**Giovanni MERRA Practice Cases**

**(Prepared for AMS 2009 short course)**

Two Giovanni instances supporting MERRA products have been added into
Giovanni family recently. They are:

MERRA_MONTH_2D: Monthly data collection with 2-dimensional variable

<http://gdata1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=MERRA_MONTH_2D>

MERRA_MONTH_3D: Monthly data collection with 3-dimensional variable

<http://gdata1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=MERRA_MONTH_3D>

**General features of the MERRA 2D interface:**

**http://disc.gsfc.nasa.gov/mdisc/  Tools  Giovanni**
[MERRA_MONTH_2D](http://gdata1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=MERRA_MONTH_2D)

-   Spatial selection ( layer selection, pan and draw features, drag box
    or enter lon/lat)

-   Parameters selection ( total 6 2D collections, click on parameter to
    see description, time coverage , collapse of group box, show unit)

-   Time selection

-   Visualization function selection

**Case 1: Lat-lon map Time averaged**  Winter Precipitation

-   Area: ( 180W -- 180E, 50S-50N)

-   Total precipitation ( in group: Land surface diagnostics)

-   Begin Date: Jan 1979, End Date: Feb 1979

-   Lat-lon map, Time averaged

-   Click "Generate Visualization", to process and generate the image

-   On the result page, modify min/max to ( 0, 0.0003), or color
    palette, note that the value has been scaled on the plot

-   Click "Generate Visualization" to re-generate the image

-   Click on "download data" at the top

-   Click on "KMZ" icon to display through GoogleEarth

> ![](media/image1.png){width="5.111111111111111in"
> height="2.671527777777778in"}
>
> ![](media/image2.png){width="5.9944444444444445in"
> height="4.3277777777777775in"}

**Case 2: Time series**  Annual cycle of precipitation and surface
temperature over US

-   select US region

-   Total precipitation ( in group: land surface diagnostics) and
    surface skin temperature ( in group: surface and TOA radiation
    fluxes)

-   Begin Date: Jan 1979, End Date: Dec 1979

-   Time-series

-   Click "Generate Visualization", to process and generate the image

-   On the result page, edit plot preference "overlay lines"

![](media/image3.png){width="4.007638888888889in"
height="3.0055555555555555in"}

**Case 3: Animation ** See seasonal variation of surface skin
temperature over US

-   Area: US

-   Parameter: surface skin temperature ( in group: surface and AOT
    radiation fluxes)

-   Begin Date: Jan 1979, End Date: Dec 1979

-   Animation

-   Click "Generate Visualization", to process and generate the image

-   On the result page: modify color bar, set min/max (250/305) and plot
    again. This will make all image plotted in the same range.

-   Animation features: play, stop, control speed, loop, or swing, etc.

![](media/image4.png){width="4.10625in" height="2.863888888888889in"}

**General features of the MERRA 3D instance:**

**http://disc.gsfc.nasa.gov/mdisc/  Tools  Giovanni**
[MERRA_MONTH_3D](http://gdata1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=MERRA_MONTH_3D)

-   3D interface has features of 2D interface plus:

-   Vertical Profile: allow to select vertical levels. Currently,
    average of levels (layers) is not supported**.**

**Case 4: Cross Map, Latitude-Pressure**  zonal mean vertical cross
section of air temperature

-   Area: global

-   Vertical: Upper Level = 100hPa, Low Level = 1000 hPa

-   Parameter: Air Temperature (in group: Basic assimilated fields from
    IAU corrector)

-   Begin Date: July 1999, End Date: Jul 1999

-   Visualization: Cross Map Latitude-Pressure

> ![](media/image5.png){width="4.002777777777778in"
> height="2.8541666666666665in"}
>
> **Case 5: Vertical Profile**  temperature vertical profile over
> eastern US

-   Area: ( 90W -- 80W, 35N-45N)

-   Vertical: Upper Level = 0.1 hPa, Low Level = 1000 hPa

-   Parameter: Air Temperature (in group: Basic assimilated fields from
    IAU corrector)

-   Begin Date: July 1999, End Date: Jul 1999

-   Visualization: Vertical Profile

> ![](media/image6.png){width="3.8715277777777777in"
> height="2.765277777777778in"}
>
> **Case 6: A-Train Giovanni ** vertical structures of Storm Ernesto
>
> (A preview of a future MERRA feature)
>
> [http://giovanni.gsfc.nasa.gov](http://giovanni.gsfc.nasa.gov/) 
> A-Train
>
> <http://gdata1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=atrain>

-   Select location on the track (near US, (18N-45N, 80W- 75W) ). You
    may change the map view for selecting ascending, descending, or
    projection, and change the view range

-   Date: Aug 31 2006

-   Parameters: Specific Humidity Profile of ECMWF model in group Water
    Vapor, Reflectivity dBZ if CloudSAT in group Cloud

-   Click on "Generate Visualization" to re-generate the image

> ![](media/image7.png){width="4.927777777777778in"
> height="2.8958333333333335in"}
>
> ![](media/image8.png){width="5.752777777777778in"
> height="3.3958333333333335in"}
>
> ![](media/image9.png){width="5.986111111111111in"
> height="3.5416666666666665in"}