Welcome to the Microwave Limb Sounder (MLS) Web Site

The Microwave Limb Sounder (MLS) experiments measure naturally-occurring microwave thermal emission from the limb (edge) of Earth's atmosphere to remotely sense vertical profiles of atmospheric gases, temperature, pressure, and cloud ice.  The overall objective of these experiments is to provide information that will help improve our understanding of Earth's atmosphere and global change.

The first MLS experiment in space (UARS MLS) was on NASA's Upper Atmosphere Research Satellite (UARS) launched 12 Sept 1991. After March 1994, the UARS MLS measurements became increasingly intermittent due to conserving satellite power and the MLS scan mechanism lifetime. The last data were obtained on 25 August 2001 (for more information go to UARS MLS data).

The second (EOS MLS) is on the NASA Earth Observing System (EOS) Aura mission launched 15 July 2004. EOS MLS began full-up atmospheric science observations on 13 August 2004, with excellent performance to date in all portions of the instrument. Data are now publicly available (for information go to EOS MLS data).

MLS Observations of Dynamics and Transport During the Record-breaking 2009 Arctic Stratospheric Major Warming

MLS observations of water vapor in the northern hemisphere lower stratosphere on three days in 2009, showing the breakdown of the polar vortex during a 'stratospheric sudden warming'. The vortex is apparent as the region of air with large water vapor abundances (red/purple colors) on January 24. The subsequent splitting and dissolution of the vortex disrupted the processes that usually occur in the winter polar stratosphere. In particular, the level of chemical ozone loss during the 2008/2009 northern winter was much less than is typical.