Ground-based Millimeter-wave Observations of Water Vapor Emission (183 GHz) at Atacama, Chile
Abstract
We report a ground-based mm-wave observation of the stratospheric and mesospheric water vapor in Atacama Chile in December 2005 Stratospheric water vapor is an important trace gas in the middle atmosphere because it is a source of odd hydrogen influencing ozone chemistry and is one of the greenhouse gases which affect the radiation balance in the middle atmosphere Previous observations suggest that the stratospheric water vapor had increased at a rate about 1 yr since 1950s e g SPARC Report 2000 whereas in 2000s it decreases at -0 1 yr e g Nedoluha et al 2003 We forward a plan of observing mm-wave spectra of water vapor 183 310 GHz at Atacama northern part of Chile at an altitude of 4 800 m in order to understand the mechanism of temporal variations of stratospheric water vapor In December 2005 we succeeded in obtaining water vapor spectra at Atacama with the mm-wave radiometer equipped with a superconductive SIS receiver developed by Nagoya University and NAOJ A vertical profile of the water vapor mixing ratio from 40 to 70 km was retrieved by using a modified optimal estimated algorithm Nagahama et al 1999 The retrieved mixing ratio was systematically smaller than the climatological value because of underestimation of tropospheric optical depth caused by less suppression of image side band sensitivity For accurate estimation of the optical depth we are developing a sideband separation receiver by using a waveguide split block e g Asayama et al 2004
- Publication:
-
36th COSPAR Scientific Assembly
- Pub Date:
- 2006
- Bibcode:
- 2006cosp...36.2995K