b. Selecting a region
Example: Select all of the stations in the region defined by 70°-20°W,
10°S-10°N.
Method 1: Data Viewer
Go back to the GLOBALSOD dataset main page via the source bar.
The utilities of this map are described in the previous section.
If you are unfamiliar with how to use this map or need to review these options,
then please refer to this
previous discussion.
While it
is possible to select a single station using the data viewer, this tool is most
appropriately used when selecting numerous stations from a specific geographic
location.
Enter "10N", "10S", "70W", and "20W" into their appropriate
lat/lon text boxes in the data viewer and click "Redraw".
CHECK
This new map allows you to see all of the stations (black dots)
in this lat/lon defined region. You have the option to click on one of those dots
to select a single station. but right now we will continue with the steps that
allow you to select all of the stations in the region.
Select the "List of stations in current view" link below
the map. CHECK
You now have search results in the same format as when you
searched for the stations in Buenos Aires. As in that example, you may select any number
of those stations by clicking on their WMO ID box and then the "Get Marked
Stations" button. We will continue through the steps that allow you to select
all of the stations in this region.
Select the "Dataset (and map) with all data found in search"
link below the gray table. CHECK
You have now selected stations from a region in northeastern
South America. Note that the page now looks very much like the dataset main page
on which we started, with the exception of the source bar. Your station selection
resides in the lowest level of the source bar. You should also note that only
stations within your selected region appear on the dataset map.
Method 2: Searches
Go back to the GLOBALSOD dataset main page using the source bar.
Select the "Searches" link to the right of the dataset map.
CHECK
We should use the lat/lon limits search option for this example.
Enter "-70" (top left box), "-20" (bottom left box), "-10" (upper
right box), and "10" (bottom right box) into the appropriate lat/lon text boxes and
select the "Search NOAA NCDC DAILY GLOBALSOD" button. (Note the different lat/lon format
from that in the data viewer example above.)
CHECK
You now have search results that are identical to those
found by Method 1. Below the the search results table you can see
that there are 177 stations within these lat/lon limits.
The steps to select only specific stations or all of the stations is identical
as in Method 1 of of the previous example.
Method 3: Expert Mode
Go back to the NOAA NCDC DAILY GLOBALSOD dataset main
page using the blue navigation bar.
Select the "Expert Mode" link in the function bar .
Enter the following lines in the text box below the text already there.
lon
290 340 masknotrange
SELECT
lat
-10 10 masknotrange
SELECT
Click "OK". CHECK
Note the convention for indicating
the latitude and longitude. The latitude is given in order from south
to north with latitudes in the southern hemisphere assigned negative values.
The longitude is given in order from west to east and as °E.
There is another way to indicate longitude as well. This additional
sign convention still gives the limits in order from west to east, but
assigns negative values to longitudes in the western hemisphere.
Try this other sign convention.
Replace 290 340 masknotrange with the following line.
-70 -20 masknotrange
Click "OK".
CHECK
You have the same data selection as in the previous methods
and should see your selection in the source bar, dataset map, and the grid
information.
We will return to a discussion of selecting a data variable for
station data in the next section after the following discussion of selecting
grid points/regions in a gridded dataset. If you are not interested in gridded
datasets, you may want to skip directly to this
next section.
2. Gridded Data
Select NOAA
NCEP EMC CMB GLOBAL Reyn_SmithOIv1*.
You should note that all of the options used in the previous
example to search for stations were dependent on characteristics of the
individual stations. Because we are now dealing with a gridded dataset,
these characteristics and their associated searching mechanisms are not
applicable, except for the lat/lon coordinates. Selecting lat/lon limits
is the only way to select a specific region for a gridded dataset. Let's
take a look at the different methods that can be used to select lat/lon
limits for gridded datasets. (Note: Some of these methods are similar to
those used with station datasets.)
a. Selecting a single grid point
Example: Select data at the grid point nearest to 120°E,
25°N.
Method 1: Data Selection Link
Select the "Data Selection" link in the function bar.
We will discuss this link again in the next section "Selecting
a Data Variable". In this operation, we must select a data variable before
selecting our geographic region of interest. Let's use the climatological SST
data as an example.
Select the "climatology Sea Surface Temperature" link.
CHECK
Enter "120E" and "25N" in the appropriate text boxes in the Setting
Ranges table.
Note the default ranges in the gray Data Selection box at the top of the page.
Select the "Restrict Ranges" button.
CHECK
The ranges in the Data Selection box are now indicative of
the coordinates you entered.
Select the "Stop Selecting" button in the Data Selection box.
CHECK
You have selected data at a single grid point in the Formosa
Strait and, as always, this is indicated in the source bar and in the grid
information. Note that the point we entered does not exactly coincide with the location of a
grid point. The grid point nearest to our selected point is automatically chosen.
Remember that you can find information on the grid resolution of the dataset on the
dataset main page under the Grids heading.
Method 2: Expert Mode
Go back to the Reyn_Smith dataset main page using the source bar.
CHECK
Select the "Expert Mode" link in the function bar .
CHECK
Enter the following sets of lines in the text box below the
text already there. (Again, we must select a variable and use climatological sst as an example.)
.climatology .sst
Y (25N) VALUES
X (120E) VALUES
Click "OK".
CHECK
You have selected the same grid point as in Method 1 and should
see your selection in the source bar and in the grid information.
b. Selecting a region
Example: Select the data in the region defined by 70°-20°W,
10°S-10°N.
Method 1: Data Viewer
When dealing with a gridded dataset we must select a
data variable before being able to use the Data Viewer. We will talk
more about the information available when selecting a data variable in
the next section, but for right now we will use the climatological
sea surface temperature data as an example.
Go back to the Reyn_Smith dataset main page using the
source bar. CHECK
Select the "climatology" link under the Datasets
and variables heading.
Select one of the [X,Y] views links (e.g., colored or contoured) in the
function bar (lower left corner of the bar).
CHECK
You have now entered the data viewer. Keep in mind that
you can always reach the data viewer by selecting one of the views links in
the function bar.
Enter "10N", "10S", "70W", and "20W" into their
appropriate lat/lon text boxes and click "Redraw".
CHECK
You have now selected gridded climatological sea surface
temperature data for the Atlantic Ocean off of northeastern South America.
To exit the data viewer and save this geographic selection...
Select the "data in view" button in the table at
the bottom of the page.
CHECK
Note that the lowest levels of the source bar indicate
your data selections.
Method 2: Data Selection Link
Go back to the Reyn_Smith dataset main page via
the navigation banner or the source bar.
Select the "Data Selection" link in the function bar.
We will discuss this step again in the next section
"Selecting a Data Variable". As in Method 1, we must select a data variable
before selecting our geographic region of interest. Let's use the
climatological data again.
Select the "climatology Sea Surface Temperature" link.
CHECK
Take a moment to look at the hints offered below the
Setting Ranges table as they include valuable information. According to
the hints we should enter our lat/lon limits in the following way:
Enter "70W to 20W" and "10S to 10N" in the appropriate
text boxes in the Setting Ranges table.
Note the default ranges in the gray Data Selection box at the top of
the page.
Select the "Restrict Ranges" button.
CHECK
The ranges in the Data Selection box should now be
indicative of the limits you entered.
Select the "Stop Selecting" button in the Data Selection
box. CHECK
You have again selected gridded data for the Atlantic
Ocean off of northeastern South America and this region of data is again
indicated in the source bar.
Method 3: Expert Mode
Go back to the Reyn_Smith dataset main page.
Select the "Expert Mode" link in the function bar .
As noted above, there is more than one acceptable
lat/lon convention.
Enter one of the following sets of lines in the text
box below the text already there.
Y (10S) (10N) RANGE
X (70W) (20W) RANGE
OR
Y (-10) (10) RANGE
X (-70) (-20) RANGE
Click "OK".
CHECK
Note that the lowest levels of the source bar will match which
convention you chose to follow. Again, you have selected data for a region
identical to those in Methods 1 and 2.
