An intro to Arizona weather
and climate
Mike Crimmins
Extension Specialist – Climate Science
Dept. of Soil, Water, & Env. Science &
Arizona Cooperative Extension
The University of Arizona
Presentation Overview
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•
•
•
The global climate system
Meteorology 101
Controls on Arizona climate
Climate variability and Change
Global Energy Balance
From http://www.bom.gov.au
Annual Cycle
Global Circulations
Atmosphere
Ocean
From http://www.bom.gov.au
Global Circulations
Meteorology 101
Weather Circulation Features
• Low Pressure System
– Rising air
– Counter-clockwise circulation
– Can produce precipitation if moisture is
available
L
• Jet Stream
– High winds at ~30,000 ft between
cold/warm air
– Provides energy for low pressure
systems; helps steer storms (storm
track)
• High Pressure System
– Sinking air
– Clockwise circulation
– Typically associated with dry conditions
H
Jet Streams
L
H
http://rst.gsfc.nasa.gov
Fronts
http://www.ux1.eiu.edu/~cfjps/1400/fronts.html
Fronts
http://earth.usc.edu/~stott/Catalina/images/weatherimages.jpg/ninefour.jpg
http://virga.sfsu.edu/gif/jetstream_init_00.gi
f
What does it take to produce
precipitation?
Vertical Atmospheric
Motion
Atmospheric Moisture
(water vapor)
Precipitation
Temperature decrease with height
• All weather occurs in
troposphere
• Temperature decreases
with height on average
~3.5 °F/1000 ft. (mean
environmental lapse rate)
• Can you spot the
tropopause in the photo?
Where does atmospheric moisture
come from?
• Moisture Advection:
Water evaporates into Maritime
Continental
atmosphere over ocean Airmass
Airmass
areas and moves over
continental areas
• Moisture Recycling:
Precipitation initially from
advection re-enters
atmosphere from
Wet soil/active vegetation = ET
evapotranspiration
Lifting Mechanisms
1. Convection: Intense
heating at surface
cause buoyancy
2. Orographic Lifting:
Air is forced up and
over physical barrier
3. Frontal Lifting: Air
masses of different
temperature/moisture
levels force vertical
motion
http://www.angliacampus.com/public/pri/geog/rivers/page04a.htm
Last step…precipitation
processes
Warm Clouds
(tropical areas)
Cold Clouds
(everywhere else)
Background on AZ Climate
Annual Average Arizona Temperatures
Annual Average Arizona Precipitation
Arizona Climograph
2.5
100
80
1.5
60
1
40
0.5
20
temp (F)
precip (in.)
2
0
0
jan
feb
mar
apr
may
jun
Precip (in.)
jul
aug
Temp (F)
sep
oct
nov
dec
Climate Quiz
San Francisco,CA
5
70
60
50
3
40
2
30
60
50
3
40
30
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Temp (F)
6
Precip (in)
Globe, AZ
Temp (F)
6
90
C
10
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Precip (in)
20
1
0
80
5
90
Atlanta, GA
D
4
3
40
2
30
20
1
10
0
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Precip (in)
Temp (F)
inches
50
deg F
60
80
70
70
4
80
70
2
10
0
inches
Minneapolis, MN
20
1
5
B
4
inches
4
inches
80
90
deg F
A
6
deg F
5
90
60
50
3
40
2
30
20
1
10
0
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Precip (in)
Temp (F)
deg F
6
3 in.
Jan
Dec
Seasonal
Distribution of
Precipitation
•More winter precip in
northern AZ
•Stronger monsoon
signal in southeast AZ
(more summer precip)
(graphic from Sheppard, et al.
2000)
Mean Annual Annual Avg.
Temp (F)
Precip (in.)
Annual Average
Arizona Potential
Evapotranspiration
http://southwest.library.arizona.edu/
Arid-zona: Seasonality and aridity
How has Maricopa County
climate varied over time?
Annual
Precipitation
and
Temperature
(departures
from average)
Seasonal
Temperatures
(departure from
average)
Seasonal Precipitation 
Drought
Atmospheric Controls on
Arizona Climate
Atmospheric Circulation and
Arizona Climate
• Large-scale circulation
patterns are an important
determinant of local climate
• Arizona has a unique
geographic position in
northern hemisphere
• Circulation patterns are tied to
global ocean sea surface
temperatures
• Patterns can persist for years
and even decades
http://www.geography.hunter.cuny.edu/~tbw/wc.notes/7.circ.atm/animations/GlobalWind.html
Seasonality of Circulation
Patterns
Global Hydroclimate
Global Circulations and Aridity
Winter Circulation
Pattern
MOIST AIR
L
Shift of jet stream track towards Arizona
DRY AIR
H
Summer
Circulation Pattern
H
DRY AIR
H
Weak flow around expanded Bermuda sub-tropical
high-pressure system
MOIST AIR
Monsoon
circulation
H
Interannual Climate Variability
What are El Niño and La Niña?
Atmosphere-Ocean Coupling
Atmosphere-Ocean Coupling
Atmosphere-Ocean Coupling
Dominant Circulation Pattern: La Niña Winter
Dominant Circulation Pattern: El Niño Winter
Arizona ENSO Connection
2005
2001
2003
2004
2006
2007
2002
2000
1999
ENSO: 1982-2012
http://iri.columbia.edu/climate/ENSO
Average Jet stream winds (~30,000 ft) - January
L
H
http://www.esrl.noaa.gov/psd
Jet stream winds (~30,000 ft) – January 2011
H
L
http://www.esrl.noaa.gov/psd
North American Monsoon
Monsoon
Monsoon start dates for
Tucson
•Average start July 3rd
•Earliest start June 17 2000
•Latest start July 25 1987
Monsoon season rainfall
(June 15th to September
30th)
•Average monsoon season
rainfall 6.06”
•Driest monsoon season 1.59”
in 1924
•Wettest monsoon season
13.84” in 1964
Upper Level Flow - May
Upper Level Flow - June
Upper Level Flow - July
NE
westerly wind
NV
UT
CO
Four Corners
High Pressure
CA
KS
TX
CO. River Valley
Thermal Low
AZ
NM
Mid-level moisture
from Gulf of Mexico
TX
Low-level moisture
from Gulf of California
Core Monsoon Area
(abundant tropical moisture,
frequent
thunderstorm activity)
GULF OF
MEXICO
PACIFIC OCEAN
Conceptual diagram of key circulation features of the North American
Monsoon System
easterly wind
Mexico
Monsoon Precipitation across AZ
Total Monsoon Rainfall
JAS Percent of Annual
Rainfall
Triggers of Thunderstorm Events
• Gulf Surge
Adams and Comrie 1997
Triggers of Thunderstorm Events
• Upper level waves/vortices
Triggers of Thunderstorm Events
• Thunderstorm Outflows
http://www.wrh.noaa.gov/psr/pns/2011/July/DustStorm.php AZ DOT
Triggers of Thunderstorm Events
• Thunderstorm Outflows
Adams and Comrie 1997
Triggers of Thunderstorm Events
• Frontal Storms
NWS Flagstaff
Triggers of Thunderstorm Events
• Frontal Storms
NWS Flagstaff
Summer Severe Thunderstorm Patterns
in Arizona
From National Weather Service – Tucson
http://www.wrh.noaa.gov/twc/monsoon/monsoon_patterns.php
Monsoon Day in Tucson
• UofA Cloud Convection Experiment
Flash floods
• Flash Flood Watch: Conditions are favorable for flash
flooding over large or multiple areas of the region. These
are usually issued only when an especially active day is
expected. Watch weather reports and conditions closely.
• Urban and Small Stream Flood Advisory: Minor
flooding is expected or underway in low lying and flood
prone areas. While it may not be life threatening,
extreme caution is advised, particularly for motorists.
• Flash Flood Warning: Life-threatening, rapid flooding is
about to occur, or is already underway. Move to higher
ground now! It is particularly dangerous to be in a low
lying area or near a wash.
From National Weather Service – Phoenix
http://www.wrh.noaa.gov/psr/general/safety/index.php
Flash Floods:
Never drive
into a flooded
roadway!
FEMA
Fighting a Losing Battle
• Width: 5.5 feet
• Length: 14 feet
• Ground Clearance: 10
inches
• Weight: 3,400 pounds
However, 1 foot of water displaced by this vehicle weighs:
(5.5’ x 14’ x 1’ x 62.4 lbs./cu.ft.) = 4,805 pounds
From Steve Waters, Maricopa County Flood Control District
Severe Thunderstorms
• Severe Thunderstorm Watch: Conditions are favorable
for widespread thunderstorms with damaging winds and
even large hail to develop. These are usually issued only
when an especially active day is expected. Watch
weather reports and conditions closely.
• Severe Thunderstorm Warning: A thunderstorm with
damaging winds of 60 mph or greater is about to occur,
or is already underway. These winds could also produce
a dust storm with visibilities below 1/4 mile. Hail 1" in
diameter or larger is also possible.
• Dust Storm Warning: A dust storm, with visibilities of
1/4 mile or less, is about to strike, or has already
developed. Pull off the road now! Wind gusts between 40
and 60 mph are also likely.
From National Weather Service – Phoenix
http://www.wrh.noaa.gov/psr/general/safety/index.php
Lightning
http://www.jason.org/digital_library/110.aspx
Lightning Safety
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•
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Flash-to-bang of five seconds = 1 mile
Immediately get off elevated areas such as hills,
mountain ridges or peaks
SEEK: Seek clumps of shrubs or trees of
uniform height. Seek ditches, trenches or the
low ground. Seek a low, crouching position with
feet together with hands on ears to minimize
acoustic shock from thunder.
Immediately get out and away from ponds,
lakes and other bodies of water
Stay away from objects that conduct electricity
(barbed wire fences, power lines, windmills,
etc.)
A safe vehicle is any fully enclosed metal
topped vehicle such as a hard topped car,
minivan, bus, truck, etc
http://www.lightningsafety.noaa.gov/outdoors.htm
Bolt from the blue
Climate Change
What is causing climate change?
Carbon Dioxide, Methane, and
Nitrous Oxide are major GHGs
From http://www.climatechange.gc.ca
Global Temperature and Carbon
Dioxide
USGCRP 2009
Natural vs. Anthropogenic Forcings
Observed
Natural Only
Stott et al. (2000)
Temperature Projections
USGCRP 2009
Precipitation
Projections
USGCRP 2009
Interactions between
temperature and precipitation
• Confidence in
continuation of
increasing
temperatures
• Projections on
precipitation
variability are less
clear
• Increasing
temperatures alone
will increase aridity
Hoerling & Eischeid 2007
Closing Points
• Elevation, latitude, and ocean sea-surface
temperatures create a complex Arizona
climate
• Different mechanisms create summer
versus winter precipitation
• Lots of opportunity for variability (spatially
and temporally)
• Climate change is real and a reason for
concern in Arizona
Thanks!
crimmins@email.arizona.edu
http://cals.arizona.edu/climate