GML’s 20-year water vapor record at Lauder, New Zealand
2025-02-27
The NOAA Global Monitoring Laboratory has reached a milestone: the longest continuous upper atmospheric water vapor record in the southern hemisphere. GML’s first frost point hygrometer balloon flight from Lauder, New Zealand took place on October 5, 2004. The 20-year record, comprising monthly launches in cooperation with New Zealand’s National Institute of Water and Atmospheric Research (NIWA), is also the second longest record on earth behind the Boulder, Colorado record.
Water vapor contributes substantially to Earth’s greenhouse effect, and recent large wildfires and volcanic eruptions have caused a jump in stratospheric water vapor abundance over Lauder, New Zealand.
Water vapor primarily enters the upper atmosphere in the tropics, where the coldest temperatures prevail at the boundary between the lower and upper atmosphere, controlling the amount of water vapor that escapes from the wetter, lower atmosphere. In the upper atmosphere, the abundance of water vapor is a few parts per million. Methane oxidation also produces water vapor in the upper atmosphere, and volcanic eruptions, large wildfires, and overshooting convection typically inject relatively small amounts of water vapor into the upper atmosphere.
Under clear skies, upper atmospheric water vapor absorbs more than half of outgoing longwave radiation. Even small changes in its abundance have a significant impact on surface temperatures and induce decadal variability in greenhouse gas forcing. GML’s long-term upper atmospheric water vapor records offer insight into interhemispheric differences in atmospheric dynamics and sources of water vapor.
Time series of upper atmospheric water vapor mixing ratio over Lauder, New Zealand since 2004 and Boulder, Colorado since 1980, separated by altitude. Vertical dashed lines show notable volcanic and wildfire events.
The Lauder record, compared with the 45-year record from Boulder, Colorado, shows little variability between 2004 and 2021. Since then, a large increase in water vapor over southern hemisphere midlatitudes has been observed, attributed primarily to the underwater Hunga Tonga–Hunga Haʻapai volcanic eruption (2022).
Both the Lauder and Boulder records have been critical for the validation of water vapor retrievals from satellites and for identifying drift in satellite retrievals.
GML's water vapor measurements in New Zealand are supported by NOAA’s U.S. Global Climate Observing System (GCOS) Program and NASA's Upper Atmospheric Research Program (UACO). Over the past 20 years, many scientists from NIWA have launched the NOAA FPH instruments on balloons including; Graeme Strang, Sonia Petrie, Alan Thomas, Hamish Chisholm, Michael Kotkamp, Richard Querel, Wills Dobson, and Penny Smale. Without their significant contributions, this record would not be possible.