Mass exchange in the stable boundary layer by coherent structures D.I. Cooper a, * , M.Y. Leclerc b , J. Archuleta a , R. Coulter d , W.E. Eichinger c , C.Y.J. Kao a , C.J. Nappo e a Los Alamos National Laboratory, MS J577 Los Alamos, NM 87545, USA b University of Georgia, Griffin, GA 30223, USA c University of Iowa, Iowa City, IA 52242, USA d Argonne National Laboratory, Argonne, IL 60439, USA e NOAA-ATDD, Oak ridge, TN 37830, USA Received 4 March 2004; received in revised form 18 November 2004; accepted 5 December 2004 Abstract Observations of multi-dimensional water vapor structures in the first 75 m of the stable boundary layer (SBL) were made using a high resolution scanning Raman lidar in October 2000 during the Vertical Transport and Mixing Experiment (VTMX). Lidar images reveal the intermittent presence of plumes and low-frequency structures contributing to much of the nocturnal surface–atmosphere mass exchange. Furthermore, periodic wave–turbulence interactions between solitary waves aloft and coherent structures at the surface were observed. Results show that when low-level waveguides are present in the SBL, downward transport by pressure fluctuations arising from Kelvin–Helmholz instabilities hundreds of meters above the surface appears to pump energy near the surface thereby supporting the development of coherent structures. These structures have a vertical extent determined by the depth of the low-level waveguide inversion. The present results suggest that, in certain nocturnal conditions, coherent structures can transport more than a third of the mass exchanged between the surface and the lowest region of the stable atmospheric boundary layer. # 2005 Elsevier B.V. All rights reserved. Keywords: Lidar; Stable boundary layer; Turbulence; Intermittency; Waves; Wave–turbulence interactions; Nocturnal surface–atmosphere exchange; Wave and atmospheric gaseous exchange 1. Introduction Mass and energy exchange in the stable boundary layer remains poorly understood, especially in terms of its spatial properties near the surface. In this paper, we postulate that intermittency is an intrinsic component of the nocturnal exchange process and that it can be initiated by wave processes higher up in the atmosphere. To date, few experiments have used high-resolution imaging systems in the nocturnal environment near the surface (<50 m) (Chimonas, 1999; Ince et al., 2000; DiGirolamo et al., 2000; Taylor et al., 2004). Profiling sensors such as radars and sodars typically have a radial resolution of the order of 5–20 m. However, given that their lowest resolvable levels hover between 5 and 20 m above the surface, their utility is limited since structures have a spatial extent ranging from 10 to 50 m near the ground (Boppe et al., 1999). There have been a few exceptions as is the case of Kelvin–Helmholtz waves observed by sodars down to 25 m (Zamora, 1983). However, sodars provide only one-dimensional www.elsevier.com/locate/agrformet Agricultural and Forest Meteorology 136 (2006) 114–131 * Corresponding author. Tel.: +1 505 665 6501; fax: +1 505 667 9122. E-mail address: Dcooper@lanl.gov (D.I. Cooper). 0168-1923/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.agrformet.2004.12.012