Cyclone Nivar is a tropical cyclone that brought a severe impact in the Southern part of India, especially in Tamil Nadu and Andhra Pradesh. The cyclone disturbance gradually started on November 23rd, originating in the Bay of Bengal. Low Pressure was induced in the off-coast regions of Tamil Nadu and Puducherry at the early hours of 24th November 2020. It crossed the coastal area and traveled towards North-west Tamil Nadu, entering south Andhra Pradesh on 26th November.
The heavy downpour had happened around the regions of Tamil Nadu, Karnataka, and Andhra Pradesh, causing environmental and severe socio-economic impacts to the area. Though the damage assessment can be mapped using Satellite data either using Radar or optical, the tracking of the cyclone is less likely to be captured by satellite unless there is a pass during the exact occurrence day. SatSure tried to map the cyclone trail, which was traveling from Tamil Nadu to Andhra Pradesh, in a unique manner using VIIRS — DMP Nightlight data, rainfall, and gust speed in this article.
The nightlight data of VIIRS has a daily temporal frequency and spatial resolution of 15 arc seconds. It captured the cyclone pass through cloud movement, where the eye of the cyclone is likely to be seen on frame 25–11–2020.
As reported by the Indian Meteorological Department, the severe cyclonic storm traveled with a speed of 120–130km/h, caused landfall in the coastal area of Tamil Nadu, near the Pondicherry coast.
The NIVAR cyclone, due to its depression, caused a heavy downpour, which can be observed from the map below, which shows the rainfall pattern from 23rd November to 28th November.
The trail of the cyclone can also be seen in the rainfall pattern which is passing from Tamilnadu to Andhra Pradesh.
From the above figure of rainfall pattern, it can be noticed that the rainfall started on 24th November, with an overall heavy rain shower of 42 mm in Chennai — Tamil Nadu, following Puducherry with a rainfall of 20mm.
On 25th November, the Maximum Rainfall captured is 168 mm in Puducherry, 166mm in Tamil Nadu, and around 115mm in Andhra Pradesh.
While on 26th November, Andhra Pradesh experienced a heavy shower with a maximum of 237mm while Tamil Nadu and Puducherry experienced around 160mm. The path of the cyclone is traveling from Puducherry, moving towards northwest Tamil Nadu and then entering Andhra Pradesh. It can also be observed that, due to the wind moving towards the northwest of Tamilnadu, moderate rainfall was observed in few regions of Karnataka as well.
The gust of the cyclone can be observed from the figure below along with the wind direction which is represented in an arrow.
Tropical storms occur seasonally during the month of May-June and October-December, which hit India either from the East or from the west. The damage caused by these storms is severe, and increasing each year. With the help of Remote Sensing, these damages can be mapped and post-disaster decisions on rehabilitation and recovery can be taken faster.
The below figure shows the impact areas with possible damage caused due to cyclones. This is generated based on the rainfall and gust speed.
The category is divided into 3, High Rainfall and High Gust Speed, Medium Rainfall, and Gust Speed, and similarly Low Rainfall and Wind Speed falling under High, Medium, and Low respectively.
The possible marked areas, the damages may be caused due to Landfall, Flood, or damage caused due to tree uprooting, etc. affecting Infrastructure, Agriculture, or any type of Land Use Classes.
Written by Nivedhitha Ajithkumar, former Geospatial Software Engineer, SatSure. This story was first published on our Medium