CHARACTERIZING COLD AIR POOL DYNAMICS USING THERMAL IMAGERY

PRESENTED BY CHRIS JOHNSON

BIOMICROMETEOROLOGY GROUP

Photo Credit: The University of Utah

DESIGN OF EXPERIMENT

SODAR

THERMAL IMAGERY TO MAP COLD AIR POOL DYNAMICS

Each pixel of temperature information will be associated with a position on the Earth and an elevation.

But first the thermal imagery must be filtered, georeferenced, and orthorectified.

GEOREFERENCING THERMAL IMAGERY

• Identify objects in the image

• Obtain accurate locations

• Use known objects as Ground Control Points Ground Control Point

Known Object and Location

ORTHORECTIFICATION

Data Gap

VALIDATION – Temperature ProfileBasic Functions:• Emits a sound pulse• Measures properties of sound backscattered

from turbulent fluctuations• Emitted pulse frequency• Backscattered sound frequency• Intensity of backscattered sound

Relationship to IR Measurements:• Atmospheric Structure Parameters

• Refractive Index Structure Parameter(CN

2)• Temperature Structure Parameter

(CT2)

• Intensity related to CN2

• CN2 related to CT

2

• CT2 directly calculated from

temperature gradient

VALIDATION – Cold Air Pool Depth

Plot Credit: Beyrich, F., 1997. Mixing Height Estimation from SODAR Data. Atmospheric Environment 31, 3941-3953.

Assumption:

The depth of the cold air pool is equal to the inversion height.

ABL Conditions for Plot:

Weak wind, surface radiatively cooling.

Potential Temperature

Backscatter Intensity

DESIGN OF EXPERIMENT

SODAR