Heat Index (HI) combines air temperature and relative humidity to determine how hot it actually feels. It has become a matter of great concern in the context of Bangladesh climatology along with most other countries. This paper demonstrates the trend analysis of extreme temperature and relative humidity and assessment of heat index effect on human health by dividing the whole Bangladesh into four regions (South-west region, central region, North-west region, east region). Bangladesh experiences highest value of HI in the month of May-August when it crosses 38˚C. Heat-related illness is already thought to be the leading cause increasing patients especially diarrheal diseases and heat stroke in hospital among meteorological phenomena. This includes classical heat stress in addition to heat-induced episodes of pre-existing illnesses such as respiratory, cardio-vascular, nervous system etc. The trend drawn with the help of average HI anomalies from 1987-2017 has shown tremendous rise in apparent temperature in central and North-west region.
Key words: Heat index, apparent temperature, relative humidity, trend analysis, human health.
The 21st climate scenarios produced by several global climate models anticipate a frequency increase in the duration and intensity of the heat waves (Monteiro et al., 2012). Bangladesh is a country that is seriously threatened by climate change (Huq, 2001), which is expected to bring an increase in frequency and intensity of heat waves in the future (Kirtman et al, 2013). Evidence points to a substantial mortality increase during hot weather, with stronger heat effects found in cities and among the elderly, children and men (Burkart and Endlicher, 2011). In Bangladesh, the ongoing spell of heat wave is one of the longest (24 days at a stretch) in 30 years. The highest temperature so far this year was recorded 41.2˚C in Rajshahi. It is the highest since April 15, 1964, when it was recorded 44.5˚C in Jessore. Heat waves do indeed lead to more deaths in Bangladesh. Few researches have been on Bangladesh climate condition by (BCAS, 1994; BUP, 1994 and Bangladesh Climate Change Country Study Program, 1997) etc. and all have the same view that Bangladesh is one of the foremost countries extremely susceptible to the unpleasant effects of global warming. The average annual temperature of Bangladesh is expected to increase by 1.4 ± 0.6˚C by 2050 (Solomon, 2007). An estimated 1,300 excess deaths occurred annually during extreme summer heat from 1975 to 2004 (Kalkstein et al, 2010) and more than 65,000 people end up in emergency rooms each summer with heat-related illnesses (Hess et al., 2014). Sometimes the mean heat index value ranges from 42° to 59 °C in different parts of the country as result health ailments are reﬂected through dehydration, heatstroke/exhaustion, and aggravation of cardiovascular diseases in elderly people and reduced work capacity and productivity (Elahi, 2016). This article discusses historical trends and future climate projections in day and night-time heat indices for the Bangladesh. The objectives of the study are: i) Trend analysis of extreme temperature and relative humidity of Bangladesh, ii) Assessment of comparative heat index all over the country and iii) Impacts assessment of heat index effect on human health.