There has been a marked change in the trend of rainfall in the country over the last 15 months, compared to the last 30 years, say meteorologists.
There was no prolonged spell of scorching heat this summer. Instead, there have been dark clouds and incessant rain.
There were heavy rains in Sylhet, Netrokona and Sunamganj districts during the pre-rainy season in March-April in 2017, but not in the corresponding period this year, said executive engineer of the Flood Forecasting and Warning Centre (FFWC) Md Arifuzzaman Bhuiyan.
Analysing data of the last 15 years reveals the pre-monsoon to be a bit different this year, he said. “Global climate change could be the reason for this change.”
He said it is not certain as yet whether this change is a temporary or a permanent effect of global climate.
The pattern of weather of the Pacific Ocean affects this region, Arifuzzaman said. “This is why El Nino during 2013, 2014 and 2015 brought severe heat spell to this region. But it has been raining a lot during March, April and May since 2016. This is due to La Nina.”
Mentioning that monsoon has spread over the country since 1 June, Arifuzzaman said it would rain a lot if the monsoon spread over India. This might cause floods in Bangladesh in the later part of June.
The Bangladesh Meteorological Department (BMD) said it rained 152 per cent more than normal in the haor and low-lying areas of the country in March 2017.
The rains destroyed crops worth Tk 7.20 billion, said the agricultural extension department.
The trend continued in April last year. That month saw 106.2 per cent more rain than normal.
The trend is changing not for rain only. The trajectory of the nor’wester has also changed this year, meteorologists say.
Traditionally, nor’westers blow over the Rajshahi, Bogura, Pabna, Sirajganj, Tangail, Mymensingh and Sylhet districts from March to May. But this year, the storm has changed its route towards Dhaka district, which could be a reason of abnormal rains in and around the district, they say.
The meteorological department of India has already forecasted heavy rain in Assam, Meghalaya, Nagaland, Monipur, Tripura, Mizoram, Bengal and Sikkim states in the first week of June.
Meteorologist Bazlur Rashid does not consider this trend abnormal.
It rained less than normal in May 2017. But the amount of rainfall in May this year crossed the normal limit. That means this is normal that one year experiences heavy rainfall and another year less, he said.
Sometimes, there can be heavy rainfall within a short span of time as happened on 22 August 2017. Meteorologists recorded 126mm rain on that day.
If this happens for several years at a stretch, only then we can say that this is the effect of global climate change.
*This piece, originally written in Bengali, has been rewritten in English by Shameem Reza