INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. (2013) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.3869

A 250-year annual precipitation reconstruction and drought assessment for from Pinus brutia Ten. tree-rings Carol Griggs,a* Charlotte Pearson,b Sturt W. Manninga and Brita Lorentzena a The Malcolm and Carolyn Wiener Laboratory for Aegean and Near Eastern Dendrochronology, Cornell University, Ithaca, NY, USA b LTRR, University of Arizona, Tucson, AZ, USA

ABSTRACT: Precipitation around Cyprus, a relatively small island, is generally consistent in year-to-year variation in all dimensions except amplitude, with the higher elevations in the west generally receiving more precipitation. An annual record of precipitation was found in tree-rings of the predominant pine species, Pinus brutia Ten., which grows from the lower foothills up to 1400 m in altitude across the island. Tree-ring chronologies from four sites in west-central Cyprus are used here to reconstruct the annual September to August precipitation and a drought record for AD 1830–2006, with the drought reconstruction extending back to 1756. A minimum of 40% of the variance in annual precipitation and drought occurrence is explained by the variance in the tree-ring widths in all cases. Our drought assessment indicates that, on average, annual droughts occur once every 5 years and sustained droughts, 2–6 years in length, have occurred in small clusters of time, from 1806–1824, 1915–1934 and 1986–2000, when the winter North Atlantic Oscillation was in a predominantly positive phase. These results suggest that a sustained drought period has a mean return time probability of one in 70–100 years. This study provides the first long-term annual precipitation reconstruction and drought assessment at low to mid-elevations for Cyprus and will aid in future plans for drought mitigation.

KEY WORDS annual precipitation reconstruction; drought record; dendroclimatology; Pinus brutia (Ten.); Cyprus; Troodos Massif; North Atlantic Oscillation Received 25 February 2013; Revised 8 October 2013; Accepted 12 October 2013

1. Introduction elevation 1951 m) in the southwest and the Pentadaktylos (Kyrenia) range (maximum height 1000 m) along the Past climate parameters have been reconstructed from northern coast, which give Cyprus high topographical many proxy records developed to understand palaeocli- variability (Price et al., 1999). mate conditions over time around the world. The nature Cyprus has a Mediterranean climate regime consisting and quality of the reconstruction depend on the origin of hot, dry summers with clear skies from June to of the data sets employed. For the time series in a den- September, and cool, wet winters from November to droclimatological reconstruction the general principle is March (Figure 2). The short autumn and spring seasons that trees primarily respond to certain climate parameters in October, April and May are characterized by high during their growing season months, particularly precip- variability and rapid changes in precipitation and temper- itation in any drier region of the range of the studied ature (Price et al., 1999). The minimal cloud cover and species, and temperature at high latitudes or altitudes high temperatures in summertime are largely influenced (Hughes et al., 2011; Fritts, 1976). However, in Cyprus, by the combination of subsidence from the northward the amount of precipitation occurring year round criti- shift of the subtropical high and the Persian trough, a cally influences water availability throughout the growing shallow low-pressure trough extending from the Asian season, so the trees contain an annual precipitation record monsoon depression centred over Pakistan, which leads that is unusual and of considerable importance in acquir- to summertime northwesterly winds. When summer ing a more complete understanding of long-term climate rainfall does occur, it is usually in the form of isolated change in Cyprus and the northeastern Mediterranean thunderstorms and contributes less than 5% of the total region. ◦ ◦ annual rainfall. Winter weather is generally influenced Cyprus is located at approximately 35 N and 33 E, at by unsettled small low pressure systems crossing the the east end of the Mediterranean Sea, and is ∼224 km sea from between the continental anticyclone of Eurasia WSW to ENE, and ∼97 km NNW–SSE with a land area and the persistent low pressure belt over North Africa. of approximately 9250 km2 (Figure 1). The island has These depressions produce the majority of the island’s two mountain ranges – the Troodos Massif (maximum annual precipitation, with the average precipitation from December to February being about 60% of the annual total (Price et al., 1999) (Figure 2). * Correspondence to: C. Griggs, The Malcolm and Carolyn Wiener Unequal heating of the sea surface and island interior Laboratory for Aegean and Near Eastern Dendrochronology, B48 Gold- win Smith Hall, Ithaca, NY 14853, USA. E-mail: [email protected] plus a large variation in the island’s topography create

 2013 Royal Meteorological Society C. GRIGGS et al.

◦ Figure 1. Map of Cyprus showing study sites and weather stations on the Island. The cross-hair shows the centre of the 4 CRU 0.5 grids at ◦ ◦ 33.0 E, 35.0 N.

Figure 2. Mean monthly precipitation totals and average temperature for Cyprus. Data is from the Cyprus Meteorological Service and the Climate Research Unit (CRU). substantial seasonal and daily temperature differences depths (ca. 1–1.5 m) on the high northern slopes, while between these sites, resulting in localized climate varia- snowfall is rare in the Kyrenia range and lowland areas tion. The central Troodos Massif, and, to a lesser degree, (Pashiardis, 2000). However, despite variations in ampli- the Kyrenia range also play an important role in defining tude, precipitation across the island is fairly consistent in the weather conditions of Cyprus. Mean annual precip- year-to-year anomalies (Figure 2, Table 1) which allows itation increases up the south windward slopes to the for a stable precipitation reconstruction across the island. top of the Troodos range from 45 cm to nearly 110 cm, Over the last half of the 20th century AD, available while on the leeward slopes amounts decrease steadily meteorological data indicate a general increase in tem- to the north and east to around 30–35 cm (Price et al., perature and a slight decrease in precipitation with a 1999; Pashiardis and Michaelides, 2008). In the winter corresponding increase in drought (Price et al., 1999; months snow may lie for several weeks at considerable Pashiardis and Michaelides, 2008). We show here that

 2013 Royal Meteorological Society Int. J. Climatol. (2013) A 250-YEAR PRECIPITATION AND DROUGHT RECORD FROM TREE-RINGS FOR CYPRUS

Table 1. October-September P correlations between stations for over 500 years (Tsintides et al., 2002). Touchan et al. and the average of 4 grids (CRU) for 1918–2008, with the (2005) report finding P. brutia at elevations ranging from exception of Agios Epifanios, at 1957–2008. 1483 to 1646 m at Armiantos, Cyprus, with lifespans of over 400 years. Our collection indicates a range of Agios Epifanios 150–300 years is more normal for the species at the mid Troodos 0.693 Troodos and lower elevations, and Boydak (2004) reports a simi- 0.697 0.866 Pedoulas lar age range (250–305 years) for P. brutia mainly at the Pano Panagia 0.569 0.841 0.843 Pano Panagia 0.779 0.570 0.592 0.561 Peristerona middle elevation range in southwestern Turkey. In both Avg 4 grids 0.793 0.649 0.754 0.670 0.697 areas human activity is a major factor, but climate condi- (CRU) tions are also more stressful to tree growth than at higher elevations. Immediately apparent in our exploratory analysis was the number of droughts and the extreme level of annual the clear response of P. brutia ring-growth to annual precipitation during the droughts have not significantly precipitation. This response is similar to a study by changed, but the variability and number of moderate to Sarris et al. (2007) that showed evidence of significantly very wet years is considerably reduced, especially in the lower annual precipitation from 1985 to 2000 recorded in 1970s–1980s. This exacerbates the effect of droughts P. brutia on the island of Samos, Greece. The drought when they occur due to little or no groundwater replen- years of the Samos meteorological data correlate very ishment from current and previous years. In the late 20th well with the Cypriot drought years, taking into account to early 21st centuries, drought in Cyprus has caused their use of January to December precipitation rather than problems ranging from support of a growing population our use of the precipitation from September to December and tourist industry to sustaining the agricultural sector of the year before growth and January to August of (especially viniculture). The severe drought of 2007/2008 the year of growth. Touchan et al. (2005) reconstructed reduced reservoir supplies to just 3% of capacity (Dav- May to August precipitation on a much larger scale in enport, 2008). Mitigation and management strategies are the northeastern Mediterranean region, including Cyprus, needed, but such planning is inhibited by the fact that using many genera and species of conifers, including most of the ∼150 weather station records on the island P. brutia. However, it is not an annual record, and the begin around 1960 or later, with less than 25 extending drought years indicated by both the meteorological data back to the early 1900s and even fewer having the unifor- and their reconstruction do not match many of the annual mity necessary for a valid assessment. Our reconstruction Cypriot drought years in our data sets. The results of extends the meteorological record by 160 years, nearly Kienast et al. (1987) indicate variability in the climate tripling the information necessary for planning drought response of trees growing along altitudinal transects, with mitigation strategies. This data set also provides a more precipitation the primary factor but increased sensitivity complete record of variation in precipitation over time to temperature at the higher altitudes, especially in areas and space, in particular with respect to its relationship to with thin soil. Thus our observations and the previous the low-frequency climate variation that is most evident studies clearly indicate that P. brutia is a suitable species in seasonal data (Michaelides et al., 2009). for reconstructing Cypriot drought history. Pinus brutia Ten. (Calabrian pine) is a common low- We selected four study sites at varying elevations land pine species in the eastern Mediterranean (Panetsos, that were likely sensitive to rainfall variation (Figure 1, 1981; Quezel´ and Barbero, 1992) whose range stretches Table 2). The sites are located at ascending altitudes from northeastern Greece, the Aegean Islands and Cyprus around the Troodos Massif, underlain by the Troodos through the west and southern coasts of Turkey to Syria, ophilite and a mixture of non-calcareous eutriclithosols Lebanon and Iraq (Panetsos, 1981; Boydak, 2004). The and cambiosols. They are the Mitsero Hills area (MSH), species is thermophilous and prefers lowland semi-humid the Roudhias Valley, Arodafna (RVA), Stavros tis Psokas to humid sites with mean annual temperatures between ◦ (STV) and Doxa Soi o Theos (DST) (Figure 1, Table 2). 12–20 C(Quezel´ and Barbero, 1992; Boydak, 2004). In The site at the lowest altitude, MSH, is northeast of the Cyprus, P. brutia is the dominant tree species at eleva- Troodos Massif on the edge of the Mesoria Plain in tions from 0 to 1400 m in the Troodos and Pentadaktylos central Cyprus, within the pillow lava zone around the ranges (Ciesla, 2004), making up over ca. 90% of the mountains, and is distinct from the other sites in that it forested area of Cyprus during the last century (Thirgood, is within the drier rain-shadow between the Troodos and 1981; Pantelas, 1986). Although its provenances vary Pentadaktylos (Kyrenia) ranges. physiologically (Schiller, 2000; Boydak, 2004), P. brutia is generally extremely drought resistant, with a deep root- ing zone, and can grow in areas with mean annual rainfall 2. Methods as low as 400 mm (Nahal, 1983). It typically grows on marls, limestone and dolomites and can tolerate volcanic At each site, up to three cores were sampled from each soils, but does not tolerate poorly drained soils (Quezel,´ tree at breast height (ca. 1.3 m) using a 5 mm increment 2000). In optimum conditions and especially at the higher borer. Sections were also cut from available stumps at elevations with more precipitation, these trees can live the Roudhias Valley site. The cores and two to four radii

 2013 Royal Meteorological Society Int. J. Climatol. (2013) C. GRIGGS et al.

Table 2. Description of site locations and sample collection.

◦ ◦ Site Site code Elevation Latitude N Longitude E Years Total No. of No. of range (m) spanned years trees cores /radii Mitsero Hills MSH 485–498 35.034 33.094 1776–2009 234 20 42 Roudhias Valley, Arodafna RVA 494–860 34.955 32.649 1633–2011 379 23 40 Stavros tis Psokas STV 860–1132 35.037 32.639 1656–2006 351 24 53 Doxa Soi o Theos DST 1328–1403 34.955 32.965 1637–2008 372 25 41 of the sections were prepared and measured according homogeneity (Michaelides et al., 2009: Table 1) were to standard dendrochronological procedures, using the considered in choosing the data sets along the altitudinal TRiDaS compliant dendrochronological analysis pack- and longitudinal transects. Their monthly precipitation age – Tellervo (Brewer et al., 2010; Jansma et al., 2010). anomalies (δP) were averaged into a single regional data The ring-width series for each tree were combined. For set. The values of the CRU precipitation and temperature ◦ each site, the tree-ring sequences were crossdated with anomalies from the four 0.5 grids covering 32.5–33.5 ◦ ◦ each other, and a site chronology was built. Crossdat- E, 34.5–35.5 N (Figure 1) were also averaged together ing and data quality were checked using the programme for inspection over the study region. Since our focus cofecha 6.02 (Holmes, 1983). was on reconstructing precipitation variations and The time series for each site was constructed using drought, we used the temperature data mainly to test arstan 41d_xp (Cook and Holmes, 1986). The tree-ring whether it had any significant influence on the drought, width measurements were detrended by fitting a negative precipitation and ring growth over time and space. exponential curve when possible or, more often, a spline The Mitsero Hills chronology was used for a local curve with a 50% cutoff. Each year’s ring width was precipitation reconstruction due to the site’s location divided by the curve’s value in the same year to remove in a low altitude, xeric environment. For the regional long-term non-climatic effects from age, tree size and climate reconstruction, principal components (PC) were stand dynamics (Fritts, 1976). The autocorrelation of the calculated from the four site chronologies. The extended adjacent ring widths in each site’s standardized chronol- drought reconstruction back to 1755 used the two ogy was removed to make the residual chronologies middle-elevation site chronologies. Initially, primary used here for the reconstructions (Cook and Kairiukstis, growth responses of all the tree-ring data sets to climate 1990). We re-iterated arstan for each site chronology, parameters were assessed from Pearson correlations choosing the option to test for unstable changes in the of the monthly climate data of the stations and region variance of the ‘common signal’ in the represented versus the site chronologies and PCs. To find the transfer samples across the chronology. In this test, for each functions suitable for reconstruction, stepwise multiple period in the chronology over which there is no change regressions were used in which each chronology or in sample count, the average correlation (r-bar) is PC was the predictand and the monthly climate data calculated between all samples included in that period were the predictors in order to determine the climate over the full length of time represented by those samples parameters recorded in the tree ring growth. Additional (e.g. for the12 samples in one 10-year period, the r-bar is response functions used combinations of the monthly calculated not for those 10 years, but for the total number data sets, ranging from seasonal to annual in length, as of years in common in these samples). Any significant predictors. The results were screened to determine the change in the r-bar values from one period to the next best predictor(s). The resulting equations were examined represents a change in the strength of the common for variations in the tree-ring growth response to climate signal in the chronology which reduces its homogeneity, parameters across the different elevations, from site to and requires an adjustment for a valid reconstruction site, and over time, to assess the spatio-temporal stability (Briffa and Jones, 1990; Osborn et al., 1997). In our of the response and potential reconstruction. four site’s residual chronologies, we found no significant Transfer functions were developed, in which the appro- differences in the r-bars over the intended reconstruction priate tree-ring chronologies or PCs were the climate periods and used them in the reconstructions. variables identified from the regression analyses. A Monthly precipitation data for 19 stations were split-sample procedure, in which the models were divided obtained in 2012 from the Cyprus Meteorological Ser- into subsets of equal length, was also used to verify vice, Ministry of Agriculture, , Cyprus. The data the climate reconstruction model’s stability. For verifica- sets, as well as gridded precipitation and temperature tion of the single-site reconstruction, the data sets were data sets in CRU TS 3.0 (Hulme, 1992, Mitchell and divided into two periods, 1959–1983 and 1984–2009. Jones 2005; Climatic Research Unit, 2010 at http:// For the regional precipitation and drought reconstruc- badc.nerc.ac.uk/browse/badc/cru) were used to calculate tion, the data was divided into three time periods from anomalies for each month and for many annual and 1918–1947, 1948–1977 and 1978–2006. The valid- seasonal combinations. The length of the precipitation ity of the resulting regression equations as accurate data sets, the locations of the stations and each data set’s transfer models was then evaluated with regression and

 2013 Royal Meteorological Society Int. J. Climatol. (2013) A 250-YEAR PRECIPITATION AND DROUGHT RECORD FROM TREE-RINGS FOR CYPRUS

Table 3. Descriptive statistics for the samples and chronologies. The mean correlation among trees and the variance explained by the first PCs are for 1830–2006.

Site code Standard Skewness Kurtosis First year EPS Mean correlation First PC deviation >0.85a and n > 4 among trees variance (%) MSH 0.32 −0.51 0.08 1820 0.762 66.9 RVA 0.21 −0.21 0.37 1740 0.606 73.0 STV 0.23 0.05 −0.05 1756 0.622 43.5 DST 0.20 −0.48 0.29 1816 0.628 42.0 aAn EPS value of >0.85 is arbitrarily significant (Cook and Kairiukstis 1990). correlation statistics, including variance explained (R2) the Troodos Massif (Table 4). Outside of Cyprus, the and reduction of error (RE; Cook and Kairiukstis, 1990). Mitsero Hills chronology correlates significantly with the The PRESS statistic (Allen, 1974) was also used in val- P. brutia chronology of Atera in Syria at about the same idation, and was performed by leaving 5 years out itera- altitude, and the three site chronologies from the higher tively across the lengths of the calibration and verification Cypriot sites correlate significantly with that from Goller¨ periods (Table 5). A regression equation was calculated in southern Turkey (Table 4). for each data set with the 5 years removed, then used to A careful inspection of the homogeneity of monthly calculate the predicted values for those 5 years. The 5- precipitation data from 13 weather stations established by year predicted data sets were combined into a time series Michaelides et al., (2009): Table 1) and the CRU gridded which was then compared to the original reconstruction. data, plus the stations’ geographic locations, resulted in The value of the residual sum of squares between the two two outcomes for the data sets used in this study. First, time series, divided by the length of the time series, is the precipitation data from Agios Epifanios, a station the PRESS statistic, and the smaller the value, the more close to the Mitsero Hills, was truncated up to 1957 due to accurate is the model (Allen, 1974). non-homogeneity, and converted into anomalies. Second, The final regression equations, successfully calibrated we combined the monthly precipitation anomalies from and verified, were used to reconstruct the local and three meteorological stations along a roughly east–west regional precipitation for 1831–2006, and the drought transect across the Troodos Massif – Pano Panagia record for 1756–2006. and Pedoulas from higher altitudes, and the Peristerona Finally, an assessment of the severity and frequency of station also near the Mitsero Hills site (Figure 1) – for the droughts over time indicated by the reconstructions was regional precipitation data. All three data sets correlate undertaken. We compared the reconstructions with sea- significantly with each other (Table 1), begin in 1917, sonal subsets of the precipitation data (September through and are homogeneous for 1917–2009. The comparison of November, December to February, March to May and this precipitation data and those from all Cypriot stations June through August) plus data sets of the North Atlantic and the CRU gridded data indicated that the CRU data is Oscillation (NAO; Hurrell, 1995, updated and available based mainly on precipitation data from several stations at www.cgad.ucar.edu/cas/jhurrell/nao.stat.winter.html), at lower elevations around the island. and the East Atlantic Western Russia pattern (EAWR; Krichak and Alpert, 2005a, updated and available at 3.2. The annual precipitation record ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/eawr_in Correlations and response functions between the site dex.tim). An arbitrary 11-year running mean of each chronologies and the monthly precipitation data sets indi- data set was used to emphasize low frequency variation. cated a consistent annual precipitation record. Especially From this assessment we are able to cautiously predict evident was a high variability in the growth response to future drought occurrence in Cyprus. any one particular month, season or multi-season precipi- tation over time. The correlations and response functions between the site chronologies and monthly precipita- 3. Results tion data also indicated an altitudinal gradient in growth response (Figure 3). The high positive correlations with 3.1. The tree-ring chronologies and meteorological the winter precipitation are with the chronology from the data low elevation Mitsero Hills site. At the higher sites the Table 3 provides a summary of the statistics for the strongest correlations were between tree rings and pre- residual tree-ring chronologies from each of the four cipitation during the growing season and in the previous sites – the Mitsero Hills area (MSH), 1776–2009; autumn months when the amount of water available for Roudhias Valley, Arodafna (RVA), 1633–2011; Stavros the next year’s growth starts to be replenished and is tis Psokas (STV), 1656–2006 and Doxia Soi o Theos stored in the trees whenever photosynthesis is possible (DST) for 1637–2008. The residual chronologies all for P. brutia (Yaseef et al., 2010). correlate significantly with each other, with the values These results also indicated that only the P. brutia tree- showing an expected reduction in relation to the sites’ rings from the lowest elevation site, Mitsero Hills (MSH), altitudes and locations relative to each other and to contain a clear record of annual precipitation (Pearson

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Table 4. Correlations between the four site tree-ring chronologies in this study, and between them and chronologies from other sites in Cyprus, Syria, and Turkey. Distances between sites are listed below the correlations. The bold values are at the p < 0.005 significance level, the normal print at p < 0.05, and the italicized values are insignificant. The Stavros Psokas, Armiantos, NW Syria, and Goller¨ (southern Turkey) chronologies were built by R Touchan, and the Stavros (mittel) and Planos Platres chronologies by F Schweingruber. All are available at the ITRDB (2010).

MSH Elev = 492m RVA 0.38 RVA Elev = 680m 43 km

STV 0.167 0.472 STV Elev = 1000m 43 km 9 km

DST 0.194 0.297 0.523 DST Elev = 1365m 15 km 29 km 31 km

Stavros (mittel) 0.279 0.581 0.593 0.492 Stavros (mittel) Elev = 800m 43 km 5 km 4 km 32 km

Stavros Psokas 0.157 0.236 0.609 0.441 0.333 Stavros Psokas Elev = 1050m 42 km 7 km 2 km 31 km 2 km

Armiantos −0.169 0.01 0.472 0.473 0.064 0.471 Armiantos Elev = 1550m 22 km 23 km 27 km 7 km 27 km 27 km

Plano Platres −0.026 0.092 0.321 0.479 0.154 0.43 0.576 Plano Platres Elev = 1620m 23 km 24 km 28 km 9 km 28 km 28 km 2 km

NW Syria 0.18 0.3 0.312 0.202 0.417 0.331 0.184 0.23 NW Syria Elev = 480m 278 km 319 km 317 km 292 km 320 km 318 km 298 km 299 km

Goller¨ 0.073 0.261 0.355 0.392 0.316 0.431 0.343 0.307 0.103 Elev = 1047m 324 km 304 km 296 km 323 km 298 km 297 km 322 km 323 km 512 km

Figure 3. Results of the response functions using the site chronologies and regional monthly precipitation data for the year before and the year of growth. Grey horizontal lines represent a p < 0.05, and the dotted line has a p < 0.01. The vertical broken lines surround the months of September through August, the sequence of months included in the annual reconstruction. r = 0.784). This is a predictable response because average 3.3. The reconstruction of precipitation and drought −1 local precipitation is around 400 mm year , a critical The data from the Agios Epifanios station, located about level for the species (Nahal, 1983), and the reason why 5 km SSE of the Mitsero Hills site at approximately this chronology was chosen for the local precipitation 200 m higher altitude, was chosen for reconstructing reconstruction. local annual precipitation due to its highest correlation

 2013 Royal Meteorological Society Int. J. Climatol. (2013) A 250-YEAR PRECIPITATION AND DROUGHT RECORD FROM TREE-RINGS FOR CYPRUS

Table 5. The statistics for the verification-calibration of each construction are listed below.

Local precipitation reconstruction Periods of calibration – verification 1958–2009 1958–1983 1984–2009 Period N Adjusted R2 PRESS RE R2 RE R2 RE R2 RE 1958–1983 26 0.654 0.45 0.672 0.615 0.590 0.564 0.600 1984–2009 26 0.545 0.49 0.619 0.615 0.613 0.668 0.666 1958–2009 52 0.608 0.41 0.613 0.668 0.677 0.564 0.617 Regional precipitation reconstructions 1918–2006 1918–1947 1948–1977 1978–2006 Period N Adjusted R2 PRESS RE R2 RE R2 RE R2 RE R2 RE 1918–1947 30 0.485 0.53 0.520 0.454 0.417 0.534 0.528 0.339 −0.014b 1948–1977 30 0.510 0.54 0.540 0.458 0.448 0.501 0.490 0.356 0.140 1978–2006 29 0.308 0.51 0.357 0.453 0.372 0.483 0.258 0.542 0.423 1918–2006 89 0.447 0.56 0.459 0.474 0.511 0.543 0.534 0.352 0.228 Drought reconstruction of negative δP anomaliesa 1918–2006 1918–1962 1963–2006 Period N Adjusted R2 PRESS RE R2 RE R2 RE R2 RE 1918–1962 16 0.542 0.15 0.603 0.586 0.518 0.669 0.470 1963–2006 23 0.681 0.14 0.710 0.556 0.422 0.563 −0.110b 1918–2006 39 0.563 0.16 0.586 0.586 0.586 0.602 0.514 0.678 0.624

Explanation of terms: PRESS is a predicted sum of squares statistic that assesses the model’s predictive ability; low numbers are more significant (see text). RE is reduction of error related to the reconstruction and met data’s residuals, and is statistically valid above 0. aOnly the negative anomalies are tested here; the RE of the complete data set’s reconstruction and verification is close to 0. bThe negative REs are the result of 1–5 years of substantial differences between precipitation anomalies and their reconstruction, but these differences are mainly in years when the anomalies are in the 1 to −1 value range. and response functions with the MSH chronology. The data set from the Peristerona, station, located 10 km NNW of Mitsero, at about 200 m lower altitude, was used for additional verification of the local reconstruction back to 1918. The combined monthly precipitation anomalies (1918–2009) from the stations used in the regional construction correlate significantly with at least one of the four site chronologies for September of the year before growth through August of the year of growth (Figure 3). The few significant correlations in the months before and after along with the results of the response function results indicated that the tree rings record Figure 4. The local precipitation calibration and verification data sets. annual rather than sub-annual precipitation fluctuations. The local precipitation is the September through August anomalies This response was also found in a study using tree rings from the Agios Epifanios station. The time series of the reconstructions in each half were calculated using the regression equation from the as an indicator of past droughts in the Aegean Sea region calibration of the other half. See Table 5 for supporting statistics. (Sarris et al., 2007). An examination for any record of temperature in the P. brutia chronologies revealed only a few significant represented by this reconstruction would include at least responses to monthly temperature. Only the higher the immediate area around the site and weather sta- site chronologies had opposite responses to tempera- tion northeast of the Troodos Mountains, and possibly ture during the winter and into the beginning of the extend over most of central Cyprus. The chronology and growing season. Temperature will affect the amount the precipitation data were divided into two segments, of evapotranspiration and thus water availability at the 1958–1983 and 1984–2009, for calibration and verifica- lower elevations, and the initiation of the growing season tion (Figure 4, Table 5), and the verification confirmed at all elevations. For the P. brutia represented in our for 1918–1957 with the Peristerona data. The chronol- study, any effect of temperature on tree-ring growth was ogy’s common signal explains 61.5% of the variance in not consistent over time. the annual September to August precipitation, which is As noted above, Agios Epifanios is the meteorolog- remarkable for a single site chronology. ical station whose annual precipitation data were used The local reconstruction is shown in Figure 5(a); the for the local reconstruction. We assumed that the area reconstruction is listed in Table S1 in the supplement. In

 2013 Royal Meteorological Society Int. J. Climatol. (2013) C. GRIGGS et al.

(a)

(b)

(c)

Figure 5. The local and regional September to August annual meteorological precipitation records compared with (a) the local annual precipitation reconstruction in central Cyprus, (b) the regional annual precipitation reconstruction for low-mid latitudes in Cyprus and (c) the regional drought reconstruction. addition to the drought years, the significantly wet years years are listed in Table 6. The two longer chronologies are well represented in this reconstruction (Figure 6(a)) from the trees at the RVA and STV sites in the middle of due to the site’s low altitude and aridity. The results and the altitudinal transect were used to extend the drought comparisons with precipitation data from other stations assessment back to 1756. The same procedures were used and other reconstructions indicate that this reconstruction as in the regional reconstruction but with the two site is consistent with the precipitation record across most chronologies rather than the PCs. Its reconstruction is of the lower altitude region of the island. The drought a record of drought years only (Figures 5(c) and 6(c)) years are included in the analysis and discussion below. from the common signal of the two chronologies. The For the regional reconstruction we included all site variance explained by the complete time series is con- chronologies in order to cover the represented altitudi- siderably reduced but there is only a slight decrease in nal gradient in the reconstruction. Principal components variance explained within the drought years (Figure 6(c), were extracted from the four sites’ chronologies. The Table 5). These drought years are included in Table 6, first component contains the variation common to all and discussed below. the chronologies with approximately equal values for the three chronologies from the higher altitude sites, and 3.4. Seasonal variability in precipitation and its record slightly less for the MSH chronology. The second com- in the tree-rings ponent contains a definite variation along their altitudinal An 11-year running mean of the seasonal precipitation transect, with MSH at one end and DST at the other. PC1 data sets over time (Figure 8) shows definite low- explains 63.9%, and PC2 21.1% of the variance; together frequency variability both between seasons across time. 85.0% of the variance is explained. The two PCs were In general, an increase in autumn and winter precipitation used in regression analyses with the regional precipitation has a positive effect on ring growth due to the amount of anomalies data to analyse the response functions. water available for the coming growth period. A decrease The calibration and verification from the PC analysis in autumn precipitation is not important when there is a on the sub-time series and sub-sample groups resulted in substantial amount of winter precipitation to offset that nearly identical reconstructions. The calibration and ver- decrease. An increase or decrease in winter precipitation ification data statistics are listed in Table 5 and shown generally has equal influence on ring growth due to in Figure 7, and the reconstruction back to 1830 is the high amount of that season’s precipitation, but is illustrated in Figure 5(b). Kienast et al. (1987) found a most important for the trees on the drier sites at lower very local record of climate parameters in tree growth elevations. with regard to both elevation and the individual sites’ For spring, decreasing and low precipitation affects terrain in the Troodos Mountains. With the combination tree growth most at the higher sites due to the importance of the four chosen site chronologies we have successfully of water availability at the onset of the growing season. reconstructed a regional drought record extending into The effects of an increasing and high precipitation in the higher elevations where temperature can also be a spring on ring growth are relative to the altitudinal limiting factor in the winter months but not consistently gradient, with MSH the most affected, and DST the least. over time, as noted above. Figure 6(b) shows the recon- Finally, summer precipitation has consistent influ- struction’s good representation of drought; the drought ence on growth only at the higher altitude sites where

 2013 Royal Meteorological Society Int. J. Climatol. (2013) A 250-YEAR PRECIPITATION AND DROUGHT RECORD FROM TREE-RINGS FOR CYPRUS

Table 6. List of years of annual, sustained and extreme sustained droughts in the reconstructions (LR = local, RR = regional, DR = drought) and in the meteorological data (LP = local, RP = regional). The bold years and letters are in the clusters of multi-year droughts in 1806–1825, 1915–1934, and 1986–2000. The extreme sustained drought of 1785–1787 is the only multi-year drought that stands alone.

Years Years Begin End Reconstruction (NA) Begin End Reconstruction Precipitation Drought reconstruction only 1902 All 1759 DR 1911 LR 1765 DR 1915 1917 All 1768 DR Regional precipitation begins 1782 DR 1925 (RR, LR) RP 1785 1787 DR 1927 1928 All RP 1794 DR 1932 1933 All RP 1806 1808 DR 1934 DR 1819 1824 DR 1941 All RP 1826 DR 1944 RR, LR 1829 DR 1947 DR Drought, regional and local 1951 (DR), RR, LR (RP) 1837 All 1953 DR 1840 All 1957 DR (RP) 1845 RR, LR Local precipitation begins 1849 DR 1959 All All 1851 DR, RR 1964 All All 1854 DR 1966 LR LP 1855 RR, LR 1970 RR, LR RP, (LP) 1870 RR, LR 1973 All All 1873 All 1986 RR, LR RP 1875 RR, LR 1990 DR RP 1879 RR, LR 1991 All All 1881 LR 1994 RP 1887 DR, RR 1997 1998 RR, LR All 1899 All 2000 RR, LR All 2008 LR LP precipitation is greater and the growing season is shorter sustained droughts and extreme sustained droughts in the due to cooler winter temperatures. In contrast, summer years of 1806–1824, 1815–1934 and 1986–2000. For precipitation has some influence on MSH ring widths, these three periods, each covering 20 years or less, about but it is effective only in years with a relatively high half of the years were drought years. Outside of those amount of summer rainfall. periods the frequency is much reduced, with one annual This finding partially indicates why the trees have drought occurring every 5–6 years over time. recorded an annual record over time. The primary growth limiting factor for the trees is a combination of all seasons, and the variations in seasonal precipitation are 4. Discussion substantial. 4.1. Current and historical perspectives 3.5. The reconstructed drought record The frequency and severity of droughts in the last two For an assessment of drought pertaining to water scarcity, decades of the 20th century plus the 2008 drought the frequency and severity of droughts were examined (Table 6) have raised serious concerns about water for possible patterns and variations in those patterns over scarcity and the future of Cyprus. Understandably, the time. We defined drought years as those with normal- consistently dry periods, especially at lower elevations, ized annual precipitation anomalies lower than −1stan- are of considerable importance to the government, and dard deviation, sustained droughts have two consecutive drought risk and concerns regarding mitigation strategies drought years, and extreme sustained drought are sus- are now prominent topics for Cyprus (Tsiourtis, 2008). tained droughts plus consecutive years with anomalies The precipitation and drought reconstructions are valid less than −0.75 standard deviations (Table 6). proxy records of low to mid-latitude inland precipitation In the meteorological data and its extensions by the due to the similarity of the local, regional and drought reconstructions there are 62 drought years over the reconstructions and the highest variance explained by the 250 year represented (Table 6). Most are annual droughts, local reconstruction from the low altitude site. but there are significant shifts in the frequency and From a historical perspective, several of the single- severity of droughts over time, with distinct clusters of and-multi-year drought periods in the local and regional

 2013 Royal Meteorological Society Int. J. Climatol. (2013) C. GRIGGS et al.

(a)

(b) Figure 7. Calibration and verification of the regional precipitation reconstruction is shown here compared to the meteorological Septem- ber to August precipitation anomalies. The regional reconstruction in each of the three segments was calculated using the regression equation from a different segment. See Table 5 for supporting statistics.

archives (Kuniholm, 1990). Other periods of reported drought, crop failure and famine in Cyprus and the immediate surrounding region (1768, 1870–1874, 1901 and 1931–1933) (Thirgood, 1987; Harris, 2007) also correspond well with our reconstruction.

(c) 4.2. Annual versus extended droughts with possible teleconnections Any drought will decrease water availability of a given year, but when a drought year occurs between years of rainfall close to or above average, its overall effect tends to be related only to that year without much impact on the following years. In contrast, the multi-year droughts have significant impact on water availability depending on their severity, duration and frequency. The multi-year droughts in the three relatively short periods reflect the low precipitation of half the represented years and a decreasing amount of available reserves, either in groundwater or stored photosynthates (Yaseef et al., Figure 6. Reconstruction versus. precipitation for the periods repre- 2010). The cause of the multi-year drought periods may sented by the meteorological data. (a) Local reconstruction vs. the be due to the impact and teleconnections of larger- local Agios Epifanios station data; (b) Regional reconstruction versus the regional precipitation and (c) The drought reconstruction versus scale climate forcings which are known to have an regional precipitation. Note the strong correlations in the drought years influence on the weather patterns and climate of the with anomalies of < −1.0 in all figures. eastern Mediterranean region. They include the NAO (Barnston and Livezey, 1987; Hurrell, 1995) and the EAWR (Krichak and Alpert, 2005a, 2012), also known reconstructions (Table 6) correspond well with historical as the North-Sea Caspian pattern (Unal et al., 2012). data from Cyprus and the northeastern Mediterranean. The effect of the winter NAO and its influence and The 1837 drought year from our reconstruction matches relationship with the EAWR on eastern Mediterranean a historical record of particularly severe crop failure climate is well known (Gund¨ uz¨ and Ozsoy,¨ 2005). The from 1836 to 1838. During this time, famine was so varying circulation patterns caused by the strength of severe that American missionaries to Cyprus reported each force over the island indicate that a positive NAO local inhabitants selling their clothing in exchange for inducing a positive EAWR has a negative effect on food, and many left the island for Syria and Asia precipitation (Krichak and Alpert, 2005a, 2005b; Unal Minor (Harris, 2007). The 1881 and 1887 drought et al., 2012). A negative NAO has minimal impact due years from the reconstruction correspond to a decade to its weaker state, but the EAWR appears to maintain during which British officials of the Cypriot colonial its inverse relationship with annual precipitation on the government report low rainfall and poor agricultural low-frequency scale, at least back to the beginning of its yields (Harris, 2007). The 1887 drought extended beyond data set in 1950. The winter NAO was mainly positive Cyprus to other neighbouring areas, with widespread from 1902–1934 to 1980–2001 (Jones et al., 1997), but drought and famine in Anatolia reported in the Ottoman the reconstructions of the winter NAO farther back in

 2013 Royal Meteorological Society Int. J. Climatol. (2013) A 250-YEAR PRECIPITATION AND DROUGHT RECORD FROM TREE-RINGS FOR CYPRUS

(a) (b)

(c)

(d)

Figure 8. The 11-year running averages of seasonal precipitation data from the four stations utilized in this study. (a) represents September through November; (b) December to February; (c) March to May and (d) June to August. The Y -axes all have the same scale except for the top portion of (b). Note the overall increasing trend in autumn (a), and decreasing trend in the winter months (b). Of significance is the slight rebound in the winter and spring groups since 1995 along with the increase in the autumn (see text for discussion). time are problematic in the late 1700 s to early 1800 s. and the lack of drought between 2000 and 2008. The While the reconstructed winter NAO of Luterbacher lower amount of winter precipitation in inland Cyprus et al. (1999) is negative for ca. 1805–1820, two other since the 1970s is still a concern, but it was at approx- reconstructions give a positive NAO during that period imately 70% in the 1990s and has increased to 90% in (Cook et al., 1998; Griggs et al., 2006). The similarity 2001–2011 relative to its average amount in1931–1960. of the extended period of drought in the early 1800 s to Finally, the end of the positive phase of the NAO at the those in the early and late 20th century indicated by the turn of the century also suggests that the drought period tree rings suggests that there was also a strong positive that began in 1986 ended in 2000. winter NAO at that time. Those three periods are when the sustained droughts occurred.

4.3. An assessment of the last severe drought period 5. Conclusions The precipitation and drought reconstructions indicate Annual precipitation and a 250-year drought record were that the two periods of extreme and sustained droughts reconstructed from four Pinus brutia tree-ring chronolo- prior to the late 20th century drought are around 20 years gies from four sites at varying altitudes in the Troodos in length (1806–1824 and 1915–1934). But can we be Mountain Massif in Cyprus. A robust local precipita- sure that the last drought ended in 2000? tion reconstruction from AD 1830 to 2008 was produced In the meteorological data of 1917 up to 2008, there for the rain-shadow area on the northeastern side of the was a slight decrease in annual precipitation despite the Massif which is relevant to one of the main population considerable decrease in winter precipitation (Figures 5 and settlement areas of Cyprus. The regional precipi- and 8). The precipitation of winter and spring, at signif- tation from the four chronologies added the variability icant lows in the last two decades of the 20th century, due to altitude and the influence of the Troodos Moun- appears to have increased very moderately at the begin- tains, but its drought record does not substantially differ ning of the 21st century (Figure 8). This increase is from the local precipitation reconstruction. The drought similar to the trends in the 1920s and 1930s (Figure 8), reconstruction was extended back to 1756 using the two suggesting that the last drought period has ended, and longest chronologies from sites between the low and that 2008 is one of the annual droughts that occur every high-altitude sites, and it represents the first longer term 5 years. A continued increase in precipitation for the early annual precipitation and drought reconstruction from the 21st century is further supported by the overall higher low to mid-elevations of Cyprus. The reconstructions also amounts of annual precipitation in Cyprus from 2009 to demonstrate the potential of Pinus brutia chronologies for 2011, at 125, 85 and 111% of the average precipitation accurate reconstruction of annual resolution climate his- for 1961–1990 (Cyprus Meteorological Service, 2013) tories and climate variability on local and regional scales.

 2013 Royal Meteorological Society Int. J. Climatol. (2013) C. GRIGGS et al.

The drought reconstruction shows that annual droughts Supporting Information occur about once every 5 years except in periods of The following supporting information is available as part sustained droughts. The sustained drought periods, of of the online article: around 20 years in length, occur every 70–100 years, Table S1: Precipitation and drought reconstructions from: with the two 20th century periods within extended Griggs et al; A 250-year annual precipitation reconstruc- positive phases of the winter NAO. With the last tion and drought assessment for Cyprus from Pinus brutia extended drought period at the end of the 20th century, (Ten.) tree-rings. it is most likely that similar conditions will not occur again until the last half of the 21st century. However, two alternative scenarios are possible. One scenario is References that the recent drought period may continue as suggested by the severe drought of 2008 despite the indications Allen DM. 1974. 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