Redefining the climate zones of Turkey using cluster analysis

Daily precipitation totals for five consecutive summers (1994)(1995)(1996)(1997)(1998) were obtained for 136 stations in East Anglia to explore geographic variations in rainfall. S-mode principal components analysis (PCA) was used to identify the main spatial modes of variability in the region's precipitation field. The components were interpreted physically by examining synoptic charts and the British Isles' circulation variables for the days with high PC scores. Whilst seven principal components have eigenvalues greater than 1, and collectively explain 86.3% of the variance, only the first 5 PCs have well defined rainfall patterns that can be attributed to specific circulation patterns. The most dominant pattern (PC 1) shows a gradient between wetter conditions in NE Norfolk and drier conditions in Cambridgeshire and Essex, which is favoured by a cyclonic northerly airflow. PC 2 is almost as dominant, and shows a west to east decay in rainfall totals that is typically associated with active zonal W-SW flows. PC 3 sees the highest totals occurring in Essex. Wetter conditions in the south of East Anglia tend to occur when areas of low pressure follow a southerly track along the English Channel and southern North Sea. PC 4 shows a maximum in convective activity that occurs furthest inland in SE Cambridgeshire and west Suffolk, with the convection being triggered or accentuated by the East Anglian Heights (the highest land in East Anglia). PC 5 shows the rainfall distribution under a cyclonic N-NW, whereby showers generated over The Wash penetrate inland and produce the most rainfall in west Norfolk. Finally, a summer precipitation regionalization was derived by applying agglomerative hierarchical cluster analysis to the loadings of PCs 1-7. It is concluded that a location's precipitation climatology is more strongly determined by the orientation of the nearest coastline rather than simply the site's distance from the North Sea.

Section: Methodsmentioning

confidence: 99%

Summer daily precipitation variability over the East Anglian region of Great Britain

Neal

Phillips

2008

“…As defined in Unal et al (2003), the Black Sea region features a mean annual temperature of 13.7°C (SD 0.7°C) and a total mean precipitation of 1175.8 mm (SD 5.5 mm). The climate type changes from semi-humid to very humid over the study region (Figure 2).…”

Section: Hydroclimatology Of North-western Turkey and The Filyos Rivementioning

confidence: 99%

Tree‐ring reconstructions of precipitation and streamflow for north‐western Turkey

Akkemik

D’Arrigo

Cherubini

et al. 2007

ABSTRACT:We describe tree-ring reconstructions of spring (May-June) precipitation and spring-summer (May-August) streamflow for north-western Turkey, both beginning in AD 1650. These are among the first such reconstructions for the region, and the streamflow reconstruction is among the first of its kind for Turkey and the entire Middle East. The reconstructions, which both emphasize high-frequency variations, account for 34 and 53% of their respective instrumental variance. Comparison to precipitation and runoff data provides some means of verification for the instrumental streamflow record, which is very short (30 years). Drought and flood events in the reconstructions are compared to historical archives and other tree-ring reconstructions for Turkey. The results reveal common climatic extremes over much of the country. Many of these events have had profound impacts on the peoples of Turkey over the past several centuries.

“…The last event was the result of a prolonged period of suboptimal rainfall, combined with extremely high summer temperatures (e.g. van der Schrier et al, 2007). It influenced a full range of ecosystems throughout Central Europe affecting some of the basic ecosystem services, starting with fodder production (Schaumberger et al, 2006) and ending with carbon sequestration (Ciais et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Developing a regional drought climatology for the Czech Republic

Trnka

Dubrovský

Svoboda

et al. 2008

This study presents a methodology for the analysis of a drought climatology within a particular region that enables a user to define drought areas at a high spatial resolution. It is suitable for quantifying the relative differences in the intensity of drought spells, and the frequency and duration between individual stations within an area of interest. The methodology is based on the Standardized Precipitation Index (SPI), the Palmer Drought Severity Index (PDSI) and the Palmer Z-index (Z-index). However, the climatological parameters needed to process and calculate the indices were not derived separately for each site as is usually done, but were based on a set of all available weather stations in the studied region. This approach was utilized in the case study including all of the Czech Republic using 233 climatological stations with monthly records of mean temperature and precipitation for the period 1961-2000. The study is also focussed on the development of more efficient ways of communicating results to the stakeholders. Therefore, a method allowing for an integration of several drought indices into a single indicator called the Integrated Climatological Drought Indicator (ICDI) was developed. The newly developed method allowed for an objective identification of the drought-prone regions of the country that were defined as areas with a chance (higher than 50 and 60% respectively) of moderate or extreme drought. We have found that 12.3 and 3% of the country area, respectively, belong within these categories and that these regions also happen to be prime agricultural areas. The conclusions were supported by the results of a cluster analysis. Finally, the analysis of time trends was conducted, which showed that the majority of 233 stations had grown significantly drier during the studied period. The main driving force behind this development was found to be an increase of temperature, especially in the 1990s.