TRANSBOUNDARY TRANSPORT OF AIR POLLUTANTS SYSTEM WITH THE COMBINED USE OF SATELLITE DATA, GROUND BASED DATA AND NUMERICAL MODELS Proposal Acronym: TRANSAT

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AN INVESTIGATION ON THE FACTORS INFLUENCING
THE RURAL SURFACE OZONE LEVELS IN THE EASTERN
MEDITERRANEAN (MALTA, GREECE, CYPRUS)   P. D.
Kalabokas (1), R. Ellul (2), E. Gerasopoulos (3),
N. Mihalopoulos (3), S. Kleanthous (4) and C.
C. Repapis (1)   (1) Academy of Athens, Research
Center for Atmospheric Physics and Climatology,
Athens, Greece (2) Department of Physics,
University of Malta, Malta (3) Environmental
Chemical Processes Laboratory, Department of
Chemisty, University of Crete, Heraklion,
Greece (4) Ministry of Labor and Social
Insurance, Labor Department, Nicosia,
Cyprus Abstract An investigation on the
origins of the observed variations in the Eastern
Mediterranean summer (JJA) rural surface ozone is
performed, following observations showing
comparable ozone levels between Central Greece
and the Crete Island, being by 15-20 higher than
the corresponding levels in Malta and Cyprus
(Fig. 1, Tab. 1). For this purpose the
measurements of the first 3-year period
(1998-2000) of the common operation of the
following four Eastern Mediterranean stations are
analyzed Giordan Lighthouse-Gozo, Malta
Aliartos-Central Greece, Finokalia-Crete, Greece
and Ag. Marina, Cyprus. All the above stations
experience, in principle, similar weather
conditions during summer regarding the high
temperatures and the strong solar irradiation.
For obtaining representative boundary layer air
the mid-day ozone averages (1200 1800) were
used.
 
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Fig. 1
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Tab. 1a (left up) Distribution statistics of the
rural summer (JJA) afternoon ozone measurements
in the Eastern Mediterranean for the year 1998.
Tab1b (right up) Average values of the rural
summer (JJA) afternoon ozone measurements in the
Eastern Mediterranean stations for the year 1998
a). Total averages b). Average ozone value of the
20 of the days with the highest values and c).
Average ozone value of the 20 of the days with
the lowest values. Tab 1c (left down)
Distribution statistics of the rural summer (JJA)
afternoon ozone measurements in the Eastern
Mediterranean for the years 1998, 1999 and
2000. Tab 1d (right down) Average values of the
rural summer (JJA) afternoon ozone measurements
in the Eastern Mediterranean stations for the
years 1998, 1999 and 2000 a). Total averages b).
Average ozone value of the 7 of the days with
the highest values and c). Average ozone value of
the 7 of the days with the lowest values.
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Fig. 2a (left) Composite weather map of
geopotential heights at 850 hPa (lower panel,
isopleths of 10m), and 700 hPa (upper panel,
isopleths of 10m) of the 7 of the days (20 days)
with the highest ozone values (1200 1800) in
Gozo, Malta in the summers (JJA) of
1998-2000. Fig. 2b (right) Composite weather map
of geopotential heights at 850 hPa (lower panel,
isopleths of 10m), and 700 hPa (upper panel,
isopleths of 15m) of the 7 of the days (20 days)
with the lowest ozone values (1200 1800) in
Gozo, Malta in the summers (JJA) of 1998-2000.
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Fig. 3a (left) Composite weather map of
geopotential heights at 850 hPa (lower panel,
isopleths of 10m), and 700 hPa (upper panel,
isopleths of 15m) of the 7 of the days (18 days)
with the highest ozone values (1200 1800) in
Finokalia, Crete, in the summers (JJA) of
1998-2000. Fig. 3b (right)Composite weather map
of geopotential heights at 850 hPa (lower panel,
isopleths of 10m), and 700 hPa (upper panel,
isopleths of 15m) of the 7 of the days (18 days)
with the lowest ozone values (1200 1800) in
Finokalia, Crete in the summers (JJA) of
1998-2000.
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Fig. 4a (left) Composite weather map of
geopotential heights at 850 hPa (lower panel,
isopleths of 10m), and 700 hPa (upper panel,
isopleths of 15m) of the 7 of the days (19 days)
with the highest ozone values (1200 1800) in
Ag. Marina, Cyprus, in the summers (JJA) of
1998-2000. Fig. 4b (right)Composite weather map
of geopotential heights at 850 hPa (lower panel,
isopleths of 5m), and 700 hPa (upper panel,
isopleths of 10m) of the 7 of the days (19 days)
with the lowest ozone values (1200 1800) in
Ag. Marina, Cyprus, in the summers (JJA) of
1998-2000
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Fig. 5a (left) Average composite weather map of
geopotential heights at 850 hPa (isopleths of
10m), for the summers (JJA) of 1998, 1999 and
2000  Fig. 5b (right)Average summer (JJA)
absolute (blue in ppb) and relative (brown in )
ozone difference between Heraklion and Vienna in
1996-1997 (18 profiles), (Kalabokas et al., EGU
2004).
REFERENCES Cyprus report (2000), Air quality
measurements in Nicosia (in Greek), Ministry of
Labor and Social Insurance, Labor Department,
Nicosia, Cyprus. Ellul R. and Nolle M. (2003),
Long term trends of trace gas concentrations in
the Central Mediterranean as measured at the GAW
station on the Island of Gozo, TOR-2 (EUROTRAC-2)
Final report, GSF, Munich, Germany. Kalabokas
P.D., Viras L. G., Bartzis J. G. and Repapis C.C.
(2000), Mediterranean rural ozone characteristics
around the urban area of Athens. Atmos. Environ.,
34, 5199-5208. Kalabokas P. D. and Repapis C.C.
(2004), A climatological study of rural surface
ozone in central Greece. Atmos. Chem. and Phys.,
4, 1139-1147. P. D. Kalabokas, A. Volz-Thomas,
J.-P. Cammas, V. Thouret and C. C. Repapis
(2004), Comparison of vertical tropospheric
summertime ozone measurements over the Aegean sea
and central Europe, European Geosciences Union
(EGU), 1st General Assembly, Nice, France, 25-30
April 2004 Kalabokas P.D., G. Kouvarakis, N.
Mihalopoulos, R. Ellul, S. Kleanthous and C. C.
Repapis (2005). Rural surface ozone levels in the
Eastern Mediterranean (Malta, Greece, Cyprus),
EGU-General Assembly 2005, Vienna, Austria, 24-29
April 2005 Kouvarakis G., Tsigaridis, K.,
Kanakidou, M. and Mihalopoulos, N. (2000),
Temporal variations of surface regional
background ozone over Crete Island in the
southeast Mediterranean., J. Geoph. Res., 105,
D4, 4399-4407. Kouvarakis G., Vrekoussis, M.,
Mihalopoulos, N., Kourtidis, K., Rappenglueck,
B., Gerasopoulos E., and Zerefos, C. (2002),
Spatial and temporal variability of tropospheric
ozone in the boundary layer above the Aegean Sea.
J. Geoph. Res., 107(D18), 8137,
doi10.1029/2000JD000081,. Nolle M, Ellul R.,
Heinrich G. and Gusten H. (2002), A long-term
study of background ozone concentrations in the
Central Mediterranean-Diurnal and seasonal
variations on the island of Gozo, Atmos.
Environ., 36, 1391-1402. Volz-Thomas A. et al.
(2003), Tropospheric ozone and its control, In
Synthesis and Integration Report, EUROTRAC-2,
GSF, Munich, Germany.
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CONCLUSION The data-analysis is mainly based on
the classification and grouping of meteorological
conditions for the highest and the lowest ozone
days (the 7 for each case), for the stations of
Malta, Crete and Cyprus by plotting the
corresponding NCAR/NCEP average weather maps
(Figs. 2-4). It comes out that a main factor
leading to high tropospheric ozone values in the
area is an anticyclonic influence. When a high
pressure system prevails in summer over the area
of a station it is expected to create low
dispersion conditions in the boundary layer and
also induce northerly atmospheric flow advecting
southwards air masses affected from the pollutant
emissions of Western, Central or Eastern Europe,
under favorable summer conditions for
photochemical ozone production. These ozone
amounts are added up in an already high ozone
background throughout the troposphere associated
with summer anticyclones. On the other hand, the
lowest ozone levels, particularly in Crete and
Cyprus stations, are associated with an extension
to the west of the Middle-East low and weak
pressure gradients over the Eastern Mediterranean
and an upper air trough in the North Eastern
Europe. The presence of low-pressure systems
(poor in tropospheric ozone) is associated with
uplifting air movements and consequently high
pollutant dispersion conditions and also with
westerly (cleaner) atmospheric airflows. In
addition, the lowest ozone levels in Malta are
associated with a southwards retreat of the North
African high pressure system giving way to
westerly flow in Western Mediterranean. The
high frequency of the above-described
meteorological situation influencing surface
ozone in Eastern Mediterranean in summer is
depicted on the average summer composite weather
maps for the period 1998-2000 at the 850hPa (Fig.
5a). The above findings are strengthened if the
results of a parallel study on summer vertical
tropospheric ozone profiles in the framework of
the MOZAIC project are taken into account, as a
difference between the Aegean and Central
European ozone average values, at all standard
pressure levels in the troposphere, was observed
which was maximized at the lower levels, 1000 hPa
(1000-950) and 900 hPa (950-850), (Fig. 5b). The
observed higher ozone differences in the Aegean
boundary layer in combination with the strong and
persistent northerly flow and the absence of
important local ozone precursor emissions is an
indication of ozone photochemical production
associated with long-range transport, processes
significantly enhanced under anticyclonic
conditions.