Mountain Climate Belts Lab: Lapse Rate, Orographic Rain Shadow, Snowline and Treeline

Lapse Rate

The lapse rate is a fundamental concept in atmospheric science that describes how temperature decreases with increasing altitude. In dry air, the standard atmosphere assumes a lapse rate of 6.5°C per kilometer. However, when water vapor is present, it can condense and release latent heat, which can increase the local lapse rate to around 9.8°C per kilometer. This process is crucial for understanding how temperature changes with elevation in mountainous regions.

In the simulation, raising a ridge in a westerly airflow demonstrates this effect: as air rises over the mountain, it cools and eventually condenses, leading to precipitation on the windward side.

Orographic Rain Shadow

An orographic rain shadow is an area downwind of a mountain range that receives less precipitation than areas closer to the mountains. This phenomenon occurs because as air rises over the mountain, it cools and condenses, releasing moisture on the windward side. By the time this air descends on the leeward side, it has lost much of its moisture content, resulting in drier conditions.

In the simulation, you can observe how the leeward side becomes significantly drier compared to the windward side, illustrating the orographic rain shadow effect.

Snowline and Treeline

The snowline is the elevation above which permanent snow accumulates. It varies with latitude, altitude, and local climate conditions but generally occurs at elevations where temperatures remain below freezing for a significant portion of the year. The treeline, on the other hand, marks the upper limit of tree growth due to harsher climatic conditions such as cold temperatures, wind exposure, and shorter growing seasons.

In the simulation, you can adjust the elevation to see how it influences the snowline and treeline, with higher elevations leading to lower temperatures and thus a higher snowline and treeline.

Vegetation Belts

Mountainous regions often exhibit distinct vegetation belts that correspond to changes in temperature, precipitation, and soil conditions. These belts can be observed from the base of the mountain up to the treeline. Below the snowline, you typically find coniferous forests or alpine meadows, while above the treeline, only hardy plants like mosses and lichens can survive due to extreme cold and wind.

The simulation allows you to explore how these vegetation belts change with elevation and airflow patterns, providing a dynamic view of mountain ecosystems.

Frequently asked questions

Try it live

Everything above runs in your browser — open Mountain Climate Belts Lab: Lapse Rate, Orographic Rain Shadow, Snowline and Treeline and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.