Variation in diurnal temperature range is asymmetric over India’s 3 agroclimatic zones with a marked accelerating decrease in the range witnessed over the last 30 years in the north-west, parts of Gangetic plain, north-east, and central India said a new study. This short term decrease in maximum and minimum temperature range is most prominent during monsoon and post-monsoon and stands out despite a long term trend of increasing differences between the two. This accelerating decline in diurnal temperature range owing to faster rise in minimum temperature and decline in solar radiation, as suggested in the study, may put agriculture and health at risk.
Diurnal temperature range (DTR) is an important indicator of climatic change and a critical thermal metric to assess the impact on agriculture and human health. Hence it is extremely important to identify the regions of wide diurnal variation and decreasing DTR and to assess the explicit causes responsible for these phenomena.
A team of researchers and scientists led by Prof. R.K. Mall, including Manisha Chaturvedi, Nidhi Singh, Rajeev Bhatla, RS Singh, Akhilesh Gupta and Dev Niyogi from the Department of Science & Technology-Mahamana Centre of Excellence in Climate Change Research (MCECCR) at Banaras Hindu University traced the long term change (1951- 2016) and change in recent past (1991- 2016) in spatial-temporal and seasonal trend in DTR, maximum (Tmax) and minimum temperature (Tmin) and solar radiation (Srad) in different agro-climatic zones of India.
The researchers found an alarming decline in DTR in the recent 30 year period over three agro-climatic zones of India comprising north-west, parts of Gangetic plain, and central India. At the same time, an overall increasing trend in DTR, maximum and minimum temperature over a long term period was also observed with large diurnal asymmetry in different agro-ecological zones. Importantly, the significant decline in DTR was associated with a large increase in minimum temperature in comparison to maximum temperature. In contrast, the temperature range in the East and West coast as well as in the Southern part of India showed an increase.
Such changes in DTR would lead to an increase in the risks of drought and heat stress, crop failure and an increase in morbidity and mortality rate.
The study supported by the Department of Science and Technology (DST), Government of India, and published in International Journal of Climatology suggested that the persistent atmospheric aerosol loading over Indo-Gangetic Plain might have caused declining solar radiation over the region, leading to rise in minimum temperature thus resulting in declining DTR over these regions. Other important factors such as cloud cover, land use land cover change could also be responsible for decline in DTR. The scientists and researchers have stressed that the results call for a robust policy and stringent mitigation and adaptation strategies to deal with declining DTR in three prominent regions of India.
https://doi.org/10.1002/joc.6978 (International Journal of Climatology).
Figure. Decadal trends of DTR over the different Agro-climatic zones of the India during the period 1951-2016 and 1991-2016.