Saturday, August 11, 2007

Estimating the number of Atlantic storms before the satellite era

UPI: A U.S. study using pre-satellite records suggests the number of Atlantic hurricane tracks might have changed just slightly during recent decades. Edmund Chang and Yanjuan Guo of the Institute for Terrestrial and Planetary Atmospheres at Stony Brook University say the number of such hurricanes is difficult to determine because hurricanes likely went undetected before satellite observations were available.

To estimate the occurrence of such undetected hurricanes, Chang and Guo examined ship track records before and during the satellite era. They mapped satellite-derived cyclone tracks from 1976 to 2005 against ship tracks from the same time period to determine the probability that ships recorded wind speeds high enough to detect a tropical cyclone.

Then, they computed the probability that ships sailing between 1900 and 1965 would have made observations of similar high wind speeds, if tropical cyclones from the satellite era had been present at the same rate during earlier years. From that data they determined the number of tropical cyclones not making landfall over any continent or island likely was underestimated by 1 or less per year after World War I.

The study appears in Geophysical Research Letters.

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