|The southern Appalachians in April show the advance of seasons from flowering spring trees in valleys to the wintery spruce-fir forests of high elevations.|
The forth full episode in the video series that covers all topics in the national AP Environmental Science curriculum is entitled Seasonality and Atmospherics. It opens with a discussion on seasonality and points out that temperate and tropical seasons differ. Moreover, it demonstrates that altitude affects the passage of seasons in the temperate zone, with higher elevations having the advance of spring retarded (see photo above). It relates the occurrence of seasonality to the tilt of the Earth's axis with respect to the sun.
The video then proceeds to describe the physical and chemical nature of the atmosphere and contrasts the early Earth atmosphere with its present condition. The role of photosynthetic organisms in shaping the present atmosphere is emphasized, and the vertical structure of the atmosphere is identified. The video ends with a comparison and contrast of weather and climate.