Polar Mesospheric Clouds (PMCs) -also known as- Noctilucent Clouds (NLCs) Mark Hervig GATS Inc. Driggs, Idaho

Noctilucent Cloud (NLC) Characteristics NLCs occur: Near 83 km altitude, almost the edge of space Poleward of 50 degrees latitude, in both hemispheres During summer NLCs are composed of water ice crystals 50 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 (O 2 ), 21% Argon (Ar), 0.9% Minor Constituents: Water vapor (H 2 O), up to ppmv Carbon dioxide (CO 2 ), 350 ppmv Ozone (O 3 ), 6 ppmv Methane (CH 4 ), 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 (CO 2 ) Humidity is affected by methane (CH 4 ): CO 2 and CH 4 are increasing due to human activities Increasing CO 2 : warms the troposphere, “greenhouse effect” cools the mesosphere, where NLCs occur Increasing CH 4 : methane becomes water: CH 4 + OH > CH 3 + H 2 O 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) Rockets Balloons 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 CO 2 in the Atmosphere The increase in CO 2 is due to human activities

Temperature in the Mesosphere is decreasing This cooling is related to the increase in CO 2 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 (CH 4 ) 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 School Fairbanks 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