Extremes

Project Overview

Motivation:

• • Extreme events have the greatest impacts on the economy and safety

  • Understanding how events have changed over time is necessary to better predict future changes

  • Documenting the atmospheric drivers is also needed to improve prediction of extremes

Methods:

• • Analyze daily and monthly temperature and precipitation extreme events

  • Daily extremes derived from key Alaska stations, monthly from climate divisions

  • Top (or bottom) 10 ranking each season used to define "extreme"

Key Findings:

• • Trends in monthly and daily extremes have a lot of similarity over the periods of record

    • Recent increase in extreme warm events decrease in cold

    • Mixed or no trend in precipitation events

    • PDO-like variability in temperature extremes (especially cold)

  • Trends in extremes not linked with a change in overall variance

  • Most extremes driven by temperature advection (or lack thereof) depending on the season

  • Circulation patterns with winter extremes are more prominent/consistent than summer

  • Similarities between monthly and daily extreme circulations: persistence during the month is likely key to this

Map of Alaska climate divisions and stations used in our analysis.

Composite sea level pressure anomalies the December-February top 10 highest (left) daily Tmax and (right) monthly divisional temperatures for Fairbanks. The units of the pressure anomalies are hPa. Anomalies significant at the 95% or greater level are shown by cross-hatching. Reds (blues) indicate positive (negative) anomalies.

Decadal counts of the top 10 most extreme monthly (a) high temperature, (b) low temperature, and (c) high-precipitation events stratified by season for all climate divisions.