Document Sample
Giovanni_Coastal2011_Acker Powered By Docstoc
					      Using NASA’s Giovanni System to
            Detect and Monitor
          Saharan Dust Outbreaks

James G. Acker
NASA Goddard Earth Sciences Data and Information Services Center
African Dust Workshop 2011
     Part 1: Introduction to Giovanni

First, let’s clear up some misconceptions. Giovanni is not:

a)   an Italian astronomer
b)   a boy band (like Menudo)
c)   a restaurant in Baltimore’s Little Italy, or
d)   an unfinished Mozart opera.

              So, then, what IS Giovanni?
Giovanni used to stand for the Goddard Earth Sciences Data and Information
Services Center (GES DISC) Interactive Online Visualization ANd aNalysis

                      But we just call it “Giovanni” now.

    It’s a Web-based application
     developed by the NASA GES DISC

    It’s easy to use
     There’s no need to learn data formats, programming, or to download
      large amounts of data

    You get customized data analyses and
     visualizations with only a few mouse clicks.
   Main Elements of Giovanni

 Interactive map for region-of-interest selection

 Compendium of available data products for analysis

 Calendrical selection of time period of interest

 Menu of visualization options
        Getting Started with Giovanni

Select Area of Interest

 Select Display (info, unit)

 Select Parameters

 Select Time Period
 Select Plot type

 Generate Visualization
Outputs: Refine/Modify

                         Refine constraints, and
                         edit plot preferences
Giovanni data download page

          Visualization image is here
    Part 2: Finding Saharan Dust Outbreaks

In this section, the use of the Giovanni system to find
occurrences of Saharan dust outbreaks will be demonstrated.
You will learn how to:

•   Choose a region-of-interest
•   Choose a time-period of interest
•   Select a data product for visualization
•   Select a visualization option
•   View and interpret the generated visualization
•   Save the visualization
                Choosing a Giovanni
                    Data Portal
We’re going to have a better, easier-to-use Giovanni
home page very soon.

So now, we’ll choose the MODIS Daily data portal.

The MODIS Daily data portal has:

         MODIS Terra and Aqua Daily Level-3 Data
          Atmosphere Daily Global 1X1 Degree Products
       Choosing a region-of-interest

Choosing a data product
    & time period

           Data product

                          Time period
     Choosing the visualization option

In this case, the “Time Series” option is selected from a drop-down menu.

In these steps, we have selected:
 The coast of northwestern Africa as the region-of-interest;
 The data parameter - Aerosol Optical Depth at 550 nanometers from MODIS
 The time period January-August 2004
 The time-series visualization option

So what happens when “Generate Visualization” is clicked?
                        Giovanni produces this:
To save any
image, right-click
and “Save Image As”
or “Save Picture As”,
or the equivalent

                                        The other peaks
                                        indicate smaller
                                          dust storms
 Part 3. Visualizing (and Interpreting)
  Images of Saharan Dust Outbreaks

Now that Giovanni has helped find a large Saharan dust
outbreak in early March 2004, the next step is to use
Giovanni to see what it looked like, according to the data.
    But first…
 what did it look
like from space?

MODIS pseudo true color image
of Saharan dust outbreak,
March 2004
  Back to the Giovanni interface…
 Adjust the region-of-interest slightly:

Select the “Lat-Lon map, Time-averaged” option (very popular):
MODIS Aerosol Optical Depth at 550 nm,
           March 5, 2004
Now change the Plot Preferences:
which produces this:
Other color palette choices
         New data parameter:
        MODIS “Deep Blue” AOD

The MODIS “Deep Blue” aerosol optical depth data
parameter allows retrieval of AOD values over bright
land areas, where the standard AOD algorithm fails.

Using “Deep Blue” AOD, the source areas of Saharan
dust outbreaks which migrate over the Atlantic Ocean
can be observed.
Deep Blue AOD,    Approximate location of
March 1-5, 1994   the Bodélé Depression
          Deep Blue AOD animation frames,
                  March 1-4, 2004

      March 1            March 2

March 3
                       March 4
    Deep Blue AOD animation frame
            March 5, 2004

MODIS AOD, March 5, 2004
   Tracking Saharan Dust Outbreaks
Using Aerosol Optical Depth and adjusting its “sensitivity”,
 the impact of a Saharan dust outbreak over the tropical
              Atlantic Ocean can be tracked.

               Leading edge                   MODIS AOD for
                                              the period March
                                              5-15, 2004, using
                                              1.5 as the upper
                                              bound value for
                                              the color palette.
Tracking Saharan Dust Outbreaks

                           Upper bound
                           value for AOD
                           palette is now
                           set to 0.5.

                           It now appears
                           that elevated
                           AOD from the
                           dust is affecting
                           the West Indies.
Tracking Saharan Dust Outbreaks

                           Same color
                           palette range is
                           used here; now
                           for the period
                           March 15-20,

                           Higher values of
                           AOD over the
                           West Indies (and
                           even Puerto
                           Rico), and notably
                           on the northeast
                           coast of
                           South America.
            Where is the Saharan dust
              in the atmosphere?
Employing the Atmospheric Infrared Sounder (AIRS) Daily data portal,
we can examine the atmospheric environment of the Saharan dust outbreak.
Where is the Saharan dust
  in the atmosphere?

       Choose Vertical Profile Layers

        Choose Vertical Profile option
               Where is the Saharan dust
                 in the atmosphere?

                  Dry air layer

The relative humidity profile shows the
                                          The temperature profile doesn’t
dry air layer primarily between 500-600
                                          provide as much information.
hPa, which is 4200-5600 meters, or
13,000 – 18,000 feet.
Where is the Saharan dust
  in the atmosphere?

               Mapping relative humidity
               in the 500 hPa layer
               shows the horizontal
               extent of the dry air layer.
       Advanced: Latitude vs. Time
             Hovmöller plot
                              As a guide, 36° N is
                              the latitude of the
                              Straits of Gibraltar,
                              and 6° N is about the
                              latitude where the
                              West African coast
                              turns westward.

                              The Hovmöller plot

                              shows occurrences
                              of dry air off the
                              “Saharan” coast. The
                              dust storm we have
                              been examining
                              this region between
                              March 1st and March
   Impacts on the Caribbean Sea?
February 2004   Sea surface temperature and phytoplankton
                chlorophyll might show an influence of dust,
                but there are other factors to be considered.
   Impacts on the Caribbean Sea?
March 2004
    Impacts on the Caribbean Sea?
April 2004
                           growth here might
                            be augmented by
                             iron from dust
                 Water Quality –
             ocean optical parameters
                 Water Quality –
             ocean optical parameters
The question is: how much of the remotely-sensed chlorophyll is actually
phytoplankton chlorophyll?

                                                 This is what the standard
                                                 chlorophyll a data product
                                                 looks like for April 2004.
                 Water Quality –
             ocean optical parameters
Looking at other data products provides improved insight into the identity
of the optically-active constituents in the water.

                                               Euphotic depth (1% light
                                               level) is a standard
                                               indicator of light
                                               penetration, and thus,
                                               turbidity in all its forms.
                Water Quality –
            ocean optical parameters
The Colored Dissolved Organic Matter (CDOM) Index shows that CDOM is
pervasive in the Orinoco River plume – and the Amazon River plume.
                  Water Quality –
              ocean optical parameters
The absorption coefficient for dissolved and detrital matter (adg) reinforces
the information from the CDOM Index.
                   Water Quality –
               ocean optical parameters
So where’s the phytoplankton? The absorption coefficient for
phytoplankton, aph, shows that there is some – but less than expected?
 Using Giovanni with Google Earth
If you generate an image, one of the file download options is a KMZ file,
which will open in Google Earth.

                            GIF image       KMZ file
 Using Giovanni with Google Earth
To examine the question of whether the Saharan dust outbreak in March 2004
affected Photosynthetically Available Radiation (PAR), three images for February,
March, and April 2004 were generated.



                              Perhaps some influence here; needs better temporal
Using Giovanni with Google Earth

                         With practice and
                         experience with
                         Google Earth,
                         multiple data images
                         can be displayed
                         with geographical
The all-important final slide:

       Any questions?

Shared By: