Kerala is anxiously awaiting the monsoon with the cities and towns alike crying out for the rains to break, bringing a respite to the residents in the State from the scorching temperatures.
The State, the gateway of the monsoon to the country, used to witness the onset of the southwest monsoon by the first of June, which is crucial for lifting the spirit and economy of the country as a whole. However, there are places in the State that record rain throughout the year.
The last 120 years of data available with the India Meteorological Department (IMD) reveal there are rain belts at the downhills of the Western Ghats in Kerala which record close to double the average annual rainfall the State receives in a year.
In Neriamangalam
For instance, Neriamangalam in Ernakulam, which is the ‘gateway’ to the high ranges of Idukki, receives an annual average rainfall of 5,066 mm with rains lashing the village irrespective of all seasons. The village witnesses an average of 166.12 rainfall days, followed by 20.72 heavy rainfall days, 4.73 very heavy rainfall, and 0.6 extreme heavy rainfall days in a year, considering the monsoon data of the last 120 years. On the other hand, the average rainfall in Kerala as a whole is around 2,700 mm.
The rain data for Kuttiyadi in Kozhikode shows the rain belt area receives an average annual rainfall of 4,454 mm, followed by Ponmudi in Thiruvananthapuram, the popular tourist hill station in southern Kerala, with an annual rainfall of 3,952.85 mm. All these stations record rainfall in 12 months of a year, as per the IMD data. There are also several other rain belts in the State like Kanjirappally, Peerumade, Piravom, Vythiri, and so on.
“The main specialty of these stations is that they are situated along the downhill of the Western Ghats or at the halfway height of the Western Ghats,” said P.S. Biju, senior scientist in the IMD.
Latent heat
The rain clouds floating in the atmosphere will be blocked by the mountains, causing the clouds to rise. While rising up, condensation takes place. During condensation, water vapour in clouds becomes liquid, and rainfall occurs. But during condensation, heat will be released, known as latent heat, which will flow into the opposite side of the Western Ghats. This creates hotness there without rainfall, known as rain shadow region, said Mr. Biju.
Chinnar in Idukki, located on the other side of the Western Ghats, is one of the rain shadow places in the State where the annual rainfall is 592.78 mm considering the last 120 years’ data. Also, places like Ayyankunnu in Kannur and Peruvannamuzhi and Thamarassery in Kozhikode, which are yet to be identified as rain belt areas as these places were added into the weather station networks of the IMD after the introduction of automatic weather stations, are also rain belt areas, but for validating this, IMD requires the data of several years.
