Fig. 1
Instrumental ISMR (red) and the AMV-index (based on Kaplan Extended SST V2 data) from June to September (blue) smoothed with an 11-yr moving average (1856–2010).
Fig. 2.*
(a) Locations of the 19 selected stations. Mountainous regions (hatched) were not considered for the study. The stations are AMT (Amraoti), BMB (Bombay), BNG (Bangalore), BRL (Bareilly), DSA (Deesa), DLH (Delhi), FZP (Ferozepur), GRK (Gorakhpur), HYD (Hyderabad), JBP (Jabalpur), MDS (Madras), NGP (Nagpur), PTN (Patna), PNE (Pune), PRI (Puri), RPR (Raipur), SMG (Shimoga), SNI (Seoni) and VNS (Varanasi). The locations of the three tree-ring sites used in KTRC are marked in red. The locations of Dandak and Jhumar caves are marked in blue (adapted from Sontakke et al., 1993). (b) Network of 306 rain gauge stations over the area considered excluding hilly area (hatched) (Mooley and Parthasarathy, 1984).
*The geographical boundaries shown in this figure do not necessarily correspond to the political boundaries.
Table 1. Dry and wet years of ISMR.
Period 1844–1870
1844–1850824.41848–1851–1860829.61851, 1855, 1860–1861–1870895.018641861, 1862, 1863, 1867, 1870Period 1871–2010
1871–1880849.91873, 18771874, 18781881–1890881.418841891–1900865.518991892, 1893, 18941901–1910822.41901, 1904, 190519101911–1920821.31911, 1918, 19201916, 19171921–1930837.2––1931–1940871.3–19331941–1950888.819411942, 19471951–1960871.419511956, 19591961–1970844.41965, 1966, 19681961, 19701971–1980840.21972, 1974, 197919751981–1990831.51982, 1985, 1986, 19871983, 19881991–2000837.9–19942001–2010811.12002, 2004, 20092007
Table 2. Available ISMR proxy reconstructions
KTRCTree ringRing width1481–2003Kerala, IndiaAnnualBorgaonkar et al., 2010SMMRTree ringRing width1602–1960GlobalAnnual1988SASMTree ringRing width896–2000AsiaAnnualShi et al., 2014Dandak CaveSpeleothemδ18O600–1500Central India~Annual2007Jhumar CaveSpeleothemδ18O1075–2008Central India~AnnualSinha et al., 2011Palmyra coralCoralδ18O1635–1702Equatorial PacificSeasonalChakraborty et al., 2012
Fig. 3
SMMR (blue) and instrumental ISMR (black) for the period 1871–1960.
Fig. 4
Standardised anomalies of instrumental ISMR (black) and SASMI (green) for the period 1871–2000.
Fig. 5
The correlation between IMDGRD data and (a) KTRC, (b) SASMI and (c) instrumental ISMR for the period 1901–2000. For KTRC, the correlation is calculated by representing dry years by 1 and non-dry years by 0. Contours show correlations significant at 90% confidence level. The black box indicates the Central India box (72°E–85°E, 21°N–27°N).
Fig. 6
The correlation between IMDGRD data and (a) SMMR and (b) instrumental ISMR for the period 1901–1960. Contours show correlations significant at 90% confidence level. The black box indicates the Central India box (72°E–85°E, 21°N–27°N).
Table 3. Available AMV proxy reconstructions used in this study
Gray-AMVTree ring1567–1990Gray et al., 2004Mann-AMVMulti-proxy500–2006Mann et al., 2009Svendsen-AMVCoral1781–1986Svendsen et al., 2014
Fig. 7
ISMR reconstruction made with (a) KTRC (red), (b) SMMR (blue) and (c) SASMI (green), where dry years are represented by 1 and non-dry years are represented by 0, and then an 11-yr moving average has been performed. The bars show the number of dry years per 11-yr period divided by 11 (probability of a dry year). The 11-yr moving average of instrumental ISMR with dry years represented by 1 and non-dry years by 0 is shown in black in all panels.
Table 4. Epochs of frequent dry years from 1481 to 2003 derived from KTRC
(A1) 1484–15151484, 1486, 1491, 1492,1508,1510,1512,1514,1515(B1) 1539–15711539, 1540, 1541, 1552,1564,1565,1569,1570,1571(C1) 1652–17031652, 1656, 1663, 1665, 1666, 1676, 1680, 1681, 1691, 1693, 1694, 1696, 1700, 1703(D1) 1760–17671760, 1761, 1763, 1765, 1767(E1) 1791–18771791, 1794, 1802, 1803, 1811, 1812, 1814, 1818, 1821, 1824, 1829, 1832, 1833, 1837, 1838, 1844, 1853, 1865, 1868, 1873, 1877(F1) 1896–19181896, 1899, 1901, 1904,1905,1908,1911,1914,1915,1918(G1) 1941–19871941, 1944, 1945, 1949, 1951, 1954, 1959, 1965, 1966, 1967, 1968, 1972, 1979, 1982, 1987
Table 5. Epochs of frequent dry years from 1602 to 1960 derived from SMMR
(A2) 1676–17201676, 1679, 1682, 1688, 1700, 1702, 1705, 1717, 1720(B2) 1743–17761743, 1746, 1747, 1754, 1755, 1758, 1760, 1768, 1769, 1775, 1776(C2) 1790–18111790, 1792, 1799, 1807, 1808, 1811(D2) 1863–18761863, 1864, 1868, 1876(E2) 1897–19301897, 1899, 1902, 1904, 1911, 1912, 1913, 1914, 1918, 1925, 1930
Table 6. Epochs of frequent dry years from 1481 to 2000 derived from reconstructed SASMI
(A3) 1481–14951481, 1482, 1484, 1492, 1495(B3) 1600–16031600, 1602, 1603(C3) 1651–16631651, 1653, 1663(D3) 1902–19311902, 1905, 1914, 1915, 1920, 1926, 1931(E3) 1965–19921965, 1966, 1968, 1976, 1979, 1980, 1982, 1983, 1986, 1987, 1991, 1992
Table 7. Linear correlation coefficients between AMV and ISMR indices normalised and smoothed with an 11-yr moving average for the period 1856–1986.
Observed AMV0.83a (0.83a, 1856–1990)0.55c (0.54c,1856–2006)0.52c (0.52c,1856–1986)0.64a (0.43c,1856–2010)0.35 (0.33,1844–2000)0.52c (0.52c,1856–1960)0.66a (0.61a,1856–2000)Gray- AMV0.78a (0.50a,1567–1990)0.42c (0.33,1781–1986)0.55b (0.51b,1844–1990)0.26 (0.06, 1567–1990)0.27 (−0.03,1602–1960)0.40 (0.05,1567–1990)Mann-AMV0.39 (0.47c,1781–1986)0.30 (0.03,1844–2006)0.07 (−0.07,1491–2000)0.22 (−0.19,1602–1960)0.11 (−0.12,1481–2000)Svendsen-AMV0.49c (0.48b,1844–1986)0.16 (0.10,1781–1986)0.83a (0.46b,1781–1960)0.59b (0.45b,1781–1986)Observed ISMR0.42 (0.32,1844–2000)0.56c (0.45c,1844–1960)0.57a (0.54a,1844–2000)KTRC0.57b (0.41b,1602–1960)0.29 (0.11,1491–2000)SMMR0.82a (0.25c,1602–1960)
[i] The values in parenthesis give the correlation during the entire record length and the years covered. # Linear correlation coefficient is calculated for the common period 1856–1960. a,b,cValues appearing with the superscripts a, b and c indicate significance at a confidence level of 99, 95 and 90%, respectively, for the effective degrees of freedom. AMV, Atlantic multidecadal variability; ISMR, Indian summer monsoon rainfall; KTRC, Kerala tree ring chronology; SASMI, South Asian summer monsoon index; SMMR, statistical model monsoon rainfall.
Fig. 8
(a) Instrumental AMV and ISMR, (b) proxy reconstructed AMV (Gray-AMV, Mann-AMV and Svendsen-AMV) and (c) proxy reconstructed ISMR (KTRC, SASMI and SMMR). All the time series data are normalised and smoothed using an 11-yr moving average, except Mann-AMV which is only available as a filtered product.