SCI-TECH & AGRI

Influence of orography on tropical rain physics

The size of rain drops influences natural events such as soil erosion and landslides. Larger drops could cause more soil erosion that may serve as triggering factors for landslides. The size of rain drops is influenced by the orography (topographic features of mountains) of places when the rain rate is high, says a study carried out by R. Harikumar, a scientist of the Indian National Centre for Ocean Information Services, Hyderabad. The size of rain drops has a significant effect on soil erosion and landslides. Larger drops could cause more soil erosion that may serve as triggering factors for landslides,

In a paper published in Atmospheric Science Letters, Dr. Harikumar found that rainfall in the Western Ghats region has larger drops compared with those in plain lands when the rain rate is high.

The study was carried out by comparing the rain drop size distribution characteristics at coastal and high altitude tropical stations. Rain data were collected from Kochi, Sriharikota, Munnar and Thiruvananthapuram.

Rainfall at Munnar consists of less number of bigger drops than in Kochi, Sriharikota, and even than Thiruvananthapuram. The rain in the Ghat region was dominated by bigger drops, which could account for more incidents of soil erosion, the paper concluded.

The drop size distribution characteristics at Munnar were very different from other stations. The only difference that Munnar possessed when compared to other stations was that, topographically, it was a hill-station situated on the Indian Western Ghats, it said.

The rain in Munnar was found to be made up of fewer but larger drops compared with any other stations in the plains, especially when it rained heavily. Even when it rained heavily in Kochi and SHAR, it is made up of more number of smaller drops compared to Thiruvananthapuram. Such a difference for Thiruvananthapuram also is attributed to the difference in orography at Thiruvananthapuram compared to Kochi and SHAR, the paper concluded.

The rain physics at Thiruvananthapuram and Munnar were comparable. Thiruvananthapuram has an orographic similarity with Munnar as it closer to the foothills. Kochi is quite far from the foot hills of the Western Ghats, and hence, orographuically, so different from Thiruvananthapuram.

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