Volume 10 [2008]

The aim of this study is to estimate future potential changes in duration of extreme dry and
wet spells and rainfall intensity in Eastern Mediterranean. For this purpose, daily
precipitation amounts, deriving from the regional climate model of UK Hadley Centre
HadRM3P have been used for the present (1960-1990) and the future period 2070-2100 on
0.44° x 0.44° latitude by longitude grid. Future data are based on B2 IPCC emission
scenario.
For the identification of precipitation extremes three climatic indices were employed: a)
CWD (Maximum number of consecutive wet days), b) CDD (Maximum number of
consecutive dry days) and c) SDII (quotient of precipitation amount of wet days and the
number of wet days of the period). They were calculated for the present and future period,
on a seasonal and annual basis.
A general future tendency was found towards drier Eastern Mediterranean, with reduced
rainfall intensity. Longer dry spells are expected in all seasons, except autumn, with the
largest increase in the southern part of the area. Extreme wet spells will shorten everywhere
during all seasons, except autumn. Precipitation intensity was found reduced for all seasons
and mostly for summer in South Aegean Sea.

In this study, the variability and trends of the mean annual and seasonal surface air
temperature in Greek peninsula are examined. The climatic data used, concern mean monthly
values of air temperature of 20 meteorological stations of the Hellenic Meteorological Service,
for the period 1951-2000.
The air temperature time series for each station are analyzed, so that the variability and
trends be described. Regarding the annual time series, a cooling trend is observed since the
early 1960’s till the middle of the decade of 1970, when the trend reverses to heating till
nowadays. It is remarkable that the today air temperature levels do not exceed the levels of
the middle of the century. During the winter, it is crystal clear that a cooling trend exists from
the middle of the decade of 1950 to the end of the decade of 1980, especially in the south
region of the country. Afterwards an increasing trend is obvious till nowadays. The pattern in
spring appears a slight heating trend in the northern region of Greece and a cooling trend in
the south. The summer time series are similar to the annual ones, so the contribution of
summer to annual variability is unquestionable. Generally speaking, the air temperature in
autumn follows the same distribution in time.
In the process, the Factor Analysis is applied on the mean annual and seasonal air
temperature and thereafter the regions, within the air temperature covariates, are defined.
Finally, the application of spectral analysis to annual and seasonal air temperature is
regarded necessary so that the periodicities are derived.

In this work preliminary results on the characteristics of the turbulent structure of the Marine
Atmospheric Boundary Layer (MABL) are presented. Measurements used here were
conducted in the framework of the Coupled Boundary Layers Air-Sea Transfer Experiment in
Low Wind (CBLAST-Low) project. A number of in situ (fast and slow sensors) and remote
sensing (SODAR) instruments were deployed on the coast of Nantucket Island, MA, USA.
Measurements of the mean wind, the variances of the three wind components, the
atmospheric stability and the momentum fluxes from the acoustic radar (SODAR) revealed
the variation of the depth, the turbulent characteristics, and the stability of the MABL in
response to the background flow. More specifically, under light south-southwesterly winds,
which correspond to the MABL wind directions, the atmosphere was very stable and low
values of turbulence were observed. Under moderate to strong southwesterly flow, less stable
and neutral atmospheric conditions appeared and the corresponding turbulent quantities were
characterized by higher values. The SODAR measurements, with high temporal and spatial
resolution, also indicated large magnitude of momentum fluxes at higher levels, presumably
associated with the shear forcing near the developed low-level jet.
The measurements from the in-situ instrumentation confirmed that the MABL typically has
small negative momentum and sensible heat fluxes consistent with stable to neutral
stratification while strong diurnal variations were typical for the land surface Atmospheric
Boundary Layer (ABL). The developed internal ABL at the experimental site was in general
less than 10m during the night and could reach 15m heights during the day, particularly under
low-wind conditions.

The political dimension of water becomes highly important not only because of its scarcity, but
also as a result of its sharing across national boundaries. Approximately 40% of the global
population lives in tranboundary water basins, emphasizing the need for cooperation and
harmonization of policies. Hence, the need for “Hydrodiplomacy” rose under the framework of
sustainable development and international cooperation.
Especially in Greece, management of transboundary rivers is of major importance, since
roughly 25% of the country’s renewable resources are “imported” as in four out of the total
five transboundary rivers Greece is the downstream country. The lack of transboundary water
agreements between Greece and its neighboring countries (except with Bulgaria) is affecting
greatly the international cooperation and the status of the water resources. Hence, the
implementation of appropriate methodologies is crucial for the promotion of the integrated
management of these areas. This study refers to five transboundary basins in Northern
Greece and introduces the principles of “Hydrodiplomacy” in their management.