There is no significant tele-connection of precipitation with El Niño/Southern Oscillation (ENSO) in Bangladesh, whereas, during monsoon, whole Bangladesh and its western region, including Rajshahi and Khulna divisions, showed significant correlation with the values of Indian Ocean Dipole (IOD), says a research study.
The findings came from a recent research titled ‘A long-term trend in precipitation of different spatial regions of Bangladesh and its tele-connections with El Niño/Southern Oscillation and Indian Ocean Dipole’ had been conducted by a four member team of Researchers of Bangladesh led by Md. Kawser Ahmed who is the founder Chairperson of Department of Oceanography, University of Dhaka. The research has also been awarded UGC Gold Medal.
The research has suggested that the co-occurrence of ENSO (El Niño and La Niña) and IOD events showed severe anomalies in the precipitation, flooding, and drought events in Bangladesh. Apart from ENSO/IOD-precipitation relationship, ENSO effects depicted anomalies.
Researchers, therefore, suggested further investigation to enhance the early warning system for floods and other natural anomalies.
Research has also revealed that the precipitation (annual or monsoon) of whole Bangladesh and almost all of the spatial regions did not show any significant correlation with ENSO events, whereas the average IOD values showed significant correlation only in monsoon precipitation of western region.
The findings of this paper suggested that among all of them, positive IOD-precipitation relationship showed the most significant correlation. As a result, it can be inferred that the tele-connections of IOD with precipitation of Bangladesh are stronger than ENSO. But co-occurrence of El Niño and positive IOD and La Niña and negative IOD may lead to different kinds of anomalies.
There might have some other reasons for the rainfall variations within the country. So, in the context of Bangladesh climate, IOD has the more tele-connection to precipitation than that of ENSO. The research findings indicate that the co-occurrence of ENSO and IOD events may suppress their influence on each other.
“This type of study has been done in some other countries, but not in Bangladesh. This study focuses on the temporal (intra-seasonal and inter- annual) and spatial variability of precipitation in Bangladesh using data sets covering the period 1948-2012 to detect the monotonic trend of precipitation in Bangladesh and magnitude of change,” Md Kawser Ahmed told the New Nation.
“Moreover, the correlation of tele-connection of precipitation variability with both ENSO and IOD events in respect of whole country and its several spatial regions has been investigated on the basis of long time scale. The findings of this study will have great implications for Bangladesh and the Bay of Bengal region countries such as India, Myanmar, Indonesia, Sri Lanka” he said.
Therefore, it can be remarked that exclusively the positive IOD events have a strong influence on monsoon precipitation of whole Bangladesh and its western region, but not on annual precipitation in any of the spatial regions. Despite significant wind anomalies in the Indian Ocean related to IOD events, the monsoon-IOD relationship remains relatively weak.
In this study, the average IOD values showed significant correlation only in monsoon precipitation of western region, whereas the individual positive IODs showed significant correlation with precipitation of whole Bangladesh, its western region, and Rajshahi and Khulna divisions.
According to the Inter-governmental Panel on Climate Change (IPCC), Bangladesh will experience five to six per cent increase in precipitation by 2030 due to climate change.
Some earlier studies have also shown that the amount of precipitation has been increasing during the recent decades with implications for flooding in Bangladesh.
