Air Particles in Indochina Captured by GCOM-C

The Global Change Observation Mission – Climate (GCOM-C) was launched from the JAXA Tanegashima Space Center in 2017, and has been successfully observing the Earth. We will introduce the state of air pollutants captured by GCOM-C.

Satellites can observe air pollutants on a large scale. JAXA’s GCOM-C is capable of observing atmospheric particles such as PM2.5 and dust on a global scale. In particular, the use of polarization measurement, which is one of the features of GCOM-C, makes it easier to detect small particles such as PM2.5 than before.

Figure 1 are images observed by GCOM-C at around 10:00 on January 29, 2019 (Indochina time). The left figure is an RGB image close to what the human eye sees (image with red, green, and blue band observation data allocated to RGB). The land of the right figure is a polarization image (polarization radiance (unit) W/m²/µm/sr). In the right figure, when the polarization radiance is high (shown by the red color), it indicates that the concentration of smaller particles is higher. At this date and time, high polarized radiance is observed from western and southern Thailand to southern Cambodia and Vietnam.

Figure 1. Images observed by GCOM-C at around 10:00 on January 29, 2019 (Indochina time) (White parts are cloud). (Left) The image close to what the human eye sees, (Right) Observation of polarization radiance (land only).

By analyzing the data observed by GCOM-C, the level of pollution caused by atmospheric particles can be measured quantitatively. Figure 2 shows the estimated atmospheric opacity, called “aerosol optical thickness”, at the same observation date and time as Figure 1. If the value is less than 0.1, the atmosphere is relatively transparent; if the value is close to 1.0, it is very turbid. The image shows a high value (from yellow to red) from the area around Bangkok, the capital of Thailand, to the area around Phnom Penh, the capital of Cambodia, we can see the detail distribution of atmospheric particles in over a very large area by GCOM-C.

Figure 2. The estimated opacity over the land caused by atmospheric particles at the same observation date and time as Figure 1. It is represented by a physical quantity called “aerosol optical thickness”.

The radiance data and aerosol optical thickness data introduced here are provided by JAXA’s Globe Portal System (G-Portal).

Observation images

Figures 1-2

Satellite	Global Change Observation Mission – Climate “SHIKISAI” (GCOM-C)
Sensor	Second generation GLobal Imager (SGLI)
Date	Around 10:00 on January 29, 2019 (Indochina Time)