Heating of lake Voui detected by MODIS on November 19, 2005.


MODIS satellites have a more frequent coverage than ASTER but their spatial resolution is only 1 km.
The surface area of Lake Voui (2.1 km2) is too small for an accurate measurement of lake temperature with the poor resolution of MODIS. Anyway, MODIS can detect rough changes in lake temperature or an increase in thermal anomaly.


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MODIS SST (MOD28L2 product) showing a strong thermal anomaly on November 21, 2005. Approximate lake temperatures measured were 30.4°C on November 20 and 29.5°C (Terra)/ 31.4°C (Aqua) on November 21. On November 25, Terra (at 11:10 UTC) and Aqua (at 14:10 UTC) give the same temperature: 42.2°C. These temperatures are likely to be a minimum, i.e. the real temperatures are probably a little bit higher. MODIS pixel footprint is about 1km along track and 2 km across track. In consequence, the measured temperatures are a mixed signal corresponding to the lake and some signal from the adjacent tropical forest (much colder than the lake at night at this elevation). Background temperatures measured with ASTER during the period Sept. 2002-Oct. 2005 were much lower with a maximum at 26.3°C.



ASTER_SW and MODIS SST data of lake Voui. (last update June 21, 2006)

Red arrow is November 27, eruption.





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