Meteonorm data and program

Meteonorm

The Meteonorm¹ software (V3.0, 1997; V4.0, 2000; V5.0, 2003; V6.0, June 2007; V6.1, 2009; V7.0, 2012; V7.1 2015; V7.2 2017; V7.3 2019; V8.0 2020; V8.1 2021) provides basically monthly meteorological data for any location on the earth.

It also generates synthetic hourly values from these monthly values, using stochastic models which have been improved in the latest versions.

Data covers useful information for PVsyst:

• Global horizontal irradiance (GHI or GlobHor)
• Diffuse horizontal irradiance (DiffHor)
• Wind speed
• Temperature

In the Meteonorm irradiance dataset, please note that :

• the effect of far shadings from mountains at sunrise and sunset is not included, which means that in mountaneous regions an horizon mask must be further applied in the project area of PVsyst.
• users of the Meteonorm¹ software have the possibility to add a skyline profile before applying the synthetic hourly generation, but it is not recommended to so do. Preferably the horizon mask should be added in PVsyst to ensure a correct transposition of diffuse onto the plane of array.

Details of the method

(from the source of the Meteonorm V8.x Manual (Software))

Ground stations

The Meteonorm database contains a total of 8'325 weather stations. For worldwide applications, severa l different international databases are included :

• Global radiation data was taken from the GEBA Global Energy Balance Archive (WMO World Climate Program - Water) (Gilgen et al., 1998). The data was quality controlled using six separate procedures (checking of physical probability, time series analysis and comparison of cloud data).
• Temperature, humidity, wind data, sunshine duration and days with rain were taken from WMO Climatological Normals 1961–1990 (WMO, 1998). To replace missing data and ensure a homogeneous distribution of weather stations, other databases such as the data summary of international weather stations compiled by the National Climatic Data Center, USA (NCDC, 1995/2002) were added. For some stations in the USA, monthly mean values 1961–1990 of global radiation of the National Renewable Energy Laboratory (NREL) database "The Solar Radiation Data Manual For Buildings" were used.

For version 7.0 six data sources were updated:

• Swiss database (based on Swissmetnet of MeteoSwiss): The main period for radiation was extended to 1986–2005 for radiation and to 2000–2009 for temperature, wind and precipitation.
• Globalsod data (NCDC, 2002): The parameters temperature, wind speed (10 m above ground) and precipitation were processed to 2000–2009 means.
• GEBA: The main period was extended to 1986–2005.
• Turkish State Meteorological Service: 9 stations with global radiation from 2004–2013 were added.
• NREL: Monthly means of selected TMY3 sites (those within the lowest uncertainty class) were added.

The monthly average radiation values were calculated for periods of at least 10 years. Although the 10-year periods differ between the stations, a uniform period was used for each continent. For some stations the data was extended with data from neighboring stations using a differential procedure.

Satellite data

In version 8.1 satellite data is used for radiation interpolation in remote areas (Fig. 3.1.1). Where no radiation measurement is available nearer than 200 km (Europe: 50 km) from the selected location, satellite information is used. If the nearest site is more than 30 km (Europe: 10 km) away, a mixture of ground and satellite information is used.

The method used for processing the satellite images is an approximation of methods like Heliosat II (Lefèvre et al., 2002): The 3 hourly pictures of the visible channel of the 5 geostationary satellites have been used (period 2009-2014). The satellite pictures are processed to daily means of global radiation and summed up to monthly values. These monthly values are interpolated with mean ground measurements (mainly GEBA data). The difference between the ground measurements and satellite information is interpolated spatially with the inverse distance method. This provides a result which includes the values at the ground stations and the variation of the satellite pictures. For MSG area (Europe, Africa, Middle East) data from the period 2008-2021 has been used. For Asia and Americas the period of 2016-2021 All satellite data have been regridded to a resolution of 8 km. In the Meteonorm software: - "Weather Stations" mean the meteorological stations which provide irradiance measurements. - "Weather stations w/o global radiation" are meteorological stations recording several parameters, but for which the irradiance is not measured (7'000 sites). - "Interpolated cities" are a set of some large cities, for which the data have been interpolated. In the "Sites" part, the PVsyst "native" database lists all "Stations" with well-measured irradiation, but allows to choose graphically any place on the earth for getting interpolated values. Although any location is directly available within the program, PVsyst also allows to import files produced by the Meteonorm software (old or new versions). Full documentation about the Software and the theory are available from the web site www.meteonorm.com.

Compared to version 7.1, Version 7.2 includes updated meteorological and turbidity data and additional features

• Database:
  • Update of the time periods for temperature, humidity, precipitation and wind speed: periods 1961–1990 and 2000–2009; for radiation parameters 1981–1990, 1991–2010 and 1996–2015.
  • Update of the satellite database. Satellite maps based on 5 geostationary satellites has been updated and enhanced – especially for areas with high albedo.
  • New turbidity climatology based on Gueymard (2012).
• Models:
  • New models for calculation of one minute radiation data.

Compared to version 7.2, Version 7.3 includes no access to ongoing hourly timeseries and includes detailed urban heat models for Barcelona, Bern, Rome and Vienna

• Database:
  • Update of precipitation and days with precipitation to the period 2001–2015.
  • Update of the solar resources in Brazil.
  • Access to ongoing current time series based on satellite (Europe, Africa, Near East) and Re-Analysis data (ERA-5, rest of the world).
• Models:
  • Detailed model for urban effects based on H2020 climate-fit.city project for Barcelona, Bern, Rome and Vienna (more cities will follow in ongoing patches).
  • New Solis 2017 clear sky model (Ineichen, 2018).

Compared to version 7.3, Version 8 is based on more recent data from the following periods

• 1996–2015: new main period for radiation parameters.
• 2000–2019: new main period for temperature, dew point temperature, wind, precipitation and days with precipitation.
  • This recent time period is denoted in the new Version as “contemporary”. It is still possible to choose a “historic” data period (1981–1990 for radiation and 1961–1990 for temperature).
• Database:
  • Access to ongoing current time series based on satellite worldwide (55°S to 65°N) and Re-Analysis data (ERA-5T) for the rest of the world.
  • New satellite data: Now based on an own, globally homogeneous satellite model (Schmutz et al.,2020), including satellite data for Asia and the Americas.
  • Future data for IPCC Scenarios RCP 2.6,4.5 and 8.5 from 10 global climate models based on CMIP5 are included.
• Models:
  • Detailed model for urban effects based on the H2020 climate-fit.city project. 100 cities in Europe include urban effects for the contemporary climates. Barcelona, Berlin, Bern, Bremen, Prague, Rome and Vienna additionally include urban effects of 2050 for two scenarios.