Mesospheric Water Vapor in 2022

The eruption of the Hunga Tonga undersea volcano in January 2022 injected water vapor to altitudes as high as 53 km, but also an unprecedented and much larger amount of water vapor into the stratosphere. Several months after the eruption, measurements from the Aura Microwave Limb Sounder (MLS) and from three ground-based Water Vapor Millimeter Wave (WVMS) instruments began to measure record-high amounts of water vapor in the mesosphere over a wide range of latitudes. While there are indications that some of this mesospheric increase in water vapor was probably caused by the Hunga Tonga eruption, the dynamical situation in 2022 also played an important part in establishing the unusually large water vapor mixing ratios, both in the upper and lower mesosphere.