Cloud microphysics and surface properties in climate

• Main Author: Stamnes, K.
• Language: unknown
• Published: 2018
• Subjects: 54 ENVIRONMENTAL SCIENCES; CLOUDS; OPTICAL PROPERTIES; PHYSICS; ENVIRONMENTAL EFFECTS; EARTH PLANET; AMBIENT TEMPERATURE; CLIMATE MODELS; Arctic; Sea ice
• Online Access: http://www.osti.gov/servlets/purl/232609; https://www.osti.gov/biblio/232609; https://doi.org/10.2172/232609

Cloud optical thickness is determined from ground-based measurements of broadband incoming solar irradiance using a radiation model in which the cloud optical depth is adjusted until computed irradiance agrees with the measured value. From spectral measurements it would be feasible to determine both optical thickness and mean drop size, which apart from cloud structure and morphology, are the most important climatic parameters of clouds. A radiative convective model is used to study the sensitivity of climate to cloud liquid water amount and cloud drop size. This is illustrated in Figure 21.1 which shows that for medium thick clouds a 10 % increase in drop size yields a surface warming of 1.5{degrees}C, which is the same as that due to a doubling of carbon dioxide. For thick clouds, a 5% decrease in drop size is sufficient to offset the warming due to doubling of carbon dioxide. A radiative transfer model for the coupled atmosphere/sea ice/ocean system is used to study the partitioning of radiative energy between the three strata, and the potential for testing such a model in terms of planned experiments in the Arctic is discussed.