scholarly journals Recent Rainfall Trend and Abrupt Changes Over Cavally Basin (West Africa)

2021 ◽  
pp. 52-66
Author(s):  
Blé Anouma Fhorest Yao ◽  
Emile Gneneyougo Soro
Keyword(s):  
Rainy Season ◽  
Kendall Test ◽  
Study Data ◽  
Dry Season ◽  
Annual Rainfall ◽  
Homogeneity Test ◽  
Monthly Precipitation ◽  
Climate Trends ◽  
Significant Drop ◽  
Standard Normal Homogeneity Test

Aims: Analyze the recent variations in annual and monthly precipitation at 18 pluviometry stations in the Cavally river basin. Place and Duration of Study: Data of month and annual rainfall data of 37 years (1980-2016) collected from the National direction of Meteorology for Ivory Coast and Guinea and from https://app.climateengine.org/climateEngine for Liberia. Methodology: Statistical methods are used to highlight the evolution of cumulative annual rainfall and the distribution of the different seasons over the period 1980-2016. Hanning’s low pass, Mann-Kendall classic test, modified Mann-Kendall test, Mann-Kendall seasonal test and Standard Normal Homogeneity Test were applied to identify the existing trend direction and significance of change over time. Results: The periods 1980-1996 and 1997-2016 could be considered as wet and dry periods respectively (with a rainfall deficit of 18% after the break in 1996). In addition, we observe a decrease in rainy days of strong accumulation that lead to a significant drop in total annual rainfall. Finally, an abnormal increase in rainfall during the dry season months and a decrease in rainfall during the rainy season months. This indicates an intra-seasonal irregularity (shortening of the rainy season and prolongation of the dry season) of precipitation. Conclusion: The Hanning filter, M-K test and SNHT are non-parametric tests widely used in the study of climate trends. However, the additional consideration of serial autocorrelation (MM-K test) and seasonal trends (M-K-S test) allows to extend and refine the information on climate variability.

Spatiotemporal variability of annual and seasonal rainfall time series in Ho Chi Minh city, Vietnam

2018 ◽  
Vol 10 (3) ◽  
pp. 658-670 ◽  
Author(s):  
Dang Nguyen Dong Phuong ◽  
Vu Thuy Linh ◽  
Tran Thong Nhat ◽  
Ho Minh Dung ◽  
Nguyen Kim Loi
Keyword(s):  
Time Series ◽  
Rainy Season ◽  
Kendall Test ◽  
Dry Season ◽  
Seasonal Rainfall ◽  
Spatiotemporal Variability ◽  
Ho Chi Minh City ◽  
Annual Rainfall ◽  
Rainfall Time Series ◽  
Spatial And Temporal Patterns

Abstract This study analyzed spatial and temporal patterns of rainfall time series from 14 proportionally distributed stations in Ho Chi Minh City for the period 1980–2016. Both parametric and nonparametric approaches, specifically, linear regression, the Mann–Kendall test and Sen's slope estimator, were applied to detect and estimate the annual and seasonal trends after using original and notched boxplots for the preliminary interpretation. The outcomes showed high domination of positive trends in the annual and seasonal rainfall time series over the 37-year period, but most statistically significant trends were observed in the dry season. The results of trend estimation also indicated higher increasing rates of rainfall in the dry season compared to the rainy season at most stations. Even though the total amount of annual rainfall is mainly contributed by rainfall during the rainy season, the pronounced increment in the dry season can be a determining factor of possible changes in annual rainfall. Additionally, the interpolated results revealed a consistently increasing trend in the southeastern parts of the study area (i.e., Can Gio district), where annual rainfall was by far the lowest intensity compared to other regions.

scholarly journals PENENTUAN MUSIM TANAM, JENIS VARIETAS, DAN TEKNIK BUDIDAYA TANAMAN PADI TERKAIT MITIGASI EMISI METANA (CH4) (Determination of Early Planting Season, Type Varieties, and Cultivation Techniques of Rice as Mitigation to Methane Emission)

2018 ◽  
Vol 24 (1) ◽  
pp. 1
Author(s):  
Lilik Slamet Supriatin
Keyword(s):  
Rainy Season ◽  
Growing Season ◽  
Dry Season ◽  
Wetland Mitigation ◽  
Annual Rainfall ◽  
Ch4 Emission ◽  
Ch4 Emissions ◽  
Cultivation Techniques ◽  
Planting Season

ABSTRAKEmisi metana (CH4) dari pertanian padi lahan sawah dapat dipengaruhi oleh faktor-faktor seperti cara pemberian air, pengolahan tanah, varietas padi, dan iklim. Pada penelitian ini dikaji tahap penentuan musim tanam, pemilihan varietas padi, dan tahap terakhir adalah teknik budidaya pertanian padi lahan sawah yang terkait mitigasi emisi CH4. Hasil kajian menunjukkan bahwa musim tanam padi pada musim kemarau menghasilkan emisi CH4 lebih kecil daripada di musim hujan dengan pengurangan emisi CH4 sebesar 18,13%. Indonesia yang memiliki tiga tipe pola curah hujan tahunan (monsunal, equatorial, lokal) mengakibatkan periode musim tanam rendah emisi CH4 berbeda antara tipe curah hujan yang satu dengan lainnya. Varietas padi Way apo buru adalah varietas yang menghasilkan emisi CH4 terendah tetapi tetap optimum dalam produksi gabah sehingga dapat dipilih menjadi prioritas pertama untuk ditanam. Teknik budidaya pertanian padi lahan sawah yang menghasilkan rendah emisi CH4 dapat dilakukan dengan membuat genangan air yang dangkal saja, dengan cara pemberian air berselang, dan kombinasi antara pemeliharaan padi, ganggang, tanaman paku air, ikan air tawar, dan bakteri metanotrof dalam satu petak lahan sawah (mina padi plus). Pemberian air dengan cara berselang menurunkan emisi CH4 pada musim kemarau sebesar 59,36% dan pada musim hujan sebesar 51,68% jika dibandingkan dengan pemberian air secara terus-menerus (kontinyu). Teknik budidaya mina padi plus mengurangi emisi CH4 sebesar 21,5 kg/ha/musim tanam dan bakteri metanotrof mengurangi emisi CH4 ke atmosfer sebesar 20-60 Tg. Sawah dapat dijadikan sebagai instalasi terbuka pengolahan udara berlimbah CH4. ABSTRACTMethane (CH4) emissions from rice cultivation can be influenced by several factors i.e. the provision of water, soil cultivation, varieties of rice, and the climate. This study will examine the determination of the growing season, the selection of rice varieties and cultivation techniques of rice agriculture-related wetland mitigation of the CH4 emission. The results showed that the rice planting season in the dry season produces CH4 emissions is smaller than in the rainy season with CH4 emission reduction of 18.13%. Indonesia, which has three types of annual rainfall patterns resulting in periods of low growing season CH4 emissions differ between types of rainfall each other. Way apo buru rice species are varieties that produce low emissions of CH4 but remains optimum in grain production. Cultivation techniques of rice farming rice fields that produce low emissions of CH4 can be done by creating a pool of shallow water only, by way of provision of water intermittent, and the combination of maintenance of rice, algae, plants salviniales, freshwater fish, and bacteria metanotrof in a wetland. The provision of water by intermittent lowering emissions of CH4 in the dry season by 59.36% and in the rainy season amounted to 51.68% when compared to the provision of water continuously (continuous). Mina padi plus cultivation techniques reduce CH4 emissions by 21.5 kg/ha/planting and metanotrof bacteria can reduce CH4 emissions to the atmosphere by 20-60 Tg. 

scholarly journals Investigating possible changes of extreme annual rainfall in Zimbabwe

2008 ◽  
Vol 5 (4) ◽  
pp. 1765-1785 ◽  
Author(s):  
D. Mazvimavi
Keyword(s):  
Global Warming ◽  
Regression Analysis ◽  
Water Resources ◽  
Quantile Regression ◽  
Rainy Season ◽  
Kendall Test ◽  
Annual Rainfall ◽  
Management Approach ◽  
Average Rainfall ◽  
Quantile Regression Analysis

Abstract. There is increasing concern about the perceived decline in rainfall which is sometimes attributed to global warming. Some studies have concluded that average rainfall in Zimbabwe has declined by 10% or 100 mm/yr during the last 100 yrs. This paper investigates the validity of the assumption that rainfall is declining in Zimbabwe. Time series of annual rainfall, and total rainfall for a) the early party of the rainy season, October-November-December (OND), and b) the mid to end of the rainy season, January-February-March (JFM) are analysed for the presence of trends using the Mann-Kendall test, and changes in extreme rainfall using quantile regression analysis. The analysis has been done for 40 rainfall stations with records starting during the 1892–1940 period and ending in 2000, and representative of the major rainfall regions. The Mann-Kendal test did not identify a significant trend at all the 40 stations, and therefore there is no proof that the average rainfall at each of these stations has changed. Quantile regression analysis revealed a decline in annual rainfall less than the tenth percentile at only one station, and increasing rainfall for rainfall greater than the ninetieth percentile at another station. All the other stations revealed no changes over time in both the extreme low and high rainfall at the annual interval. Therefore, there is no evidence that the frequency and severity of droughts has changed during the 1892 to 2000 period. The general perception about declining rainfall is likely shaped by a comparison of the recent drought years (1980's–1990's) to recent wet periods (1970's). There have however been periods with similar dry years beyond the recallable memory, e.g. 1926–1936, 1940's. Crop failures and livestock losses attributed to declining rainfall are most likely due to poor agricultural practices such as production of crops in unsuitable climatic regions, degradation of rangelands partly due to increasing livestock populations. Rainfall in Zimbabwe has high inter-annual variability, and currently any change due to global warming is not yet statistically detectable. The annual renewal rate of water resources from rainfall has therefore not changed, and an adaptive water resources management approach is called to overcome problems arising from increasing water demand, and variability of available water resources.

scholarly journals Variation in Onset of Leaf Unfolding and Wood Formation in a Central African Tropical Tree Species

2021 ◽  
Vol 4 ◽  
Author(s):  
Bhely Angoboy Ilondea ◽  
Hans Beeckman ◽  
Joris Van Acker ◽  
Jan Van den Bulcke ◽  
Adeline Fayolle ◽  
...  
Keyword(s):  
Tree Species ◽  
Rainy Season ◽  
Cambial Activity ◽  
Wood Formation ◽  
Dry Season ◽  
Tropical Tree ◽  
Congo Basin ◽  
Leaf Phenology ◽  
Annual Rainfall ◽  
Tropical Tree Species

A diversity of phenological strategies has been reported for tropical tree species. Defoliation and seasonal dormancy of cambial activity inform us on how trees cope with water stress during the dry season, or maximize the use of resources during the rainy season. Here, we study the matching between leaf phenology (unfolding and shedding) and cambial activity for Prioria balsamifera, a key timber species in the Democratic Republic of Congo. In particular, we (i) evaluated the seasonality of cambial activity and synchrony of phenology among trees in response to climate and (ii) identified the seasonality of leaf phenology and its relation with cambial phenology. The study was conducted in the Luki Man and Biosphere Reserve, located in the Mayombe forest at the southern margin of the Congo Basin. Historic defoliation data were collected every ten days using weekly crown observations whereas recent observations involved time-lapse cameras. Cambial pinning was performed on ten trees during 20 months and radius dendrometers were installed on three trees during 13 months. Tree rings were measured on cores from 13 trees and growth synchrony was evaluated. We found that P. balsamifera defoliates annually with a peak observed at the end of the dry season and the beginning of the rainy season. The new leaves unfolded shortly after shedding of the old leaves. The peak defoliation dates varied across years from September 12 to November 14 and the fraction of number of trees that defoliated at a given time was found to be negatively correlated with annual rainfall and temperature; during the dry season, when precipitation and temperatures are the lowest. Wood formation (radial growth), was found to be highly seasonal, with cambial dormancy occurring during the dry season and growth starting at the beginning of the rainy season. Individual ring-width series did not cross date well. The within species variability of leaf phenology and cambial rhythms provides indication about resistance of the population against climatic changes.

scholarly journals Assessing Inhomogeneities in Extreme Annual Rainfall Data Series by Multifractal Approach

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1030 ◽  
Author(s):  
Amanda García-Marín ◽  
Javier Estévez ◽  
Renato Morbidelli ◽  
Carla Saltalippi ◽  
José Ayuso-Muñoz ◽  
...  
Keyword(s):  
Central Italy ◽  
Extreme Rainfall ◽  
Break Point ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Data Series ◽  
Homogeneity Test ◽  
Umbria Region ◽  
Standard Normal Homogeneity Test ◽  
Break Points

Testing the homogeneity in extreme rainfall data series is an important step to be performed before applying the frequency analysis method to obtain quantile values. In this work, six homogeneity tests were applied in order to check the existence of break points in extreme annual 24-h rainfall data at eight stations located in the Umbria region (Central Italy). Two are parametric tests (the standard normal homogeneity test and Buishand test) whereas the other four are non-parametric (the Pettitt, Sequential Mann–Kendal, Mann–Whitney U, and Cumulative Sum tests). No break points were detected at four of the stations analyzed. Where inhomogeneities were found, the multifractal approach was applied in order to check if they were real or not by comparing the split and whole data series. The generalized fractal dimension functions Dq and the multifractal spectra f(α) were obtained, and their main parameters were used to decide whether or not a break point existed.

scholarly journals The Svalbard Airport Temperature Series

2010 ◽  
Vol 3 (1) ◽  
pp. 5-25 ◽  
Author(s):  
Øyvind Nordli
Keyword(s):  
Local Maximum ◽  
Thermal Conditions ◽  
Kendall Test ◽  
Temperature Series ◽  
Homogeneity Test ◽  
Svalbard Archipelago ◽  
Ww Ii ◽  
Standard Normal Homogeneity Test ◽  
Composite Series

Abstract In the Isfjorden region of Spitsbergen in the Svalbard archipelago, the air temperature has been observed continuously at different sites since 1911 (except for a break during WW II). The thermal conditions at these various sites turned out to be different so that nesting the many series together in one composite time series would produce an inhomogenous long-term series. By using the SNHT (Standard Normal Homogeneity Test) the differences between the sites were assessed and the series adjusted accordingly. This resulted in an homogenised, composite series mainly from Green Harbour (Finneset in Grønfjorden), Barentsburg (also in Grønfjorden), Longyearbyen and the current observation site at Svalbard Airport. A striking feature in the series is a pronounced, abrupt change from cold temperature in the 1910s to warmth in the 1930s, when temperature reached a local maximum. This event is called the early 20th century warming. Thereafter the temperature decreased to a local minimum in the 1960s before the start of another increase that still seems to be ongoing. For the whole series, statistically significant positive trends were detected by the Mann-Kendall test for annual and seasonal values (except for winter). Quite often the Norwegian Meteorological Institute receives queries about long-term temperature series from Svalbard. Hopefully, the Svalbard Airport composite series will fulfil this demand for data. It may be downloaded free of charge from the Institute’s home page: http://sharki.oslo.dnmi.no and should be used with reference to this article.

scholarly journals Time Series Analysis of Monthly and Annual Precipitation in The State of Texas Using High-Resolution Radar Products

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 982
Author(s):  
Dawit Ghebreyesus ◽  
Hatim O. Sharif
Keyword(s):  
Southern Oscillation ◽  
Stage Iv ◽  
The State ◽  
Trend Test ◽  
Homogeneity Test ◽  
Monthly Precipitation ◽  
Slope Test ◽  
Standard Normal Homogeneity Test ◽  
Significant Difference ◽  
Before And After

Precipitation is the main source for replenishing groundwater stored in aquifers for a myriad of beneficial purposes, especially in arid and semi-arid regions. A significant portion of the municipal and agricultural water demand is satisfied through groundwater withdrawals in Texas. These withdrawals have to be monitored and regulated to be in balance with the recharge amount from precipitation in order to ensure water security. The main goal of this study is to understand the spatio-temporal variability of precipitation in the 21st century using high spatial resolution stage-IV radar data over the state of Texas and examine some climatic controls behind this variability. The results will shed light on the trends of precipitation and hence will contribute to improving water resources management strategies and policies. Pettit’s test and Standard Normal Homogeneity Test (SNHT), tools for detecting change-point in the monthly precipitation, suggested change-points have occurred across the state around the years 2013 and 2014. The test for the homogeneity of the data before and after 2013 revealed that, in over 64% of the state, the precipitation means were significantly different. The Panhandle region (northern part) is the only part of the state that did not show a significant difference in the mean precipitation before and after 2013. Theil-Sen’s slope test, Correlated Seasonal Mann-Kendall Test, and Cox and Stuart Trend Test all indicated that there were no significant trends in the monthly precipitation after 2013 in over 98% of the area of the state. Texas precipitation was found to be influenced significantly by the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). A significant correlation in more than 82% and 60% of the state was found with ENSO at two-month and with PDO at four-month lag, respectively.

scholarly journals Long-term (35 Years) Rainy and Dry Season Characterization in Semiarid Northeastern Brazil

2021 ◽  
Author(s):  
J. Sparacino ◽  
D.S. Argibay ◽  
G. Espindola
Keyword(s):  
Rainy Season ◽  
Rain Rate ◽  
Fire Risk ◽  
Water Security ◽  
Dry Season ◽  
Northeastern Brazil ◽  
Annual Rainfall ◽  
Data Series ◽  
Season Length ◽  
Conservation Area

Abstract Uncertainties in the timing and quality of rainy season are a threat for food and water security, and also in terms of fire vulnerability. Then, understanding features associated to rainfall allows a climate characterization useful for climate and fire risk management. We used rainfall data series (1983-2018) from 15 meteorological stations to characterize the greatest conservation area of Brazilian-unique seasonally dry tropical forest Caatinga (northeastern Brazil). Accumulated anomalies in daily series were used to determine onset and end of rainy seasons. We also determined seasonal and annual rainfall (quality) and rain rate, and performed a dry season sub-classification. Results showed greater variability for end dates as compared to onset dates for rainy season. Droughts in the region are becoming more severe. We found a significant decreasing tendency of 7 mm/year on annual rainfall, of 0.3 mm/day per decade on rain rate, and an increase of 12 days per decade on consecutive dry days. Dry season length presented a 14-year periodicity and is related with previous but uncorrelated from posterior rainy season length. The complexity of the rainfall patterns is evidenced by the weak correlation we found between the amount of rainfall and the rainy season length.

scholarly journals Analysis of Precipitation and Temperature Extremes over the Muda River Basin, Malaysia

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 283 ◽  
Author(s):  
Mou Leong Tan ◽  
Narimah Samat ◽  
Ngai Weng Chan ◽  
Anisah Jessica Lee ◽  
Cheng Li
Keyword(s):  
River Basin ◽  
Climate Extremes ◽  
Quality Data ◽  
Maximum Temperature ◽  
Homogeneity Test ◽  
Temperature Extremes ◽  
Monthly Precipitation ◽  
Northeast Monsoon ◽  
Standard Normal Homogeneity Test ◽  
Precipitation And Temperature

Trends in precipitation and temperature extremes of the Muda River Basin (MRB) in north-western Peninsular Malaysia were analyzed from 1985 to 2015. Daily climate data from eight stations that passed high quality data control and four homogeneity tests (standard normal homogeneity test, Pettitt test, Buishand range test, and von Neumann ratio test) were used to calculate 22 Expert Team on Climate Change Detection and Indices (ETCCDI) extreme indices. Non-parametric Mann–Kendall, modified Mann–Kendall and Sens’ slope tests were applied to detect the trend and magnitude changes of the climate extremes. Overall, the results indicate that monthly precipitation tended to increase significantly in January (17.01 mm/decade) and December (23.23 mm/decade), but decrease significantly in May (26.21 mm/decade), at a 95% significance level. Monthly precipitation tended to increase in the northeast monsoon, but decrease in the southwest monsoon. Mann–Kendall test detected insignificant trends in most of the annual climate extremes, except the extremely wet days (R99p), mean of maximum temperature (TXmean), mean of minimum temperature (TNmean), cool days (TX10p), cool nights (TN10p), warm days (TX90p) and warm nights (TN90p) indices. The number of heavy (R10mm), very heavy (R20mm), and violent (R50mm) precipitation days changed at magnitudes of 0~2.73, −2.14~3.33, and −1.67~1.29 days/decade, respectively. Meanwhile, the maximum 1-day (Rx1d) and 5-day (Rx5d) precipitation amount indices changed from −10.18 to 3.88 mm/decade and −21.09 to 24.69 mm/decade, respectively. At the Ampangan Muda station, TNmean (0.32 °C/decade) increased at a higher rate compared to TXmean (0.22 °C/decade). The number of the cold days and nights tended to decrease, while an opposite trend was found in the warmer days and nights.

scholarly journals A Case Study of Rainfall and Temperature Trends in San Diego Region, 1985–2017

Hydrology ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 87
Author(s):  
Esther Mosase ◽  
Laurent Ahiablame ◽  
Fritz Light ◽  
Francis Dwomoh
Keyword(s):  
Rainy Season ◽  
San Diego ◽  
Management Strategies ◽  
Kendall Test ◽  
Dry Season ◽  
Maximum Temperature ◽  
Data Compilation ◽  
Maximum Temperatures ◽  
Set Up

Prolonged and frequent droughts in Southern California present hazards and uncertainty for the region’s increasing population, resulting in proactive and aggressive water management strategies. The goal of this study is to present a case study of the San Diego region’s rainfall and temperature time series analysis in order to determine annual and seasonal trends and their significance. Rainfall and temperature data from 20 rain-gauged stations were analyzed for the period 1985–2017. A project database was set up for data compilation and quality control, and a Mann-Kendall test for trend analysis was used. Results indicated that rainfall in the region decreased both annually and during the rainy season (November–April) by up to 0.14 mm between 1985 and 2017, although not in a statistically significant manner, except at two rainfall observation stations. Rainfall appears to have increased in many of the stations examined during the dry season (May–October), with an average magnitude of 0.09 mm. Analysis of daily minimum and maximum temperature reveals overall average annual and seasonal increases of 0.07 °C and 0.04 °C, respectively, with statistically significant increases at 10 of 17 for minimum temperature, and 0.27 °C and −0.25 °C with statistically significant increases at 9 of 16 for maximum temperature. Temperature tends to have increased more during the dry season compared to the rainy season. This study reveals an overall decreasing tendency in rainfall and an increasing tendency in minimum and maximum temperatures (although not statistically significant) in the San Diego region between 1985 and 2017, which likely contributed to important management implications for the region’s water resources.

Sign in / Sign up

Export Citation Format

Share Document