Temporal coverage: 9 May 2013 - present
The Microwave Limb Sounder (MLS) Ozone (O3) Mixing Ratio layer at 46hPa (hectopascals) indicates ozone levels at the vertical atmospheric pressure level of 46hPa, and is measured in parts per billion by volume (ppbv).
Ozone plays important roles in atmospheric chemistry and radiative balance throughout the atmosphere. Chemically, it is a powerful oxidant. Radiatively, it is an important greenhouse gas, particularly at 10 to 15 km. At the Earth's surface, it is a toxic component of air pollution with significant public health and agricultural impacts. The stratospheric ozone layer from 15 to 50 km absorbs UV radiation, protecting life at the surface and, through heating by the absorbed radiation, largely determines the temperature structure of the middle atmosphere.
Ozone is a critical player in all three of the primary objectives of MLS: to track stability of the stratospheric ozone layer, to help improve predictions of climate change and variability, and to help improve understanding of global air quality. MLS ozone measurements contribute to understanding of processes that control the expected recovery of the ozone layer as abundances of human-produced, ozone depleting substances decline in the coming decades. Ozone, particularly in the upper troposphere (10 to 15 km), is an important greenhouse gas. While MLS does not measure ozone down to the Earth's surface, MLS measurements can be used to improve the vertical resolution of other sensors on the Aura satellite, allowing mid- and lower-tropospheric ozone to be distinguished from the large amounts of ozone in the stratosphere and upper troposphere. In the upper troposphere, ozone levels provide important information about the history of air parcels, with high ozone generally indicating descent from above and low ozone ascent from below.
The MLS Ozone (O3) Mixing Ratio 46hPa layer is derived from the MLS Ozone product (ML2O3_NRT) available from the Microwave Limb Sounder (MLS) instrument on the Aura satellite. The sensor resolution is 5 km, imagery resolution is 2 km, and the temporal resolution is twice daily (day and night).
References: GES DISC - ML2HNO3_NRT: MLS/Aura Near-Real-Time L2 Nitric Acid (HNO3) Mixing Ratio V004; MLS - HNO3 Product