196
Murat Ttirke~
Spring series generally indicate a high-frequency variation with an unchanged
mean at some stations and about slightly increasing mean at many stations (Fig. 10.2).
Stations of the BLS region generally experience increased precipitation from the early
1940s to mid-1960s. Thereafter there is a general decrease. Stations of the MED
region generally depict wet conditions in the late 1940s, early 1950s, 1970s and
1980s, along with the dry conditions in the 1940s and 1990s. Stations over the CMED
region show a general increasing trend, from the mid-1940s to the mid-1970s, with
the wet conditions in the late 1940s, early-mid 1950s, late 1960s and 1970s.
Thereafter drier conditions dominate. At the stations of the CCAN region, wet
conditions generally dominate over the early 1950s, mid-late 1960s and 1970s, along
with the dry conditions over the 1930s, early-mid 1940s, mid-late 1950s and early
1960s.
Summer rainfall series generally tend to increase at some stations and to show
unchanged situation at many stations. The longer runs of negative anomalies are a
dominant characteristic, even though individual highest positive anomalies are also
observed in this season (not shown here). Autumn precipitation series generally show
a random run of anomalies at different time periods at many stations, mostly with an
unchanged mean, along with a some degree of low-frequency fluctuation at some
stations. Autumn precipitation series also indicate an increase during the last 10 years
at many stations, except those over the MED and MEDT regions (not shown here).
As an expected result of the general decrease with an apparent low-frequency
fluctuation in winter precipitation, annual precipitation series of many stations also
indicate a low-frequency fluctuation with a decreasing mean over the study period
(not shown here). Annual precipitation is generally decreasing at many stations on the
Black Sea coast and over the MED region. Long-period fluctuations are evident
particularly in the stations over the MED, MEDT, CCAN and CEAN regions. Most
of the years from the early 1970s are generally characterized by a longer run of the
dry anomalies.
Secular trends. Numbers of the stations having a significant secular trend in
normalized annual and seasonal precipitation anomaly series are given in Table 1.
The time-series plots of sequential values of the statistics u(t) and u '(t) from the
Mann-Kendall rank correlation test are also shown in Fig. 11.1-2 for winter and
spring precipitation anomaly series ofthe selected 15 stations of Turkey. Results from
both the Mann-Kendall test statistics and visual interpretations of the time-series plots
of sequential values of the statistics u(t) and u '(t) for 91 stations are summarized as
follows:
In spring, a general upward trend with high year to year variations is dominant
in many stations except the stations over the BLS Region, where a general
downward trend appears. The upward trend was evident during the period from
the mid-1940s to the late 1960s at many stations and to the 1980s at some
stations (Fig. 11.2). This increased precipitation period has been generally
followed by a downward trend at many stations. Only 4 stations experience any
significant trend in spring precipitation series.
In summer, 7 stations, almost all of which take place in the CMED and CCAN
regions, indicate a significant upward trend.
Murat Ttirke~
Spring series generally indicate a high-frequency variation with an unchanged
mean at some stations and about slightly increasing mean at many stations (Fig. 10.2).
Stations of the BLS region generally experience increased precipitation from the early
1940s to mid-1960s. Thereafter there is a general decrease. Stations of the MED
region generally depict wet conditions in the late 1940s, early 1950s, 1970s and
1980s, along with the dry conditions in the 1940s and 1990s. Stations over the CMED
region show a general increasing trend, from the mid-1940s to the mid-1970s, with
the wet conditions in the late 1940s, early-mid 1950s, late 1960s and 1970s.
Thereafter drier conditions dominate. At the stations of the CCAN region, wet
conditions generally dominate over the early 1950s, mid-late 1960s and 1970s, along
with the dry conditions over the 1930s, early-mid 1940s, mid-late 1950s and early
1960s.
Summer rainfall series generally tend to increase at some stations and to show
unchanged situation at many stations. The longer runs of negative anomalies are a
dominant characteristic, even though individual highest positive anomalies are also
observed in this season (not shown here). Autumn precipitation series generally show
a random run of anomalies at different time periods at many stations, mostly with an
unchanged mean, along with a some degree of low-frequency fluctuation at some
stations. Autumn precipitation series also indicate an increase during the last 10 years
at many stations, except those over the MED and MEDT regions (not shown here).
As an expected result of the general decrease with an apparent low-frequency
fluctuation in winter precipitation, annual precipitation series of many stations also
indicate a low-frequency fluctuation with a decreasing mean over the study period
(not shown here). Annual precipitation is generally decreasing at many stations on the
Black Sea coast and over the MED region. Long-period fluctuations are evident
particularly in the stations over the MED, MEDT, CCAN and CEAN regions. Most
of the years from the early 1970s are generally characterized by a longer run of the
dry anomalies.
Secular trends. Numbers of the stations having a significant secular trend in
normalized annual and seasonal precipitation anomaly series are given in Table 1.
The time-series plots of sequential values of the statistics u(t) and u '(t) from the
Mann-Kendall rank correlation test are also shown in Fig. 11.1-2 for winter and
spring precipitation anomaly series ofthe selected 15 stations of Turkey. Results from
both the Mann-Kendall test statistics and visual interpretations of the time-series plots
of sequential values of the statistics u(t) and u '(t) for 91 stations are summarized as
follows:
In spring, a general upward trend with high year to year variations is dominant
in many stations except the stations over the BLS Region, where a general
downward trend appears. The upward trend was evident during the period from
the mid-1940s to the late 1960s at many stations and to the 1980s at some
stations (Fig. 11.2). This increased precipitation period has been generally
followed by a downward trend at many stations. Only 4 stations experience any
significant trend in spring precipitation series.
In summer, 7 stations, almost all of which take place in the CMED and CCAN
regions, indicate a significant upward trend.