1 Introduction

Climatic change and its impacts are among the major concerns not only for the scientific community but also for the common man in present times. The changing pattern of precipitation is considered one of the major consequences of climate change. The precipitated water is an important part of the water cycle, which plays a major role in sustaining life along with substantial functions in several other processes as well. In the case of a country such as India, where water availability depends on the seasonal monsoon, precipitation plays a crucial role in every aspect of life. However, the Sixth Assessment Report of the Intergovernmental Panel on Climate Change elaborated that the changing pattern of precipitation in India will have a diversified impact on drinking water, agriculture, hydrology, flooding, droughts, and extreme precipitation events [1], which in turn will shape the socio-economic and other aspects of the country. Indigenous people, farmers, local and marginalized communities, and traditional people will be worst affected by such changes [2]. Therefore, it is pertinent to study the pattern of precipitation as it is one of the important climatic variables to understand the impact of changing climate. There are several studies on the pan-India level to understand the dynamics of precipitation [3,4,5,6,7]. However, to understand the in-depth mechanisms of such changes, region-focused studies are also needed at present. Particularly, regions that are underdeveloped and home to vulnerable groups of the population must be focused on. Madhya Pradesh (MP) is such a region where most of the population, including tribal groups of the indigenous population, is dependent on rainfall-based agriculture and forest products. Even then, only a few studies have been conducted to investigate the changes in rainfall covering the whole of Madhya Pradesh. Among them, one of the studies assessed the variability of rainfall from 1901 to 2002 at the district level in Madhya Pradesh [8]. Another study also analyzed the spatial and temporal variation in rainfall trends from 1901 to 2011 at the district level [9]. Moreover, a similar study has analyzed the characteristics of the extreme rainfall events over central India (Madhya Pradesh, Chattisgarh, and Vidarbha) for the period of 1901–2010 [10]. Other than these, there are a few more studies focused on smaller areas. The trends of rainfall over the Kanha and Satpura Tiger Reserves during 1971–2015 [11], the Narmada river basin from 1901 to 2002 [12], the Ken river basin from 1901 to 2010 [13], the Sindh River basin between 1901 and 2002 [14], the semi-arid Bundelkhand region of Madhya Pradesh from 1951 to 2018 [15], and the Western (Hoshangabad district) and Eastern (Mandla district) Madhya Pradesh from 1971 to 2015 [16] have been investigated using similar statistical methods and data. However, there is a lack of studies to understand the dynamics of rainfall from the perspectives of meteorological subdivisions, i.e., East and West Madhya Pradesh (Fig. 1). Broadly, these two meteorological subdivisions seem to be under the influence of the Bay of Bengal branch and the Arabian Sea branch of the Indian summer monsoon. Any changes in these two branches of the Indian summer monsoon may be reflected in the rainfall pattern in Madhya Pradesh.

Fig. 1
figure 1

Study Area. A Location of Madhya Pradesh with sources of rainfall. AS Branch- Arabian Sea branch of Indian Summer Monsoon, BB Branch- Bay of Bengal branch of Indian Summer Monsoon. Background images are from ESRI online. B Meteorological subdivisions of India with highlighted regions of the study area in red dotted lines: 19-West and 20-East Madhya Pradesh (Original source: Kothawale and Rajeevan, 2017) [17]

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Therefore, the present study aims to explore the long-term as well as the recent trend in rainfall in East and West Madhya Pradesh. This study also assesses the magnitude of any change in rainfall in the region. Furthermore, this study explores the variability of rainfall in May and October to investigate the temporal shift in the monsoon season under the impact of climate change in this region.

2 Study area

Madhya Pradesh, with an area of 308,252 km2, is the second-largest state in India. It is located between 21°17′ N to 26°52′ N and 74°08′ E to 82°49′ E (Fig. 1). Most of the area of Madhya Pradesh is occupied by plateaus such as Malwa, Bundelkhand, Baghelkhand, Rewa-Panna, and the Central highlands. Two mountain ranges, Vindhyachal and Satpura, run parallel in east–west direction, forming the Narmada River valley between them. These two mountain ranges control the rainfall behavior of the Indian Summer monsoon in the region. Broadly, Madhya Pradesh has a subtropical type of climate. The annual rainfall ranges from 800 to 1800 mm. The intensity of rain decreases from the southeast to the northwest in the region. The annual average temperature varies from 22 °C to 25 °C in Madhya Pradesh. The state is drained by several rivers, mainly the Narmada, Tapti, Son, Betwa, Shipra, and Chambal Rivers. As per the Census of India 2011, Madhya Pradesh shares 6% (72.63 million) of the total population of India, out of which 72.37% lives in rural areas and only 27.63% lives in urban areas. The rural population is dependent on agriculture, which majorly relies on seasonal rainfall. Madhya Pradesh has a 21.09% tribal population that is directly dependent on the natural environment for the entirety of their needs.

3 Dataset and methodology

The present study is based on Sub-divisional monthly area-weighted rainfall series prepared and provided by the Indian Institute of Tropical Meteorology (IITM), India. The data is for monthly, seasonal and annual rainfall which lasts from 1871 to 2016. The data are freely available on IITM website (https://www.tropmet.res.in/data/data-archival/rain/iitm-subdivrf.txt), accessed on 05/12/2022. The data has been taken for Eastern and Western Madhya Pradesh. To convert the data into mm, it was divided by 10 as suggested by the IITM. The data are some of the most detailed and reliable since proper care was taken in the preparation of these data by considering homogeneity, missing values, outliers, and assigning the weightage [17]. There are several key references available to understand the process of preparing these data series [6, 17,18,19,20,21]. The data are of particular importance as they are one of the longest data series in monsoon-dominated countries in SE Asia.

The study estimates the variability over the centennial scale from 1871 to 2016 and in the recent 30 years from 1987 to 2016 to know the changes at the long as well as short temporal scales. This study is focused on monsoon rainfall (June–September), annual rainfall, and the month before and after the monsoon season (May and October). The fringe months of summer monsoon- May and October are analyzed to assess any temporal shift in the monsoon season as an impact of climate change or global warming. Spatially, the study area is divided into two parts, Eastern and Western Madhya Pradesh, representing 15 and 22 weather stations, respectively. These two meteorological subdivisions of Madhya Pradesh are part of the rainfall data series given by IITM, Pune, which has provided the data of 5 homogeneous regions and 30 meteorological subdivisions of India [5, 17]. The study used Mann–Kendall non-parametric test to detect any trend in the observed rainfall over the period. The Mann–Kendall test is a reliable and widely used technique to assess the trends in climatic data sets [7, 22,23,24]. The Mann–Kendall test does not need the normal distribution of data, as it overcomes the inconsistencies caused by inhomogeneity in the time series. The test validates the null hypothesis (no trend) against the alternative hypothesis, assuming that there is a trend. Sen’s Slope estimator is used [25] to assess the magnitude of the trend in this study. Many climatological studies have preferred Sen’s Slope over simple linear regression considering its robustness. Details of the process to calculate the Mann–Kendall test and Sen’s Slope estimator can be found in Kumar et al. and references therein [22]. All the tests are carried out using a 95% confidence level for the present study.

4 Results

4.1 Long-term variability (1871–2016)

4.1.1 Eastern Madhya Pradesh

The annual rainfall in East Madhya Pradesh recorded a statistically significant negative trend as the p-value (0.011) is lesser than the alpha value 0.05 calculated by the Mann–Kendall test. Sen’s Slopes estimator showed a decrease of a total of − 164.25 mm at − 1.125 mm y − 1 during the entire observed period. Standard Deviation (SD) and coefficient of variance (CV) stand at 212.71 mm and 0.17 mm, respectively, for the same in Eastern Madhya Pradesh. In the case of monsoon rainfall (JJAS) also, a statistically significant negative trend (p-value 0.003 < alpha 0.05) was recorded in Eastern Madhya Pradesh. The total decrease in monsoon rainfall is observed at − 181.33 mm with − 1.242 mm y − 1. SD and CV are observed as 194.47 mm and 0.18 mm, respectively, for the monsoon rainfall. Rainfall in May and October does not show any trend for the observed period. However, Sen’s Slope estimator assessed a total increase of 1.02 mm (0.007 mm y − 1) and 3.21 mm (0.022 mm y − 1) in the May and October months, respectively. Rainfall during May recorded a CV of 1.13 mm with an SD of 14.00 mm. CV for rainfall in October month is recorded as 1.01 mm, along with an SD of 41.24 mm.

4.1.2 Western Madhya Pradesh

Western Madhya Pradesh did not record any statistically significant trend in any analyzed series of rainfall, i.e., total annual, Monsoon (JJAS), May, and October. However, Sen’s Slope estimator shows changes of 16.93 mm (0.116 mm y − 1), − 13.57 mm (− 0.093 mm y − 1), near zero mm, and 2.77 mm (0.019 mm y − 1) for the total annual, monsoon, and May and October rainfall, respectively. The annual rainfall observed a CV of 0.18 mm and an SD of 176.46 mm during the observed period. During the monsoon, the observed CV and SD are 0.19 mm and 169.76 mm, respectively. The month of May observed a CV of 1.30 mm with an SD of 12.38 mm. The month of October recorded 1.18 mm CV and 32.33 mm SD for the entire period. Table 1 and Fig. 2 show the rainfall variability for long-term observation in the study area.

Table 1 Long-term trend of rainfall in Madhya Pradesh, 1871–2016
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Fig. 2
figure 2

Long-term rainfall variability in Madhya Pradesh (1871–2016). East Madhya Pradesh: A—Annual rainfall, B—Monsoon (JJAS) rainfall, C—May rainfall, D—October rainfall. West Madhya Pradesh: E—Annual rainfall, F—Monsoon (JJAS) rainfall, G—May rainfall, H—October rainfall. The linear trend line shows Sen’s Slope

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4.2 Short-term variability (1987–2016)

4.2.1 Eastern Madhya Pradesh

None of the observed rainfall series (annual, monsoon, May, and October) have recorded a statistically significant trend over the last 30 years in Eastern Madhya Pradesh from 1987 to 2016. However, a change of − 20.61 mm (− 0.687 mm y − 1), − 59.76 mm (− 1.992 mm y − 1), − 1.68 mm (− 0.056 mm y − 1), and 6.27 mm (0.209 mm y − 1) was reflected in the annual total, monsoon, and May and October rainfall, respectively, through Sen’s Slope estimator. The annual total rainfall recorded a CV of 0.19 mm with 228.12 mm SD. The monsoon rainfall observed a CV and SD of 0.21 mm and 217.18 mm, respectively, for the last thirty years. The CV of rainfall during May and October was 0.95 mm and 0.87 mm with SD of 12.50 mm and 33.41 mm, respectively. Table 2 and Fig. 3 show the short-term variability of rainfall in Madhya Pradesh.

Table 2 Short-term trend of rainfall in Madhya Pradesh, 1987–2016
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Fig. 3
figure 3

Short-term rainfall variability in Madhya Pradesh (1987–2016). East Madhya Pradesh: A—Annual rainfall, B—Monsoon (JJAS) rainfall, C—May rainfall, D—October rainfall. West Madhya Pradesh: E—Annual rainfall, F—Monsoon (JJAS) rainfall, G—May rainfall, H—October rainfall. The linear trend line shows Sen’s Slope

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4.2.2 Western Madhya Pradesh

Similar to the eastern part, Western Madhya Pradesh has also not recorded any statistically significant trend in rainfall in annual total, monsoon, October, and May during the last 30 years. The Sen’ Slope indicates a change of 140.37 mm (4.679 mm y − 1), 127.50 mm (4.250 mm y − 1), − 2.19 (− 0.073 mm y1), and − 14.01 (− 0.467 mm y − 1) in annual total, monsoon, and May and October rainfall, respectively, in Western Madhya Pradesh. The annual total rainfall recorded a CV of 0.19 mm with an SD of 175.32 mm. The monsoon rainfall observed a CV and SD of 0.20 mm and 173.12 mm, respectively, for the last thirty years. The CV of rainfall during May and October was 1.49 mm and 0.97 mm, with an SD of 15.73 mm and 26.73 mm, respectively.

5 Discussion

East Madhya Pradesh receives more rainfall than West Madhya Pradesh. However, the rainfall variability is higher in West Madhya Pradesh for all the observed series of rainfall, i.e., total annual, Monsoon, May, and October at long as well as short time scales (Tables 1, 2). The statistically significant decreasing trends of rainfall over the long-term in Eastern Madhya Pradesh observed by this study are confirmed by a previous study indicating the significant decreasing trend in districts of East Madhya Pradesh at Balaghat, Dindori, and Shahdol in annual rainfall, and at Balaghat and Dindhori in monsoon rainfall, from 1901 to 2002 [8]. A similar trend was also confirmed in another study, which showed a significant decrease in the four stations in East Madhya Pradesh, i.e., Balaghat, Katni, Shadol, and Sidhi, during the monsoon season between 1901 and 2011 [9]. The decreasing trend in Eastern Madhya Pradesh was also confirmed by one more study on the Ken River basin, a major part of which lies in Eastern Madhya Pradesh, showing similar statistically significant negative trends in data series of the annual and monsoon periods during 1901–2010 [13]. A study focused on the Narmada River basin also confirmed that the stations located in Western MP (Dhar, East Nimar, Harda, Hosangabad) did not indicate a significant trend, whereas the station located in Eastern MP (Dindori station) indicated a significant negative trend for annual and monsoon rainfall [12]. The negative trends of rainfall in Eastern MP are also similar to the trends in the adjoining state of Chattishgarh in monsoon and annual rainfall [5, 26]. Other states that are under the dominance of the Bay of Bengal branch of the Indian summer monsoon, such as Nagaland, Manipur, Mizoram, Tripura, Assam, and Meghalaya, have also experienced statistically significant decreasing trends over long-term observation (1871–2011) in the monsoon season [27]. Moreover, Orissa also experienced a decreasing trend (insignificant) in annual and monsoon rainfall (1871–2006) [28].The no trend of rainfall in Western Madhya Pradesh is also similar to the result of other studies on western regions of India, such as Vidarbha, Marathwada, East Rajasthan, and Gujarat [27]. The diverse trends of rainfall in East and West Madhya Pradesh over the long-term period may be understood with the help of characteristics of monsoon depressions and cyclones in the Bay of Bengal and the Arabian Sea, as they are one of the main sources of precipitation in India. The observed pattern of a significant decrease in rainfall in Eastern Madhya Pradesh and no trend in Western Madhya Pradesh may be linked with the considerably decreasing frequency of tropical cyclones/monsoon depressions in the Bay of Bengal and no trend in the Arabian Sea during the monsoon season over the long period [29, 30]. The trends in tropical depressions/cyclones may be affected by anthropogenic aerosols and the emission of greenhouse gases. A recent study has quantified the relative role of aerosol and greenhouse gas forcing in tropical cyclone frequency at the global scale, and reported that the impact of the two forcings are almost comparable, but opposite, and may result in the cancellation of their respective effects [31]. A similar study also highlights that anthropogenic aerosols-induced cooling has a role in the reduced genesis of tropical cyclones in the northern hemisphere [32]. The decreasing trend of tropical cyclones over the Bay of Bengal may be attributed to the aerosols-induced cooling effect, which may be a cause of the drying trends of Eastern Madhya Pradesh over the long term. Moreover, a similar study also confirms the role of anthropogenic aerosols in decreasing precipitation trends over the Northern Hemisphere in the last century [33]. In the case of the Arabian Sea, the no-trend in tropical cyclone frequency may be attributed to the combined and opposite impact of aerosol and greenhouse gas forcing [31], resulting in the cancellation of their effects and producing no trends in rainfall in western Madhya Pradesh. On the short temporal scale, a study covering the past 45 years, from 1971 to 2015, has investigated the rainfall trends in Mandla (east Madhya Pradesh) and Hoshangabad (west Madhya Pradesh) and reported no significant trend in monsoon and annual rainfall [16], similar to the results of this study. The no-trends over the short temporal scale may also be attributed to the canceling effect of the two forcings. However, there is a need for studies particularly focused on this region to explore the role of these anthropogenic forcings. The no-trend in rainfall during the months of May and October over long- as well as short-term observation suggests that there is no shift in the duration of the monsoon season in the study area. However, statistical analysis shows that variability during annual and monsoon rainfall has increased in recent times in comparison to long-term variability in the study area (Tables 1, 2).

6 Conclusions

This study analyzed long-term (1871–2016) as well as short-term (1987–2016) variability in rainfall over meteorological subdivisions of East and West Madhya Pradesh. This study found statistically significant negative trends in total annual (− 1.125 mm y − 1) and monsoon (− 1.242 mm y − 1) rainfall over long-term observation in East Madhya Pradesh only. There were no trends recorded for the last 30 years in East Madhya Pradesh. West Madhya Pradesh did not record any trend in rainfall for short as well as long-term observation periods. Rainfall during the months of May and October did not show any trend in both meteorological subdivisions, indicating no shift in the monsoon season over long as well as short temporal observation. It indicates that there is an impact of reported climate change on rainfall as reflected in statistically significant declining trends over long-term observation in Eastern Madhya Pradesh. The decreasing trend in rainfall in Eastern Madhya Pradesh may be attributed to the decreasing frequency of depressions and cyclones in the Bay of Bengal during the monsoon season, but it must be explored more in future research. This study also indicates that any changes in water resources, agricultural, and other socio-economic practices in the study area have not been led by rainfall variability in the last 30 years, particularly since no trend was detected in rainfall in this study. However, better practices for water conservation are always fruitful toward attaining a sustainable future.