Aura: A mission dedicated to the health of Earth's atmosphere


Microwave Limb Sounder (MLS)

MLS is a limb scanning emission microwave radiometer. MLS measures radiation in the GHz and THz frequency ranges (millimeter and submillimeter wavelengths). Aura’s MLS is a major technological advance over the MLS flown on UARS. MLS will measure important ozone-destroying chemical species in the upper troposphere and stratosphere. In addition, MLS has a unique ability to measure trace gases in the presence of ice clouds and volcanic aerosols.

MLS Contributions to Understanding Stratospheric Ozone

Aura’s MLS will continue the ClO and HCl measurements made by UARS. These measurements will inform us about the rate at which stratospheric chlorine is destroying ozone. MLS will also provide the first global measurements of the stratospheric hydroxyl (OH) and hydroperoxy (HO2) radicals that participate in ozone destruction. In addition, MLS will measure bromine monoxide (BrO), a powerful ozone-destroying radical. BrO has both natural and man-made sources.

MLS measurements of ClO and HCl will be especially important in the polar regions. The HCl measurements tell scientists how stable chlorine reservoirs are converted to the ozone destroying radical, ClO. Since the Arctic stratosphere may now be at a threshold for more severe ozone loss, Aura’s MLS data will be especially important.

MLS Contributions to Understanding Air Quality

MLS measures carbon monoxide (CO) and ozone in the upper troposphere. CO is an important trace gas that can indicate where and when their is an exchange of air between the stratosphere and troposphere. CO is also a tropospheric ozone precursor and its appearance in the upper troposphere can indicate strong vertical transport from pollution events.



Global maps of temperature, nitric acid, chlorine monoxide and ozone

UARS MLS simultaneously mapped key chemical constituents nitric acid (HNO3), chlorine monoxide (CLO), and ozone (O3) over the winter polar regions in both Northern (upper) and Southern (lower) Hemispheres where the greatest ozone loss occurs. Aura MLS will map these and other chemicals with better coverage and larger altitude range than UARS MLS. Together with HIRDLS, Aura MLS will measure an array of source, radical and reservoir gases in the active region of the polar stratosphere to give a complete picture of the ozone depletion process and predicted recovery. MLS will also make global measurements of BrO, OH and HO2.

MLS Contributions to Understanding Climate Change

MLS’s measurements of upper tropospheric water vapor, ice content, and temperature will be used to evaluate models and thus reduce the uncertainty in climate forcing. MLS also measures greenhouse gases such as ozone and N2O in the upper troposphere.

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