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

PI将进行必要的关键测量，以准确估计格陵兰中部冰盖上空气溶胶的直接辐射强迫。抽样将在2011年春季至秋季的田间季节进行。它将包括估计气溶胶单次散射反照率和非对称性参数所需的气溶胶物理和光学性质的实时测量(粒度分布、多波长散射、后向散射、BSP系数和多波长吸收系数)，以及非对称性参数，例如，还将对依赖于波长的光学厚度以及光谱表面反射率Rs进行额外测量。这些数据将作为辐射传输模型的输入，该模型将用于估计格陵兰上空大气表面和顶部的直接气溶胶辐射强迫。直接辐射强迫的源和源区将由采样的气溶胶的化学成分来确定。据推测，尘埃、生物质燃烧和化石燃料燃烧气溶胶往往产生比人为温室气体大许多倍的正直接辐射强迫。雪的反照率在几小时到几天的时间尺度上有不同的变化，将对其进行额外的表征，以确定它是否也对峰会上的直接气溶胶强迫产生重大影响。将在较高的时间频率上确定地面雪粒特性和地面雪化学，以探索这些特性的可变性与地面反照率之间的联系。

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.