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


High Resolution Dynamics Limb Sounder (HIRDLS)

HIRDLS is an infrared limb-scanning radiometer measuring trace gases, temperature, and aerosols in the upper troposphere, stratosphere, and mesosphere. The instrument will provide critical information on atmospheric chemistry and climate. Using vertical and horizontal limb scanning technology, HIRDLS will provide accurate measurements with daily global coverage at high vertical and horizontal resolution.

HIRDLS makes key contributions to each of Aura’s three science questions.

HIRDLS Contributions to Understanding Stratospheric Ozone

The largest ozone depletions occur in the polar winter in the lower stratosphere. HIRDLS will retrieve high vertical resolution daytime and nighttime ozone profiles in this region.

HIRDLS will measure nitrogen dioxide (NO2), nitric acid (HNO3) and CFCs—gases that play a role in stratospheric ozone depletion. Although international agreements have banned their production, CFCs are long-lived and will remain in the stratosphere for several more decades. By measuring profiles of the long-lived gases at 1.2 km vertical resolution, from the upper troposphere into the stratosphere, HIRDLS will make it possible to quantify the transport of air from the troposphere into the stratosphere.

Modeled global map of nitrous oxide The need for high horizontal resolution measurements of the stratosphere is illustrated above. Using a model, the long-lived trace gas N2O is transported by observed winds. The transport processes produce filamentary structures that are predicted but have never been observed globally. HIRDLS high resolution measurements will be able to observe these structures which are signatures of transport.

HIRDLS Contributions to Understanding Air Quality

HIRDLS will measure ozone, nitric acid, and water vapor in the upper troposphere and lower stratosphere. With these measurements, scientists will be able to estimate the amount of stratospheric air that descends into the troposphere and will allow us to separate natural ozone pollution from man-made sources.

HIRDLS Contributions to Understanding Climate Change

HIRDLS will measure water vapor and ozone, both important greenhouse gases. The instrument is also able to distinguish between aerosol types that absorb or reflect incoming solar radiation. HIRDLS will be able to map high thin cirrus clouds that reflect solar radiation.

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