ATS620

FALL 2011

PROBLEM SET 2

Due Date: 9 September 2011

  1. (10 points) How much liquid water must evaporate from a human body (via perspiration) to lower the temperature of the person by 5°C? (Assume that the latent heat of evaporation of water is 2.5 x 106 J kg-1, and the specific heat of the human body is 4.2 x 103 J K-1 kg-1.) What percentage of the total body weight does the mass of evaporated water represent?
  1. (10 points) Twenty liters of air at 20°C and a relative humidity of 60% are compressed isothermally to a volume of 4 liters. Calculate the mass of water condensed. The saturation vapor pressure of water at 20°C is 23 hPa. (Density of air at 0°C and 1000 hPa is 1.28 kg m-3.)
  1. (10 points) One kilogram of ice at 0°C is placed in an isolated container with 1 kg of water at 10°C and 1 atm.

a) How much of the ice melts?

b) What change is there in the entropy of the universe due to the melting of the ice?

  1. (20 points) Download the IDL programs (skewt.pro and hw2.pro) and the text files (joplin18z.txt and joplin00z.txt). The text files contain radiosonde data from Springfield, MO (near Joplin, MO) during the afternoon of the notorious Joplin, MO EF5 tornado. The IDL program (hw2.pro) will plot each sounding on a Skew-T log p diagram (using skewt.pro). Plot and print out the 18Z sounding then draw/indicate the following:

a)The LCL, LFC, and EL for a surface parcel

b)Neutrally unstable, conditionally unstable, and absolutely stable

c)Areas of CINH, CAPE for a surface parcel

For the 18Z thermodynamic environment, would you expect a surface parcel to reach its LFC? How about for a surface parcel containing a dew point of 23C? Explain from an energy perspective.