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 Period

Select 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 ofthe 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 Outbreaks

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 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?