Summer Drought Patterns in the Middle-Lower Reaches of the Yangtze River Basin and Their Connections with Atmospheric Circulation before and after 1980

Figure 3

The normalized principal components (PCs): (a) PC1 and (b) PC2. (c) The moving test (MTT) of the first two PCs, in which red (black) solid line indicates MTT statistics of the PC1 (PC2) and dotted lines indicate 99% confidence level. (d) The scatter diagram of the PC1 versus PC2 for 1961–2013, in which the WBWD, SDNF, and SFND years are colored in red, blue, and green, respectively. Red line in (a) denotes trend line of PC1, significant at 95% confidence level for the Mann-Kendall trend test, and red lines in (b) denote mean value of 1961–1991, 1992–2002, and 2003–2013.

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