You should now be more comfortable with finding datasets in the Data Library. Let us take a closer look at the information and utilities available to you when you select a dataset. You will not use these utilities in this section, but it is important to know what they do and where they are for Parts II and III. The NOAA NCDC DAILY FSOD dataset is a commonly used dataset and is the example for this section.
Select NOAA NCDC DAILY FSOD*.
Views: The views icons on the left side of the function bar take you to an image of the selected data and a data viewer similar to that seen on this page. Let's quickly go over the different types of images seen here. The colored and contoured images generally display a spatial (e.g., [X,Z], [lon,lat]) image as either colors or contours. The line graph typically illustrates a time series (e.g., [data value,T]) image. Other types of views icons will appear depending on your data selection. It is important to remember that the image in the icon is representative of the image to which the icon is linked. We will talk much more about these links and their visualization capabilities in Part III.
When in Expert Mode there is a list of active datasets at the top of the page and a text window containing the command equivalent of the current page where the commands can be edited. Right now, you should see only one dataset, FSOD, noted as the active dataset. Because no variable has been selected, you can see all of the possible variables listed in this location as well. Much more detail about expert mode, including specific examples, will be given in Parts II and III.
Go bac k to the dataset main page by selecting the "FSOD" link in the source
bar or the dataset link in the navigation banner.
Select the "Data Tables" link.
The function bar is largely used to select, manipulate, and visualize data and will therefore be covered in much greater detail in Parts II and III. Keep in mind that many of the contents of the links in the function bar will appear signifcantly different after you have selected your data variable and station(s) or region. The goal here was just to introduce you the options available in the function bar.
The source bar, as described in the previous section, indicates to the user the location of the current dataset in the Data Library and offers the opportunity to go to any of the higher levels in the hierarchy by selecting one of the links. For example, you can view other NCDC datasets by selecting the "NCDC" link and other daily NCDC datasets by selecting the "DAILY" link. You should also notice the asterisk next to last link in the dataset path. This indicates that the documentation for the dataset is available and you can go to it by selecting the asterisk link.
The source bar is an extremely valuable navigation tool in the Data Library. Try using its options...
Dataset Map/Data Viewer
A dataset map will appear when the selected dataset is comprised of station data. Those datasets with gridded data will have a main page with an identical structure with the exception of this map. For example, look at the main page for the NOAA NCEP-NCAR CDAS-1 MONTHLY Diagnostic* dataset, which is a gridded dataset. You should note the options and structure of this page are identical to those of the FSOD dataset, with the exception of the dataset map.
The data viewer is an interactive interface that helps you find data for a specific location. The black dots on the map represent stations for which there is data in the dataset. The FSOD dataset primarily contains data from the United States and you can see that by the density of dots in the United States on the dataset map. You can select any of those stations by clicking on them. However, that may not be easy if the stations are as dense as they are here. Therefore, there a few options that make finding specific station(s) easier. First, you can zoom in on the map using the Zoom pull-down menu on the left side.
Go back to the default dataset map by clicking on the "FSOD" link in the source bar.
Go back to the dataset main page.
Select the "dataset documentation" link. CHECK
Datasets and variables
This is the same list of variables that you saw on the outline page. There is a link to each variable, as well as the abbreviated name of the variable in the dataset, and its grids (in brackets). You may notice that in this list the grids are time and WBAN instead of time and station as on the outline page. WBAN and station are synonymous- WBAN are the ids for stations. (Note: IWMO is another type of station ID and you may therefore see it in the station grid descriptions of other datasets.)
You may chose a variable from this list, but it is often easier to select the station(s) or region first. Right now, let's just look to see what information is available when we select a variable.
Select the pressure variable.
This is the typical information given for each variable. You are given the specific information about the grids as well as how the data are scaled, how missing values are replaced, and the units of the data.
You can think of grids as the ways in which the data are dependent. In this example, the data vary with each station as well as with time. The information after each grid indicates the units and range of the grid. For example, the time grid has units of julian days and has data from 1 Jan 1869 through 31 Dec 1999, which creates 47846 different time grid points. (Note: month is another common temporal grid unit.)
Grids vary from dataset to dataset, but there is a fundamental difference between those for station data and those for gridded data.
NCEP CPC GLOBAL daily* here.
This is a gridded dataset and, accordingly, it has latitude and longitude grids instead of a station grid. You can see this in the grid brackets with the Daily OLR variable as well as in the information below the Grids heading. The description of the latitude and longitude grid gives the spatial resolution of the data as well as the spatial range and number of grid points in each direction.