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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #345138

Title: The role of local heating in the 2015 Indian heat wave

item GHATAK, D. - Beijing Normal University
item ZAITCHIK, B.F. - Johns Hopkins University
item HAINS, C. - Collaborator
item Anderson, Martha

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2017
Publication Date: 10/25/2017
Citation: Ghatak, D., Zaitchik, B., Hains, C., Anderson, M.C. 2017. The role of local heating in the 2015 Indian heat wave. Scientific Reports. 7:7707.

Interpretive Summary: Extreme heat waves can have significant negative impacts on human and livestock health, and on agricultural production. Understanding the drivers of heat waves can help to improve predictability and mitigation of future events. This study looks at a severe heat wave that affected India in 2015 and manifested in two peaks: one in May and a second in early June. The question we investigate is whether the condition of the land-surface at the time of the heat wave (wet versus dry) potentially played a role in exacerbating the temperature anomaly by accelerating local heating of the overlying air mass. The study compared several surface diagnostics including remotely sensed estimates of sensible heating - the heating flux from the land to the atmosphere - derived from an energy balance model developed by ARS scientists. We find that in the first peak of the Indian heat wave of 2015, the sensible heat flux was low because the land-surface still had residual soil moisture available for evaporative cooling. However in the second peak, this moisture reserve had already been eliminated and the sensible heat flux was significantly higher. In this case, the local heating from the dry land-surface added to the temperature anomaly created by the larger-scale atmospheric dynamics. This information may be useful in developing remotely sensed diagnostics that could provide an early warning of heat wave intensity and impact.

Technical Abstract: India faced a major heat wave during the summer of 2015. Temperature anomalies peaked in the dry period before the onset of the summer monsoon, suggesting that local land-atmosphere feedbacks involving desiccated soils and vegetation might have played a role in driving the heat extreme. Upon examination of in situ data, reanalysis, satellite observations, and land surface models, we find that the heat wave included two distinct peaks: one in late May, and a second in early June. During the first peak we find that clear skies led to a positive net radiation anomaly at the surface, but there is no significant sensible heat flux anomaly within the core of the heat wave affected region. By the time of the second peak, however, soil moisture had dropped to anomalously low levels in the core heat wave region, net surface radiation was anomalously high, and a significant positive sensible heat flux anomaly developed. This led to a substantial local forcing on air temperature that contributed to the intensity of the event. The analysis indicates that the highly agricultural landscape of North and Central India can reinforce heat extremes under dry conditions.