Plenary Lecture

Towards a better understanding of the mean and turbulent structure of the Atmosphere over the sea

COSTAS G. HELMIS
Department of Applied Physics, Faculty of Physics
National and Kapodistrian University of Athens
Building PHYS-5, University Campus, 157 84 Athens, Greece
GREECE
chelmis@phys.uoa.gr

Abstract: In recent years the study of the vertical structure of the Marine Atmospheric Boundary Layer (MABL) has been the main topic of interest for atmospheric physics. The study of the coastal Atmospheric Boundary Layer (ABL) has received considerable attention, since uncertainties related to the parameterization of the mass, heat and moisture exchange between the air and sea are existed and experimental studies reveal large data scatter. Moreover, certain atmospheric phenomena such as the development of Low Level Jet (LLJ) or intensified thermal stratifications are associated with the marine ABL. The characteristics of the ABL in maritime areas exhibited strong variations in space and time due to the land/sea surface forcing and the modification of the large and meso-scale wind flow field related to terrain and surface thermal effects. The Coupled Boundary Layers Air-Sea Transfer Experiment in Low Winds (CBLAST-Low) project aims to the understanding of the air-sea interaction and the coupled atmospheric and oceanic boundary layer dynamics at low wind speeds. As part of the CBLAST-Low experiment, extensive ground-based measurements were performed during summer 2003, on Nantucket Island, MA, USA. One of the main objectives of these measurements was the detailed study of the mean and turbulent vertical structure of the MABL
In this invited talk a review regarding the structural characteristics of the mean and turbulent MABL will be given, based on the measurements of the experimental campaign. The measurements of the mean wind, turbulence variances and fluxes from the operated SODAR system revealed the variation of the boundary layer stability as well as the turbulence characteristics in response to the background flow. Large values of the momentum fluxes at higher levels were estimated, presumably associated with the shear forcing near the very frequently developed marine LLJ, due mainly to the inertial oscillation mechanism. The understanding of the possible cause for the development and evolution of the LLJ, which is associated with a strong stability of the MABL lower layer and the confirmation of this mechanism from experimental measurements and theoretical considerations, will also be given. The SODAR measurements, with high time and space resolution, and the other relevant measurements from this experimental campaign give complementary information in order to understand the momentum transport and the TKE balance of the jet-related boundary layer under different meteorological conditions.

Keywords: Fluxes, SODAR, marine Atmospheric Boundary Layer, turbulence, parameterization, Low-Level Jet

Short Biography of the Speaker:
Studies First Degree: BSc, University of Athens, Faculty of Physics, 1972
Post Graduate Titles: MSc in Electronics, University of Athens, 1975
MSc in Automation, University of Athens, 1976
PhD in Physics, University of Athens, 1981

Academic Positions:
Head of the Dept. of Applied Physics, Faculty of Physics, University of Athens.
Assoc. Professor, Dept. of Applied Physics, Faculty of Physics, University of Athens.

Fields of Scientific activities:
- Atmospheric Physics
- Development of instrumentation for remote and in-situ measurements
- Air Pollution meteorology
- Indoor and Outdoor Air Pollution
He has 92 publications in journals, 167 announcements in conference proceeding, 86 participations in technical reports and 20 other publications. He has participated in the EEA on air quality (ETC/AQ) during 1996-2001 and in 89 research projects, in 37 of the above he acted as the Principal Investigator.