Automatic Tracking and Characterization of Cumulonimbus Clouds from FY-2C Geostationary Meteorological Satellite Images

Table 2

Cloud characteristics derived from geostationary imagery.

Type	Features	Number	Characters	Equation^#	This study	Hong et al., [48]*	Arnaud et al., [12]**	Machado et al., [29]***	Xu et al., [49]****
Pixel features	Coldness features	1	Top brightness temperature of Cb pixel (TB)		✓
		2	Gradient of pixel TB (GT)		✓
		3	Difference of pixel TB over split window channels (SWDT)		✓
		4	Difference of TB between one IR and WV channel (DIWT)		✓
	Time evolution features	5	Change in pixel cloud type (CPT)		✓
		6	Change ratio of pixel TB (CTB)		✓
	Situation features	7	Deviation to convective cloud center (DCCC)		✓
Cloud patch features	Coldness features	8	Minimum TB of a cloud patch (PD)		✓	✓		✓
		9	Mean TB of a cloud patch (PD)		✓	✓		✓
		10	Difference in TB over split windows for a Cb patch (DSWT)		✓
		11	Difference in TB over IR and WV windows for a Cb patch (DIWT)		✓
	Geometric features	12	Clouds patch area ()	resolution	✓	✓	✓	✓	✓
		13	Perimeter (PERI)	PERI = resolution	✓	✓		✓	✓
		14	Geometric center (, )	,	✓				✓
		15	Gravitational center (, )	,	✓			✓	✓
		16	Shape index of geometric momentum (SIGM)	,	✓		✓
		17	Shape index of the perimeter (SIP)		✓
		18	Eccentricity (ECCT)		✓	✓		✓	✓
	Texture features	19	Boundary steepness (BS)		✓
		20	Standard deviation of the TB of a cloud patch (STD)		✓	✓			✓
		21	Gradient of cloud TB (TOPG)		✓	✓			✓
	Dynamical features	22	Life stage of a cloud patch (L)		✓			✓
		23	Horizontal moving speed of a Cb patch (HMSP)		✓			✓
		24	Horizontal moving direction of a cloud patch (HMDP)		✓			✓
		25	Cloud growth rate (CGR)		✓
		26	Vertical moving character of a Cb patch (VMCP)		✓

TB₁, TB₂, and TB_WV are the brightness temperature (TB) of three infrared (IR) channels (IR1, 10.3–11.3 m; IR2, 11.5–2.5 m; and WV 6.3–7.6 μm), respectively; is the cloud type on the current () image, and is the corresponding cloud type on the previous () image; is typically 1 hour. () is the center of Cb patch. The center of the Cb patch can be the geometric center () or the gravitational center (); is the number of pixels in a Cb patch; is the number of pixels on the boundary of a Cb patch; is the geometric momentum of a cloud patch, and is the geometric momentum of a round patch with the same size; PERI is the perimeter of a cloud patch, and PERI₀ is the perimeter of a round patch with the same area; is the distance between the focus and the center of cloud patch, and is the length of the long axis; is the distance from pixel on the Cb cloud patch boundary to the corresponding position on the warmer cloud patch boundary; is the distance from pixel on the boundary to the shooting top (PD).
*Hong et al. [48] extracted the following additional parameters: compactness, mean value of local standard deviation of cloud patch (MSTDS), and gray images' texture (angular second moment, contrast, entropy, etc.).
**Arnaud et al. [12] extracted the following additional parameters: maximum length, maximum width, volume index, position of the front edge, and angle between the principal axis of the cloud and the -axis.
***Machado et al., [29] extracted the following additional parameters: area overlap fraction with possible antecedent, average (weighted) difference of all parameters. The dynamical features refer to the MCSs over America.
****Xu et al. [49] extracted the following additional parameters: maximum temperature difference from IR threshold, mean temperature difference from IR threshold, and maximum entropy.