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Category Archives: Meteorology
Zenith, Azimuth and Elevation Angles
The position of the Sun relative to a point on the ground is an important input needed to model solar air mass and solar system performance. The inputs used to describe solar position include:
- Zenith angle
- Azimuth angle relative to the North point on a compass
- Elevation angle or altitude , where
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Welcome to Sunlight and Weather, a technical introduction to solar irradiance, the Earth’s atmosphere, and the basic principles which define the performance of solar power systems.
Weather data sources are presented that were collated to support wind and solar resource assessment, engineering design, and power system monitoring. Data sources include ground stations, satellite observation networks, reanalysis data, forecasts systems, and aerosol models.
All links and content have been extracted from data source websites to facilitate ease of access to data servers. Please contribute if you find links have changed or data product definitions should be updated.
Aerosols directly and indirectly effect the Earth’s radiation budget and climate. As a direct effect, aerosols absorb and scatter sunlight, affecting the spectral intensity of solar radiation reaching the earth’s surface. As an indirect effect, atmospheric aerosols modify cloud formation processes and how clouds affect the energy budget.
Intro to Aerosol Data
Aerosol data can be obtained from several sources. It is important to point out that aerosol data has many uncertainties. Measuring atmospheric aerosols is a challenge due to the large range in particle size, shape, concentration and composition. No single instrument can measure all the aerosol properties, and detection methods of the smallest sub-3 nm particles are still developing.
Intro to Reanalysis Data
Reanalysis is a scientific method for developing a comprehensive and consistent record of how the weather and climate are changing over time. Reanalysis data relies on the assimalation of sensor data from multiple sources and numerical weather prediction models to produce a continually updated, gridded data set that describes the state of the Earth’s atmosphere at difference points in time and space. Gridded reanalysis data is available from different sources. The different data sources vary with respect to
Weather and atmospheric forecast data can be obtained from the following forecast systems:
Introduction to Satellite Observation Networks
Satellite observation networks provide invaluable data on the climate and the layered atmosphere. Space satellite data is a key input to assess the feasibility and operational integrity of renewable energy power systems.
Ground station sensors for weather and climate observation are listed below. The list is limited to station networks that that provide verification of wind and solar resource data.
The air mass coefficient defines the path length of sunlight through the atmosphere (e.g. the column depth), and is a key input for estimating solar extinction and the irradiance intensity on the Earth’s surface. The challenge in modeling air mass and solar extinction is an atmosphere that is highly variable, exhibiting unique behavior at different altitudes. Atmospheric models seek to overcome some of the errors in the interpolative models of air mass. Specifically, atmospheric models:
Aerosol Optical Depth (AOD) defines the degree to which aerosols prevent the transmission of sunlight by absorption or scattering. AOD is measured using an integrated extinction coefficient over a vertical column of air. The extinction coefficient can be used to analyze solar extinction and the performance of solar power systems as a function of location and time.
Solar data collection, as defined by ISO and WMO standards, is a relatively new activity in Qatar. This article summarizes initiatives underway. In nearly all cases, public access to the solar radiation data is limited since data collection remains immature and unvalidated, or the data is strongly aligned to private commercial interests. Notwithstanding, data collection efforts are making significant progress and are likely to benefit renewable energy strategy development and policy design at the national level.
Air Mass Coefficient
The air mass coefficient defines the path length (or column depth) of sunlight through the atmosphere. The air mass for dry air, wet air and dust are key inputs for estimating solar extinction and the irradiance intensity on the Earth’s surface. The air mass coefficient is a ratio between the path length for a specific zenith angle and the column depth when the zenith angle equals zero.
The Meteosat series of satellites are equatorial geostationary satellites operated for meteorological data collection by EUMETSAT. Meteosat solar data is obtained under the Meteosat First Generation (MFG) and the Meteosat Second Generation (MSG) programs. EUMETSAT is responsible for the launch and operation of the satellites and for delivering satellite data to end-users.
Data for renewable energy resource assessment, particularly solar energy, can be accessed from the EUMETSAT Satellite Application Facility (SAF) for Land Surface Analysis (LSA) located here. This article provides essential reference data for working with Meteosat solar data.