Long-term changes in climatic variables over the Bharathapuzha river basin, Kerala, India
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ORIGINAL PAPER
Long-term changes in climatic variables over the Bharathapuzha river basin, Kerala, India Jose George 1 & Athira P. 1 Received: 10 December 2019 / Accepted: 3 May 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The current study analyzes the changes in the climate pattern of Bharathapuzha river basin in Kerala, India, which experiences a significant imbalance in water availability since 1990. The analysis of the climatic variables shows that there are three climatic zones existing in the basin. The trend in the historic climatic variables is estimated using the non-parametric Mann-Kendall test and the Sen slope analysis. A discrete wavelet analysis is also performed to separate only the long period component of the signal, and its trend is also studied. A significant decreasing trend is observed in the rainfall. However, a monotonous long-term increasing trend is detected for monthly average temperatures and monthly minimum temperatures. The sequential MannKendall test result shows a significant change in the climatic pattern after 1980. The rainfall effectiveness of the basin is analyzed using indices. A drought analysis is also conducted using Standardized Precipitation Index (SPI) in different time scales since climatic zones 2 and 3 in the catchment are drought-prone areas in recent years. A detailed analysis on the existence of climate change in this region is conducted for the first time. These results can be further used for planning and development of climate change adaptation policies for the basin. Keywords Climate change . Mann-Kendall test . Wavelet analysis . Extreme event indices . Standardized Precipitation Index
1 Introduction The Intergovernmental Panel on Climate Change (IPCC), in its 5th Assessment report (AR5), has stated that it is extremely likely that human influence has been the observed cause of global warming of the Earth’s atmosphere since the midtwentieth century. The “Statement on Climate of India During 2019” released by the Indian Meteorological Department (IMD) reports that the maximum temperature over India has shown an increasing trend of 1.0 °C/100 years during the period 1901–2019 (MoES 2019). In India, there is also a visible shift in the onset of southwest monsoon (Pal and Al-Tabbaa 2009). The monsoon season that used to start at the end of May is now shifted to the second week of June. Furthermore, the break spells during the monsoon season are also increasing, which reduces the number of rainy days. The recent years have seen relatively dry June and July months and
* Athira P. [email protected] 1
Department of Civil Engineering, Indian Institute of Technology Palakkad, Palakkad, Kerala, India
a large amount of rainfall occurs in the month of August which results in large-scale flooding in southwestern parts of the country. In this context, the current study tries to identify the existing trend in climatic variables of the Bharathapuzha river basin in Kerala, India. Detection and quantification of trends in climate variables is
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