# Presentation: 185947

## A review of 2005-06 Extreme Events

- Background and variables used
- Extreme sea surface temperatures
- Focus on 850 mb temperature anomalies
- also Dartmouth Flood Monitor
- 1968-2006 and Oct 2005-Sept 2006
- > 2 sigma anoms; < -2 sigma anoms
- Northern Hemisphere time series of % area
- Global map of % days with extreme temps
- Extreme cases (1998, 2002, 2003, 2005, 2006)
- Speculation on Synoptics
- USA monthly temp and precip xtremes

- Special thanks to: Cathy Smith, Don Hooper, Klaus Wolter, Alex McColl, Barry McInnes

*Klaus Weickmann, ESRL/PSD*

## L

- H

- H

- H

- H

- May-Sep 1998, 2002, 2003, 2005,
- 2006 composites on right

- SSTA

- OLRA

- 200uv

## Temperature 850 hPa

- Annual mean
- standard deviation
- 1968-2006

- Annual mean
- 1968-2006

- Note: full seasonal cycle of
- standard deviation used in
- analysis that follows

## <  -2 σ

- % area 20-90N

- <  -2 σ

- > +2 σ

- Pinatubo

- ‘82-83

- ~Jan ‘77

- ‘98

- ‘02

- ‘03

- ‘05

- ‘06

- 850 temperature Oct ’68 – Sep ’06
- 91-day running mean

- Mean
- 2.46%
- 2.06%

## % days <  -2 σ

- % days <  -2 σ

- % days > +2 σ

**Oct 1968 to**
** ****Sep 2006**

- Shading:
- 2-4%, 4-6%, >6%

- orography not
- “blocked out”

## <  -2 σ

- % area 20-90N

- <  -2 σ

- > +2 σ

- 850 temperature Oct ’05 – Sep ’06
- daily plus 91-day running mean

- 11 Jul
- 2%

- 21 Jul
- 8.7%

**11 Sep**

**15-16 Aug**

## Oct 1968 to

**Oct 1968 to**
** ****Sep 2006**

- 850 mb temperature
- anomalies (degrees C)
- Shading:
- 0.5-1.0, 1.0-2.0, 2.0-3.0

- 3.5C!

- 850 mb temperature
- normalized anomalies
- Shading:
- 0.5-1.0, 1.0-1.5

## % days <  -2 σ

- % days <  -2 σ

- % days > +2 σ

**Oct 2005 to**
** ****Sep 2006**

- Shading:
- 5-10%, 10-15%, >15%

- orography not
- “blocked out”

## <  -2 σ

- % area 20-90N

- <  -2 σ

- > +2 σ

- Pinatubo

- ‘82-83

- ~Jan ‘77

- ‘98

- ‘02

- ‘03

- ‘05

- ‘06

- 850 temperature Oct ’68 – Sep ’06
- 91-day running mean

- Mean
- 2.46%
- 2.06%

## Jun 13 – Sep 11, 1998

- May 20 – Aug 18, 2002

- Aug 3 – Nov 3, 2003

- Jul 14 – Oct 3, 2005

- Jul 12 – Oct 10, 2006

- Percent of days out of 91 with
- 850 hPa normalized temperature
- anomalies greater than +2 sigma
- Shading levels
- 8-16%, 16-32%, 32-48%, >48%

## Daily dates with maxima in % area > +2 sigma during Jul 12 – Oct 10 2006

- Daily dates with maxima in % area > +2 sigma during Jul 12 – Oct 10 2006

- USA west coast
- heat wave

## Slide 12

## Slide 13

## Slide 14

## Slide 15

## Speculation on Synoptics

**Speculation on Synoptics**
- Two areas of tropical forcing
- due to extreme SSTs in warm
- pool region
- MJO-like behavior: faster time
- scale and consolidation of
- anomalies, esp. summer/fall?
- Leads to more transient “split
- flows” with stronger westerly
- winds in tropics & subtropics
- Favors extreme ridging events
- and subtropical jets spiraling
- into mid-latitudes
- Reflecting increased heat
- transport due warm tropical
- SSTs?

## Summary and Conclusions

- Expanded > 29C SSTs in warm pool region, especially since July 2001
- 2005-06 continues recent string of extreme temperatures during summer/fall, and more general trend of increasing warm extremes
- > 2 sigma more often, over larger area and especially at warm time of year
- Synoptic discussion of Nov-Dec 2005 (USA west coast precip), April 2006 (CA precip) and June 2006 (USA east coast precip) extreme events @ http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html

## Slide 18

## Possible impact of assimilation

- model errors on results?