Anomalous temperature regimen in the near-surface soil layer of Tlamacas hill and its relation to activity of Popocatépetl Volcano, Mexico

Abstract

This article describes anomalous changes in the diurnal behavior of the temperature measured in the near-surface soil at the Tlamacas monitoring site, Popocatépetl. Results of the statistical analysis show two essential changes for the temperature characteristics observed during the 2007–2009 (quiet volcano) and 2013–2014 (active volcano) monitoring periods. Under normal conditions, the absolute minimum daily temperature is observed at about 7:40 Local Time (LT) during sunrise for the atmosphere and, with a time delay, at about 8:30 LT, for soil measurements. The absolute temperature maximum is observed about 15:30 LT for the atmosphere and 16:30 LT for in-soil measurements. The dispersion of the residual temperature (24-h running trend of the temperature substituted) is 5.6 times lower for the 2013–2014 period in comparison with the 2007–2009 period. In other words, in 2013–2014, the temperature variability became 5.6 times lower that it was in 2007–2009.