scholarly journals Long-Term Rainfall Trends and Their Variability in Mainland Portugal in the Last 106 Years

Climate ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 146
Author(s):  
Maria Manuela Portela ◽  
Luis Angel Espinosa ◽  
Martina Zelenakova
Keyword(s):  
Temporal Variability ◽  
Annual Rainfall ◽  
Small Country ◽  
Rain Gauges ◽  
Mainland Portugal ◽  
Mk Test ◽  
Rainfall Trends ◽  
Slope Estimator ◽  
European Coast

This study addresses the long-term rainfall trends, their temporal variability and uncertainty over mainland Portugal, a small country on the most western European coast. The study was based on monthly, seasonal and annual rainfall series spanning for a period of 106 years, between October 1913 and September 2019 (herein after referred to as global period), at 532 rain gauges evenly distributed over the country (c.a. 6 rain gauges per 1000 km2). To understand the rainfall behavior over time, an initial sub-period with 55 years and a final sub-period with 51 years were also analyzed along with the global period. The trends identification and the assessment of their magnitude were derived using the nonparametric Mann-Kendall (MK) test coupled with the Sen’s slope estimator method. The results showed that after the initial sub-period with prevailing increasing rainfall, the trends were almost exclusively decreasing. They were also so pronounced that they counterbalanced the initial rainfall increase and resulted in equally decreasing trends for the global period. The study also shows that approximately from the late 1960s on, the rainy season pattern has changed, with the last months prior to the dry season showing a sustained decrease of their relative contributions to the annual rainfalls. Overall, the results support the hypothesis of less uncertainty on the pronounced decrease of rainfall over mainland Portugal in recent years, which is expected to continue. They also show that the asymmetry between a less wet North, yet still wet, and an arid South is becoming much more marked.

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

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.

scholarly journals Long term effect of climate change on rainfall in northwest Iraq

2014 ◽  
Vol 4 (3) ◽  
Author(s):  
Nadhir Al-Ansari ◽  
Mawada Abdellatif ◽  
Salahalddin Ali ◽  
Sven Knutsson
Keyword(s):  
Climate Change ◽  
Management Strategies ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Water Shortages ◽  
Intergovernmental Panel ◽  
Continuous Decrease ◽  
Rainfall Trends ◽  
Semi Arid Region

AbstractMiddle East, like North Africa, is considered as arid to semi-arid region. Water shortages in this region, represents an extremely important factor in stability of the region and an integral element in its economic development and prosperity. Iraq was an exception due to presence of Tigris and Euphrates Rivers. After the 1970s the situation began to deteriorate due to continuous decrease in discharges of these rivers, are expected to dry by 2040 with the current climate change. In the present paper, long rainfall trends up to the year 2099 were studied in Sinjar area, northwest of Iraq, to give an idea about its future prospects. Two emission scenarios, used by the Intergovernmental Panel on Climate Change (A2 and B2), were employed to study the long term rainfall trends in northwestern Iraq. All seasons consistently project a drop in daily rainfall for all future periods with the summer season is expected to have more reduction compared to other seasons. Generally the average rainfall trend shows a continuous decrease. The overall average annual rainfall is slightly above 210 mm. In view of these results, prudent water management strategies have to be adopted to overcome or mitigate consequences of future severe water crisis.

Rainfall trends in hindsight and in foresight

2020 ◽  
Author(s):  
Theano Iliopoulou ◽  
Demetris Koutsoyiannis
Keyword(s):  
Daily Rainfall ◽  
Predictive Performance ◽  
Predictive Modelling ◽  
Annual Rainfall ◽  
Methodological Framework ◽  
Rainfall Trends ◽  
Out Of Sample ◽  
Linear Trends

<p>Trends are customarily identified in rainfall data in the framework of explanatory modelling. Little insight however has been gained by this type of analysis with respect to their performance in foresight. In this work, we examine the out-of-sample predictive performance of linear trends through extensive investigation of 60 of the longest daily rainfall records available worldwide. We devise a systematic methodological framework in which linear trends are compared to simpler mean models, based on their performance in predicting climatic-scale (30-year) annual rainfall indices, i.e. maxima, totals, wet-day average and probability dry, from long-term daily records. Parallel experiments from synthetic timeseries are performed in order to provide theoretical insights to the results and the role of parsimony in predictive modelling is discussed. In line with the empirical findings, it is shown that, prediction-wise, simple is preferable to trendy.</p>

Less rain and rainy days - lessons from 45 years of rainfall data (1971 to 2015) in the Kathmandu Valley, Nepal

2021 ◽  
Author(s):  
Rajaram Prajapati ◽  
Rocky Talchabhadel ◽  
Priya Silwal ◽  
Surabhi Upadhyay ◽  
Brandon Ertis ◽  
...  
Keyword(s):  
Temporal Variability ◽  
Temporal Trends ◽  
Daily Rainfall ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Kathmandu Valley ◽  
Light Rain ◽  
Mk Test ◽  
Spatio Temporal ◽  
Rainy Days

Abstract Understanding spatio-temporal variability in rainfall patterns is crucial for evaluating water balances needed for water resources planning and management. This paper investigates spatio-temporal variability in rainfall and assesses the frequency of daily rainfall observations from seven stations in the Kathmandu Valley, Nepal, from 1971–2015. Daily rainfall totals were classified into five classes, namely, A (light rain, daily rainfall < 10 mm in a day), B (between 10–50 mm), C (between 50–100 mm), D (between 100–150 mm) and E (> 150 mm). The relationship between daily rainfall and rainfall frequency of various rainfall rate classes were analysed. Kriging method was used for interpolation in interpreting seasonal and annual rainfall data and spatial maps were generated using QGIS. The Mann-Kendall (MK) test was performed to determine the temporal trends and Theil-Sen’s (TS) slope estimator was used in quantifying the magnitude of trends. Mountain stations showed a decreasing trend in rainfall for all seasons, ranging from − 8.4 mm/year at Sankhu to -21.8 mm/year at Thankot, whereas, a mixed pattern was found on the Valley floor. Mean annual rainfall in the Valley was 1610 mm. Both annual rainfall and the number of rainy days decreased in the Kathmandu Valley over the study period. The study indicated a significant reduction in rainfall after 2000. Since springs and shallow groundwater are the primary sources of water supply for residents in the Kathmandu Valley, it is apparent that decreasing rainfall will have (and is already having) an adverse impact on domestic, industrial, and agricultural water supplies, and the livelihoods of people.

scholarly journals Long-term trends of climate change and its impact on crop growing season on Montreal Island

2016 ◽  
Vol 8 (1) ◽  
pp. 78-88
Author(s):  
Erika Bouchard ◽  
Zhiming Qi
Keyword(s):  
Climate Change ◽  
Daily Rainfall ◽  
Growing Season ◽  
Annual Rainfall ◽  
Climate Trends ◽  
Growing Season Length ◽  
Mk Test ◽  
Long Term Trends ◽  
Increasing Trends

Long-term trends in air temperature and precipitation under climate change were analyzed for two meteorological stations on the Island of Montreal: McGill (1872–1986) and Pierre-Elliott-Trudeau (P-E-T, formerly Dorval) Airport (1942–2014). A linear trendline analysis, the Mann–Kendall (MK) test and the two-sample Kolmogorov–Smirnov (KS) test were conducted to assess specific climate trends. On a 100-year basis, temperature increased 1.88°C (34%) and 1.18°C (19%) at the McGill and P-E-T Airport sites, respectively, while annual rainfall increased 23.9 mm y−1 (2.3%) and 138.8 mm y−1 (15%) over the same period. The frequency of 50% (every other year) and 95% (every year) annual maximum daily rainfall events showed decreasing trends for the McGill station, but increasing trends for the P-E-T Airport station. Growing degree-days and growing season length are prone to being influenced by climate change and are critical to managing agricultural activities in the Montreal region; both showed increasing trends. At the same time, the onset of the growing season occurred earlier as time progressed.

Spatio-temporal Trend Detection of Rainfall for Climate Change Assessment in Ahmedabad-Gandhinagar District of Gujarat State, India

2021 ◽  
Vol 7 (1) ◽  
pp. 69-78
Author(s):  
Geeta S. Joshi ◽  
Payal Makhasana
Keyword(s):  
Climate Change ◽  
Rain Gauge ◽  
The State ◽  
Monthly Rainfall ◽  
Trend Detection ◽  
Annual Rainfall ◽  
Sen’S Slope Estimator ◽  
Sen’S Slope ◽  
Mk Test ◽  
Slope Estimator

The present research aims to assess the historical change in rainfall patterns with the changing climate in the Ahmedabad-Gandhinagar district in the state of Gujarat in India. The Mann-Kendall (MK) test along with Sen’s slope estimator have been used for detecting the trend of rainfall data series. The trend of annual rainfall is carried out for – (1) six rain gauge stations established by the State Water Data Center (SWDC) and (2) 11 grid data available from the National Center for Environmental Prediction-Climate Forecast System Reanalysis (NCEP-CFSR) for 35 years starting from 1979 to 2013. Results obtained from these two data sets for the trend detection were found consistent. Furthermore, the analyses of annual and monthly rainfall using MK test and Sen’s slope estimator at six rain gauge stations are carried out in three time periods i.e. 1974-1987, 1988-2001 and 2002-2016. The inverse distance weighted (IDW) method of interpolation is used for the results obtained from the spatial distribution of the temporal rainfall trend for interpolating the station value over the study area. Annual rainfall for data length of 1979 to 2013 shows an increasing trend. The trend of annual and monthly rainfall for July and September shows a positive trend for the span 2002-2016. This study would be useful to the water resource department and policymakers for climate change adaptation in the study area.

scholarly journals Rainfall and drought characteristics for crop planning in Palamau region of Jharkhand

MAUSAM ◽  
2021 ◽  
Vol 65 (1) ◽  
pp. 67-72
Author(s):  
PRAGYAN KUMARI ◽  
RAJAN KUMAROJHA ◽  
AWADOOD WADOOD ◽  
RAMESH KUMAR
Keyword(s):  
Temporal Variability ◽  
Daily Rainfall ◽  
Agricultural Drought ◽  
Annual Rainfall ◽  
Monsoon Period ◽  
Production Risk ◽  
Annual Basis ◽  
Average Annual Rainfall ◽  
Meteorological Droughts

Daily rainfall data of 56 years (1956-2011) of Palamau district of Jharkhand have been considered to analyse the long term average and its temporal variability on weekly, monthly, seasonal and annual basis. The average annual rainfall at Palamau was 1138 mm with 34 per cent coefficient of variation indicating thereby that the rainfall was not much stable over the years. July was the highest rainfall recipient month (332 mm) followed by August (310 mm) during the monsoon period. Trend analysis on rainfall of past 56 years exhibited a decreasing pattern of 8.33 mm and 7.04 mm per year in annual and kharif season rainfall, respectively. Agricultural drought was most frequently observed in early (23-26 SMW) as well as late (37-40 SMW) stages of kharif crops. Meteorological droughts of different intensities, viz., mild, moderate and severe over the observed periods showed that station is prone to mild-moderate type of drought. Short duration, low water requiring but high value crops like maize, pulses, oilseeds and some vegetables can be opted for this region to minimize the production risk.

scholarly journals Assessing the sources of uncertainty associated with the calculation of rainfall kinetic energy and erosivity – application to the Upper Llobregat Basin, NE Spain

2011 ◽  
Vol 15 (3) ◽  
pp. 679-688 ◽  
Author(s):  
G. Catari ◽  
J. Latron ◽  
F. Gallart
Keyword(s):  
Kinetic Energy ◽  
Temporal Variability ◽  
Rainfall Intensity ◽  
Spatial Scales ◽  
Annual Rainfall ◽  
Rainfall Erosivity ◽  
Sources Of Uncertainty ◽  
Eastern Pyrenees ◽  
Erosion Modelling

Abstract. The diverse sources of uncertainty associated with the calculation of rainfall kinetic energy and rainfall erosivity, calculated from precipitation data, were investigated at a range of temporal and spatial scales in a mountainous river basin (504 km2) in the south-eastern Pyrenees. The sources of uncertainty analysed included both methodological and local sources of uncertainty and were (i) tipping-bucket rainfall gauge instrumental errors, (ii) the efficiency of the customary equation used to derive rainfall kinetic energy from intensity, (iii) the efficiency of the regressions obtained between daily precipitation and rainfall erosivity, (iv) the temporal variability of annual rainfall erosivity values, and the spatial variability of (v) annual rainfall erosivity values and (vi) long-term erosivity values. The differentiation between systematic (accuracy) and random (precision) errors was taken into account in diverse steps of the analysis. The results showed that the uncertainty associated with the calculation of rainfall kinetic energy from rainfall intensity at the event and station scales was as high as 30%, because of insufficient information on rainfall drop size distribution. This methodological limitation must be taken into account for experimental or modelling purposes when rainfall kinetic energy is derived solely from rainfall intensity data. For longer temporal scales, the relevance of this source of uncertainty remained high if low variability in the types of rain was supposed. Temporal variability of precipitation at wider spatial scales was the main source of uncertainty when rainfall erosivity was calculated on an annual basis, whereas the uncertainty associated with long-term erosivity was rather low and less important than the uncertainty associated with other model factors such as those in the RUSLE, when operationally used for long-term soil erosion modelling.

scholarly journals Analysis of Climate Variability and Trends in Southern Ethiopia

Climate ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 96
Author(s):  
Abrham Belay ◽  
Teferi Demissie ◽  
John W. Recha ◽  
Christopher Oludhe ◽  
Philip M. Osano ◽  
...  
Keyword(s):  
Rainfall Variability ◽  
Rate Of Change ◽  
Mitigation Strategies ◽  
Annual Rainfall ◽  
Southern Ethiopia ◽  
Drought Indices ◽  
Trend Test ◽  
Rainfall Trends ◽  
Slope Estimator ◽  
Normal Rainfall

This study investigated the trends and variability of seasonal and annual rainfall and temperature data over southern Ethiopia using time series analysis for the period 1983–2016. Standard Anomaly Index (SAI), Coefficient of Variation (CV), Precipitations Concentration Index (PCI), and Standard Precipitation Index (SPI) were used to examine rainfall variability and develop drought indices over southern Ethiopia. Temporal changes of rainfall trends over the study period were detected using Mann Kendall (MK) trend test and Sen’s slope estimator. The results showed that the region experienced considerable rainfall variability and change that resulted in extended periods of drought and flood events within the study period. Results from SAI and SPI indicated an inter-annual rainfall variability with the proportions of years with below and above normal rainfall being estimated at 56% and 44% respectively. Results from the Mann Kendall trend test indicated an increasing trend of annual rainfall, Kiremt (summer) and Bega (dry) seasons whereas the Belg (spring) season rainfall showed a significant decreasing trend (p < 0.05). The annual rate of change for mean, maximum and minimum temperatures was found to be 0.042 °C, 0.027 °C, and 0.056 °C respectively. The findings from this study can be used by decision-makers in taking appropriate measures and interventions to avert the risks posed by changes in rainfall and temperature variability including extremes in order to enhance community adaptation and mitigation strategies in southern Ethiopia.

scholarly journals Trend Analysis of Rainfall Data in Magelang District Using Mann-Kendall Test and Modification Mann-Kendall Variation

AGRIFOR ◽  
2018 ◽  
Vol 17 (2) ◽  
pp. 293 ◽  
Author(s):  
Joko Suryanto ◽  
Joko Krisbiyantoro
Keyword(s):  
Kendall Test ◽  
Significant Trend ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Partial Sums ◽  
Trend Test ◽  
Positive Trend ◽  
Mk Test ◽  
Rainfall Trends ◽  
Negative Significant Trend

The objective of the research was to analyzed rainfall trends from 6 rainfall stations Kajoran, Mendut, Muntilan, Ngablak, Salaman and Tempuran rainfall station in different time scales (monthly, 3-months periodicityand annual). Identification homogenity of the rainfall data period 1986-2016 for Magelang district using Rescaled Adjusted Partial Sums (RAPS) methode. The three non-parametric tests, Mann-Kendall (MK), modified Mann-Kendall (MMK), trend free prewhitening Mann-Kendall (TFPW-MK) and Sen’s slope wereemployed to assess significance of trends and detecting magnitude of trends.The results shows that monthly rainfall have no significant trend using MK, MMK, and TFPW-MK test at 0.05 level significance. Rainfall 3-month based January-February-March (JFM) period Kajoran station have negative significant trend with magnitude 19.4 mm/3-month. Mendut station have positive trend for April-May-June (AMJ) period with magnitude 6.75 mm/3-month. No significant trends at 0.05 level significance using MK trend test were detected in annual rainfall for 6 rainfall stations.

Sign in / Sign up

Export Citation Format

Share Document