Hydrometeor loading is the induced drag effects on the atmosphere from a falling

hydrometeor In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

. When falling at

terminal velocity Terminal velocity is the maximum velocity (speed) attainable by an object as it falls through a fluid (air is the most common example). It occurs when the sum of the drag force (''Fd'') and the buoyancy is equal to the downward force of gravit ...

, the value of this drag is equal to ''gr_h'', where ''g'' is the acceleration due to gravity and ''r_h'' is the

mixing ratio In chemistry and physics, the dimensionless mixing ratio is the abundance of one component of a mixture relative to that of all other components. The term can refer either to mole ratio (see concentration) or mass ratio (see stoichiometry). In at ...

of the hydrometeors. Hydrometeor loading has a net-negative effect on the atmospheric

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...

equations. As the hydrometeor falls toward the surface, the surrounding air provides resistance against the acceleration due to gravity, and the air in the vicinity of the hydrometeor becomes

denser Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek language, Greek letter Rho (letter), rho), although the Latin letter ''D'' ca ...

. The increased weight of the atmosphere can support a present

downdraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...

or even cause a downdraft to occur. Hydrometeor loading can also lead to increased high pressure inside of a

mesohigh A mesohigh (sometimes called a "bubble high") is a mesoscale high-pressure area that forms beneath thunderstorms. While not always the case, it is usually associated with a mesoscale convective system. In the early stages of research on the subject ...

in a thunderstorm.

References

Fluid dynamics Precipitation {{climate-stub