Guest lecture at CIRFA and the Department of Physics and Technology, UiT, Friday 6 November, 14:15, auditorium 2.017 in the Technology building.
“The role of clouds on the surface energy balance of Greenland: Results for the ICECAPS experiment at Summit Station” by Von P. Walden, Professor at the Laboratory for Atmospheric Research at Washington State University.
Abstract: The Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation over Summit (ICECAPS) experiment has been conducted at Summit Station, Greenland (72.5 N, 38.4 E; 3200 m) since May 2010. A comprehensive suite of instruments has been operated nearly continuously to characterize atmospheric and cloud properties. The instruments include a cloud radar, two aerosol and cloud lidars, two microwave radiometers, and an infrared spectrometer. Radiosondes are also being launched twice each day. These measurements are providing a better understanding of the effect of clouds on the surface energy budget over Greenland. Many clouds throughout the year contain supercooled liquid water, which have a large impact on the energy budget. The annual average cloud radiative forcing (CRF) is positive, as are all of the monthly means. The positive CRF throughout the summer makes Summit different from other Arctic locations. Overall, the infrared cloud radiative effect (CRE) from individual clouds is larger at Summit than in other Arctic locations. The reason for this is that temperature and humidity control the CRE through competing influences between the mid- and far-infrared spectral regions. The low precipitable water vapor over the high-altitude Greenland plateau results in the increased CRE. At constant relative humidity, CRE is approximately constant for temperatures characteristic of the Arctic. This result also has implications for understanding recent and future changes across the Arctic due to climate change.