Boundary layer structure and decoupling from synoptic scale flow during NAMBLEX E. G. Norton1, G. Vaughan1, J. Methven2, H. Coe1, B. Brooks3, M. Gallagher1, and I. Longley1 1School of Earth, Atmospheric and Environmental science, University of Manchester, Building Sackville Street, Manchester, M60 1QD, UK 2Department of Meteorology, University of Reading, P.O. Box 243, Earley Gate, Reading, RG6 6BB, UK 3School of the Environment, University of Leeds, Leeds, LSJ 9JT, UK
Abstract. This paper presents an overview of the meteorology and planetary
boundary layer structure observed during the NAMBLEX field campaign
to aid interpretation of the chemical and aerosol measurements. The
campaign has been separated into five periods corresponding to the
prevailing synoptic condition. Comparisons between meteorological
measurements (UHF wind profiler, Doppler sodar, sonic aneometers
mounted on a tower at varying heights and a standard anemometer) and
the ECMWF analysis at 10m and 1100 m identified days when the
internal boundary layer was decoupled from the synoptic flow aloft.
Generally the agreement was remarkably good apart from during period
one and on a few days during period four when the diurnal swing in
wind direction implies a sea/land breeze circulation near the
surface. During these periods the origin of air sampled at Mace Head
would not be accurately represented by back trajectories following
the winds resolved in ECMWF analyses. The wind profiler observations
give a detailed record of boundary layer structure including an
indication of its depth, average wind speed and direction.
Turbulence statistics have been used to assess the height to which
the developing internal boundary layer, caused by the increased
surface drag at the coast, reaches the sampling location under a
wide range of marine conditions. Sampling conducted below 10 m
will be impacted by emission sources at the shoreline in all wind
directions and tidal conditions, whereas sampling above 15 m is
unlikely to be affected in any of the wind directions and tidal
heights sampled during the experiment.
Citation: Norton, E. G., Vaughan, G., Methven, J., Coe, H., Brooks, B., Gallagher, M., and Longley, I.: Boundary layer structure and decoupling from synoptic scale flow during NAMBLEX, Atmos. Chem. Phys., 6, 433-445, doi:10.5194/acp-6-433-2006, 2006.