Universität zu Köln

Krause, P., Sornig, M., Wischnewski, C., Kostiuk, T., Livengood, T. A., Herrmann, M., Sonnabend, G., Stangier, T., Wiegand, M., Paetzold, M., Mahieux, A., Vandaele, A. C., Piccialli, A. and Montmessin, F. (2018). Long term evolution of temperature in the venus upper atmosphere at the evening and morning terminators. Icarus, 299. S. 370 - 386. SAN DIEGO: ACADEMIC PRESS INC ELSEVIER SCIENCE. ISSN 1090-2643

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Abstract

This paper contains a comprehensive dataset of long-term observations between 2009 and 2015 at the upper mesosphere/lower thermosphere providing temperature values at different locations of the morning and evening side of the terminator of Venus. Temperature information is obtained by line-resolved spectroscopy of Doppler broadened CO2 transitions features. Results are restricted to a pressure level of 1 pbar, similar to 110 km altitude due the nature of the addressed non-LTE CO2 emission line at 10 mu m. The required high spectral resolution of the instrumentation is provided by the ground-based spectrometers THIS (University of Cologne) and HIPWAC (NASA GSFC). For the first time upper mesosphere/lower thermosphere temperatures at the Venusian terminator derived from IR-het spectroscopy between 2009 and 2015 are investigated in order to clarify the local-time dependences, latitudinal dependences and the long-term trend. Measured temperatures were distributed in the range between 140 K and 240 K, with mean values equal to 199 K +/- 17 K for the morning side of the terminator and 195 K +/- 19 K for the evening side of the terminator. Within the uncertainty no difference between the averaged morning and evening terminator side temperature is found. In addition, no strong latitudinal dependency is observed at these near terminator local times. In contrast IR-het data from 2009 show a strong latitudinal dependency at noon, with a temperature difference of around 60K between the equatorial and polar region (Sonnabend et al., 2012). Accord with the instruments of the Venus Express mission a northern-southern hemispherical symmetry is observed (Mahieux et al., 2012; Piccialli et al., 2015). The data shows no consistent long-term temperature trend throughout the six years of observation, but a variability in the order of tens of Kelvin for the different observing runs representing a time step of few month to two years. This is about the same order of magnitude as the variability within a single run with a typically time range of 2-10 days. This variation is not connected to the solar cycle. Sub millimeter observations by Clancy et al. found a relation between temperatures and long-term variation in mesospheric water vapor, SO2, and sulfate aerosols (Clancy and Muhleman, 1991; Clancy et al., 2012). SO2 column densities observed by SOIR at the terminator are fairly stable over the time period of 2006-2011 (Mahieux et al., 2015), supporting the hypothesis of a relation between SO2 and temperature variations. The temperatures derived from the infrared heterodyne spectroscopy (IR-het) are compared to results from the Venus Express space mission (VEx). A consistence with the temperatures from the VEx instruments SOIR, VIRTIS and SPICAV is found. As the instruments probe different local time, SPICAV probes the pure nightside, SOIR across the terminator and IR-het the pure dayside atmosphere it is not surprising that the IR-het temperatures are mostly on the warmer side compared to results from SPICAV and SOIR. (C) 2017 Elsevier Inc. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Krause, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sornig, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wischnewski, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kostiuk, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Livengood, T. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Herrmann, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sonnabend, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stangier, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wiegand, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Paetzold, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mahieux, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vandaele, A. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Piccialli, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Montmessin, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-205185
DOI:	10.1016/j.icarus.2017.07.030
Journal or Publication Title:	Icarus
Volume:	299
Page Range:	S. 370 - 386
Date:	2018
Publisher:	ACADEMIC PRESS INC ELSEVIER SCIENCE
Place of Publication:	SAN DIEGO
ISSN:	1090-2643
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MU-M WAVELENGTH; SPECTRAL-LINE OBSERVATIONS; HETERODYNE SPECTROSCOPY; THERMAL STRUCTURE; GLOBAL CIRCULATION; CARBON-MONOXIDE; EXPRESS; WINDS; MESOSPHERE; CO2 Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/20518