Aerosol-Cloud-Radiation Interactions in the Arctic

这笔赠款支持一项关于北极雾霾与低层云相互作用影响地面长波和短波辐射通量的调查。它是基于对阿拉斯加州巴罗附近两个观测点的数据进行分析的。一个是NOAA气候监测和诊断实验室(CMDL)，它测量地面附近的气溶胶浓度；另一个是美国能源部大气辐射测量(ARM)站点，它用地面遥感设备监测云和大气辐射特性。新的和现有的算法将用于从观测中推断云的微结构、净辐射通量和降水的存在。从现有的长期记录中，将有可能研究这些数量的年度和年际变化。云凝结核(CCN)的浓度将根据地面对气溶胶浓度和散射太阳辐射的测量来估计。这需要关于云滴大小分布的信息，这些信息将基于1998年春在北极进行的华盛顿大学LEADEX实验和其他野外实验的档案数据。该项目将评估一种假设，即污染导致的北极雾霾导致层云水滴较小但较多，从而导致北极冬季和初春的红外发射率更高，地表长波加热增加。此外，它还将提供有关冬季北极云组成的新信息，人们对此知之甚少。这一结果将改进气候模型中云的辐射特性的处理。

This grant supports an investigation of the way arctic haze interacts with low-level clouds to affect longwave and shortwave radiative fluxes at the ground. It is based on analysis of data from two observational sites near Barrow, Alaska. One is the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL), which measures aerosol concentrations near the ground; the other is the DOE Atmospheric Radiation Measurement (ARM) site, which monitors cloud and atmospheric radiative properties with ground-based remote sensing equipment. New and existing algorithms will be used for inferring cloud microstructure, the net radiative flux, and the presence of precipitation from the observations. From the long records available, it will be possible to study the annual and interannual variability of these quantities. Concentrations of cloud condensation nuclei (CCN) will be estimated from measurements at the ground of aerosol concentration and scattered solar radiation. This requires information about the cloud droplet size distribution, which will be based on archival data from the University of Washington LEADEX experiment conducted in the Arctic in the spring of 1998 and from other field experiments. The project will evaluate the hypothesis that pollution-induced arctic haze causes stratus clouds to have smaller but more drops, leading to a higher infrared emissivity and increased longwave surface heating in the arctic winter and early spring. In addition, it will provide new information on the composition of wintertime arctic clouds, about which little is known. The results will lead to improved treatment of the radiative properties of clouds in climate models.