136
1. Luterbacher and E. Xop1aki
(NAOI) reconstructions (Cook et al. 2001) in order to see whether there is any
connection between Mediterranean climate and the atmospheric circulation over the
eastern North Atlantic over the last 5 centuries. The discussions and conclusions are
presented in the last sections.
2 Data and Methods
2.1
Predictor Data (Instrumental and Documentary Proxy Data for the
Last 500 Years)
The available time series of documentary proxy and early instrumental data and the
domain of the reconstructed area are presented in Figure la (Luterbacher et al.
200Ia). Circles mark time-varying instrumental data series (pressure, temperature
and precipitation) provided by different sources, triangles mark data series estimated
from high resolution documentary evidence (see above), thus not directly measured
values. Prior to AD 1659 only reconstructed climatic indices mostly on a seasonal
resolution are available which are given in red triangles (Figure 1 a). These seasonal
predictors are continuously available or for parts ofthe AD 1500 to 1658 period. For
the Mediterranean, relevant time series are the documentary proxy based
reconstructed seasonal precipitation of Andalusia (Southern Spain, Rodrigo et al.
2001), the tree-ring based reconstructions of precipitation over Central Turkey
(D' Arrigo and Cullen 2001) and Southern Jordan (Touch an et al. 1999).
Thus, from AD 1500 to 1658, seasonal temperature and precipitation fields were
reconstructed. From AD 1659 the reconstructions are monthly based (Luterbacher
et al. 200le). The same data have recently been used to successively reconstruct
monthly (seasonally) atmospheric circulation indices (NAOI) and entire SLP fields
back to AD 1659 (AD 1500-1658) (Luterbacher et al. 200lab).
The dependent variables (predictands) consist of gridded monthly temperature
and precipitation (OSxOS resolution) data on the land areas from 30
c
N-70'N and
30'W-40oE. The gridded monthly temperature and precipitation data for the period
1901-1990 were taken from New et al. (2000).
2.2
Statistical Reconstruction of Large-scale 500 Years Temperature
and Precipitation Fields
To reconstruct the gridded temperature and precipitation fields we follow the
description of Luterbacher et al. (200le). We first identified all predictors for which
data were available for that particular month (season) and all other months from the
same climatological season (i.e. winter is December, January and February). Since
the data base varies over the whole 500 years (Fig. 1 b), this resulted in a total of 320
different cases for the monthly and seasonal temperature and precipitation
1. Luterbacher and E. Xop1aki
(NAOI) reconstructions (Cook et al. 2001) in order to see whether there is any
connection between Mediterranean climate and the atmospheric circulation over the
eastern North Atlantic over the last 5 centuries. The discussions and conclusions are
presented in the last sections.
2 Data and Methods
2.1
Predictor Data (Instrumental and Documentary Proxy Data for the
Last 500 Years)
The available time series of documentary proxy and early instrumental data and the
domain of the reconstructed area are presented in Figure la (Luterbacher et al.
200Ia). Circles mark time-varying instrumental data series (pressure, temperature
and precipitation) provided by different sources, triangles mark data series estimated
from high resolution documentary evidence (see above), thus not directly measured
values. Prior to AD 1659 only reconstructed climatic indices mostly on a seasonal
resolution are available which are given in red triangles (Figure 1 a). These seasonal
predictors are continuously available or for parts ofthe AD 1500 to 1658 period. For
the Mediterranean, relevant time series are the documentary proxy based
reconstructed seasonal precipitation of Andalusia (Southern Spain, Rodrigo et al.
2001), the tree-ring based reconstructions of precipitation over Central Turkey
(D' Arrigo and Cullen 2001) and Southern Jordan (Touch an et al. 1999).
Thus, from AD 1500 to 1658, seasonal temperature and precipitation fields were
reconstructed. From AD 1659 the reconstructions are monthly based (Luterbacher
et al. 200le). The same data have recently been used to successively reconstruct
monthly (seasonally) atmospheric circulation indices (NAOI) and entire SLP fields
back to AD 1659 (AD 1500-1658) (Luterbacher et al. 200lab).
The dependent variables (predictands) consist of gridded monthly temperature
and precipitation (OSxOS resolution) data on the land areas from 30
c
N-70'N and
30'W-40oE. The gridded monthly temperature and precipitation data for the period
1901-1990 were taken from New et al. (2000).
2.2
Statistical Reconstruction of Large-scale 500 Years Temperature
and Precipitation Fields
To reconstruct the gridded temperature and precipitation fields we follow the
description of Luterbacher et al. (200le). We first identified all predictors for which
data were available for that particular month (season) and all other months from the
same climatological season (i.e. winter is December, January and February). Since
the data base varies over the whole 500 years (Fig. 1 b), this resulted in a total of 320
different cases for the monthly and seasonal temperature and precipitation