scholarly journals Intraseasonal Teleconnections between South America and South Africa

2015 ◽  
Vol 28 (23) ◽  
pp. 9489-9497 ◽  
Author(s):  
Alice M. Grimm ◽  
C. J. C. Reason
Keyword(s):  
South America ◽  
Southern Africa ◽  
Rainfall Variability ◽  
Intraseasonal Variability ◽  
Daily Rainfall ◽  
Summer Rainfall ◽  
South American ◽  
Climate Anomalies ◽  
Monsoon System ◽  
The Tropics

Abstract Teleconnection of climate anomalies between various parts of the tropics and extratropics is a well-established feature of the climate system. Building on previous work showing that a teleconnection exists between the South American monsoon system and interannual summer rainfall variability over southern Africa, this study considers intraseasonal variability over these landmasses. It is shown that strong teleconnections exist between South African daily rainfall and that over various areas of South America, with the latter leading by 4–5 days, for both winter and summer, involving regions with strong rainfall in these seasons. During the summer, the mechanisms involve both a modulation of the local Walker cell as well as extratropical Rossby wave trains. For winter, the latter mechanism is more important. While in summer tropical convective anomalies over South America play an important role, in winter the subtropics become more important. In both cases, these modulations lead to regional changes in circulation over southern Africa that are favorable for the dominant synoptic rainfall-producing weather systems such as cutoff lows and tropical extratropical cloud bands.

scholarly journals The Role of Mesoscale Convective Complexes in Southern Africa Summer Rainfall

2013 ◽  
Vol 26 (5) ◽  
pp. 1654-1668 ◽  
Author(s):  
R. C. Blamey ◽  
C. J. C. Reason
Keyword(s):  
South Africa ◽  
Southern Africa ◽  
Rainfall Variability ◽  
Warm Season ◽  
Tropical Rainfall Measuring Mission ◽  
Summer Rainfall ◽  
Spatial And Temporal Variability ◽  
Eastern Region ◽  
Southwest Indian Ocean ◽  
Mesoscale Convective

Abstract A combination of numerous factors, including geographic position, regional orography, and local sea surface temperatures, means that subtropical southern Africa experiences considerable spatial and temporal variability in rainfall and is prone to both frequent flooding and drought events. One system that may contribute to rainfall variability in the region is the mesoscale convective complex (MCC). In this study, Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) data is used to document the precipitation produced by MCCs over southern Africa for the 1998–2006 period. Most of the rainfall associated with MCCs is found to occur over central Mozambique, extending southward to eastern South Africa. High precipitation totals associated with these systems also occur over the neighboring southwest Indian Ocean, particularly off the northeast coast of South Africa. MCCs are found to contribute up to 20% of the total summer rainfall (November–March) in parts of the eastern region of southern Africa. If the month of March is excluded from the analysis, then the contribution increases up to 24%. In general, the MCC summer rainfall contribution for most of the eastern region is approximately between 8% and 16%. Over the western interior and Botswana and Namibia, the MCC contribution is much less (<6%). It is also evident that there is considerable interannual variability associated with the contribution that these systems make to the total warm season rainfall.

Elemental proxy evidence for late Quaternary palaeoenvironmental change in southern African sedimentary records: interpretation and applications

2021 ◽  
Author(s):  
M.S. Humphries
Keyword(s):  
Environmental Change ◽  
Southern Africa ◽  
Southern Oscillation ◽  
Late Quaternary ◽  
Rainfall Variability ◽  
Analytical Techniques ◽  
Summer Rainfall ◽  
Geochemical Data ◽  
Complex Nature ◽  
Cape Coast

Abstract Sediments are the most important source of Late Quaternary palaeoclimate information in southern Africa, but have been little studied from a geochemical perspective. However, recent advances in analytical techniques that allow rapid and near-continuous elemental records to be obtained from sedimentary sequences has resulted in the increasing use of elemental indicators for reconstructing climate. This paper explores the diverse information that can be acquired from the inorganic component of sediments and reviews some of the progress that has been made over the last two decades in interpreting the climatic history of southern Africa using elemental records. Despite the general scarcity of elemental records, excellent examples from the region exist, which provide some of the longest and most highly resolved sequences of environmental change currently available. Records from Tswaing crater and marine deposits on the southern KwaZulu-Natal coastline have provided rare glimpses into hydroclimate variability over the last 200 000 years, suggesting that summer rainfall in the region responded predominantly to insolation forcing on glacial-interglacial timescales. Over shorter timescales, lakes and wetlands found in the Wilderness embayment on the southern Cape coast and along the Maputaland coast in north-eastern South Africa have yielded highly-resolved elemental records of Holocene environmental change, providing insight into the changing interactions between tropical (e.g., El Niño-Southern Oscillation) and temperate (e.g., mid-latitude westerlies) climate systems affecting rainfall variability in the region. The examples discussed demonstrate the multiple environmental processes that can be inferred from elemental proxies and the unique insight this can provide in advancing our understanding of past climate change on different timescales. The interpretation of geochemical data can be complicated by the complex nature of sedimentary environments, various proxy assumptions and analytical challenges, and the reliability of sediment-based climate reconstructions is substantially enhanced through multi-proxy approaches.

scholarly journals Intraseasonal variability in the South American monsoon system

2011 ◽  
Vol 12 (3) ◽  
pp. 253-260 ◽  
Author(s):  
Solange Aragão Ferreira ◽  
Manoel Alonso Gan
Keyword(s):  
Intraseasonal Variability ◽  
South American ◽  
The South ◽  
South American Monsoon ◽  
Monsoon System ◽  
South American Monsoon System

scholarly journals - The genus Stylosanthes (Fabaceae, Papilionoideae, Dalbergieae) in South America.

2017 ◽  
Vol 52 (3) ◽  
pp. 549-585 ◽  
Author(s):  
Ricardo O. Vanni
Keyword(s):  
South America ◽  
World Wide ◽  
Herbarium Specimens ◽  
South American ◽  
Field Observations ◽  
New Synonyms ◽  
Brazilian Species ◽  
The Tropics ◽  
Flora Of Argentina

The papilionoid genus Stylosanthes Sw. includes about 50 spp. distributed world wide in the tropics, approximately half of them grow in South America.The present study focuses on South American Stylosanthes. Based on examinations of herbarium specimens, as well as field observations, a total of 25 taxa (23 spp. and 2 varieties) are here described and identified with a key. Most of the species have been found to be more widely distributed than expected from the previous taxonomic literature, and the genus appears to be mainly concentrated in Brazil and Paraguay. Stylosanthes leiocarpa Vogel is new to the flora of Argentina and the presence of S. nervosa J. F. Macbr. is confirmed in Argentina. The nomenclature of S. guianensis (Aubl.) Sw. is analyzed. Clarifications are made about nine recently described Brazilian species. The names S. hispida Rich. and S. longiseta Micheli are resurrected. Lectotypes or neotypes for eight species and 18 new synonyms are proposed.

scholarly journals Late Quaternary Variations in the South American Monsoon System as Inferred by Speleothems—New Perspectives using the SISAL Database

Quaternary ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 6 ◽  
Author(s):  
Michael Deininger ◽  
Brittany Marie Ward ◽  
Valdir F. Novello ◽  
Francisco W. Cruz
Keyword(s):  
South America ◽  
Late Quaternary ◽  
Precipitation Amount ◽  
Ice Age ◽  
Convergence Zone ◽  
South American ◽  
The South ◽  
South American Monsoon ◽  
Monsoon System ◽  
South American Monsoon System

Here we present an overview of speleothem δ18O records from South America, most of which are available in the Speleothem Isotopes Synthesis and Analysis (SISAL_v1) database. South American tropical and subtropical speleothem δ18O time series are primarily interpreted to reflect changes in precipitation amount, the amount effect, and consequently history of convection intensity variability of convergence zones such as the Intertropical Convergence Zone (ITCZ) and the South America Monsoon System (SAMS). We investigate past hydroclimate scenarios in South America related to the South American Monsoon System in three different time periods: Late Pleistocene, Holocene, and the last two millennia. Precession driven summertime insolation is the main driver of convective variability over the continent during the last 120 kyrs (from present day to 120 kyrs BP), including the Holocene. However, there is a dipole between speleothem δ18O records from western and eastern South America. Records located in the central region of Brazil are weakly affected by insolation-driven variability, and instead are more susceptible to the variability associated with the South Atlantic Convergence Zone (SACZ). Cold episodic events in the Northern Hemisphere, such as Heinrich and Bond Events, and the Little Ice Age, increase the convective activity of the SAMS, resulting in increased precipitation amount in South America.

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.

The Influence on Summer Rainfall in the Lesotho Lowlands from Indian Ocean SSTs

2002 ◽  
Vol 33 (4) ◽  
pp. 305-318 ◽  
Author(s):  
Lars Hydén
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
Rainfall Variability ◽  
Austral Summer ◽  
Equatorial Indian Ocean ◽  
Summer Rainfall ◽  
Significant Negative Correlation ◽  
Annual Rainfall ◽  
Ocean Area ◽  
The Indian Ocean

Lesotho is located approximately at latitude 30 degrees south in the interior of Southern Africa. The mesoscale climate is complicated and governed by various weather systems. The inter-annual rainfall variability is great, resulting in low food security, since the growing of crops in the Lesotho Lowlands is almost exclusively rain-fed. Reliable forecasts of austral summer rainfall are thus valuable. Earlier research has shown that the sea surface temperatures (SST) in the Indian Ocean to some extent govern rainfall in Southern Africa. The research presented is part of an on-going project to find suitable oceanographic and meteorological predictors, which can be used in a forecast model for summer rainfall, to be developed later. The first part of this paper investigates the correlation between the average SSTs in the Equatorial Indian Ocean, the Central Indian Ocean, and the Agulhas Gyre, respectively, and rainfall two months later in the Lesotho Lowlands during early austral summer, October until December for the period 1949-1995. No significant correlations have been found, probably because the three ocean areas are too large. In the second part of this paper the monthly SST in 132 grid squares in the Indian Ocean were investigated and found to be correlated with rainfall in the Lesotho Lowlands two months later, October until March. Significant correlations have been found between the SSTs and certain ocean areas and December, January, and February rainfall, respectively. There is significant negative correlation between December rainfall and October SST in an ocean area between Kenya and Somalia across the Indian Ocean to Sumatra. In the area where the Somali Current flows there is also significant correlation between December SST and December rainfall. January rainfall is significantly negatively correlated with November SST in an ocean area, northeast of Madagascar. February rainfall is significantly, but weakly, negatively correlated with SST in a narrow north-south corridor in the Eastern Indian Ocean from the equator down to latitude 40 degrees south.

scholarly journals Daily Precipitation Statistics for South America: An Intercomparison between NCEP Reanalyses and Observations

2011 ◽  
Vol 12 (1) ◽  
pp. 101-117 ◽  
Author(s):  
Viviane B. S. Silva ◽  
Vernon E. Kousky ◽  
R. Wayne Higgins
Keyword(s):  
South America ◽  
Large Scale ◽  
Atmospheric Model ◽  
Northeastern Brazil ◽  
South American ◽  
The South ◽  
Wet Season ◽  
Central Brazil ◽  
Monsoon System ◽  
Dry Bias

Abstract In this study, the authors document the extent to which the precipitation statistics of the new CFS reanalysis (CFSR) represent an improvement over the earlier reanalyses: the NCEP–NCAR reanalysis (R1) and the NCEP–DOE Second Atmospheric Model Intercomparison Project (AMIP-II) reanalysis (R2). An intercomparison between the CFSR, R1, R2, and observations over South America was made for the period 1979–2006. The CFSR shows notable improvements in the large-scale precipitation patterns compared with the previous reanalyses (R1 and R2). In spite of these improvements, the CFSR has substantial biases in intensity and frequency of occurrence of rainfall events. Over west-central Brazil, the core region of the South American monsoon system (SAMS), the CFSR displays a dry bias during the onset phase of the SAMS wet season and a wet bias during the peak and decay phases of the SAMS wet season. The CFSR also displays a dry bias along the South American coast near the mouth of the Amazon and along the east coast of northeastern Brazil. A wet bias exists in all seasons over southeast Brazil and over the Andes Mountains.

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.

Precipitation Characteristics of the South American Monsoon System Derived from Multiple Datasets

2012 ◽  
Vol 25 (13) ◽  
pp. 4600-4620 ◽  
Author(s):  
Leila M. V. Carvalho ◽  
Charles Jones ◽  
Adolfo N. D. Posadas ◽  
Roberto Quiroz ◽  
Bodo Bookhagen ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
Austral Summer ◽  
Global Precipitation Climatology Project ◽  
South American ◽  
The South ◽  
Frequency Distributions ◽  
South American Monsoon ◽  
Monsoon System ◽  
South American Monsoon System

Abstract The South American monsoon system (SAMS) is the most important climatic feature in South America and is characterized by pronounced seasonality in precipitation during the austral summer. This study compares several statistical properties of daily gridded precipitation from different data (1998–2008): 1) Physical Sciences Division (PSD), Earth System Research Laboratory [1.0° and 2.5° latitude (lat)/longitude (lon)]; 2) Global Precipitation Climatology Project (GPCP; 1° lat/lon); 3) Climate Prediction Center (CPC) unified gauge (CPC-uni) (0.5° lat/lon); 4) NCEP Climate Forecast System Reanalysis (CFSR) (0.5° lat/lon); 5) NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis (0.5° lat/0.3° lon); and 6) Tropical Rainfall Measuring Mission (TRMM) 3B42 V6 data (0.25° lat/lon). The same statistical analyses are applied to data in 1) a common 2.5° lat/lon grid and 2) in the original resolutions of the datasets. All datasets consistently represent the large-scale patterns of the SAMS. The onset, demise, and duration of SAMS are consistent among PSD, GPCP, CPC-uni, and TRMM datasets, whereas CFSR and MERRA seem to have problems in capturing the correct timing of SAMS. Spectral analyses show that intraseasonal variance is somewhat similar in the six datasets. Moreover, differences in spatial patterns of mean precipitation are small among PSD, GPCP, CPC-uni, and TRMM data, while some discrepancies are found in CFSR and MERRA relative to the other datasets. Fitting of gamma frequency distributions to daily precipitation shows differences in the parameters that characterize the shape, scale, and tails of the frequency distributions. This suggests that significant uncertainties exist in the characterization of extreme precipitation, an issue that is highly important in the context of climate variability and change in South America.

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