Fires Causing Persistent Haze Across Southeast Asia

Fires are persisting across Indonesia and causing transboundary haze and respiratory health problems for people in neighboring countries like Malaysia and Singapore. This image from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA-21 platform shows thick smoke emanating from wildland fires in the Kalimantan region of Indonesia. Red dots indicate places where VIIRS detected heat signatures indicative of active fires or smoldering landscapes.

This view shows an overlay of the aerosol index layer at 380nm, also from the VIIRS instrument on NOAA-21. While the deepest reds mark the thickest smoke over Kalimantan, yellows and oranges indicate areas where smoky, particle-laden air has been detected over other countries. 

The aerosol index at 380nm indicates the presence of ultraviolet (UV)-absorbing particles in the air, such as desert dust, volcanic ash, and smoke particles. The index is related to both the thickness of the aerosol layer and to the height of that layer in the atmosphere. The index is a unitless value that typically ranges from 0 to 5, with higher values indicating heavier particle concentrations that could reduce visibility or impact human health.

Drier-than-usual conditions, drought and delayed rainfall due to El Niño have been exacerbating fires in the region. 

Ground-based instruments in the Aerosol Robotic Network (AERONET), marked by colored dots, show high aerosol optical depth (AOD) values—especially at the sites in Pontianak, Indonesia, Jambi, Indonesia, and Singapore. Click on each AERONET site to view the local AOD value.

Aerosol optical depth (AOD) (also known as aerosol optical thickness) indicates the level at which particles in the air prevent light from traveling through the atmosphere. Aerosols scatter and absorb incoming sunlight, which reduces visibility. From an observer on the ground, an AOD of less than 0.1 is “clean” air—characterized by clear blue skies, bright sunlight, and maximum visibility. As AOD increases to 0.5, 1.0, and greater than 3.0, aerosols can become so dense that the Sun is obscured.

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