Abstract:
The goal of this study was to estimate the sensitiv
ity of reference evapotranspiration
(
ET
0
) to changes in meteorological parameters in the Ca
spian region. Long-term
meteorological data (1961-2008) were obtained from
three synoptic meteorological
stations. The region was primarily classified into
three climatic zones, based on De
Martonne climate classification. The Penman–Monteit
h equation was applied to calculate
the
ET
0
and the sensitivity of
ET
0
was studied in terms of changes in air temperature,
solar radiation, wind speed and vapor pressure with
in a possible range of ±20%
from the
normal long-term meteorological parameters. The res
ults indicated that the Caspian
region could be classified into the three climatic
classes: Mediterranean, humid, and
extremely humid. During the last half century, mete
orological parameters and, in
particular, temperature of the Caspian region has c
hanged dramatically and the
ET
0
has
increased as a result of climate change. The study
suggests that an increase in
temperature by 20%
(approximately 3.3 ºC) will result in
ET
0
demand increase by 16%.
Changes in vapor pressure (20%
) represented the highest inverse effect on annual
ET
0
throughout the Caspian region (-19%
in the Mediterranean, and -30%
in other climates).
The Mediterranean and extremely humid climates of t
he Caspian region showed an
increase of 2 and 5%
of the total
ET
0
,
respectively, in response to 20%
change in the wind
speed. It is quite essential for managers to take i
nto consideration the expected change in
evapotranspiration owing to global warming while pl
anning for development of artificial
and natural ecosystems in the Caspian region.
Keywords
: Climate change, Meteorological parameters, Penman
-Monteith.
