Chukchi/Beaufort Seas Surface Wind Climatology, Variability, and Extremes from Reanalysis Data: 1979-

2009

Xiangdong Zhang, Jeremy Krieger, Paula Moreira, and Soumik BasuIARC and ARSC, University of Alaska Fairbanks

Jing Zhang, and Steve StegallNOAA-ISET Center, North Carolina A&T State University

Martha ShulskiHigh Plains Regional Climate Center, University of Nebraska-Lincoln

Outlines

• Large scale control

• Synoptic and mesoscale features beyond the large-scale control

• Regional data analysis results

~ 20-25% of variance provide background information to mesoscale model

rapid changes in wind speed and direction

Dynamic control of the large-scale surface wind

Aleutian low

Beaufort high

Icelandic low

Siberian high

Large-scale modulation:Beaufort high intensifies/weakens, and shifts with AO fluctuation.

Arctic Oscillation shows a large fluctuations and an upward trend from 1970s to 90s.

Thompson and Wallace (1998)

Positive AO Negative AO

Dynamic control of the large-scale surface wind

Xiangdong Zhang et al. (2003)

Differences of Surface Air Temperature and Wind Stress Between Positive and Negative AO

Dynamic control of the large-scale surface wind

Differences of Sea Ice Properties Between Positive and Negative AO

Concentration and Velocity Thickness

Zhang et al. (2003)

Arctic Oscillation largely impacts sea ice and ocean

• Arctic Rapid change Pattern (ARP)

ARP

Atmospheric circulation pattern has shifted (climate systems became more unstable)

Dynamic control of surface wind has changed

• Swift phase change of ARP accelerated climate change and resulted in the extreme event of sea ice cover loss in summer 2007

ARP Index (All Months Included)

The ARP associated atmospheric and oceanic heat transport reduced sea ice and enlarged open water

• Extreme sea ice loss in summer 2007 is a result of multiyear polarity and swift phase change of ARP, not a single-time, random event

The previously warmed ocean retains the decreased sea iceThe enlarged open water enhance albedo feedback

The ARP phase change reversed wind pattern and reduced sea ice coverThe ARP phase change enhanced Pacific warm air and warm water inflowThe enlarged open water enhance albedo feedback

Wind has tremendous local features beyond large-scaleDynamic control

Single synoptic weather system can brings large impact on ocean and sea ice

Wind has tremendous local features beyond large-scaleDynamic control

Large differences can occur in difference locations no matter how close they are

Wind has tremendous local features beyond large-scaleDynamic control

Large differences can occur in difference locations no matter how close they are

• Data: North American Regional Reanalysis (NARR) from 1979-2009 with 32 km grid spacing, and 8 times daily.

• Parameters to be analyzed:

1. Climatology of wind speeds;

2. Climatology of 95th percentile wind;

3. Climatology of wind directions.

Regional analysis of wind field

• Obvious seasonality over the Beaufort/Chukchi seas;

• Minimum wind speeds occur in May;

•Maximum wind speeds occur in September and October (~7-8 m/s or greater).

Monthly climatology of wind speeds

• Similar seasonality to the averaged wind speeds;

• Minimum wind speeds occur in May;

•Maximum wind speeds occur in September and October (~14-15 m/s or greater).

Monthly climatology of 95th percentile of wind speeds

• Obvious seasonality over the Beaufort/Chukchi seas;

• The largest variance occur in October.

Monthly climatology of wind speed variances

• Obvious seasonality over the Beaufort/Chukchi seas;

• The largest variance occur in October.

Monthly climatology of 95th percentile wind speed variances

• NE wind dominates over the Beaufort/Chukchi seas;

• The largest frequency occurs in winter and spring (larger than 60%).

Monthly climatology of frequency of NE wind

• SE wind mainly occurs over the northwest Beaufort Sea and Chukchi Sea;

• The largest frequency occurs in early summer.

Monthly climatology of frequency of SE wind

• SW wind mainly occurs over the north Beaufort Sea and Canada Basin;

• The largest frequency occurs in late summer.

Monthly climatology of frequency of SW wind

• NW wind mainly occurs over the north of the Canadian Archipelago, and Siberian coast of the Chukchi Sea;

• The largest frequency occurs in winter (over 60%).

Monthly climatology of frequency of NW wind

• NW wind mainly occurs over the north of the Canadian Archipelago, and Siberian coast of the Chukchi Sea;

• The largest frequency occurs in winter (over 60%).

Monthly climatology of frequency of NW wind

• Wind speed generally has increased in the Beaufort and Chukchi seas throughout most of the year;

• The largest increase has occurred in September and October (90% significant level in the hatching area).

Linear trends of wind speeds

• Similarly, wind speed generally has increased in the Beaufort and Chukchi seas throughout most of the year;

• The largest increase has occurred in September and October (90% significant level in the hatching area).

Linear trends of the 95th percentile wind speeds

• The wind speed had large fluctuations year by year in the Beaufort and Chukchi seas;

• The largest increase has occurred from July to October.

Linear trends of wind speed time series

• Similarly, the wind speed considerably fluctuated in the Beaufort and Chukchi seas throughout the year;

• The largest increase has occurred from July to October.

Linear trends of the 95th percentile wind speed time series

• Strong seasonality occurs for the diurnal cycle of wind speeds;

• Wind speeds have larger diurnal cycle in March and April over ocean, and from April through September over land.

Diurnal cycle of surface wind speeds

JAMSTEC ship, 2009

Extreme/strong wind event induced by intense mesoscale system

• Atmospheric circulation plays a dynamic controlling role in surface wind variability and changes;

• Surface wind has strong local and mesoscale features beyond the large-scale circulation control;

• The monthly averaged and the 95th percentile of 8 hourly surface wind speeds present a large seasonality with a minimum in May and a maximum in September and October;

• The monthly averaged and the 95th percentile of 8 hourly surface wind speeds has considerable increased in September and October during the last 30 years;

• Wind speeds show clear diurnal cycle in March and April over ocean and from April through September over land.

Summary