Reasons for the formation of topographic precipitation

The formation of topographic precipitation is due to the blocking effect of topography.

Specific reasons:

When the moist air mass moves forward, it is forced to rise slowly due to terrain obstacles such as mountains, resulting in adiabatic cooling, condensation and formation of clouds. As it continues to rise, the water vapor of the cloud condenses to saturation, forming rainfall, which is called topographic precipitation.

Topographic precipitation mostly falls on windward slopes, and leeward slopes are adiabatic heated due to air sinking, which reduces cloud cover and rainfall, which is called foehn effect.

Typical rain area:

In the world, the wettest place often appears on the windward slope of the mountain, which is called rain slope; The leeward slope has less precipitation and becomes a dry slope or "rain shadow" area.

For example, the mountain slope in Scandinavia, Norway is windward, and the precipitation 1000 ~ 2000mm, while the leeward slope is only 300mm. For another example, the northern, eastern and southern sides of the mountains in Taiwan Province Province, China are windward, with more precipitation, with an annual rainfall of more than 2,000 mm, and the fire in Taipei reaches 8,408 mm, which is the place with the most precipitation in China.

Influence of topographic precipitation:

Vegetation impact:

The contribution of topographic precipitation to topographic region lies in abundant precipitation on windward slope, which provides sufficient water for vegetation growth and often leads to lush vegetation on windward slope. Water resources are abundant, and so are animal resources. For example, in Changbai Mountain area of China, the vegetation and animals on the windward slope are completely different from those on the leeward slope.

Climate impact:

There are also differences in precipitation at different altitudes on windward slopes. There is less precipitation in foothills and hilltops. Due to insufficient airflow uplift at the foot of the mountain, there is less rainfall caused by cloud formation, and the air humidity at the top of the mountain has been greatly reduced, with less clouds and less rain, and the most precipitation is halfway up the mountain. Therefore, the climate changes vertically.

For example, the southern slope of Changbai Mountain in China presents a landscape transition from temperate zone to cold zone from the foot of the mountain to the top of the mountain, which is related to the vertical influence of topographic precipitation.

Weather impact:

The diurnal range and annual range of windward slope are smaller than that of leeward slope due to the wettability of wet airflow. Due to the rainy weather on the windward slope, the atmosphere has a strong weakening effect on solar radiation during the day, and the temperature will not rise excessively. At night, the atmosphere has a strong heat preservation effect on the ground, and the temperature will not drop excessively. The leeward slope is the opposite.