Plotting Output Options in Giovanni
For each of the plot functions described below, the "Generate Plot" button at the bottom of the Giovanni interface would be clicked after the selection information has been provided to the interface.
Generate Plot button
5.1 Area Plot
The first output option in Giovanni is the Area Plot option. On the Selection Functions page, the following area was selected. The year 2004 was selected as the Time Period.
The output result of these selections is shown below. Note that Giovanni provides header information indicating the time period. The data shown are the chlorophyll concentrations for this region averaged over the entire year January-December 2004.
5.2 Time Plot
The second output option in Giovanni is the Time Plot option. On the Selection Functions page, a smaller area was selected, as shown below.
The Time Period selected was also January-December 2004. The Time Plot output result is shown below.
The Animation output option creates a series of monthly Area Plots for the selected region, and displays them sequentially. This option is useful for rapidly visualizing regions with seasonal variability and determining the most illustrative months for Area Plot output.
5.4 Hovmöller Plot (longitude versus time)
The two Hovmöller Plot output options create plots of the selected parameter as either longitudinal variation versus time or latitudinal variation versus time. These plots allow a two-dimensional representation of changes occurring in a given region spanning a selected time period. Using the same Area and Time Period selections as for the preceding Time Plot, the output result shown below is theHovmöller longitude versus time plot. Time is the Y-axis and longitude is the X-Axis. The data is averaged over the latitude range for the selected area.
5.5 Hovmöller Plot (latitude versus time)
The other Hovmöller Plot output option is the latitude versus time option. The same region and Time Period selections used for the two previous plots are used again for this output option. In this case, time is again the Y-axis, and latitude is the X-axis. The data are averaged over the longitude range of the selected region.
Since most maps are plotted with latitude changing vertically, it may be easier to comprehend this image if it is rotated so that the latitude variation becomes the Y-axis:
Hovmöller plots allow visualization of spatial variability that may not be apparent in a simple time plot in which the data for the entire selected region are averaged to a single value.