Hot and wet: 2009 summer of extremes

By Ni Yinbin and Yan Zhen  |   2009-9-3  |     NEWSPAPER EDITION

IT will probably come as no surprise to long-time Shanghai residents that the summer of 2009 has been an unusual one.
Now it's official: The Shanghai Meteorological Bureau said yesterday that there were twice as many scorching days this summer than normal and more rain. It was also a season with two distinct personalities: hot and relatively dry early and wet and milder later on.
"This summer was not normal," said Shen Yu, senior engineer with the bureau.
Since the first heat wave in May, the city recorded 18 days with temperatures exceeding 35 degrees Celsius, compared with an average of nine days in recent years.
The mercury hit 40 degrees Celsius on July 20, the hottest day this year and only 0.3 degrees shy of a 137-year record. The bureau also reported that the average daily high this summer reached 27.9 degrees, 1.4 degrees higher than the historical average.
Wild swings
Extreme weather continued as the heat wave moderated into a string of seemingly endless rainy days.
Although precipitation during the traditional Plum Rain season around mid-June was 30 percent lower than average, summer rainfall overall soared 35 percent above normal, hitting 685 millimeters.
The peak occurred in July and August, when thunderstorms blown in by the powerful typhoon "Marakot" hovered near the city. Rainfall in the past two months was 60 percent to 70 percent higher than in the same period in previous years.
Shen explained that the long rain spell was due to a zigzagging cold front.
"It went southwest and after some days changed direction to the northeast," Shen said. "It was rare, but we can also find some similar summers in the past."
More pleasant days are ahead, the bureau said. Rainfall this autumn is expected to be about one-third of the summer's level, according to the bureau.
There should be fewer than 27 rainy days this fall, and the average temperature will be 18 to 19 degrees Celsius, which is about normal.
The bureau also said the first frost should occur in the second half of November.
Fall will be declared when the average temperature drops below 22 degrees Celsius for five consecutive days.