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Parameters

The parameters are based upon solar radiation derived from satellite observations and meteorological data from assimilation models. The base solar and meteorological parameters are available as climatologically, monthly, annual, and daily time series formats for user selected grids. The base data is available in its original source spatial resolution. This section explains the structure, naming convention, and availability of the specific solar and meteorological parameters that can be accessed through the POWER Data Services . This is intended to be a supplement to POWER Data Access Viewer (DAV) User Guide and the API documentation.

Dictionary

To access the full list of the POWER data parameters available please use the Parameter Dictionary located on the POWER Homepage under the Resources Section.

Parameter Not Selected Parameter Selected
Parameter Not Selected Parameter Selected

Groupings

The groups are dependent on the user community and temporal level selected when using the Data Access Viewer (DAV). This enables parameter recommendations to be tailored to each of the communities: Sustainable Buildings (SB), Agroclimatology (AG), and Renewable Energy (RE). While within each community, parameters are filtered by the temporal availability (Daily, Monthly, or Climatological) allowing users to only select data that is available.

For each User community and temporal level, the parameters available in POWER are 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.

Parameters Limit

There is currently a limit of 20 parameters that can be downloaded at a time using the Data Access Viewer (DAV).

Grouping Closed Grouping Open
Grouping Closed Grouping Open

Availability

All parameters have associated availability with a POWER Community and Temporal level when using the API but if using Data form OPeNDAP or the POWER Data Archive you will have access to the full data catalog in it original units.

API Parameters

To determine availability of a parameter for a specific community and Temporal level please refer to the POWER Parameter Dictionary on the POWER Homepage.

OPeNDAP Parameters

If a parameter can be found on OPeNDAP it is available but unlike the API the units are not converted into user communities units; they are stored in the base units. If you access the data form OPeNDAP you will need to convert the data into the units you require.

Naming Convention

POWER uses a standard naming convention across all the services in the POWER Data Services; this enables users to access data from any of the power services using the same naming convention.

  • Names are typically less than 20 characters
  • Abbreviated words are separated by a _.
  • Grouped parameters lead with the common name (e.g. T2M: T2M_MAX, T2M_MIN, T2M_RANGE)
  • If the parameter's time is not Local Solar Time (LST) it is suffixed to the end of the parameter name (e.g. ALLSKY_SFC_SW_DWN_00_GMT).

Recent Parameter Updates

Change in Minimum Insolution Over Consecutive p-day Period Parameter

There was a change in the consecutive p-day period parameters; we now provide the insolation value not a percentage. The value is the cumulative minimum amount of insolation over the p-days period.

Since we now provide the insolation value, the percentage can be calculated following the example below:

INSOL_CONSEC_07_MIN / INSOL_CONSEC_07 = %

New Parameters Names

Some of the parameter names in your example changed; the definition just to confirm:

  • ALLSKY_TOA_SW_DWN to TOA_SW_DWN: Top-Of-Atmosphere Shortwave Downward Irradiance - The total solar irradiance incident (direct plus diffuse) on a horizontal plane at the top of the atmosphere (extraterrestrial radiation).

  • DNR to ALLSKY_SFC_SW_DNI: The direct solar irradiance incident to a horizontal plane normal (perpendicular) to the direction of the sun's position under all sky conditions.

  • SRF_ALB to ALLSKY_SRF_ALB: The direct solar irradiance incident to a horizontal plane normal (perpendicular) to the direction of the sun's position under all sky conditions.

  • DIFF to ALLSKY_SFC_SW_DIFF: The diffuse (light energy scattered out of the direction of the sun) solar irradiance incident on a horizontal plane at the surface of the earth under all sky conditions.

  • PRECTOT to PRECTOTCORR: Precipitation Corrected - The bias corrected average of total precipitation at the surface of the earth in water mass (includes water content in snow). In V1 you where getting PRECTOTCORR when you request PRECTOT.

  • In the previous API version, that change happened dynamically but, in this version, we are working to enhance traceability between the underlying source data models (to be clear what parameter is being used).

  • KT to ALLSKY_KT: All Sky Insolation Clearness Index - A fraction representing clearness of the atmosphere and the all sky insolation that is transmitted through the atmosphere to strike the surface of the earth divided by the average of top of the atmosphere total solar irradiance incidents.