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
James G. Acker
NASA Goddard Earth Sciences Data and Information Services Center
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.
Select Area of Interest
Select Display (info, unit)
Select Plot type
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
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
Go to the Giovanni home page, http://giovanni.gsfc.nasa.gov/
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
Click-and-drag on the map
Data product selection
To save any
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
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.
MODIS pseudo true color image
of Saharan dust outbreak,
Adjust the region-of-interest slightly:
Select the “Lat-Lon map, Time-averaged” option (very popular):
New color palette
New parameter maximum value
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.
Approximate location of
the Bodélé Depression
MODIS AOD, March 5, 2004
Using Aerosol Optical Depth and adjusting its “sensitivity”,
the impact of a Saharan dust outbreak over the tropical
Atlantic Ocean can be tracked.
MODIS AOD for
the period March
5-15, 2004, using
1.5 as the upper
bound value for
the color palette.
value for AOD
palette is now
set to 0.5.
It now appears
AOD from the
dust is affecting
the West Indies.
palette range is
used here; now
for the period
Higher values of
AOD over the
West Indies (and
Rico), and notably
on the northeast
Employing the Atmospheric Infrared Sounder (AIRS) Daily data portal,
we can examine the atmospheric environment of the Saharan dust outbreak.
Choose Vertical Profile Layers
Choose Vertical Profile option
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.
Mapping relative humidity
in the 500 hPa layer
shows the horizontal
extent of the dry air layer.
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
The Hovmöller plot
of dry air off the
“Saharan” coast. The
dust storm we have
been examining impacted
this region between
March 1st and March
Sea surface temperature and phytoplankton
chlorophyll might show an influence of dust,
but there are other factors to be considered.
Phytoplankton growth here might be augmented by iron from dust
Influence of Amazon River waters
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
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
With practice and
multiple data images
can be displayed