In recent days, North India has witnessed an unexpected surge in rainfall, bringing relief to a region that was previously grappling with a rainfall deficit. This sudden change in weather patterns has sparked curiosity among many, prompting us to delve deeper into the factors behind this phenomenon. In this article, we will explore the causes of the sudden surge of rainfall, shedding light on the interaction between western disturbances and the monsoon trough. Additionally, we will discuss the impact of climate change on the monsoon and the unique vulnerabilities of hilly areas in relation to heavy rainfall and landslides.
The Role of Western Disturbances and Monsoon Troughs:
The surge in rainfall can be attributed to the convergence of two key atmospheric phenomena: western disturbances and the monsoon trough. Western disturbances, originating from the Mediterranean or Central Asia, carry low-pressure air pockets that affect the western Himalayas, resulting in rainfall. On the other hand, the monsoon trough acts as a convergence point for moisture-laden air masses from different directions. This convergence leads to the formation of dense vertical clouds, known as cumulonimbus, which bring heavy rainfall and thunderstorms.
Understanding the Temperature Contrast: While western disturbances are commonly observed during the winter, they can occur throughout the year. In contrast, the monsoon trough, crucial for monsoon rains, forms when the land heats up more rapidly than the surrounding ocean. This temperature difference creates low-pressure areas, triggering wind flows that contribute to the monsoon rainfall. This explains why the surge in rainfall is specific to the monsoon season.
Insights from the India Meteorological Department (IMD): According to the IMD, the recent intense rainfall in North India can be attributed to the interaction between a western disturbance and the monsoon trough. This interaction has not only covered the rainfall deficit experienced earlier but also holds the promise of good rainfall in the upcoming weeks. IMD Director General Mrutyunjay Mohapatra states that the heavy downpour will gradually subside from Tuesday, providing much-needed respite.
Regional Disparities and Climate Change Impacts: While North India has experienced a significant surplus in rainfall, other regions have faced different circumstances. Central India has observed a slight excess in rainfall, while peninsular India and east/northeast India continue to face a rainfall deficit. Former Secretary of the Ministry of Earth Sciences, Madhavan Rajeevan, highlights the influence of climate change on monsoon patterns. He notes that shorter, yet intense, rainfall events are becoming more prevalent, emphasizing the need to improve forewarning systems.
The Vulnerability of Hilly Areas to Heavy Rainfall: The Indian Institute of Tropical Meteorology’s climate scientist, Roxy Mathew Koll, emphasizes the susceptibility of hilly areas, such as the Himalayan foothills and the Western Ghats, to heavy rainfall and landslides. Global warming has increased moisture levels, which are intercepted and lifted by the hills in a phenomenon known as orographic lifting. This process eventually leads to heavy showers and increased landslide risks.
The sudden surge of rainfall in North India can be attributed to the active interaction between western disturbances and the monsoon trough. This convergence of atmospheric factors has helped alleviate the earlier rainfall deficit. However, regional disparities persist, emphasizing the complex nature of the monsoon. Furthermore, the vulnerability of hilly regions to heavy rainfall and landslides highlights the impacts of climate change on local weather patterns. By understanding these factors, we can better prepare for and mitigate the challenges posed by extreme weather events in the future.