250
S. Ferrarese et al.
tinental ice (in our case Hells Gâte, an ice shelf about 20 km from the Italian
Summer Station of Terra Nova Bay) were evaluated with two-fold aims: firstly, to
investigate the transfer of sensible and latent heat energy at the air-ice surface
boundary and the rôle it plays in determining the évolution of the atmospheric
surface layer, so as to better understand the relationship between the dynamics of
this last and katabatic winds; secondly, to provide useful information on the existing links between these events, offshore mesoscale cyclogenesis [3] and the
polynya of Terra Nova Bay [4]. The measurements of sensible and latent heat fluxes over the Hells Gâte ice sheet were obtained by using two masts 10 m high and 5
km apart.both equipped with fast and slow response sensors. Each mast was operated by two teams, namely the Atmospheric Group of the Department of General
Physics, Turin University, Italy (GEOFIT), and the Institute of Atmospheric Physics
of the Italian National Research Council, Rome, Italy (IFA-CNR). The experiments,
the instrument characteristics and data validation are described in Section 2, while
in Section 3 the direct évaluation method of turbulent heat fluxes is introduced. In
Section 4 the heat energy balance is presented and, finally, in Section 5, the main
results of the présent study are summarized and discussed.
2 Experimental Set-up, Data Validation and Analysis
The instruments used for the Antarctic expéditions were installed on two masts,
positioned at a distance of about 5 km from each other (Fig. 1) and aligned nearly perpendicularly to the continental ice-sea front. On the first mast, located near
the continental ice front (coastal mast), the following instruments were placed at
different heights: an ultrasonic Kaijo Denki anemometer-thermometer at 10 m,
three Sitep thermometers, igrometers, and anemometers at 10, 5 and 2.5 m
respectively, a Sitep solarimeter at 2 m, a Sitep barometer at 2 m and three Sitep
thermistors buried in the ice at -0.5, -0.25 and 0 (surface) m. On the second mast
(inner mast), the following instruments were placed at two heights: two ultrasonic Gill Soient anemometers at 10 and 5 m respectively and a fast Campbell kripton igrometer at 10 m.
The ultrasonic Kaijo Denki anemometer-thermometer recorded the three
components of the wind velocity and sonie température (Ts) at 20 Hz, allowing
the évaluation of turbulent sensible heat flux. The Sitep anemometers, based on
solid-state sensors to guarantee the operativeness even in extreme meteorological
conditions, sampled at 4 Hz, while the other instruments on the first mast sampled at 1 cycle/min. The two ultrasonic Gill anemometers sampled the three components of the wind speed and the velocity of sound at 21 Hz. The fast kripton
igrometer sampled also at 21 Hz and was syncronized with the nearby Gill
anemometer, installed at 10 m on the same mast. Table 1 summarizes the list of
deployed instruments, their main characteristics and location.
For these instruments, the conversion of the velocity in an orthogonal coordinate System, the dérivation of the sonie température from the velocity of
sound and the correction of the tilt error hâve been made by a suitable software
that uses a three-dimensional rotation of coordinates [5-7]. From these data,it is
possible to calculate the turbulent sensible heat fluxes at 10 m on the first mast
S. Ferrarese et al.
tinental ice (in our case Hells Gâte, an ice shelf about 20 km from the Italian
Summer Station of Terra Nova Bay) were evaluated with two-fold aims: firstly, to
investigate the transfer of sensible and latent heat energy at the air-ice surface
boundary and the rôle it plays in determining the évolution of the atmospheric
surface layer, so as to better understand the relationship between the dynamics of
this last and katabatic winds; secondly, to provide useful information on the existing links between these events, offshore mesoscale cyclogenesis [3] and the
polynya of Terra Nova Bay [4]. The measurements of sensible and latent heat fluxes over the Hells Gâte ice sheet were obtained by using two masts 10 m high and 5
km apart.both equipped with fast and slow response sensors. Each mast was operated by two teams, namely the Atmospheric Group of the Department of General
Physics, Turin University, Italy (GEOFIT), and the Institute of Atmospheric Physics
of the Italian National Research Council, Rome, Italy (IFA-CNR). The experiments,
the instrument characteristics and data validation are described in Section 2, while
in Section 3 the direct évaluation method of turbulent heat fluxes is introduced. In
Section 4 the heat energy balance is presented and, finally, in Section 5, the main
results of the présent study are summarized and discussed.
2 Experimental Set-up, Data Validation and Analysis
The instruments used for the Antarctic expéditions were installed on two masts,
positioned at a distance of about 5 km from each other (Fig. 1) and aligned nearly perpendicularly to the continental ice-sea front. On the first mast, located near
the continental ice front (coastal mast), the following instruments were placed at
different heights: an ultrasonic Kaijo Denki anemometer-thermometer at 10 m,
three Sitep thermometers, igrometers, and anemometers at 10, 5 and 2.5 m
respectively, a Sitep solarimeter at 2 m, a Sitep barometer at 2 m and three Sitep
thermistors buried in the ice at -0.5, -0.25 and 0 (surface) m. On the second mast
(inner mast), the following instruments were placed at two heights: two ultrasonic Gill Soient anemometers at 10 and 5 m respectively and a fast Campbell kripton igrometer at 10 m.
The ultrasonic Kaijo Denki anemometer-thermometer recorded the three
components of the wind velocity and sonie température (Ts) at 20 Hz, allowing
the évaluation of turbulent sensible heat flux. The Sitep anemometers, based on
solid-state sensors to guarantee the operativeness even in extreme meteorological
conditions, sampled at 4 Hz, while the other instruments on the first mast sampled at 1 cycle/min. The two ultrasonic Gill anemometers sampled the three components of the wind speed and the velocity of sound at 21 Hz. The fast kripton
igrometer sampled also at 21 Hz and was syncronized with the nearby Gill
anemometer, installed at 10 m on the same mast. Table 1 summarizes the list of
deployed instruments, their main characteristics and location.
For these instruments, the conversion of the velocity in an orthogonal coordinate System, the dérivation of the sonie température from the velocity of
sound and the correction of the tilt error hâve been made by a suitable software
that uses a three-dimensional rotation of coordinates [5-7]. From these data,it is
possible to calculate the turbulent sensible heat fluxes at 10 m on the first mast