scholarly journals Temporal rainfall trend analysis in different agro-ecological regions of southern Africa

Water SA ◽  
2021 ◽  
Vol 47 (4 October) ◽  
Author(s):  
W Mupangwa ◽  
R Makanza ◽  
L Chipindu ◽  
M Moeletsi ◽  
S Mkuhlani ◽  
...  
Keyword(s):  
Southern Africa ◽  
Linear Trend ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Farming Systems ◽  
Seasonal Rainfall ◽  
Smallholder Farming ◽  
Significant Linear Trend ◽  
Semi Arid ◽  
Linear Trends

Rainfall is a major driver of food production in rainfed smallholder farming systems. This study was conducted to assess linear trends in (i) different daily rainfall amounts (<5, 5–10, 11–20, 21–40 and >40 mm∙day-1), and (ii) monthly and seasonal rainfall amounts. Drought was determined using the rainfall variability index. Daily rainfall data were derived from 18 meteorological stations in southern Africa. Daily rainfall was dominated by <5 mm∙day-1 followed by 5–10 mm∙day-1. Three locations experienced increasing linear trends of <5 mm∙day-1 amounts and two others in sub-humid region had increases in the >40 mm day-1 category. Semi-arid location experienced increasing trends in <5 and 5–10 mm∙day-1 events. A significant linear trend in seasonal rainfall occurred at two locations with decreasing rainfall (1.24 and 3 mm∙season-1). A 3 mm∙season-1 decrease in seasonal rainfall was experienced under semi-arid conditions. There were no apparent linear trends in monthly and seasonal rainfall at 15 of the 18 locations studied. Drought frequencies varied with location and were 50% or higher during the November–March growing season. Rainfall trends were location and agro-ecology specific, but most of the locations studied did not experience significant changes between the 1900s and 2000s.

scholarly journals Defining Intraseasonal Rainfall Variability within the North American Monsoon

2006 ◽  
Vol 19 (17) ◽  
pp. 4243-4253 ◽  
Author(s):  
Phil J. Englehart ◽  
Arthur V. Douglas
Keyword(s):  
North American ◽  
Linear Trend ◽  
Monsoon Season ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Principal Component ◽  
Seasonal Rainfall ◽  
North American Monsoon ◽  
The North ◽  
The Pacific

Abstract This study provides an empirical description of intraseasonal rainfall variability within the North American monsoon (NAM) region. Applying particular definitions to historical daily rainfall observations, it demonstrates that distinct intraseasonal rainfall modes exist and that these modes differ considerably from the monsoon core region in northwest Sonora (SON), California, to its northward extension in southeast Arizona (AZ). To characterize intraseasonal rainfall variability (ISV), separate P-mode principal component (PC) analyses were performed for SON and AZ. The results indicate that in each area, much of the ISV in rainfall can be described by three orthogonal modes. The correlations between ISV modes and total seasonal rainfall reinforce the notion of differing behaviors between the monsoon’s core and extension. For SON all three ISV modes exhibit significant correlation with seasonal rainfall, with the strongest relationship in evidence for the ISV mode, which is related to rainfall intensity. For AZ, total rainfall exhibits the strongest correlation with the ISV mode, which emphasizes season length and rainfall consistency. Examination of longer-period behavior in the ISV modes indicates that, for SON, there is a positive linear trend in intensity, but a countervailing trend toward a shorter monsoon season along with less consistent rainfall in the form of shorter wet spells. For AZ, the evidence for trend in the ISV modes is not nearly as compelling, though one of the modes appears to exhibit distinct multidecadal variability. This study also evaluates teleconnectivity between ENSO, the Pacific decadal oscillation (PDO), and the NAM’s intraseasonal rainfall variability. Results indicate that part of the intraseasonal rainfall variability in both SON and AZ is connected to ENSO while only SON exhibits a teleconnection with the long-period fluctuations of the PDO.

The Southern Oscillation Index as a predictor of seasonal rainfall in the arable areas of the inland Australian subtropics

1993 ◽  
Vol 44 (6) ◽  
pp. 1337 ◽  
Author(s):  
JS Russell ◽  
IM McLeod ◽  
MB Dale ◽  
TR Valentine
Keyword(s):  
Southern Oscillation Index ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Summer Rainfall ◽  
Seasonal Rainfall ◽  
Four Seasons ◽  
Eastern Australia ◽  
Australian Continent ◽  
Ace Algorithm ◽  
Linear Trends

A detailed study has been carried out in four regions in the subtropics of Eastern Australia to determine the relationship between the Southern Oscillation Index (SOI) and subsequent seasonal rainfall. The period studied was from 1915 to 1991 for 3-monthly periods of spring (SON), summer (DJF), autumn (MAM) and winter (JJA). The 3-monthly prior SOI values were plotted against seasonal rainfall of the four regions and four seasons. These data were widely scattered but with a linear trend showing increased seasonal rainfall as the SOI increased. Linear trends were plotted for each season and region. Comparisons were made between the use of the ACE algorithm, which transforms the SOI and rainfall data, and the use of linear trends. Polynomials were used to calculate equations for each region and season, but only spring and summer produced satisfactory ACE functions. Estimates were made of spring and summer rainfall relative to prior SOI values for each region. While the SOI as a predictor of rainfall broadly estimates spring and summer rainfall, this variable has limited usefulness on its own. One of the options available with the ACE program is that additional independent variables can be added as required. Current research suggests that sea surface temperature data from specific ocean areas surrounding the Australian continent is the most useful additional variable at present. However the complexity of such an analysis is greatly increased.

scholarly journals Linking Drought Intensity with Rice Yield in Nagaland

2021 ◽  
Author(s):  
Baiarbor Nongbri ◽  
S.M. Feroze ◽  
Ram Singh ◽  
L.I.P. Ray
Keyword(s):  
Normal Condition ◽  
Drought Index ◽  
Rice Yield ◽  
Linear Trend ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Severe Drought ◽  
Drought Intensity ◽  
Rice Yields ◽  
Linear Trends

Background: Rainfall being one of the most important factors of production for rainfed kharif rice, occurrence of drought may have serious implication on rice yield. Hence, this study is an attempt to understand the linkage between drought and yield of rice in Phek and Dimapur district of Nagaland where rice is the primary crop. Methods: Reconnaissance Drought Index was calculated using gridded daily rainfall (0.25o X 0.25o) and temperature (1o X 1o) (o=degree) data for the year of 1975-2013.Result: The annual mean temperature has increased by 0.03oC in Phek and Dimapur district during the study period. The increasing linear trends for annual temperatures are significant whereas, the linear trend for annual rainfall shows decreasing but insignificant trend. About 38.46% and 41.02% of the 39 years under study were ‘Normal condition-dry’ in Phek in Dimapur district, respectively. Moderate and severe drought occurred more frequently in Dimapur than Phek. After 1994, majority of the years were drought years and the frequency of occurrence was higher in Dimapur. The drought occurrences negatively impacted the rice yields and the rice yield may reduce by 13.85% in normal condition dry to 18.45% in extreme drought condition.

scholarly journals Understanding Adoption and Impacts of Conservation Agriculture in Eastern and Southern Africa: A Review

2021 ◽  
Vol 3 ◽  
Author(s):  
Hambulo Ngoma ◽  
Arild Angelsen ◽  
Thomas S. Jayne ◽  
Antony Chapoto
Keyword(s):  
Southern Africa ◽  
Agricultural Research ◽  
Farming Systems ◽  
Conservation Agriculture ◽  
Evidence Base ◽  
Smallholder Farming ◽  
Ecological Zones ◽  
Environmental Objectives ◽  
Eastern And Southern Africa ◽  
Capital Intensive

Conservation Agriculture (CA) aims to concurrently promote agricultural productivity, local livelihoods, climate resilience and other environmental objectives. We review the emerging evidence base in Eastern and Southern Africa to address whether CA is climate smart and why adoption rates by smallholders remain generally very low. We first develop an adoption framework that can be used to assess when and where the different components of CA are expected to be adopted under different conditioning factors and consider options to make CA climate smart. Our results suggest that CA can contribute positively to productivity and adaptation/resilience objectives, although the degree of success varies considerably by farm, household and regional characteristics. Overall, we find that capital-intensive (mechanized) CA is more likely to be adopted in areas of economic dynamism where capital is cheap relative to labor. Labor-intensive CA practices are more likely to be adopted in regions of economic stagnation where capital is expensive, and labor is abundant and cheap. A subnational focus is needed to identify economic conditions of different regions and agro-ecological zones and to test hypotheses derived from the framework in this paper and to propose the most appropriate CA packages for promotion. Our findings suggest that labor using variants of CA such as planting basins are more likely to be adopted than are capital using mechanized options in densely populated parts of Malawi, Ethiopia, Kenya, Tanzania, Zambia and Zimbabwe where labor is abundant, and presumably cheap, but capital is expensive. However, rising land scarcity (prices) and wages in the region present an opportunity for capital intensive, mechanized CA operations to be adopted if the cost of capital can be kept low and if there is a supportive environment for mechanization. We conclude that CA is climate smart and if adopted widely, it has the potential to help build resilience in smallholder farming systems. CA can be more climate smart, and its uptake can be enhanced by reframing, better targeting, adapting CA to location-specific economic and biophysical, and through greater and more effective public spending on agricultural research and development.

scholarly journals Influence of South Atlantic Sea Surface Temperatures on Rainfall Variability and Extremes over Southern Africa

2008 ◽  
Vol 21 (24) ◽  
pp. 6498-6520 ◽  
Author(s):  
C. J. R. Williams ◽  
D. R. Kniveton ◽  
R. Layberry
Keyword(s):  
High Resolution ◽  
Southern Africa ◽  
Climate Model ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
South Atlantic ◽  
Sea Surface ◽  
Rainfall Extremes ◽  
Central South

Abstract It is generally agreed that changing climate variability, and the associated change in climate extremes, may have a greater impact on environmentally vulnerable regions than a changing mean. This research investigates rainfall variability, rainfall extremes, and their associations with atmospheric and oceanic circulations over southern Africa, a region that is considered particularly vulnerable to extreme events because of numerous environmental, social, and economic pressures. Because rainfall variability is a function of scale, high-resolution data are needed to identify extreme events. Thus, this research uses remotely sensed rainfall data and climate model experiments at high spatial and temporal resolution, with the overall aim being to investigate the ways in which sea surface temperature (SST) anomalies influence rainfall extremes over southern Africa. Extreme rainfall identification is achieved by the high-resolution microwave/infrared rainfall algorithm dataset. This comprises satellite-derived daily rainfall from 1993 to 2002 and covers southern Africa at a spatial resolution of 0.1° latitude–longitude. Extremes are extracted and used with reanalysis data to study possible circulation anomalies associated with extreme rainfall. Anomalously cold SSTs in the central South Atlantic and warm SSTs off the coast of southwestern Africa seem to be statistically related to rainfall extremes. Further, through a number of idealized climate model experiments, it would appear that both decreasing SSTs in the central South Atlantic and increasing SSTs off the coast of southwestern Africa lead to a demonstrable increase in daily rainfall and rainfall extremes over southern Africa, via local effects such as increased convection and remote effects such as an adjustment of the Walker-type circulation.

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