Final answer:
The western part of Nepal receives rainfall in winter season due to the influence of the westerly winds. These winds blow from the Mediterranean Sea and bring moisture to the western region.
Step-by-step explanation:
Nepal's unique topography, characterized by the towering Himalayas and the vast Terai plains, plays a significant role in shaping its diverse climatic patterns. During the winter season, while most of Nepal experiences dry conditions, the western region receives considerable rainfall, a phenomenon attributed to the influence of westerly winds.
These westerly winds originate from the Mediterranean Sea and the Black Sea, carrying moisture across the Middle East and into the Indian subcontinent. As they approach Nepal, these winds encounter the towering peaks of the Himalayas. These mountains act as a barrier, forcing the air to rise and cool down, leading to condensation and the formation of clouds.
Since the westerly winds arrive from the west, the western region of Nepal bears the brunt of this precipitation, resulting in significantly higher winter rainfall compared to the eastern parts of the country. The eastern regions, sheltered by the mountains, receive minimal rainfall during this period due to the rain shadow effect.
In summary, the unique interplay between westerly winds and Nepal's topography is responsible for the winter rainfall pattern, with the western region receiving ample precipitation while the eastern parts remain relatively dry.