Yearly tropical cyclone potential impact index in China

A new composite index called the yearly tropical cyclone potential impact(YTCPI) is introduced. The relationship between YTCPI and activities of tropical cyclones(TCs) in China, disaster loss, and main ambient fields are investigated to show the potential of YTCPI as a new tool for short-term climate prediction of TCs. YTCPI can indicate TC activity and potential disaster loss. As correlation coefficients between YTCPI and frequency of landfalling TCs, the frequency of TCs traversing or forming inside a 24 h warning line in China from 1971 to 2010 are 0.58 and 0.56, respectively(both are at a statistically significant level, above α = 0.001). Furthermore, three simple indexes are used to compare with YTCPI. They all have very close relationships with it, with correlation coefficients 0.75, 0.82 and 0.78. For economic loss and YTCPI, the correlation coefficient is 0.57 for 1994–2009. Information on principal ambient fields(sea surface temperature, 850 and 500 hPa geopotential heights) during the previous winter is reflected in the relationship with YTCPI. Spatial and temporal variabilities of ambient fields are extracted through empirical orthogonal function(EOF) analysis. Spatial distributions of correlation coefficient between YTCPI and ambient fields match the EOF main mode. Correlation coefficients between YTCPI and the EOF time array for the three ambient fields are 0.46, 0.44 and 0.4, respectively, all statistically significant, above α = 0.01. The YTCPI has the overall potential to be an improved prediction tool.