| Abstrakt: |
Scientific knowledge-based understanding of the local climate, its trend and variability are important for better planning and design of city drainage systems, which are limited in this region. Therefore, this study intended to evaluate variability and trends of climate extremes incorporating daily data from the Chattogram station over 1950-2020 period. The variability of climate from 1950-1989 to 1990-2020 period was analyzed using the observed daily maximum temperature, minimum temperature, and rainfall data. Over the recent period the daily minimum temperature has increased and the median of Tmin for each month has scaled up; the increment ranges from 0.2°C to 1.1 °C (monthly) over 1990-2020 period. The variability of mean daily maximum temperature also demonstrated that the medians have raised over the months, ranging from 0.32°C to 1.32°C in recent years from the historic period. In case of mean daily rainfall, it is seen that mostly, the monsoon season experienced more rainfall in recent years than before, while the pre-monsoon season have lower rainfall than historic period. The mean rainfall anomaly ranges from -2.0 mm/day to 2.87 mm/day for different months. To examine the effects of climate change on the extreme climate indices, 22 extreme climate indices from ETCCDI were computed for 1950-1989 and 1990-2020 periods. Their linear trend analysis demonstrated substantial upward slopes for both maximum and minimum temperature indices, while the rainfall indices showed mild positive slopes in 1990-2020 period. We found highly increasing trend for the warm days and warm night frequencies whereas, the frequency of cold days and cold nights were found significantly decreasing. On the other hand, mild increasing trend in one-day and five-day maximum rainfall were detected. Also, about 6% increment of average annual precipitation from 1950-1989 to 1990-2020 period was observed in Chattogram. This study revealed upward trends for the heavy monsoon rainfall in the recent decades. This increased monsoon rainfall could be on of the driving forces for the increased waterlogging situation in the Chattogram City. To improve the present city drainage condition, vulnerabilities associated with the extreme climate indices need to be considered. [ABSTRACT FROM AUTHOR] |
