Response of Cloud Cover to Changes in Sea Ice
Clouds play a major role in the arctic surface energy balance controlling the growth and melt of sea ice. At the same time the processes involved in the formation, maintenance and dissipation of cloud cover over the Arctic Ocean are thought to be strongly influenced by the sea ice itself. The proposed project will advance the understanding of this interaction and feedback by asking: What is the response of Arctic clouds to diminishing sea ice? In answering this question, we will consider (i) the physical processes that cause and modulate this response, (ii) the role of large-scale atmospheric dynamics, (iii) the potential effects on the heat and energy balance and in climate feedbacks, and (iv) the limitations of observing from space the response of clouds to changes in sea ice. Our approach will be to conduct a series of experiments with different configurations of a regional atmospheric model, the Weather Research and Forecast (WRF) model. Focusing on the autumn season, sea ice and sea surface temperature will be altered and changes in cloud cover associated with sea ice will be examined in the context of large scale dynamics. Model experiments designed to better understand the physical processes involved in the response of clouds to diminishing sea ice will be performed. The impact on the surface and the top of the atmosphere energy balance of sea-ice driven changes on cloud cover and the atmospheric temperature and humidity will be examined. Differences in sea ice-cloud interactions between the WRF model and a typical global climate model (e.g. CAM) will be assessed. Finally, we will assess the ability of satellite cloud detection criteria used in typical visible and infrared-based algorithms to properly detect cloud changes in the context of significant changes in surface properties by performing radiative transfer calculations to simulate the spectral signal at the satellite from modeled atmospheric and cloud responses for different surface conditions . The proposed research addresses significant questions of the “Understanding Change” aspect of the Study of Arctic Environmental Change (SEARCH). In particular the questions/activities “What are the critical interactions among ocean, ice, land, and atmosphere as they relate to Arctic Change?”, “What is the direction and relative importance of feedbacks?” will benefit from the proposed project.
Total cloud fraction for October 1, 2007 after one day of integration for a) median sea ice concentration,
b) actual sea ice concentrations (observed), and c) difference between them (observed-ice – median-ice). The ice
edge location is shown in green and magenta for median-ice and observed-ice ice cases respectively. Sea level
pressure contours (4-hPa interval) are shown in a) and b), contour tickmarks indicate direction of decreasing
pressure. Sea level pressure differences are overlaid in c) with an interval of 2 hPa and show no substantial
difference in this case. Inset in c) shows area of maps.