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Selecting Data Variables |
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Selecting Data Variables |
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At this point, you should feel comfortable with the many ways to select data for specific locations. Let us now look at the ways of selecting data variables. These techniques are independent of the data type and we therefore use just one of the datasets to illustrate them.
Note: When using station data, it is often best to select your desired station(s) before selecting a data variable.
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1. Selecting a single variable |
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2. Selecting more than one variable |
Start at the GLOBALSOD dataset main page*.
Example: Select the maximum wind gust variable from the GLOBALSOD dataset.
Method 1: Dataset and Variables Links
Select the "maximum" link under the Datasets and
variables heading.
Select the "gust" link under the Datasets and variables heading.
Select the "Wind Speed" link under the Datasets and variables heading.
CHECK
Method 2: Data Selection Link
Go back to the GLOBALSOD dataset main page.
Select the "Data Selection" link in the function bar.
CHECK
Select the "maximum gust Wind Speed" link from the list
of variables.
You are now at the data selection page. At this point you have the option
to select a specific time period and this is discussed in more detail in the
next section.
Right now let's continue with the techniques to select data variables.
Select the "Stop Selecting" button in the Data Selection box.
CHECK
This brings us to the same results found by Method 1.
Method 3: Expert Mode
Go back to the GLOBALSOD dataset main page.
Select the "Expert Mode" link in the function bar.
In the text box at the top of the page, enter the following line below the text
already there.
.maximum .gust .wspeed
Click "OK". CHECK
Again, this offers us the same results found by the previous
two methods.
You can use expert mode to select a data variable in this manner any time you know the variable is identified in the dataset. Note that this information is given under the Datasets and variables heading. Simply see how a variable is defined, add appropriate "."s as in this example and put it in expert mode.
This technique is typically used for comparing two different data strings arithmetically or visually. These operations are covered in more detail in Part III. The following example illustrates the selection procedure only.
Knowledge of the location of a dataset is important in this technique. As you continue to use the Data Library, you will become familiar with the directory structure of the datasets that you use most often. We will work through this example under the assumption that you are not very familiar with the location of the dataset in the SOURCES directory tree. Remember we noted that the source bar is your key to knowing where you are in the data library? We will use to our advantage here.
Let's use the Reyn_Smith dataset this time. As always, start on the dataset's main page*.
Example: Select the monthly climatological SST and monthly observed SST data variable from the Reyn_Smith dataset.
Use the links under the Datasets and variables heading to select
the climatological SST variable.
CHECK
Write down the directory structure indicated in the source bar.
(Note that the structure actually begins with "SOURCES", but it is not seen due to a lack
of room in the bar.)
Go back to the dataset main page.
Use the links under the Datasets and variables heading to select the monthly SST variable.
CHECK
Enter expert mode.
Note the similarity between the directory structure in the source bar
and the text in the text box. You can refer to any dataset or variable in expert mode in
this way. Simply take the location of the dataset/variable as indicated by the source
bar and add "." at the beginning of each directory level. We will use the directory structure
information you just wrote down to add the climatological SST variable here.
Enter the following line in the text box below the text that is already
there. With the exception of the ".", this should have been what you wrote down.
SOURCES .NOAA .NCEP .EMC .CMB .GLOBAL .Reyn_SmithOIv1 .climatology .sst
Click "OK".
CHECK
You have new selected both variables and should see both variables
indicated at the very top of the page. As mentioned above, operations that use this
technique are illustrated in subsequent sections.
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