Geometry Energy Index
St George's School
Floor Location : M 029 N
Geometry Energy Index (GEI) is an system to estimate tropical cyclone intensity (which includes tropical depression, tropical storm, and typhoon/hurricane) based on the graphed functional relationship among multiple features of a cyclone. The features used in calculating are wind speed based on Joint Typhoon Warning Centre (JTWC), eye centre temperature and cloud temperature based on Cooperative Institute for Meteorological Satellite Studies (CIMSS), circulation radius based on JTWC and China Meteorological Administration (CMA), and Dvorak Technique value from CIMSS.
Since this is an innovation, it’s a hybrid version based on Dvorak technique and infrared satellite image. Compared to the existing analytical technique used by JTWC, CMA, and Japan Meteorology Agency (JMA), GEI is an analytical index rather than an operational index. The existing tropical cyclone estimating system used by official agencies is based on estimated wind speed and mostly ignored the inner relationship between a cyclone’s intensity and size, which affects the total energy of the cyclone. This hybrid system can avoid the subjective view of weighing wind speed more.
First, I put the four features of a cyclone into a function graph. The result after calculation will be in a scale from 0-100. The higher a cyclone’s score is, the more energy the cyclone has. By experimenting on 33 different tropical cyclones throughout 2015-2016, GEI has been updated and perfected. Data from the analyze of the 33 cyclones all show that the index doesn’t have a huge difference from the existing official analyzation. All data show an inverse proportion relationship with the air pressure data, another aspect of cyclone. The inverse proportion indicates GEI is scientifically usable. The minor difference with the existing analyzation is created by the features of the cyclone other than wind speed, which analyzes a more precise energy index of the cyclone to avoid the cost of underestimation in a cyclone landfall.
In the results of analyzing cyclones by GEI, Hurricane Matthew, Typhoon Meranti, and Typhoon Songda provide a lucid example. Although the peak intensity of Hurricane Matthew is Category-5 with high wind speed (140kts), it's not large (radius≈350 km). Therefore, its score (GEI=61.69) is not as high as Meranti’s (GEI=80.19), another Category-5 at its 140kts intensity. However, Matthew expanded when it approached Florida (radius≈500 km). At that time, although Matthew’s strength decreased to Category-1 (75kts), its score (GEI=26.37) was higher than Songda’s (GEI=19.89, 75kts, radius≈400 km) because of Matthew's huge size.
By using GEI, we can have a more accurate analyze of tropical cyclones and a better way to defend us against them.