Monsoon contributes about 72 percent of the total annual rainfall in Bhutan
Monsoon: Measuring 66.7mm, Trongsa received the highest rainfall in the country this month, breaking its record of 47.4mm in 2010 in the same month, records with meteorology division show.
Last year, the dzongkhag received 41.9mm of rain in the same month.
It is considered light, if the rainfall measures between 2mm and 20mm and moderate if its between 20mm and 60mm, it is considered moderate. Heavy rainfall measures between 60mm and 80mm and when it crosses 80mm and above, it’s considered very heavy rainfall.
These series of downpour made June one of the wettest months in Trongsa and caused major landslides in the dzongkhag.
Senior meteorologist Tayba Buddha Tamang said unlike this year, Trongsa experienced both dry and wet spell in the past. But this monsoon, both Trongsa and Gasa have been receiving continuous rainfall and that there are several factors contributing to the precipitation.
Since the installation of meteorology station in Gasa in 2003, the highest amount of rainfall accumulated in 24 hours was recorded 80mm. This month, the highest amount of rainfall in Gasa was 35mm.
“After the start of monsoon, if it rains for few days and then there is a dry spell, there will not be much impact of the rainfall,” he said. “When it rains continuously, the rain loosens the soil which already has high moisture causing disasters like landslides and rise in water level.”
Monsoon usually arrives in the first week of June in Bhutan. This year it arrived on June 6. “This year monsoon was on time,” he said.
Tayba Buddha said some places in the country receive more than 300mm of rainfall in a day. For instance Samtse receives 323mm and Dewathang 391.4mm of rainfall in June. “Compared to these places, the amount of rainfall Trongsa received is less,” he said.
During winter, the westerly wind brings moisture from the Mediterranean and Arabian seas towards the western Himalayas such as Sikkim, Jammu and Kashmir and north of India. “These places normally get snowfall due to western disturbance,” he said. “Bhutan also gets snowfall when the disturbance is strong.’
However, in summer, the wind direction turns from westerly to southwest, called the southwest monsoon. “We get monsoon mostly from Bay of Bengal and Arabian Sea,” he said. Also, since Bhutan is mountainous, it also receives convectional rainfall before monsoon.
Tayba Buddha said the monsoon lasts until August and the season contributes about 72 percent of the total annual rainfall in Bhutan.
By Dechen Tshomo