Details

1. Has everyone purchase a copy of the notes?
2. Reading for Thursday;
• Section 1.1 - Basic Concepts (Radiance vs. Irradiance),
• Section 1.3 - Line Shapes
• Section 1.4 - Radiatively Active Gases in the Atmosphere
3. Revised office hours for Walden, Thurs. 12:30 - 1:30pm
4. Pay close attention to the Matlab commands used in the first few labs.  We will build upon these throughout the course.

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• EM spectrum.  We are interested in solar (ultraviolet and visible) and infrared radiation.

 
• Why?  Because these spectral regions dominate the energy balance of Earth.

 
• Langley plots can be used to determine the amount of solar radiation incident at the top of the atmosphere.

 
• The increase of atmospheric carbon dioxide since 1957 is a direct result of industrialization.  Greenhouse gases, such as carbon dioxide, absorb and trap infrared radiation emitted by Earth.

 
• The Sun puts out an enormous amount of radiation, similar to a blackbody at about 6000 K.  The Earth, on the other hand, emits (or gives off) radiation as if it were a blackbody at about 300 K.  Conservation of energy says that if the Earth's temperature on average is constant, then the amount of energy Earth receives from the Sun must be equal to the amount of energy Earth gives off to space.  Planck's function tells us how much radiation is given off by a blackbody, a perfect emitter and absorber, at a given temperature.  This function is the topic of Lab 2.

 


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1. Make sure you hand in a lab report that is organized and legible.
2. When we ask you to "record" values, this means write them down in your report.  It is very important to always include the correct units with all values in your report.
3. Hand in all figures that are created in the lab as part of your report.  Figures should always have x- and y-axes labels, as well as a title.  If data has come from an external source (like the CO2 data), make sure you reference where you got it from.

Scripts versus Functions in Matlab
 

• A Matlab script file is a text (ASCII) file containing Matlab commands.  Here is an example script that generates the plot of atmospheric carbon dioxide from 1957 to 1996.

Here is what the Matlab command, 'help script', tell us:

» help script

 SCRIPT About MATLAB scripts and M-files.
    A  SCRIPT file is an external file that contains a sequence
    of MATLAB statements.  By typing the filename, subsequent
    MATLAB input is obtained from the file.  SCRIPT files have
    a filename extension of ".m" and are often called "M-files".
    To make a SCRIPT file into a function, see FUNCTION.
 
    See also TYPE, ECHO.
 
 
 

• A Matlab function is also a text file, but it has the ability to pass input values from Matlab to itself and to return output values to the Matlab workspace.  Actually, you have already used many Matlab functions already; plot, axis, xlabel, ylabel, title, length, reshape, find, ...   Functions are commonly used when you want to repeat a given operation.  There are also useful for organizing your data analysis, so that your scripts are reasonably short and readable.  In Lab 2, you will use two functions, written by Dr. Walden, for calculating the Planck function (planck_wv.m and planck_wn.m).

Here is what 'help function' tell us:

» help function

 FUNCTION Add new function.
    New functions may be added to MATLAB's vocabulary if they
    are expressed in terms of other existing functions. The
    commands and functions that comprise the new function must
    be put in a file whose name defines the name of the new
    function, with a filename extension of '.m'. At the top of
    the file must be a line that contains the syntax definition
    for the new function. For example, the existence of a file
    on disk called STAT.M with:
 
            function [mean,stdev] = stat(x)
            n = length(x);
            mean = sum(x) / n;
            stdev = sqrt(sum((x - mean).^2)/n);
 
    defines a new function called STAT that calculates the
    mean and standard deviation of a vector. The variables
    within the body of the function are all local variables.
    See SCRIPT for procedures that work globally on the work-
    space.
 
    A subfunction that is visible to the other functions in the
    same file is created by defining a new function with the FUNCTION
    keyword after the body of the preceeding function or subfunction.
    For example, avg is a subfunction within the file STAT.M:
 
           function [mean,stdev] = stat(x)
           n = length(x);
           mean = avg(x,n);
           stdev = sqrt(sum((x-avg(x,n)).^2)/n);
 
           function mean = avg(x,n)
           mean = sum(x)/n;
 
    Subfunctions are not visible outside the file where they are defined.
    Normally functions return when the end of the function is reached.
    A RETURN statement can be used to force an early return.
 
    See also SCRIPT, RETURN, VARARGIN, VARARGOUT, NARGIN, NARGOUT, INPUTNAME.