Convective storm with two above-anvil ice plumes

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AVHRR and SEVIRI products confirm that two above-anvil ice plumes consisted of small ice crystals.

Date & Time
21 June 2016 07:40 UTC and 08:25 UTC
Satellites
Metop-A and B, Meteosat-10
Instruments
SEVIRI, AVHRR
Channels/Products
Infrared, Visible, Day Microphysics RGB, Cloud RGB, Severe Convection RGB, Sandwich Product
 
 

By Mária Putsay (Hungarian Meteorological Service)

The convective system shown in Figures 1 and 2 was observed over Russia (north-east of Belarus, close to city of Velikiye Luki) on 21 June, at 07:40 UTC by the Metop-B AVHRR instrument and at 08:25 UTC by Metop-A AVHRR.

According to reports from the European Severe Weather Database (ESWD) it caused large hail and severe winds.

Figure 1: Metop-B, 21 June 2016, 07:40 UTC
AVHRR
Day Microphysics RGB (left panel) and Cloud RGB (right panel)
Full Resolution
Figure 2: Metop-A, 21 June 2016, 08:25 UTC
AVHRR
Day Microphysics RGB (left panel) and Cloud RGB (right panel)
Full Resolution

The two-panel images in Figures 1 and 2 are the AVHRR Day Microphysics (left) and Cloud RGB (right). Note the highly extended, divergent, high-level cirrus shield.

The AVHRR Cloud RGB images are created with the VIS0.63, NIR0.87 and IR10.8 channels. AVHRR Day Microphysics RGB images are created with the NIR0.87, NIR1.61 and IR10.8 channels. The SEVIRI Day Microphysics RGB images are created with the VIS0.8, the reflected part of the IR3.9 and IR10.8 channels.

On the top of the north-western cell two over-anvil ice-plumes can be observed. In the Cloud RGB image the ice plumes can be seen due to the shadows cast on the anvil, and due to their different appearance compared to the anvil.

In the Day Microphysics RGB the colour tones of the ice plumes and the anvil are different: orange against red-orange. The higher NIR1.6 reflectivity values of the ice plumes result in a stronger green signal.

Figure 3: Metop-A, 21 June 2016, 08:25 UTC
AVHRR
Day Microphysics RGB (left panel) and Cloud RGB (right panel)
Figure 4: Metop-B, 21 June 2016, 08:25 UTC
AVHRR
Sandwich product

The ice plumes seem to consist of smaller ice crystals. The Metop images from 08:25 UTC (Figures 3 and 4) give a closer look at this storm top.

Figure 5
 
Figure 5: Metop-A AVHRR VIS0.63 (upper left), AVHRR Day Microphysics RGB (upper middle), Meteosat SEVIRI Day Microphysics RGB (upper right), AVHRR sandwich product (bottom left), AVHRR IR10.8 image (bottom middle) & Meteosat Severe Convection RGB (bottom right), 21 June 08:25 UTC
Full Resolution

In Figure 5, Metop AVHRR and Meteosat SEVIRI images are shown together, the SEVIRI Day Microphysics and Severe Convection RGB images are also visualised. Note the dislocation of the clouds of AVHRR and SEVIRI images due to the parallax shift.

In the SEVIRI Day Microphysics RGB image the presence of the two ice plumes is not eye-catching due to less spatial resolution.

However, the two yellow bands on the SEVIRI Severe Convection RGB image indicate the ice plumes are present.

The yellow colour in this RGB indicates small cloud top particles and/or a very cold cloud top. But, in this case, it could not be caused only by the low cloud top temperature, as the Severe Convection RGB is less yellow for more cold areas.

See Figure 5 and 6 comparing the brightness temperature of IR10.8 image and the yellow colours in the Severe Convection RGB.

So, both the AVHRR Day Microphysics and the SEVIRI Severe Storm RGB images confirm that these ice plumes consisted of small ice crystals.

Figure 6
 
Figure 6: Metop-A AVHRR Day Microphysics RGB (left), IR10.8 image (middle) & Meteosat SEVIRI Severe Convection RGB (right), 21 June 08:25 UTC
Full Resolution
 
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