GREarth User Guide


GREarth's main window contains several sections:


Getting Started

The first time you run GREarth you will see the main GREarth window along with several "Manager" windows overlaid on top. Move the Manager windows to locations suited for your Windows Desktop resolution. Two additional important, resizable windows also appear: "Active SPC Products" and "Active Warnings". Move them to suitable locations on your Windows Desktop. Now focus on the display part of the main GREarth window. The entire CONUS should be visible.


Navigation in the Display Window

To pan the display, click and drag with the left mouse button. To zoom in, roll your mousewheel forward. To zoom out, roll your mousewheel backwards. To zoom in on a specific area, right-click on the location you wanted centered and drag outwards. A zoom box will appear showing the extent of the new view area. Release the right mouse button to activate the new zoom area. To cancel the right-click zoom operation, press the Esc key before releasing the right mouse button.

You can save the current viewpoint to a "Favorites" list at the bottom of the Viewpoints main menu item. Navigate to the viewpoint of interest then select Viewpoints->Add To Favorites. Enter the name for the viewpoint in the dialog box and click OK. To go to that saved viewpoint in the future, select Viewpoints->[name of favorite]. To delete a saved favorite viewpoint, select Viewpoints then right-click on the saved name.

To set the startup viewpoint, navigate to the viewpoint desired then select Viewpoints->Set as Default. GREarth will start up with that viewpoint in the future.


Entering Your Client ID

In order to view live data in GREarth, you must enter a valid Client ID. To do this, select File->Start Polling or File->Configure Polling. The follow dialog will appear:

In the "Client ID" textbox, enter the Client ID you received. It is a long string of hexadecimal characters. Press the "Test" button to check to see if the Client ID you entered works properly. GREarth will show the test status in the textbox at the bottom. Once you have verified the Client ID is valid, press OK to permanently set the new ID. You are now ready to start viewing live data in GREarth.


CONUS Radar Mosaic and Storm Attributes

GREarth's data primary data feed is CONUS reflectivity. It is a lowest altitude, 1km resolution mosaic created from high resolution Level III data. It updates every five minutes. The timestamp of the reflectivity being displayed is shown at the top of the Info panel on the right. Two forms of the CONUS mosaic are available: a raw mosaic and a quality controlled (QC) mosaic. The raw mosaic shows all of the radar data received, including AP and GC. The QC mosaic uses Level III Echo Tops, RUC cloudbase, and RUC temperature fields to attempt to eliminate this AP/GC. The QC algorithm is most effective in summer conditions and less effective in winter conditions.

In addition to the CONUS mosaic, GREarth also displays CONUS-wide storm attributes derived from the Storm Attribute table in the Level III data feed. Due to the large number of storm attributes generated by the NEXRAD algorithms, GREarth filters out all attributes except for those with a TVS, ETVS, NMD, or a POH/POSH greater 30%. Icons are shown for each valid attribute along with a one hour storm track. Tick marks along the storm track are at 15 minute intervals. The default hail icons show the magnitude of the maximum expected hail size as a single digit. Hover your mouse pointer on the icon to see a popup window with the attribute details.

Up to four hours of reflectivity can be displayed. Use the VCR toolbar buttons to step through the hours of data available. To single step forward or backward, use the left or right arrow keys on your keyboard.

More information is available on the Radar Details page.


Severe Weather Warnings

GREarth supports Flash Flood, Severe Thunderstorm, and Tornado warnings. These warnings are displayed graphically in the display window and listed in the Active Warnings window. To see the text of a particular warning, click on the outline in the display window or right-click on its line in the Active Warnings window. To quickly zoom the display to a particular warning in the Active Warnings window, double-click on the warning line. 

Tornado warnings receive special treatment by GREarth. TOR warnings and associated SVS statements are searched for key phrases in order to determine the significance of the event in progress. TOR warnings are classified as regular (listed with a type of TOR), tornado reported (TORR), and tornado emergency (TORE). Each type uses a different, user-controlled line style for easy discrimination in the display window. Note that while GREarth detects most TORR and TORE events, the language used to report these events is not standardized and not all will be detected.


SPC Severe Weather Watches

GREarth supports Severe Thunderstorm and Tornado watches. Watches can be displayed as an outline and/or as a county fill. GREarth processes the watch statements and discriminates between regular and Particularly Dangerous Situation (PDS) watches. Each watch type has a user-controlled outline style for easy discrimination on the display window. To see the text of a watch, click on its outline in the display window or right-click on its line in the Active SPC Products window.


SPC MCD Statements

GREarth supports Mesoscale Discussions from the Storm Prediction Center. The MCDs are shown graphically in the display window and listed in the Active SPC Products window. GREarth parses the MCD statement text to determine the type of event being discussed: winter weather, heavy rainfall, severe thunderstorm, and tornado. If GREarth can't determine the type, the MCD is shown with the "Unknown" style. Each type of MCD has its own user-defined line style. To see the text of an MCD, click on its outline in the display window or right-click on its line in the Active SPC Products window.


Local Storm Reports (LSRs)

GREarth displays icons for each Local Storm Report that is within one hour of the currently displayed radar mosaic timestamp. For LSRs that typically contain a magnitude, e.g. HAIL, GREarth uses iconsheets with a fix range of associated values. The default iconsheets contain numerical values indicating the general size reported in the magnitude. Hover your mouse pointer over an LSR icon to see the complete report details.


SPC Day 1 Convective Outlook

GREarth displays seven SPC Day 1 Convective Outlook graphical fills:

  1. Categorical (None, Slight, Moderate, High, Extreme)

  2. Probability of Any Tornado

  3. Probability of Large Hail (1+")

  4. Probability of Damaging Wind Gusts (>50 kts)

  5. Probability of Extreme Tornado (EF2+)

  6. Probability of Extreme Hail (2+")

  7. Probability of Extreme Damaging Wind Gusts (>65 kts )

The SPC Outlook Manager window controls which graphical product is displayed. The background color of each item in the window indicates the maximum value in the current outlook.

To read the text of the Day 1 Convective Outlook statement, right-click on its line in the Active SPC Products window.


METAR Reports

GREarth displays real time METAR data for over 8000 stations worldwide. You can display icons for one of four METAR data fields: Present Weather, Temperature, Dewpoint, and Wind. The METAR Manager window controls which field is displayed. Hover your mouse pointer over a METAR icon to see the full report details. By default, only reports that are within two hours of the currently displayed radar mosaic timestamp are shown. 


NHC Tracks, Recon, and Model Data

GREarth displays National Hurricane Center tracks, recon reports, and hurricane model data. The official NHC tropical system tracks have two components: the center location and wind category, and the expected 34, 50, and 60 kt wind radii in each quadrant. Recon reports are shown in real time as the aircraft passes through tropical systems. Each recon report is shown as a wind category icon. The lowest surface pressure is shown as an "L" icon while the highest surface wind report is shown as a red up-arrow icon. Vortex Data Messages are shown as a red "V" icon. For the HWRF and GFDL hurricane models, GREarth shows icons indicating the wind category at 6 hr forecast positions. Hover your mouse pointer over any of these icons see more detailed information.

More information is available on the NHC Details page.


GOES Satellite Imagery

GREarth displays 1km visible, 4km infrared, and 4km water vapor imagery from GOES-East and GOES-West. This imagery is broken down into sectors: East Conus, Puerto Rico, East Tropical, West Conus, and Hawaii. Except for the East Tropical sector, these satellite images update at irregular intervals based on current weather conditions. The update rate can be as fast as every 5 minutes though typical times are every 15 minutes. The East Tropical sector updates at a fixed 30 minute interval.

More information is available on the GOES Details page.


Mesoanalysis Data

GREarth displays selected RUC model mesoanalysis fields for the entire CONUS. Several severe weather fields are available along with standard surface and upper air fields. The Filled fields are shown as a color-filled graphic underneath the radar data. The Overlays are contour lines or icons overlaid on the radar data. The data shown is the RUC forecast that is closest to the radar data timestamp, which is typically the one hour forecast.

More information is available on the Mesoanalysis Details page.


Background Imagery

GREarth displays background imagery downloaded on-demand from the Blue Marble Next Generation (BMNG), Landsat, and USGS NAIP aerial photography WMS servers. The specific source displayed depends on the zoom level and the available domain. At wide views, the BMNG source is selected. At intermediate zoom levels, the Landsat imagery is displayed. At tight zoom levels, the USGS NAIP aerial photography imagery is used. The quality of each source varies:

GREarth uses a quadtree tiled global mapping to render the background imagery. Tiles are downloaded as needed. Download times for the imagery vary widely. BMNG and Landsat imagery is downloaded from the JPL WMS server and is relatively fast on a fast internet connection. USGS NAIP imagery is fairly slow, even on a fast internet connection. However, GREarth caches all downloaded background imagery on your hard disk, so subsequent loading of the background imagery is very fast.