## 3 Results
### The SST-SIF Link after the Onset of the Summer Monsoon  
The characteristic inverse tropical Indian Ocean SST influence on SIF anomalies weakens considerably over the Indian mainland after June. Overall, the association between SST anomalies of the individual Indian Ocean regions and SIF anomalies across India seems to weaken after the monsoon onset (Table 5). Meanwhile, mostly statistically significant positive SST-SIF associations were observed once the monsoon establishes across the country. The composite of SIF anomalies also demonstrated these varying responses of vegetation photosynthetic activity to the tropical Indian Ocean SSTs (Figures S1-S3). The well-defined patterns of negative SST-SIF relations discovered during the onset phase of the monsoon (Figure 5) then appeared as a mixed and irregular relationship in July (Figure S1), August (Figure S2) and September (Figure S3). However, in July, notable positive SIF anomalies were observed across SPH, WPH, GPH and WDR as a result of warm SST anomalies in WIO (Figure S1a). In contrast, considerable negative SIF anomalies in the same region are found only when cold SST anomalies persist mainly in the CIO region (Figure S1f). In August, positive and negative SIF anomalies concentrated across WDR in response to the positive and negative SST anomalies in the CIO, respectively (Figure S2c,f). As the  
Figure 6: Regions showing statistically significant composite anomalies of specific humidity (kg/kg) across India during the month of June when SST anomalies of the Western Indian Ocean (**a,d**), Northern Indian Ocean (**b,e**) and Central Indian Ocean (**c,f**) demonstrated positive (upper) and negative (lower) variations. The colour bar shows the scaled density estimate of negative (orange) and positive (blue) specific humidity anomalies. The warmer SST in the oceanic regions leads to negative specific humidity anomalies, while the colder SST leads to positive specific humidity anomalies in the shaded areas. (Software used: Python version 3.7 (2019), [[https://www.python.org/](https://www.python.org/)]([https://www.python.org/](https://www.python.org/)) (accessed on 8 November 2021) and R version 4.0.5 (2021), [[https://www.R-project.org/](https://www.R-project.org/)]([https://www.R-project.org/](https://www.R-project.org/)) (accessed on 6 November 2021)).  
monsoon withdraws in September, SIF anomalies over India failed to vary in relation to the SST anomalies in WIO, NIO and CIO (Figure S3). However, the cause-effect chain of SST and SIF was found to be weak in July (Figure S4i-iv), August (Figure S5i-iv) and September (Figure S6i-iv), and the observed composite anomalies did not complement each other. This points to the complexity of the physical processes associated with each phase of the summer monsoon.  
Figure 8: Regions showing statistically significant composite anomalies of soil moisture (m\({}^{3}\)/m\({}^{3}\)) across India during the month of June when SST anomalies of the Western Indian Ocean (**a**,**d**), Northern Indian Ocean (**b**,**e**) and Central Indian Ocean (**c**,**f**) demonstrated positive (upper) and negative (lower) variations. The colour bar shows the scaled density estimate of negative (orange) and positive (blue) soil moisture anomalies. The warmer SST in the oceanic regions leads to negative soil moisture anomalies, while the colder SST leads to positive soil moisture anomalies in the shaded areas.  
Figure 7: Regions showing statistically significant composite anomalies of rainfall (mm) across India during the month of June when SST anomalies of the Western Indian Ocean (**a**,**d**), Northern Indian Ocean (**b**,**e**) and Central Indian Ocean (**c**,**f**) demonstrated positive (upper) and negative (lower) variations. The colour bar shows the scaled density estimate of negative (orange) and positive (blue) rainfall anomalies. The warmer SST in the oceanic regions leads to negative rainfall anomalies, while the colder SST leads to positive rainfall anomalies in the shaded areas.