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NORTH SEA - CASPIAN PATTERN (NCP) and its influence on the hydroclimate of Turkey. OZAN MERT GÖKTÜRK İ TÜ EURASIA INSTITUTE OF EARTH SC IENCES. Contents. A re view of NCP Data sets and methodology Results: effects of NCP Problems and discussion.
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NORTH SEA - CASPIAN PATTERN (NCP)and its influence on the hydroclimate of Turkey OZAN MERT GÖKTÜRK İTÜ EURASIA INSTITUTE OF EARTH SCIENCES
Contents • A review of NCP • Data sets and methodology • Results: effects of NCP • Problems and discussion
North Sea – Caspian Pattern (NCP) (Kutiel ve Benaroch, 2002) NCPI= gpm(500hPa) (0°, 55° N ; 10° E, 55° N) –gpm(500hPa) (50° E, 45° N ; 60° E, 45° N)
NCP(+) NCP(-)
Progress of NCPI through the year (Kutiel ve Benaroch, 2002)
Hypothesis There should be a significant relation between NCP and Turkey’s precipitation/streamflow regimes. This relation can be investigated by Pearson’s correlation coefficient and also with the Canonical Correlation Analysis.
Data sets • Predictors - Large-scale 500 hPa geopotential height field - NCPI • Predictands - Monthly precipitation series of Turkey - Monthly streamflow series of Turkey
Predictors • Monthly mean 500 hPa geopotential height field • 10°W - 60°E 30°N - 70°N 2.5°x2.5° grid 493 grid points • 1958 – 2003 • NCEP-NCAR Reanalysis
Predictands: streamflow • Monthly, 110 stations • 1958-2003
Predictands: precipitation • Monthly, 260 stations • 1958-2003
Data pre-processing • “De trending” : to include only the variations. • Outlier trimming: to avoid the distortion of the analysis by the extreme values
Data homogenization • Alexandersson (1986) • Based on comparison with a reference regional time series
Methodology • Pearson’s correlation (well-known) Correlate NCPI with monthly streamflows and precipitations…
Methodology • Canonical Correlation Analysis (CCA) Pearson korelasyonu -> univariate time series CCA -> multivariate time series
CCA Space Time Any correlation between these two??? 1. Write the time series as anomalies,
2. These anomalies are composed of independent spatial patterns and their time coefficients… (von Storch ve Zwiers, 1999) Time coefficients Spatial patterns
X X + X + + … =
CCA 3. Find such spatial patterns that correlation between their time coefficients are the greatest. That is , maximize
CCA 4. ... finally, Canonical predictor patterns Canonical predictand patterns
CCA 5. -Canonical Correlation Coefficient (CCC)
Variance represented ….% Corr.with NCPI = CCC = ….. Anomalies - predictors Anomalies - predictands Variance represented % ....
January – streamflow Pearson’s correlations with NCPI
February – streamflow Pearson’s correlations with NCPI
r.Var. %16 NCPI cor. 0.46 January Streamflow 1. CCA pair CCC = 0.92 r.Var. %37
January – precipitation Pearson’s correlations with NCPI
r.Var. %23 NCPI cor. 0.72 January Precip. 1. CCA pair CCC = 0.98 r.Var. %43
March – streamflow Pearson’s correlations with NCPI
March – precipitation Pearson’s correlations with NCPI
April – precipitation Pearson’s correlations with NCPI
May – streamflow Pearson’s correlations with NCPI
Streamflow... No significant relation for the rest of the year • Precipitation... No significant relation with NCP for May and June…
July – precipitation Pearson’s correlations with NCPI
August – precipitation Pearson’s correlations with NCPI
September – precipitation Pearson’s correlations with NCPI
October - precipitation Pearson’s correlations with NCPI
November- precipitation Pearson’s correlations with NCPI
r.Var. %26 NCPI ile 0.68 November Precip. 1. CCA pair CCC = 0.95 t.Var. %17
December – precipitation Pearson’s correlations with NCPI
r.Var. %17 Corr with NCPI 0.61 December Precip. 1. CCA pair CCC = 0.98 r.Var. %21
Winter (DJF) – precipitation Pearson’s correlations with NCPI
Winter (DJF) – streamflow Pearson’s correlations with NCPI
Spring (MAM) – streamflow NCPI ile Pearson korelasyonları
Summer (JJA) – precipitation Pearson’s correlations with NCPI
Fall (SON) – precipitation Pearson’s correlations with NCPI
Summary • NCP effective mostly in winter • NCP(+) enhances precip at Black Sea shoreline • NCP(-) enhances precip at western provinces • February, NCP(+), (subtropical jet) • Some peculiar locations (e.g. Artvin, Sinop) • NCP effective also in summer
Future studies? • NCP and NAO??? A combined index? • Is NCP predictable???