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Using NASA’s Giovanni System to Detect and Monitor Saharan Dust Outbreaks. James G. Acker NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Part 1: Introduction to Giovanni. First, let’s clear up some misconceptions. Giovanni is not : an Italian astronomer

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using nasa s giovanni system to detect and monitor saharan dust outbreaks
Using NASA’s Giovanni System toDetect and Monitor Saharan Dust Outbreaks

James G. Acker

NASA Goddard Earth Sciences Data and Information Services Center


part 1 introduction to giovanni
Part 1: Introduction to Giovanni

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

an Italian astronomer

a boy band (like Menudo)

a restaurant in Baltimore’s Little Italy, or

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 ANdaNalysis


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 visualizationswith only a few mouse clicks.
main elements of giovanni
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
Getting Started with Giovanni

Select Area of Interest

Select Display (info, unit)

Select Parameters

SelectTime Period

Select Plot type

Generate Visualization


Outputs: Refine/Modify

Refine constraints, and edit plot preferences

24 different color palette options!


Giovanni data download page HDF, NetCDF, ASCII

Data downloadchoices are here

Visualization image is here

what is dicce giovanni
What is DICCE-Giovanni ?

DICCE (Data-enhanced Investigations for Climate Change

Education) is our current education-focused project using Giovanni.

DICCE data portals provide a much-reduced set of data parameters, from

several different missions and models, to simplify the use of Giovanni and

to make finding relevant and interesting data quick and easy.

The DICCE Daily Portal has many different data products related to dust,

Smoke, and volcanic emissions. Daily precipitation data products will be

added soon.

part 2 finding saharan dust outbreaks
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
Choosing a GiovanniData Portal

Go to the Giovanni home page,

Choose eithe the MODIS Daily data portal (Atmospheric Portals) or the DICCE-Daily Portal (Applications and Education Portals).

Both portals have MODIS Daily data:

MODIS Terra and Aqua Daily Level-3 Data

Atmosphere Daily Global 1X1 Degree Products

choosing a region of interest
Choosing a region-of-interest

Blue Marble


Click-and-drag on the map




choosing a data product time period
Choosing a data product& time period



Data product selection

Time period


choosing the visualization option
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
Giovanni produces this:

To save any

image, right-click

and “Save Image As”

or “Save Picture As”,

or the equivalent

This March 5 peak in AOD indicates a large dust storm

The other peaks indicate smaller dust storms

part 3 visualizing and interpreting images of saharan dust outbreaks
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
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
Back to the Giovanni interface…

Adjust the region-of-interest slightly:

Select the “Lat-Lon map, Time-averaged” option (very popular):

now change the plot preferences
Now change the Plot Preferences:

New color palette

New parameter maximum value

new data parameter modis deep blue aod
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 march 1 5 1994
Deep Blue AOD, March 1-5, 1994

Approximate location of

the Bodélé Depression

tracking saharan dust outbreaks
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


the period March

5-15, 2004, using

1.5 as the upper

bound value for

the color palette.

tracking saharan dust outbreaks1
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 outbreaks2
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
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 atmosphere1
Where is the Saharan dust in the atmosphere?

Choose Vertical Profile Layers

Choose Vertical Profile option

where is the saharan dust in the atmosphere2
Where is the Saharan dust in the atmosphere?

Dry air layer

The relative humidity profile shows the

dry air layer primarily between 500-600

hPa, which is 4200-5600 meters, or

13,000 – 18,000 feet.

The temperature profile doesn’t

provide as much information.

where is the saharan dust in the atmosphere3
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 hovm ller plot
Advanced: Latitude vs. TimeHovmöller 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 impacted

this region between

March 1st and March




impacts on the caribbean sea
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.

Orinoco River

outflow region

impacts on the caribbean sea2
Impacts on the Caribbean Sea?

April 2004

Phytoplankton growth here might be augmented by iron from dust

Influence of Amazon River waters

using giovanni with google earth
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 earth1
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 earth2
Using Giovanni with Google Earth

With practice and

experience with

Google Earth,

multiple data images

can be displayed

with geographical