In this document
You'll learn what parameters, sources, and units are covered in the Solargis Forecast data specification table, the forecast model details (Solargis CMV model plus HRRR, ICON, ICON EU, IFS, IFS Ensemble, and GFS NWP models with their coverage, resolution, and update rates), and a technical comparison across the Forecast Basic, Professional, Enterprise, Historical Period, and Portfolio Aggregation tiers (geographical coverage, temporal resolution/coverage, and data update rates).
Forecast data parameter specifications
The following table details all parameters available in Solargis Forecast services. It specifies the units and source of each parameter.
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Parameter | API parameter | Unit | Type | Source | Forecast Basic | Forecast Professional/ Enterprise | Forecast: Historical Period | Forecast: Portfolio Aggregation |
Global Horizontal Irradiation | GHI | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
Direct Normal Irradiation | DNI | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
Diffuse Horizontal Irradiation | DIF | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
Global Tilted Irradiation for fixed-tilt PV modules * | GTI | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
Global Tilted Irradiation for PV modules on trackers * | GTI | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
GHI high estimate (10 % probability of exceedance) | GHI_UNC_HIGH | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
GHI low estimate (90 % probability of exceedance) | GHI_UNC_LOW | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
GTI high estimate (10 % probability of exceedance) | GTI_UNC_HIGH | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
GTI low estimate (90 % probability of exceedance) | GTI_UNC_LOW | kWh/m2, Wh/m2, W/m2 | Solar | Solargis CMV, NWP | ||||
Cloud identification quality flag | CI_FLAG | - | Solar | Solargis | ||||
Sun Altitude (Elevation) Angle | SUN_ELEVATION | ° | Solar | Solargis | ||||
Sun Azimuth Angle | SUN_AZIMUTH | ° | Solar | Solargis | ||||
Clearness index | KT | - | Solar | Solargis CMV | ||||
Incidence angle of direct irradiance * | PANEL_INC | ° | PV | Solargis | ||||
Photovoltaic Output for fixed-tilt PV modules * | PVOUT | kW, kWh | PV | Solargis CMV, NWP | ||||
Photovoltaic Output for PV modules on trackers * | PVOUT | kW, kWh | PV | Solargis CMV, NWP | ||||
PVOUT high estimate (10 % probability of exceedance) * | PVOUT_UNC_HIGH | kW, kWh | PV | Solargis CMV, NWP | ||||
PVOUT low estimate (90 % probability of exceedance) * | PVOUT_UNC_LOW | kW, kWh | PV | Solargis CMV, NWP | ||||
PV module temperature * | TMOD | °C | PV | Solargis | ||||
Tilt of inclined surface * | PANEL_TILT | ° | PV | Solargis | ||||
Azimuth of inclined surface * | PANEL_AZIMUTH | ° | PV | Solargis | ||||
Air Temperature at 2 meters | TEMP | °C | Climate | NWP | ||||
Wet Bulb Temperature | WBT | °C | Climate | NWP | ||||
Dew Point Temperature | TD | °C | Climate | NWP | ||||
Wind Speed | WS | m/s | Climate | NWP | ||||
Wind Direction | WD | ° | Climate | NWP | ||||
Wind Gust | WG | m/s | Climate | NWP | ||||
Wind speed at 100 meters | WS100 | m/s | Climate | NWP | ||||
Wind direction at 100 meters | WD100 | ° | Climate | NWP | ||||
Atmospheric Pressure | AP | hPa | Climate | NWP | ||||
Relative Humidity | RH | % | Climate | NWP | ||||
Precipitable Water | PWAT | kg/m2 | Climate | NWP | ||||
Precipitation Rate | PREC | mm/h | Climate | NWP | ||||
Water equivalent of accumulated snow depth | SDWE | kg/m2 | Climate | NWP | ||||
Water equivalent of fresh snowfall rate | SFWE | kg/m2/hour | Climate | NWP | ||||
Potential hail risk with hail size ≥ 1 inch (~2.5 cm) within 50 km radius** | HAILRISK25MM | % | Climate | HRRR | ||||
Potential hail risk with hail size ≥ 1.5 inch (~3.8 cm) within 50 km radius** | HAILRISK38MM | % | Climate | HRRR | ||||
Potential hail risk with hail size ≥ 2 inch (~5 cm) within 50 km radius** | HAILRISK50MM | % | Climate | HRRR |
** US CONUS territory only
* This parameter needs a PV system defined in the request, at least in a minimal setup as follows:
<pv:system installedPower="1">
<pv:module type="CSI"/>
<pv:inverter/>
<pv:losses/>
</pv:system>Forecast model details
The spatial resolution and update rate of Solargis Forecast for a particular location and time horizon depends on the forecast model used. Solargis Forecast uses several forecasting models – our proprietary Cloud Motion Vector (CMV) model, and four different Numerical Weather Prediction (NWP) models. These models are summarized in the table below.
As a general statement, nowcasts and short-term forecasts for solar and PV parameters are derived from the Solargis CMV model, with sub-hourly update rates, and ~4 km spatial resolution. Forecasts for meteorological parameters for any time horizon, solar and PV parameters beyond approximately the next 3 hours are derived from a blend of NWP models, with an update rate of 6 hours, and at least ~13 km spatial resolution. In the continental USA, the forecast for the next 2 days is available with an hourly update rate and approximately 3 km spatial resolution.
The spatial resolution of the final delivered data (solar and PVOUT parameters) is improved by the Solargis downscaling process using horizon shading. We use the near-global SRTM terrain database, which has a spatial resolution of 90 m (3 arc-seconds). This step is particularly important in areas with complex terrain, where the effects of horizon shading become more noticeable in the data.
Model | Coverage | Temporal coverage up to | Spatial resolution | Update rate |
CMV model by Solargis | Global | Approx. 3 hours | 0.033° (~4 km) | 5 minutes in the contiguous USA 10 minutes in the Americas and East Asia/Pacific 15 minutes in Europe, Africa, and Asia |
HRRR by NOAA | Continental USA (CONUS) | 18 hours (D+0) 48 hours (D+2) every 6 hours | 0.033° by 0.033° (approx. 3.5 × 3.5 km) | 1 hour |
ICON by DWD | Global | 60 hours (D+2) | 0.1 by 0.1° (approx. 11 × 11 km) | 6 hours |
ICON EU by DWD | Europe | 60 hours (D+2) | 0.0625° by 0.0625° (approx. 7 × 7 km) | 6 hours |
IFS by ECMWF | Global | 60 hours (D+2) | 0.1 by 0.1° (approx. 11 × 11 km) | 6 hours |
IFS Ensemble by ECMWF | Global | 60 hours (D+2) | 0.25° by 0.25° (approx. 28 × 28 km) | 6 hours |
GFS by NOAA | Global | 14 days (D+14) | 0.1 by 0.1° (approx. 11 × 11 km) | 6 hours |
Forecast subscriptions - technical details
| Forecast Basic | Forecast Professional | Forecast Enterprise | Forecast: Historical Period | Forecast: Portfolio Aggregation |
Geographical coverage | Land surface and coastal seas between latitudes 60°N to 56°S and between 60°N and 65°N in Scandinavia and America (Figure 1) | ||||
Temporal resolution (time step) | Hourly | Up to 5 minutes | Up to 5 minutes | Up to 5 minutes | Up to 5 minutes |
Temporal coverage for Forecast data | Today to D+7 | Today to D+14 | Today to D+14 | Past two complete calendar years for horizons H+0, H+1, H+2, H+3 D+0, D+1, D+2 | Today to D+14 |
Data update rate for up to approx. 3 hours ahead | Six hours | Up to 5 minutes for PVOUT, GHI, DNI, DIF, GTI (including clear sky and uncertainty variants - Figure 1) Six hours for all other parameters One hour for all other parameters in CONUS | Up to 5 minutes for PVOUT, GHI, DNI, DIF, GTI (including clear sky and uncertainty variants - Figure 1) Six hours for all other parameters One hour for all other parameters in CONUS | n/a | Up to 5 minutes (Figure 1)
|
Data update rate for data beyond approx. 3 hours ahead | Six hours | Six hours One hour in CONUS up to D+2 | Six hours One hour in CONUS up to D+2 | n/a | Six hours |
Figure 1: Geographical coverage of Solargis Forecast data