There is a saying in meteorological proverbs that "snow hits mountains and frost hits depressions". Try to describe its principle and matters needing attention in agricultural layout.

The principle of "snow hits mountains and frost hits depressions": precipitation appears in the form of rain or snow, depending on whether the atmospheric temperature is above 0 degrees or below 0 degrees. When the temperature on the ground and in the sky is below 0 degrees, snow falls; Above 0 degrees, it is raining. Because the temperature in the mountainous area is much lower than that in the plain, there is always more snow on the top of the mountain than in the plain. The phenomenon of "first frost" appears because at night, there is no sunlight radiation, the temperature drops, and the air layer near the ground cools down first because of the continuous loss of heat in low-lying terrain. Because of the high density of cold air, it flows along the slope to the bottom of the depression and basin, just like the principle of "water flows downwards", so there will always be a lot of cold air accumulated in the depression and basin at night, and frost will occur when the temperature of the depression is lower than that of the slope and flat land.

Based on this meteorological phenomenon, we should pay attention to the distribution of vertical planting varieties in mountainous areas and choose to plant frost-resistant crops in potholes. If frost occurs in spring and autumn, we can use "smoke to drive frost" to disperse frost haze by using the temperature and smoke generated by burning straw or firewood to prevent crops from freezing damage.