407 research outputs found
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A comparison of three canopy interception models for a leafless mixed deciduous forest stand in the eastern United States
Canopy interception of incident precipitation is a critical component of the forest water balance during each of the four seasons. Models have been developed to predict precipitation interception from standard meteorological variables because of acknowledged difficulty in extrapolating direct measurements of interception loss from forest to forest. No known study has compared and validated canopy interception models for a leafless deciduous forest stand in the eastern United States. Interception measurements from an experimental plot in a leafless deciduous forest in northeastern Maryland (39°42'N, 75°5'W) for 11 rainstorms in winter and early spring 2004/05 were compared to predictions from three models. The Mulder model maintains a moist canopy between storms. The Gash model requires few input variables and is formulated for a sparse canopy. The WiMo model optimizes the canopy storage capacity for the maximum wind speed during each storm. All models showed marked underestimates and overestimates for individual storms when the measured ratio of interception to gross precipitation was far more or less, respectively, than the specified fraction of canopy cover. The models predicted the percentage of total gross precipitation (PG) intercepted to within the probable standard error (8.1%) of the measured value: the Mulder model overestimated the measured value by 0.1% of PG; the WiMo model underestimated by 0.6% of PG; and the Gash model underestimated by 1.1% of PG. The WiMo modelâs advantage over the Gash model indicates that the canopy storage capacity increases logarithmically with the maximum wind speed. This study has demonstrated that dormant-season precipitation interception in a leafless deciduous forest may be satisfactorily predicted by existing canopy interception models
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Rainfall in Queensland: Part 4: the ability of HiGEM to simulate Queensland's rainfall variability and its drivers
Stakeholders and policymakers are seeking detailed information on the impacts of climate change and variability, especially on rainfall, at the local and regional levels. This information can be delivered by only those global climate models that represent the atmosphere and ocean at fine resolution, to robustly simulate the weather systems that produce rainfall. These models provide us with a better understanding of the key meteorological phenomena that affect Queensland. That knowledge can then be used to improve the simulation of these phenomena in lowerresolution
climate models. Implementing these improvements will provide more accurate predictions on weekly to seasonal and decadal timescales, as well as more robust predictions of the impacts of climate change on these phenomena.
High-resolution Global Environment Model, version 1.1 (HiGEM) is a global, coupled climate model that was developed by the U.K. academic community. It is based on the U.K. Hadley Centre's HadGEM1 model, but HiGEM has considerably higher resolution: 90 km in the atmosphere and 30 km in the ocean. HiGEM has been used in this research as its increased resolution may allow the model to better represent regional climate variability and change in Queensland.
In this research, a 150 year control simulation of HiGEM was assessed to evalute the ability of the model to simulate Queensland's rainfall and its inter-annual and decadal variability. HiGEM was also assessed for its ability to produce the observed Empirical Orthogonal Teleconnection (EOT) patterns of rainfall avariability obtained from the SILO gridded rainfall dataset.
In the mean, HiGEM produces less rainfall over Queensland than observed, particularly in the north of the state. Most of this dry bias occurs because the model simulates a weaker Australian summer monsoon than is observed. However, HiGEM represents well the relationship between the El Niño Southern Oscillation (ENSO) and Queensland rainfall, on annual and seasonal timescales. The model even captured the observed asymmetric correlation between the ENSO and Queensland rainfall: stronger La Niña events cause stronger flood years in Queensland, but stronger El Niño events do not cause stronger droughts.
The research found that HiGEM lacks the ability to model decadal variations in Queensland rainfall and in the teleconnection between the ENSO and rainfall. This is likely due to the model's inability to simulate the Interdecadal Pacific Oscillation (IPO), which has been identified as the key driver of these variations.
In relation to the generation of tropical cyclones, HiGEM captures the observed regions of tropical-cyclone formation and the correct distributions of tropical cyclone tracks, but simulates too many tropical cyclones in the Southwest Pacific.
When EOT analysis is applied to HiGEM and the results are compared with the EOT patterns computed using observed rainfall, HiGEM performs well for those EOTs related to the ENSO in summer, winter and spring. HiGEM also represents the relationship between Southeast Queensland rainfall and onshore easterly winds, including the decadal variations in the winds' strength and moisture content. Futher, HiGEM correctly simulates the observed association between the frequency of tropical cyclones and summer rainfall in Cape York.
The success of HiGEM at reproducing many of the observed EOTs, particularly in summer, increases our confidence in the model's ability to predict the impact of climate change on Queensland's rainfall and its drivers
Breastfeeding after a caesarean section: Mother-infant health trade-offs
This thesis demonstrates the value of an anthropological perspective on informing appropriate breastfeeding support after caesarean section delivery. In contrast to epidemiological research that identifies distinct aspects of mother-infant interactions altered by this birth mode, my research explored the interrelated obstacles to breastfeeding from the mothersâ perspectives as the experiences were unfolding. I apply Triversâs (1974) parent-offspring conflict model to conceptualise breastfeeding and predict realisation of infant feeding based on the interaction of maternal cost and infant benefit. The work adds the previously unstudied population of caesarean section-delivered breastfeeding dyads to the human life-history theory line of investigation.
Postnatal ward and telephone semi-structured interview data were collected in Newcastle, England during 2006-09 with two groups of women. Phase 1 comprised participants who underwent either an unscheduled or scheduled caesarean section delivery (n = 75). Phase 2 involved women who experienced scheduled, non-labour caesarean section delivery and were randomly allocated an intervention or control cot for the entirety of their postnatal ward stay (n = 51). The impact of the infant side-car crib or standalone cot on breastfeeding was tested among the Phase 2 mothers by comparison of 35 overnight postnatal ward video recordings.
The various aspects of womenâs delivery and infant care were prioritised based on their knowledge of known risks and benefits. Intentions were carried out within the context of the support and opportunities available. Contrary to popular belief, the decision to undergo a caesarean section and deviation from prenatal breastfeeding intentions were undertaken because they seemed like the best or only option in the circumstances. Many women felt frustrated because of their postnatal limitations with caretaking for infants who were described as unexpectedly doing poorly. The absence of labour before the caesarean section was perceived to be beneficial by the mothers due to the intense pain of contractions and the undo âstressâ vaginal parturition posed for the infant. However, the participants were surprised by being told by midwives after the delivery that (sub-clinically) poor infant condition was a common consequence of caesarean section. Some breastfeeding difficulty stemmed from âmucousâ expulsion that had to occur before the babies could be âinterestedâ in feeding.
The peak mother-infant breastfeeding conflict was night-time after visiting hours. Midwifery and maternal concerns over the mothersâ lack of sleep prompted formula supplementation. As predicted, the side-car crib was associated with reduction of the maternal cost of breastfeeding. However, participants in the intervention group were not observed breastfeeding significantly more frequently than the control group as expected. The cost-benefit breastfeeding model suggests that high maternal cost and/or low perceived infant benefit was experienced to such a degree that mothers breastfed minimally despite the âhuge differenceâ in infant access afforded by the side-car crib compared to the standalone cot. Regardless, data support the side-car crib as the better arrangement for mother-infant dyads who underwent a non-labour caesarean section due to the less potential infant risk observed and the benefit to maternal recovery.
The utility of the parent-offspring conflict framework for predicting breastfeeding outcomes was supported by the association of reported reasons for breastfeeding intent and of bedsharing with breastfeeding frequency and duration. The thesis suggests that more detailed physiological information may enable families to better understand public health advice for exclusive breastfeeding and low caesarean section delivery rates. Breastfeeding after a caesarean section is affected by interrelated and compounding difficulties, so my single alteration in the postnatal environment did not resolve the impediments. An evolutionary perspective can assist in identifying populations at risk for suboptimal health outcomes and designing support to ameliorate mismatches between coevolved processes and routinely encountered conditions
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Rainfall in Queensland: Part 5: projected changes in Queensland rainfall under double-CO2 conditions in the HiGEM model
This report analyses projected changes in Queensland rainfall from the HiGEM global climate model under atmospheric carbon dioxide (CO2) concentrations of approximately 690 parts per million (ppm), equivalent to the CO2 concentration in the late 21st century under a moderate (IPCC SRES (2012) A1B) emissions scenario.
HiGEM is a high-resolution version of the U.K. Met Office model (HadGEM1). Previously reported research found that with present-day CO2, HiGEM accurately simulated many observed climate drivers of Queensland rainfall, including the El Niño Southern Oscillation; this increases our confidence in the modelâs projections of rainfall change.
The HiGEM model projects that average surface temperatures in Queensland will warm by approximately 2°C under doubled CO2, with the strongest warming in autumn and winter. Consistent with many other studies, the land warms by more than the ocean, leading to greater warming inland in Queensland and less along the coast.
While HiGEM projects small changes to annual-total rainfall, the NovemberâApril wet season becomes compressed: 10â20 per cent more rain falls during January and February, with 10â40 per cent less in November, March and April. The Queensland wet season begins up to 10 days laterâparticularly along the coastâand ends up to 20 days earlierâparticularly in the southwest. Precipitation falls in fewer but much more intense events.
The HiGEM model projects that Queensland will rely more strongly upon heavy mid-summer rains for its annual precipitation. This has important consequences for agriculture and for water storage. The frequency of extreme rain days (greater than 100 millimetre accumulation) in HiGEM increases by up to 40 per cent, particularly in summer during the intensified monsoon. HiGEM also projects that the average duration of extreme rainfall will rise (by 20 per cent) as will the area covered by each event (15 per cent). The number of light rain days (1â5 millimetre) is projected to decrease by 5â10 per cent. Tropical cyclones become slightly less frequent near Queensland.
The HiGEM model projects that many climate drivers of rainfall will remain robust in a warmer world. The correlation with ENSO declines, but there are an inadequate number of ENSO events in the future-climate simulation on which to base firm conclusions. Rainfall variations in southwest and southeast Queensland become less connected to those in the rest of the state, mostly due to an earlier end of the wet season in those regions
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El Niño 2015/2016 impact analysis, monthly outlook December 2015
During the summer and autumn 2015, El Niño conditions in the east and central Pacific have strengthened, disrupting weather patterns throughout the tropics and into the mid-latitudes. For example, rainfall during this summerâs Indian monsoon was approximately 15% below normal. The continued strong El Niño conditions have the potential to trigger damaging impacts (e.g. droughts, famines, floods), particularly in less-developed tropical countries, which would require a swift and effective humanitarian response to mitigate damage to life and property (e.g. health, migration, infrastructure). This analysis uses key climatic variables (temperature, soil moisture and precipitation) as measures to monitor the ongoing risk of these potentially damaging impacts.
The previous 2015-2016 El Niño Impact Analysis was based on observations over the past 35 years and produced Impact Tables showing the likelihood and severity of the impacts on temperature and rainfall by season. The current report is an extension of this work providing information from observations and seasonal forecast models to give a more detailed outlook of the potential near-term impacts of the current El Niño conditions by region.
This information has been added to the Impact Tables in the form of an âObservations and Outlookâ row. This consists of observational information for the past seasons of JJA 2015 and SON 2015, a detailed monthly outlook from 5 modeling centres for Dec 2015 and then longer-term seasonal forecast information from 2 modeling centres for the future seasons of JF 2016 and MAM 2016. The seasonal outlook information is an indication of the average likely conditions for that coming month (or season) and region and is not a definite prediction of weather impacts
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Diagnosing ocean feedbacks to the BSISO: SST-modulated surface fluxes and the moist static energy budget
The oceanic feedback to the atmospheric boreal summer intraseasonal oscillation (BSISO) is examined by diagnosing the sea surface temperature (SST) modification of surface fluxes and the moist static energy (MSE) on intraseasonal scales. SST variability affects intraseasonal surface latent heat (LH) and sensible heat (SH) fluxes, through its influence on air-sea moisture and temperature gradients (delta-q and delta-T). According to bulk formula decomposition, LH is mainly determined by wind-driven flux perturbations, while SH is more sensitive to thermodynamic flux perturbations. SST fluctuations tend to increase the thermodynamic flux perturbations over active BSISO regions, but this is largely offset by the wind-driven flux perturbations. Enhanced surface fluxes induced by intraseasonal SST anomalies are located ahead (north) of the convective center over both the Indian Ocean and western Pacific, favoring BSISO northward propagation. Analysis of budgets of column-integrated MSE () and its time rate of change (d/dt) show that SST-modulated surface fluxes can influence the development and propagation of the BSISO, respectively. LH and SH variability induced by intraseasonal SSTs maintain 1-2% of /day over the equatorial western Indian Ocean, Arabian Sea and Bay of Bengal, but damp about 1% of /day over the western North Pacific. The contribution of intraseasonal SST variability to d/dt can reach 12-20% over active BSISO regions. These results suggest that SST variability is conducive, but perhaps not essential, for the propagation of convection during the BSISO life cycle
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