Interactive comment on “ Climate field reconstruction of East Asian spring temperature ”

Both referees identify added value in the manuscript but also make a series of suggestions that the authors should heed to improve the manuscript. In their response, the authors essentially agree with most suggestions, and therefore, the submission of a revised version is encouraged. In the exchange between reviewers and authors a few points have been raised that, in my view, are important enough to be included in the revised abstract, and which were absent in the initial submission. I would suggest to include in the revised abstract that: the reconstruction is considered skilful for interannual time-scales but not for longterm change (the original abstract needs to be corrected on this point)


Introduction
The East Asian Monsoon (hereafter EAM) is an important component of the Earth's climate system, and influences the societal and economic activity of one quarter of the World's population.In addition to studies of instrumental data, a dense network of long-term palaeoclimatic records (e.g.documentary records and dendroclimatic reconstructions) is crucial in order to better understand the EAM.In East Asia, documentary reconstructions demonstrated regional/wide-area climate conditions (e.g.temperature and pressure patterns) in the late Little Ice Age (e.g., Maejima and Tagami, 1983;Hirano and Mikami, 2007;Ge et al., 2007).Zaiki et al. (2006)  these back to 1820 in western Japan (hereafter referred to as the west-Japan temperature series).Dendroclimatic reconstructions using climatically sensitive chronologies, however, are sparse for the mid-latitude East Asian Pacific rim despite recent efforts to improve their coverage (Choi et al., 1994;Gostev et al., 1996;Davi et al., 2002;Jacoby et al., 2004;Yonenobu and Eckstein, 2006;Zhu et al., 2009).Although those recent studies for improving this coverage provide reconstructed regional temperatures, climatic field reconstruction (CFR) of temperature has never been reported in this region.The purpose of the present study is to reconstruct the regional scale spring temperature for East Asia by CFR, using a network of spring-temperature-sensitive regional tree-ring chronologies, including a new tree-ring record from north-eastern Japan.The potential of this reconstruction is evaluated in comparison to other proxy-based reconstructions for East Asia.

Meteorological data
A gridded land air temperature dataset (CRUTEM3) and a combined land/marine temperature dataset (HadCRUT3) (Brohan et al., 2006) were used.We selected the datasets from 5 • latitude/longitude grids between 30-45 • N and 125-145 • E for CFR analysis (shown with dotted lines in Fig. 1).An average land air temperature dataset from the grids with solid lines (between 35-40 • N and 125-140 • E) (Fig. 1) was finally used to obtain an optimal CFR model after the calibration trials.

Tree-ring records
We used a total of seven ring-width chronologies to examine the performance of the CFR models.As shown in Table 1, six of these were derived from previous studies (Kojo, 1987;Choi et al., 1994;Yonenobu and Eckstein, 2006).To improve the spatial Introduction

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Full coverage, we developed a new ring-width chronology of Japanese cedar (Cryptomeria japonica) in north-eastern Japan for the period of 1784-2003.These series are all sensitive to spring temperature.Because of their unsubstantial coherency with the other records, JAPA001 and 007 were eliminated during the calibration trials.After calculating the principal components (PCs) for the remaining five chronologies over their common interval (1784-1990), PC1 and PC2 (with eigenvalues > 1) were used for CFR.

Calibration and verification
Simple correlation analysis was performed between the PCs and the averaged temperature between 1887 and 1990.Based on this correlation analysis, principal components regression (PCR) was performed to derive a transfer function.All mean temperature subsets (February-May) were examined as candidate predictants.Finally, we obtained the optimal CFR model for estimating March-May mean land temperature over the 35-40 • E, 125-140 • N region.Since some divergence was observed between the actual and estimated CRUTEM3 data during the calibration trials, a frequency range higher than approximately 60 yr was removed by subtracting a high-pass filtered curve from the original data to remove the upward bias in the actual data series.This model was further examined using a split period calibration-verification method between 1887-1938 and 1939-1990.The full 1887-1990 period was used to develop the final reconstruction.The statistical methods used in evaluating the reconstruction were Peason's correlation, the reduction of error (RE), coefficient of efficiency (CE), and the sign test.A positive RE or CE indicates a valid reconstruction (Cook et al., 1994).Positive values for the sign test denote the correct sign for the reconstruction (Fritts, 1976).A residual analysis was also performed using the Durbin-Watson statistic and 1st order autocorrelation (AR 1 ) for the residuals of the final reconstruction.
The final calibration model accounts for 19.4 % of the total variance and passes all the calibration tests (Table 2).A residual analysis demonstrates that the residuals due Introduction

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Full to regression show no significant autocorrelation (DW = 1.939,AR 1 = 0.03).The split models also pass the statistical tests (p < 0.05 or positive RE/CE except for the CE slightly below zero).Intervention analysis was applied to the reconstruction to identify significant regime shifts (p < 0.05), in which the mean values of 15 yr periods were compared on either side of each year (Rodionov, 2004).
Figure 3a shows the visual comparison between the estimated and actual mean March-May gridded temperature over the 35-40 • N, 125-140 • E region.A pronounced upward trend for the unfiltered actual CRUTEM3 data is observed, leading to the divergence between the actual and estimated CRUTEM3 data, despite their fairly good agreement of year-to-year variations.This trend is mostly eliminated for the filtered CRUTEM3 data.

Correlations between principal components and temperature data
PC1 correlates significantly with spring and summer temperature (positive), whereas PC2 correlates significantly with spring temperature (positive) and previous summer temperature (negative) (Fig. 2).According to the loadings of the correlation matrix (data not shown), PC1 (29.0 % of the variance) represents the Korean chronologies, while PC2 (25.3 % of the variance) represents the Japanese chronologies.Therefore, in this study, the geographic pattern is more significant than the difference between species.  .Specifically, the cold periods identified were 1807-1820 (period II), 1835-1846(period II), and 1904-1919 (period V) (period V), respectively.Higher interannual fluctuation can be observed in period I (1792-1806).Period IV shows lower interdecadal variability, indicating slightly above-average temperature.

Reconstructed East Asian spring temperature
The intervention-analysis generated six regime shifts at 1807, 1821, 1835, 1847, 1904, and 1919, giving a consistent result with the above mentioned cold periods (Fig. 3b).

Comparison between REAST and the regional reconstructions
REAST largely corresponds to the regional spring temperature reconstructions in Japan and Korea (Fig. 3c-f), despite the differences of estimated months.Figure 3c shows a 31-yr interval moving correlation between REAST and the regional reconstruc- estimated from old diaries by a different method, indicating a period of cool conditions in 1824-1841 (Hirano and Mikami, 2007).Spring temperature reconstruction from historical documents for the Pacific coastal region of southern China shows a cold period from the 1790s to the 1840s, with a short-term warm period around the 1820's (Wang et al., 1991).This finding agrees well with our reconstruction (I-III).Annual temperature reconstruction for eastern China using a 14 document-based series (Ge et al., 2007) also partially supports to our reconstruction, in which the Little Ice Age continued from the 1770s to the end of the 19th century.Their result is consistent with our reconstruction in the first half of the 19th century (I-III), but not in the second half (IV).

Recovered instrumental records
Recovered instrumental records (March-May) for west-Japan spring temperature (WJST) (Zaiki et al., 2006) show cold periods in the 1830s and the 1880s, and a short warming in the 1850s.These trends show notably good agreement with REAST except for the cold period of the 1880s, which, nevertheless, corresponds well to the Japanese reconstructions (Fig. 3e-f).This cold period is likely to be regionally limited to Japan.Actually, the correlation between February-April temperature for central Japan (Fig. 3e) and WJST (r = 0.542, p < 0.001) is higher than that between REAST and WJST (r = 0.382, p < 0.001) for the period of 1863-1990.

Other reconstructions and historical episodes
REAST might contribute to describing the past behavior of the EAM.The reconstruction of the December-February Siberian High Index (1599-1980) (D'Arrigo et al., 2005a) is generally consistent with REAST, particularly in the late 17th and the early 18th centuries (I-III).This is not the case in the 1830s, however, when little association is found between REAST and the extended East Asian Winter Monsoon Index (EAWMI) as computed from the SHI and the North Pacific Index (NPI) (D'Arrigo et al., 2005b); correlation between EAWMI and REAST is not significant.This fact may be attributed Introduction

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Full to the seasonal difference between REAST (March-May) and EAWMI (December-February).
Our reconstruction and the regional chronologies used do not show any abrupt depression after the Tambora (1816) volcanic eruption (Fig. 3b, d-f).REAST exhibits the lowest temperature anomaly in 1814 and an increasing trend after 1815 in period III.
It is possible that the Tambora eruption did not influence tree growth of the springtemperature-sensitive species we investigated.Moreover, the Laki (1783) eruption is also not detected in REAST.
A great famine occurred between 1832 and 1839 in Japan (Nishimura and Yoshikawa, 1936).Although famines in premodern Japan have generally been attributed to lower summer temperature which caused bad crops of rice, our reconstruction shows spring temperatures in Korea and Japan were also cold in the prolonged famine period (period III).

Conclusions
We have reconstructed the mean March-May temperature over 35-40 • E, 125-140 • N for the period of 1784-1990 using dendroclimatic field reconstruction.The reconstruction accounted for 19.4 % of the temperature variance in the calibration period and showed interdecadal fluctuations remarkably similar to the regional dendroclimatic reconstructions in Japan and Korea, indicating the past coherent spatial variations of the spring temperatures across the region.In spite of the lower explained variance for our reconstruction, we believe the result is remarkable because corresponding temperature fluctuations have been demonstrated across the region including the Korean Peninsula and the Japanese archipelago.Our reconstruction shows fairly good agreement with cold periods estimated from documentary records in China and Japan.The recovered west-Japan temperature series also showed a reasonable agreement with this reconstruction.Accordingly, these comparisons revealed that climatic field reconstruction from chronologies in this area offers a good potential for reconstructing long-term and

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Full large-scale past temperature patterns for East Asia.Further studies for reconstructing broader scale climate should be conducted in East Asia including Northeast China, in which the spatial coverage of chronologies is being improved (Zhu et al., 2009).Introduction

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Full  Full  Full recovered instrumental temperature records before official meteorological observations in Japan and extended Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Figure
Figure 3b shows the reconstructed mean March-May gridded temperature over the 35-40 • E, 125-140 • N region with interdecadal variations obtained by a 10-yr low-pass filter.The 1887-1990 mean (−0.065 • C) is shown to display cold and warm periods.The reconstructed East Asian spring temperature (REAST) demonstrates abrupt interdecadal fluctuations including below-average cold times within periods II (1807- tions.The three reconstructions demonstrate positive significant correlations (p < 0.05) for most of the common interval, indicating high coherency.The four reconstructions display remarkably similar interdecadal fluctuations in periods II and III, with a cold-warm-cold pattern in each.Common interdecadal variations are also observed in periods IV and V; period IV shows lower interdecadal variations near the average temperature and period V shows cold intervals.On the contrary, a divergence is observed among the reconstructions in period I; those in Japan show a cold period, and those in Korea and REAST show a relatively warm period.Documentary reconstructions show good agreements with our results.Fukaishi and Tagami (1992) reconstructed frequencies of a winter-type pressure pattern across Japan from old diaries over the period of 1720-1869, and suggest that extraordinarily cold conditions occurred during 1808-1819 (II) and 1826-1841 (III).Frequencies of the winter monsoon weather patterns across Japan during the 19th century were also Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Asia. how forest sites.The grids with dotted and solid lines show the temperature data used for calibration he final calibration, respectively.

Fig. 1 .
Fig. 1.Map of northeastern Asia.Symbols show forest sites.The grids with dotted and solid lines show the temperature data used for calibration trials and the final calibration, respectively.

Fig. 3 .
Fig. 3. (a) Estimated (solid line), and actual (dotted line) March-May (MAM) temperature anomalies.The actual record (orange line) is prewhitened to fit the low-frequency variability to the estimated series (see black dotted line).The left axis is for filtered actual and estimated records; the right axis for the actual record.(b) Reconstructed spring (MAM) temperature for East Asia.The horizontal red lines show regime shifts detected using intervention analysis (Rodionov, 2004).(c) 31-yr running correlations between REAST and the regional reconstructions (d-f): (d) C. Korea, April-May, (e) C. Japan, February-April (f) NE Japan, April temperatures.

Table 1 .
List of chronologies.

Table 2 .
Calibration and verification statistics for the East Asian March-May temperature reconstruction.