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All India mean sunshine duration (SSH in hours), mean total cloud amount (CLD in okta), number of rainy days (NRD in days) and good visibility days (VIS in % days) based upon 40 stations under study for the period 1970-2006 monsoon are shown in Figs. 6 to 10 where regions having significant (at 99%) CCs are shaded.

All India mean sunshine duration (SSH in hours), mean total cloud amount (CLD in okta), number of rainy days (NRD in days) and good visibility days (VIS in % days) based upon 40 stations under study for the period 1970-2006 monsoon are shown in Figs. 6 to 10 where regions having significant (at 99%) CCs are shaded.

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Changes in sunshine duration in association with total cloud amount, rainy days and good visibility days over India were examined for 1970-2006. Climatologically, annual total sunshine duration over west Rajasthan and adjoining Gujarat is more than 3100 hours which is ideal for harnessing solar energy over these regions. The trend analysis indicate...

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... to examine country as a whole trends. The linear trend analysis was performed on these data series and trends were tested for significance at 95% and 99% level of significance using t-test. Average India monthly, annual and seasonal mean and trend values of SSH, CLD, NRD, and VIS are given in Table 1 and monthly variations in means are shown in Fig. 2. Decadal average India means and trends in SSH, CLD, NRD and VIS for 1970-1979(D1), 1980-1989, Decadal means and trends of sunshine duration (SSH), total cloud amount (CLD), rainy days (NRD) and good visibility days (VIS) for India based upon 40 stations under study. SSH, CLD, NRD and VIS means are in hour, okta, days and % days ...

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... The step-by-step calculation and assumptions of the microclimatic parameters in various evapotranspiration methods were obtained from Allen et al. (1998) and Zotarelli et al. (2010). Sunshine hours used in this study were collected from a report by Jaswal (2009). Daily sunshine duration is the sum of the period for which the direct solar irradiance surpasses 120 Wm −2 (WMO 2024). ...
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Global food security and water resources are vulnerable to climatic changes and require evapotranspiration estimation for future crop water requirements. Still, assessment can be challenging to apply to realistic, complex landscapes. Further, agro-meteorological data scarcity in rural areas, drew in use of temperature-based evapotranspiration (TET) models. Therefore, this study developed a region-specific seasonal irrigation demand assessment tool in climate change by calibrating four TET models based on past investigations, with Pan evaporation models for finding the best model. For this purpose, observed climate station and satellite based climate data were utilized. Multilinear Regression (MLR) bias-corrected model was developed for future temperature projections and predictors from 3 General Circulation Model (GCM ) models were used. The model was calibrated using historical data and applied to forecasting water demand for RCP Scenarios. The greatest monthly mean temperature increase (1.4 °C) and decrease (0.01 °C) changes were for February and September during the 2071–2100 and 2041–2070 periods respectively. The study results revealed a rise in irrigation water demand upto 2.5% and 2.4% for the subsequent seasons till the end of century. The developed integrated model showed that single cropping of water-intensive crop consumes more water than multiple cropping. This type of model provided scientific evidence for policy-making targeted at agronomists and water resource managers. Further robust optimization modeling of crop diversification to climate change while considering the future regional food crop demand and available water resources are focus of future research.
... Many methods have been employed to estimate the solar radiation intensity in India, including artificial neural networks (ANNs) [16], Angstrom linear-type correlations [17], and estimates based on the extremes of air temperature [18]. Depending on the region, solar radiation in India ranges between 4 and 7 kWh/m 2 /day, and there are 2300-3200 hours of sunlight per year [19]. As India is a tropical country, it receives solar radiation almost all year round, making it an ideal place to generate solar energy [20]. ...
... Regulatory complexities, including land acquisition, financing, foreign direct investment, and power purchase agreements, introduce bottlenecks into the evolution of the solar market [16,17]. Harmonizing national roadmaps, policies, and programs to facilitate meaningful solar minigrid deployment in rural areas requires meticulous institutional and local coordination [18,19]. ...
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Solar power is energy from the sun that is converted into thermal or electrical energy. China, the USA, and India have the world's richest solar energy sources. India receives solar radiation with an average intensity of 200 MW/km2 and 250-300 sunny days a year. The solar radiation in India varies from 4 to 7 kWh/m2/day, with 2300 to 3200 sunshine hours yearly, depending on the region. Badhla Solar Park, Jodhpur, India, is the world's largest solar plant, with a 2.25 GW installed capacity. Solar energy is the best alternative electricity source used explicitly in the agricultural sector. In the farming sector, the consumption of solar energy has been increasing. The major issues were the installation costs, low availability of technicians, and poor quality of panels. The focus on skill development equips the workforce to drive innovation, efficiency and sustained growth in the renewable energy field. With the support of international collaboration and a skilled workforce, India's progress in solar energy development is a boon for the industry.
... India is blessed with immense solar energy potential, with an average incident solar radiation of 3.5 -7.0 kWh/m2/day and 250 -300 clear sunny days per year. This could be used as a year-round reliable source of energy in groundwater pumping (Sharma et al., 2012;Ramachandra, 2011;Jaswal, 2009). Further, traditionally, farmers execute surface irrigation methods, leading to the overexploitation of groundwater. ...
... Despite numerous benefits, adoption and diffusion of pressurised irrigation system is still far below the potential level though many Indian states are providing good subsidy on pressurised irrigation technologies ( ). Table 2 Eastern region of India receives high solar irradiance with on an average 250 -300 bright days in a year (Sharma et al., 2012;Jaswal, 2009). Typically, mean monthly averaged solar 2 irradiance in this region is ranging from few W/m to about 2 930 W/m and mean monthly averaged solar global radiation 2 is ranging from 3.6-6.4 ...
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Under the policy frameworks and financing schemes for solar energy use in agriculture many Indian states are providing subsidies on small capacity solar pumps even upto 90% for the use of smallholders' irrigation. One of most the popular and subsidised solar pump is of 3.0 HP solar submersible pump, operated by 3.0 kWp solar array. This paper presents the performance of 3.0 HP solar pump with tracking and fixed array evaluated under the prevailing solar global 2 2 radiation of 3.4-6.4 kWh/m /day, solar irradiance of 0-930 W/m and the groundwater depth regime 10 ±4m of Eastern region of India. The results showed that the 3 times manually tracked array yielded 19-23 percent more water compared to fixed array. The mean monthly daily 3 groundwater yield with 3 times manually tracked array was found in range of 80-155 m /day.
... Besides, decreasing sunny days and all-sky solar irradiance has been reported (Jaswal, 2009 (Im et al., 2017;. The present study also revealed an increase in WBGT temperature over most of Pakistan, Afghanistan and the western part of India. ...
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Rising temperature and alteration of other meteorological parameters in the Indian monsoon region have exposed billions of populations in densely populated South Asia to heat stress. This study employed high-resolution ERA5 reanalysis data for assessing spatiotemporal changes in outdoor WBGT over South Asia for the period 1979‒2021. The area affected and exposed population to different heat stress conditions were also estimated using LandScan population datasets. The results revealed an increase in the annual average daily mean WBGT by 0.1‒0.5°C/decade while the monsoon and pre-monsoon mean WBGT by 0.1‒0.7°C/decade over most of South Asia. The large increase in WBGT caused a rise in extreme heat stress-affected areas during monsoon and pre-monsoon by 56% and 66%, respectively; consequently, a rate of 17 million people each year are exposed to excessive heat. The study also revealed the increase in extreme heat stress days by more than 6 days/decade over a major part of the study area. This research's findings and accompanying maps can be applied to future efforts to lessen the likelihood of heat-related stress in South Asian nations, where temperature extremes have grown rapidly in recent years.
... The net radiation (R n ) is estimated using the analytical method proposed by Cai and Mu (2005) and Cai et al. (2007). The cloud cover forecasts (in okta) were translated to sunshine duration (n) using the correlation charts (Jaswal 2009). The shortwave solar radiation (R s ) is estimated from n and the extraterrestrial radiation (R a ) using the Angstrom equation (Allen et al. 1998). ...
Article
Crop simulation models in conjunction with weather forecasts help in understanding soil-water-plant interactions in real time, and thus in effective management of irrigation water. However, selection of the optimal forecast horizon for use with irrigation scheduling is challenging in the context of uncertainties associated with weather forecasts. This study is aimed at evaluating the effectiveness of the Indian Meteorological Department (IMD) short-term weather forecasts with different forecast horizons (1, 3, and 5 days) in simulating crop water and yield dynamics of rice. Rule-based irrigation is triggered by specifying thresholds on the current day’s ponding depth (do), precipitation (Po), and evapotranspiration (ETo) as well as their forecast values (∑ni=1Pi; ∑ni=1ETi; n=1,3,5). The IMD forecasts of temperature, humidity, wind speed, and cloud cover were translated into ETo forecasts using the Penman-Monteith equation and region-specific crop coefficients. The Soil–Water–Atmosphere–Plant (SWAP) model was modified to simulate soil–water and plant growth conditions by considering the three forecast scenarios along with conventional irrigation (ignoring weather forecast), and a hypothetical perfect 5-day forecast (reference). Experiments were conducted in four paddy fields in a command area of south India for two monsoon seasons (2018 and 2019) to calibrate and parameterize the SWAP model. The accuracy of forecast variables is increased with increase in length of forecast horizon (root-mean-square error = 12.5±0.98, skill score = 0.6%±0.03% at 1-day lead to 5.9±2.5, 22.4%±7.8% at 5-day lead) due to averaging. Conventional irrigation has resulted in the highest use of irrigation water (912±12.5 mm), percolation losses (1,245±19.5 mm), and electricity (806.5±100.5 kW), achieving a low yield (2,331±138 kg ha−1). Irrigation scheduling with 5-day forecast horizon outperformed other scenarios (69% water saving and 23% higher yield), and is slightly inferior to the hypothetical perfect forecast. Our results conclude that IMD forecasts, though moderately reliable at multiple lead times, can serve as a valuable tool in scheduling irrigation activities for sustainable management.
... Although the causes of SD variability and the action mechanisms of influential factors are complicated, the variations of climatic factors and human activity are considered to be the main factors. For instance, cloud thickness was identified as the governing factor for SD in the US from 1961 to 1990 (Liepert, 2002), and also played a key role in the decrease of SR in Canada from the late 1950s to the early 1990s (Cutforth and Judiesch, 2007); atmospheric moisture contributed to the decreasing trend of SD in Switzerland over the last century (Rebetez and Beniston, 1998); climatic factors like total cloud amount, rainy days, and good visibility influenced the SD in India during 1970(Jaswal, 2009; decline in sunshine hours in the city of Shijiazhuang, Beijing and Tianjin were heavily influenced by wind speed (Yang et al., 2009a); sunshine hours in the Southwestern China were highly impacted by wind speed, relative humidity, precipitation, cloud cover, surface downwards SR flux, and cloud water content, with wind speed showing the strongest relationship to sunshine hours (Li et al., 2012); surface SR negatively correlates with the near surface water vapour in most region at higher latitudes in China (Wang et al., 2011); additionally, changing meteorological factors, including evaporation and diurnal temperature, were considered critically influential to SD in many parts of the world (Wild, 2009(Wild, , 2012. Highly developed urbanization and industrialization in recent decades also contributed the most to dimming from the 1950s to the 1980s (Alpert et al., 2005); many aerosols and greenhouse gases released during urbanization and industrialization directly or indirectly changed the sunshine condition. ...
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Sunshine duration (SD) is a key index with which to quantitatively measure the intensity and duration of solar radiation. The exploration of spatiotemporal characteristics and potential influential factors for SD could help us better understand solar radiation variability. In this study, we first explore the spatiotemporal variability of SD across mainland China during 1959–2017, then identify the predominant influential climatic factors and detect their relative influence of temporal dynamic on SD, and finally discuss the relative influential rates of climatic factors and detect the dominating climatic factor on a spatial scale. The results show that: Firstly, the annual and seasonal SD gradually decreased from the northwest to southeast across mainland China; a significant decreasing trend (p < .05) was detected for annual SD at a rate of −2.7 h⋅a–1, a turning point significantly occurred in 1986 (p < .05) in the year SD series, and oscillation periods of 2.4–3.8 years existed in mainland China and most sub‐regions. Secondly, the significant (p < .05) decrease of wind speed (Win), increase of precipitation (Pre), and increase of vapour pressure (Vp) were responsible for the decreasing trend of SD with relative influential rates of 39.9, 30.6, and 29.5%, respectively. Thirdly, temporally, the relative influential rate of each climatic variable changed over time; spatially, Win dominated most areas of mainland China (55.9%) during 1959–2017, followed by Pre (24.9%) and Vp (19.2%).
... Solar radiation (sunshine duration) has profound influence on surface temperature, evaporation, the hydrologic cycle and ecosystems and it is the primary source of energy required for sustenance of life on this planet. It has been proved that sunshine duration over India has decreased for all months and the decreasing trends were significant at 99 per cent for January to May and October to December (Jaswal, 2009). Table 3b shows that the results obtained for the slopes of S h and monsoon seasons. ...
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div> Climate change analysis has been conducted using daily surface meteorological datasets in respect of nine parameters from five rubber growing locations in the East and North-East India. Monthly, seasonal and annual variability in meteorological parameters showed decreasing trends in relative humidity, sunshine hours and pan evaporation rates coupled with increasing temperature extremes. Rise in mean temperature was seen to be highest (0.34 0C per decade) for Dhenkanal which experiences dry sub-humid type of climate. The data on relative humidity and temperature also revealed the fact that warm surface temperatures, along with limited moisture availability, may lead to lower relative humidity in the future, since all the stations are away from the moist coastal belts. Decreasing trends in sunshine hours were mainly observed during winter and post monsoon seasons with decreasing number of days even with the optimum required daily sunshine hours. The fact that there were no significant changes in the amount of rainfall or the number of rainy days was in conformity with several earlier reports in the northeast. Mean monthly decadal variations have also been tested with earlier and recent sets. With long term trends in most of the weather parameters, being lesser when compared to that of the traditional rubber growing regions in India, it is imperative that for rubber cultivation to thrive in this non-traditional belt, future policy inputs will have to be based depending on the magnitude of climate change effects. </div
... Solar radiation (sunshine duration) has profound influence on surface temperature, evaporation, the hydrologic cycle and ecosystems and it is the primary source of energy required for sustenance of life on this planet. It has been proved that sunshine duration over India has decreased for all months and the decreasing trends were significant at 99 per cent for January to May and October to December (Jaswal, 2009). Table 3b shows that the results obtained for the slopes of S h Raj 193 and monsoon seasons. ...
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Please see the pdf file here: http://indsocplantationcrops.in/journal.php
... Notably, these smaller cities are located in the plains at the northern-most extension of the Indo-Gangetic plain (IGP), which is one of the most polluted regions of the world (Guttikunda et al., 2003). The decline in SSD observed for the plains in this study is indeed close to that of the IGP during the longer period of 1970-2006(Jaswal, 2009. Studies have reported a continuous increase in the emissions of black carbon (BC) and sulfates in the IGP during the 1990s and 2000s (Sahu et al., 2008;Lu et al., 2011). ...
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We analyzed temporal changes of sunshine duration (SSD) and number of rainy days (NRD) in Nepal across its three physiographic regions: plains, low-hills, and high-hills and mountains for the period 1987-2010 with the records at 13 meteorological stations. We found declining trends in SSD, i.e. solar dimming, across the country at a rate of -0.20% per year with the highest decline in post-monsoon season (-0.33% per year) followed by pre-monsoon season (-0.24% per year). A close look at the individual stations indicated that the declines in pre-monsoon and post-monsoon seasons are common regional phenomena. By region, the dimming is pronounced (-0.56% per year) in the plains at 0-300 meters above sea level and gradually diminishes with an increase in elevation. The NRD for the same 13 stations showed a significant declining trend (-0.20% per year), which suggested that the change in the NRD could not be a major driver of the decrease of SSD in Nepal. We argue that the decline in SSD might be influenced by the trans-boundary air pollution from the Indian sub-continent and biomass burning across the region as suggested by other studies.