Radio propagation that rely on reflection (actually refraction) of radio waves from the ionosphere. The ionosphere is a region of the atmosphere from about that contains layers of charged particles (ions) which can refract a radio wave back toward the Earth. A radio wave directed at an angle into the sky can be reflected back to Earth beyond the horizon by these layers, allowing long distance radio transmission. The F2 layer is the most important ionospheric layer for long-distance, multiple-hop HF propagation, though F1, E, and D-layers also play significant roles. The D-layer, when present during sunlight periods, causes significant amount of
Atmospheric Circulation Reconstructions over the Earth and for teaching. The 20CR dataset has already been utilized in several significant research projects, CLIWOC's efforts culminated in the creation of this historical document, namely "A Dictionary of Nautical Meteorological Terms: CLIWOC Multilingual Dictionary of Meteorological Terms; An English/Spanish/French/Dutch Dictionary of Windforce Terms Used by Mariners from 1750 to 1850". Atmospheric Circulation Reconstructions over the Earth The Atmospheric Circulation Reconstructions over the Earth, ACRE, is an international science project, began in 2008, that recovers historical weather observations to reconstruct past global and local weather patterns and so support meteorological reanalysis. The project aims to collect weather data from the