scholarly journals Long–term spatio–temporal warming tendency in the Vietnamese Mekong Delta based on observed and high–resolution gridded datasets

2019 ◽  
pp. 01-16
Author(s):  
Dang Nguyen Dong Phuong ◽  
Dang Kien Cuong ◽  
Duong Ton Dam ◽  
Nguyen Kim Loi
Keyword(s):  
High Resolution ◽  
Statistical Tests ◽  
Mekong Delta ◽  
Kendall Test ◽  
Trend Detection ◽  
Homogeneity Test ◽  
Spatio Temporal ◽  
Temperature Records ◽  
Slope Estimator ◽  
Increasing Trends

The Vietnamese Mekong Delta is among the most vulnerable deltas to climate–related hazards across the globe. In this study, the annual mean and extreme temperatures from 11 meteorological stations over the Vietnamese Mekong Delta were subjected to normality, homogeneity and trend analysis by employing a number of powerful statistical tests (i.e. Shapiro–Wilk, Buishand Range test, classical/modified Mann–Kendall test and Sen’s slope estimator). As for spatio–temporal assessment, the well–known (0.5° × 0.5°) high–resolution gridded dataset (i.e. CRU TS4.02) was also utilized to examine trend possibilities for three different time periods (i.e. 1901–2017, 1951–2017 and 1981–2017) by integrating spatial interpolation algorithms (i.e. IDW and Ordinary Kriging) with statistical trend tests. Comparing the calculated test–statistics to their critical values (a = 0.05), it is evident that most of the temperature records can be considered to be normal and non–homogeneous with respect to normality and homogeneity test respectively. As for temporal trend detection, the outcomes show high domination of significantly increasing trends. Additionally, the results of trend estimation indicate that the magnitude of increase in minimum temperature was mostly greater than mean and maximum ones and the recent period (1981–2017) also revealed greater increasing rates compared to the entire analyzed period and second half of the 20th century. In general, these findings yield various evident indications of warming tendency in the Vietnamese Mekong Delta over the last three decades.

scholarly journals Spatio-Temporal Trend Mapping of Precipitation and its Extremes Across Afghanistan (1951-2010)

2021 ◽  
Author(s):  
Quarban Aliyar ◽  
Santosh Dhungana ◽  
Sangam Shrestha
Keyword(s):  
Crop Production ◽  
Heavy Precipitation ◽  
Kendall Test ◽  
Eastern Region ◽  
Spring Precipitation ◽  
Significance Level ◽  
Northeastern Region ◽  
Spatio Temporal ◽  
Slope Estimator ◽  
Harsh Climate

Abstract The civil war, harsh climate, tough topography and lack of accurate meteorological stations has limited observed data across Afghanistan. In order to fulfill the gap, this study analyzed the trend in precipitation and its extremes using Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) daily dataset between 1951 to 2010 at the spatial resolution of 0.25˚˟0.25˚. Non-parametric modified Mann-Kendall test and Sen’s slope estimator were employed to detect trend and quantify it at the significance level of 5%. Significant decreasing trends were observed only in small clusters of southwestern regions ranging between 0 to -1.5mm/year and northeastern region between -1.5 to -6 mm/year for the annual time series. Similar trend pattern was observed in spring season decreasing at the rate of -0.15 to 0.54 mm/year in northeastern and 0 to -0.15 mm/year southwestern region. Decrease in spring precipitation is expected to affect crop production especially in northeastern region which host 22 % of the arable area. Increasing trend in eastern region at maximum of 0.16 mm/year was observed which could intensify the flooding events. Trend analysis of extreme precipitation indices indicated similar spatial distribution to the mean precipitation, concentrated around southwestern, northeastern, and eastern regions. Increasing frequency of consecutive dry days in western region and very heavy precipitation (R10mm) and extremely heavy precipitation (R20mm) in eastern region are fueling the occurrence of droughts and floods respectively. Taking these findings of erratic nature of rainfall and extreme events into consideration for sustainable management of water resources would be fruitful.

scholarly journals TREND DETECTION OF METROLOGICAL DROUGHT IN NORTH OF IRAQ

2021 ◽  
Vol 25 (3) ◽  
pp. 60-73
Author(s):  
Ihsan F. Hasan ◽  
Keyword(s):  
Time Series ◽  
Standardized Precipitation Index ◽  
Meteorological Drought ◽  
Kendall Test ◽  
Northern Region ◽  
Trend Detection ◽  
Precipitation Data ◽  
Study Region ◽  
Slope Estimator ◽  
Mild Drought

This study presents an analysis of meteorological drought using multi time-scales of Standardized Precipitation Index SPI (6, 9 and 12 month), based on observed 49-year daily mean precipitation data records at 11 stations over the Northern region of Iraq. The detection of drought trends in results of SPI analysis was studied to identify whether there is any increase or decrease in the severity of drought at the selected meteorological Stations; Mann Kendall test and Sen's slope estimator were used to detect statistically significant trends. The results indicate that there is a statistically significant decreasing trend of SPI time series at 5% significant level in most of the selected stations. Based on drought categories the meteorological drought in the study region can be classified as mild drought.

scholarly journals Analysis of Non-Parametric Trend and Climatic Parameter Homogeneity Tests in a Data-scarce Region: A Spatio-Temporal Perspective in the Tawang River Basin, Eastern Himalayas

2021 ◽  
Author(s):  
Juna Probha Devi ◽  
Chandan Mahanta ◽  
Anamika Barua
Keyword(s):  
Water Resource Management ◽  
Management Strategies ◽  
Kendall Test ◽  
Climate Impact ◽  
Mean Annual Precipitation ◽  
Homogeneity Test ◽  
Eastern Region ◽  
Positive Trend ◽  
Temporal Perspective ◽  
Spatio Temporal

Abstract This study is aimed at studying long–term historical and future (1950-2099) trends for the RCP 4.5 and RCP 8.5 on approximately 30-year timescale at annual and seasonal for precipitation and at annual, seasonal, monthly, and diurnal temperature range (DTR) for temperature maximum (T_max), temperature minimum (T_min) variations using statistical trend analysis techniques– Mann–Kendall test (MK) and Sen's slope estimator (S) and the homogeneity test using Pettitt’s test. The study is carried out in three spatial points across the Tawang Chu in the district of Tawang, Arunachal Pradesh. The summer mean precipitation for RCP 4.5 (2006-2065) shows a positive trend with a rise in precipitation between 1.56 mm to 9.94 mm in all the study points. The mean annual precipitation statistics for all the points show an increase of RCP 4.5 in 2006-2052 and 2053-2099 timescale. Both RCP 4.5 and 8.5 scenarios exhibit a uniform rise in T_min and T_max during investigation. For all the points, the results likewise reveal a rising trend in mean annual T_min and T_max. Still, the inter-decadal temperature statistical analysis shows that the increase in mean annual T_min is greater than the increase in T_max, indicating a decreasing trend in DTR. It is anticipated that this study's outcomes will contribute to a better understanding of the relationship between change in climate and the regional hydrological behaviour and will be benefitting the society to develop a regional strategy for water resource management, can serve as a resource for climate impact research scope- assessments, adaptation, mitigation, and disaster management strategies for India's north-eastern region.

scholarly journals Climate change and its implications for rainfed agriculture in Ethiopia

2020 ◽  
Author(s):  
Desalew Meseret Moges ◽  
H. Gangadhara Bhat
Keyword(s):  
Coupled Model ◽  
Daily Rainfall ◽  
Kendall Test ◽  
Future Climate ◽  
Rainfed Agriculture ◽  
Rcp Scenarios ◽  
Precipitation Concentration Index ◽  
Spatio Temporal ◽  
Temperature Records ◽  
Climate Analysis

Abstract This study aims to investigate the spatio-temporal variability and trends in climate and its implications for rainfed agriculture in the Rib watershed, north-western highland Ethiopia from 1986 to 2050. The daily rainfall and temperature records for the period 1986–2017 were used to detect the variability and trends of the current climate using the coefficient of variation, precipitation concentration index, Mann–Kendall test, and Sen's slope estimator. On the other hand, future climate changes (2018–2050) were analyzed based on the Coupled Model Intercomparison Project version 5 (CMIP5) model outputs under under two representative concentration pathway (RCP) scenarios, RCP 4.5 and 8.5. The results showed high inter-seasonal and inter-annual variability of rainfall and temperature in the studied watershed over the last four decades. The annual and Kiremt (June–September) rainfall showed a generally increasing trend, while the Belg (March–May) rainfall exhibited a decreasing trend between 1986 and 2017. Conversely, the minimum, maximum and mean temperature demonstrated increasing trends over the study period although most of the detected trends were statistically insignificant at 5 and 10% level of significance. Future climate analysis results showed an increase in future temperature and annual and Kiremt rainfall while Belg rainfall declined.

scholarly journals Maximum and Minimum Temperature Trends Variation over Northern and Southern Part of Bangladesh

2015 ◽  
Vol 6 (2) ◽  
pp. 83-88 ◽  
Author(s):  
NM Refat Nasher ◽  
MN Uddin
Keyword(s):  
Minimum Temperature ◽  
Geographical Location ◽  
Kendall Test ◽  
Maximum Temperature ◽  
Coastal City ◽  
Post Monsoon ◽  
Temperature Trends ◽  
Two Cities ◽  
Slope Estimator ◽  
Increasing Trends

Temperature is one of the pivotal climatic variables in our world climate literature. In the present study monthly, seasonal and yearly highest maximum and lowest minimum temperatures of two cities were analyzed. Mann-Kendall test and Sen’s Slope Estimator were used to determine the trend and slope magnitude. Chittagong, as the coastal city and Rajshahi, as Barind track were selected as a study area due to its respective geographical location. Such types of data of 52 years for Chittagong as well as 48 years for Rajshahi were collected from Bangladesh Meteorological Department (BMD). Monthly highest maximum and lowest minimum temperature data from 1950-2002 for Chittagong and 1964-2012 for Rajshahi were used for analysis. In Rajshahi, significant rising trends were found in highest maximum post-monsoon temperature, lowest minimum monsoon temperature and highest maximum temperature from July to October, June and August for lowest minimum temperature. Falling trends were found in annual highest maximum and lowest minimum temperatures, pre-monsoon highest maximum temperature, lowest minimum winter temperature and January lowest minimum temperature. For Chittagong, significant increasing trends found in post-monsoon highest maximum temperature, June to December highest maximum temperature except July and December lowest minimum temperature. No significant decreasing trend was found in Chittagong.DOI: http://dx.doi.org/10.3329/jesnr.v6i2.22101 J. Environ. Sci. & Natural Resources, 6(2): 83-88 2013

scholarly journals Spatio-Temporal Analysis of Drought Indicated by SPEI over Northeastern China

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 908 ◽  
Author(s):  
Lei Ye ◽  
Ke Shi ◽  
Hairong Zhang ◽  
Zhuohang Xin ◽  
Jing Hu ◽  
...  
Keyword(s):  
Water Resource Management ◽  
Kendall Test ◽  
Temporal Analysis ◽  
Northeastern China ◽  
Jilin Province ◽  
Liaoning Province ◽  
Songhua River ◽  
Liaohe River ◽  
Spatio Temporal ◽  
Increasing Trends

Drought is a natural extreme climate event which occurs in most parts of the world. Northeastern China is one of the major agricultural production areas in China and also a typical vulnerable climate zone. To understand the spatio-temporal characteristics of drought over northeastern China, we first assessed the trends of precipitation and temperature. Drought events were then characterized by Standardized Precipitation Evapotranspiration Index over various temporal scales. The Trend Free Prewhitening Mann–Kendall test and distinct empirical orthogonal function, were used to investigate the trends and spatio-temporal patterns of droughts. The results indicate precipitation increasing trends are mostly detected in Heilongjiang and Jinling provinces, however, the majority of the trends are insignificant. Temperature increasing trends are detected over the entire northeastern China and most of them are significant. Decreasing drought trends are observed in Heilongjiang province and some bordering area in Jilin province, whereas increasing trends are noticed in Liaoning province and some bordering area in Jilin province. Two main sub-regions of drought variability—the Liaohe River Plain and the Second Songhua River basin (LS region), and the Songnen Plain and the Lesser Hinggan Mountains (SL region) are identified, and the detected droughts for the two sub-regions correspond well with recorded drought loss. The results will be beneficial for regional water resource management and planning, agriculture production, and ecosystem protection in northeastern China.

scholarly journals Long-term trend analysis of climatic variables and reference evapotranspiration over different urban areas in Tunisia

2019 ◽  
Vol 6 (12) ◽  
pp. 189-201
Author(s):  
Basma Latrech ◽  
Hiba Ghazouani ◽  
Lasram Asma ◽  
Boutheina M. Douh ◽  
Mansour Mohsen ◽  
...  
Keyword(s):  
Trend Analysis ◽  
Urban Areas ◽  
Kendall Test ◽  
Climatic Variables ◽  
Upward Trend ◽  
Slope Estimator ◽  
Increasing Trends ◽  
Regression Tests ◽  
Long Term Trend

In this study, the trend analysis of annual climatic variables including Tmax, Tmin, Tmean, RHmean, WS and SR as well as FAO-56 PM ET0 were investigated in three locations in Tunisia during 1984-2007. The Mann-Kendall Test, the Sen's Slope Estimator and linear regression tests were used for the analysis. The obtained results showed a significant increasing trends (a < 0.001) and (a < 0.01) in annual Tmax, Tmin and Tmean at all the considered locations. However, Tmin increase faster than Tmax with a slope of magnitudes ranging between 0.057 to 0.1 oC year-1. For RHmean, a non-significant tendency of decrease was observed in Chott-Mariem station. However, significantly increasing trends were found for Kelibia and Tunis Carthage. Concerning the WS variable, a tendency of decrease is observed during the study period for all the stations. Nevertheless, the statistical analysis of decreasing tendency of wind speed varied from non-significant for Tunis Carthage to highly significant (a <= 0.001) at Chott-Mariem and Kelibia. Despite the highly significant upward trend of temperature, the temporal pattern of mean annual FAO56 PM-ET0, over the different stations, did not exhibit any significant trend except for Kelibia station.

 Spatio-temporal characterization of rainfall using an innovative trend and discrete wavelet transformation approaches in Bhakra catchment, India

2021 ◽  
Author(s):  
Neha Gupta ◽  
Sagar Chavan
Keyword(s):  
Extreme Rainfall ◽  
Kendall Test ◽  
Mitigation Measures ◽  
Discrete Wavelet ◽  
Precipitation Concentration Index ◽  
Seasonal Time Series ◽  
Seasonal Basis ◽  
Spatio Temporal ◽  
Water Resources Projects ◽  
Slope Estimator

&lt;p&gt;Using a high-resolution daily gridded rainfall data of 0.25&amp;#176; from the Indian Meteorological Department (IMD), the present study investigates the detailed characteristics of rainfall in the Bhakra Catchment from 1901 to 2019. The long term spatial and temporal rainfall variations in Bhakra Catchment are not well explored. The spatial pattern of rainfall regimes in this catchment is identified by estimating index like the precipitation concentration index (PCI) and seasonality index (SI). Extreme rainfall trends on annual and seasonal basis are examined using the innovative trend analysis (ITA) method. Reliability of ITA was assessed by comparing them with widely applied Mann&amp;#8211;Kendall (MK) or modified Mann&amp;#8211;Kendall (mMK) test results. Furthermore, the change in two halves of rainfall series is estimated using percent bias technique for estimating changes in rainfall. Changes in slopes are estimated by using Sen&amp;#8217;s slope estimator (Q). Discrete wavelet transform (DWT) in conjunction with Sequential Mann&amp;#8211;Kendall test (SQMK) is employed to find out the dominant periodicity in rainfall patterns. The effectiveness of the graphical method in qualitative analysis can be seen, while DWT is found efficient in identifying periodicity. Both positive and negative trends are detected in annual and seasonal time series over the study area. The outcomes of this study may be helpful in the planning and management of water resources projects in the catchment along with the planning of mitigation measures to alleviate the effects of climate change under extreme rainfall conditions.&lt;/p&gt;

Flow Indices Variability in Humid Subtropical of Upper Awash River Basin, Ethiopia

2021 ◽  
Author(s):  
Sintayehu Yadete Tola ◽  
Amba Shetty
Keyword(s):  
Water Resources ◽  
River Basin ◽  
Decadal Variability ◽  
Statistical Tests ◽  
Kendall Test ◽  
Change Points ◽  
Watershed Hydrology ◽  
Time Step ◽  
Awash River Basin ◽  
Slope Estimator

Abstract Investigating the hydrological extremes indices at high resolutions describing the whole stream spectrum is essential for the comprehensive assessment of watershed hydrology. The study focuses on a wide-ranging assessment of river discharge in annual mean, peak, and high and low percentiles flow at the Upper Awash River basin, Ethiopia. Statistical tests such as coefficient of variation, flood variability to characterize the flow regime and Tukey’s test to detect decadal variability. Modified Mann-Kendall test, Sen’s slope estimator, innovative trend analysis and Pettitt’s test were applied to see trends, and change points in time series, respectively. Results showed that the basin was characterized by moderate to high variability. Spatially, main tributaries showed a higher variability, almost in all-time step and characterized by higher flood variability. The large discharge receiving rivers resulted in a moderate to high and lower discharge variability. Test statistics resulted in a positive increasing trend dominating most time scales at a 5% significant level and higher magnitude of slope trend in peak flow. A negative trends were also exhibited. Hombole main outlet site experienced decreasing trend in high percentile flow. In comparison, complete trend direction agreements were observed (except in few series). Flow indices showed an upward shift and downward shift mainly in the year 2000s and the significant decadal variation resulted in comparable with change points. The study provides an understanding of water resources variability, which will be necessary to apply operational water resources strategies and management to restrain the potential impacts of variability nature of the streamflow.

scholarly journals Spatio-temporal Variability and Trends in Rainfall and Temperature in Anger watershed, Southwestern Ethiopia

2021 ◽  
Vol 5 (1) ◽  
pp. 462-472
Author(s):  
Gemechu Yigezu Ofgeha ◽  
Muluneh Woldetsadik Abshire
Keyword(s):  
Temporal Trends ◽  
Kendall Test ◽  
Annual Rainfall ◽  
Small Scale ◽  
Rainfall Trend ◽  
High Rainfall ◽  
Southwestern Ethiopia ◽  
Spatio Temporal ◽  
Small Scale Farmers ◽  
Increasing Trends

Insights to broadly argued research gap on lack of climate studies at micro-scale considering unique features of an area, this paper intended to examine agro-ecological level spatio-temporal trends and variability in rainfall and temperature in Anger watershed of southwestern Ethiopia. The gridded data managed by the Ethiopia National Meteorological Services Agency (NMSA) for 1983-2018 were used. The Mann-Kendall test for trend analysis and different variability measures were used. Questionnaire and FGD data on community perceptions gathered from 214 households and elders were analysed descriptively and qualitatively. The study reveals the consistent increasing trends in temperature; and high variability and insignificant but increasing rainfall trend. The trends and variability show spatio-temporal differences along agro-ecologies. The watershed is characterized by moderate to high rainfall coefficient of variations, significant years of high rainfall concentration, and considerable negative annual rainfall anomalies; that the variability was severe in woinadega followed by kolla agro-ecology. Although, the perceptions on trends, variability and its implications show difference across agro-ecology, the propensity to increased temperature, unclear rainfall trend and significant inter-annual and seasonal variability were witnessed. Unpredictability of rainfall time, concentrations in kiremt, and unexpected rain during harvesting was major challenges resulting multifaceted impacts on the small-scale farmers’ livelihoods.

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