The wet‐dry tropics of Central America are characterized by long dry seasons, during which communities often struggle for water. High interannual rainfall variability, driven in parts by the El Niño ...Southern Oscillation (ENSO), increases these challenges. Further, climate change projections indicate that the region will likely become drier. However, research on impacts on water resources at the watershed scale is limited in the region—yet this information is essential for water managers. Therefore, in this research, we quantified the potential impacts of ENSO and four different climate change scenarios on water resources in two watersheds in the wet‐dry tropics of Guanacaste, Costa Rica, using a hydrological model (Water Evaluation and Planning Tool WEAP). Given that the watersheds are human used, we also explored different water demand scenarios. Modeling results indicated that an extreme El Niño can reduce groundwater recharge and streamflow by ∼60% relative to ENSO neutral. For 2075–2100, modeling results indicated that while potential evapotranspiration increases, actual evapotranspiration decreases due to limited water availability. Further, climate change may lead to reductions of mean annual streamflow and groundwater recharge by 40%–45% and 26%–28%, respectively, in comparison to the historical baseline. Importantly, high population growth could further hasten potentially irreversible groundwater storage declines. On the other hand, reduction of per‐capita water demand could slow down, or even reverse, the decline of groundwater storage.
Plain Language Summary
In the wet‐dry tropics of Costa Rica, communities often struggle for water during the long dry season. Climate variability is high in the region, and in some years, rainfall is reduced, mostly due to El Niño (an ocean‐atmosphere circulation). With climate change, it might become drier in the future. In this research, we assessed the potential impacts of El Niño and four future climate change scenarios on surface water and groundwater supplies and found that during an extreme El Niño, streamflow and groundwater recharge are ∼60% reduced. Climate change at the end of the 21st century may lead to reductions of mean annual streamflow and groundwater recharge by 40%–45% and 26%–28%, respectively, in comparison to the historical baseline. We also considered increasing domestic water demand and found that a growing population with increasing water demands can lead to potentially irreversible groundwater supply decline. On the other hand, reduction of domestic water demand due to effective water management can potentially slow down, or even reverse, such a decline of groundwater supplies.
Key Points
Watershed‐based analysis of climate change and water demand impacts on streamflow and groundwater in wet‐dry tropics of Central America
El Niño and climate change may substantially impact streamflow and groundwater recharge, especially with high population growth
Reductions in domestic water demand may be able to slow down, or reverse, groundwater storage declines
Rainfall in Guanacaste, Costa Rica, has marked wet/dry phases: the rainy season is punctuated by a short midsummer drought, and the dry season frequently has months of no rain. In this region, spring ...and summer rainfall peaks are important for local rain-fed agriculture and annual total for groundwater recharge and hydroelectricity production. We propose a novel model of rainfall in this region, the double-Gaussian model, which uses monthly total rainfall data collected from 1980 to 2020 from two meteorological observation stations. Our model provides an intuitive way of describing the seasonality of rainfall, the inter-annual variability of the cycle, and variability due to the monthly Oceanic Niño Index, ONI. We also consider two alternative models, a regression model with ARMA errors and a Tweedie model, as a means of assessing the robustness of our conclusions to violations of the assumptions of the double-Gaussian model. We found that the data provide strong evidence of an increase/decrease in rainfall in both temporal maxima during La Niña/El Niño (negative/positive ONI) conditions but no evidence of a decade-scale trend after accounting for ONI effects. Finally, we investigated the problem of forecasting future rainfall based on our three models. We found that when ONI is incorporated as a predictor variable, our models can produce substantial gains in prediction accuracy of spring, summer, and annual totals over naive methods based on monthly sample means or medians.
As part of efforts to understand the sources of air pollution in Cape Town, this study investigates the local variation of tropospheric ozone (O3) and identifies possible advection paths of O3 ...pollution from a remote source to Cape Town. Measurements of O3 and wind from three sites in the Cape Town area were analyzed to study the local variations of O3. At each site, the diurnal variation of O3 is found to be mainly driven by photochemical production while the seasonal variation of O3 is mostly driven by wind conditions. The highest concentration of O3 is observed at the remote site (Cape Point) while lowest O3 concentration is observed at the sub-urban site (Goodwood), where there are chemical sinks of O3 such as NOx. Atmospheric pollution over southern Africa was simulated to study the regional transport of O3. The simulations show that extreme O3 levels in Cape Town can be caused by air pollution transported from the industrial Highveld of South Africa, in the lower troposphere. Such extreme O3 pollution events over Cape Town are simulated to occur in January (14%), March (44%), April (28%) and September (14%). Lagrangian trajectories suggest four paths by which air parcels can be transported from the industrial Highveld to Cape Town: a north-easterly path which is the most frequent route, a tropical deviation route, a deviation along the south coastline and an oceanic deviation path which is the less frequent route. The major advection paths associated with poor air quality in Cape Town are the north-easterly route and the path along the south coastline of the country. Hence the study suggests that emissions in the industrial Highveld may contribute to O3 concentration in the Cape Town area.
•We investigate the local variation and transport of O3 pollution over Cape Town.•The concentration of O3 is higher at Cape Point than at two sites near the city.•Emissions from the industrial Highveld contribute to O3 pollution in Cape Town.•Pollutants from the Highveld are transported to Cape Town via four major pathways.•The pollutant transports mostly occur in March and September.
This seminal work documents the clandestine sea borne operations undertaken by South Africa's 4 Reconnaissance Commando Regiment. It breathtakingly reveals the versatility and effectiveness of this ...elite unit which worked with a range of other South African and Rhodesian forces, including the Rhodesian SAS, to engage in a range of raiding and war fighting activities. These operations saw the clandestine reconnaissance of harbors, the sinking of enemy shipping and the destruction of shore installations in Angola and Mozambique. Just some of the tasks undertaken by this extraordinary maritime capability which totaled no more than 45 operators, both black and white!With unparalleled access to previously secret material, the authors, both of whom worked to develop 4 Recce's operating capabilities, trace the origins of the Regiment back to the 1970's when the South African's determined the need for a maritime force projection capability. They relate how maritime doctrine was developed within South Africa's wider Special Forces capability and how joint operational approaches were configured with the South African Navy. This saw the development of a range of swimmer, reconnaissance, diving and boat operator training courses, along with the design of specialist raiding craft and amphibious assault platforms, which were originated to operate from the Navy's existing shipping and submarines. All of which demonstrated the immense potential of this newly emergent force and the resourcefulness of its individual operators. Required to successfully complete a grueling selection process, the operators of 4 Recce were relentlessly tested to prove their physical and mental mettle, not to mention their leadership skills and initiative. Steyn and Soderlund's chronological analysis of the operations undertaken by 4 Recce and the South African Navy is stunning to behold. They impartially detail the secret and specialized actions which saw both success and failure. From Cabinda on the West Coast to Tanzania on the East, 4 Recce, and whose existence and capability was largely kept secret even within the South African Defence Force, conducted numerous clandestine raids. They attacked shipping and strategic targets such as oil facilities, transport infrastructure and even ANC offices. And sometimes the raids did go wrong, spectacularly so in one instance when two operators were killed and Captain Wynand Du Toit was captured. He was later paraded in front of the world's media, much to the embarrassment of the South African government. This is a fascinating work and one that will enthrall anyone with an interest in Special Forces operations. Profusely illustrated with many previously unpublished photographs, it stands as a testament to the author's endeavors as, respectively, the former Operations Commander of 4 Recce and the former Commander Task Group of the SA Navy - as well as the incredible operators of 4 Recce. Explosive and compulsive, Iron Fist from the Sea takes you right to the raging surf; to the adrenaline and fear that is sea borne raiding...
Numerical model simulations of sea-breeze circulations under idealized conditions are subjected to dimensional analyses in order to resolve sea-breeze dynamical relations and unify previous results ...based on observations. The analysis is motivated by the fact that sea-breeze depth scaling and volume flux scaling are only partially understood. The analysis is based on nonlinear numerical modelling simulations in combination with recent observational scaling analyses. The analysis confirms scaling laws for sea-breeze strength dependence on governing variables and shows how the sea-breeze speed scale is controlled by surface heat flux. It also shows that the sea-breeze depth scale is controlled by stability. By combining sea-breeze speed and depth scales, the sea-breeze volume flux scale is determined by an equilibrium between the accumulated convergence of heat over land since sunrise and stable air advection from the sea surface.PUBLICATION ABSTRACT
Numerical model simulations of sea-breeze circulations in the presence of idealized topography are subjected to dimensional analysis in order to capture the dynamics of the sea-breeze circulation ...combined with an upslope-flow circulation. A secondary objective is to reconcile previous results based on observations. The analysis is based on a scaling analysis of sea-breeze speed, depth and volume flux. This study is motivated by the fact that the literature of sea breezes interacting with upslope flows is generally qualitative. Results show clear scaling regimes and strong interaction between the two thermally driven circulations. We distinguish three regimes, depending on slope length, slope angle, stability and surface heat flux. The first and third regimes obey the scaling laws of pure sea-breeze scaling. The second regime shows a significant decrease in the scaled volume flux relative to pure sea-breeze scaling. Dynamical relations in the second regime show a strong influence on the circulation of upslope stable air advection.
High-resolution Doppler lidar observations obtained during the Mesoscale Alpine Program (MAP) 1999 field campaign are used to investigate the along-valley structure of daytime valley flows in the ...Wipp Valley, Austria. The observations show that under varying ambient conditions the valley flow increases in speed through a narrow section of the valley. Furthermore, the along-valley volume flux diverges along the valley segment under investigation, which suggests that the observed along-valley acceleration of the valley flow cannot be explained by the horizontal constriction of the valley sidewalls. It is hypothesized that the along-valley acceleration of the flow is caused by an intravalley change in the horizontal pressure gradient induced by differential heating rates of the valley atmosphere.
Assuming current emissions and background concentrations, we investigate how changes in synoptic meteorology alone affect ozone episodes in the Lower Fraser Valley, Canada, in future climates. We ...perform synoptic typing of combined sea level pressure and 500 hPa geopotential heights for June to September 1961-2000 using the National Centers for Environmental Prediction (NCEP) reanalysis data. Five clusters provide a qualitatively good representation of typical synoptic conditions and stratify exceedance days into one cluster with more than half of all exceedances. Independent cluster analyses for climate model output from the Third Generation Coupled Global Climate Model (CGCM3.1 T63) 1961-2000 control runs and 2046-65 Special Report on Emissions Scenarios (SRES) A1B scenario runs give clusters qualitatively similar to those using NCEP data. When CGCM output is mapped to the NCEP clusters, the CGCM control run cluster frequencies are almost identical to NCEP frequencies, while CGCM 2046-65 output shows only small frequency changes. This indicates that, in future climates, the frequency of occurrence of synoptic types conducive to ozone exceedances will not be appreciably different than they are in the present climate. However, the CGCM predicts substantial increases in daily maximum temperatures in the Lower Fraser Valley across all five clusters. An analysis of exceedance probabilities suggests that the predicted temperature increase will more than double the number of exceedance days per year.
R
ésumé
Traduit par la rédaction Sur la base des niveaux d'émission et des concentrations de fond actuels, nous étudions comment les seuls changements dans la météorologie synoptique influencent les épisodes d'ozone dans la vallée du bas Fraser, au Canada, dans les climats futurs. Nous effectuons un typage synoptique de la pression au niveau de la mer combinée aux hauteurs géopotentielles de 500 hPa pour juin à septembre 1961-2000 en utilisant les données de réanalyse des NCEP (National Centers for Environmental Prediction). Cinq grappes fournissent une représentation qualitativement bonne des conditions synoptiques typiques et stratifient les jours de dépassement dans une grappe avec plus de la moitié de tous les dépassements. Des analyses de grappes indépendantes pour la sortie du modèle climatique faites à partir des passes de vérification du CGCM3.1 T63 (Third Generation Coupled Global Climate Model) pour la période 1961-2000 et des passes de scénario du SRES (Special Report on Emissions Scenarios) A1B pour 2046-2065 donnent des grappes qualitativement semblables à celles obtenues avec les données des NCEP. Quand la sortie du CGCM est mise en correspondance avec les grappes des NCEP, les fréquences des grappes des passes de vérification sont presque identiques aux fréquences des NCEP, et en même temps la sortie du CGCM 2046-2065 ne montre que de petits changements de fréquence. Cela indique que, dans les climats futurs, la fréquence d'apparition des types synoptiques menant à des dépassements d'ozone ne diffèrera pas notablement de ce qu'elle est dans le climat présent. Cependant, le CGCM prévoit des augmentations appréciables dans les températures maximales journalières dans la vallée du bas Fraser dans les cinq grappes. Une analyse des probabilités de dépassement suggère que l'augmentation de température prévue fera plus que doubler le nombre de jours de dépassement par année.
A novel pattern-based model evaluation technique is proposed and demonstrated for air quality models (AQMs) driven by meteorological model (MM) output. The evaluation technique is applied directly to ...the MM output; however, it is ultimately used to gauge the performance of the driven AQM. This evaluation of AQM performance based on MM performance is a major advance over traditional evaluation methods. First, meteorological cluster analysis is used to assign the days of a historical measurement period among a small number of weather patterns having distinct air quality characteristics. The clustering algorithm groups days sharing similar empirical orthogonal function (EOF) representations of their measurements. In this study, EOF analysis is used to extract space–time patterns in the surface wind field reflecting both synoptic and mesoscale influences. Second, simulated wind fields are classified among the determined weather patterns using the measurement-derived EOFs. For a given period, the level of agreement between the observation-based clustering labels and the simulation-based classification labels is used to assess the validity of the simulation results. Mismatches occurring between the two sets of labels for a given period imply inaccurately simulated conditions. Moreover, the specific nature of a mismatch can help to diagnose the downstream effects of improperly simulated meteorological fields on AQM performance. This pattern-based model evaluation technique was applied to extended simulations of fine particulate matter (PM2.5) covering two winter seasons for the San Francisco Bay Area of California.
Background and Objectives:
Triptorelin 6-month formulation was developed to offer greater convenience to both patients and physicians by reducing the injection frequency. The efficacy, ...pharmacokinetics and safety of a new 6-month formulation of triptorelin were investigated over 12 months (48 weeks). The primary objective was to evaluate the formulation in achieving castrate serum testosterone levels (≤1.735 nmol/L or ≤50 ng/dL) on day 29 and in maintaining castration at months 2–12. Absence of luteinizing hormone (LH) stimulation and change in prostate-specific antigen (PSA) level were also assessed.
Methods:
An open-label, non-comparative, phase III study in 120 patients with advanced prostate cancer was conducted from July 2006 to August 2007 in private and public institutions in South Africa. Each patient received two consecutive intramuscular injections of triptorelin embonate (pamoate) 22.5 mg at an interval of 24 weeks. In all patients, testosterone (primary outcome measurement) was measured at baseline and then every 4 weeks; LH was measured before and 2 hours after the two injections. PSA was measured on day 1 and at weeks 12, 24, 36 and 48. Adverse events were recorded at each visit.
Results:
In the intent-to-treat population, 97.5% (95% CI 92.9, 99.5) of patients achieved castrate serum testosterone levels by day 29, and 93.0% (95% CI 86.8, 97.0) maintained castration at months 2–12. After the second injection, 98.3% of patients showed absence of LH stimulation. The most frequent drug-related adverse events were hot flushes (71.7% of patients). No patient withdrew from the study as a result of an adverse event.
Conclusions:
The triptorelin 6-month formulation was well tolerated and was able to achieve and maintain castration for the treatment of locally advanced and metastatic prostate cancer. By reducing the frequency of required injections, this new formulation offers a more convenient treatment regimen. (Clinical Trial Registration, NCT00751790 at
www.clinicaltrials.gov
)
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