Several observational studies of radiation fog have been reported in the literature, mostly presenting observations of atmospheric stability within fog layers, and a discussion of the physics involved (e.g. Roach et al., 1976; Choularton et al., 1981; Meyer et al., 1986; Duynkerke, 1991; Fuzzi et al., 1992; Guédalia and Bergot, 1994; Fuzzi et al., 1998; Duynkerke, 1999; Haeffelin et al., 2010; Porson et al., 2011). However, detailed process-level observations characterizing or even documenting the effects of surface and orographic variability on dynamical controls on fog during the complete life cycle of radiation fog are largely non-existent, most probably owing to the challenges in making extensive observations of fog (in complex terrain).
The Local And Non local Fog EXperiment (LANFEX) was designed to examine how local is the develop- ment and evolution of (primarily) radition fogs in complex terrain (Lane et al., 2015).The experimental phase of LANFEX ran between mid-November 2014 to end of March 2016. Networks of instrumentation were deployed at selected sites in the shallow valley of the River Great Ouse around Bedford, UK, and deeper valleys in south-west Shropshire, UK. The present study uses a subset of the campaign data, collected around Skyborry in the section of the Teme River Valley between Knighton and Dutlas in Shropshire during the winter season 20152016.
The sites and main instruments used in this work, namely a Doppler LiDAR (DL), temperature and relative humidity data loggers, referred to as HOBOs, and Optical Particle Counters (OPCs) will be presented. The data were collected from 18 December to 26 March 2016, as part of the LANFEX field campaign. We also use radiosonde/rawinsonde (RS) and OPC upper-air data collected during the intensive observation periods (IOPs) of the field campaign. Initial results will be presented, focusing on relating observed changes in droplet size distribution throughout fog to dynamical controls on fog, following the ideas pioneered by Pilié et al. (1975a,b).
Acknowledgements. We wish to thank the land owners for providing access to their fields. The authors would like to acknowledge the National Centre for Atmospheric Science (NCAS) Atmospheric Measurement Facility (AMF) for the use of the Doppler LiDAR and HOBOs during this project. The contribution by GA to this work was supported by a grant from LabEx Osug@2020 (Investissements d'avenir ANR10LABX56).