Earlier this month, air temperatures in New Delhi reached an astounding 118° F (43° C). Then, for a period of seven days, temperatures remained above 110° F (43° C). Satellite data now shows the extent of this unprecedented event.


The top map shows land surface temperature anomalies (LST) for southern Asia from June 2-9. Below shows LST from June 10-17.


LST anomalies are not absolute temperatures. Rather, they show how much the land surface was heated above or below recorded average. Those super-dark red areas in south India show where the ground was as much as 12° F (22° C) above the norm from 2001 to 2010. Blue areas are normal, while grey depict areas with incomplete data.

Interestingly, the maps don't actually convey the true extent of the heat wave. NASA's Earth Observatory explains:

[Neither] map fully captures the heatwave that occurred in northern and central India because it overlapped two different weeks of data. Each map shows an average of eight days, so the extreme temperatures of individual days gets smoothed out by the average to cooler temperatures on other days in the period. The extremes around New Delhi also might not show up as brightly in this map because temperatures were about 5°C above the norm while other areas went as much as 12°C above.

Also, the maps also reveal the arrival of something else: A monsoon.

Note how much of central and western India is cooler in the second week; there are also several gray areas where cloudiness masked out measurements of the ground. Rainfall, cloud cover, and moist breezes from the Arabian Sea likely explain the change in land surface temperatures. India's meteorological agency noted that the monsoon has arrived, but rainfall in the June to September period is expected to be weaker than normal.


Monsoons can be devastating, but this one will likely be welcomed — for a while anyway.

[ ESO ]

NASA Earth Observatory image by Kevin Ward, using data from the Land Processes Distributed Active Archive Center (LPDAAC).