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Long Island Sound Extension

Many scientific studies correlate changes on an annual rate.  Therefore, it is important to be able to convert monthly data into yearly data. 

Below are graphs of chlorophyll concentrations found by scientists through water samples; amount and sources of nitrogen; and hypoxia - or loss of oxygen - events.  See how each correlates with your own yearly chlorophyll data generated with Giovanni.


Time Series (Giovanni)

  1. Select the area specified above.
  2. Parameter: Chlorophyll (SeaWiFS)
  3. Temporal:            Begin Date = 1998, Jan

End Date = 2007, Dec

  1. Select Visualization: Time Series

Export the data to an Excel spreadsheet by following these steps:

  1. Click on Download Data above the Giovanni Time Series image for the western plot.
  2. Scroll down to the bottom.  Under Time-Series Rendering, click ASC (this stands for ASCII data, which is data in text form). 

screen capture of asc data

  1. A new window will pop up with the complete data set.  Copy and paste to Notepad (or another text file editor) and save as ‘li_chloro’
  2. Open Excel.  From File, click Open.  Under Files of Type, scroll to All Files
  3. Now, your text files should appear.  Select one.  Change to Fixed Width.

screen capture for excel

  1. In the next step, make sure that Date is switched to MDY under Column Data Format. 

screen capture for excel


First, we must average the data for each year. 

  1. Enter ‘=average(B1:B12)’ to average the 1998 data.


  1. Do this for the remaining years.
  2. Select the years and the average chlorophyll concentration (i.e. Column C and D)
  3. Select Chart under the Insert toolbar. 
  4. Choose Column as your Chart Type

excel graph

Compare this Chart to other data supplied by the LIS Water Quality Program (click on each small image in the right-hand column to view the larger image and additional information provided with the image).


Satellite Chlorophyll:

chlorophyll satellite

Satellite Chlorophyll:

chlorophyll satellite

Satellite Chlorophyll:

chlorophyll satellite

In-situ Chlorophyll

chlorophyll in-situ

Nitrogen Loads:

nitrogen concentrations

Hypoxia Area and Duration (number of days):

hypoxia graph

Below are larger images with information about each.

chlorophyll blowup

nitrogen blowup

hypoxia blowup


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Last updated: Apr 06, 2016 10:25 AM ET