Dust storms are one of the climatological phenomena. These events are important because they represent a massive amount of erosion and leave a considerable amount of deposition. Dust storms usually transport silt-sized material from the world’s deserts to distant places, thousands of kilometres away. The wind is responsible for lifting the dust particles from the ground and moving them from one place to another.
Dust storms are defined as those having visibility of less than 1 kilometre. A low-intensity dust storm is called blowing dust with visibility of fewer than 11 kilometres.
(Creative Commons Attribution-Share Alike 4.0 International license)
Why worry about dust storms?
The phenomenon of dust storms has many environmental consequences. It also concerns the physical and economic well-being of humans. Suspended dust particles cause health implications. Dust storms are thus a natural disaster. They pose a challenge to sustainable development.
What do we need to understand about dust storms?
There are broadly three areas of research concerning dust storms:
1. Source: Identification of the source areas of dust storms
2. Space: Studying the spatial distribution (extent) of dust storms
3. Time: Studying the varying patterns of dust storms over time
Research into these needs regional to global scale studies, which is often not attainable through ground-based in-situ measuring stations; instead, a synoptic view (remote sensing) is required, which is offered by satellite-platformed sensors.
Are dust storms visible from satellite-based images?
Sensors onboard satellite platforms can sense electromagnetic radiations not only in the visible range of the spectrum but also in the infrared and microwave ranges. Hence, one can get information far beyond what human eyes can see through satellite-based images. Sand particles have a characteristic spectral signature which helps to distinguish them from the background signatures such as that emerging from vegetation and waterbodies. However, it may become challenging to determine a dust storm from a background of sand-related ground features or from the surrounding clouds.
How do we distinguish between a dust storm and clouds from satellite data?
For this, scientists have been relying upon the brightness temperature property observed in the electromagnetic spectrum’s thermal infrared region. While dust storms absorb infrared radiations at 10.8 μm, water droplets in a cloud absorb infrared radiations at 12 μm. Hence, the brightness temperature difference values between two thermal infrared channels (channels at 11 and 12 μm) are helpful. A negative difference value indicates the presence of a dust load.
Recent study
In a recent geospatial study, scientists from the Indian Space Research Organisation (ISRO) and the Indian Council of Agricultural Research (ICAR) have shown their enhanced capability to assess dust load using satellite-based images.
Data from two types of satellites have been used for the research mentioned above:
1. Geostationary satellite (INSAT-3D)
2. Polar satellite (Moderate Resolution Imaging Spectroradiometer, MODIS)
A dust detection algorithm was developed that was based on dust indices.
Challenges and way forward
The study cited here was carried out in the Thar desert. Further, the thresholds defined in the study primarily affect the area under the dust storm. The findings from this study would help in the development of an early warning system for dust storms. Also, such studies will aid in studying dust storm dynamics.
References
Paper in focus:
Other references:
Goudie, A.S., 1983. Dust storms in space and time. Progress in Physical Geography, 7(4), pp.502-530.
