Wavelet analysis was also applied to the series of two sub-divisions – Odisha and Nagaland, Manipur, Mizoram, and Tripura (NMMT) – both at the annual level and for monsoon season and the results are presented in Table 7. It is noted from this table that Sen's slope for all the components is very high for the NMMT sub-division and the declining trends in all components are statistically significant. For Odisha also, the trends are declining but not statistically significant. The approximate and detailed components for these two sub-divisions for annual and monsoon data series are presented in Figures 9–12. A notable feature here is that the approximate (a3) component of various series shows smooth variation over most duration while the d1 component has rapid fluctuations; the variations in the d2 component are in between. The Mood test brought out change points in the variance of some components, as summarized in Table 8. The presence of change points in some components indicates that the properties of rainfall-generating mechanisms at the related scale are changing at different times.
Table 8

Key statistical change parameters for NMMT and Odisha sub-divisions data series

Region and component seriesSen's slopeMK test: p- and Z-value
p-valueZ-value
Odisha – Annual 
A3 −2.858 0.180 −1.340 
A3 + D1 −2.001 0.534 −0.623 
A3 + D1 + D2 −2.289 0.572 −0.565 
Odisha – JJAS 
A3 −1.232 0.507 −0.663 
A3 + D1 −1.800 0.514 −0.653 
A3 + D1 + D2 −2.357 0.496 −0.680 
NMMT – Annual 
A3 −18.363 1.13 × 10−13 −7.424 
A3 + D1 −19.644 7.69 × 10−6 −4.474 
A3 + D1 + D2 −18.902 0.119 × 10−3 −3.848 
NMMT – JJAS 
A3 −15.399 2.2 × 10−16 −9.201 
A3 + D1 −16.753 1.53 × 10−9 −6.041 
A3 + D1 + D2 −16.192 1.81e × 10−7 −5.218 
Region and component seriesSen's slopeMK test: p- and Z-value
p-valueZ-value
Odisha – Annual 
A3 −2.858 0.180 −1.340 
A3 + D1 −2.001 0.534 −0.623 
A3 + D1 + D2 −2.289 0.572 −0.565 
Odisha – JJAS 
A3 −1.232 0.507 −0.663 
A3 + D1 −1.800 0.514 −0.653 
A3 + D1 + D2 −2.357 0.496 −0.680 
NMMT – Annual 
A3 −18.363 1.13 × 10−13 −7.424 
A3 + D1 −19.644 7.69 × 10−6 −4.474 
A3 + D1 + D2 −18.902 0.119 × 10−3 −3.848 
NMMT – JJAS 
A3 −15.399 2.2 × 10−16 −9.201 
A3 + D1 −16.753 1.53 × 10−9 −6.041 
A3 + D1 + D2 −16.192 1.81e × 10−7 −5.218 

Note: All component series had a falling trend.

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Figure 9
Decomposed components – A3, D1, D2, and D3 of Nagaland annual rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Nagaland annual rainfall time series.

Figure 9
Decomposed components – A3, D1, D2, and D3 of Nagaland annual rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Nagaland annual rainfall time series.

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Figure 10
Decomposed components – A3, D1, D2, and D3 of Nagaland monsoon rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Nagaland monsoon rainfall time series.

Figure 10
Decomposed components – A3, D1, D2, and D3 of Nagaland monsoon rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Nagaland monsoon rainfall time series.

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Figure 11
Decomposed components – A3, D1, D2, and D3 of Odisha annual rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Odisha annual rainfall time series.

Figure 11
Decomposed components – A3, D1, D2, and D3 of Odisha annual rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Odisha annual rainfall time series.

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Figure 12
Decomposed components – A3, D1, D2, and D3 of Odisha monsoon rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Odisha monsoon rainfall time series.

Figure 12
Decomposed components – A3, D1, D2, and D3 of Odisha monsoon rainfall time series.
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Decomposed components – A3, D1, D2, and D3 of Odisha monsoon rainfall time series.

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