Wind Field Climatology, Changes, and Extremes in the Chukchi–Beaufort Seas and Alaska North Slope during 1979–2009

Abstract

ind field climatology, changes, and extremes at ~32-km resolution were analyzed for the Chukchi?Beaufort Seas and Alaska North Slope region using 3-hourly North American Regional Reanalysis (NARR) from 1979 to 2009. The monthly average wind speeds show a clear seasonal cycle with a minimum of 2?4 m s?1 in May and a maximum up to 9 m s?1 in October. The 95th percentile winds show a similar seasonality with a maximum up to 15 m s?1 in October. The 31-yr domain averaged 3-hourly wind speeds display a clear diurnal cycle over land and sea ice areas during the warm seasons. Weaker radiation during winter and larger heat capacity over open water reduce the diurnal signal in the wind field diurnal variations. There were increasing trends of areal averaged monthly mean and 95th percentile wind speeds for July through November. The strongest increase in the areal averaged 95th percentile wind speeds occurred in October from 7 m s?1 in 1979 to 10.5 m s?1 in 2009. The frequency of extreme wind events (speed above the 95th percentile winds) shows an increasing trend in all months, with the greatest increase occurring in October, showing 8% more extreme wind events in 2009 comparing to 1979. The prevailing wind direction was northeast with a frequency of 40%?60% for most of the year. The frequency for southwest and northwest winds was small (<20%) except for two anomalous areas along the Brooks Range in Alaska and the Chukotka Mountains in easternmost Russia where the frequency has increased to 35%?50% during the cold season months.