Using NASA’s Giovanni System to Detect and Monitor Saharan Dust Outbreaks
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Transcript of 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. AckerNASA 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:
a) an Italian astronomerb) a boy band (like Menudo)c) a restaurant in Baltimore’s Little Italy, or d) an unfinished Mozart opera.
So, then, what IS Giovanni?
GiovanniGiovanni used to stand for the Goddard Earth Sciences Data and Information Services Center (GES DISC) Interactive Online Visualization ANd aNalysis Infrastructure.
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 PeriodSelect Plot type
Generate Visualization
Refine constraints, and edit plot preferences
Outputs: Refine/Modify
24 different color palette options!
Giovanni data download page HDF, NetCDF, ASCII
Visualization image is here
Data download choices are here
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 andto 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.
DICCE-Giovanni Daily Data Portal
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 GiovanniData Portal
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 DataAtmosphere Daily Global 1X1 Degree Products
Choosing a region-of-interest
Click-and-
drag on the
map
MOVE
ZOOM
DRAW
Blue Marble
Borders
Choosing a data product& time period
Time periodselection
Data product selection
DICCE-G Daily
Interface!
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:
This March 5 peak in AOD
indicates a large dust storm
The other peaks indicate smaller
dust storms
To save anyimage, right-clickand “Save Image As”or “Save Picture As”,or the equivalent
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 imageof 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:
New color palette
New parameter
maximum value
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, March 1-5, 1994 Approximate location of
the Bodélé Depression
Deep Blue AOD animation frames, March 1-4, 2004
March 1 March 2
March 3March 4
Deep Blue AOD animation frameMarch 5, 2004
MODIS AOD, March 5, 2004
Tracking Saharan Dust OutbreaksUsing Aerosol Optical Depth and adjusting its “sensitivity”,
the impact of a Saharan dust outbreak over the tropical Atlantic Ocean can be tracked.
MODIS AOD forthe period March5-15, 2004, using1.5 as the upperbound value forthe color palette.
Leading edge
Tracking Saharan Dust Outbreaks
Upper boundvalue for AODpalette is now set to 0.5.
It now appearsthat elevatedAOD from thedust is affectingthe West Indies.
Tracking Saharan Dust Outbreaks
Same colorpalette range isused here; now for the periodMarch 15-20, 2004.
Higher values ofAOD over theWest Indies (andeven Puerto Rico), and notablyon the northeastcoast ofSouth America.
Fire?
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?
The relative humidity profile shows thedry air layer primarily between 500-600hPa, which is 4200-5600 meters, or13,000 – 18,000 feet.
The temperature profile doesn’tprovide as much information.
Dry air layer
Where is the Saharan dust in the atmosphere?
Mapping relative humidityin the 500 hPa layer shows the horizontal extent of the dry air layer.
Advanced: Latitude vs. TimeHovmöller plot
Tim
e
Latitude
As a guide, 36° N isthe latitude of theStraits of Gibraltar,and 6° N is about thelatitude where the West African coast turns westward.
The Hovmöller plot shows occurrencesof dry air off the “Saharan” coast. Thedust storm we havebeen examining impactedthis region between March 1st and March23rd.
Impacts on the Caribbean Sea?February 2004
Orinoco River
outflow region
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
Influence of Amazon
River waters
Phytoplankton growth here might be augmented by
iron from dust
Using Giovanni with Google EarthIf 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 EarthTo examine the question of whether the Saharan dust outbreak in March 2004affected Photosynthetically Available Radiation (PAR), three images for February,March, and April 2004 were generated.
February
April
March
Perhaps some influence here; needs better temporalresolution
Using Giovanni with Google Earth
With practice and experience withGoogle Earth, multiple data imagescan be displayed with geographicalcontext
The all-important final slide:
Any questions?