Comments on: Half a Degree May Double Hurricane Intensity http://www.sciscoop.com/2005-8-1-165248-1059.html Scooping up science news and dropping it on your desk Thu, 18 Mar 2010 16:03:57 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: SEWilco http://www.sciscoop.com/2005-8-1-165248-1059.html/comment-page-1#comment-2525 SEWilco Wed, 03 Aug 2005 11:04:11 +0000 http://localhost/~arielschwartz/wordpress/sciscoop/?p=2626#comment-2525 Notice the "50 year" limit. In 1975, 30 years ago, the 1945-1975 global cooling period ended and warming began. Behavior of hurricanes may have been different during that time. There was a period of warming from about 1850-1945; how did hurricanes behave then? Notice the “50 year” limit.
In 1975, 30 years ago, the 1945-1975 global cooling period ended and warming began. Behavior of hurricanes may have been different during that time. There was a period of warming from about 1850-1945; how did hurricanes behave then?

]]> By: chad http://www.sciscoop.com/2005-8-1-165248-1059.html/comment-page-1#comment-1554 chad Tue, 02 Aug 2005 08:06:35 +0000 http://localhost/~arielschwartz/wordpress/sciscoop/?p=2626#comment-1554 <p>This is not as bad as it sounds, and I'm going to dissect the phrase, "integrated square," to show what I mean.</p> <p>Let's start with "square." Whenever you hear the words "energy" or "power," immediate start thinking about exponents, and especially powers of two. The common measurement of power, the <a href="http://en.wikipedia.org/wiki/Decibel">decibel</a>, is a way of linearizing exponents, where every 3 decibels approximately corresponds to a doubling. So 30 decibels is (approximately) equivalent to multiplying by 1000. (Decibels are unitless, however there are some versions that are anchored to a specific value at 0dB. You may be most familiar with the audio version, dBA, which is typically shortened just to "decibels" and should not be confused with this conversation.)</p> <p>Anyway, back to the discussion. So in the topic, we are dealing with the square of the wind speed. A small change in wind speed will create a larger change in the square of the wind speed, especially when the wind speed is high, like it is in hurricanes. After doing some sample math with actual numbers, however, I realized that a few percentage points of wind speed change, say 2%, will only change the square by about 4%. So this is not the primary source of the doubling.</p> <p>Most of the doubling, therefore, must come from the other part of the original phrase: "integrated." Think of the "integrated square" as a (curvy) rectangle, with the square of the wind speed as the height and time as the width. The area of the square is the "destructive potential" of the hurricane, as mentioned in the topic. This width is the "integrated" part, and it is how long the winds last. The increase in temperature prolongs the duration of the winds. The increase in temperature, therefore, makes the rectangle wider, and this is where we get most of the increase in the "destructive potential" of the hurricane.</p> <p>The New Scientist equates destructive potential with intensity. I think this is a bit of a misnomer. I believe most people consider intensity to be synonymous with wind speed. So I return to my original statement, which is, this isn't nearly as bad as it sounds. I do, however, agree that sustaining high wind speeds for a longer period, especially as the hurricane continues to move inland, would definitely increase its destructiveness. It would be nice to have some actual figures on how much longer the winds are sustained.</p> This is not as bad as it sounds, and I’m going to dissect the phrase, “integrated square,” to show what I mean.

Let’s start with “square.” Whenever you hear the words “energy” or “power,” immediate start thinking about exponents, and especially powers of two. The common measurement of power, the decibel, is a way of linearizing exponents, where every 3 decibels approximately corresponds to a doubling. So 30 decibels is (approximately) equivalent to multiplying by 1000. (Decibels are unitless, however there are some versions that are anchored to a specific value at 0dB. You may be most familiar with the audio version, dBA, which is typically shortened just to “decibels” and should not be confused with this conversation.)

Anyway, back to the discussion. So in the topic, we are dealing with the square of the wind speed. A small change in wind speed will create a larger change in the square of the wind speed, especially when the wind speed is high, like it is in hurricanes. After doing some sample math with actual numbers, however, I realized that a few percentage points of wind speed change, say 2%, will only change the square by about 4%. So this is not the primary source of the doubling.

Most of the doubling, therefore, must come from the other part of the original phrase: “integrated.” Think of the “integrated square” as a (curvy) rectangle, with the square of the wind speed as the height and time as the width. The area of the square is the “destructive potential” of the hurricane, as mentioned in the topic. This width is the “integrated” part, and it is how long the winds last. The increase in temperature prolongs the duration of the winds. The increase in temperature, therefore, makes the rectangle wider, and this is where we get most of the increase in the “destructive potential” of the hurricane.

The New Scientist equates destructive potential with intensity. I think this is a bit of a misnomer. I believe most people consider intensity to be synonymous with wind speed. So I return to my original statement, which is, this isn’t nearly as bad as it sounds. I do, however, agree that sustaining high wind speeds for a longer period, especially as the hurricane continues to move inland, would definitely increase its destructiveness. It would be nice to have some actual figures on how much longer the winds are sustained.

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