The trophosphere, often referred to in the context of Earth's atmosphere, is the lowest layer of the atmosphere where weather events occur and where most of the Earth's air mass is concentrated. It extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on geographical location and weather conditions. This layer is characterized by a decrease in temperature with altitude and contains the majority of the atmosphere's water vapor, making it crucial for climate and weather patterns.