Comment on "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment"

doi:10.1126/science.1121522

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Technical Comments

Comment on "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment"

Johnny C. L. Chan

Laboratory for Atmospheric Research, Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.

Fig. 1. Annual variations of the potential destruction index (PDI), the number of category 4 and 5 typhoons according to the Saffir-Simpson scale (NCAT45), and the SST anomalies within the area 5° to 30°N, 120° to 180°E averaged between May and November (SSTA). All series are standardized (deviation of the raw value from the mean over the entire period was calculated and then divided by the standard deviation). [View Larger Version of this Image (26K GIF file)]

Fig. 2. Annual variations of the principal component coefficients of various parameters of the atmospheric environment. VORT, rotational flow at around 1.5 km from the sea surface; SHEAR, vertical wind shear of the east-west flow between 12 and 1.5 km, and MSE, moist static energy in the lower troposphere. All series are standardized (i.e., deviation of the raw value from the mean over the entire period was calculated and then divided by the standard deviation) values averaged between May and November each year. The time series of PDI from Fig. 1 is also reproduced for comparison. [View Larger Version of this Image (28K GIF file)]