Delayed impact of El Niño on the spring surface air temperature over India

Abstract

Air temperature variability and prediction is important considering the potential implications on human health, water resources management, agriculture and land-atmosphere interaction. In this paper, we investigate the delayed in uence of El Niño on spring Surface Air Temperature (SAT) variability over India using observations and assessed its predictability in coupled climate models. Analysis suggests that El Niño, at its decaying phase, exerts strong in uence on the spring SAT over India. It is found that SAT over India is abnormally warmer, especially over southern peninsular India in the El Niño decaying spring. It is found that this strong SAT warming is mainly induced by anomalous anticyclonic circulation extending from the Western North Paci c (WNP) region to southern peninsular India. This anomalous anticyclone induced downdraft reduces the speci c humidity anomalies in the lower troposphere and leads to decreased cloud cover over the southern peninsular India. As a result of this, shortwave radiation is enhanced at the surface, which causes anomalous SAT warming over India. It is found that 60% years out of top 10 warmest years over the southern peninsular India correspond to the decaying phase of El Niño, suggesting the importance of the present study. It is also found that the strong SAT warming over southern peninsular India aids to increase Discomfort Index (above 28 and 30 o C hours/day) and Universal Thermal Climate Index during El Niño decaying spring years. Further, we have examined the predictability of the spring SAT during decaying El Niño years based on the Asia-Paci c Economic Cooperation Climate Center (APCC) models. It is noted that most of the APCC models reasonably well predicted the spatial distribution of warm SAT over India during the El Niño decaying spring season at 1 and 3 month leads. This study highlights the predictability of spring SAT a season in advance over India, which would in turn help in planning better adaptation and mitigation strategies.