The Arctic Atmospheric Boundary Layer (ABL) structure depends mostly on the stability condition of the atmosphere, the surface processes and the orography of the site. The complex interactions between turbulence and radiation due to the presence of the Arctic clouds, haze and sea ice variation, make the parameterisation of the different ABL processes even more difficult. It is worth mentioning that the turbulent energy fluxes are larger in the marginal ice zones, where the sea surface is partially covered by sea ice floes. Under these conditions the surface temperature is extremely inhomogeneous and classical boundary layer schemes fail to describe the area averaged turbulent fluxes adequately. This deficit can hardly be overcome only by using ground based turbulence measurements, which may reflect local effects on the flow and do not cover a wide range of surface and atmospheric conditions. Long time series of measurements of physical quantities at appropriate upper levels are then needed to understand the complex phenomenology that may occur in these marginal ice zones. One of the most important advantages of Ny-Ålesund is the possibility to perform continuous measurements both at sea level and at 480 m of altitude. Since height of the ABL in the Arctic regions is typically below 500 m, this means that it's possible to perform measurements inside and outside the ABL for most part of the year, highlighting the importance of local surface processes with respect to vertical exchange and advective processes at several temporal and spatial scales.
Our objective is to provide continuous measurements at the sea level and in the first 30-50 m, to complement those running at Zeppelin station by Swedish and Norwegian research groups. In particular the interest for the proposed ABL observational study are:
- the continuous monitoring of the thermal and dynamical characteristics of the turbulence within the PBL and study the annual evolution in particular during the seasonal transition periods.
- The study of the fine structure of the ABL turbulence by means of the atmospheric parameter profiles.
- The monitoring of the stability and the boundary layer structure.
- The measure of the wind dynamics at different height to study the interaction between local and synoptic circulation.
- The study of the dependence of surface temperature and wind direction on cloud coverage.
- The study of the behaviour of some micrometeorological parameters in connection with the general flow pattern, the orography and characteristics of the area.
The surface layer processes are investigated using conventional and fast response sensors installed on the CCTower. Sonic/standard anemometers, aspirated temperature sensors and fast hygrometers installed, in a logarithmic array, at different height, on the tower allow the continuous monitoring and study the fine structure of the turbulence in the ABL. The Arctic ABL characteristics over Ny-Ålesund are investigated by remote sensing technique as well as by in situ measurements. Vertical profiles of the meteorological parameters (temperature, wind speed and direction, humidity and pressure) are provided also during field campaign by direct measurements with tethersounding, and takes profit of lidar measurements carried out within the frame of the CCT project and by other groups at Ny-Ålesund. These measurements give information, up to several hundreds meters, of thermal structure, wind, temperature and aerosol profiles respectively, to drawn the evolution of the ABL, and its seasonal variation. Strong convection conditions, arising during spring, when the sea ice starts to break, are also studied, in relation with the variability of the cloudiness and with the anomalous warmings observed in the past. The Microwave Temperature Profile (MTP5) allows the characterization of the thermal structure of the low atmosphere with a high vertical and temporal resolution and the quantitative definition of the processes and the characteristics of the ABL about the inversion height observed by sodar.
