Variability of lake surface water temperature: a case study during El Nino and La Nina events over the Himalayan lake region

Lake surface water temperature (LSWT) is sensitive to long-term changes in thermal structure of lakes. This paper investigates the association of LSWT with meteorological parameters and its impact during El Nino and La Nina events over the Himalayan lake region, using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data from 2001 to 2017. The observed daytime rates of change of LSWT was -0.05 degrees C/year whereas it was +0.01 degrees C/year for nighttime. The cooling of lake during daytime could be attributed to increase in rainfall and decrease in solar radiation, whereas increase in nighttime LSWT is due to increasing lowest temperature. The variability in LSWT with respect to meteorological variables during El Nino Southern Oscillation period was highest for cold phase than warm phase. There was only 1% increase in LSWT in the El Nino years (2002 and 2009), due to decreased rainfall by 95% and 56% respectively. On the other hand, the LSWT decreased in strong La Nina years of 2007 (2%) and 2010 (6%) due to the drastically increased rainfall, decreased maximum temperature and solar radiation. The correlation revealed that, in addition to the increase in temperature, the LSWT warming is consistent with the decrease in rainfall and increase in solar radiation.

Automated summary

In the Himalayan lake region, lake surface water temperature is sensitive to meteorological parameters, with significant impacts from El Nino and La Nina events, particularly changes in rainfall and solar radiation.