<p>Sea surface temperature (SST) is a key physical attribute of upper ocean thermal conditions that provide crucial information on the earth&#8217;s climate system by playing vital role in air-sea interactions. Some regional-scale SST variations are linked to large-scale climate variability which has catastrophic consequences in the social-economic sectors of many countries. Such anomalous SST conditions in the tropical oceans causes severe impacts on the functioning of terrestrial ecosystems by altering the fluxes of heat and moisture on land, and thus threatens terrestrial carbon dynamics as well as global food security. Thus, monitoring the vegetation response to SST anomalies is fundamental to understand, quantify, and predict the effects of oceanic variability on terrestrial vegetation activity. Solar-induced chlorophyll fluorescence (SIF) is a promising plant biophysical variable that has been used for the continuous observation of global vegetation activity, especially the photosynthetic characteristics. Our study comprehensively evaluates the relationship between tropical Pacific SST variability and SIF anomalies across India to assess the spatial and temporal variability in the ocean-vegetation interactions. Overall, SIF anomaly over the Indian mainland shows negative association with SST variability in the eastern equatorial Pacific. The persistence of warm anomalies in this oceanic region forces the reduction of average SIF in all the Indian agro-climatic zones notably during the summer monsoon. While during the years of cold anomalies in the eastern equatorial Pacific, SIF appears to be enhanced. Similarly, the composite of SIF demonstrated negative (positive) anomalies during the years of positive (negative) SST anomalies. However, the implications of SST variability on the SIF anomalies are not uniform all over India even during the summer monsoon. There exist a high spatial and temporal variability in the observed SST-SIF interactions. Within the monsoon months, the influence of both positive and negative SST anomalies was predominant only during July and August across much of the Indian mainland. In addition, this oceanic influence was also significantly notable in March, particularly in the Deccan plateau. Overall, the impact of warm anomalies is comparatively stronger on the functioning of the terrestrial ecosystem in India than the cold anomalies with a limited influence mainly over the southern peninsular region. This difference in the implications of positive and negative SST anomalies is evident in all the months except during March, July, and August. Annually, SST variability in the eastern equatorial Pacific significantly contributes to the interannual variability of SIF anomalies in Gujarat plains and hills, Western plateau and hills, Southern plateau and hills, Central plateau and hills, Eastern plateau and hills, and Western dry region. The observed significant SST-SIF linkage between the eastern equatorial Pacific and the Indian vegetation was feasible through the atmospheric teleconnections. The present study provides the fundamental information that aids the early detection of possible vegetation growth anomalies to various climate extremes associated with the tropical Pacific region. This can be useful for planning long-term strategies and policies to improve precision agriculture and forest management practices in India.&#160;</p>
Sea surface temperature (SST) substantially influences the land climate conditions through the co-variability of multiple climate variables, which in turn affect the structural and functional characteristics of terrestrial vegetation. Our study explored the varying responses of vegetation photosynthesis in India to the SST variations in the tropical Indian Ocean during the summer monsoon. To characterise the terrestrial photosynthetic activity, we used solar-induced chlorophyll fluorescence (SIF). Our results demonstrated a significant negative SST-SIF relationship during the onset phase of the summer monsoon: the SIF anomalies in the northern and central Indian regions decrease when strong warm SST anomalies persist in the tropical Indian Ocean. Further, SIF anomalies increase with cold anomalies of SST. However, the negative SST anomalies in the tropical Indian Ocean are less impactful on SIF anomalies relative to the positive SST anomalies. The observed statistically significant SST–SIF link is feasible through atmospheric teleconnections. During monsoon onset, positive SST anomalies in the tropical Indian Ocean favour weakened monsoon flow, decreasing moisture transport from the ocean to the Indian mainland. The resultant water deficiency, along with the high air temperature, created a stress condition and reduced the photosynthetic rate, thus demonstrating negative SIF anomalies across India. Conversely, negative SST anomalies strengthened monsoon winds in the onset period and increased moisture availability across India. Negative air temperature anomalies also dampen water stress conditions and increased photosynthetic activity, resulting in positive SIF anomalies. The identified SST-SIF relationship would be beneficial to generate a simple framework that aids in the detection of the probable impact on vegetation growth across India associated with the rapidly varying climate conditions in the Indian Ocean.
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