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Long-lived contrailsand convective cirrusabove the tropicaltropopause U. SchumannChristoph KiemleHans Schlager2017 год

Long-lived contrails and convective cirrus above the tropical tropopause
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Аннотация: Abstract. This study has two objectives: (1) it characterizes contrails at very low temperatures and (2) it discusses convective cirrus in which the contrails occurred. (1) Long-lived contrails and cirrus from overshooting convection are investigated above the tropical tropopause at low temperatures down to −88 °C from measurements with the Russian high-altitude research aircraft M-55 Geophysica, as well as related observations during the SCOUT-O3 field experiment near Darwin, Australia, in 2005. A contrail was observed to persist below ice saturation at low temperatures and low turbulence in the stratosphere for nearly 1 h. The contrail occurred downwind of the decaying convective system Hector of 16 November 2005. The upper part of the contrail formed at 19 km altitude in the tropical lower stratosphere at ∼ 60 % relative humidity over ice at −82 °C. The ∼ 1 h lifetime is explained by engine water emissions, slightly enhanced humidity from Hector, low temperature, low turbulence, and possibly nitric acid hydrate formation. The long persistence suggests large contrail coverage in case of a potential future increase of air traffic in the lower stratosphere. (2) Cirrus observed above the strongly convective Hector cloud on 30 November 2005 was previously interpreted as cirrus from overshooting convection. Here we show that parts of the cirrus were caused by contrails or are mixtures of convective and contrail cirrus. The in situ data together with data from an upward-looking lidar on the German research aircraft Falcon, the CPOL radar near Darwin, and NOAA-AVHRR satellites provide a sufficiently complete picture to distinguish between contrail and convective cirrus parts. Plume positions are estimated based on measured or analyzed wind and parameterized wake vortex descent. Most of the non-volatile aerosol measured over Hector is traceable to aircraft emissions. Exhaust emission indices are derived from a self-match experiment of the Geophysica in the polar stratosphere in 2010. The number of ice particles in the contrails is less than 1 % of the number of non-volatile aerosol particles, possibly because of sublimation losses and undetected very small ice particles. The radar data show that the ice water content in convective overshoots is far higher than measured along the flight path. These findings add insight into overshooting convection and are of relevance with respect to hydration of the lower stratosphere.
Год издания: 2017
Авторы: U. Schumann, Christoph Kiemle, Hans Schlager, Ralf Weigel, Stephan Borrmann, Francesco D’Amato, Martina Krämer, Renaud Matthey, Alain Protat, Christiane Voigt, C. M. Volk
Издательство: Copernicus Publications
Источник: Atmospheric chemistry and physics
Ключевые слова: Atmospheric Ozone and Climate, Atmospheric chemistry and aerosols, Atmospheric aerosols and clouds
Другие ссылки: Atmospheric chemistry and physics (PDF)
Atmospheric chemistry and physics (HTML)
DOAJ (DOAJ: Directory of Open Access Journals) (HTML)
JuSER (Forschungszentrum Jülich) (HTML)
JuSER (Forschungszentrum Jülich) (PDF)
JuSER (Forschungszentrum Jülich) (HTML)
elib (German Aerospace Center) (HTML)
elib (German Aerospace Center) (HTML)