Mike CrimminsExtension Specialist – Climate Science Dept. of Soil, Water, & Env. Science &

Arizona Cooperative ExtensionThe University of Arizona

Mike CrimminsExtension Specialist – Climate Science Dept. of Soil, Water, & Env. Science &

Arizona Cooperative ExtensionThe University of Arizona

An intro to Arizona weather and climate

An intro to Arizona weather and climate

Presentation Overview

• 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 CirculationsAtmosphere

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• 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

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Jet Streams

http://rst.gsfc.nasa.gov

HHLL

http://www.ux1.eiu.edu/~cfjps/1400/fronts.html

Fronts

http://earth.usc.edu/~stott/Catalina/images/weatherimages.jpg/ninefour.jpg

Fronts

http://virga.sfsu.edu/gif/jetstream_init_00.gif

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 atmosphere over ocean areas and moves over continental areas

• Moisture Recycling: Precipitation initially from advection re-enters atmosphere from evapotranspiration

MaritimeAirmass

ContinentalAirmass

Wet soil/active vegetation = ET

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

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Climate Quiz

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San Francisco,CA Minneapolis, MN

Globe, AZ Atlanta, GA

Seasonal Distribution of Precipitation

Mean AnnualPrecip (in.)

Annual Avg.Temp (F)

Jan Dec

3 in.

• More winter precip in northern AZ

• Stronger monsoon signal in southeast AZ (more summer precip)

(graphic from Sheppard, et al. 2000)

Annual Average Arizona Potential

Evapotranspirationhttp://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

Average Wintertime Mid-latitude Jet Stream Track

Shift of jet stream track towards Arizona

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DRY AIR

MOIST AIR

Winter Circulation Pattern

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Average summertime mid-latitude jet stream track

Monsooncirculation

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Weak flow around expanded Bermuda sub-tropicalhigh-pressure systemDRY AIR

MOIST AIR

Summer Circulation Pattern

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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

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ENSO: 1982-2012

http://iri.columbia.edu/climate/ENSO

Average Jet stream winds (~30,000 ft) - January

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http://www.esrl.noaa.gov/psd

Jet stream winds (~30,000 ft) – January 2011

HHLL

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

westerly wind

easterly wind

Four CornersHigh Pressure

CO. River ValleyThermal Low

Core Monsoon Area(abundant tropical moisture,

frequent thunderstorm activity)

Mid-level moisturefrom Gulf of Mexico

Low-level moisturefrom Gulf of California

PACIFIC OCEAN

Mexico

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GULF OFMEXICO

Conceptual diagram of key circulation features of the North American Monsoon System

Monsoon Precipitation across AZ

Total Monsoon Rainfall

JAS Percent of AnnualRainfall

Triggers of Thunderstorm Events

• Gulf Surge

Adams and Comrie 1997

Triggers of Thunderstorm Events

• Upper level waves/vortices

Triggers of Thunderstorm Events

• Thunderstorm Outflows

AZ DOThttp://www.wrh.noaa.gov/psr/pns/2011/July/DustStorm.php

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 – Tucsonhttp://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 – Phoenixhttp://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 – Phoenixhttp://www.wrh.noaa.gov/psr/general/safety/index.php

Lightning

http://www.jason.org/digital_library/110.aspx

Lightning Safety• 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

From http://www.climatechange.gc.ca

Carbon Dioxide, Methane, and Nitrous Oxide are major GHGs

What is causing climate change?

Global Temperature and Carbon Dioxide

USGCRP 2009

Stott et al. (2000)

Natural Only

Observed

Natural vs. Anthropogenic Forcings

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.eduhttp://cals.arizona.edu/climate