hectopascales

The hectopascal, abbreviated as hPa, is a unit of pressure. It is equal to 100 pascals. The pascal is the SI derived unit of pressure, defined as one newton per square meter. The hectopascal is commonly used in meteorology to measure atmospheric pressure.

Atmospheric pressure is the force exerted by the weight of air above a given point. Standard atmospheric pressure at sea level is approximately 101,325 pascals, which is equivalent to 1013.25 hectopascals. Weather forecasts and meteorological charts often display pressure readings in hectopascals. For instance, a high-pressure system is typically associated with pressures above 1013.25 hPa, while a low-pressure system is associated with pressures below this value.

The hectopascal is a practical unit for meteorological measurements because it results in values that are more manageable than those expressed purely in pascals. Historically, the millibar (mb) was widely used in meteorology, and one millibar is precisely equal to one hectopascal. This means that pressure readings in millibars are numerically identical to readings in hectopascals. The transition to hectopascals reflects the broader adoption of the International System of Units (SI).