Effects of Humidity on Atmospheric Transmission in the Thermal Region

Effects of Humidity on Atmospheric Transmission in

the Thermal Region

What is the Problem?

• Sponsored by (Herb Mitchell) describes the problem– Atmospheric Transmission Anomaly Observed

• Scenario:– Remote Sensing Experiment

• Multiple airborne sensors collecting coincidently– Visible and Longwave Imagery (spectral)

• Decision made to collect imagery– Based on observation of clear sky condition

• Resulting Thermal Imagery with regions of low transmission

• Data Not Useful (Avoid in the future)

What are the clues and conditions?

• Experiment was collected in high humidity conditions

• Observed over land and water scenes

• Degraded Transmission across LWIR region (8-14 um)

• Rarely occurring event

The Hypothesis

• High concentration of aerosols < 200 [nm] diameter

• Aerosols coated by thin layer liquid water

• Size small enough to not scatter in the visible region, but…

• Absorb in LWIR because of the water coating resulting in lower transmission

Primary Approach

• Image Analysis & Modeling– Get smart/review topics of humidity, aerosols, and

LWIR– Study the observed phenomenon in the previously

collected imagery– Radiometric model these effects (MODTRAN)– Tool development for analysis/visualization of

simulations

Secondary Approach

• Instrumentation & Field Experiments– Ground-based observation of these effects

• Develop Instrumentation• Measure Environmental Condition• Simultaneous imaging in VIS-LWIR

Most Figures and Facts are stolen from

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Basic Concepts

• Water in the atmosphere– Water Vapor– Hydrometeors– Part of Aerosol

• Measures of Moisture– Mixing ratio

• [g/cm^3]

– Dew Point• Temperature to which air is cooled to reach saturation

– Relative Humidity • Ratio of partial pressure of water vapor to partial pressure of

saturated air at a given temperature

Surface Spectral Measurements

What are typical atmospheric water vapor values?

• Tropical Atmosphere - 3.55517 GM / CM2

• Mid-latitude Summer - 2.50788 GM / CM2• Mid-latitude Winter - 0.74752 GM / CM2

• Subarctic Summer - 1.81400 GM / CM2• Subartctic Winter - 0.37745 GM / CM2

• 1976 US Standard - 1.24007 GM / CM2

Water as a particle

• Difficult for Pure Water to become particles

Water condenses on other particles

Possible for particles to be in a Haze State

• R=microns

Log-normal Distribution

Sample Diameters of Particles

Electro-physics IR Camera and Sony Camcorder

Electrophysics EZ-Therm

• Pros– More portable– IR camera meant for field

work

• Cons– Separate Cameras Difficult

to Manage– Visible Camera unreliable in

high humidity conditions– Conventional Video

recording limited to 2 hours max

– Not meant for persistent surveillance

BAE Bolometer Sensor Head

• Attempted use in MDCT Project

• Conclusion: Not really packaged properly

• Requires Rube-goldberg setup of PC, power, recording setup

• Multiple copies of camera

What about humidity measurements?

• Off the shelf weather station (mostly stationery)

• Kestral - mobile, but not suitable for long term monitoring

Enter Bob Kremens Fire Weather Stations

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Weather Station Features

• Basic Met Data• Customizable• *RF-enabled• Need to modify for

GPS capability…• Easier said than

done.

Hardware Advice - Make Multiple Copies

• Remember, there was a backup mirror for the Hubble.

When I broke hardware, I attended Seminars

• Continued attempt to procrastinate

• IS&T (Rich Hailstone) - nanoparticles!

• Research Computing

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Summary of RC Seminar• Use of computational fluid

dynamics– Aerosol and Particle

Deposition in Lungs

• Lab setup for imaging air flow– Use laser fluorescence of

micron size particle (30 microns?)

• Effects of Tobacco byproduct deposition

Followup Discussion

• Discussed experiments using <200 nm particles– Dr. Robinson Currently not setup of this– Aerosol equipment company called TSI

• Check out Rich Hailstone’s lab– Can fabricate nanoparticles [nm], but typically in solution or

substrate.– No means to aerosolize

Grand Opening Celebration

Hardware Advice - Make Multiple Copies

• Remember, there was a backup mirror for the Hubble.

Conesus Tracks with Humidity

Relative Humidity vs Time/Position

0

10

20

30

40

50

60

70

80

90

100

1 25 49 73 97 121 145 169 193 217 241 265

Time/Position

Relative Humidity

Series1

Tested again on the Last MISI/LANDSAT Collect

Relative Humidity vs. Time/Position

0

10

20

30

40

50

60

70

80

1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 109

Time/Position

Relative Humidity

Series1

Ready for next year’s collection season

While the snow is flying and our airborne sensors are not…

Deploying the MDCT Weather Heads

Currently Repackaging IR & VIS Camera

• Need to figure out trigering based on meteorologial parameters

• Simultaneous video recording of imagery

• Work in Progress…

When the ladder is too short…

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What is the relationship to humidity?

• Thank you Frank Padula and Jason Faulring

• (www.weatherunderground.com)

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Wind DataQuickTime™ and a

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What constituent has spectral features?

• Use Odonnell and Pogorzala techniques to possibly identify?– Statistics based

• Apply Topology-based techniques as alternative

• More to come…

Crazy Thought!

• Can Land feature anomaly be caused by the imaging aircraft exhaust plume?

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Meanwhile… Back at the Google Ranch

• Described lab setup to generate hydrocarbon aerosol particles in the 1x10e6 concentration.

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• PASTE DIAGRAM OF VERANTH SETUP HERE

• Turns out Veranth is no longer at UR

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What is it?

HUCAPS

More Work To Do…

• MODTRAN v2 r11 simulations– Topological Tool Analysis

• Camera Package Integration• <200 [nm] Imaging Lab Experiment• Spectral Image Analysis• Matt’s Cooling Tower Experiment• Field Imaging and Instrumentation

Experiment (Spring overflight)

Wants

• Weather Station for the HUCAPS

• Persistent Imaging of the Surround

Deploying the MDCT Weather Heads