scholarly journals Recent Trends in the Daily Rainfall Regime in Southern West Africa

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 741 ◽  
Author(s):  
Francis Nkrumah ◽  
Théo Vischel ◽  
Geremy Panthou ◽  
Nana Ama Browne Klutse ◽  
David C. Adukpo ◽  
...  
Keyword(s):  
West Africa ◽  
Rainy Season ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Large Set ◽  
Mean Intensity ◽  
Mean Annual Rainfall ◽  
Recent Trends ◽  
The Mean ◽  
Climate Events

Extreme climate events, either being linked to dry spells or extreme precipitation, are of major concern in Africa, a region in which the economy and population are highly vulnerable to climate hazards. However, recent trends in climate events are not often documented in this poorly surveyed continent. This study makes use of a large set of daily rain gauge data covering Southern West Africa (extending from 10° W to 10° E and from 4° N to 12° N) from 1950 to 2014. The evolution of the number and the intensity of daily rainfall events, especially the most extremes, were analyzed at the annual and seasonal scales. During the first rainy season (April–July), mean annual rainfall is observed to have a minor trend due to less frequent but more intense rainfall mainly along the coast of Southern West Africa (SWA) over the last two decades. The north–south seasonal changes exhibit an increase in mean annual rainfall over the last decade during the second rainy season (September–November) linked by both an increase in the frequency of occurrence of rainy days as well as an increase in the mean intensity and extreme events over the last decade. The study also provides evidence of a disparity that exists between the west and east of SWA, with the east recording a stronger increase in the mean intensity of wet days and extreme rainfall during the second rainy season (September–November).

scholarly journals Precipitation characteristics over Paradeep

MAUSAM ◽  
2021 ◽  
Vol 49 (3) ◽  
pp. 321-324
Author(s):  
T. R. SIVARAMAKRISHNAN ◽  
J. R. PRASAD
Keyword(s):  
Monsoon Season ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Monsoon Period ◽  
Mean Annual Rainfall ◽  
Precipitation Characteristics ◽  
The Mean ◽  
Rainfall Climatology

The daily rainfall records since 1976 and the SRRG records after its installation in 1982 at Paradeep have been analysed and rainfall climatology has been worked out. The heaviest 24-hour rainfall recorded at the station is 264 mm on 4 June 1982. The mean annual rainfall is 1475 mm. January and December are near dry months while August is the wettest month getting about 339 mm rainfall. The variability of annual rainfall here is 20 %. Light rainspells giving a total rain of 10 mm or less form about 50% occasions in pre-monsoon period and 63% of occasions in monsoon period. The extended rainspells lasting for more than 4 hours form about 10% of occasions in pre-monsoon season and 6% occasions in monsoon season. While morning (04-08 hr IST) period gets the rainfall in both pre-monsoon and monsoon months, early night gets the peak rainfall activity during the pre-monsoon months.

A Practical Method for Estimating Rainfall Rate Frequencies Directly from Climatic Data

1958 ◽  
Vol 39 (9) ◽  
pp. 469-472 ◽  
Author(s):  
S. L. Russak ◽  
J. W. Easley
Keyword(s):  
Signal Transmission ◽  
General Relation ◽  
Practical Method ◽  
Rainfall Rate ◽  
Annual Rainfall ◽  
Climatic Data ◽  
Mean Annual Rainfall ◽  
Hourly Rainfall ◽  
The Mean ◽  
Complete Frequency

In evaluating the environmental limitations on microwave signal transmission, it was necessary to determine the occurrence of rainfall rates for a number of regions in different parts of the world. Clock-hourly precipitation data were used where available. Where these data were not available, a known empirical technique was employed which correlates clock-hourly rainfall at individual rates to a climatological index. This index uses parameters which are almost universally obtainable—namely, mean annual rainfall and number of days with measurable rain. In the course of this work, the authors found a more general relation between clock-hourly rainfall rate frequencies and the climatological index. Using this relation, rainfall frequencies at any rate are obtained directly from a linear equation and two nomograms. It is also possible to synthesize the complete frequency distribution of rainfall rates and obtain, as a check, the mean annual rainfall. Examples, supplemented by illustrations, are given in the development of this technique and its utilization.

THE MEAN ANNUAL RAINFALL OF MOUNT KENYA

Weather ◽  
1966 ◽  
Vol 21 (2) ◽  
pp. 48-49 ◽  
Author(s):  
B. W. Thompson
Keyword(s):  
Annual Rainfall ◽  
Mean Annual Rainfall ◽  
The Mean

Recent Changes in the Rain Regime in Israel 1975-2020

2021 ◽  
Author(s):  
Baruch Ziv ◽  
Ron Drori ◽  
Hadas Saaroni ◽  
Adi Etkin ◽  
Efrat Sheffer
Keyword(s):  
Rainy Season ◽  
Regional Climate ◽  
Daily Rainfall ◽  
The Other ◽  
Effective Length ◽  
Annual Rainfall ◽  
Rain Intensity ◽  
Subtropical Highs ◽  
The One ◽  
Mediterranean Oscillation

<p>Previous observation analyses have shown a declining rainfall trend over Israel, mostly statistically insignificant. These findings support the projections of the climatic models for the 21<sup>th</sup> century. The current study, for the period 1975-2020, undermines these findings, and the alarming future projections, and elaborates changes in the distribution of the rain along the rainy season.</p><p>The annual rainfall has a negligible trend, of +0.002%/decade, the number of rainy days has declined by -1.9%/decade and the average daily rainfall has increased by +2.1%/decade, all statistically insignificant. In the mid-winter both rainfall and daily rain intensity increased, while these variables have declined in the autumn and spring. The implied contraction of the rainy season is estimated by 2 measures. The 'effective length', which is determined by the time between accumulation of 10% and 90% of the annual rainfall, lasting 112 days on the average. This has been shortened by seven days during the study period. The other is the Seasonality Index (SI), reflecting the temporal concentration of the rainy season around its center. The trend found indicates that the regional climate is shifting from being between 'Markedly seasonal with a long dry season' and 'Most rain in ≤3 months', further toward the latter.</p><p>The trend in Cyprus Low occurrence and in the Mediterranean Oscillation Index were found to explain the rainfall trends only partially. We suggest that the cause for the increase in the mid-winter rain intensity is the increase in sea-surface temperature, found over the east Mediterranean, and for the decline in the transition seasons, to the poleward expansion of the subtropical highs. The contraction of the rainy season on the one hand, and the increased daily rain intensity in the mid-winter on the other, have ecological and hydrological impacts in this vulnerable region. </p>

scholarly journals Integration of Weather System Variability to Multidecadal Regional Climate Change: The West African Sudan–Sahel Zone, 1951–98

2006 ◽  
Vol 19 (20) ◽  
pp. 5343-5365 ◽  
Author(s):  
Michael A. Bell ◽  
Peter J. Lamb
Keyword(s):  
Rainy Season ◽  
Regional Climate ◽  
West African ◽  
Seasonal Rainfall ◽  
Annual Rainfall ◽  
Large Set ◽  
The West ◽  
Weather System ◽  
Linear Type ◽  
System Variability

Abstract Since the late 1960s, the West African Sudan–Sahel zone (10°–18°N) has experienced persistent and often severe drought, which is among the most undisputed and largest regional climate changes in the last half-century. Previous documentation of the drought generally has used monthly, seasonal, and annual rainfall totals and departures, in a standard “climate” approach that overlooks the underlying weather system variability. Most Sudan–Sahel rainfall occurs during June–September and is delivered by westward-propagating, linear-type, mesoscale convective systems [disturbance lines (DLs)] that typically have much longer north–south (102–103 km) than east–west (10–102 km) dimensions. Here, a large set of daily rainfall data is analyzed to relate DL and regional climate variability on intraseasonal-to-multidecadal time scales for 1951–98. Rain gauge–based indices of DL frequency, size, and intensity are evaluated on a daily basis for four 440-km square “catchments” that extend across most of the West African Sudan–Sahel (18°W–4°E) and are then distilled into 1951–98 time series of 10-day and seasonal frequency/magnitude summary statistics. This approach is validated using Tropical Applications of Meteorology Using Satellite Data (TAMSAT) satellite IR cold cloud duration statistics for the same 1995–98 DLs. Results obtained for all four catchments are remarkably similar on each time scale. Long-term (1951–98) average DL size/organization increases monotonically from early June to late August and then decreases strongly during September. In contrast, average DL intensity maximizes 10–30 days earlier than DL size/organization and is distributed more symmetrically within the rainy season for all catchments except the westernmost, where DL intensity tracks DL size/organization very closely. Intraseasonal and interannual DL variability is documented using sets of very deficient (8) and much more abundant (7) rainy seasons during 1951–98. The predominant mode of rainfall extremes involves near-season-long suppression or enhancement of the seasonal cycles of DL size/organization and intensity, especially during the late July–late August rainy season peak. Other extreme seasons result solely from peak season anomalies. On the multidecadal scale, the dramatic decline in seasonal rainfall totals from the early 1950s to the mid-1980s is shown to result from pronounced downtrends in DL size/organization and intensity. Surprisingly, this DL shrinking–fragmentation–weakening is not accompanied by increases in catchment rainless days (i.e., total DL absence). Like the seasonal rainfall totals, DL size/organization and intensity increase slightly after the mid-1980s.

scholarly journals Validation of Satellite Rainfall Products for Western Uganda

2014 ◽  
Vol 15 (5) ◽  
pp. 2030-2038 ◽  
Author(s):  
Jeremy E. Diem ◽  
Joel Hartter ◽  
Sadie J. Ryan ◽  
Michael W. Palace
Keyword(s):  
Daily Rainfall ◽  
Summer Rainfall ◽  
Seasonal Rainfall ◽  
Annual Rainfall ◽  
Boreal Summer ◽  
Time Step ◽  
African Rainfall ◽  
Rainfall Total ◽  
Mean Annual Rainfall ◽  
Western Uganda

Abstract Central equatorial Africa is deficient in long-term, ground-based measurements of rainfall; therefore, the aim of this study is to assess the accuracy of three high-resolution, satellite-based rainfall products in western Uganda for the 2001–10 period. The three products are African Rainfall Climatology, version 2 (ARC2); African Rainfall Estimation Algorithm, version 2 (RFE2); and 3B42 from the Tropical Rainfall Measuring Mission, version 7 (i.e., 3B42v7). Daily rainfall totals from six gauges were used to assess the accuracy of satellite-based rainfall estimates of rainfall days, daily rainfall totals, 10-day rainfall totals, monthly rainfall totals, and seasonal rainfall totals. The northern stations had a mean annual rainfall total of 1390 mm, while the southern stations had a mean annual rainfall total of 900 mm. 3B42v7 was the only product that did not underestimate boreal-summer rainfall at the northern stations, which had ~3 times as much rainfall during boreal summer than did the southern stations. The three products tended to overestimate rainfall days at all stations and were borderline satisfactory at identifying rainfall days at the northern stations; the products did not perform satisfactorily at the southern stations. At the northern stations, 3B42v7 performed satisfactorily at estimating monthly and seasonal rainfall totals, ARC2 was only satisfactory at estimating seasonal rainfall totals, and RFE2 did not perform satisfactorily at any time step. The satellite products performed worst at the two stations located in rain shadows, and 3B42v7 had substantial overestimates at those stations.

scholarly journals Statistical Analysis of Rainfall Variability for Tehsils of Palghar District, Maharashtra State, India

2021 ◽  
Vol 9 (VII) ◽  
pp. 2602-2618
Author(s):  
Dr. Sumit M. Dhak
Keyword(s):  
Statistical Analysis ◽  
Monsoon Season ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Department Of Agriculture ◽  
Average Annual Rainfall ◽  
Detailed Statistical Analysis ◽  
Annual Total ◽  
The Mean

A detailed statistical analysis of monthly, seasonal and annual rainfall for Tehsils of Palghar district were carried out using 22 years (1998-2019) daily rainfall data taken from Department of Agriculture, Maharashtra State. The mean, standard deviation and coefficient of variation for monthly, seasonal and annual rainfall were computed for tehsils of Palghar districts. The month of July received maximum monthly mean rainfall for all years (1998 to 2019) in tehsils of Palghar district. The result showed that monthly mean rainfall in month of July was maximum at Jawhar (1147.1 mm) followed by Vikramgad (1071.9 mm), Talasari (1014.3 mm), Vasai (1009.9 mm), Wada (998.5 mm), Mokhada (949.6 mm), Palghar (948.7 mm) and Dahanu (841.6) with contributes 40.4 %, 39.1 %, 38.5 %, 35.4 %, 37.3 %, 37.3 %, 36.9 % and 36.3 % of the annual mean rainfall (1998 to 2019) respectively. The result showed that contribution of rainfall during Monsoon season ranges from 95.5 % to 97.0 % of the annual total rainfall for tehsils of Palghar District. The result showed that average annual rainfall (1998 to 2019) of Vasai, Jawhar, Vikramgad, Wada, Talasari, Palghar, Mokhada and Dahanu were 2855.9 mm, 2839.1 mm, 2738.9 mm, 2674.0 mm, 2633.3 mm, 2570.8 mm, 2543.6 mm and 2318.5 mm respectively.

scholarly journals Regional frequency analysis of short duration rainfall extremes using gridded daily rainfall data as co-variate

2017 ◽  
Vol 75 (8) ◽  
pp. 1971-1981 ◽  
Author(s):  
H. Madsen ◽  
I. B. Gregersen ◽  
D. Rosbjerg ◽  
K. Arnbjerg-Nielsen
Keyword(s):  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Rainfall Data ◽  
Regional Frequency Analysis ◽  
Mean Annual Precipitation ◽  
Least Squares Regression ◽  
Mean Intensity ◽  
The Mean ◽  
Intensity Duration Frequency ◽  
Rainfall Statistics

A regional partial duration series (PDS) model is applied for estimation of intensity duration frequency relationships of extreme rainfalls in Denmark. The model uses generalised least squares regression to relate the PDS parameters to gridded rainfall statistics from a dense network of rain gauges with daily measurements. The Poisson rate is positively correlated to the mean annual precipitation for all durations considered (1 min to 48 hours). The mean intensity can be assumed constant over Denmark for durations up to 1 hour. For durations larger than 1 hour, the mean intensity is significantly correlated to the mean extreme daily precipitation. A Generalised Pareto distribution with a regional constant shape parameter is adopted. Compared to previous regional studies in Denmark, a general increase in extreme rainfall intensity for durations up to 1 hour is found, whereas for larger durations both increases and decreases are seen. A subsample analysis is conducted to evaluate the impacts of non-stationarities in the rainfall data. The regional model includes the non-stationarities as an additional source of uncertainty, together with sampling uncertainty and uncertainty caused by spatial variability.

scholarly journals Evaluation and Application of Multi-Source Satellite Rainfall Product CHIRPS to Assess Spatio-Temporal Rainfall Variability on Data-Sparse Western Margins of Ethiopian Highlands

2019 ◽  
Vol 11 (22) ◽  
pp. 2688 ◽  
Author(s):  
Ashebir Sewale Belay ◽  
Ayele Almaw Fenta ◽  
Alemu Yenehun ◽  
Fenta Nigate ◽  
Seifu A. Tilahun ◽  
...  
Keyword(s):  
Rainfall Variability ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Integration Time ◽  
Spatial And Temporal Variability ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Mean Annual Rainfall ◽  
Time Space ◽  
Spatio Temporal

The spatio-temporal characteristic of rainfall in the Beles Basin of Ethiopia is poorly understood, mainly due to lack of data. With recent advances in remote sensing, satellite derived rainfall products have become alternative sources of rainfall data for such poorly gauged areas. The objectives of this study were: (i) to evaluate a multi-source rainfall product (Climate Hazards Group Infrared Precipitation with Stations: CHIRPS) for the Beles Basin using gauge measurements and (ii) to assess the spatial and temporal variability of rainfall across the basin using validated CHIRPS data for the period 1981–2017. Categorical and continuous validation statistics were used to evaluate the performance, and time-space variability of rainfall was analyzed using GIS operations and statistical methods. Results showed a slight overestimation of rainfall occurrence by CHIRPS for the lowland region and underestimation for the highland region. CHIRPS underestimated the proportion of light daily rainfall events and overestimated the proportion of high intensity daily rainfall events. CHIRPS rainfall amount estimates were better in highland regions than in lowland regions, and became more accurate as the duration of the integration time increases from days to months. The annual spatio-temporal analysis result using CHIRPS revealed: a mean annual rainfall of the basin is 1490 mm (1050–2090 mm), a 50 mm increase of mean annual rainfall per 100 m elevation rise, periodical and persistent drought occurrence every 8 to 10 years, a significant increasing trend of rainfall (~5 mm year−1), high rainfall variability observed at the lowland and drier parts of the basin and high coefficient of variation of monthly rainfall in March and April (revealing occurrence of bimodal rainfall characteristics). This study shows that the performance of CHIRPS product can vary spatially within a small basin level, and CHIRPS can help for better decision making in poorly gauged areas by giving an option to understand the space-time variability of rainfall characteristics.

Sign in / Sign up

Export Citation Format

Share Document