A very intense Mesoscale Convective System (MCS), with induced dust, was responsible for many casualties in the Uttar Pradesh province of Northern India in early May.
22 October 2020
02 May 2018
By Ivan Smiljanic (SCISYS)
Although media reports named the event as ‘dust storms’, and satellites did identify dust in the region, the high intensity of the associated MCS were responsible for more than 100 deaths in the region.
Very rapid development of the convective system occurred around 300 km west of New Delhi, along a eastward advancing dust field front, as can be seen in the Meteosat-8 Dust RGB animation (Figure 2). Its movement was likely enhanced by the cold outflow from an older convective system in the north. Dust sources were situated further west, mostly in Pakistan and Iran.
Very peculiar cirrus outflow, that looked like splayed fingers, on top of associated MSC (Figure 1) is connected to the gravity wave field, excited by a squall line perpendicular to the system propagation.
The system intensified as it travelled to the south-east along the low level moisture boundary, throughout most of Northern India, before dissipating in the early hours of the following day, as can be seen on the Himawari-8 10.4 µm animation (Figure 3).
The strong intensity of this system is demonstrated by its size and duration, the number and variety of cloud-top features (e.g. multiple overshooting tops), and the low cloud top temperatures (exceeding -75 °C).
This was well captured by the by the visible (nominally 500 m) and high resolution infra-red (2 km) imagery from the Himawari-8 ABI instrument, see Figures 4 and 5.
Due to the fact that the event took place close to the edge of the ABI instrument scanning area, one needs to keep in mind reduced scanning resolution, but also take into account angle correction which greatly affects high-reaching clouds (parallax correction), and scattering processes in the visible spectrum — in this case strong forward scattering for AHI and weak backward scattering for SEVIRI in the local evening hours (Figure 6).
The difference in viewing angles between Meteosat-8 and Himawari-8 is obvious when directly comparing images from both on the same grid Figure 7). When viewing the features at an angle, these two satellites are seeing clouds and other features (e.g. overshooting tops) from almost opposite sides.
The zoomed-in views over New Delhi (ca. 10 km radius) (Figures 8 and 9) reveal the distorted pixel shapes from both satellites (at the same projection). Change in pixel size, from sub-satellite point, is following: for the ABI instrument from 2 x 2 km to ca. 4.95 x 7.65 km (lat/lon); for SEVIRI instrument from 3 x 3 km to ca. 4.20 x 4.25 km. For easy reference one pixel is marked in both images.
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