Animating NetCDF Data in ArcMap

Virginia Smith, CRWR

 

Table of Contents

 

Introduction

NetCDF

NetCDF is a data format and library designed to store multidimensional arrays of scientific data, and is widely used in the atmospheric sciences and oceanography.  Additionally, netCDF files are self-describing and can be linked with geographic features easily through GIS.  While relatively new to GIS, netCDF has a long history of use in the science community.  Unidata, a largely NSF funded program under the University Corporation for Atmospheric Research (UCAR), is the “home” of netCDF and provides the following definition:

 

NetCDF (network Common Data Form) is an interface for array-oriented data access and a library that provides an implementation of the interface. The netCDF library also defines a machine-independent format for representing scientific data. Together, the interface, library, and format support the creation, access, and sharing of scientific data.  <http://www.unidata.ucar.edu/software/netcdf/>

 

Additoanlly, UCAR is the chief source of netCDF software, standards development, updates, etc.  .  

 

NetCDF’s useful format and divisibility it can be used in many different ways.  NetCDFs are used by varying agencies to represent different aspects of specfic fields. Some of the agencies that employ NetCDF are:

 

The National Center for Atmospheric Research (NCAR)

University Corporation for Atmospheric Research (UCAR)

NOAA’s Climate Diagnostics Center (CDC)

Los Alamos National Laboratory (LANL)

The National Center for Supercomputing Applications

US Air Force and Navy

Atmospheric Research in Australia

Australia Defense

UK Hydrographic Office

NATO

And more…

 

 

NetCDF in ArcGIS 9.2

ArcGIS version 9.2 introduces support for working with netCDF files.  With the Multidimension Tools toolbox allows users to create netCDFs or create features, rasters or tables from netCDFs.

 

Figure 1:  The Multidimension Tools toolbox is new for ArcGIS 9.2

 

Using GIS netCDF files can be converted and displayed in raster, feature class or tabular format.  GIS can also be used to create netCDF files.  In ArcToolbox netCDF files can be created using raster, feature or table files.

 

 

 

Figure 2:  Examples of netCDF data displayed in ArcGIS 9.2

 

 

 

Also new in ArcGIS 9.2 is the Animation toolbar and Animation Manager, which supports the animation of data through space and time. 

 

This document walks you through the procedure for downloading and animating netCDF data in ArcMap. 

 

Downloading NARR NetCDF Data

The National Centers for Environmental Prediction (NCEP) produce the North American Regional Reanalysis (also known as NARR), which is a consistent historical climate data for North America.  This data is published in an online catalog at:

 

http://nomads.ncdc.noaa.gov:8085/thredds/catalog.html

 

In this portion of the exercise, you will download a netCDF file of potential evaporation data (in millimeters per 3 hours) from the NARR. 

 

Note:  If you do not have a high speed Internet connection, or if the netCDF server is down, you may skip to the Adding NetCDF Data to ArcMap section of the exercise and use the files found here.

 

  1. Open a web browser (e.g., Mozilla Firefox, Internet Explorer, etc.).
  2. Browse to http://nomads.ncdc.noaa.gov:8085/thredds/catalog.html.
  3. Click North American Regional Reanalysis (NARR)-Monthly/  to view the catalog of data by year. (North American Regional Reanalysis (NARR)/ will take you to a similar catalog for daily data.)

 

 

 

  1. There is a list of six digit numbers.  The first four numbers represent the year of the data.  The last two digits of the number represent the month.  Scroll down to 200001 and select this link.  This is the data for January, 2000.

 

 

  1. Click on the file listed in that folder.

 

 

  1. Click the first file in the list, narrmon-a_221_20000101_0000_000.grb.  The data available through this link is the average data over a three hour span for the month of January.  (Narrmon-a has grids of physical parameters such as humidity, evaporation or precipitation, and narrmon-b has radiation data.  Also, the second to last four digit number changes in the list.  This number represents the time.  0300 represents 3:00 am Greenwich Mean Time.  The data available through that link is the average monthly values for that three hour time span)

 

 

 

  1. Click the link in the Access section after Netcdf Server.

 

 

 

NetcdfServer provides a user interface for extracting a portion of a NARR  dataset.  You will use NetcdfServer to download the evaporation data from within the dataset.

 

  1. Scroll to the bottom of the page and check Evaporation. (*For a complete list of the parameter grids available see the bottom of the document.)

 

 

For the bounding box and forecast hours, you will accept the defaults in order to download data for the entire prediction time range and the entire model area.

  1. Scroll back up and click Submit. 

 

  1. After a few moments, you will be prompted to save the resulting netCDF file to your computer.  Click Save and save the file to your computer.

 

 

You have now downloaded evaporation data from NCEP’s NARR catalog in netCDF format.  To add this data to ArcMap as a raster layer scroll down to Adding NetCDF Data to ArcMap on this page.

 

Downloading RADAR Stage IV NetCDF Data

 

RADAR Stage IV data is also available at the National Centers for Environmental Prediction (NCEP).  This data provides precipitation for North America.  The data is collected using RADAR.  This data is published in an online catalog at:

 

http://nomads.ncdc.noaa.gov:8085/thredds/catalog.html

 

In this portion of the exercise, you will download a netCDF file of precipitation data the RADAR Stage IV dataset.

 

1.      Open a web browser (e.g., Mozilla Firefox, Internet Explorer, etc.).

2.   Browse to http://nomads.ncdc.noaa.gov:8085/thredds/catalog.html.

  1. Click Radar Dataset/ to view the catalog of Radar datasets.
  2. Click StIV/ to access the Stage IV data.
  3. Select the year of data you are interested in.
  4. Select the month of data you are interested in.
  5. Select the day of data you are interested in.
  6. Now you have a choice.  You can either choose to retrieve daily precipitation values or hourly precipitation values.  For this example, choose day/.
  7. Click on the file shown. 
  8. Select the netCDF server.
  9. Enter  the bounding box (as shown in the previous exercise).  Check the total precipitation box.

  1. Scroll back up and click Submit. 

 

  1. After a few moments, you will be prompted to save the resulting netCDF file to your computer.  Click Save and save the file to your computer.

 

 

You have now downloaded precipitation data from NCEP’s the RADAR Stage IV catalog in netCDF format. 

 

 

 

Adding NetCDF Data to ArcMap

With the Multidimension Tools, you can visualize netCDF data as a feature layer, raster layer, or table view in ArcMap.  In this portion of the exercise, you will add the precipitation data to ArcMap as a netCDF raster layer.

 

  1. Open a new map file in ArcMap. 

 

 

  1. If you can’t see ArcToolbox, click the Show/Hide ArcToolbox Window button.

 

 

  1. In ArcToolbox, expand the Multidimension Tools toolbox.
  2. Double click the Make NetCDF Raster Layer tool to run the tool.

 

 

  1. Input the path to the netCDF file that you downloaded.  Make sure potential_evapation is listed as the Variable, x is listed as the X Dimension, and y is listed as the Y Dimension.

 

 

  1. Click OK to create the layer.  The map now shows a raster layer of the average potential evaporation in millimeters per 3 hours for January 2000.  By default, data the first time stamp in the netCDF is displayed. 

 

 

 

Animating the Evaporation Data

The Animation Manager in ArcGIS 9.2 is a powerful utility with features for creating various types of animations in ArcMap.  More information and tutorials about animating in ArcMap can be found in the ArcGIS Desktop Help in the Mapping and Visualization heading.

 

 

In this portion of the exercise, you will use the Animation Manager to animate the netCDF precipitation raster through time.  To complete this exercise download the netCDF zipped data file (link).  This file contains 12 raster images representing the average monthly potential evaporation data.   The data used to create these rasters came from NARR.  These rasters were formed uses the methods described above.  Begin a new map file and add all of the rasters to this file.  Adjust their color scales to your liking.  Put these in order by date. Once your display is set we are ready to being animating.  The first step is to create a new animation track and keyframes.

 

  1. If you can’t see the Animation toolbar, click View, then point to Toolbars, then click Animation.
  2. In the Animation toolbar, click the Animation menu, and then click Create Keyframe…

 

 

In the Create Animation Keyframe window that opens, you will create a new track for your animation, and create the start and end keyframes within the track.  These are the minimal keyframes required for an animation.

 

  1. For Type, select Time Layer.
  2. For Source object, select the first layer to be animated, in this case it will be pe01 (or whatever you netCDF raster layer is called).
  3. Click New to create a new destination track for your keyframe.
  4. Input start as the Keyframe name, and click Create.  This creates a new keyframe, which you see in the Animation Manager later on.

 

 

  1. Input end as the Keyframe name, replacing “start” (for this case it will be pe12).  Then click Create.

 

 

  1. Click Close.

 

The next step is to use the Animation Manager to calculate the time stamps for the start and end keyframes, and specify the duration of each frame.

 

  1. Click the Animation menu, and then click Create Group Animation…

 

 

 

  1. Select One layer at a time.

 

 

  1. Click Ok.
  2. Click the Animation menu, and then click Animation Manager…
  3. Select the Keyframes tabs.
  4. Select MapView under the Keyframes of Type drop down menu.

 

 

  1. Select the Time View tab.  This should look like the image shown below.

 

 

  1. Click Close.
  2. Add Calcounties and Continents shapefiles to the map.  Calcounties shows the countries of California and  Continents shows the outline of the world’s continents.

 

Now you’re ready to animate the data.

 

  1. On the Animation toolbar, click the Open Animation Controls button.

 

 

  1. On the Animation Controls toolbar, click the Play button.

 

 

The display will animate the precipitation data through time.  A text label shows the current time stamp for the data, and the progress bar at the bottom of the ArcMap display shows the total progress of the animation.

 

 

Congratulations!  You have downloaded precipitation data in netCDF format, added the data to ArcMap as a raster layer, and animated the data through time.  Be sure to peruse the NCEP catalog for more information about available datasets, and check out the ArcGIS Help for more information about customizing animations in ArcMap.

 

Primary Contact

Virginia Smith
University of Texas at Austin

e-mail: virginia_smith@mail.utexas.edu
Phone: (512) 471-0570

These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 2007 Center for Research in Water Resources.

Appendix

 

Parameter Selection Grids Available through NARR:

Accumulated_snow
Albedo
Best_4-layer_lifted_index
Blackadars_mixing_length_scale
Canopy_conductance
Categorical_freezing_rain
Categorical_ice_pellets
Categorical_rain
Categorical_snow
Cloud_water
Convective_available_potential_energy
Convective_available_potential_energy_surface
Convective_cloud_cover
Convective_inhibition
Convective_inhibition_surface
Convective_precipitation
Dew_point_temperature
Downward_longwave_radiation_flux
Downward_shortwave_radiation_flux
Evaporation
Exchange_coefficient
Geopotential_height
Geopotential_height_hybrid
Geopotential_height_maximum_wind
Geopotential_height_tropopause
Geopotential_height_zeroDegC_isotherm
Ground_Heat_Flux
High_level_cloud_cover
Horizontal_moisture_divergence
Horizontal_moisture_divergence_hybrid
Horizontal_moisture_divergence_isobaric
Humidity_parameter_in_canopy_conductance
Ice_mixing_ratio
Latent_heat_flux
Liquid_volumetric_soil_moisture_non-frozen
Low_level_cloud_cover
Mean_sea_level_pressure_ETA_model
Mid_level_cloud_cover
Moisture_availability
Non-convective_cloud
Planetary_boundary_layer_height
Plant_canopy_surface_water
Potential_evaporation
Potential_temperature
Potential_temperature_hybrid
Potential_temperature_surface
Precipitable_water
Precipitation_rate
Pressure
Pressure_adiabatic_condensation_lifted
Pressure_hybrid
Pressure_maximum_wind
Pressure_nearest_grid_point
Pressure_reduced_to_MSL
Pressure_surface
Pressure_tropopause
Pressure_vertical_velocity
Pressure_vertical_velocity_hybrid
Pressure_vertical_velocity_layer_between_two_pressure_difference_from_ground
Relative_humidity
Relative_humidity_hybrid
Relative_humidity_zeroDegC_isotherm
Sensible_heat_flux
Snow_cover
Snow_depth
Snow_melt
Snow_phase-change_heat_flux
Soil_moisture_content
Soil_moisture_parameter_in_canopy_conductance
Soil_temperature
Soil_temperature_depth_below_surface
Solar_parameter_in_canopy_conductance
Specific_humidity
Specific_humidity_height_above_ground
Specific_humidity_hybrid
Specific_humidity_layer_between_two_pressure_difference_from_ground
Storm_relative_helicity
Subsurface_runoff_baseflow
Surface_drag_coefficient
Surface_friction_velocity
Surface_lifted_index
Surface_runoff_non-infiltrating
Temperature
Temperature_height_above_ground
Temperature_hybrid
Temperature_layer_between_two_pressure_difference_from_ground
Temperature_parameter_in_canopy_conductance
Temperature_surface
Temperature_tropopause
Total_cloud_cover
Total_precipitation
Total_precipitation_nearest_grid_point
Turbulent_Kinetic_Energy
Turbulent_Kinetic_Energy_hybrid
Upward_long_wave_radiation_flux
Upward_long_wave_radiation_flux_surface
Upward_short_wave_radiation_flux
Upward_short_wave_radiation_flux_surface
Vegetation
Vertical_speed_shear
Visibility
Volumetric_soil_moisture_frozen_+_liquid
Water_condensate_flux_convergence_vertical_int
Water_condensate_flux_convergence_vertical_int_layer_between_two_isobaric
Water_condensate_meridional_flux_vertical_int
Water_condensate_meridional_flux_vertical_int_layer_between_two_isobaric
Water_condensate_zonal_flux_vertical_int
Water_condensate_zonal_flux_vertical_int_layer_between_two_isobaric
Water_vapor_flux_convergence_vertical_int
Water_vapor_flux_convergence_vertical_int_layer_between_two_isobaric
Water_vapor_meridional_flux_vertical_int
Water_vapor_meridional_flux_vertical_int_layer_between_two_isobaric
Water_vapor_zonal_flux_vertical_int
Water_vapor_zonal_flux_vertical_int_layer_between_two_isobaric
u-component_of_storm_motion
u_wind
u_wind_height_above_ground
u_wind_hybrid
u_wind_layer_between_two_pressure_difference_from_ground
u_wind_maximum_wind
u_wind_tropopause
v-component_of_storm_motion
v_wind
v_wind_height_above_ground
v_wind_hybrid
v_wind_layer_between_two_pressure_difference_from_ground
v_wind_maximum_wind
v_wind_tropopause
water_condensate_added_by_precip_assimilaition
water_condensate_added_by_precip_assimilaition_layer_between_two_isobaric
water_vapor_added_by_precip_assimilation
water_vapor_added_by_precip_assimilation_layer_between_two_isobaric