scholarly journals “Late-stage” deforestation enhances storm trends in coastal West Africa

2022 ◽  
Vol 119 (2) ◽  
pp. e2109285119
Author(s):  
Christopher M. Taylor ◽  
Cornelia Klein ◽  
Douglas J. Parker ◽  
France Gerard ◽  
Valiyaveetil Shamsudheen Semeena ◽  
...  
Keyword(s):  
West Africa ◽  
Late Stage ◽  
Landscape Heterogeneity ◽  
Sea Breeze ◽  
Mesoscale Dynamics ◽  
Coastal Belt ◽  
Synoptic Forcing ◽  
Storm Frequency ◽  
The Tropics ◽  
The Impact

Deforestation affects local and regional hydroclimate through changes in heating and moistening of the atmosphere. In the tropics, deforestation leads to warming, but its impact on rainfall is more complex, as it depends on spatial scale and synoptic forcing. Most studies have focused on Amazonia, highlighting that forest edges locally enhance convective rainfall, whereas rainfall decreases over drier, more extensive, deforested regions. Here, we examine Southern West Africa (SWA), an example of “late-stage” deforestation, ongoing since 1900 within a 300-km coastal belt. From three decades of satellite data, we demonstrate that the upward trend in convective activity is strongly modulated by deforestation patterns. The frequency of afternoon storms is enhanced over and downstream of deforested patches on length scales from 16 to 196 km, with greater increases for larger patches. The results are consistent with the triggering of storms by mesoscale circulations due to landscape heterogeneity. Near the coast, where sea breeze convection dominates the diurnal cycle, storm frequency has doubled in deforested areas, attributable to enhanced land–sea thermal contrast. These areas include fast-growing cities such as Freetown and Monrovia, where enhanced storm frequency coincides with high vulnerability to flash flooding. The proximity of the ocean likely explains why ongoing deforestation across SWA continues to increase storminess, as it favors the impact of mesoscale dynamics over moisture availability. The coastal location of deforestation in SWA is typical of many tropical deforestation hotspots, and the processes highlighted here are likely to be of wider global relevance.

scholarly journals Chemical characterization and source apportionment of submicron aerosols measured in Senegal during the 2015 SHADOW campaign

2017 ◽  
Author(s):  
Laura-Hélèna Rivellini ◽  
Isabelle Chiapello ◽  
Emmanuel Tison ◽  
Marc Fourmentin ◽  
Anaïs Féron ◽  
...  
Keyword(s):  
West Africa ◽  
Source Apportionment ◽  
Sampling Site ◽  
Chemical Characterization ◽  
Sea Breeze ◽  
Saharan Dust ◽  
High Time Resolution ◽  
Organic Fraction ◽  
Air Masses ◽  
The Impact

Abstract. The present study offers the first chemical characterization of the submicron (PM1) fraction in West Africa at a high time resolution, thanks to collocated measurements of non-refractory (NR) species with an Aerosol Chemical Speciation Monitor (ACSM), black carbon and iron concentrations derived from absorption coefficient measurements with a 7-wavelength aethalometer, and total PM1 determined by a TEOM-FDMS for mass closure. The field campaign was carried out during four months (March to June 2015) as part of the SHADOW (SaHAran Dust Over West Africa) project at a coastal site located in the outskirts of the city of M'Bour, Senegal. With an average mass concentration of 5.4 µg m−3, levels of NR-PM1 in M'Bour were three to ten times lower than cities like Paris or Beijing. Nonetheless the first half of the observation period was marked by intense but short pollution events (concentrations higher than 15 µg m−3), sea breeze phenomena and Saharan desert dust outbreaks (PM10 up to 900 µg m−3). During the second half of the campaign, the sampling site was mainly under the influence of marine air masses. The air masses on days under continental and sea breeze influences were dominated by organics (36–40 %), whereas sulfate particles were predominant (40 %) for days under oceanic influence. Overall, measurements showed that about 3/4 of the total PM1 were explained by NR-PM1, BC and Fe (a proxy for dust) concentrations, leaving ~ 1/4 for other refractory species. A mean value of 4.6 % for the Fe / PM1 ratio was obtained. Source apportionment of the organic fraction, using Positive Matrix Factorization (PMF) highlighted the impact of local combustion sources, such as traffic and residential activities, which contribute on average to 52 % of the total organic fraction. A new organic aerosol (OA) source, representing on average 3 % of the total OA fraction, showed similar variation as non-refractory particulate chloride. Its rose plot and daily pattern pointed out to local combustion processes, that is to say two open waste burning areas located about 6 and 11 km away from the receptor site and to a lesser extent a traditional fish smoking place. The remaining fraction was identified as oxygenated organic aerosols (OOA), a factor that prevailed regardless of the day type (45 %) and was representative of regional but also local sources due to enhanced photochemical processes.

Spatial patterns and trends of extreme rainfall over the southern coastal belt of West Africa

2020 ◽  
Vol 143 (1-2) ◽  
pp. 473-487
Author(s):  
Marc Kpanou ◽  
Patrick Laux ◽  
Télesphore Brou ◽  
Expédit Vissin ◽  
Pierre Camberlin ◽  
...  
Keyword(s):  
West Africa ◽  
Spatial Patterns ◽  
Extreme Rainfall ◽  
Coastal Belt

scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

The impact of the COVID-19 pandemic on stage at diagnosis of breast and colorectal cancers.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 6501-6501
Author(s):  
Jade Zhou ◽  
Shelly Kane ◽  
Celia Ramsey ◽  
Melody Ann Akhondzadeh ◽  
Ananya Banerjee ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Colorectal Cancer ◽  
Cancer Screening ◽  
Late Stage ◽  
Stage Iv ◽  
Stage I ◽  
Screening Programs ◽  
Stage Distribution ◽  
Number Of Patients ◽  
The Impact

6501 Background: Effective cancer screening leads to a substantial increase in the detection of earlier stages of cancer, while decreasing the incidence of later stage cancer diagnoses. Timely screening programs are critical in reducing cancer-related mortality in both breast and colorectal cancer by detecting tumors at an early, curable stage. The COVID-19 pandemic resulted in the postponement or cancellation of many screening procedures, due to both patient fears of exposures within the healthcare system as well as the cancellation of some elective procedures. We sought to identify how the COVID-19 pandemic has impacted the incidence of early and late stage breast and colorectal cancer diagnoses at our institution. Methods: We examined staging for all patients presenting to UCSD at first presentation for a new diagnosis of malignancy or second opinion in 2019 and 2020. Treating clinicians determined the stage at presentation for all patients using an AJCC staging module (8th edition) in the electronic medical record (Epic). We compared stage distribution at presentation in 2019 vs 2020, both for cancers overall and for colorectal and breast cancer, because these cancers are frequently detected by screening. Results: Total numbers of new patient visits for malignancy were similar in 2019 and 2020 (1894 vs 1915 pts), and stage distribution for all cancer patients was similar (stage I 32% in 2019 vs 29% in 2020; stage IV 26% in both 2019 and 2020). For patients with breast cancer, we saw a lower number of patients presenting with stage I disease (64% in 2019 vs 51% in 2020) and a higher number presenting with stage IV (2% vs 6%). Similar findings were seen in colorectal cancer (stage I: 22% vs 16%; stage IV: 6% vs 18%). Conclusions: Since the COVID-19 pandemic, there has been an increase in incidence of late stage presentation of colorectal and breast cancer, corresponding with a decrease in early stage presentation of these cancers at our institution. Cancer screening is integral to cancer prevention and control, specifically in colorectal and breast cancers which are often detected by screening, and the disruption of screening services has had a significant impact on our patients. We plan to continue following these numbers closely, and will present data from the first half of 2021 as it becomes available.

scholarly journals On what scales can GOSAT flux inversions constrain anomalies in terrestrial ecosystems?

2019 ◽  
Author(s):  
Brendan Byrne ◽  
Dylan B. A. Jones ◽  
Kimberly Strong ◽  
Saroja M. Polavarapu ◽  
Anna B. Harper ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Net Ecosystem Exchange ◽  
Terrestrial Ecosystems ◽  
Atmospheric Co2 ◽  
Strong Correlations ◽  
Climate Anomalies ◽  
Temperature And Precipitation ◽  
The Tropics ◽  
Emergent Constraint ◽  
The Impact

Abstract. Interannual variations in temperature and precipitation impact the carbon balance of terrestrial ecosystems, leaving an imprint in atmospheric CO2. Quantifying the impact of climate anomalies on the net ecosystem exchange (NEE) of terrestrial ecosystems can provide a constraint to evaluate terrestrial biosphere models against, and may provide an emergent constraint on the response of terrestrial ecosystems to climate change. We investigate the spatial scales over which interannual variability in NEE can be constrained using atmospheric CO2 observations from the Greenhouse Gases Observing Satellite (GOSAT). NEE anomalies are calculated by performing a series of inversion analyses using the GEOS-Chem model to assimilate GOSAT observations. Monthly NEE anomalies are compared to proxies, variables which are associated with anomalies in the terrestrial carbon cycle, and to upscaled NEE estimates from FLUXCOM. Strong agreement is found in the timing of anomalies in the GOSAT flux inversions with soil temperature and FLUXCOM. Strong correlations are obtained (P  RNINO3.4) in the tropics on continental and larger scales, and in the northern extratropics on sub-continental scales during the summer (R2 ≥ 0.49). These results, in addition to a series of observing system simulation experiments that were conducted, provide evidence that GOSAT flux inversions can isolate anomalies in NEE on continental and larger scales. However, in both the tropics and northern extratropics, the agreement between the inversions and the proxies/FLUXCOM is sensitive to the flux inversion configuration. Our results suggest that regional scales are likely the minimum scales that can be resolved in the tropics using GOSAT observations, but obtaining robust NEE anomaly estimates on these scales may be difficult.

scholarly journals A bias-corrected CMIP5 dataset for Africa using the CDF-t method – a contribution to agricultural impact studies

2018 ◽  
Vol 9 (1) ◽  
pp. 313-338 ◽  
Author(s):  
Adjoua Moise Famien ◽  
Serge Janicot ◽  
Abe Delfin Ochou ◽  
Mathieu Vrac ◽  
Dimitri Defrance ◽  
...  
Keyword(s):  
West Africa ◽  
Air Temperature ◽  
Climate Model ◽  
Global Climate Model ◽  
Cumulative Distribution ◽  
Shortwave Radiation ◽  
Climate Change Scenarios ◽  
Reference Dataset ◽  
Near Surface ◽  
The Impact

Abstract. The objective of this paper is to present a new dataset of bias-corrected CMIP5 global climate model (GCM) daily data over Africa. This dataset was obtained using the cumulative distribution function transform (CDF-t) method, a method that has been applied to several regions and contexts but never to Africa. Here CDF-t has been applied over the period 1950–2099 combining Historical runs and climate change scenarios for six variables: precipitation, mean near-surface air temperature, near-surface maximum air temperature, near-surface minimum air temperature, surface downwelling shortwave radiation, and wind speed, which are critical variables for agricultural purposes. WFDEI has been used as the reference dataset to correct the GCMs. Evaluation of the results over West Africa has been carried out on a list of priority user-based metrics that were discussed and selected with stakeholders. It includes simulated yield using a crop model simulating maize growth. These bias-corrected GCM data have been compared with another available dataset of bias-corrected GCMs using WATCH Forcing Data as the reference dataset. The impact of WFD, WFDEI, and also EWEMBI reference datasets has been also examined in detail. It is shown that CDF-t is very effective at removing the biases and reducing the high inter-GCM scattering. Differences with other bias-corrected GCM data are mainly due to the differences among the reference datasets. This is particularly true for surface downwelling shortwave radiation, which has a significant impact in terms of simulated maize yields. Projections of future yields over West Africa are quite different, depending on the bias-correction method used. However all these projections show a similar relative decreasing trend over the 21st century.

scholarly journals Numerical modelling of sediment transport in the Adriatic Sea

2014 ◽  
Vol 11 (3) ◽  
pp. 1391-1433 ◽  
Author(s):  
A. Guarnieri ◽  
A. J. Souza ◽  
N. Pinardi ◽  
P. Traykovski
Keyword(s):  
Sediment Transport ◽  
Adriatic Sea ◽  
Transport Model ◽  
Data Availability ◽  
Western Coast ◽  
Po River ◽  
Northern Adriatic ◽  
Coastal Belt ◽  
Italian Coasts ◽  
The Impact

Abstract. A new sediment transport model, considering currents, tides and waves is presented for the Adriatic Sea basin. The simulations concentrate on the winter of 2002–2003 because of field data availability and interesting intermittent processes occurrence. A process oriented analysis is performed to investigate the impact that Sirocco and Bora wind regimes have on sediment transport. The comparisons of the simulations with the observed data show that the model is capable to capture the main dynamics of sediment transport along the Italian coasts and the sediment concentration within the water column. This latter can reach values up to several g L−1, especially within the first centimetres above the bottom. The sediments are transported mainly southwards along the Italian coasts, consistently with the known literature results, except during Sirocco wind events, which can be responsible for reversing the coastal circulation in the northern area of the basin, and consequently the sediment transport. The resuspension of sediments is also related to the specific wave regimes induced by Bora and Sirocco, the former inducing resuspension events near the coasts while the latter causing a more diffused resuspension regime in the Northern Adriatic basin. Beside the realistic representation of short timescales resuspension/deposition events due to storms, the model was also used to investigate persistent erosion or deposition areas in the Adriatic Sea. Two main depocenters were identified: one, very pronounced, in the surroundings of the Po river delta, and another one a few kilometres off the coast in front of the Ancona promontory. A third region of accumulation, even if less intense, was found to be offshore the southernmost limit of the Gargano region. On the contrary the whole western coast within a distance of a few kilometres from the shore was found to be subject to prevailing erosion. The comparison with observed accumulation and erosion data shows that the model captures well the main depocenters in the domain and the erosion within the very coastal belt of the western side of the basin, but seems to be too erosive in a few areas, in particular those where the contribution of sediment inflow to the sea of some minor but intermittently important rivers is not considered in a realistic way as input to the model.

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