The Madden–Julian Oscillation (MJO) is the leading driver of intraseasonal rainfall variability in the global tropics. However, the influence of MJO on western tropical South America (WTSA) has not ...been a focus of research. This is not surprising since the MJO convective core becomes nondescript as it propagates across the eastern Pacific, such that its influence on the Pacific coast of tropical South America is not obvious in global analyses. In this study, we examine MJO impacts on subseasonal rainfall variability in the rainiest season for WTSA (February–April). In order to avoid confusion with El Niño Southern Oscillation (ENSO) signals, only ENSO-neutral years are included in the analysis. We found that the MJO convective core reemerges when it propagates onto land in WTSA, and that it is associated with subseasonal precipitation anomalies of 20–50% relative to climatology. The MJO signal is evident in the real-time multivariate MJO (RMM) index; however, the signal is clearer when a custom subseasonal index for the region based on WTSA outgoing longwave radiation is employed. Dynamically, the MJO influence is consistent with a modulation of the Pacific Ocean Walker Circulation descending branch, which is climatologically located in or near WTSA. Furthermore, MJO drives zonal and vertical motions on moisture and wind fields that influence precipitation in the region. We found that the timing of deep convection on subseasonal timescales captured by the regional index is consistent with a dominant role of the MJO convective core, rather than propagation of equatorial Rossby or Kelvin waves. However, there is evidence that equatorial Rossby waves that emerge over the tropical Atlantic Ocean also influence precipitation in WTSA on MJO timescales.
Dengue fever, a mosquito-borne viral disease, is a rapidly emerging public health problem in Ecuador and throughout the tropics. However, we have a limited understanding of the disease transmission ...dynamics in these regions. Previous studies in southern coastal Ecuador have demonstrated the potential to develop a dengue early warning system (EWS) that incorporates climate and non-climate information. The objective of this study was to characterize the spatiotemporal dynamics and climatic and social-ecological risk factors associated with the largest dengue epidemic to date in Machala, Ecuador, to inform the development of a dengue EWS.
The following data from Machala were included in analyses: neighborhood-level georeferenced dengue cases, national census data, and entomological surveillance data from 2010; and time series of weekly dengue cases (aggregated to the city-level) and meteorological data from 2003 to 2012. We applied LISA and Moran's I to analyze the spatial distribution of the 2010 dengue cases, and developed multivariate logistic regression models through a multi-model selection process to identify census variables and entomological covariates associated with the presence of dengue at the neighborhood level. Using data aggregated at the city-level, we conducted a time-series (wavelet) analysis of weekly climate and dengue incidence (2003-2012) to identify significant time periods (e.g., annual, biannual) when climate co-varied with dengue, and to describe the climate conditions associated with the 2010 outbreak.
We found significant hotspots of dengue transmission near the center of Machala. The best-fit model to predict the presence of dengue included older age and female gender of the head of the household, greater access to piped water in the home, poor housing condition, and less distance to the central hospital. Wavelet analyses revealed that dengue transmission co-varied with rainfall and minimum temperature at annual and biannual cycles, and we found that anomalously high rainfall and temperatures were associated with the 2010 outbreak.
Our findings highlight the importance of geospatial information in dengue surveillance and the potential to develop a climate-driven spatiotemporal prediction model to inform disease prevention and control interventions. This study provides an operational methodological framework that can be applied to understand the drivers of local dengue risk.
Abstract Hydrological predictions at subseasonal-to-seasonal (S2S) time scales can support improved decision-making in climate-dependent sectors like agriculture and hydropower. Here, we present an ...S2S hydrological forecasting system (S2S-HFS) for western tropical South America (WTSA). The system uses the global NASA Goddard Earth Observing System S2S meteorological forecast system (GEOS-S2S) in combination with the generalized analog regression downscaling algorithm and the NASA Land Information System (LIS). In this implementation study, we evaluate system performance for 3-month hydrological forecasts for the austral autumn season (March–May) using ensemble hindcasts for 2002–17. Results indicate that the S2S-HFS generally offers skill in predictions of monthly precipitation up to 1-month lead, evapotranspiration up to 2 months lead, and soil moisture content up to 3 months lead. Ecoregions with better hindcast performance are located either in the coastal lowlands or in the Amazon lowland forest. We perform dedicated analysis to understand how two important teleconnections affecting the region are represented in the S2S-HFS: El Niño–Southern Oscillation (ENSO) and the Antarctic Oscillation (AAO). We find that forecast skill for all variables at 1-month lead is enhanced during the positive phase of ENSO and the negative phase of AAO. Overall, this study indicates that there is meaningful skill in the S2S-HFS for many ecoregions in WTSA, particularly for long memory variables such as soil moisture. The skill of the precipitation forecast, however, decays rapidly after forecast initialization, a phenomenon that is consistent with S2S meteorological forecasts over much of the world.
In Ecuador, forecasts of seasonal total rainfall could mitigate both flooding and drought disasters through warning systems if issued at useful lead time. In Ecuador, rainfall from December to April ...contributes most of the annual total, and it is crucial to agricultural and water management. This study examines the predictive skill for February–April and December–February seasonal rainfall totals using statistical and dynamical approaches. Fields of preceding observed sea surface temperature (SST) are used as predictors for a purely statistical prediction, and predictions of an atmospheric general circulation model (AGCM) are used as predictors with a model output statistics correction design using canonical correlation analysis. For both periods, results indicate considerable predictive skill in some, but not all, portions of the Andean and especially coastal regions. The skill of SST and AGCM predictors comes mainly through skillful rainfall anomaly forecasts during significant ENSO events. Atlantic Ocean SST plays a weaker predictive role. For the simultaneous diagnostic highest skill is obtained using the eastern Pacific Ocean domain, and for time-lagged forecasts highest scores are found using the global tropical ocean domain. This finding suggests that, while eastern Pacific SST is what matters most to Ecuadorian rainfall, at sufficient lead time these local SSTs become most effectively predicted using basinwide ENSO predictors. In Ecuador’s coastal region, and in some parts of the Andean highlands, skill levels are sufficient for warning systems to reduce economic losses associated with flood and drought. Accordingly, the Instituto Nacional Meteorologia e Hidrologia of Ecuador issues forecasts each month using methods described here—also implemented by countries of the Latin American Observatory partnership, among other South American organizations.
Stabilization and solidification mixtures of contaminated material with 60% weathered, oily crust, and 40% sediment were made, and acute toxicity (
Vibrio fischeri
bioassay), hydrocarbons in ...leachates, and resistance to compression were determined. For stabilized materials, the hydrocarbon concentration expected in base soil (underneath stabilization cells) was calculated from hydrocarbon concentrations in laboratory leachates using a modified test that better simulates real site conditions (acid extraction of complete formed blocks). In the modified tests, an asymptotic behavior in the hydrocarbon concentration in leachates was observed, nearing a maximum after 15 days. The calculated hydrocarbon concentration in base soil was < 3000 mg/Kg in all concentrations of agglomerate and pozzolan used (3.75–15% CaO, 1.25–5.0% diatomaceous earth). Acute toxicity was null or indeterminate with respect to background levels. For solidified materials, in two of the treatments (3.75 and 7.5% CaO, 1.25 and 3.75% diatomaceous earth; plus gravelly backfill at 1:1), unconfined resistance to compression was sufficient for the material to be used as sub-base for rural roads (> 17.6 ton/m
2
), but with higher concentrations of reagents (15% CaO, 5% diatomaceous earth; plus gravelly backfill at 1:1), the resistance was insufficient. In all solidification treatments, no toxicity above background was encountered, and Total Petroleum Hydrocarbons in leachate tests resulted in calculated hydrocarbon concentrations in base soil of < 3000 mg/Kg. From these data, it was concluded that stabilization and solidification were feasible for this site using low concentrations of reagents, and that it was not necessary to use a plastic liner to prevent subsoil contamination.
Artificial soil mixtures were prepared with 10–40% of either kaolinite or bentonite clay, plus
Sphagnum
moss, and clean sand. Mixtures were placed in plastic containers in the field, and let mature ...for six months (in a tropical climate). They were then contaminated with 3% of either light, medium or heavy crude oil, and let weather for another six months. Afterward, compaction was measured in the field, and core samples were taken for laboratory determinations. No correlation was found between soil density and compaction, and it appeared that some of the density determinations were unreliable due to interferences from the petroleum. Compaction was low (< 0.5 MPa) for smectite-based soil, but much higher (up to 1.24 MPa) in kaolinite-based soil, especially with higher clay levels contaminated with heavy crude. Water repellency for kaolinite-based soil was low to null (especially for 30 and 40% clay), but repellency for smectite-based soil was three orders of magnitude higher, in the severe to extreme range. However, it is uncertain whether these laboratory determinations on smectite-based soils could be applied to the field. Regional, smectite-rich soils tend to be moist and low-lying in the landscape, unlikely to manifest water repellency, even during the dry season. Field capacity in smectite-based soil showed low impacts (reductions of 0–1% of moisture content with higher amounts of clay), but kaolinite-based soil showed considerable reduction, especially at 30% clay (being 15% less). The importance of these results for contamination, characterization and remediation of regional soils is discussed, as well as recommendations for future research.
Quality and compositional changes were determined in noni fruit harvested at five ripening stages, from dark-green to thaslucent-grayish. Fruit ripening was accompanied by acidity and soluble solids ...accumulation but pH diminution, whereas the softening profile presented three differential steps named early (no significant softening), intermediate (significant softening), and final (dramatic softening). At early step the extensive depolymerization of hydrosoluble pectins and the significantly increment of pectinase activities did not correlate with the slight reduction in firmness. The intermediate step showed an increment of pectinases and hemicellulases activities. The final step was accompanied by the most significant reduction in the yield of alcohol-insoluble solids as well as in the composition of uronic acids and neutral sugars; pectinases increased their activity and depolymerization of hemicellulosic fractions occurred. Noni ripening is a process conducted by the coordinated action of pectinases and hemicellulases that promote the differential dissasembly of cell wall polymers.
A weeklong workshop in Brazil in August 2004 provided the opportunity for 28 scientists from southern South America to examine daily rainfall observations to determine changes in both total and ...extreme rainfall. Twelve annual indices of daily rainfall were calculated over the period 1960 to 2000, examining changes to both the entire distribution as well as the extremes. Maps of trends in the 12 rainfall indices showed large regions of coherent change, with many stations showing statistically significant changes in some of the indices. The pattern of trends for the extremes was generally the same as that for total annual rainfall, with a change to wetter conditions in Ecuador and northern Peru and the region of southern Brazil, Paraguay, Uruguay, and northern and central Argentina. A decrease was observed in southern Peru and southern Chile, with the latter showing significant decreases in many indices. A canonical correlation analysis between each of the indices and sea surface temperatures (SSTs) revealed two large-scale patterns that have contributed to the observed trends in the rainfall indices. A coupled pattern with ENSO-like SST loadings and rainfall loadings showing similarities with the pattern of the observed trend reveals that the change to a generally more negative Southern Oscillation index (SOI) has had an important effect on regional rainfall trends. A significant decrease in many of the rainfall indices at several stations in southern Chile and Argentina can be explained by a canonical pattern reflecting a weakening of the continental trough leading to a southward shift in storm tracks. This latter signal is a change that has been seen at similar latitudes in other parts of the Southern Hemisphere. A similar analysis was carried out for eastern Brazil using gridded indices calculated from 354 stations from the Global Historical Climatology Network (GHCN) database. The observed trend toward wetter conditions in the southwest and drier conditions in the northeast could again be explained by changes in ENSO.
A workshop on enhancing climate change indices in South America was held in Maceió, Brazil, in August 2004. Scientists from eight southern countries brought daily climatological data from their ...region for a meticulous assessment of data quality and homogeneity, and for the preparation of climate change indices that can be used for analyses of changes in climate extremes. This study presents an examination of the trends over 1960–2000 in the indices of daily temperature extremes. The results indicate no consistent changes in the indices based on daily maximum temperature while significant trends were found in the indices based on daily minimum temperature. Significant increasing trends in the percentage of warm nights and decreasing trends in the percentage of cold nights were observed at many stations. It seems that this warming is mostly due to more warm nights and fewer cold nights during the summer (December–February) and fall (March–May). The stations with significant trends appear to be located closer to the west and east coasts of South America.
Although malaria control investments worldwide have resulted in dramatic declines in transmission since 2000, progress has stalled. In the Amazon, malaria resurgence has followed withdrawal of Global ...Fund support of the Project for Malaria Control in Andean Border Areas (PAMAFRO). We estimate intervention-specific and spatially-explicit effects of the PAMAFRO program on malaria incidence across the Loreto region of Peru, and consider the influence of the environmental risk factors in the presence of interventions.
We conducted a retrospective, observational, spatial interrupted time series analysis of malaria incidence rates among people reporting to health posts across Loreto, Peru between the first epidemiological week of January 2001 and the last epidemiological week of December 2016. Model inference is at the smallest administrative unit (district), where the weekly number of diagnosed cases of Plasmodium vivax and Plasmodium falciparum were determined by microscopy. Census data provided population at risk. We include as covariates weekly estimates of minimum temperature and cumulative precipitation in each district, as well as spatially- and temporally-lagged malaria incidence rates. Environmental data were derived from a hydrometeorological model designed for the Amazon. We used Bayesian spatiotemporal modeling techniques to estimate the impact of the PAMAFRO program, variability in environmental effects, and the role of climate anomalies on transmission after PAMAFRO withdrawal.
During the PAMAFRO program, incidence of P. vivax declined from 42.8 to 10.1 cases/1000 people/year. Incidence for P. falciparum declined from 14.3 to 2.5 cases/1000 people/year over this same period. The effects of PAMAFRO-supported interventions varied both by geography and species of malaria. Interventions were only effective in districts where interventions were also deployed in surrounding districts. Further, interventions diminished the effects of other prevailing demographic and environmental risk factors. Withdrawal of the program led to a resurgence in transmission. Increasing minimum temperatures and variability and intensity of rainfall events from 2011 onward and accompanying population displacements contributed to this resurgence.
Malaria control programs must consider the climate and environmental scope of interventions to maximize effectiveness. They must also ensure financial sustainability to maintain local progress and commitment to malaria prevention and elimination efforts, as well as to offset the effects of environmental change that increase transmission risk.
National Aeronautics and Space Administration, National Institutes of Health, Bill and Melinda Gates Foundation.
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