Global satellite measurements of HDO and implications for understanding the transport of water vapour into the stratosphere

Abstract

ABSTRACT:The deuterium content of water vapour in a given air mass is sensitive to its temperature and condensation history. Isotopic measurements therefore have the potential to shed light on the transport of air and water vapour into the stratosphere. Previous measurements of the isotopic composition in the upper troposphere and stratosphere have been sparse in terms of both spatial and temporal coverage. Presented here are retrievals of the deuterium content of water vapour (HDO or δD) from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite instrument. These retrievals offer the first global scale coverage of the isotopic composition of water vapour in this altitude region and span a time period of almost two years. The spatial coverage and the time span of the dataset offer previously unattainable insight into the mean seasonal and spatial distributions of the isotopic composition of water vapour in the upper troposphere and stratosphere. Measurements of HDO are extremely challenging due to low sensitivity in the spectra at low temperatures and water vapour amounts. Nonetheless, the data show a number of interesting results. Zonal mean profiles show the greatest depletion in δD in the tropical upper troposphere, with decreasing depletion with altitude in the stratosphere due to the influence of methane oxidation. Seasonal zonal means also show a strong depletion in the southern polar spring at around 300 mbar, which is thought to be related to the occurrence of polar stratospheric clouds and dehydration events in the polar vortex. Geographically, the regions and time periods where the greatest depletions are observed in the tropical upper troposphere are those associated with strong convective activity. Results confirm that temporal variability is central to the transport of water vapour into the tropical tropopause layer (TTL) and stratosphere. The data presented here show an annual cycle in δD in the TTL which is tied to temperature and suggests that this signature propagates upwards into the stratosphere. The data also show a number of points where extremely dry air is associated with relatively enriched δD values. We postulate that these points are evidence of ice lofting.

Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

“…If performed from space, remote sensing observations can provide data on a quasi-global scale. The sensors MIPAS, SMR, and ACE allow for δD observations within and above the upper troposphere/lower stratosphere region Payne et al, 2007;Nassar et al, 2007;Lossow et al, 2011). Worden et al (2006) and Frankenberg et al (2009) perform the first space-based remote sensing observations of tropospheric δD using the US and European research satellite sensors TES and SCIAMACHY, respectively.…”

The MUSICA MetOp/IASI H<sub>2</sub>O and δD products: characterisation and long-term comparison to NDACC/FTIR data

“…Furthermore, there are space-borne scientific sensors that measure middle tropospheric δD (Worden et al, 2007) and δD at and above the upper troposphere and lower stratosphere (e.g. Steinwagner et al, 2007;Payne et al, 2007;Lossow et al, 2011). Most recently, middle tropospheric δD products applying the operational meteorological satellite sensor IASI (Infrared Atmospheric Sounding Interferometer) have been presented by Schneider and Hase (2011a), Lacour et al (2012), and Pommier et al (2014).…”

Profiles of CH<sub>4</sub>, HDO, H<sub>2</sub>O, and N<sub>2</sub>O with improved lower tropospheric vertical resolution from Aura TES radiances

“…Measurements of the isotopic ratio of water can provide an additional constraint for quantifying the distribution of the sources and exchange processes through the sensitivity of this composition to that of the moisture source, to changes in phase, and to transport and mixing processes (e.g., Kuang et al, 2003;Worden et al, 2006Worden et al, , 2007Risi et al, 2008;Nassar et al, 2007;Payne et al, 2007;Brown et al, 2008;Noone et al, 2008;Frankenberg et al, 2009;Herbin et al, 2009;Steinwagner et al, 2010;Schneider and Hase, 2011). Satellite measurements such as those from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, the Aura TES instrument, the Atmospheric Chemistry Experiment (ACE), the Infrared Atmospheric Sounding Interferometer (IASI), and the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) have been used for this purpose.…”