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A characterization of the diurnal cycle of precipitation (DCP) over the whole South America is still lacking in the literature and the scarcity of sub‐daily rain ground measurements limits the data available for analysis and forbids a correct validation of alternative datasets. In this paper we analyse the climatological mean DCP during the monsoon active season using five gridded datasets: two satellite precipitation estimates, two regional climate models and one reanalysis. Amazonia, the Brazilian Highlands, the northeastern South American coast, the Andes and the western Colombian coast are identified as the areas with most prominent DCPs. The afternoon convection triggered by solar heating over land and the coastal and topographic effects are the main modes of sub‐daily variability, based on an EOF decomposition of the 3 hourly mean precipitation fields. We explore the contribution of mean frequency and intensity to amount of precipitation and nighttime–daytime differences. In general, both models precipitate earlier and more frequently than the satellite products and do not reproduce correctly areas of observed predominant nighttime precipitation where mesoscale convective systems are active, like La Plata Basin or Amazonia. Over the analysed areas, the high frequency of precipitation is the driving mechanism of total amount in the models, whereas in the satellite products there is also considerable contribution from intensity. Overall, the reanalysis shows features in between the models and the satellite estimates, sharing characteristics with both types of data. The results presented here point at the diversity of sub‐daily precipitation characteristics in South America, the issues with conventional climate models and the uncertainty in satellite products and reanalyses. The growing interest in the DCP by the scientific community and the development of new techniques like convection permitting modelling will hopefully continue to improve our knowledge of the precipitation dynamics and its influence on climate. [ABSTRACT FROM AUTHOR]

ABSTRACT It is known that the El Niño - Southern Oscillation ( ENSO) episodes have a great influence on South American precipitation and its extreme events during austral autumn (from March until May, MAM) and winter (from June until August, JJA) that occur after the ENSO peak (normally this happens on austral summer). Recent papers have studied the two types of ENSO and their influence on atmosphere-ocean system. This study analysed the influence of Central and East equatorial Pacific ENSO on South American seasonal/monthly mean precipitation and its extreme events during MAM and JJA. The composites of precipitation anomalies, during these two types of ENSO, show that there are different, even opposite patterns over South America. In MAM, there is an increased precipitation in southeastern South America and a decrease in the northeast South America during East El Niño ( EEN) and an increased precipitation in central Brazil during Central El Niño ( CEN). In JJA, the signs of anomaly precipitation are opposite between CEN (less precipitation) and EEN (more precipitation) over southeastern South America. The extreme precipitation events show patterns consistent with the precipitation anomaly patterns, but, normally, the changes in the frequency of extremes precipitation events affect more extensive areas than the total precipitation. If monthly or seasonal atmospheric anomalies in a certain region during one of the types of ENSO are similar (opposite) to the atmospheric anomalies associated with extreme precipitation events in this region, then there is enhancement (suppression) of the frequency of extreme events in this region during this type of ENSO. [ABSTRACT FROM AUTHOR]

The Eastern Pacific (EP) and Central Pacific (CP) El Niño‐Southern Oscillation (ENSO) types and their impacts on the tropical North Atlantic (TNA) SST variability and 15°N–15°S South American precipitation during the warm and cold phases of the Atlantic Multidecadal Oscillation (WAMO and CAMO) were evaluated during the 1901–2012 period. The results show more frequent ENSO events during the CAMO. The El Niño (EN) (La Niña [LN]) events, regardless of type (EP or CP), during the WAMO (CAMO) were accompanied by a warming (cooling) in the TNA after its mature phases. In these cases, extratropical teleconnection patterns are established through variations in the Pacific/North America (PNA) teleconnection pattern and are accompanied by variations in the Walker circulation. For the EN (LN) in the CAMO (WAMO), the tropical teleconnections occur predominant, through the Walker cell and the zonal inter‐basin gradient, which is intensified due to the SST gradient between the eastern equatorial Pacific (non‐neutral anomalies) and the equatorial Atlantic (neutral anomalies). These circulation pattern changes affect the precipitation patterns in the 15°N–15°S South American sector during December–January–February (D(0)JF(+1)) and March–April–May (MAM(+1)). The EP EN (EPEN) events are associated with the intensification of the negative precipitation anomalies in northeastern Brazil (NEB) during the WAMO and in the central part of the Amazon during the CAMO. In the case of CP EN (CPEN) events, the greatest differences between the AMO phases occur during MAM(+1), with reverse sign anomalies over northwestern South America. In the case of LN events, the largest differences occur in NEB, with reduced rainfall in the WAMO, regardless of type EP or CP. The results presented here highlight the role of low frequency oscillations in defining the teleconnection patterns between tropical Pacific and Atlantic Oceans, not discussed previously. [ABSTRACT FROM AUTHOR]

Precipitation, low‐level flow and atmospheric moisture transport fields over the Intra‐Americas region from a Weather Research and Forecasting model (WRF) multi‐decadal simulation are presented. The period of analysis is 1982–2012, and the focus is on mean monthly states and their variability. WRF results are compared to global precipitation products and to the Interim Reanalysis from the ECWMF (ERA‐Interim). An analysis of the coupling between precipitation over northern South America and regional scale sea surface temperatures (SSTs) and winds within ERA‐Interim and WRF is also presented. Over land, precipitation biases in WRF are mostly positive, especially over Central America and northern South America. This bias is associated with an excess in atmospheric moisture convergence in WRF compared to ERA‐Interim, which in turn is related to stronger low‐level circulation structures and differences in the moisture transport field between WRF and ERA‐Interim at the regional scale. The largest differences in the flow are observed over the eastern Pacific, where the flow is correlated with precipitation over southern Mexico, Central America and northern South America during the boreal summer. During early winter, correlation patterns of WRF precipitation and SST anomalies over the tropical Pacific are substantially weaker over western Texas and northwestern South America compared to the coupling between the global precipitation products and observed SSTs. For northwestern South America, the low correlation seems to be associated to a lack of coupling between regional scale winds and SST anomalies. During the boreal summer, the coupling between Caribbean SSTs and precipitation over parts of Mexico and Central America is stronger in WRF compared to observation‐based products. Precipitation over northern South America is sensitive to sea surface temperature (SST) anomalies over the Pacific, especially during the driest season December–January. This relationship is evident in the correlation between SSTs over the Pacific and Global Precipitation Climatology Centre (GPCC)‐precipitation over the Colombian Andes (brown contours, top‐left panel). However, a regional climate simulation with Weather Research and Forecasting (WRF) does not show such coupling during the early dry season (top right). This behaviour seems to be a consequence of the lack of coupling between regional‐scale moisture transport and SSTs in WRF. [ABSTRACT FROM AUTHOR]

ABSTRACT Recent studies show that different types of ENSO influence the atmospheric fields differently. In this study, precipitation anomalies and extreme events over South America are analysed with relation to two types of ENSO [East (strong Sea Surface Temperature Anomalies (SSTA) on East Pacific) and Central (strong SSTA on Central Pacific)]. The composites of precipitation anomalies, during these two types of ENSO, show that there are different patterns, e.g. during austral summer of Central El Niño (CEN) there are negative precipitation anomalies in eastern Brazil that do not exist in East El Niño (EEN), whereas in southern Brazil there are positive precipitation anomalies during EEN that do not exist in CEN. Furthermore, the anomalies are mostly stronger and more extensive during EEN (Central La Niña - CLN) than in CEN (East La Niña - ELN), although there are some exceptions, such as during austral spring in southern Brazil, where anomalies during CEN (ELN) are stronger than during EEN (CLN). The anomalous frequency of extreme precipitation events shows generally patterns consistent with the anomalous precipitation behaviour, though the patterns are not always coincident, because the regions with significant increase of frequency of extreme events tend to be more extensive than those with increased seasonal precipitation. When the monthly or seasonal atmospheric anomalies associated with a type of ENSO episode are very similar (opposite) to the atmospheric anomalies associated with extreme precipitation in a certain region, then a significant enhancement (suppression) of the frequency of extreme events is observed in that region during this type of episode. [ABSTRACT FROM AUTHOR]

ABSTRACT This article quantifies the relationship between sea ice cover ( SIC) on the Southern Ocean and precipitation and river discharges over southeastern and eastern South America. The period of analysis covers from 1981 to 2008 and includes monthly mean data of SIC over the Ross, Amundsen-Bellingshausen and Weddell Seas, as well as atmospheric variables and discharges of selected rivers in eastern South America. To isolate the effect of known modes of climate variability on SIC, the signals of El Niño-Southern Oscillation and the Southern Annual Mode are removed from all time series through regression analysis. Composites of precipitation differences over South America reveal a pattern of enhanced rainfall activity over the South Atlantic Convergence Zone ( SACZ) in summer ( JFM) when SIC is above average particularly over the Weddell Sea area, while winter ( ASO) SIC anomalies show negative and significant correlations with rainfall over much of South America. Moisture fluxes patterns in summer reveal increased moisture transport towards the SACZ region and decreased low-level jet activity (and precipitation) over northern Argentina. In particular a large dry bias over southeastern South America associated to positive SIC anomalies on the Weddell Sea in September is shown to impact the discharges of the Uruguay and Iguazú Rivers, with the largest effects found two months after the SIC anomaly (November). Although less robust, a relationship with the Paraná River is also found. These results suggest that increased SIC over the Weddell Sea during September can help to forecast drier conditions particularly on the Uruguay basin and somewhat wetter conditions in the SACZ region within the following season. [ABSTRACT FROM AUTHOR]

Sea surface temperature (SST) anomalies in the Pacific Ocean during El Niño-Southern Oscillation (ENSO) episodes exhibit different spatial patterns from year to year. In most ENSO studies, SST anomalies have been analysed in the 3.4 or 3.0 El Niño regions. Recent analyses have considered different SST anomalies areas in the Pacific, such as ENSO Modoki, which takes into account anomalies in the central Pacific which are bounded by opposite anomalies in the eastern and western Pacific. In order to analyse the influence of different Pacific spatial patterns on South American precipitation and on the Southern Hemisphere atmospheric circulation, composites obtained from Canonical ENSO were compared with those from ENSO Modoki in cases when strong anomalies were present in the Central Pacific. During the Canonical El Niño (La Niña), there tends to be a precipitation increase (decrease) in the La Plata Basin (LPB, 45°W-65°W, 15°S-35°S) and a decrease (increase) over northern South America during all seasons. In ENSO Modoki exhibiting strong anomalies in the Central Pacific, these typical patterns are not observed, and in some regions the anomalies even show opposite signs. Precipitation anomaly differences or similarities over South America between the two cases occur in different areas and different seasons. In both cases, differences in tropical South American precipitation during both ENSO types are related to differences in the Walker circulation. In extra-tropical South America, the precipitation differences are due to differences in the Pacific wavetrains and differences in moisture flux intensity over the continent. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The National Centers for Environmental Prediction (NCEP) ETA regional circulation model (RCM) was one-way nested in the T62 NCEP general circulation model for a series of 3-month simulations of the austral summer and winter over South America (SA). The intensity-scale verification technique (ISVT), based on the scale decomposition of precipitation skill score and energy relative difference, was used to quantitatively assess the dynamic-downscaling ability of seasonal precipitation and inter-annual precipitation difference. The ISVT showed that the RCM was able to add value to summer and winter rainfall forecasts over southern South America. Largest improvements were associated to precipitation events at spatial scales of about 400-800 km and rainfall rates above 4 mm day. In general, downscaling failed to yield better results over northern South America. In terms of inter-annual precipitation difference, the RCM produced better results over southern South America, by simulating the increase in intense small-scale events in the wet years. Analysis of meridional moisture flux associated with the South American low-level jet (SALLJ) suggested that the Andean topography plays an important role in the RCM's rainfall simulations over the La Plata basin. A sensitivity test with lowered Andean topography heights produced weaker moisture advection by the SALLJ, and lower rainfall totals over that basin for both seasons. During summer, results showed that the reduced rainfall was associated with deteriorated simulations of mid- to large-scale precipitation events, whereas during winter it was associated with deteriorated simulations of smaller-scale events. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The South American Monsoon System (SAMS) is characterised by intense convective activity and precipitation during austral summer. This study investigates changes in the onset, demise and duration of SAMS during 1948-2008. The results show a significant change in these characteristics in the early 1970s. Onset becomes steadily earlier from 1948 to early 1970s and has occurred earlier than 23-27 October after 1972-1973. Demise dates have remained later than 21-25 April after the mid-to-late 1970s. SAMS duration shows a statistical changepoint in the summer of 1971-1972 such that the mean duration was ∼170 days (1948-1972) and 195 days (1972-1982). Vertically integrated moisture flux is used to diagnose changes in mean state and reveal statistically significant increases over South America after 1971-1972. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The article presents a study on the temperature and precipitation extreme in South America based on the Providing Regional Climate for Impacts Studies (PRECIS) regional climate modeling (RCM) system. The study compared the simulation trends in the 1961-1990 of the HadRM3P, the RCM within PRECIS, with the actual observations. It reveals that HadRM3P simulated trends show the similarity in the patterns of negative trends in the cold nights in South America and Southeastern South America.

The article presents a study which evaluates the energy cycle of South America during rainy seasons with the use of the multivariate Empirical Orthogonal Function (EOF) analysis. It states that precipitation during rainy seasons affect the economic activities of the country. The study also used the linear regression analysis and examined the consistency of physical processes. It concludes that the timing of tropical and extratropical circulations is fast which is said to be quite consistent.