Atmospheric Variability

Why is it so cold winter 2010-2011? Why was it so hot summer 2010? Why was it so dry in 2007? Why was it so wet in 1998, 2009 (fall)? Are these extremes becoming more

common? Why or why not? Does variability in atmospheric flow patterns

fully answer these questions?

Atmospheric Variability

Temporal weekly, monthly, seasonal, annual, decadal

Spatial (x,y) Global, synoptic, regional, mesoscale,

microscale, sub-micro Vertical (z)

Surface, 1000mb, 925, 850, 700, 500, 300 Trends?

Natural or anomalous

What is a teleconnection

AMS: 1. A linkage between weather changes occurring in widely

separated regions of the globe. 2. A significant positive or negative correlation in the fluctuations of a field at widely separated points. Most commonly applied to variability on monthly and longer timescales, the name refers to the fact that such correlations suggest that information is propagating between the distant points through the atmosphere.”

Pressure fluctuations SST Height anomalies (700, 500mb) Associations with circulation indices

The North Atlantic Oscillation (NAO)

Pressure dipole in North Atlantic centered near Iceland/Greenland and over the Azores Icelandic Low vs Azores High Tendency for either both weak or both strong

Dominant mode of Variability in Atlantic Winter

The NAO index is obtained by projecting the NAO loading pattern to the daily anomaly 500 millibar height field over 0-90°N. The NAO loading pattern has been chosen as the first mode of a Rotated Empirical Orthogonal Function (EOF) analysis using monthly mean 500 millibar height anomaly data from 1950 to 2000 over 0-90°N latitude. (NCDC)

The North Atlantic Oscillation

Dec – March Temp correlations

Dec – March Precip correlations

The North Atlantic Oscillation

38.0

43.0

48.0

53.0

58.0

1949

1954

1959

1964

1969

1974

1979

1984

1989

1994

1999

2004

2009

Bama state averaged temp Dec-Feb

Arctic Oscillation (AO) or NHam

Cyclonic circulation of upper level winds around the Arctic Latitude poleward of 55°N

Positive = stronger winds- confines Arctic air More zonal

Negative = relaxed winds- Arctic air oozes southward

AO index is obtained by projecting the AO loading pattern to the

daily anomaly 1000 millibar height field over 20°N-90°N latitude

Winter AO

38.0

43.0

48.0

53.0

58.0

1949

1954

1959

1964

1969

1974

1979

1984

1989

1994

1999

2004

2009

Bama state averaged temp Dec-Feb

Current Phase

Pacific North American (PNA)

Quadripole pattern of 500mb height anomalies All months except June and July

winter Center locations

Similar signs south of Aleutians and over SE U.S. Hawaii and InterMountain U.S. and Canada

The PNA index is obtained by projecting the PNA loading pattern to the daily anomaly 500 millibar height field over 0-90°N. The PNA loading pattern has been chosen as the second mode of a Rotated EOF analysis using monthly mean 500 millibar height anomaly data from 1950 to 2000 over 0-90°N latitude.

PNA

38.0

43.0

48.0

53.0

58.0

1949

1954

1959

1964

1969

1974

1979

1984

1989

1994

1999

2004

2009

Bama state averaged temp Dec-Feb

Current Phase PNA

El Nino Southern Oscillation (ENSO)

Both a SST and pressure fluctuation in the tropical Pacific

~ 5-7 year periodicity Most significant atmospheric/oceanic coupling

in the world El Nino = warmer than normal SST La Nina = colder than normal SST Southern oscillation= pressure flip-flop

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstanim.shtml

Southern Oscillation Index (SOI)

Standardized difference in MSLP between Darwin Australia and Tahiti (T-D)

Pressure normally higher over Tahiti and lower over Darwin Slow east to west flow of tropical water

Nino Regions

Oceanic Nino Index

Running mean of the Nino 3.4 region At least 5 consecutive

overlapping months above (below) 0.5°C sst anomaly

Weak Mod Strong Weak Mod Strong1951 1986 1957 1950 1954 19551963 1987 1965 1956 1964 19731968 1994 1972 1962 1970 19751969 2002 1982 1967 1998 19881976 1991 1971 19991977 1997 1974 20072004 2009 1984 20102006 1995

2000

El Niño La Niña

ENSO Impacts

Alabama Impacts

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

Projected ENSO November 2012 – April 2014

Time BELOW NORMAL ABOVE BELOW NORMAL ABOVE DEG ANOMALYNDJ 0 1 0 0 1 0 26.62 0.05DJ F 0.013 0.987 0 0.019 0.979 0.001 26.47 -0.16J FM 0.15 0.84 0.011 0.109 0.877 0.014 26.65 -0.18FMA 0.202 0.751 0.047 0.088 0.894 0.018 27.13 -0.12MAM 0.282 0.601 0.117 0.112 0.855 0.033 27.52 -0.1AMJ 0.352 0.444 0.204 0.178 0.738 0.085 27.67 -0.1MJ J 0.362 0.39 0.248 0.226 0.63 0.144 27.49 -0.09J J A 0.355 0.382 0.264 0.258 0.56 0.183 27.16 -0.08J AS 0.343 0.389 0.268 0.267 0.531 0.202 26.87 -0.07ASO 0.472 0.356 0.171 0.423 0.43 0.147 26.4 -0.35SON 0.432 0.354 0.214 0.414 0.385 0.201 26.4 -0.29OND 0.413 0.351 0.235 0.421 0.335 0.244 26.35 -0.28NDJ 0.497 0.328 0.175 0.514 0.297 0.189 26.03 -0.54DJ F 0.535 0.317 0.148 0.541 0.302 0.158 26.02 -0.61J FM 0.547 0.313 0.14 0.524 0.343 0.133 26.27 -0.56FMA 0.55 0.317 0.134 0.469 0.436 0.096 26.81 -0.44

Discovered 1996 (Hare and Mantua) Leading principal component of Northern

Pacific SST variability Similar to ENSO

Long-lived ENSO Greater SST variability in mid latitiude Pacific

Pacific Decadal Oscillation (PDO)

Pacific Decadal Oscillation (PDO)

Positive Negative

El Nino vs positive PDO

Table 1: summary of North American climate anomalies associated with extreme phases of the PDO.

climate anomalies Warm Phase PDO Cool Phase PDO

Ocean surface temperatures in the northeastern and tropical Pacific

Above average Below average

October-March northwestern North American air temperatures

Above average Below average

October-March Southeastern US air temperatures

Below average Above average

October-March southern US/Northern Mexico precipitation

Above average Below average

October-March Northwestern North America and Great Lakes precipitation

Below average Above average

Northwestern North American spring time snow pack

Below average Above average

Winter and spring time flood risk in the Pacific Northwest

Below average Above average

Atlantic Multidecadal Oscillation (AMO) Fluctuation in detrended SST in north Atlantic (0 –

70°N) AMO index 10 year running mean

Relationships to speed of thermohaline circulation

Thermohaline Circulation

AMO and hurricane activity

AMO and hurricane activity

PDO and AMO drought

Quasi Biennial Oscillation (QBO)

Oscillating (E-W) stratospheric winds 10 – 100 mb above the equator

20 – 36 month periodicity Impacts

Spike in ATL hurricane activity during west (positive) zonal flow

May impact Asian monsoon and ENSO

Quasi Biennial Oscillation (QBO)

Madden Julian Oscillation

30 – 60 day oscillation, Tropical Indo-Pacific Eastward wave propagation of anomlaous rainfall low

OLR 4-8 m/s

Impacts trop and subtrop, precip, temp, and circulation

Most prominent NH winter U.S. Impacts

Increase frequency/intensity west coast precip Eastern cold air outbreaks

http://web.archive.org/web/20070612204448/http://www.apsru.gov.au/mjo/index.asp

Madden Julian Oscillation

MJO- OLR and pressure

MJO Phase Diagram

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Precipitation/

MJO and Atlantic Hurricanes

Phase 1 and 2 support a more active regime of Atlantic convection ACE > 76 91.5 major hurricane days (1974 – 2007)

Phase 6 and 7 less active ACE < 36 20.5 major hurricane days (1974 – 2007)

Others not discussed

ESRL Indices http://www.esrl.noaa.gov/psd/data/

climateindices/list/

Climate Prediction Center http://www.cpc.ncep.noaa.gov/