The Spread of the Hunga Tonga H2O Plume in the Middle Atmosphere Over
the First Two Years Since Eruption
Abstract
The eruption of Hunga Tonga in January 2022 injected a large amount of
water into the stratosphere. Satellite measurements from Aura Microwave
Limb Sounder (MLS) show that this water vapor (H2O) has now spread
throughout the stratosphere and into the lower mesosphere, resulting in
an increase of >1 ppmv throughout most of this region.
Measurements from three ground-based Water Vapor Millimeter Wave
Spectrometer (WVMS) instruments and MLS are in good agreement, and show
that in 2023 there was more H2O in the lower mesosphere than at any time
since the WVMS measurements began in the 1990’s. At Table Mountain,
California all WVMS H2O measurements at 54 km since June 2023, and all
of the measurements from Mauna Loa, Hawaii, since the resumption of
measurements in September 2023, show larger mixing ratios than any
previous measurements. At 70 km several recent ~1 week
WVMS retrievals in the last few months show the largest anomalies ever
measured. The MLS measurements show that maximum H2O anomalies have
occurred throughout almost all of the stratosphere and lower mesosphere
since the eruption. As of November 2023, almost all of the
~140 Tg of water originally injected into the
stratosphere by the Hunga Tonga eruption remains in the middle
atmosphere at pressures below 83 hPa (altitudes above
~17 km). The eruption occurred during a period when
stratospheric H2O was already slightly elevated above the 2004-2021 MLS
average, and the November 2023 anomaly of ~160 Tg
represents ~15% of the total mass of H2O in this
region.