Long Term Trend Analysis of Upstream and Middle-Stream River in Langat Basin, Malaysia

Abstract. Historically droughts have had a huge impact on conditions of life on earth. With growing population of the Earth the impacts of droughts grow even more severe. Human beings are also affected by drought like other life forms. Studies have taken place to understand and thereby mitigate the effects of these climatological phenomena on humans. The study of drought trends is of great importance since it is directly related to food and water resources availability, that could become scarce in case of droughts. In this paper by using SPI, SSI and TSDI indices we try to understand the drought behaviour in Iran using Mann-Kendall and Sen’s slope methods. Canonical correlation analysis between SPI and SSI shows a positive correlation for the most parts of Iran. Also the correlation between TSDI and SPI/SSI is positive for majority of the Iran. Drought trends in Iran are analysed using Mann-Kendall and Sen’s slope estimator with 95% confidence level.

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Rainfall trend and variability over Opak River basin, Yogyakarta, Indonesia

Journal of the Civil Engineering Forum ◽

10.22146/jcef.60628 ◽

2020 ◽

Vol 1000 (1000) ◽

Author(s):

Wakhidatik Nurfaida ◽

Hendra Ramdhani ◽

Takenori Shimozono ◽

Indri Triawati ◽

Muhammad Sulaiman

Keyword(s):

River Basin ◽

Water Resource ◽

Rainfall Intensity ◽

Kendall Test ◽

Rainfall Data ◽

Positive Trend ◽

Sen’S Slope Estimator ◽

Sen’S Slope ◽

Slope Estimator

Rainfall intensity seems to be increasing nowadays due to climate change as presented in many studies of both global and regional scale. Consequently, cities worldwide are now more vulnerable to flooding. In Indonesia, increasing frequency of floods was reported for the past decades by The National Agency for Disaster Countermeasure (BNPB). To understand the rainfall changes, long-term trend evaluation over a specific area is then crucial due to the large variability of spatial and temporal rainfall distribution. This study investigates the homogeneity and trend of rainfall data from 20 stations over the Opak River basin, Yogyakarta, Indonesia. A long-term ground observation rainfall data whose period varies from 1979 to 2019 were analyzed. Non-parametric Mann – Kendall test was applied to assess the trend, while the magnitude was calculated using the Sen’s slope estimator. An increasing annual maximum of daily rainfall intensity was observed at four stations on a 0.95 confidence level based on the Mann – Kendall test, while the Sen’s slope estimator shows a positive trend at almost all stations. The trend of heavy rainfall frequency was also found to be significantly increased, with only one station showed a decreasing trend. Furthermore, this paper also described the spatial and temporal rainfall variability. Positive trend was mostly found during the rainy season, while the negative trend occurred during the dry season. This could pose a challenge for water resource management engineering and design, such as water supply systems or reservoir management. Understanding this phenomena will benefit hydrologists in preparing future water resource engineering and management.

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Spatiotemporal Trend Analysis of the Mean Annual Rainfall in Senegal

European Scientific Journal ESJ ◽

10.19044/esj.2016.v12n12p231 ◽

2016 ◽

Vol 12 (12) ◽

pp. 231 ◽

Cited By ~ 5

Author(s):

Lamine Diop ◽

Ansoumana Bodian ◽

Dior Diallo

Keyword(s):

Kendall Test ◽

Annual Rainfall ◽

Positive Trend ◽

Sen’S Slope Estimator ◽

Small Areas ◽

Sen’S Slope ◽

Trend Magnitude ◽

North East ◽

Spatiotemporal Trends ◽

Slope Estimator

The spatiotemporal trends of annual rainfall in Senegal during 1940 - 2013 were investigated using the Mann–Kendall test and Theil–Sen’s slope estimator. Theil and Sen's slope estimator test was used for finding the magnitude of change over a time period. Inverse Weight Distance (IDW) technique in Arc GIS 10.2 was used to investigate spatial patterns of the trends over the entire country. For the period 1940-2013, the results of the analysis showed negative trends in annual rainfall at the whole country except for the Bakel station which exhibits a positive trend but not significant. While for the period 1984 - 2013, all the stations show a positive trend with 07 out of 22 stations exhibiting a significant trend at the 95% confidence interval. The spatial distribution of trend during the period 1940- 2013 showed a significant negative trend in the whole study of area except small areas located at the extreme South Est and West as well as North East and West. The trend magnitude varies between -4.41mm/year to 1.34 mm for the period 1940-2013 with a maximum negative magnitude at the Tambacounda station. For 1984-2013, the trend magnitude is positive for the whole country with values varying between 2.67 mm/year at Goudiry and 12.2 mm/year at Ziguinchor. Magnitudes are greater than 5 mm/year, for stations with significant positive trend.

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Water vapor pressure trends in south and southwest Iran

MAUSAM ◽

10.54302/mausam.v68i2.636 ◽

2021 ◽

Vol 68 (2) ◽

pp. 335-348

Author(s):

YOUNES KHOSRAVI ◽

HASAN LASHKARI ◽

HOSEIN ASAKEREH

Keyword(s):

Time Series ◽

Water Vapor ◽

Vapor Pressure ◽

Water Vapor Pressure ◽

Sen’S Slope Estimator ◽

Sen’S Slope ◽

Ground Station ◽

Mk Test ◽

Slope Estimator ◽

The Persian Gulf

Recognitionanddetectionofclimaticparameters inhave animportant role inclimate change monitoring. In this study, the analysis of oneofthe most importantparameters, water vapor pressure (WVP), was investigated. For this purpose, two non-parametric techniques, Mann-Kendall and Sen's Slope Estimator, were used to analyze the WVP trend and to determine the magnitude of the trends, respectively. To analyze these tests, ground station observations [10 stations for period of 44 years (1967-2010)] and gridded data [pixels with the dimension of 9 × 9 km over a 30-year period (1981-2010)] in South and SouthwestofIran were used. By programming in MATLAB software, the monthly, seasonal and annual WVP time series were extracted and MK and Sen's slope estimator tests were done. The results of monthly MK test on ground station observations showed that the significant downward trends are more considerable than significant upward trends. It also showed that the WVP highest frequency was more in warm months, April to September and the highest frequency of significant trends slope was in February and May. The spatial distribution of MK test of monthly gridded WVP time series showed that the upward trends were detected mostly in western zone and near the Persian Gulf in August. On the other hand, the downward trends through months. The maximum and minimum values of positive trends slope occurred in warm months and cold months, respectively. The analysis of the MK test of the annual WVP time series indicated the upward significant trends in the southeast and southwest zones of study area.

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Analysis of long-term climatic changes at Hodeidah-Yemen during the period between 1984 and 2019

10.21203/rs.3.rs-897613/v2 ◽

2021 ◽

Author(s):

Abkar Ali Iraqi ◽

AbdAlla Mohammed AbdAlla

Keyword(s):

Climatic Variability ◽

Arab Country ◽

Climatic Fluctuations ◽

Sen’S Slope Estimator ◽

Sen’S Slope ◽

Mk Test ◽

Slope Estimator ◽

Annual Means ◽

C 50 ◽

Increasing Trends

Abstract Yemen is one of the Arab country that is vulnerable to climate changes, and this is clear from the indicators of impact on water resources, coastal zone environments, etc. This work focuses on studying the climatic variability at Hodeidah city-Yemen during the period between 1984 and 2019. This study aimed to characterize trends in mean monthly, seasonal and annual temperature. To attain these objectives the collected data were analyzed using both parametric (linear regression) and non-parametric (Mann–Kendall, Spearman and Sen's slope estimator tests) methods to detect the trend and the magnitudes of rates of changes of temperature over time. Analysis of data indicates clear climatic fluctuations of temperature. The annual means of temperature during the period of study were varied between 26.9°C and 30.1°C. The warmest years were observed during the more recent years of the study period ( 2005 to 2018). The increasing rate of annual temperature is about + 0.075°C /year, + 0.37°C/5year, + 0.75°C/decade ,+2.53°C, over the whole period of study(1985 to 2019), + 3.7°C/50 year and increase to + 4.85°C in 2050. On a monthly timescale, there are similar magnitudes of rates of change from December to September with highest rates in October and November. The results also showed that most months and seasons have significant positive trends in temperature and (Z-α/2) values of the MK Test > 1.96 and positive value of Sen’s slope estimator indicates significant an increasing trend towards warmer years. Anomalies of temperature confirm significant increasing trends towards warmer years (2000s to 2019).

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Satellite-based study of physico-optical properties of aerosols over a westernmost location of Brahmaputra valley

Satellite Oceanography and Meteorology ◽

10.18063/som.v3i2.699 ◽

2018 ◽

Vol 3 (2) ◽

Author(s):

Jhuma Biswas 1

Keyword(s):

Atmospheric Aerosols ◽

Monsoon Season ◽

Cloud Condensation Nuclei ◽

Winter Season ◽

Earth Observing System ◽

Brahmaputra Valley ◽

Increasing Trend ◽

Long Term Trend ◽

Term Analysis

This study examines the long term trend of the radiatively active atmospheric aerosols which can influence the Earth’s energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei. MODIS sensor on board the NASA Earth Observing System Terra and Aqua satellite based Aerosol Optical Depth (AOD) data are used for long term analysis of aerosols over Bongaigaon, Assam for the period August, 2002 to March, 2017. Highest AOD values are observed in pre-monsoon (March-May) season due to long range transportation as well as intense biomass burning activities especially as a part of Jhum cultivation. In general, AOD values are low in post-monsoon (October-November) season which may be due to wash out of aerosols by rain in the preceding months without enough replacement. The monthly AOD values vary from its highest value 0.949 in April, 2016 to its lowest value 0.107 in November, 2002 for the study period. From the comparison of MODIS Terra and Aqua AOD at 550 nm, it is clearly seen that generally Terra AOD at 10:30 hr is higher than the Aqua AOD at 13:30hr. A slowly increasing trend of both Aqua and Terra AOD at 550 nm is observed over the study location. The observed Ångström exponent value varies from its minimum value in monsoon season to its maximum value in winter season. With increasing AOD values, horizontal visibility decreases over Bongaigaon.

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Rainfall trend analysis using Mann-Kendall and Sen’s slope estimator test in West Kalimantan

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/893/1/012006 ◽

2021 ◽

Vol 893 (1) ◽

pp. 012006

Author(s):

F Aditya ◽

E Gusmayanti ◽

J Sudrajat

Keyword(s):

Climate Change ◽

Rainfall Variability ◽

Annual Rainfall ◽

Sen’S Slope Estimator ◽

West Kalimantan ◽

Rainfall Analysis ◽

Sen’S Slope ◽

Rainfall Trends ◽

Slope Estimator ◽

The Impact

Abstract Climate change has been a prominent issue in the last decade. Climate change on a global scale does not necessarily have the same effect in different regions. Rainfall is a crucial weather element related to climate change. Rainfall trends analysis is an appropriate step in assessing the impact of climate change on water availability and food security. This study examines rainfall variations and changes at West Kalimantan, focusing on Mempawah and Kubu Raya from 2000-2019. The Mann-Kendall (MK) and Sen's Slope estimator test, which can determine rainfall variability and long-term monotonic trends, were utilized to analyze 12 rainfall stations. The findings revealed that the annual rainfall pattern prevailed in all locations. Mempawah region tends to experience a downward trend, while Kubu Raya had an upward trend. However, a significant trend (at 95% confidence level) was identified in Sungai Kunyit with a slope value of -33.20 mm/year. This trend indicates that Sungai Kunyit will become drier in the future. The results of monthly rainfall analysis showed that significant upward and downward trends were detected in eight locations. Rainfall trends indicate that climate change has occurred in this region.

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Analysis of long-term climatic changes at Hodeidah-Yemen during the period between 1984 and 2019

10.21203/rs.3.rs-897613/v1 ◽

2021 ◽

Author(s):

Abkar Ali Iraqi ◽

AbdAlla Mohammed AbdAlla

Keyword(s):

Climatic Variability ◽

Arab Country ◽

Climatic Fluctuations ◽

Sen’S Slope Estimator ◽

Sen’S Slope ◽

Mk Test ◽

Slope Estimator ◽

Annual Means ◽

C 50 ◽

Increasing Trends

Abstract Yemen is one of the Arab country that is vulnerable to climate changes, and this is clear from the indicators of impact on water resources, coastal zone environments, etc. This work focuses on studying the climatic variability at Hodeidah city-Yemen during the period between 1984 and 2019. This study aimed to characterize trends in mean monthly, seasonal and annual temperature. To attain these objectives the collected data were analyzed using both parametric (linear regression) and non-parametric (Mann–Kendall, Spearman and Sen's slope estimator tests) methods to detect the trend and the magnitudes of rates of changes of temperature over time. Analysis of data indicates clear climatic fluctuations of temperature. The annual means of temperature during the period of study were varied between 26.9°C and 30.1°C. The warmest years were observed during the more recent years of the study period ( 2005 to 2018). The increasing rate of annual temperature is about + 0.075°C /year, + 0.37°C/5year, + 0.75°C/decade ,+2.53°C, over the whole period of study(1985 to 2019), + 3.7°C/50 year and increase to + 4.85°C in 2050. On a monthly timescale, there are similar magnitudes of rates of change from December to September with highest rates in October and November. The results also showed that most months and seasons have significant positive trends in temperature and (Z-α/2) values of the MK Test > 1.96 and positive value of Sen’s slope estimator indicates significant an increasing trend towards warmer years. Anomalies of temperature confirm significant increasing trends towards warmer years (2000s to 2019).

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Interpreting the seasonal and long-term trend of nitrate in both groundwater and spring water in a typical headwater wetland with well-defined groundwater flow pathways

Water Science & Technology Water Supply ◽

10.2166/ws.2016.047 ◽

2016 ◽

Vol 16 (5) ◽

pp. 1327-1338

Author(s):

Yingjie Cao ◽

Changyuan Tang ◽

Zhiwei Han ◽

Sako Yoko ◽

Xing Li

Keyword(s):

Groundwater Flow ◽

Soil Water ◽

Residence Time ◽

Spring Water ◽

Hydrological Process ◽

Term Trend ◽

Increasing Trend ◽

Flow Pathways ◽

Long Term Trend

Timescale problems of nitrate behavior (i.e. seasonal variation and long-term trend) in headwater are closely related to its hydrological process. In a typical agricultural headwater catchment in the Chiba prefecture, Japan, the groundwater nitrate concentration showed an increasing trend, while for spring water, a substantial decreasing trend was observed during our monitoring period. Two key issues, (1) identification of multiple flow pathways and (2) evaluation of the residence time for different pathways, were emphasized to reveal the factors controlling the different patterns of nitrate trend. Three major flow pathways including vertical soil water flow (VF), lateral groundwater flow (LG) and deep groundwater flow (DG) along the upland-slope-valley were differentiated. Different timescales of three flow pathways were identified. The residence time of VF was calculated as 9–10 years based on the soil water budget equation and the apparent age of LG was estimated as 41 years by chlorofluorocarbon (CFC) traces. The increasing trend of NO3− in groundwater agreed well with the historical nitrate loading, and the decreasing trend of NO3− in spring was mainly influenced by nitrate behavior of LF, which substantially decreased due to reduction of nitrogen fertilizer loadings since 2000.

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