What are the functions of the first and second sentences of this poem, such as Morning Rain and Willow Color? When sending Yuan Er to Anxi

The poet wrote Yu Chao, which is a description of the environment, but it adds a bit of sadness to seeing friends off. "New Willow Color" not only shows the freshness of the natural scenery after the rain, but also implies the season-early spring, and also shows the feelings of reluctance. Here, the poet is not only worried about the life of friends who are far away from home, but also contains a touch of worry, which naturally enters the following, from reality to overall emptiness. Contribute to the following emotional expression.