Nederbörd

Nederbörd is a meteorological term used in Nordic languages to describe any form of water that falls from the atmosphere to the Earth's surface. It includes liquid precipitation such as rain and drizzle, as well as solid precipitation such as snow, sleet, and hail, and can also involve mixed forms like freezing rain.

The formation of Nederbörd depends on cloud physics. In warm clouds, precipitation typically develops by collision-coalescence, where larger droplets grow by merging with smaller ones until they become too heavy to be suspended. In cold clouds, the Bergeron process dominates: ice crystals grow at the expense of surrounding supercooled droplets, potentially producing snow that may melt into rain or refreeze as sleet or hail depending on the atmospheric profile. The resulting type—rain, snow, sleet, hail, or freezing rain—depends on temperature, humidity, and air movement as the droplets fall.

Measurement and reporting of Nederbörd rely on rain gauges and standardized observations. Liquid precipitation is recorded in millimeters of water equivalent. Snow is often measured as depth but is commonly converted to a water equivalent using snow density. Rainfall intensity is expressed in millimeters per hour, and total precipitation over a period is reported as a depth.

Geographic and seasonal variation shape Nederbörd patterns. Tropical regions receive high totals, while temperate and polar regions show pronounced seasonal cycles with rain or snow, influenced by latitude, prevailing winds, and topography. Orographic lift, frontal systems, and climate variability drive regional differences and extremes. Nederbörd is a central element of the water cycle, with important implications for agriculture, water resources, and flood risk.