Five different types of lowered snow line in alpine valleys

The snow line for the same precipitation event in alpine valleys can vary greatly from valley to valley, even when the valleys are close together. Often this is not due to a difference in air mass, but to a different interaction of topography and topography-related meteorological conditions. By knowing the causes of a lowered snow line, we can better understand the differences in snow cover in alpine valleys at the same elevation over short distances or the differences in snow cover between alpine valleys and areas outside the valleys. As different types of lowered snow line respond differently to climate change, we can also understand future changes in snow conditions in alpine valleys. To better understand the process, we observed the temperature conditions during winter precipitation events on the territory of Eastern Julian Alps (Slovenia) over a period of two years, focusing on the height of the zero isotherm. Depending on atmospheric conditions, especially changes in the temperature profile and precipitation intensity during precipitation events, five causes of lowered snow line have been identified. These types can occur individually, but during multi-day snowfall events they occur frequently or in combination.