The ongoing eruption of Mount Merapi on the Indonesian island of Java has disrupted the lives of thousands of local residents, who live in the shadow of this active volcano, partly due to the agricultural richness created by the fertile volcanic soils on its slopes. Pyroclastic flows and ash deposition from a series of strong explosion events have caused hundreds of fatalities and required the evacuation of the local region. Despite the continuing danger from the volcano, some residents are trying to move back to their damaged homes already.
The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument acquired the true-color image below, showing the erupting ash plume from Mount Merapi on November 10, 2010. (Image and labeling courtesy of the NASA Earth Observatory.)
Figure 1. MODIS-Terra true-color image of the ash plume from Mount Merapi, observed on November 10, 2010.
The threat posed by clouds of sulfur dioxide (SO2) and ash erupted into the atmosphere from Merapi caused the cancellation of airplane flights during some days of the eruption, and even affected the travel itinerary of U.S. President Barack Obama during his state visit to Indonesia.
The GES DISC Interactive Online Visualization ANd aNalysis Infrastructure (Giovanni) provides data from several NASA satellites that allow monitoring of the atmospheric effects of the Merapi eruption. The Ozone Monitoring Instrument Level 2 Gridded (OMIL2G) interface provides daily SO2 data, which show the movement of the SO2 aerosol cloud over the eastern Indian Ocean during the series of eruptions occurring between November 5 and November 12. (Compare this image to the animation of data from the European Space Agency's Infrared Atmospheric Sounding Interferometer on the MetOp satellite.)
Figure 2: SO2 column amount (in Dobson Units, DU) from the Giovanni OMIL2G interface, for the period November 5-12, 2010, showing the movement of the SO2 aerosol cloud erupted from Mount Merapi.
The MODIS instrument on the Aqua satellite allows observation of the areas which were impacted by the heavy ashfall from Merapi. A composite image averaging the daily data acquired by MODIS for the period of November 5-12 demonstrates that the ash was primarily erupted over the central and western regions of the island, consistent with the MODIS image in Figure 1. Examining the daily data images from MODIS which were averaged to produce the image below shows that major ash eruption events were observed on November 6, 9, and 11. The daily images have missing data due to clouds, and the coverage gaps between the instrument's daily scanning area.
Figure 3. Averaged Aerosol Optical Depth (AOD) at 550 nm from the MODIS instrument on the Aqua satellite, for the period November 5-12, 2010. This image shows the regions on the island of Java most affected by ash from the eruption of Mount Merapi.