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 Physical Climatology: Field Methods

GEOG 5231/4231 - Fall 2001

Professor Konrad Steffen
CIRES Ekeley Building, S264
Tel o: 492 4524; h: 494 6276
e-mail koni@seaice.colorado.edu


Lab III

Objectives 

  • Relative calibration of temperature, humidity and wind profile instruments
  • Calculation of sensible and latent heat fluxes based on bulk method

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    Relative Calibration of temperature, humidity and wind sensors
    same procedure than Lab II

    Latent and Sensible Heat Flux

    1.  Describe the instrumentation used for turbulent energy flux measurements (sensible, latent heat fluxes) based on the gradient method. Discuss and describe the other instruments used for the energy balance measurements at Mammoth Gulch. 

    2.  What is the Richardson Number and why do we use a stability function to correct convective fluxes?

    3.  Profile measurements for a day and night situations are given in the following table. Analyze both cases in preparation for the Mammoth Gulch flux data analysis.

    a)  Calculate the Richardson Number..

    b)  Plot the temperature and wind profile on semi logarithmic paper; e.g., log(z) versus T and V.

    c)  Derive the roughness length for both data sets (use plot of log(z) versus V)

    d)  Discuss the two profiles in the context of the atmospheric stability.

    e)  Derive the radiation balance and the albedo from the two date sets. 

    f)  Calculate the sensible and latent heat flux for both data sets and use the stability function if needed.
        To derive the vapor pressure from the measured relative humidity use the following approximation:

                  Relative Humidity = 100 (e/es)
                  Vapor density  r = 2.17 e / T;  e[Pa], T[K]
                  e = vapor pressure
                  es = saturation vapor pressure
                 Link to Saturation vapor tables
                  P = pressure
                 Ca : heat capacity of the air = 0.0012 106 J m-3 K-1
                  Lv : latent heat of vaporization = 2.52 106 J kg-1
                  X: factor stable condition = (1-5 Ri)2
                  X: factor unstable condition = (1-16 Ri)3/4

                 QH=[-Cak2(Du DT)/(ln(z2/z1))2] X

                 QE=[-Lvk2(Du D r)/(ln(z2/z1))2] X
     

    g) Derive the ground heat flux as residual of the above calculated energy balance.

    JD_time 
    Net R. 
    S(refl) 
    S(in) 
    V1
    V2 
    V3 
      T1 
      T2 
      T3 
    H1 
    H2 
    H3 
    P
    Time 
    W m-2
    W m-2
    W m-2
    ms-1
    ms-1
    ms-1
    C 
    C 
    C 
    % 
    % 
    % 
    mb
    303.5521 
    36.35 
    199.08 
    273.81
    .97
    1.43
    1.65
    -7.7
    -8.0
    -8.3
    76.0
    82.6
    87.7
    835.7 
    306.8542
    -58.67
    .00
    .00
    .88
    1.11
    1.35
    -13.0
    -12.2
    -11.7
    68.9
     67.5
    65.7
    836.3 

    Instruments heights: Level 1= 0.2 m; level 2 = 0.6 m; level 3 = 1.3 m
    V: wind speed H: relative humidity  P: pressure 
    Net R: net radiation S(refl).: short-wave reflected radiation S(in): short-wave incoming radiation
     

    General reading: 
    Book: An Introduction to Boundary Layer Meteorology (Roland B. Stull) 

  • The Richardson Number, p. 175-180.
  • Boundary Conditions and Surface Forcings, p. 251-294.

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    Lab Report III is due on November 21, 2001 (before Thanksgiving)