Table 4 shows the relationship between the NAO index and the drought–flood index in Pearson and nonparametric tests. The drought–flood index and NAO index had insignificant negative correlation for the whole year, significant negative correlation in summer, and an extremely positive correlation at a test level of 0.01 in winter. The cross-wavelet spectrum was used for further discussion about the correlation between the drought–flood index and NAO index at multiple time-scales, as presented in Figure 6.
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Table 4
Correlation between NAOI and drought–flood index in the headstreams of the Tarim River Basin
| Item | Pearson test | Kendall's tau_b | ||||
|---|---|---|---|---|---|---|
| Correlation test | Annual | Winter | Summer | Annual | Winter | Summer |
| −0.067 | 0.410** | −0.311* | −0.049 | 0.271** | −0.240* | |
| Item | Pearson test | Kendall's tau_b | ||||
|---|---|---|---|---|---|---|
| Correlation test | Annual | Winter | Summer | Annual | Winter | Summer |
| −0.067 | 0.410** | −0.311* | −0.049 | 0.271** | −0.240* | |
‘**’ is significant at the test level of 0.01.
‘*’ is significant at the test level of 0.05.
Figure 6
Cross-wavelet analysis for the annual (a), winter (b), and summer (c) periods, between the drought–flood index and NAO index in the headstream mountain areas of the Tarim River.
Figure 6
Cross-wavelet analysis for the annual (a), winter (b), and summer (c) periods, between the drought–flood index and NAO index in the headstream mountain areas of the Tarim River.