Typhoons cause atmospheric pressure to drop.

VOA: special.2009.07.07

We're going to drop the pressure, the volume is going to go up.

我们会降低压强，体积就会变大。

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In addition,the U.S.Air Force conducted its first airdrop of supplies on Monday, north of Port-au-Prince, using an aircraft that flew from the United States and returned there after the drop, easing pressure on the Port-au-Prince airport.

VOA: standard.2010.01.19