Country witnessed higher than normal rainfall this winter seasonInternational scientists have linked aberrant rain patterns with climate change, but Nepal lacks homegrown studies to confirm the cause.
Amid growing scientific evidence of climate change altering rainfall patterns, the country has been experiencing a very active rainfall this winter season, according to the Department of Hydrology and Meteorology.
The department has said that all the weather stations, which regularly keep track of rainfall, have recorded higher than normal rainfall this winter.
The normal rainfall of any place for any particular month is calculated as the average of the total rainfall received during a given month between 1981 and 2010. The rainfall data of the ongoing winter season have shown that most of the stations have crossed the normal rainfall mark.
Except for the weather stations in Dharan and Biratnagar, all other stations have recorded significantly more precipitation than their normal this winter season, which is not over yet.
According to Indira Kadel, a senior divisional meteorologist at the department, some stations have recorded twice the normal rainfall, which is the average of precipitation over 30 years period from 1981 to 2010.
“The winter rainfall has been noticeably active this season. Almost all the stations have recorded more rainfall,” Kadel told the Post. “But this is not something that has happened for the first time in the last few years. For linking it with climate change, we need to analyse its intensity and frequency.”
The amount of rainfall a place receives is called ‘normal’ when the received amount of rain remains somewhere between 90 to 110 percent of the average rainfall.
The internal prediction of the department had also predicted that the winter rainfall would be above the normal this year. While there is still a month left of the winter season, many parts of the country have already witnessed rainfall above the normal range and there are chances of a few more wet spells in the days ahead.
Winter rainfall, which occurs because of the westerly disturbance, contributes nearly 3.5 percent of the country’s annual rainfall. Despite the lower amount of rainfall, winter precipitation is considered valuable for winter crops, especially in high mountains where snow provides much-needed moisture to the crops for a longer period of time.
“Some stations recorded 60 percent of the normal rainfall and a few others recorded as low as 30 percent last winter,” said Kadel, who is the chief of the Climate Analysis Section under the department. “This year, it is above the normal range. But this is not something that has happened for the first time.”
The years 2006 and 2009 were dry years. In those years, even monsoon remained mostly dry across the country. Even this year, when monsoon was expected to be normal, the country’s western and far-western regions received ‘below normal’ rainfall.
Meanwhile, high altitude places in Nepal have also seen a significant rise in maximum temperature than low-lying districts, causing excessive melting of snow in the Himalaya.
Although meteorologists shy away from linking these changes with climate change due to lack of detailed study in the country, the changes in the precipitation pattern are evident which is because of annual variability in rainfall which in turn can be linked with climate change.
“Inter-annual variability or inconsistency has definitely gone up which is because of climate change as suggested by various studies,” said Kadel. “Such unpredictability increases the climate risk and uncertainty about our farming and development planning and increases the cost.”
The uncertain amount of rainfall causes confusion among planners and public from what kind of crops to be cultivated for the season to roofing for houses to development of infrastructure.
“Besides affecting the development planning and general life, unpredictable weather phenomenon also adds to the challenge of forecasting,” said Kadel.