CLIMATE RELATIONSHIP OF CENTRAL EUROPE

            Understanding climate zones of central Europe is an important step in better interpreting the tree ring data.  The locations of the individual trees that comprise the tree ring chronologies are far less significant if they are not in the same climate belts.  There are distinct climate divisions in Europe as evident from the meteorological data.  So, European chronologies do not all relate or crossdate with each other.  There is, however, a decent GLK value for the European oak chronologies in the United Kingdom and the temperate regions of north central Europe (Schweingruber, 1988, 131, Baillie, 1982).  There is an annual precipitation and temperature gradient by latitude in central Europe (Schuepp and Schirmer, 1977, Pfister and Lauterburg, 1992) .  The predominant wind direction, Gulf Stream effect, various mountain ranges, and Mediterranean Sea all contribute to the variability in European climate.

            At larger scales of geographic generalization, such as biological growing patterns, it is necessary to use zonal belts (Chernavskaya, 1992) .  The environmental differentiation of central Europe becomes more apparent looking at the dominant vegetation types (Figure 4.2).  This places the majority of Germania in the same climate zone with a few exceptions in the Netherlands, the far eastern portions, and high mountain areas.  However, there is more to establishing a climate relation than dominant vegetation cover, even though it is a good place to start.

Over the past few hundred years, meteorological records have become more abundant and widespread.  Some of the earliest European weather stations are in central Europe at Basel, Berlin, Geneva, Höhenpeissenberg, Vienna, and the Great Saint Bernard Pass (Figure 4.3).  These older sites have recorded various meteorological phenomena from the early 18^th century.  A correlation study on monthly and annual meteorological variation from the stations based in Berlin (records tested 1719 to 1927), Prague (records tested 1775 to 1934), and Karlsruh (records tested 1779 to 1920) have been shown to be very close (Schuepp and Schirmer, 1977) (Figure 4.4).  These sites did show the predicted variation by latitude, but they correlated to each other and weather phenomena at one site was reflected in the others. 

There is a correlation in the modern monthly mean precipitation records from the weather stations located in Berlin, Essen, Fichtelberg, Geisenheim, Goerlitz, Hamburg, Hannover, Karlsruhe, Kassel, Konstanz, Lindenberg, Muenchen, Nuernberg, Potsdam, Tostock, Schleswig, and Trier (Figure 4.5). These meteorological stations’ records were compiled and averaged by their monthly mean precipitation from 1961 to 1991.  The monthly averages shows that this entire region receives most precipitation in June and July and least in October and February.  More importantly, these data show that all of the weather stations record rainfall through out the year (Figure 4.6). 

Looking at the annual precipitation records of weather stations in Berlin, Copenhagen, Frankfurt, Geneva, Prague, Trier, and Vienna from 1850 to 1969 (Figure 4.7), there is a latitudinal gradient over Central Europe, but there is still a relationship between the stations (Figure 4.8).  For example, the data reveal that annual precipitation is greater in Geneva than in Prague.  Modern precipitation records for central Europe show there is general consistency in both maximum and minimum precipitation across Europe that could have been proportionately similar in 3^rd century Germania (Figures 4.9 and 4.10).  Figures 4.9 and 4.10 reveal that southern and western Germania would receive more precipitation than eastern Germania, especially near the mountainous regions of the Alps and Caspian ranges.

Western and southern Germania would be an ideal location of tree ring studies that would be representative of the majority of central Europe.  Central Europe is divided into east and west zones in the spring that divide the region about the Vistula River, but the remainder of the year is fairly contiguous (Pfister and Lauterburg, 1992) .  Therefore, if the tree ring record suggests that the trees of western and southern Germania were showing poor growth rates, or smaller rings, then the rest of Germania would be affected as well.  There is a good correlation between the tree ring chronologies of central Europe, except for some of the high alpine chronologies that reflecting orographic effects.  Using the GLK coefficient, there is a high correlation making the tree ring records crossdatable between the German and the Netherlands chronologies (Brongers, 1973) (Figure 4.11).  The average correlation using GLK of the Netherlands and German is 63.5% with an average of 300 years overlap in the study.  This degree of correlation indicates accurate crossdating and, in turn, shows similar interpretations of climate variability over the same period (Table 4.1).

            This is not the case with the Mediterranean chronologies.  The Mediterranean tree-ring chronologies have proven to be difficult for purposes of isolating precipitation and temperature, because they are in a climate zone with different characteristics than central Europe (Serre-Bachet, 1989) .  The Mediterranean region does not show as strong seasonal variability as central Europe and this is reflected in their chronologies.  The ancient region of Germania had a different climate regime than those south of the Alps and should have to be studied separately (Serre-Bachet, 1989) . 

            The four chronologies, river Main, river Danube, Becker Roman Archeological, and the corrected Hollstein, are in ideal locations to reconstruct the climate variability in the river valleys of Germania (Figure 4.12).  Since all four of these chronologies crossdate very well, they were combined into a master chronology for the whole region.  The modern records support the correlation between the region north of the Alps, which is the ancient region of Germania.  These climate consistencies allow the master tree-ring record to be applied in the study of climate change in Germania.

Table 4.1 – Chart showing the gleicklaufigkeit (GLK) comparison between the Netherlands chronologies and the German master chronology showing the high level of correlation in central Europe (Brongers, 1973) .