Climatology of extreme winds in the Chukchi/Beaufort Seas during 1979–2009

The high-resolution (32km, 3-hourly) North American Regional Reanalysis (NARR) was used to examine the detailed structures of the distribution and evolution of the surface winds across the Chukchi/Beaufort Seas/Alaska region during the 31-year period 1979–2009. The wind direction climatology analyses show that the prevailing wind direction in the study area is northeast with a frequency of 40–60% for nearly all months. The frequency for southwest wind is small (<20%), except for an anomalous area along the Brooks Range where the frequency is 35–50% during the cold winter season. The combination of the extremely stable boundary layer and thermal wind effects probably cause these mesoscale features in the wind direction climatology.

The monthly average wind speeds in the study area show a clear seasonal cycle, with a minimum of 2.5–4 m/s in May and a maximum of 4–9 m/s in October. The maximum and 95th percentile wind speeds show a similar seasonality—strong winds in fall and calm winds in spring. The maximum 95th percentile wind speeds during fall are 9–15 m/s. Monthly wind speeds during 1979–2009 show a positive trend during the warm season, while sea ice extent in the study area shows a negative trend. As a result, a negative correlation between sea ice extent and wind speed occurs for the months when there is an increase in wind speed. The frequency of extreme wind events (wind speed above the 95th percentile) also shows an obvious increasing trend, particularly in September and October.