing many times greater than that of anthropogenic greenhouse gases. Additional characterization of snow albedo, which varies occurs on timescales of hours to days, will be made to determine whether it, too, exerts a significant influence on the direct aerosol forcing over Summit. Surface snow grain properties and surface snow chemistry will be determined at high temporal frequency to explore the link between the variability in these properties and the surface albedo.