Temperature Inversions in Temperature Inversions in Colorado Colorado –– What are they What are they and What do they mean?and What do they mean?

Nolan J. Doesken, State ClimatologistNolan J. Doesken, State ClimatologistColorado Climate CenterColorado Climate Center

presented to Rocky Mountain Agribusiness Association 55presented to Rocky Mountain Agribusiness Association 55thth Annual Annual Convention and Trade Show, Denver, CO on January 9, 2007Convention and Trade Show, Denver, CO on January 9, 2007

Prepared by Odie BlissPrepared by Odie Bliss

http://http://ccc.atmos.colostate.educcc.atmos.colostate.edu

The air near the surface is heated The air near the surface is heated by energy from the sun.by energy from the sun.

Typical Typical afternoon afternoon conditionsconditions

Temperature

Height

When the sun goes down, the air When the sun goes down, the air near the surface may cool quickly, near the surface may cool quickly, especially when the air is clear and especially when the air is clear and

the humidity is low.the humidity is low.

InversionInversionconditionsconditions

Temperature

Height

InversionsInversions

• Air temperature typically is cooler as you go away from the surface.

• When the air temperature is warmer aloft –inversion

• Stability – will the air mix or not?

Inversion conditionsInversion conditions• Clear skies• Calm winds• Dew or frost• Smoke not rising• Dust hanging over a road• Often form in low areas• Winter a regular feature

StabilityStability

• Stability conditions affect the dispersion of spray by the wind

StabilityStability

3 categories• Unstable (air cools with height)• Neutral• Stable (air rises with height)

There are many situations that There are many situations that cause cause ““inversionsinversions”” in the in the

atmosphere, but the ones that atmosphere, but the ones that affect agricultural spraying the affect agricultural spraying the most are surface inversions most are surface inversions ––

air that is coldest near the air that is coldest near the ground and warms with height ground and warms with height for dozens to hundreds of feet.for dozens to hundreds of feet.

The climate and topography of The climate and topography of Colorado are very conducive to Colorado are very conducive to the formation of inversions. This the formation of inversions. This

is especially true in large is especially true in large mountain valleys such as the mountain valleys such as the San Luis Valley, and in most San Luis Valley, and in most river valleys where many of river valleys where many of ColoradoColorado’’s crops are grown.s crops are grown.

Colorado Average Annual PrecipitationColorado Average Annual Precipitation

The Life-Cycle of a Surface Temperature Inversion.

Typical Typical summer summer

day day progressionprogression

Temperature

Height

3 PM8 AM &

7 PM

Midnight

NonNon--InversionInversion

InversionInversionconditioncondition

In Colorado, balloons are launched In Colorado, balloons are launched twice daily at Denver and Grand twice daily at Denver and Grand Junction. These data are publicly Junction. These data are publicly

available online.available online.

• http://www.rap.ucar.edu/weather

But you donBut you don’’t need weather t need weather balloons to detect inversions.balloons to detect inversions.

Knowing local wind patterns is also Knowing local wind patterns is also key to understanding inversions.key to understanding inversions.

Average Wind Speed (mph) by Hour for July 2001

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

Win

d Sp

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(mph

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Alamosa Denver Grand Junction

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Example Example CoCoRaHSCoCoRaHS Map, July 9, 2006Map, July 9, 2006

Colorado Climate CenterColorado Climate CenterColorado State UniversityColorado State University

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