MLS

Aura's Microwave Limb Sounder

This image is an animated version of the Aura satellite in orbit. The satellite, seen centered in the image, is made up of silver and gold box-like shapes and instruments. Spanning out to the right of the satellite is a long sheet of solar panels. In the background of the image at the bottom is a portion of Earth seen with clouds and a blue haze surrounding it. The top of the background is the deep black of space, with a cluster of green colored stars to the left.

Aura's Microwave Limb Sounder (MLS) instrument uses microwave emission to measure stratospheric temperature and upper tropospheric constituents. MLS also has unique capability to measure upper tropospheric water vapor in the presence of tropical cirrus, and the cirrus ice content. These measurements are valuable for diagnosing the potential for severe loss of Arctic ozone when abundances of stratospheric chlorine will still be high, and slight cooling of the stratosphere could exacerbate ozone loss due to chlorine chemistry.

MLS is providing the first global measurements of hydroxide, hydroperoxyl and bromine monoxide, constituents that play an important role in stratospheric chemistry. MLS is unique in its ability to provide these measurements in the presence of tropical cirrus, where important processes affecting climate variability occur. MLS also provides unique measurements of cirrus ice content.

The simultaneous MLS measurements of upper tropospheric water vapor, ice content, and temperature, under all conditions and with good vertical resolution, will be of great value for improving our understanding of processes affecting the distribution of atmospheric water, climate variability, and tropospheric-stratospheric exchange. The simultaneous measurements of carbon monoxide and nitrous oxide enhance the value of this data set by helping identify source regions of the air masses being observed.

Official MLS Instrument website
Browse the MLS Science Feature Collection

MLS helps improve understanding and assessment of:

 Ozone Depletion

MLS measures the vertical profiles of ozone and many chemical species that affect it. It is providing the first global measurements of stratospheric and mesospheric OH and HO2, the key chemicals in hydrogen chemistry that destroys ozone.

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A side-by-side comparison of modeled ozone concentration in Earths atmosphere with the Montreal Protocol (left) and without (right).
Previous “world-avoided” experiments have shown that, without the Montreal Protocol, ozone levels would be depleted globally by the mid-twentieth century.
NASA/Goddard Space Flight Center Scientific Visualization Studio

Climate Change

The primary MLS measurements for helping understand climate change are water vapor and cloud ice in the upper troposphere. Feedbacks associated with water vapor in the upper troposphere, depending upon the process, can either amplify or attenuate the effects of other greenhouse gases. Measurements of upper tropospheric cloud ice provide new information on these processes, especially deep convection.

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This week NASA is celebrating the Aura mission's 10th anniversary. With its four instruments, Aura measures greenhouse gases, clouds and dust particles, among other climate agents in the atmosphere.
This week NASA is celebrating the Aura mission's 10th anniversary. With its four instruments, Aura measures greenhouse gases, clouds and dust particles, among other climate agents in the atmosphere.

Air Quality

MLS observations of upper tropospheric ozone and carbon monoxide provide important new information for global air quality research. Ozone in the troposphere is a pollutant of major global concern, and CO is an excellent tracer of pollution transport. Deep convection and other processes can deposit polluted boundary layer air into the upper troposphere where faster winds transport it over long distances. As a result, the upper troposphere, where MLS makes measurements plays a significant role in the intercontinental transport of polluted air.

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A map of the U.S. showing average nitrogen dioxide concentrations for 2022. The data is color-coded. Higher concentrations are in red and lower concentrations in blue.
This map shows average concentrations of nitrogen dioxide for 2022 over the U.S., as detected by the Ozone Monitoring Instrument on NASA's Aura satellite. Higher concentrations are in red and purple. Lower concentrations are in blue.
NASA's Scientific Visualization Studio

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