SUPERCELL
Intensity
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When simulating the external supercell case with WRF, the most characteristic result was found to be for the intensity of the supercell. The strength of the storm was analyzed from the perspective of upward (mesocyclone), downward, and vertical wind shear.
01
W (Time series)
The graph below shows the horizontal mean value of W (vertical velocity) over time when the initial radius setting value changes. The x-axis is time and the y-axis is bottom top.
In the early stages of a supercell, a strong updraft is confirmed due to the formation of a mesocyclone, and the downdraft becomes stronger over time. Additionally, the larger the initial radius, the stronger the updraft appears at the beginning of supercell creation. The strength of the downdraft has no noticeable correlation with the initial radius.
02
W (YZ-plane)
This is a YZ plane graph of W according to the initial radius setting value. It shows the WRF modeling results of 30minute.
You can check the vertical distribution of W through the graph above. Downdrafts are visible on the left and right, centered on the strong updraft in the center of the supercell. In particular, you can check the difference in the intensity of updraft (mesocyclone) depending on the initial radius setting value. The larger the initial radius, the stronger the updraft, and unlike the time series graph, which was the horizontal mean value, the difference in the strength of the downdraft is clearly visible.
03
U,V (Standard Deviation)
vertical wind shear: It is one of the important variables that determine the strength and persistence of supercells. Since there is no vertical wind shear stress among WRF output variables, the difference between the upper and lower wind is confirmed using the standard deviation value of the wind speed vector obtained using horizontal wind (U) and medial wind (V).
The above plot is the standard deviation of the wind component for the bottom-top level at each initial radius setting value. Output time is 30min.
It can be seen that the larger the initial radius, the larger the standard deviation of the wind component near updraft area in the vertical direction. This means that the difference in wind vector between the upper and lower levels is large. This serves as evidence to support the stronger strength of the supercell.
Conclusion