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This is the second of three very dense lessons on the fundamentals of solar energy. Keep it up! The lessons will lighten up a bit as we transition past these core materials.
The Sun provides us with shortwave band light at the Earth's surface, and the Earth emits longwave band light up toward the sky; but what is the role of the Sky/Atmosphere in the energy balance on Earth, and how does the atmosphere affect the bands of light that we collect and find useful at the Earth's surface? In solar energy conversion systems, engineers and design specialists apply meteorological information, particularly shortwave band irradiation (from the Sun) to inform project development and design, and also to inform daily performance of installed systems. To a lesser extent (for some radiative thermal estimations), longwave band irradiation from the Earth and atmosphere is used, but the main driver for our SECSs is the shortwave band.
Applied solar energy workers need to use the same science as those working in the field of Meteorology. The shortwave band of light can be collected via ground detectors (pyranometers/pyrheliometers) or from satellites (GOES East, GOES West) to probe and diagnose the behavior of light interacting with the atmosphere and the surfaces of Earth over time. Satellites in orbit have instruments called radiometers to detect and measure the intensity (brightness) of the light scattered back to the satellite. Satellite images of visible light display the shading from clouds, the cloudiness of the Earth's surface, and features such as smoke emerging from large forest fires or volcanoes spewing ash. The signal is a measurement of electromagnetic radiation, both the intensity of the light from the Sun, and the ability of the particles or surfaces to reflect that light back up to the radiometer. Think about what determines the brightness of the light that reflects (is "back-scattered") up to the satellite.
We will start with the concept of electromagnetic radiation, including some important bands of electromagnetic radiation invisible to the human eye. We will also point out ways that a meteorologist and climatologist collect and interpret satellite or radar imagery derived from electromagnetic radiation.
As a preview to Lesson 3, please review the learning objectives on the next page to get an initial sense of the overarching goals that encompass this stage in your forecasting apprenticeship.