Spatial and Temporal Variations in Precipitation and Aridity Index Series of Turkey
195
Aridity index (PIPE)
Fig. 9. Geographical distribution of aridity index values over Turkey (re-plotted from Tiirke~, 1999)
4.2 Variations and Trends in Precipitation and Aridity Index Series
4.2.1
Annual and Seasonal Precipitation Series
Long-periodfluctuations. Long-term fluctuations in annual and seasonal normalized
precipitation anomaly series of 91 stations are examined by means of the 9-point
Gaussian filter to eliminate the variations shorter than about ten-year periods. Timeseries plots for variations in winter and spring precipitation anomaly series are shown
in Fig. 10.1-2 for the selected IS stations that are representative for all rainfall regime
regions of Turkey. Results from visual examinations on the time-series plots are
summarized as follows.
In winter, a general upward trend with a low-frequency fluctuation dominated by
wetter anomalies are followed by a general downward trend, which is dominated by
longer runs of drier anomalies from the late 1960s at many stations and from the late
1970s at some stations (Fig. 10.1). Stations of the BLS region generally experience
the wet conditions mostly in the late 1930s, 1940s, 1960s, late 1970s and early 1980s,
along with the dry conditions in the 1970s, mid-late 1980s and 1990s. At the stations
of the MED region, wet conditions generally occur in the I 940s, 1960s and early-mid
1980s, whereas dry conditions appear in the early-mid 1930s, around 1970s, late
1980s and 1990s. At the stations of the CMED and the MEDT regions, tluctuation
patterns are quite similar to the patterns of thc MED region, with the wet conditions
in the 1940s, mid 1950s, mid-late 1960s, late 1970s and early 1980s and with the dry
conditions in the early-mid 1930s, early-mid 1970s, mid-late 1980s and 1990s. At the
stations of the CCAN region, wet conditions are evident in the early-mid 1940s,
1960s, mid-late 1970s and early 1980s, and dry conditions are evident in the earlymid 1930s, 1950s, early 1970s, mid-late 1980s and 19905.
195
Aridity index (PIPE)
Fig. 9. Geographical distribution of aridity index values over Turkey (re-plotted from Tiirke~, 1999)
4.2 Variations and Trends in Precipitation and Aridity Index Series
4.2.1
Annual and Seasonal Precipitation Series
Long-periodfluctuations. Long-term fluctuations in annual and seasonal normalized
precipitation anomaly series of 91 stations are examined by means of the 9-point
Gaussian filter to eliminate the variations shorter than about ten-year periods. Timeseries plots for variations in winter and spring precipitation anomaly series are shown
in Fig. 10.1-2 for the selected IS stations that are representative for all rainfall regime
regions of Turkey. Results from visual examinations on the time-series plots are
summarized as follows.
In winter, a general upward trend with a low-frequency fluctuation dominated by
wetter anomalies are followed by a general downward trend, which is dominated by
longer runs of drier anomalies from the late 1960s at many stations and from the late
1970s at some stations (Fig. 10.1). Stations of the BLS region generally experience
the wet conditions mostly in the late 1930s, 1940s, 1960s, late 1970s and early 1980s,
along with the dry conditions in the 1970s, mid-late 1980s and 1990s. At the stations
of the MED region, wet conditions generally occur in the I 940s, 1960s and early-mid
1980s, whereas dry conditions appear in the early-mid 1930s, around 1970s, late
1980s and 1990s. At the stations of the CMED and the MEDT regions, tluctuation
patterns are quite similar to the patterns of thc MED region, with the wet conditions
in the 1940s, mid 1950s, mid-late 1960s, late 1970s and early 1980s and with the dry
conditions in the early-mid 1930s, early-mid 1970s, mid-late 1980s and 1990s. At the
stations of the CCAN region, wet conditions are evident in the early-mid 1940s,
1960s, mid-late 1970s and early 1980s, and dry conditions are evident in the earlymid 1930s, 1950s, early 1970s, mid-late 1980s and 19905.