Thermal flows along the south-eastern Adriatic

1
Thermal flows along the south-eastern Adriatic

• Maja Telišman Prtenjak Sanda Ðivanovic
• Department of Geophysics, Faculty of Science,
  University of Zagreb, Croatia
• Email telisman_at_irb.hr

EGU2009-1561
RESULTS

• CONCLUSIONS
• Airports are located in the area which is under
  significant influence of the convergence zones
  (as the result of the merged thermal
  circulations)
• considerably channeling of the surface wind
  occurred in sea passages as well over the Neretva
  river
• Formation of several mesoscale eddies (e.g. over
  the island of Šolta near Split-airport and in the
  lee the island of Vis)

Model vs. measurements
Figure 2. Vertical comparison between modeled
(pink) and measured (blue) wind at Split
airport on 24 April 2006. Wind (a) speed and (b)
direction at 0400 LST and wind (c) speed and (d)
direction at 1500 LST during land/sea breeze
event. Position of the measuring site is
indicated in Fig 1.Vertical wind measurements
were performed by Scintec MFAS sodar with the
measurements range from 30 to 700 m. Averaging
and output intervals were set to 10 minutes and
space resolution is 20 m. The model results are
in a good agreement with the sodar results.
Table 1. Calculated statistic indices during
24-25 April 2006 RMSE (root mean square error),
d-index of agreement and MAE (mean absolute
error) reflect the degree to which measurements
are accurately estimated by the model. The
calculations were made for wind speed, wind
direction and temperature at 9 stations with 24
hour measurements. Wind direction and 2-m
temperature showed reasonable model performance,
although somewhat poorer agreement was obtained
for the wind speed (e.g. Split, Makarska, Komiza
and Dubrovnik)
1500 LST
0400 LST
wind direction wind speed
2-m temperature

• AIM MOTIVATION
• Klaic et al. (2009) examined sea/land breeze and
  etesian interaction along the Adriatic.
• However, a spatial distribution of the
  small-scale features in the wind field during sea
  breeze event along the south-eastern Adriatic
  (SEA) is still unknown.
• In SEA, the existed sea/land breeze knowledge is
  predominantly climatological. Only certain
  number of the forecast sites were analyzed
  (Lukšic, 2004 Pandžic and Likso, 2005).
• Since several airports (Split-airport,
  Brac-airport and Dubrovnik-airport) are located
  in this area, the aim is to detect possible
  (sometimes very dangerous) convergence zone (and
  other wind forms).

Nighttime surface wind field
0300 LST
Daytime surface wind field
Modeled 10-m wind field on 24 April 2006
(b) 1400 LST

• During the nighttime, weak land breeze interacted
  with downslope wind reaching 3.4 m s-1.
• The strongest channeling between Mosor and
  Biokovo mountains

(c) 1400 LST
(a) measurements

• Specific features in the surface wind field was
• the formation of the mesoscale eddy above the
  island of Šolta within SC and BC. This vortex
  with the offshore flow formed (relatively weak)
  nighttime convergence zone near Split-airport.
• Above Brac-airport weak convergence zone was
  developed.
• atmospheric vortex in the lee of the island of
  Vis.

Šolta
(d) 1400 LST
(e) 1700 LST
Figure 4. Same as in Fig. 3 except for 0300 LST
on 24 April 2006.
Figure 1. (a) Configuration of nested model grids
over the study area on the south-eastern Adriatic
coast. Frames indicate the coarse-grid (1),
mid-frame (2) and fine-grid (3) WRF model
domains, respectively. (b) The fine-grid domain
with the positions of measuring sites hourly
meteorological measurements (green circles) 1
Šibenik, 2 Knin, 3 Split, 4 Makarska, 5
Hvar, 6 Komiža, 8 Ploce and airport stations
Split-airport, Brac-airport and Dubrovnik-airport
(red circles). Topography contours are given for
every 100 m between at 0 and 2000 m.
Abbreviations are SC Split channel, BC Brac
channel, HC Hvar channel, VC Vis channel, KC
Korcula channel, NC Neretva channel.
Acknowledgements This work has been supported
by the Ministry of Science, Educational and Sport
(BORA project No. 119-1193086-1311).
References Klaic, Z.B., Pasaric, Z., Tudor,
M., 2009. On the interplay between sea-land
breezes and etesian winds over the central
Adriatic. J. Marine Syst. (in press). Lukšic,
I., 2004. Neki odnosi izmedu zmorca, etezija i
atmosferskog poremecaja. Hrv. meteorol. casopis,
39 121133. (in Croatian) Michalakes J, Dudhia
J, Gill D, Henderson T, Klemp J, Skamarock W,
Wang W. 2004. The Weather Research and
Forecasting Model software architecture and
performance. In 11th ECMWF Workshop on the use of
High Performance Computing in Meteorology, edited
by George Mozdzynski. Reading. U.K. Pandžic,
K., Likso, T., 2005. Eastern Adriatic typical
wind field patterns and large-scale atmospheric
conditions. Int. J. Climatol., 25 81-98.
Figure 3. (a) 10-m wind vectors (m s-1) from
meteorological (Fig. 1) and climatological
stations at 1400 LST for 24 April 2006 (b)
modeled WRF wind field in the fine model domain
at 1400 LST (c) the modeled wind field above
Neretva river at 1400 LST (d) the modeled wind
field above the island of Brac at (d) 1400 LST
and (e) at 1700 LST. The wind vectors are given
at a horizontal resolution of 3 km and the wind
speed is depicted by filled areas (scale legend
on the right) with a 1 m s-1 interval.

• MODEL SIMULATION SPECIFICATIONS
• WRF-ARW (version 2.2) 3D nonhydrostatic
  mesoscale model (e.g. Michalakes et al., 2004)
• a two-way nested configuration with grid spacing
  of 10.8 km, 3.6 km and 1.2 km in model domains
• (on the Lambert conformal projection) (Fig. 1).
• 80 terrain-following coordinate levels with the
  lowest level at about 25 m.
• Initial and boundary conditions from ECMWF at
  the standard pressure levels every 6 h
• Simulations of 65 h were performed from 0700 h
  of 28 June 2004 until midnight of 30 June 2004.
• WRF dynamic and physical options for all
  domains
• a Mellor-Yamada-Janjic scheme for the PBL
• a rapid radiative transfer model for the
  longwave radiation and a Dudhia scheme for
• shortwave radiation
• a single-moment 3-class microphysics scheme with
  ice and snow processes
• the Eta surface layer scheme based on MO theory
• a five-layer thermal diffusion scheme for the
  soil temperature.
• the Betts-Miller-Janjic cumulus parameterization
  is only used on the coarse domain

• During the day, after 0900 LST, sea breeze
  developed as well as upslope wind over the
  mountainous coastline
• They superimposed with the strength up to 6 m
  s-1 at 1400 LST.
• Specific features in the surface wind field
  were
• convergence zones e.g. near Split-airport
  (stronger) and above the island of Brac (weaker)
  close to the Brac-airport that moved eastward and
  southward, respectively. Vertical velocities were
  over 1 m s-1
• canalizing flows trough the mountainous gaps and
  sea channels (HC, BC, SC, NC) as well as above
  Neretva river (Fig. 3c)
• atmospheric vortex in the lee of the island of
  Vis (Fig. 3e).