Correlative Analysis of PMC Existence and Mesospheric Temperature and Water Vapour
Polar Mesospheric Clouds (PMCs) -also known as- Noctilucent Clouds (NLCs)
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Transcript of Polar Mesospheric Clouds (PMCs) -also known as- Noctilucent Clouds (NLCs)
Polar Mesospheric Clouds (PMCs)-also known as-
Noctilucent Clouds (NLCs)
Mark Hervig
GATS Inc.
Driggs, Idaho
Noctilucent Cloud (NLC) CharacteristicsNLCs occur:
Near 83 km altitude, almost the edge of spacePoleward of 50 degrees latitude, in both hemispheresDuring summer
NLCs are composed of water ice crystals50 nanometers in radius (the radius of human hair is 500 times larger)
Because they are ice clouds, their formation is controlled by:
temperature
humidity
NLC over Finland, photo by Pekka Parviainen
NLCs are visible from the ground
NLC over Finland, photo by Pekka Parviainen
Shortly after sunset, the observer is in darkness, but the NLC is still in sun light
The Earth’s Atmosphere, in brief
Composition of the Atmosphere
Major Constituents:Nitrogen (N), 78%Oxygen (O2), 21%Argon (Ar), 0.9%
Minor Constituents:Water vapor (H2O), up to 10000 ppmvCarbon dioxide (CO2), 350 ppmvOzone (O3), 6 ppmvMethane (CH4), 1.7 ppmv and others…..
ppmv = “parts per million by volume”
Vertical Structure of the Atmosphere
Layers in the atmosphere are defined by temperature
Weather as we know it happens in the troposphere
NLCs
Clouds in the Atmosphere
Most clouds occur in the troposphere
Except NLCs
They occur in the mesosphere
Clouds form when water vapor in the atmosphere condenses
Clouds are a collection of water drops and/or ice crystals
Water vapor condenses when the temperature cools
Rising air expands, expanding air cools, so…. rising air = clouds (sometimes)
NLC Formation
NLC formation is similar to that of “every day” clouds:
Water vapor condenses into ice when temperatures cool
This cooling is due to rising air
NLCs are different than “every day” clouds:
NLCs form 70 km (43 miles) higher
They only occur during summer
They only occur at high latitudes (50 degrees to the pole)
Why do they occur only in summer high latitudes?
weather patterns
Why should we study NLCs?• NLCs respond to atmospheric temperature and humidity
Temperature is affected by carbon dioxide (CO2)
Humidity is affected by methane (CH4):
• CO2 and CH4 are increasing due to human activities
• Increasing CO2: warms the troposphere, “greenhouse effect” cools the mesosphere, where NLCs occur
• Increasing CH4:
methane becomes water: CH4 + OH > CH3 + H2O
• NLCs are a visible indication of climate change “The minors canary” of climate change
How do we measure NLCs?
In Situ Measurements (instrument in contact with the subject)
RocketsBalloons and Airplanes can’t fly high enough
Remote Measurements (instrument is far from the subject)
Ground observers: visual, cameras
LIDAR (light detection and ranging)
RADAR (radio detection and ranging)
Satellites: mapping, solar occultation
LIDAR
NLC measurements from satellite
examples of satellite measurements :
Limb sounding: light absorption
Nadir imaging: light scattering
NLC patterns are changing dramatically
NLCs are occurring more often than before
NLCs are occurring farther south than before
NLC photo by Timo Leponiemi
Are these changes telling us something?
NLC Occurrence Versus Time
NLCs occur nearly twice as often as they did 35 year ago
From Gaddsen, 1997
NLC Locations: Old and New
US Towns where NLCs were recently sighted:
Twin Falls, Idaho Logan, Utah Boulder, Colorado Glen Ullin, North Dakota McGuire, New Jersey
NLCs are occurring 700 miles farther south than ever before
What is causing the changes in NLCs?
NLC over Finland, photo by Pekka Parviainen
Increasing CO2 in the Atmosphere
The increase in CO2 is due to human activities
Temperature in the Mesosphere is decreasing
This cooling is related to the increase in CO2
Temperatures near 80 km have cooled by almost 5 degrees Kelvin (K) every 10 years, since measurements were started in the 1950’s
Increasing Methane (CH4) in the Atmosphere
This increase is due to human activities
Some evidence suggests an increase in mesospheric H2O, but this is not yet clear.
What are we doing in Driggs?
NASA’s Office of Space Science has funded a project in Driggs called:
“Polar Mesospheric Clouds in the Classroom”
Goals of this project are to
Educate the public about NLCs
Observe NLCs using digital cameras
This project is a partnership between GATS Inc. and Teton High School
On the web: gwest.gats-inc.com/pic/nlc_epo_home.html
NLC Cameras
Digital Cameras will be used to look for NLCs
Our images will posted on the internet
What we learn will help scientists who study NLCs
Camera locations:
Teton High SchoolFairbanks Alaska
Finland ??Antarctica ??You decide
We will install 3 “NLC-cams” each year
What can You do?
NLC Cameras:
Choose the right cameras for the job
Install the Driggs cam
Determine the best way to operate them
Connect them to the internet
Pick good locations for future cameras, anywhere in the world
Analyze the images, look for NLCs
Project Web Pages
Develop interactive web pages
Display and archive the “NLC-cam” images
Update project information
Education
Take what we learn and share it with other students/schools