regenvorming

Regenvorming is the atmospheric process by which water in the vapor phase forms liquid rain drops that fall to the surface. It encompasses cloud formation, microphysical growth of droplets, and the atmospheric conditions that determine how and when rain occurs. Rain forms when airborne moisture becomes saturated and droplets in clouds grow large enough to overcome air resistance and fall.

There are two principal pathways for rain formation. In warm rain systems, temperatures remain above freezing throughout the cloud. Droplets coalesce as they collide within deep, moist clouds, growing into larger drops that eventually become too large to be supported by updrafts and fall as rain. The efficiency of this process depends on cloud depth, updraft strength, and the concentration of cloud condensation nuclei.

In cold rain systems, clouds contain supercooled liquid droplets and ice crystals. The Bergeron–Findeisen process dominates here: ice crystals grow at the expense of surrounding supercooled droplets, becoming large enough to fall as precipitation. If the air near the surface is above freezing, melting can produce rain; if it remains below, snow, sleet, or freezing rain may result.

Other important factors include lifting mechanisms (convection, fronts, orographic lift), atmospheric moisture availability, and the vertical temperature profile. Rain is commonly associated with frontal systems, convective storms, and orographic rain on mountains.

Measurement and prediction rely on rain gauges, weather radar, and satellites, along with numerical weather models. Regenvorming is a key component of the hydrological cycle, influencing weather, agriculture, and water resources.