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.
Start at the CDAS-1 monthly intrinsic dataset main page*.
Example: Select the Pressure level zonal wind variable from the CDAS-1 monthly intrinsic
dataset.
Method 1: Dataset and Variables Links
Select the PressureLevel link under the Datasets and variables heading.
Select the zonal wind link under the Datasets and variables heading.
CHECK
Method 2: Data Selection tab
Go back to the CDAS-1 monthly intrinsic dataset main page.
Select the "Data Selection" tab in the function bar.
CHECK
Select the "PressureLevel zonal wind" 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 us 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 CDAS-1 monthly intrinsic dataset main page.
Select the "Expert Mode" tab in the function bar.
In the text box at the top of the page, enter the following line below the text already
there.
.PressureLevel .u
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 us use the Lesotho ENACTS ALL monthly dataset this time. As always, start on the dataset main page*.
Example: Select the monthly climatological rainfall and monthly observed rainfall data variable from the Lesotho ENACTS ALL monthly dataset.
Use the links under the Datasets and variables heading to select the monthly climatological
rainfall variable.
CHECK
Write down the directory structure indicated in the source bar. (Note that the structure
actually begins with "SOURCES", but it might not be 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 observed
rainfall 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 monthly observed rainfall 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 .Lesotho .ENACTS .ALL .monthly .climatologies .rfe
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.