What kind of scene does the poem appreciation couplet of "A Song of Rain and Snow" depict?

Rain and snow song is one of Yuefu's cross-blowing songs. Cross-blowing lyrics are Yuefu, but the source is Huqu, which is military music. "Rain and snow are separated by a stream, from the army to Longxi." The first pair of couplets broke the topic and explained the time, place and events, creating a specific atmosphere for the following. "Look at the fox tracks around the array and the horseshoes on the side of the mountain." Parallel connected the first couplet, further writing the desolate scene of the frontier fortress. "The cold flag is bad in color and low in drum." The necklace combines the cold, darkness and depression of the border with the depression and dreariness of the foot soldiers with lyrical scenery and blending scenes. "The clouds are long and gloomy and gray." Couplets sum up the whole poem and point out the theme of homesickness. It is precisely because of this theme that the repression of previous poems has also found a foothold. "Melancholy clouds" and "mystery" are not only the reflection of natural scenes, but also the transmission of soldiers' inner feelings.