altitude
Quick Summary
Altitude refers to the vertical distance of something above a reference point, most commonly sea level. It is a linear measurement that indicates how high an object is.1
Types of Altitude Measurement
- Elevation: This term is often used interchangeably with altitude, especially when referring to height on land above sea level.1
- Absolute Altitude: This specifically measures the vertical distance between an aircraft and the surface directly below it.2
- Pressure Altimeter: This instrument approximates altitude above sea level by measuring atmospheric pressure, which decreases linearly with height.3
- Radio Altimeter: This type measures the absolute altitude by calculating the time it takes for a radio wave to travel to the ground and back.3
Instruments like the altimeter are used to measure these vertical distances.3
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- climateVariation with height
There are two main levels where the atmosphere is heated—namely, at Earth’s surface and at the top of the ozone layer (about 50 km, or 30 miles, up) in the stratosphere. Radiation balance shows a net gain at these levels in most cases. Prevailing…
Read MoreThere are two main levels where the atmosphere is heated—namely, at Earth’s surface and at the top of the ozone layer (about 50 km, or 30 miles, up) in the stratosphere. Radiation balance shows a net gain at these levels in most cases. Prevailing…
Read More - climateRelation between temperature and humidity
…of the boiling point with altitude can be calculated. For example, the saturation vapour pressure at 40 °C (104 °F) is 74 mb (0.07 standard atmosphere), and the standard atmospheric pressure near 18,000 metres (59,000 feet) above sea level is also 74 mb; thus, it is where water boils at…
Read More…of the boiling point with altitude can be calculated. For example, the saturation vapour pressure at 40 °C (104 °F) is 74 mb (0.07 standard atmosphere), and the standard atmospheric pressure near 18,000 metres (59,000 feet) above sea level is also 74 mb; thus, it is where water boils at…
Read More - climateAverage relative humidity
Humidity also varies regularly with altitude. On the average, fully half the water in the atmosphere lies below 0.25 km (about 0.2 mile), and satellite observations over the United States in April revealed 1 mm (0.04 inch) or less of water in all the air above 6 km (4 miles).…
Read MoreHumidity also varies regularly with altitude. On the average, fully half the water in the atmosphere lies below 0.25 km (about 0.2 mile), and satellite observations over the United States in April revealed 1 mm (0.04 inch) or less of water in all the air above 6 km (4 miles).…
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bloodProduction of red blood cells (erythropoiesis)…persons who live at high altitude have higher red cell counts than those who live at sea level. For example, there is a small but significant difference between average red cell counts of persons living in New York City, at sea level pressure, and persons living in Denver, Colorado, more…
Read More…persons who live at high altitude have higher red cell counts than those who live at sea level. For example, there is a small but significant difference between average red cell counts of persons living in New York City, at sea level pressure, and persons living in Denver, Colorado, more…
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blood diseasePolycythemia…atmospheric pressure, as at high altitudes, or from impaired pulmonary ventilation. The sustained increase in red cells in persons who reside permanently at high altitudes is a direct result of the diminished oxygen pressure in the environment. Chronic pulmonary disease (e.g., emphysema—abnormal distension of the lungs with air) may produce…
Read More…atmospheric pressure, as at high altitudes, or from impaired pulmonary ventilation. The sustained increase in red cells in persons who reside permanently at high altitudes is a direct result of the diminished oxygen pressure in the environment. Chronic pulmonary disease (e.g., emphysema—abnormal distension of the lungs with air) may produce…
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respiratory systemThe gases in the environment5 kilometres in altitude. At sea level and a barometric pressure of 760 millimetres of mercury, the partial pressure of nitrogen is 79.02 percent of 760 millimetres of mercury, or 600.55 millimetres of mercury; that of oxygen is 159.16 millimetres of mercury; and that of carbon dioxide is…
Read More5 kilometres in altitude. At sea level and a barometric pressure of 760 millimetres of mercury, the partial pressure of nitrogen is 79.02 percent of 760 millimetres of mercury, or 600.55 millimetres of mercury; that of oxygen is 159.16 millimetres of mercury; and that of carbon dioxide is…
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human respiratory systemHigh altitudesAscent from sea level to high altitude has well-known effects upon respiration. The progressive fall in barometric pressure is accompanied by a fall in the partial pressure of oxygen, both in the ambient air and in the alveolar spaces of the
Read MoreAscent from sea level to high altitude has well-known effects upon respiration. The progressive fall in barometric pressure is accompanied by a fall in the partial pressure of oxygen, both in the ambient air and in the alveolar spaces of the
Read More