A study of winter static stability regimes in the Dry Valleys using pseudo-vertical profiles of temperature Peyman Zawar-Reza* ,1 , Marwan Katurji 1,2 , Bob Noonan 1 , Iman Soltanzadeh 1 , Tanja Dallafior 1,3 , Sharon Zhong 2 1 Centre for Atmospheric Research, University of Canterbury, Christchurch, New Zealand 2 Department of Geography, Michigan State University, East Lansing, Michigan 3 Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland *peyman.zawar-reza@canterbury.ac.nz 1. Introduction Surface climatology of the McMurdo Dry Valleys (MDV) has been studied relatively extensively in the past three decades. In winter, katabatic winds affect the climate of the MDV by increasing local air temperatures by as much as 30°C (Nylen et al. 2004). It has been estimated that an increase of 1% in frequency in strong katabatic events, can increase average winter temperatures by 1°C. The summer wind regimes can be quite different and are predominantly driven by the heating and cooling cycles of the surface in response to solar insolation during synoptically quiescent periods. Due to logistical reasons and remoteness, little attention has been paid to the within the valley vertical structure of the boundary layer. A rare glimpse into the vertical stability of the valley atmosphere was provided by McKendry and Lewthwaite (1990; hereafter ML1990), but for the summertime field season only. ML1990 used a combination of airsondes, pilot balloons, and monostatic acoustic sounder to derive their Wright Valley vertical profiles. Subsequent studies that cited ML1990 did not build up on the papers knowledge base, so the state of knowledge has remained the same. ML1990 discuss the fact that down-valley strong katabatic winds (in summer) possess neutral stability extending to heights of 2000 to 4000 m, but they also measure periods when stable regimes decouple the surface layer air from aloft. Although very informative, ML1990 studies stability for a few case studies and in summer, we hope to complement this work by extending the analysis into winter and at higher temporal resolution. There is no information available on the vertical extent of the (stable) boundary layer that can form during synoptically quiescent periods or the thickness of the katabatic intrusions into the valley system climatologically. Data on static stability of the atmosphere can guide not only surface based meteorological studies, but is a good source of validation for mesoscale modelling research. To our knowledge, Whiteman et al. (2004) was the first study that pioneered the use of surface based temperature measurements to derive pseudovertical temperature profiles. They derived vertical stability by deploying a line of temperature dataloggers in a valley in Rocky Mountains. In that study, it was shown that pseudovertical temperature soundings at night approximated free air temperature soundings over the centre of the valley, thereby providing useful insight into night-time evolution of the boundary layer. Fast et al. (2005) applied the same reasoning to study nocturnal boundary layer over Phoenix, Arizona. Motivated by these studies, we apply the same methods towards the Dry Valleys atmosphere, initially for the Wright Valley. Therefore we present the first assessment of winter static stability in this valley using miniature temperature sensors called iButtons as described below. Figure 1 Map of McMurdo Dry Valleys; the red dot shows the location of the AWS while the blue line marks the line where the iButtons array was installed.