Water vapor measurements at ALOMAR over a solar cycle compared with model calculations by LIMA

Abstract

[1] Microwave water vapor measurements between 40 and 80 km altitude over a solar cycle (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) were carried out in high latitudes at Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69.29°N, 16.03°E), Norway. Some smaller gaps and three interruptions of monitoring in the winters 1996/1997 and 2005/2006 and from spring 2001 to spring 2002 occurred during this period. The observations show a distinct year-to-year variability not directly related to solar Lyman-a radiation. In winter the water vapor mixing ratios in the upper domain were anticorrelated to the solar activity, whereas in summer, minima occurred in the years after the solar maximum in 2000/2001. In winter, sudden stratospheric warmings (SSWs) modulated the water vapor mixing ratios. Within the stratopause region a middle atmospheric water vapor maximum was observed, which results from the methane oxidation and is a regular feature there. The altitude of the maximum increased by approximately 5 km as summer approached. The largest mixing ratios were monitored in autumn. During the summer season a secondary water vapor maximum also occurred above 65 km most pronounced in late summer. The solar Lyman-a radiation impacts the water vapor mixing ratio particularly in winter above 65 km. In summer the correlation is positive below 70 km. The correlation is also positive in the lower mesosphere/stratopause region in winter due to the action of sudden stratospheric warmings, which occur more frequently under the condition of high solar activity and the enhancing the humidity. A strong day-to-day variability connected with planetary wave activity was found throughout the entire year. Model calculations by means of Leibniz-Institute Middle Atmosphere model (LIMA) reflect the essential patterns of the water vapor variation, but the results also show differences from the observations, indicating that exchange processes between the troposphere and stratosphere not modeled by LIMA could have influenced the long-term variability. We show results of measurements, compare these with calculations, and discuss the chemical and dynamical backgrounds of the variation of water vapor in the middle atmosphere.

Ionization and NO production in the polar mesosphere during high-speed solar wind streams: model validation and comparison with NO enhancements observed by Odin-SMR

“…The ionization and ion-chemistry calculations require appropriate minorconstituent models for NO and H 2 O, respectively. For H 2 O we have made an analytical approximation to the climatologies reported by Hartogh et al (2010) (from a decade of year-round measurements from Andenes, northern Norway) and by Rong et al (2010) (polar summer mesosphere in both hemispheres observed by the SOFIE instrument on the AIM satellite). This is illustrated in the right-hand panel of Fig.…”

Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere

“…Pronounced daily water variability is connected to planetary wave activity throughout the year (Hartogh et al, 2010). The largest water vapour concentrations have been found during summer because of intensified gravity wave upward propagation.…”

“…Recent research has been quite successful in mapping the water vapour pattern in the lower mesosphere and explaining possible mechanisms for cluster ion formation (Solomon et al, 1981;Gumbel and Witt, 2002;Sonnemann et al, 2005Sonnemann et al, , 2012Hervig and Siskind, 2006;Lossow et al, 2007;Grygalashvyly et al, 2009;Hartogh et al, 2010;Gabriel et al, 2011). However, the ionospheric parameter responses to water vapour variability in the mesosphere and the lower thermosphere are very complicated.…”

First detection of tidal behaviour in polar mesospheric water vapour by ground based microwave spectroscopy

“…On the other hand, the ground based instrument needs information about global scale waves from satellites to be able to draw conclusions about the observed variations. Ground based microwave spectroscopy is a well-established technique which has proven to be useful for observations of the water vapour mixing ratio (WVMR) on different time scales, from long term trends and seasonal behaviour to isolated events such as sudden stratospheric warmings (Hartogh and Jarchow, 1995;Nedoluha et al, 1996;Seele and Hartogh, 2000;Hartogh et al, 2010). The chemical lifetime of water vapour in the middle atmosphere is on the order of days to weeks (depending on altitude) which is similar to the characteristic dynamical time scale of interest and can therefore be used as a tracer molecule (Brasseur and Solomon, 1998).…”