Low-pressure area area of wind divergence aloft occurs ahead of embedded shortwave troughs, which are of smaller wavelength. Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity. Thermal lows form due to localized heating caused by greater sunshine over deserts and other land masses. Since localized areas of warm air are less dense than their surroundings, this warmer air rises, which lowers atmospheric pressure near that portion of the Earth's surface. Large-scale thermal lows over continents help drive monsoon circulations. Low-pressure areas can also
Pressure-sensitive paint error sources by employing a second probe into the paint layer, known as the reference probe. This reference probe is used to ratio out the effects of these errors producing high quality PSP pressure maps at low speeds. Pressure-sensitive paint Pressure-sensitive paint (PSP) is a method for measuring air pressure or local oxygen concentration, usually in aerodynamic settings. PSP is paint-like coating which fluoresces under a specific illumination wavelength in differing intensities depending on the external air pressure being applied locally to its surface. A model surface is painted with the PSP coating with an airbrush or automotive type paint