Relative high humidity.
The basic explanation is that (contrary to what might seem intuitive)
humid air is less dense than dry air, so there is less drag. In other
words, humid air is thinner, so it slows the ball down less. The
difference is slight, but it could make a few yards difference on a
long drive.
Follow the links below to find more detailed explanations:
The Flight of a Golf Ball
"The molecular weight of water is about 18 grams per mole; that of dry
air (including nitrogen, oxygen, carbon dioxide, and other trace
gases) is about 29 grams per mole. Thus, if we increase the proportion
of water vapor molecules in the air mixture while keeping temperature
and pressure constant, we lower the density. But not by much. At a
temperature of 95 degrees F (35 degrees C) and a standard sea-level
pressure of 29.92 inches of mercury (1013 mb), the air density is
1.1447 kg per cubic meter (0.0715 lb/ft-3) when the relative humidity
is 5 percent, and 1.1310 kg m-3 (0.0706 lb ft-3) when the relative
humidity is 60 percent, a decrease of only 1.2 percent. Thus, one
could expect to drive a golf ball only a few yards farther on a very
humid, hot summer day than on a very dry, hot summer day. With the
effect of backspin added, the gain is even less, perhaps only half as
much."
http://www.weatherwise.org/qr/qry.golfball.html
How Weather Affects Baseball
"Air with high humidity is less dense, or thinner, than dry
air. But this effect so slight it would only account for a long ball
traveling a few inches farther on a humid day."
http://www.sportsweatherpage.com/baseball_weather.htm
Humidity and air density
"Most people who haven't studied physics or chemistry find it hard to
believe that humid air is lighter, or less dense, than dry air. How
can the air become lighter if we add water vapor to it?
"Scientists have known this for a long time. The first was Isaac
Newton, who stated that humid air is less dense than dry air in 1717
in his book, Optics. But, other scientists didn't generally understand
this until later in that century. ...
"Wait a minute, you might say, 'I know water's heavier than air.'
True, liquid water is heavier, or more dense, than air. But, the water
that makes the air humid isn't liquid. It's water vapor, which is a
gas that is lighter than nitrogen or oxygen.
"Compared to the differences made by temperature and air pressure,
humidity has a small effect on the air's density. But, humid air is
lighter than dry air at the same temperature and pressure."
http://www.usatoday.com/weather/wdensity.htm
Finally, although it doesn't directly answer your question, you may be
interested in the following document. It tells you more than you'd
ever want to know about the factors that affect the flight of golf
balls.
The Science of Golf Balls
http://www.bs-sports.co.jp/english/science_of_golf_ball/the_science_of_golf_balls.pdf
I hope this satisfies your curiosity.
Best wishes,
mvguy-ga
Google search terms:
"air resistance" humidity
://www.google.com/search?q=%22air+resistance%22+humidity&sourceid=opera&num=25&ie=utf-8&oe=utf-8 |
