Precipitation
Precipitation is water released from clouds that falls to Earth as rain, snow, sleet, hail, or other frozen or liquid particles.
Cloud condensation nuclei: Tiny airborne particles on which water vapor condenses to form cloud droplets. They provide surfaces for cloud droplets to form, an early step toward many forms of precipitation.
Atmospheric water vapor: Water in gaseous form present in Earth's atmosphere. It supplies the moisture that can condense, freeze, and eventually fall as precipitation.
Weather forecasting: The prediction of future atmospheric conditions from observations and models. Forecasts estimate when, where, and in what form precipitation will occur.
Evaporation: The change of a liquid into vapor at its surface. Evaporation moves water from Earth's surface into the atmosphere, opposite the downward delivery by precipitation.
Collision-coalescence process: A warm-cloud process in which droplets collide and merge into larger drops. It produces raindrops in clouds whose temperatures remain above freezing.
Condensation: The change of a substance from gas to liquid. Cloud droplets form when atmospheric water vapor condenses.
Hydrology: The study of water's movement, distribution, and properties on Earth and in the atmosphere. Precipitation supplies water to rivers, lakes, soils, and aquifers.
Deposition (phase transition): The direct change of a gas into a solid without passing through a liquid state. Ice crystals can form by deposition, but deposition itself is not falling precipitation.
Bergeron process: An ice-cloud growth process in which ice crystals grow at the expense of supercooled water droplets. It helps form snow and can generate rain after ice melts while falling.
Cloud: A visible mass of suspended water droplets, ice crystals, or both in the atmosphere. Precipitation usually develops from particles inside clouds.