Unraveling Precipitation Trends and Variability under the Influence of Climate Change in the Navsari District of Gujarat

doi:10.21203/rs.3.rs-3879480/v1

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Research Article

Unraveling Precipitation Trends and Variability under the Influence of Climate Change in the Navsari District of Gujarat

https://doi.org/10.21203/rs.3.rs-3879480/v1

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Studying the variability of rainfall holds significant importance in the dominion of agriculture. To facilitate the optimal planting of crops in the face of climate fluctuations, agro-meteorologists predominantly depend on rainfall distributions. These distributions serve as a crucial tool for understanding the rainfall patterns within a specific area. This study undertakes a thorough examination of precipitation trends in the Navsari district of Gujarat, spanning the years 1983 to 2022 under the influence of climate change. The study utilized descriptive statistics to assess the characteristics of rainfall, while the Mann-Kendall test is utilized to determine the trend in rainfall patterns. Additionally, the Standard Precipitation Index (SPI) is calculated to quantify the degree of wetness in the region. It was observed that over the four decades, Navsari witnessed an annual mean rainfall of 1662.59 mm, accompanied by a standard deviation of 475.73 mm and a Coefficient of Variation (CV) of 28.61%, indicating notable inconsistency in annual rainfall. Onset delays were observed in five years, with notable delays in 1986, 1992, and 2005. Withdrawal delays occurred in seventeen years, ranging from 7 to more than 15 days. The normal monsoon duration of 111 days was exceeded in fourteen years but curtailed in twenty-six years, with 1996 experiencing the highest and 1986 the lowest monsoon days. Additionally, in the last decade, a noticeable increase in very wet months was observed. Season-wise SPI analysis identified extreme wet conditions in post-monsoon (1983, 1999), winter (1994, 2014), and pre-monsoon seasons.

Rainfall variability is a key factor for predicting the processes in agriculture, hydrology, and climatology. The distribution and amount of rainfall are significantly impacted by climate change (Singh et al., 2021). Rainfall remains one of the most influential meteorological parameters in many aspects of our daily lives. Any variation in rainfall has an impact on the management of water resources, accessibility to fresh water, food production, and nutritional security, both directly and indirectly (Hu et al., 2017).

Most of the farmers are smallholders who depend more on rainfed agriculture rather than irrigated agriculture. Many people utilize rainfall distributions to understand the area's rainfall pattern for effective crop planning in a changing climate. In India, there have been several research done that examined trends in annual and seasonal rainfall (Krishnakumar et al., 2009; Mondal et al., 2015; Kundu et al., 2015). Many researchers also study the rainfall patterns in Gujarat state (Kumar et al., 2017; Priyan, 2015; Patel et al., 2021).

In the non-parametric, the Mann-Kendall test (Mann, 1945 and Kendall, 1975) is widely used in the study of hydrometeorology to detect the significance trend in time series data. (Sandhu and Kaur, 2023) and Standard Precipitation Index (SPI) approach has been used to identify the rainfall patten monthly and seasonally for Navsari area (Das et al., 2022). This study has undertaken an assessment of both seasonal, periodical and annual rainfall trends and variations to gain a more comprehensive understanding of the recent changes in rainfall patterns in the Navsari area.

2.1 Study Area

The study area of Navsari is located between 20°32’ to 21°05’ North Latitude and 72°42’ to 73°30’ East Longitude (Fig. 1) and IMD station which is located at Navsari Agricultural University.

2.2 Meteorological data

Monthly rainfall data collected from the Agro-Meteorological Cell, Department of Agricultural Engineering, N. M. College of Agriculture, Navsari Agricultural University, Navsari for the years of 1983 to 2022 for this study.

2.3 Research Methodology

For this study, data divide into four period viz., P1, P2, P3 and P4 consider as year of 1983 to 1992, 1993 to 2002, 2003 to 2012 and 2013 to 2022, respectively as well as the whole data. January and February, March to May, June to September and October to December consider as winter, pre-monsoon, monsoon and post-monsoon season, respectively.

2.4 Computational Method

The initial assessment of rainfall contains mean, Standard Deviation (SD) and Coefficient of Variance (CV) for monthly, seasonal and period wise to analyze and understand the behavior of rainfall in Navsari station.

Mann-Kendall non-parametric test is applied for detection of rainfall trend in Navsari station. Mann-Kendall test statistics calculated as follows; (Varshney and Satpathy, 2017)

$$S=\sum _{i=1}^{n-1}\sum _{j=i+1}^{n}\text{s}\text{g}\text{n}\left({x}_{j} – {x}_{i}\right)$$

$$\text{s}\text{g}\text{n}\left({x}_{j} – {x}_{i}\right)= \left\{\begin{array}{c}+1, >\left({x}_{j} – {x}_{i}\right)\\ 0, = \left({x}_{j} – {x}_{i}\right)\\ -1, <\left({x}_{j} – {x}_{i}\right)\end{array}\right.$$

Where x_i and x_j represent the data at time i and j. Positive S value indicate the positive trend and negative S value indicate negative trend. Statistically evaluate the significance of the trend, it is necessary to determine the probability associated with S and the sample size n. variance is as follows;

$$Var \left(S\right)=\frac{n\left(n-1\right)\left(2n+5\right)-\sum _{i=1}^{m}{t}_{j}({t}_{j}-1)(2{t}_{j}+5)}{18}$$

Where n is data point, m is tied groups and t_j is data in j^th tied group. Z transformation is applied as follows;

$$Z=\left\{\begin{array}{c}\begin{array}{cc}\frac{S\pm 1}{\sqrt{Var\left(S\right)}}& \text{i}\text{f} \text{S} \ne 0\end{array}\\ \begin{array}{cc}0& \text{i}\text{f} \text{S} = 0\end{array}\end{array}\right.$$

Degree of wetness is calculated by Standard Precipitation Index (SPI) for monthly total rainfall data. SPI is calculated as follows; (das et al., 2022). The SPI is used to predict whether conditions will be wet or dry based on precipitation factors. This state of wetness or dryness can be observed by the SPI over different time frames, spanning sub-seasonal to inter-annual scales.

$$SPI= \frac{({r}_{ij}-{r}_{im})}{\sigma }$$

Where r_ij indicate rainfall at i^th station for j^th observation, rim indicate long term mean rainfall and σ indicate standard deviation. According to McKee et al. (1993), SPI classified into seven classes as given in Table 1.

3.1 Descriptive Statistics of Rainfall in Navsari:

Descriptive statistics of rainfall in Navsari station were calculated monthly and seasonally for 1983 to 2022 year and presented in Table 2. For the period of forty years, mean of annual rainfall in Navsari station is 1662.59 mm with SD of 475.73 mm and CV of 28.61 per cent indicating that the annual rainfall was inconsistent in this area, average of the monsoon rainfall season is 1605.33 mm with SD of 480.11 mm and CV of 29.91 per cent and out of all month, July month have highest rainfall followed by August month which having lowest CV of 47.89 per cent with 638.98 mm mean rainfall but it contains inconsistent in rainfall and least rainfall obtain in April month.

Table 2

Monthly, Seasonal and Annual rainfall in Navsari for the period of 1983 to 2022
Month/Season	Mean	SD	CV (%)
Jan	1.52	4.95	325.26
Feb	0.54	2.06	382.69
Mar	0.57	1.86	326.10
Apr	0.17	0.61	356.39
May	6.13	23.62	385.62
Jun	303.11	249.06	82.17
Jul	638.98	306.03	47.89
Aug	372.33	238.56	64.07
Sep	290.92	207.22	71.23
Oct	36.90	54.96	148.96
Nov	6.75	14.59	216.11
Dec	4.68	13.29	283.96
Winter	2.06	5.20	252.59
Pre-Monsoon	6.87	23.53	342.62
Monsoon	1605.33	480.11	29.91
Post-Monsoon	48.33	56.46	116.83
Annual	1662.59	475.73	28.61

In period wise analysis (Table 3), highest average rainfall occurs in P3 period (1896.64 mm) followed by P4 period (1751.79 mm) with CV of 20.58 and 26.49 per cent, respectively indicating consistent in rainfall in P3 period as compare to another period. In monthly period wise analysis, mostly July month indicate lowest CV (49.60, 42.39 and 41.89 in P2, P3 and P4, respectively) except P1 period so that it indicates now a days CV is continuously decreasing in July month and highest rainfall occurs in July month (600.12, 536.16, 733.74 and 685.9 in P1, P2, P3 and P4, respectively) and it indicate highest in P3 period.

3.2 Trend Analysis of rainfall in Navsari:

Mann-Kendall test applied for trend of rainfall in Navsari area and concluded in Table 4. For the period of forty years, among all season, Monsoon season having significantly increasing trend (z-value is 2.01) whereas Winter, Pre-monsoon and Post-monsoon season have no trend. From this monsoon season, September month having significantly increasing trend (z-value is 2.66) whereas another month have no trend. The graphical representation of month wise z-statistics value given in the Fig. 2.

P3 period having significant decreasing trend in Monsoon season, whereas another any season have no trend in other period (P1, P2 and P4). Out of P3 period in monsoon season, June and July month having significantly negative trend (Fig. 3).

Table 3 Monthly, Seasonal and Annual rainfall in Navsari for the period of P1, P2, P3 and P4
Month/ Season	P1			P2			P3			P4
Month/ Season	Mean	SD	CV (%)	Mean	SD	CV (%)	Mean	SD	CV (%)	Mean	SD	CV (%)
Jan	0.04	0.13	316.23	4.45	8.50	191.11	0.2	0.63	316.23	1.4	4.42	316.23
Feb	0.19	0.60	316.23	0.36	1.13	316.23	1.6	3.86	241.52	0	0	-
Mar	0.18	0.57	316.23	0.9	1.89	210.82	0	0	-	1.2	3.15	262.94
Apr	0	0	-	0.32	0.70	218.9	0	0	-	0.37	1.00	272.08
May	4.64	14.29	307.99	3.2	5.13	160.46	1.82	2.96	162.7	14.84	45.39	305.93
Jun	272.22	156.37	57.44	341.1	265.33	77.78	357.51	368.81	103.16	241.59	166.66	68.98
Jul	600.12	360.47	60.07	536.16	265.94	49.60	733.74	311.08	42.39	685.9	287.34	41.89
Aug	329.78	165.67	50.24	292.57	197.12	67.37	467.56	214.67	45.91	399.4	338.03	84.63
Sep	227.17	199.14	87.66	173.77	134.34	77.30	337.83	167.92	49.70	424.9	240.87	56.68
Oct	42.67	80.02	187.55	51.08	61.78	120.96	17.44	25.92	148.65	36.4	38.92	106.93
Nov	3.55	7.94	223.77	5.44	11.98	220.36	6.52	12.65	194.16	11.5	22.74	197.79
Dec	0.53	1.676	316.23	3.29	6.07	184.67	0.7	2.21	316.23	14.2	24.10	169.76
Winter	0.23	0.60	260.91	4.81	8.37	174.02	1.80	3.82	212.44	1.40	4.43	316.23
Pre-Monsoon	4.82	14.24	295.37	4.42	5.11	115.65	1.82	2.96	162.70	16.41	44.95	273.93
Monsoon	1429.29	487.82	34.13	1343.60	405.62	30.19	1896.64	390.36	20.58	1751.79	464.02	26.49
Post-Monsoon	46.75	78.42	167.74	59.81	61.33	102.55	24.66	35.00	141.94	62.10	41.18	66.31
Annual	1481.09	510.57	34.47	1412.64	381.62	27.01	1924.92	383.71	19.93	1831.7	461.4	25.19
Note: P1 = 1983 to 1992, P2 = 1993 to 2002, P3 = 2003 to 2012 and P4 = 2013 to 2022

Table 4

Mann-Kendall test statistics of rainfall in Navsari station
Month/Season	P1			P2			P3			P4			(1983–2022)
Month/Season	z-value	P value	Trend	z-value	P value	Trend	z-value	P value	Trend	z-value	P value	Trend	z-value	P value	Trend
Jan	-1.39	0.16	N	-1.72	0.08	N	0	1	N	-1.04	0.29	N	-1.04	0.29	N
Feb	0.69	0.48	N	0.34	0.72	N	-1.03	0.3	N	0	1	N	-0.33	0.73	N
Mar	0.34	0.72	N	0	1	N	0	1	N	-1.03	0.3	N	0.14	0.88	N
Apr	0	1	N	1.03	0.3	N	0	1	N	-1.81	0.06	N	0.74	0.45	N
May	0	1	N	1.11	0.26	N	0.77	0.43	N	0	1	N	0.44	0.65	N
Jun	-0.17	0.85	N	0	1	N	-2.14	0.03	D	0	1	N	-0.78	0.43	N
Jul	-0.35	0.72	N	-1.43	0.15	N	-2.14	0.03	D	0	1	N	0.4	0.68	N
Aug	-0.35	0.72	N	1.78	0.07	N	0.17	0.85	N	0.35	0.72	N	1.01	0.31	N
Sep	0.17	0.85	N	-1.25	0.21	N	1.6	0.1	N	0.17	0.85	N	2.66	0.007	I
Oct	-0.19	0.84	N	-0.63	0.52	N	0.98	0.32	N	0.44	0.65	N	0.75	0.44	N
Nov	0.51	0.6	N	0	1	N	1	0.31	N	0	1	N	1	0.31	N
Dec	0	1	N	1.22	0.22	N	0	1	N	1.44	0.14	N	1.35	0.17	N
Winter	-0.25	0.79	N	-1.72	0.08	N	-1	0.31	N	-1.04	0.29	N	-1.02	0.3	N
Pre-Monsoon	0.55	0.57	N	1.29	0.19	N	0.77	0.43	N	-0.57	0.56	N	0.72	0.46	N
Monsoon	-0.89	0.37	N	-0.89	0.37	N	-2.14	0.03	D	1.07	0.28	N	2.01	0.04	I
Post-Monsoon	-0.37	0.71	N	-0.53	0.59	N	1.07	0.28	N	0.53	0.59	N	1.01	0.3	N
Notation: N = No Trend, I = Increasing Trend and D = Decreasing Trend

3.3 Variability in onset, withdrawal and duration of monsoon in Navsari

The monsoon season start in Navsari on the 15th June and withdrawal in 3rd October. The variability in onset of monsoon, withdrawal of monsoon and duration of monsoon in Navsari during 1983 to 2022 (40 years) are presented in Table 5. The onset of monsoon in Navsari was delayed for five years i.e., by up to 7 days during four year (1983, 1986, 1992 and 2005) and by 8 to 14 days during one year (2009). The remaining year observed early onset of monsoon in Navsari (Thirty-three years). The normal withdrawal of monsoon in Navsari should occur up to 3rd October, delay of withdrawal occurs in seventeen years i.e., by up to 7 days during ten years (1985, 1997, 2001, 2008, 2010, 2012, 2013, 2016, 2019 and 2022), by 8 to 14 days during six years (1983, 1990, 1999, 2015, 2017 and 2021) and more than 15 days during one year (1996).

The normal duration of monsoon in Navsari is 111 days (15th June to 3rd October). Out of this, fourteen years occurs more duration compare to normal and remaining twenty-six years observed less duration of monsoon as compare to normal. Highest monsoon days occurs in the year of 1996 and least monsoon days in 1986.

Table 5

Variability in onset, withdrawal and duration of monsoon in Navsari
Year	Onset date	Deviation from Normal (Days)	Withdrawal date	Deviation from Normal (Days)	Duration of Monsoon
1983	17-Jun	-2	12-Oct	9	117
1984	13-Jun	2	21-Sep	-12	100
1985	1-Jun	14	10-Oct	7	131
1986	17-Jun	-2	5-Sep	-28	80
1987	10-Jun	5	13-Sep	-20	95
1988	2-Jun	13	1-Oct	-2	121
1989	6-Jun	9	29-Sep	-4	115
1990	1-Jun	14	11-Oct	8	132
1991	7-Jun	8	21-Sep	-12	106
1992	17-Jun	-2	30-Sep	-3	105
1993	12-Jun	3	28-Sep	-5	108
1994	10-Jun	5	19-Sep	-14	101
1995	15-Jun	0	24-Sep	-9	101
1996	12-Jun	3	28-Oct	25	138
1997	2-Jun	13	5-Oct	2	125
1998	8-Jun	7	28-Sep	-5	112
1999	1-Jun	14	12-Oct	9	133
2000	1-Jun	14	8-Sep	-25	99
2001	3-Jun	12	10-Oct	7	129
2002	11-Jun	4	18-Sep	-15	99
2003	13-Jun	2	29-Sep	-4	108
2004	10-Jun	5	1-Oct	-2	113
2005	19-Jun	-4	25-Sep	-8	98
2006	1-Jun	14	3-Oct	0	124
2007	1-Jun	14	28-Sep	-5	119
2008	7-Jun	8	6-Oct	3	121
2009	26-Jun	-11	9-Oct	6	105
2010	4-Jun	11	29-Sep	-4	117
2011	4-Jun	11	27-Sep	-6	115
2012	8-Jun	7	7-Oct	4	121
2013	8-Jun	7	10-Oct	7	124
2014	13-Jun	2	21-Sep	-12	100
2015	8-Jun	7	12-Oct	9	126
2016	15-Jun	0	7-Oct	4	114
2017	8-Jun	7	14-Oct	11	128
2018	3-Jun	12	23-Sep	-10	112
2019	12-Jun	3	4-Oct	1	114
2020	1-Jun	14	27-Sep	-6	118
2021	5-Jun	10	13-Oct	10	130
2022	12-Jun	3	9-Oct	6	119
Normal	15-Jun		03-Oct		111

3.4 Standard Precipitation Index (SPI)

The monthly and season wise SPI of Navsari is presented in Table 6 and Table 7 respectively. According to SPI calculation, the occurrence of extremely wet conditions is notable for specific months in various years viz. 1994 (January and June), 2002 (March and April), 2014 (January and November), 2019 (September and November), 2020 (August and December) and 2021 (May and December). Consequently, over the last decade, there has been a prevalence of extremely wet months.

Examining the season-wise SPI index, Navsari experienced extremely wet conditions in the post-monsoon season during 1983 and 1999, in the winter season during 1994 and 2014, whereas pre monsoon season having extremely wet condition in pre monsoon season.

Table 6 Monthly SPI value of Navsari Area
	January	February	March	April	May	June	July	August	September	October	November	December
1983	-0.227	-0.261	-0.307	-0.281	-0.259	-0.279	0.137	0.976	0.774	3.659	-0.463	-0.352
1984	-0.307	-0.261	-0.307	-0.281	-0.259	0.171	-0.402	-0.320	-0.123	-0.671	-0.463	-0.352
1985	-0.307	-0.261	-0.307	-0.281	-0.213	-0.747	-0.951	0.580	-0.928	1.741	-0.463	-0.352
1986	-0.307	-0.261	-0.307	-0.281	-0.259	0.403	0.418	-0.976	-1.336	-0.671	-0.463	-0.352
1987	-0.307	-0.261	-0.307	-0.281	-0.259	-0.280	-0.586	-0.173	-1.371	-0.671	0.366	0.047
1988	-0.307	-0.261	-0.307	-0.281	-0.259	-0.252	2.656	-0.767	0.395	-0.540	-0.463	-0.352
1989	-0.307	-0.261	0.662	-0.281	-0.259	-0.275	-0.265	-0.642	-0.857	-0.671	-0.463	-0.352
1990	-0.307	0.662	-0.307	-0.281	1.659	-0.350	-1.816	-0.073	0.517	-0.475	1.141	-0.352
1991	-0.307	-0.261	-0.307	-0.281	-0.259	-0.926	0.279	-0.970	-1.288	-0.671	-0.463	-0.352
1992	-0.307	-0.261	-0.307	-0.281	-0.259	1.295	-0.740	0.583	1.140	0.022	-0.463	-0.352
1993	-0.307	-0.261	2.114	-0.281	-0.259	0.868	-0.151	-1.165	-0.055	0.768	-0.463	-0.352
1994	5.226	-0.261	-0.307	-0.281	-0.259	2.356	0.798	-0.496	-0.504	-0.671	-0.463	-0.352
1995	0.904	-0.261	-0.307	-0.281	-0.259	-1.166	0.423	-0.643	-0.350	-0.253	-0.463	-0.352
1996	0.702	-0.261	-0.307	-0.281	-0.259	-0.499	-0.068	-0.557	-1.264	1.932	-0.463	-0.352
1997	0.924	-0.261	-0.307	1.671	0.215	0.245	-1.281	-0.391	-0.620	-0.417	0.894	0.596
1998	-0.307	-0.261	-0.307	-0.281	-0.259	-0.974	0.109	-0.583	0.885	0.839	1.908	-0.352
1999	-0.307	1.489	-0.307	-0.281	0.012	0.090	-1.019	-1.191	-0.780	2.265	-0.463	-0.352
2000	-0.307	-0.261	-0.307	-0.281	0.295	-0.760	0.407	-0.227	-1.346	-0.671	-0.463	0.874
2001	-0.307	-0.261	-0.307	-0.281	-0.204	0.751	-0.614	1.713	-1.036	-0.540	-0.463	-0.352
2002	-0.307	-0.261	2.114	2.973	-0.259	0.614	-1.961	0.197	-0.582	-0.671	-0.463	-0.051
2003	-0.307	5.573	-0.307	-0.281	-0.259	1.644	1.645	0.076	-0.535	-0.653	-0.463	-0.352
2004	-0.307	-0.261	-0.307	-0.281	0.037	0.216	1.385	0.616	-0.625	-0.468	-0.463	-0.352
2005	-0.307	-0.261	-0.307	-0.281	-0.259	3.777	-0.587	-0.161	0.518	-0.671	-0.463	-0.352
2006	-0.307	-0.261	-0.307	-0.281	-0.259	0.413	1.217	-0.391	-0.759	-0.216	-0.463	-0.352
2007	0.096	-0.261	-0.307	-0.281	-0.259	-0.491	-0.246	0.937	0.271	-0.671	0.017	-0.352
2008	-0.307	1.683	-0.307	-0.281	-0.259	-0.652	0.360	1.503	0.483	-0.544	-0.463	0.175
2009	-0.307	-0.261	-0.307	-0.281	-0.259	-1.044	1.347	-0.736	-0.246	0.857	0.990	-0.352
2010	-0.307	-0.261	-0.307	-0.281	-0.259	-0.135	-0.308	1.420	1.421	-0.071	2.073	-0.352
2011	-0.307	-0.261	-0.307	-0.281	-0.039	-0.948	-0.513	1.449	0.158	-0.649	-0.463	-0.352
2012	-0.307	-0.261	-0.307	-0.281	-0.005	-0.595	-1.202	-0.722	1.578	-0.453	-0.463	-0.352
2013	-0.307	-0.261	-0.307	4.925	-0.242	1.061	0.595	-0.043	1.704	0.147	-0.463	-0.352
2014	2.520	-0.261	-0.307	-0.281	-0.259	-1.072	0.261	-0.203	0.425	-0.671	4.128	-0.352
2015	-0.307	-0.261	5.073	0.533	-0.259	0.307	-1.039	-1.288	0.719	-0.617	-0.463	-0.352
2016	-0.307	-0.261	0.769	-0.281	-0.259	-0.852	-0.382	-0.580	1.149	1.075	-0.463	-0.352
2017	-0.307	-0.261	-0.307	-0.281	-0.090	-0.033	-0.091	-0.291	-1.018	-0.162	-0.463	2.432
2018	-0.307	-0.261	-0.307	-0.281	-0.259	-0.735	2.101	-0.685	-1.095	-0.671	-0.463	-0.352
2019	-0.307	-0.261	-0.307	-0.281	-0.259	-0.165	-0.484	0.682	2.215	1.057	2.073	-0.352
2020	-0.307	-0.261	-0.307	-0.281	-0.259	-0.747	0.114	3.742	-0.390	-0.580	-0.463	2.583
2021	-0.307	-0.261	-0.307	-0.281	5.837	0.325	-0.706	-0.848	0.975	-0.344	0.291	4.614
2022	-0.307	-0.261	-0.307	-0.281	-0.259	-0.559	1.163	0.648	1.781	0.675	-0.463	-0.352

Table 7 Season wise SPI value in Navsari area
	1983	1984	1985	1986	1987	1988	1989	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	2001	2002
Winter	-0.319	-0.396	-0.396	-0.396	-0.396	-0.396	-0.396	-0.031	-0.396	-0.396	-0.396	4.870	0.757	0.565	0.776	-0.396	0.296	-0.396	-0.396	-0.396
Pre-Monsoon	-0.292	-0.292	-0.245	-0.292	-0.292	-0.292	-0.215	1.633	-0.292	-0.292	-0.101	-0.292	-0.292	-0.292	0.235	-0.292	-0.020	0.265	-0.237	-0.016
Monsoon	0.761	-0.380	-1.106	-0.586	-1.197	1.352	-1.000	-1.152	-1.340	0.982	-0.248	1.267	-0.806	-1.125	-1.151	-0.344	-1.532	-0.828	0.402	-1.085
Post-Monsoon	3.359	-0.856	1.492	-0.856	-0.548	-0.728	-0.856	-0.250	-0.856	-0.181	0.545	-0.856	-0.449	1.678	-0.034	1.227	2.003	-0.567	-0.728	-0.785

	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022
Winter	1.910	-0.396	-0.396	-0.396	-0.012	0.373	-0.396	-0.396	-0.396	-0.396	-0.396	2.295	-0.396	-0.396	-0.396	-0.396	-0.396	-0.396	-0.396	-0.396
Pre-Monsoon	-0.292	0.006	-0.292	-0.292	-0.292	-0.292	-0.292	-0.292	-0.071	-0.037	-0.139	-0.292	0.154	-0.207	-0.122	-0.292	-0.292	-0.292	5.828	-0.292
Monsoon	1.709	1.031	1.728	0.468	0.171	0.846	-0.155	1.052	-0.030	-0.753	1.644	-0.307	-0.833	-0.478	-0.659	0.145	0.901	1.376	-0.282	1.543
Post-Monsoon	-0.838	-0.658	-0.856	-0.413	-0.732	-0.608	1.007	0.384	-0.835	-0.643	-0.059	0.331	-0.803	0.844	0.295	-0.856	1.482	-0.077	0.827	0.455

This study revealed that, Rainfall distribution is inconsistent over the Navsari area and highest rainfall occurs in July month and followed by the month is shifted to September month. For the rainfall trend, the monsoon season has a significantly increasing trend and out of this, September month has significantly increased trend in Navsari area during the period of 1983 to 2022 years. The study reveals a significant annual rainfall mean of 1662.59 mm with remarkable variability. Monsoon onset delays, withdrawal variations, and deviations from the normal 111-day monsoon duration were observed. Extremely wet condition is more observed in last period as compare to another. Season-wise SPI analysis identified extreme wet conditions in post-monsoon, winter, and pre-monsoon seasons. These findings contribute vital insights for informed agricultural practices and climate adaptation in the Navsari region. By understanding rainfall fluctuations, farmers can implement adaptive strategies, such as choosing drought-resistant crops or optimizing irrigation practices, to mitigate the risks associated with unpredictable weather patterns.

Funding

This research did not receive any funding.

Availability of data and materials

The datasets used in this study are available upon request.

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Ethics approval and consent to participate

The manuscript is original work of authors and is not being submitted or under consideration apart from this journal.

Competing interests

There are no competing interests among the authors.

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Unraveling Precipitation Trends and Variability under the Influence of Climate Change in the Navsari District of Gujarat

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Abstract

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1. Introduction

2. Materials and Methods

2.1 Study Area

2.2 Meteorological data

2.3 Research Methodology

2.4 Computational Method

3. Results and Discussion

3.1 Descriptive Statistics of Rainfall in Navsari:

3.2 Trend Analysis of rainfall in Navsari:

3.3 Variability in onset, withdrawal and duration of monsoon in Navsari

3.4 Standard Precipitation Index (SPI)

Conclusion

Declarations

References

Additional Declarations

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