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| Mesopause | |
|---|---|
| Name | Mesopause |
| Altitude km | 80–100 |
| Temperature K | ~120–270 |
| Composition | Atomic oxygen, molecular nitrogen, ozone (trace) |
| Pressure Pa | ~0.01–0.1 |
| Parent | Earth |
Mesopause The mesopause is the atmospheric region marking the temperature minimum between the stratosphere and the thermosphere, situated near 80–100 km altitude above Earth. It exhibits complex interactions among waves, tides, and chemical processes driven by forcing from Sun, Moon, and terrestrial weather systems such as the El Niño–Southern Oscillation and Madden–Julian Oscillation. Observations from platforms like TIMED (satellite), UARS, AIM (satellite) and sounding rockets complement in situ data from stations including Arecibo Observatory, Andøya Space Center, and the South Pole Station.
The mesopause demarcates the lower boundary of the thermosphere and the upper boundary of the mesosphere and is typically centered near 85–90 km, varying with latitude and season between about 80 km and 100 km; this altitude range is monitored by programs such as NASA, ESA, NOAA, JAXA and research groups at MIT, Caltech, and University of Colorado Boulder. It is influenced by planetary-scale phenomena including the Quasi-Biennial Oscillation, Stratospheric Sudden Warming, and global circulation patterns studied by institutions like the Hadley Centre and the Max Planck Institute for Solar System Research.
Temperatures at the mesopause reach minima (near 120 K to 140 K) in the summer polar mesosphere and warmer values (up to ~270 K) in winter, with seasonal and latitudinal modulation documented by missions such as AURA (satellite), ENVISAT, and instruments at Mauna Kea and Davos; variability is driven by propagation and dissipation of gravity waves, planetary waves observed in campaigns coordinated by SPARC and WCRP. Short-term variability stems from tidal forcing linked to solar cycle variations and episodic events like meteor showers, while long-term trends tie to anthropogenic influences tracked by groups at IPCC and NOAA Climate Program Office.
Mesopause dynamics are governed by gravity wave breaking, tidal forcing, and mean meridional circulation connecting to the stratosphere and thermosphere; modeling and analysis are performed with tools developed at NCAR, Goddard Space Flight Center, and European Centre for Medium-Range Weather Forecasts. Processes such as mesospheric jet formation, polar mesospheric summer echoes, and mesospheric cooling involve coupling to phenomena studied by Arecibo Observatory, EISCAT, and the International Space Station payloads, with theoretical frameworks from researchers at Princeton University, University of Cambridge, and UCLA.
The mesopause region contains atomic oxygen, molecular nitrogen, minor ozone, and metallic layers from meteoric ablation that are sources for compounds examined by CABERNET and university groups at University of Leeds and University of Bremen; chemistry includes photodissociation driven by extreme ultraviolet and reactions producing radiative cooling via infrared emission lines cataloged by databases at JPL and NIST. Metal layers such as sodium, iron, and potassium are probed by lidar groups at Leicester University and NCAR; linkage to noctilucent cloud formation implicates sites like Svalbard and observations coordinated with ESA missions.
The mesopause is the site of noctilucent clouds, polar mesospheric summer echoes, airglow, and sporadic E-layer interactions that affect radio propagation studied by ITU, NGDC, and observatories including Jicamarca Radio Observatory, EISCAT, and Arecibo Observatory. Airglow emissions in oxygen red and green lines, hydroxyl bands, and sodium D-lines are exploited by imaging systems developed at University of Wisconsin–Madison and Leibniz Institute for Atmospheric Physics to infer dynamics linked to tidal signatures identified by researchers at Lockheed Martin and universities such as UCL.
Mesopause investigations employ lidar, radar, satellite limb sounding, sounding rockets, and infrasound networks maintained by agencies including NASA, ESA, NOAA, JAXA, and national observatories; facilities such as Arecibo Observatory, EISCAT, Poker Flat Research Range, and Andøya Space Center provide high-resolution profiles. Instruments include sodium and Rayleigh lidars, Fabry–Pérot interferometers, microwave limb sounders like those on Aura and TIMED, and ground-based radars built by groups at MIT, KIT, IRF and universities like University of Illinois Urbana–Champaign.
The mesopause modulates coupling between tropospheric variability (e.g., ENSO, MJO) and the ionosphere; its state influences satellite drag, radio communications, and upper-atmosphere chemistry relevant to space weather forecasting performed by NOAA Space Weather Prediction Center and ESA Space Weather Service Network. Trends in mesospheric temperatures and composition are assessed in assessments by IPCC, WMO, and academic consortia at NCAR and Scripps Institution of Oceanography for implications on climate change, atmospheric circulation, and planetary protection studies undertaken by NASA and international partners.