192
Murat Tiirke~
cent along the Black Sea coast (Fig. 5d). A seasonality index highlights this contrast
of the precipitation amounts between the seasons over different regions of Turkey.
The seasonality index (Sf) at a station is computed by summation of the absolute
deviations of mean monthly precipitation from the overall mean and dividing it to the
long-term average annual precipitation (Glantz 1987; Tiirke~ 1998a). Areas with Sf
values greater than 0.55 generally have a Mediterranean type rainfall regime, which
coincide with the Mediterranean and Continental Mediterranean regions of Turkey
(Fig. 6). Contribution of the mean spring precipitation amount to the mean annual
precipitation total ranges between about 30 per cent and 35 per cent in the majority
of the stations of the Continental Mediterranean region. If the contribution of spring
precipitation is taken into consideration, it is seen that seasonality of most stations
over the Continental Mediterranean region, however, differs somewhat from those
over the Mediterranean region. This percentage pattern of the spring precipitation is
similar to the pattern that is found over the continental interior regions rather than that
of the Mediterranean region. On the other hand, Sf values smaller than about 0.35
generally correspond to a uniform and quite uniform rainfall regime over the Black
Sea region and the northern Marmara, respectively.
4.1.4 Precipitation Variability
The spatial distribution of variability in annual and seasonal precipitation amounts
was examined by a measure termed the coefficient of variation (CV) and shown in
Fig. 7 and 8, respectively. The CV is calculated by expressing the standard deviation
as a percentage of the long-term average. Variability of the annual precipitation
decreases from the southern part of the country, which is generally characterized by
the Mediterranean rainfall regime, to the Black Sea coast, where a uniform rainfall
regime is dominant (Fig. 7). The CVs are greater than 25 per cent over a great part of
"
Seasonality index
Fig. 6. Geographical distribution of the Sesonality Index (SI) of precipitation over Turkey (replotted from Tiirke~ 1999)
Murat Tiirke~
cent along the Black Sea coast (Fig. 5d). A seasonality index highlights this contrast
of the precipitation amounts between the seasons over different regions of Turkey.
The seasonality index (Sf) at a station is computed by summation of the absolute
deviations of mean monthly precipitation from the overall mean and dividing it to the
long-term average annual precipitation (Glantz 1987; Tiirke~ 1998a). Areas with Sf
values greater than 0.55 generally have a Mediterranean type rainfall regime, which
coincide with the Mediterranean and Continental Mediterranean regions of Turkey
(Fig. 6). Contribution of the mean spring precipitation amount to the mean annual
precipitation total ranges between about 30 per cent and 35 per cent in the majority
of the stations of the Continental Mediterranean region. If the contribution of spring
precipitation is taken into consideration, it is seen that seasonality of most stations
over the Continental Mediterranean region, however, differs somewhat from those
over the Mediterranean region. This percentage pattern of the spring precipitation is
similar to the pattern that is found over the continental interior regions rather than that
of the Mediterranean region. On the other hand, Sf values smaller than about 0.35
generally correspond to a uniform and quite uniform rainfall regime over the Black
Sea region and the northern Marmara, respectively.
4.1.4 Precipitation Variability
The spatial distribution of variability in annual and seasonal precipitation amounts
was examined by a measure termed the coefficient of variation (CV) and shown in
Fig. 7 and 8, respectively. The CV is calculated by expressing the standard deviation
as a percentage of the long-term average. Variability of the annual precipitation
decreases from the southern part of the country, which is generally characterized by
the Mediterranean rainfall regime, to the Black Sea coast, where a uniform rainfall
regime is dominant (Fig. 7). The CVs are greater than 25 per cent over a great part of
"
Seasonality index
Fig. 6. Geographical distribution of the Sesonality Index (SI) of precipitation over Turkey (replotted from Tiirke~ 1999)