Annual Temperature Trends Research Articles

Sea surface temperature trend analysis by Mann-Kendall test and sen’s slope estimator: a study of the Hai Phong coastal area (Vietnam) for the period 1995-2020

Based on the Mann-Kendall test and Sen’s slope method, this study investigates the monthly, seasonal, and annual sea surface temperature (SST) trends in the coastal area of Hai Phong (West of Tonkin Gulf) based on the measurements at Hon Dau Station from 1995 to 2020. The results show a sea surface warming trend of 0.02°C/year for the period 1995-2020 (significant level α = 0.1) and of 0.093°C/year for the period 2008-2020 (significant level α = 0.05). The monthly SSTs in June and September increased by 0.027°C/year and 0.036°C/year, respectively, for the period 1995-2020, and by 0.080°C/year and 0.047°C/year, respectively, for the period 2008-2020. SST trends in winter, summer, and other months were either different for the two periods or not significant enough. This may be due to the impact of ENSO, which caused interannual SST variability in the Hai Phong coastal with two intrinsic mode functions (IMF) signals a period of ~2 (IMF3) and ~5.2 years cycle (IMF4). A combination of these signals had a maximum correlation of 0.22 with ONI (Oceanic Niño Index) delayed by 8 months. ENSO events took ~8 months to affect SST at Hai Phong coastal area for 1995-2020 and caused a variation of SST within 1.2°C.

Climate Variability Patterns and Farmers’ Perceptions of Its Impact on Food Production: A Case Study of the Gelda Watershed in the Lake Tana Basin in Northwest Ethiopia

This study looked at patterns of erratic climate and farmer perceptions in the Gelda watershed of Lake Tana Basin in northwestern Ethiopia. The National Meteorological Agency of Ethiopia provided essential climatic data for the period between 1981 and 2011. A household survey and focus group discussions were also used to understand about local communities’ perceptions of climate variability and its impact on food production. Time series trend analysis of observed rainfall and temperature conditions was detected using linear regression analysis. To compare the means of climatic parameters and determine whether the average difference was significantly different from zero, the paired sampled t-test was used. The study found that the average annual temperature trend increased by 1.1°C, while the amount and distribution of annual and monthly rainfall decreased, varied across the catchment, and fluctuated during the study periods (1981–2011) at mean temperature rise with an average rate of 0.17°C in the last decade. The variability of annual and monthly rainfall in terms of intensity and distribution has decreased and varied across the watershed. The analysis revealed that annual rainfall variability was variable in the upper catchment (CV > 11.7%) and lower catchment (CV > 14.4%). The amount and intensity of temperature, on the other hand, increased throughout the study watershed, despite observed variation both spatially and temporally (stated decades). Farmers’ understanding and expression of climate variability in terms of erratic rainfall distribution, decreasing amount, and increasing temperature over the last three decades, however, matched the observed data. Moreover, farmers are pointed out that high population pressure; deforestation and intensified agriculture are responsible factors for the variability of climate in the study watershed. Therefore, based on the findings, scientist and policymakers has to design appropriate adaptation measures that can tackle the aggravation of climate variability for future.

TREND DETECTION OF AVERAGE ANNUAL RAINFALL AND TEMPERATURE IN SULAYMANIYAH GOVERNORATE, IRAQ

Change in the magnitudes of temperature and rainfall temporally and spatially can be observed, on both regional and global scales, so detecting the trend of their changes is essential to fit the management plans of hydrological, agricultural, and other water-related activities. In this study, the trend of annual temperature and annual rainfall magnitudes within Sulaymaniyah Governorate have been investigated by using the Mann–Kendall trend test and Sen’s slope estimator. The recorded data at five stations namely Sulaymaniyah, Dukan, Halabja, Penjwen, and Chamchamal stations across Sulaymaniyah Governorate have been studied. The results showed that the positive increasing trend appeared in the annual temperature values of the data of Sulaymaniyah, Dukan, Penjwen, and Chamchamal stations, while Halbja station didn’t reveals any trend in its annual temperature values. Regarding the trend of annual magnitudes of rainfall, the results showed that the trend didn’t appears in the rainfall magnitudes of all of the studied stations, based on the calculated value of (Z), the trend has not appeared in average annual rainfall depth in all of the studied stations at the significant level of 95%, however by taking the p-values, slightly trend toward negative was observed in Sulaymaniyah Station, while moderately trend toward negative and positive increase has appeared in Halabja and Chamchamal stations respectively, but at Dukan and Penjwen Stations, the trend has not appeared in the average annual rainfall.

Streamflow trends during recent decades at some near-natural catchments in Iran

ABSTRACT In this study, we assessed the impacts of climate variations on streamflow in 28 near-natural catchments in Iran. To this end, we analysed the trend of annual streamflow, precipitation, and temperatures using the Mann-Kendall test and Sen’s slope between water years 1982 and 2011. We evaluated the frequency of precipitation in different classes, i.e. below 5, 5–10, 10–15, and above 15 mm/day. Our results indicate a decline in streamflow at 25 catchments, at a rate of −5.66 to −0.19 mm/year. The annual precipitation amount did not decrease significantly, while the frequency of light precipitation events (<5 mm/day) increased. About 60% of the upward trend was significant. Mean temperature increased at all studied catchments, at an average rate of 0.055°C/year. In short, our results indicate that increases in temperature and the frequency of light precipitation events are two leading factors in streamflow reduction across studied catchments.

Detection of annual and seasonal temperature variability and change using non-parametric test- A case study of Bundelkhand region of central India

Consequences of global warming and climate change are major threat to humans and their socio-economic activities. Agriculture of Bundelkhand region is supposed to be more vulnerable due to emerging scenario of climate change and poor socio-economic status of farming community. Many studies carried out elsewhere have shown evidence of regional temperature variability along with global climate changes. This study focuses on the temporal variability and trend in annual and seasonal temperature (1901-2012) at six locations of Bundelkhand region. The results of the analysis reveal that the annual maximum (TMax) and minimum (TMin) temperature has significantly increasing trend in all the locations in the range of 0.5 to 2.0oC 100 year-1 and 0.5 to 1.1 oC 100 year-1, respectively. Seasonal analysis revealed warming trend in both TMax (0.6-2.6oC100 year-1) and TMin (0.9 to 2.3 oC 100 year-1) during post-monsoon and winter season in all the locations. Majority of the locations showed cooling trend (0.3-1.0 oC 100 year-1), in the mean maximum and minimum temperature during monsoon season except at two locations i.e Jhansi and Banda. However, a significant positive trends (2.9 oC) in the TMin was found for the period of hundred years at Banda district during monsoon season.

Evidence of Climate Change Based on Lake Surface Temperature Trends in South Central Chile

Lake temperature has proven to act as a good indicator of climate variability and change. Thus, a surface temperature analysis at different temporal scales is important, as this parameter influences the physical, chemical, and biological cycles of lakes. Here, we analyze monthly, seasonal, and annual surface temperature trends in south central Chilean lakes during the 2000–2016 period, using MODIS satellite imagery. To this end, 14 lakes with a surface area greater than 10 km2 were examined. Results show that 12 of the 14 lakes presented a statistically significant increase in surface temperature, with a rate of 0.10 °C/decade (0.01 °C/year) over the period. Furthermore, some of the lakes in the study present a significant upward trend in surface temperature, especially in spring, summer, and winter. In general, a significant increase in surface water temperature was found in lakes located at higher altitudes, such as Maule, Laja and Galletué lakes. These results contribute to the provision of useful data on Chilean lakes for managers and policymakers.

Precipitation and Temperature trend analysis by Mann Kendall test: The case of Addis Ababa methodological station, Addis Ababa, Ethiopia

The impact of climate change on annual and monthly air precipitation and temperature has received a great deal of attention by scholars worldwide. This study focuses on detecting trends in annual precipitation and temperature for Addis Ababa methodological station located in Addis Ababa. SPSS in combination with the excel spreadsheet used for analyzing the statistics. We were also used the Mann-Kendall trend test and Sen’s slope method to detect trends and the magnitude of change. According to our analysis, the mean minimum temperature ranges between 8.45°C and 12.5°C, while, the mean maximum temperature varies between 21.1°C and 25.5°C From the analysis the monthly coefficient of variation (CV%) for both maximum and minimum temperature ranging from (5.4% in April) to (14.08% in December). According to the Mann Kendal test and Sen’s slope estimate, the annual maximum temperature shows a statistically significant increasing trend but no significant positive or negative trend was detected in annual perception as well minimum temperature.

Monthly river temperature trends across the US confound annual changes

Climate variations and human modifications of the water cycle continue to alter the Earth’s surface water and energy exchanges. It is therefore critical to ascertain how these changes impact water quality and aquatic ecosystem habitat metrics such as river temperatures. Though river temperature trend analyses exist in the literature, studies on seasonal trends in river temperatures across large spatial extents, e.g. the contiguous United States (US), are limited. As we show through both annual and monthly trend analyses for 20 year (n = 138 sites) and 40 year (n = 40 sites) periods, annual temperature trends across the US mask extensive monthly variability. While most sites exhibited annual warming trends, these annual trends obscured sub-annual cooling trends at many sites. Monthly trend anomalies were spatially organized, with persistent regional patterns at both reference and human-impacted sites. The largest warming and cooling anomalies happened at human impacted sites and during summer months. Though our analysis points to coherence in trends as well as the overall impact of human activity in driving these patterns, we did not investigate the impact of river temperature observation accuracy on reported trends, an area needed for future work. Overall, these patterns emphasize the need to consider sub-annual behavior when managing the ecological impacts of river temperature throughout lotic networks.

Trend and change-point detection analyses of rainfall and temperature over the Awash River basin of Ethiopia

Awash River basin (ARB) as a system is in a state of continuous change that requires successive studies to discern the changes or trends of climatic elements through time due to climate change/variability, and other socio-economical developmental activities in the basin. The livelihood of communities in the ARB is primarily based on rainfall-dependent agriculture. Effects of rainfall anomalies such as reduction of agricultural productivity, water scarcity, and food insecurity are becoming more prevalent in this area. In recent years, ARB has been experiencing more frequent rainfall anomalies that change-point detection test and trend analyses of basin rainfall associated with sea surface temperature is crucial in providing guidance to improve agricultural productivity in ARB. Change-point detection tests such as Pettit's, the von Neumann ratio (VNR), Buishand's range (BR) and standard normal homogeneity (SNH) plus trend analysis Mann-Kendall (MK) test of rainfall and temperature data from 29 meteorological stations in the ARB were carried out from 1986 to 2016. A significant increasing trend of annual and seasonal temperature was found. The temperature change-points for the annual and major rainy season (MRS) were detected in 2001, while for the minor rainy season (mRS) in 1997. A significant decreasing trend, shift, and high variability of rainfall were detected in the downstream part of the ARB. The BR and SNH results showed that the mRS rainfall change-point was in 1998, with a subsequent mean annual decrease of 52.5 mm. The increase (decrease) of rainfall in the annual and MRS was attributable to La Niña (El Niño) events. The significant decreasing trend and change-point of rainfall in the mRS was attributable to the steady warming of the Indian and Atlantic Oceans, local warming, and La Niña events. With this knowledge of the current trends and change-point for rainfall and temperature in the ARB, it is therefore essential that appropriate integrated water management and water-harvesting technologies are established, especially in the downstream areas. Moreover, early detection of El Niño episodes would provide invaluable warning of impending rainfall anomalies in the ARB and would enable better preparations to mitigate its negative effects.

Hydro-climatic Variability and Trend Analysis of Modjo River Watershed, Awash River Basin of Ethiopia

Climate change and variability is expected to trigger changes in temperature and precipitation series. This study aimed at assessing variability and trend of hydro-climatic variables at Modjo River watershed. Long-term climate data of 5 representative stations with in the watershed (1981-2010) and streamflow data of Modjo gauging station (1983 -2010) were used. Rainfall variability was analyzed using Coefficient of variation (CV), Precipitation concentration index (PCI) and Standardized anomaly index (SAI). Climate trends were evaluated using Sen’s slope estimator and Mann–Kendall trend test methods. The study revealed Most of the stations showed low variation in annual rainfall (CV% &lt;20) while the main (Kiremt) and short (Belg) season rainfall exhibited CV ranging from low to high. Both annual and seasonal rainfall showed a non-significant trend at all stations for the past 30 years. However, majority of stations showed an increasing trend in annual daily average temperature ranging from 0.2 to 0.6ºC per decade. Following increases in temperature and the subsequent rise in evapotranspiration, streamflow has shown a high significant declining trend. The temporal decline in streamflow at Modjo watershed could likely affect downstream Koka dam water reserve. Thus, any watershed management strategy that can optimize water conservation for sustainable crop production and option that can improve flow to the reserve is vital. Keywords: Climate change, Climate variability, Hydro-climate, trend, Modjo river watershed DOI: 10.7176/JEES/11-9-04 Publication date: September 30 th 2021

Temperature and Rainfall Trends in Central Highland and Mid Rift Valley of Ethiopia

The study was carried out to identify the trends of rainfall, minimum and maximum temperature for Bishoftu, Adama, Meki, Metehara, and Holeta regions of Ethiopia in the years from 1970 to 2018. Mann Kendall test and Sen’s slope estimators’ methods, were used to detecting the trends of rainfall, minimum temperature, and maximum temperature. The result reveals that annual rainfall shows no trend at Metehara station but all stations have significant trend of declining annual rainfall Except for Adama station where significant trend was detected with an increasing rate of 1.148mm/annum. On the other hand, the trend of maximum temperature has significantly increasing in all stations with rates of 0.032, 0.24,0.05, and 0.46 Holeta, Bishofta, Metehara and Mieso stations respectively. While the trend of annual minimum temperature of all stations has significantly increasing trend at 70% confidence interval but at 95% significant level Metehara, Bishoftu and Adama 0.023, 0.01 and 0.048 0 C/annual show increasing trend respectively. Overall, the estimated values indicated that there is climate change in the study area. From this, it can be concluded the effect of global warming is present in both the highland and low land of Ethiopia.

Trend and Change-Point Detection Analyses of Rainfall and Temperature Over the Awash River Basin of Ethiopia

Awash River basin (ARB) as a system is in a state of continuous change that requires successive studies to discern the changes or trends of climatic elements through time due to climate change/variability, and other socio-economical developmental activities in the basin. The livelihood of communities in the ARB is primarily based on rainfall-dependent agriculture. Effects of rainfall anomalies such as reduction of agricultural productivity, water scarcity, and food insecurity are becoming more prevalent in this area. In recent years, ARB experienced more frequent and intense spatio-temporal rainfall anomalies, which make the shift and trend analyses of rainfall associated with sea surface temperature crucial in providing guidance to improve agricultural productivity. Change-point detection tests (Pettit’s, the von Neumann ratio (VNR), Buishand’s range (BR) and standard normal homogeneity (SNH)) and Mann-Kendall (MK) trend analysis of rainfall and temperature data from 29 meteorological stations in the ARB were carried out from 1986 to 2016. A significant increasing trend of annual and seasonal temperature was found. The temperature change-points for the annual and major rainy season (MRS) were detected in 2001, while for the minor rainy season (mRS) in 1997. A significant decreasing trend, shift, and high variability of rainfall were detected in the downstream part of the ARB. The BR and SNH results showed that the mRS rainfall change-point was in 1998, with a subsequent mean annual decrease of 52.5 mm. The increase (decrease) of rainfall in the annual and MRS was attributable to La Nina (El Nino) events. The significant decreasing trend and change-point of rainfall in the mRS was attributable to the steady warming of the Indian and Atlantic Oceans, local warming, and La Nina events. With this knowledge of the current trends and change-point for rainfall and temperature in the ARB, it is therefore essential that appropriate integrated water management and water-harvesting technologies are established, especially in the downstream areas. Moreover, early detection of El Nino episodes would provide invaluable warning of impending rainfall anomalies in the ARB and would enable better preparations to mitigate its negative effects.

Recent trends in hydroclimate and groundwater levels in a region with seasonal frost cover

In cold climate, the main annual recharge event is spring snowmelt. Projections of groundwater storage hence depend on winter hydroclimate. Winter recharge is a factor of rain, melt and ground frost. Increases in winter rain and melt have already been observed. However, due to complex processes involved in ground frost formation and its natural patchy coverage, the effect of ground frost on recharge is poorly understood.The objective of the study is to improve the understanding of the connection between groundwater storage and hydroclimate in Sweden and Finland, a region with temperate and cold climate, from a seasonal frost cover perspective. In the study, annual, frost-free season and frost season temperature and precipitation trends in the climate regions are compared between one global and two regional reanalysis datasets. Effective precipitation and wet day frequency trends between 1980 and 2010 are compared to groundwater level trends for the same period. Trends are calculated using the Mann-Kendall test and Sen’s slope.The results show that the region is generally experiencing warming and increased precipitation. These trends are strongest in the frost season. Further, the global dataset systematically underestimates median temperatures and precipitation compared to the regional datasets. Effective precipitation trends are generally weak, and indicate wetting in the frost season and drying in the frost-free season. Wet day frequency trends are decreasing significantly on the regional scale in Finland, but with nearly no trends in Sweden. Groundwater levels in southern Finland and southeastern Sweden are declining significantly, while groundwater levels in southwestern Sweden are significantly rising. The results indicate that groundwater trends in southern Finland are linked to wet day frequency and effective precipitation trends in the frost-free season, and that trends in the frost season have no impact on annual groundwater level trends. In southern Sweden, groundwater level trends appear linked to annual and frost-free season trends in effective precipitation, though insignificantly. These trends may be explained by century-scale trends in precipitation drought indices identified by previous studies.

Statistical analysis and temporal trend of annual maximum temperature with teleconnection patterns of different stations in Pakistan

Statistical analysis and temporal trend of annual maximum temperature with teleconnection patterns of different stations in Pakistan

Surface air temperature trends in Kathmandu Valley for 2011-2017

In this study, we reviewed the maximum and minimum temperature trends of the Kathmandu valley over the period of 2011-2017. In addition, the average monthly temperature trends were studied annually for the same period, with the data made available from the Department of Hydrology and Meteorology (DHM) of Nepal. The annual temperature trended in the same direction, with winter temperatures being lower and summer temperatures being higher. The annual average minimum and maximum air temperature trends were found to be slightly rising at 0.097˚C/year and 0.04˚C/year, respectively. The mean air temperature in Kathmandu valley is increasing at a rate of 0.06 degrees Celsius per year, with 2016 being the warmest year and 2012 being the least warm, with annual mean temperatures of 19.82˚C and 19.32˚C, respectively. The temperature difference is much smaller in the summer (less than ~12˚C) than in the winter. &#x0D; BIBECHANA 18 (2) (2021) 95-104

Quantifying the Relative Contribution of Climate Change and Anthropogenic Activities on Runoff Variations in the Central Part of Tajikistan in Central Asia

Quantifying the relative contribution of climate change and anthropogenic activities to runoff alterations are essential for the sustainable management of water resources in Central Asian countries. In the Kofarnihon River Basin (KRB) in Central Asia, both changing climate conditions and anthropogenic activities are known to have caused changes to the hydrological cycle. Therefore, quantifying the net influence of anthropogenic contribution to the runoff changes is a challenge. This study applied the original and modified Mann–Kendall trend test, including the Sen’s slope test, Pettitt’s test, double cumulative curve, and elasticity methods. These methods were applied to determine the historical trends, magnitude changes and change points of the temperature, precipitation, potential evapotranspiration, and runoff from 1950 to 2016. In addition, the contributions of climate change and anthropogenic activities to runoff changes in the KRB were evaluated. The trend analysis showed a significant increasing trend in annual temperature and potential evapotranspiration, while the annual precipitation trend showed an insignificant decreasing trend during the 1950–2016 time period. The change point in runoff occurred in 1986 in the upstream region and 1991 in the downstream region. Further, the time series (1950–2016) is separated into the prior impacted period (1950–1986 and 1950–1991) and post impacted period (1987–2016 and 1992–2016) for the upstream and downstream regions, respectively. During the post impacted period, climate change and anthropogenic activities contributed to 87.96% and 12.04% in the upstream region and 7.53% and 92.47% in the downstream region of the KRB. The results showed that in runoff changes, the anthropogenic activities played a dominant role in the downstream (97.78%) and the climate change impacts played a dominant factor in the upstream region (87.96%). In the land-use type changes, the dominant role was played by construction land, which showed that the area from 248.63 km2 in 1990 increased to 685.45 km2 (175.69%) in 2015. These findings suggest that it is essential to adopt effective steps for the sustainable development of the ecological, hydrological, and social order in the KRB in Central Asia.

Trend Analysis and Variability of Air Temperature and Rainfall in Regional River Basins

Global warming and climate variability are emerging as the foremost environmental problems in the 21st century, especially in developing countries. Full knowledge of key climate change variables is crucial in managing water resources in river basins. This study examines the variability of air temperature and rainfall in the five states of South-Eastern region of Nigeria, using the trend analysis approach. For this purpose, temporal trends in annual rainfall and temperature were detected using non-parametric Mann-Kendall test at 5% significance level. The time series rainfall and temperature data for the period 1922-2008 were analyzed statistically for each state separately. The results of Mann Kendall test showed that there is trend in rainfall in all the capital cities in South-East except Owerri and Awka. It is also observed that the trend of rainfall is decreasing for all the study areas in South-East with the lowest trend rate of -0.1153 mm rainfall occurring in Umuahia. In the case of air temperature, it is observed that the trend is increasing for all the study areas in South-East with the highest trend rate of 0.04698 oC/year occurring in Enugu. These findings provide valuable information for assessing the influence of changes on air temperature and rainfall on water resources and references for water management in the South-Eastern river basin of Nigeria. It also proved that Mann-Kendall technique is an effective tool in analyzing temperature and rainfall trends in a regional watershed. Doi: 10.28991/cej-2021-03091692 Full Text: PDF

Spatiotemporal Analysis of Maximum and Minimum Temperature within a Basin: A Case Study of West-Flowing River Basin of Kutch, Saurashtra and Marwar, India

India has a vast geographic diversity and accordingly has diverse responses to changing climate. The more than expected variations in the temperature are causing alterations in the water cycle and stressing the regional water availability along with agriculture significantly. With the current climate change conditions with globally evident rising temperatures, India has to face the challenge of sustaining its rapid economic growth along with ensuring food security to its increasing mainly agriculture-dependent population. The purpose of this research was to investigate the spatiotemporal variations in maximum and minimum temperature in terms of monthly and annual trends in west-flowing river basin of Kutch, Saurashtra and Marwar (WFR-KSM basin). The trend was calculated and assessed in ProUCL5.0.00 and ArcMap 10 software using 36-year Indian Meteorological Department (IMD) maximum and minimum temperature grid (1° × 1°) data from 1969 to 2004. The direction and magnitude of annual and monthly trends were calculated for every grid using Mann–Kendall (MK) test and Theil–Sen’s (TS) slope. The trends in annual, maximum and minimum temperature were spatially analyzed annually and for every month from January to December. The majority of the area exhibited increasing trend in minimum and maximum temperature annually and in all the months from January to December. In annual maximum temperature, all grids exhibited positive slope ranging from 0.01 to 0.03 degree Celsius per year. In annual minimum temperature, majority of the grids (81.25%) exhibited positive slope ranging from 0.01 to 0.04 degree Celsius per year and none of the grids exhibited negative slope. Monthwise trend in maximum and minimum temperature also indicated rising trend in majority of the grids, with few grids identified with declining trend mainly along the eastern border of the basin.

Airborne pollen trends in Tétouan (NW of Morocco)

Trends of the airborne annual pollen integral (APIn) and pollen season of principal woody and herbaceous plants in Tetouan were analysed over a 10-year monitoring period (2008–2017). Pollen was continuously sampled by means of a 7-day recording volumetric pollen trap by Burkard. Pollen trends were analysed by using Mann–Kendall tests and Sen’s slope. Aerobiological data were correlated with temperature and rainfall. A significant decreasing trend in annual minimum temperature was revealed together with significant decreasing trends in the APIn observed for Cupressaceae, Cannabis, Parietaria, Pinus and Quercus, this being highly significant for Cupressaceae and Pinus. On the contrary, the seasonal intensity of Mercurialis, Morus and Olea showed nonsignificant trends. Besides this, 77% of the studied pollen types showed a tendency to decreasing the peaks value, these trends being significant for Cupressaceae (−204.67 pollen/ m3 per year) and Pinus (−14.33 pollen/ m3 per year). The end of the Quercus pollen season showed a marked tendency to occur earlier across the years (−4.5 days/year) and the start day of Cannabis, Cupressaceae, Pinus and Poaceae to occur later (+ 7.13, 2.33, 1.67 and 2.5 day/year, respectively), shortening the duration of the respective pollen seasons but not with a significant trend. Regarding the association between the pollen season intensity and meteorological parameters, six pollen types showed at least one statistically significant coefficient correlation. The decreasing and significant trend in the intensity of the APIn diminishes also the exposure to airborne pollen for allergic sufferers, having implications in the field of public health. Decreasing trends in annual minimum temperature and the general lack of significant trends and correlation coefficients between the parameters of the pollen season of different pollen types and monthly mean temperatures and rainfall suggest that interannual variability in the data is due to human interventions, deforestation, fires and the opposite response of some species to warming in Fall/Winter and Spring, and this could be the reasons for the observed behaviour in the pollen season.

Rainfall and Temperature Trend Analysis by Mann–Kendall Test and Significance for Rainfed Cereal Yields in Northern Togo

This study investigates the trend in monthly and annual rainfall, minimum and maximum temperature (Tmin and Tmax) using the Mann–Kendall (MK) test and Sen’s slope (SS) method and evaluates the significance of their variability for maize, sorghum and millet yields in northern Togo employing multiple regression analysis. The historical data of Kara, Niamtougou, Mango and Dapaong weather stations from 1977 to 2012 were used. Four non-parametric methods—Alexandersson’s Standard Normal Homogeneity Test (SNHT), Buishand’s Range Test (BRT), Pettitt’s Test (PT) and Von Neumann’s Ratio Test (VNRT)—were applied to detect homogeneity in the data. For the data which were serially correlated, a modified version of the MK test (pre-whitening) was utilised. Results showed an increasing trend in the annual rainfall in all four locations. However, this trend was only significant at Dapaong (p &lt; 0.1). There was an increasing trend in Tmax at Kara, Mango and Niamtougou, unlike Dapaong where Tmax revealed a significant decreasing trend (p &lt; 0.01). Similarly, there was an increasing trend in Tmin at Kara, Mango and Dapaong, unlike Niamtougou where Tmin showed a non-significant decreasing trend (p &gt; 0.05). Rainfall in Dapaong was found to have increased (7.79 mm/year) more than the other locations such as Kara (2.20 mm/year), Niamtougou (4.57 mm/year) and Mango (0.67 mm). Tmax increased by 0.13, 0.13 and 0.32 °C per decade at Kara, Niamtougou and Mango, respectively, and decreased by 0.20 per decade in Dapaong. Likewise, Tmin increased by 0.07, 0.20 and 0.02 °C per decade at Kara, Mango and Dapaong, respectively, and decreased by 0.01 °C per decade at Niamtougou. Results of multiple regression analysis revealed nonlinear yield responses to changes in rainfall and temperature. Rainfall and temperature variability affects rainfed cereal crops production, but the effects vary across crops. The temperature has a positive effect on maize yield in Kara, Niamtougou and Mango but a negative effect on sorghum in Niamtougou and millet in Dapaong, while rainfall has a negative effect on maize yield in Niamtougou and Dapaong and millet yield in Mango. In all locations, rainfall and temperature variability has a significant effect on the cereal crop yields. There is, therefore, a need to adopt some adaptation strategies for sustainable agricultural production in northern Togo.