First Bytes
Mathematical Functions Lab
Introduction: In this lab activity you will use MatLab and write functions to to calculate various useful values and perform conversions.
This lab is available at www.cs.utexas.edu/users/scottm/FirstBytes/MathematicalFunctionsLab.htm
Write a function to carry out each of the operations explained below:
The heat index and the summer simmer index are used to measure the amount of discomfort during the summer months when heat and humidity often combine to make it feel hotter than it actually is. The heat index is usually used for afternoon high temperatures while the summer simmer index is used for overnight low temperatures. Below are the detailed equations that are used to calculate the apparent temperatures in the heat index and the summer simmer index.
Heat Index: If you know the relative humidity and the dry air temperature, then you can use the following equation to calculate the heat index.
(1) Heat index(HI), or apparent temperature(AI)= -42.379 + 2.04901523(Tf) + 10.14333127(RH) - 0.22475541(Tf)(RH) - 6.83783x10**(-3)*(Tf**(2)) - 5.481717x10**(-2)*(RH**(2)) + 1.22874x10**(-3)*(Tf**(2))*(RH) + 8.5282x10**(-4)*(Tf)*(RH**(2)) - 1.99x10**(-6)*(Tf**(2))*(RH**(2))
Note: In order for the Heat Index formula to work correctly, you must use the relative humidity in percent form. In other words, if the relative humidity is 65%, use 65 for RH in the formula, not .65.
Tf= air temperature in degrees Fahrenheit, RH= relative humidity
expressed as a whole number
You can find the temperature and relative humidity for Austin at
www.theweatherchannel.com
Zip code for Austin: 78712
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Formula used to calculate wind chill The term "wind chill" goes back to the Antarctic explorer Paul Siple, who coined it a 1939 dissertation, "Adaptation of the Explorer to the Climate of Antarctica." During the 1940s, Siple and Charles Passel conducted experiments on the time needed to freeze water in a plastic cylinder that was exposed to the elements. They found that the time depended on how warm the water was, the outside temperature and the wind speed. The formulas used to calculate wind chill were based on those experiments. In the fall of 2001, the U.S. National Weather Service and the Canadian weather replaced the formulas with new ones (one for Fahrenheit temperatures and one for Celsius readings). The new formulas are based on greater scientific knowledge and on experiments that tested how fast the faces of volunteers cooled in a wind tunnel with various combinations of wind and temperature. The new formula for winds in mph and Fahrenheit temperatures is: Wind chill temperature = 35.74 + 0.6215T - 35.75V (**0.16) + 0.4275TV(**0.16) In the formula, V is in the wind speed in statute miles per hour, and T is the temperature in degrees Fahrenheit. Note: In the formula, ** means the following term is an exponent (i.e. 10**(0.5 ) means 10 to the 0.5 power, or the square root of V), - means to subtract, + means to add. A letter next to a number means to multiply that quantity represented by the letter by the number. The standard rules of algebra apply. For reference, the old wind chill formula was: T(wc) = 0.0817(3.71V**0.5 + 5.81 -0.25V)(T - 91.4) + 91.4 Source for both formulas: The National Weather Service |