What does ancient poetry mean (sending Yuaner to Xi 'an)?

About the ancient poem "send Yuan Er An" means:

Just after a shower in the morning, the acropolis felt dust and humidity, the air was fresh and the hotel was greener. Let's have another farewell drink, my friend. You know, it's hard to see old friends outside the Buddhist paradise.

Original: Weicheng is rainy and dusty, and the guest house is green and willow. Sincerely advise friends to drink a glass of wine, and it is difficult to meet their relatives when they go out to the sun.

Precautions:

(1) Yuan Er: Yuan, who ranks second, is a friend of the author. Dispatch: Send a special envoy. Anxi: refers to Anxi, the capital of the Tang Dynasty, near Kuqa in Xinjiang today.

⑵ Weicheng: Xianyang City in Qin Dynasty, Weicheng City in Han Dynasty, northwest of Chang 'an, and north bank of Weishui. Yu Chao: It rained this morning.

(3) Guest House: Hotel.

⑷ Yangguan: Located in the southwest of Dunhuang County, Gansu Province, it is the main road leading to the western regions in ancient times.

Creation background: This poem was written by Wang Wei when he sent his friends to the northwest frontier. The title of the poem is also called "Farewell", which was later composed by musicians and named "Three Layers in Yangguan", also known as "Weicheng Qu". About before the Anshi Rebellion. Anxi, the abbreviation of Anxi Duhu, was established by the central government of the Tang Dynasty to govern the western regions, located in Qiuci City (now Kuqa, Xinjiang). The friend named Yuan went to Anxi on the orders of the imperial court. In the Tang Dynasty, most people who traveled westward from Chang 'an saw them off in Weicheng. Weicheng is the old city of Xianyang, Qin Dou, in the northwest of Chang 'an, on the north bank of Weishui.