New ARM Campaign Studying the Lower Troposphere on Alaska’s North Slope


Perennial sea ice in the Arctic has declined more than 20% since the mid-1970s, raising concerns that a threshold in the net incoming versus outgoing radiation (albedo) feedback may have been crossed. Recent studies suggest that Arctic sea-ice retreats, depicted by the summer ice edge, are correlated closely to an upward trend in the downwelling, long-wave radiative flux in the Arctic. Increasing the downwelling long-wave flux appears to be driven mostly by increases in clouds and precipitable water vapor, establishing the need to better understand the contribution of clouds in this important feedback process.

The Arctic Lower Troposphere Observed Structure (ALTOS) campaign began on October 15th, conducting in situ cloud and aerosol measurements in the lower troposphere near Oliktok Point on the North Slope of Alaska. The principle observing system is a tethered balloon system with state-of-the art atmospheric, cloud microphysics, and aerosol sampling devices. ALTOS will provide support for testing Arctic cloud processes used in climate models and for testing algorithms used to retrieve these measurements. Data obtained during the campaign will provide a statistically significant set of observed in situ cloud properties for validating retrieval algorithms and will help scientists reduce the uncertainty in the radiative forcing and heating rates on hourly time scales. These data will also increase understanding of the driving processes that control climate changes and determine the state of the Arctic climate system.