How are data accessed/downloaded in POWER?

Solar and meteorological parameters can be accessed in the POWER web site via the Data Access Viewer (DAV) at  https://power.larc.nasa.gov/data-access-viewer/.  When the DAV page opens you may click the “Access Data” box and/or check the “Do not show ..” box to avoid loading the splash Page on subsequent visits. 

• In the DAV page that is now visible, in Section 1 select the User community appropriate for the desired data parameters.
• Choose the appropriate Temporal Average in Section 2.
• Enter the site latitude and longitude in Section 3
• Note that if Climatology time period is selected in Section 2, there is not need to enter a time period in section 4 since by default monthly values are averaged over the climatological time period.
• In Section 5, Select Output File Format.
• In Section 6, the parameters that are available for the Select User community and Temporal period are listed in Parameters Folders. Each folder can be opened by clicking on the intersection of the horizontal and vertical branch associated with each folder. Individual data parameters are selected/deselected by clicking on each parameters or all parameters in a folder can be selected/deselected by clicking on the folder itself.
• Click the “Submit” button in Section 7. The resulting page will provide time series plots of the selected data parameters. To download data in the previously selected format click the appropriate box under the "Output Files".

You may also download all data parameters using API calls described at https://power.larc.nasa.gov/docs/v1/.

What is the spatial resolution of the POWER data?

The POWER solar data were initially produced on a 1° latitude/longitude grid and subsequently re-gridded via data replication to a 0.5° latitude, longitude grid cells. The latitude, longitude value for the cell is at the lower left corner of the cell.

The POWER meteorological data were initially produced on a 1/2° by 2/3° global grid and then bi-linearly interpolated by the POWER project to a global 0.5° grid. The latitude, longitude value for the cell is at the center of the cell.

What is the temporal resolution of the POWER data?

The POWER solar data are initially produced on 3-hourly time increments which are averaged to provide daily values. The daily averaged values are used to calculate climatologically averaged monthly values.

The meteorological data are initially produced on 1-hourly time increments which are averaged to provided daily values. The daily averaged values are used to calculate climatologically averaged monthly values.

Where is this data derived?

The POWER solar data are inferred via radiative transfer models from satellite observations. Solar data are taken from the NASA GEWEX SRB and the FLASHFlux projects. Specific time periods associated with each project are listed in the methodology documentation.

The POWER meteorological data are taken from the most current NASA’s Global Model and Assimilation Office assimilation model. The most current model is given in the methodology documentation.

How do I access a requested file (ASCII, CSV, ICASA, GeoTIFF, NetCDF) from the API?

JSON is the default response for all data requests. Please see the 'outputs' section at the bottom of the JSON response for a link to the requested file.

What are the different ways to access the POWER data?

The POWER data can be downloaded as daily time series files or as climatologically monthly averaged values.

Who do I contact if I have a question?

Inquiries regarding the POWER data can be made at power-project@lists.nasa.gov.

Why is the elevation given for the POWER data different from the surface station values?

The POWER data, including the elevation value, represent average values over 1/2° latitude, longitude grid cells. In complex terrain, such as mountains, the averaged elevation of the grid cell can be substantially different from the local elevation of a local surface site.

Are sunshine data (sunshine hours /day; or percentage insolation) and Solar Radiation Global available in POWER?

Yes. The annual averaged global solar radiation and the monthly averaged daylight hours are available via the POWER Data Access Viewer in the Sustainable Buildings community.

Can one access/download POWER data from multiple locations without entering an individual latitude, longitude coordinate?

Contact the POWER project office at power-project@lists.nasa.gov for help in downloading data files from multiple surface sites.

Does the POWER solar insolation represent net radiation or solar radiation requiring an additional cloud term?

The POWER solar values are the downward solar radiation reaching the earth's surface for all sky conditions. The influence of clouds has been taken into account in computing the solar values. The POWER data does not provide the net radiation defined as difference between the incoming and outgoing radiation.

Are hourly data available?

Hourly data are not available at this time

Do the solar insolation values include cloudiness?

The all sky values do include cloudiness. The clear sky values are determined for various cloud 'free' conditions.

What is the accuracy of the POWER solar and/or meteorology data?

The accuracy of both the solar and meteorology data are evaluated through direct comparisons with surface site observations. Results from the comparisons are documented in the methodology documentation.

Overview of Parameters Available in the POWER Data Portal

The purpose of this document is to provide Users of the POWER data portal a brief reference guide on what and where specific solar and meteorological parameters can be accessed, and is intended to be a supplement to POWER Data Access Viewer (DAV) User Guide. Additionally, API documentation have been developed to facilitate the use of the various download capabilities of the new web portal, and extensive documentation on the source and validation of the various parameters can be found in the online methodology documentation.

On June 13, 2018 a new the NASA data web portal with improved solar and meteorology data and greatly enhanced capabilities to facilitate access to NASA's solar insolation and meteorological data parameters, was inaugurated. The new POWER data portal is designed to accommodate numerous User requests for more options to access and download data in multiple formats; remove several security issues in the old system; and to combine data portals from three separate User communities. In particular, the new POWER home page provides access to data previously available through separate home pages to the SSE-Renewable Energy (SSE), the Sustainable Buildings (SB), and the Agroclimatolgy (AG) communities via a single site. The new POWER data archive offers all parameters on a ½ x ½ degree global grid through a GIS-enabled Data Access Viewer (DAV), ArcGIS Image Services, and an Application Program Interface (API) service that provides data in a number of formats including CSV, ASCII, JSON, ICASA, NetCDF, and geoTIFF. The new POWER data portal provides direct access to NASA's solar insolation and meteorological data parameters customized for application to the Sustainable Buildings (SB), Agroclimatology (AG), and Renewable Energy (SSE) communities.

The solar and meteorological parameters in POWER are organized based upon the three user communities that POWER serves (Table 1); SSE-Renewable Energy (SSE), the Sustainable Buildings (SB), and the Agroclimatolgy (AG) communities. Within each community, parameters can be accessed with a temporal averaging period of Daily, Interannual, or Climatological. The daily time period can be used to download the time series of the daily averaged values of the selected parameters over the selected time period. The interannual time period can be used to download a time series of the monthly averaged value of the selected parameter for each year in a selectable time period. The climatological time period gives the monthly climatological average for each selected parameters over a climatological time period (currently set by default to July 1983 – June 2005).

For each User community and Temporal Averaging period, the parameters available in POWER are organized into parameter groups and presented in a directory tree style with the name of each folder identifying in very generic terms the parameters in each folder. Each folder in the directory structure can be expanded or collapsed by double clicking on the folder name to expose the parameters that can be selected/deselected individually by clicking on the parameter name, or selecting/deselecting all parameters in a folder by single clicking on the folder name. (Note that currently there is a limit of 20-parameters that can be downloaded at a time.)