Atmospheric and cloud conditions over Barrow, Alaska and Eureka, Canada

Due to the rapid recession of Arctic summertime sea ice, there is considerable interest in the atmospheric conditions across the Arctic Basin. Surface-based measurements made at Barrow, Alaska (71 N, 156 W) and the Canadian Network for the Detection of Arctic Change (CANDAC) site at Eureka, Canada (80 N, 86 W) are used to examine atmospheric variables, including cloud conditions. Data from radiosondes, microwave radiometers, and Atmospheric Emitted Radiance Interferometers (AERIs) are used to examine the temporal variability of the temperature structure (surface, troposphere, near-surface inversion), total column water vapor, cloud cover, and longwave cloud radiative forcing (LWCRF) at both sites. The seasonal cycles of the meteorological and cloud conditions at Barrow and Eureka are compared. Recent radiosonde temperature data are put in the context of long-term trends from data sets that originated in the late 1940s at Barrow and the late 1960s at Eureka. Temporal changes in LWCRF over the past decade are examined at Barrow. The spatial variability of LWCRF between Barrow and Eureka is investigated over the past three years, when the AERI measurements were available from both sites. The particular causes of changes in the downwelling longwave flux are examined, with particular attention to recent changes in summer conditions.