The atmospheric pressure at that place and at that time.
Downforce
The force put on a given area by the weight of the air above it is called atmospheric pressure.
Downforce
Atmospheric pressure
The force that air exerts on a given area is called air pressure. Air pressure is the result of the weight of the air above the given area pressing down on it. This pressure can vary depending on altitude, weather conditions, and temperature.
What do you mean "... based on"? The athmosperic pressure is "weight of air" and it can be measured. Strikly speaking: "force per unit area exerted against a surface by the weight of air above that surface at any given point" (wikipedia) Ap could be given in force/area units for example lb/sq ft, kg/sq meter etc.
Yes, pressure is the force per unit area exerted by the weight of the atmosphere above a point on the Earth's surface. This pressure decreases with increasing altitude due to the decreasing weight of the air column above.
Air pressure results from the weight of the air molecules above a given area pressing down. This pressure pushes on surfaces in all directions, exerting a force perpendicular to the surface. The force increases with greater air density and higher elevation.
The amount of force that air is placing on the Earth is called atmospheric pressure. It is the force per unit area exerted by the weight of the air above that particular area.
We know that force acting perpendicularly on an area is thrust & thrust acting on an unit area is called pressure. Pressure exerted by wind or air hasn't been classified individually,rather we all together say it atmospheric pressure. And it is nearly 100000 Pa. so we may say it as atmospheric pressure. -----Akashraj Ghosh, Kharagpur
We measure this force using a barometer. Because there are different kinds of barometers, there are also different unit of measurement for this force. A mercury barometer measures in inches of mercury (in Hg), the english (non-metric) system uses pounds per square inch (PSI), and the pascal (Pa) is the standard in the metric system. In weather terminology, the bar and millibar indicate pressure readings.
The force exerted per unit area by air particles is known as air pressure. It is caused by the constant collisions of air molecules with surfaces and is typically measured in units like pascals (Pa) or millibars (mb). The weight of the air above a given area also contributes to air pressure.