Introduction:
Northern India is characterized by a diverse climate due to its geographical location and the influence of the Himalayas. One of the notable features of this region is the decrease in rainfall from east to west. This phenomenon can be attributed to several factors that affect the distribution of rainfall patterns.

Topography:
The topography of Northern India plays a crucial role in the distribution of rainfall. As we move from east to west, the land gradually transforms from the fertile Gangetic plains to the arid Thar Desert. The altitude also increases towards the west due to the presence of the Aravalli Range and other mountainous regions. This change in topography leads to variations in the availability of moisture and influences the amount of rainfall received.

Monsoon Winds:
The Indian monsoon is a major contributor to the rainfall in Northern India. The monsoon winds blow from the southwest during the summer months, bringing moisture-laden clouds from the Arabian Sea. These winds encounter the Eastern Ghats and the Western Ghats, which act as barriers, causing the clouds to release their moisture. As a result, the eastern parts of Northern India, such as Bihar and West Bengal, receive substantial rainfall.

Rain Shadow Effect:
As the monsoon winds continue their journey towards the western parts of Northern India, they encounter the Himalayas. The Himalayas act as a physical barrier, forcing the moisture-laden clouds to rise. As the clouds ascend, they cool down, and their moisture condenses, resulting in heavy rainfall on the windward side of the mountains. However, on the leeward side (western side), a rain shadow effect occurs. The descending air mass becomes dry and inhibits the formation of clouds, leading to a significant decrease in rainfall. This effect is particularly prominent in regions like Rajasthan and Punjab, which lie in the rain shadow of the Himalayas.

Distance from the Sea:
Another factor contributing to the decrease in rainfall from east to west is the distance from the sea. The eastern parts of Northern India are closer to the Bay of Bengal, which provides a source of moisture for the region. However, as we move westward, the distance from the sea increases, and the availability of moisture decreases. This results in reduced rainfall in the western parts of Northern India.

Conclusion:
The decrease in rainfall from east to west in Northern India can be attributed to the topography, monsoon winds, rain shadow effect, and distance from the sea. Together, these factors create a complex interplay that influences the distribution of rainfall across the region. It is important to understand these factors to comprehend the diverse climate patterns and their impact on various regions in Northern India.