Home About us Contact
|
Home About us Contact | ||
|
|
||
Prior Estimates (prior + estimate)
Selected AbstractsThe effect of wealth and real income on wildlife consumption among native Amazonians in Bolivia: estimates of annual trends with longitudinal household data (2002,2006)ANIMAL CONSERVATION, Issue 3 2010R. Godoy Abstract Over the last decades, native Amazonians have put increasing pressure on animal wildlife owing to growth in demand. Across societies, household monetary income and wealth shape food consumption; hence, so it is natural to ask what effect might these variables have on the demand for wildlife consumption among native Amazonians, particularly as they gain a stronger foothold in the market economy and increasing de jure stewardship over their territories. Prior estimates of the effects of household monetary income and household wealth on wildlife consumption among native Amazonians have relied on cross-sectional data and produced unclear results. The goal of this research was to improve the precision of previous estimates by drawing on a larger sample and on longitudinal data. The analysis draws on a dataset composed of five consecutive annual surveys (2002,2006, inclusive) from 324 households in a native Amazonian society of foragers and farmers in Bolivia (Tsimane'). Multiple regression analysis is used to estimate the association between wildlife consumption and monetary income and wealth. Wildlife consumption bore a positive association with the level of household wealth and no significant association with household monetary income. Among Tsimane', the main internal threat to wildlife conservation in the short run will likely arise from increases in wealth, probably from the enhanced capacity that selected physical assets (e.g. guns) have in the capture of animal wildlife. [source] Simultaneous state estimation and attenuation correction for thunderstorms with radar data using an ensemble Kalman filter: tests with simulated dataTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 643 2009Ming Xue Abstract A new approach to dealing with attenuated radar reflectivity data in the data assimilation process is proposed and tested with simulated data using the ensemble square-root Kalman filter. This approach differs from the traditional method where attenuation is corrected in observation space first before observations are assimilated into numerical models. We build attenuation correction into the data assimilation system by calculating the expected attenuation within the forward observation operators using the estimated atmospheric state. Such a procedure does not require prior assumption about the types of hydrometeor species along the radar beams, and allows us to take advantage of knowledge about the hydrometeors obtained through data assimilation and state estimation. Being based on optimal estimation theory, error and uncertainty information on the observations and prior estimate can be effectively utilized, and additional observed parameters, such as those from polarimetric radar, can potentially be incorporated into the system. Tests with simulated reflectivity data of an X-band 3 cm wavelength radar for a supercell storm show that the attenuation correction procedure is very effective,the analyses obtained using attenuated data are almost as good as those obtained using unattenuated data. The procedure is also robust in the presence of moderate dropsize-distribution-related observation operator error and when systematic radar calibration error exists. The analysis errors are very large if no attenuation correction is applied. The effect of attenuation and its correction when radial velocity data are also assimilated is discussed as well. In general, attenuation correction is equally important when quality radial velocity data are also assimilated. Copyright © 2009 Royal Meteorological Society [source] On the equivalence between Kalman smoothing and weak-constraint four-dimensional variational data assimilationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 613 2005M. Fisher Abstract The fixed-interval Kalman smoother produces optimal estimates of the state of a system over a time interval, given observations over the interval, together with a prior estimate of the state and its error covariance at the beginning of the interval. At the end of the interval, the Kalman smoother estimate is identical to that produced by a Kalman filter, given the same observations and the same initial state and covariance matrix. For an imperfect model, the model error term in the covariance evolution equation acts to reduce the dependence of the estimate on observations and prior states that are well separated in time. In particular, if the assimilation interval is sufficiently long, the estimate at the end of the interval is effectively independent of the state and covariance matrix specified at the beginning of the interval. In this case, the Kalman smoother provides estimates at the end of the interval that are identical to those of a Kalman filter that has been running indefinitely. For a linear model, weak-constraint four-dimensional variational data assimilation (4D-Var) is equivalent to a fixed-interval Kalman smoother. It follows that, if the assimilation interval is made sufficiently long, the 4D-Var analysis at the end of the assimilation interval will be identical to that produced by a Kalman filter that has been running indefinitely. The equivalence between weak-constraint 4D-Var and a long-running Kalman filter is demonstrated for a simple analogue of the numerical weather-prediction (NWP) problem. For this nonlinear system, 4D-Var analysis with a 10-day assimilation window produces analyses of the same quality as those of an extended Kalman filter. It is demonstrated that the current ECMWF operational 4D-Var system retains a memory of earlier observations and prior states over a period of between four and ten days, suggesting that weak-constraint 4D-Var with an analysis interval in the range of four to ten days may provide a viable algorithm with which to implement an unapproximated Kalman filter. Whereas assimilation intervals of this length are unlikely to be computationally feasible for operational NWP in the near future, the ability to run an unapproximated Kalman filter should prove invaluable for assessing the performance of cheaper, but suboptimal, alternatives. Copyright © 2005 Royal Meteorological Society [source] Ambient temperature and risk of death from accidental drug overdose in New York City, 1990,2006ADDICTION, Issue 6 2010Amy S. B. Bohnert ABSTRACT Background Mortality increases as ambient temperature increases. Because cocaine affects core body temperature, ambient temperature may play a role in cocaine-related mortality in particular. The present study examined the association between ambient temperature and fatal overdoses over time in New York City. Methods Mortality data were obtained from the Office of the Chief Medical Examiner for 1990 to 2006, and temperature data from the National Oceanic and Atmospheric Association. We used generalized additive models to test the relationship between weekly average temperatures and counts of accidental overdose deaths in New York City, controlling for year and average length of daylight hours. Results We found a significant relation between ambient temperature and accidental overdose fatality for all models where the overdoses were due in whole or in part to cocaine (all P < 0.05), but not for non-cocaine overdoses. Risk of accidental overdose deaths increased for weeks when the average temperature was above 24°Celsius. Conclusions These results suggest a strong relation between temperature and accidental overdose mortality that is driven by cocaine-related overdoses rising at temperatures above 24°Celsius; this is a substantially lower temperature than prior estimates. To put this into perspective, approximately 7 weeks a year between 1990 and 2006 had an average weekly temperature of 24 or above in New York City. Heat-related mortality presents a considerable public health concern, and cocaine users constitute a high-risk group. [source] A large carbon pool and small sink in boreal Holocene lake sedimentsGLOBAL CHANGE BIOLOGY, Issue 10 2004Pirkko Kortelainen Abstract Model-based estimates suggest that lake sediments may be a significant, long-term sink for organic carbon (C) at regional to global scales. These models have used various approaches to predict sediment storage at broad scales from very limited data sets. Here, we report a large-scale direct assessment of the standing stock and sedimentation rate of C for a representative set of lakes in Finland. The 122 lakes were selected from the statistically selected Nordic Lake Survey database, they cover the entire country and the water quality represents the average lake water quality in Finland. Unlike all prior estimates, these data use sediment cores that comprise the entire sediment record. The data show that within Finland, aquatic ecosystems contain the second largest areal C stocks (19 kg C m,2) after peatlands (72 kg C m,2), and exceed by significant amounts stocks in the forest soil (uppermost 75cm; 7.2 kg C m,2) and woody biomass (3.4 kg C m,2). Kauppi et al. (1997). The Finnish estimate extrapolated over the boreal region gives a total C pool in lakes 19,27 Pg C, significantly lower than the previous model-based estimates. [source] Modification of upwind finite difference fractional step methods by the transient state of the semiconductor deviceNUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 2 2008Yirang Yuan Abstract The mathematical model of the three-dimensional semiconductor devices of heat conduction is described by a system of four quasi-linear partial differential equations for initial boundary value problem. One equation of elliptic form is for the electric potential; two equations of convection-dominated diffusion type are for the electron and hole concentration; and one heat conduction equation is for temperature. Upwind finite difference fractional step methods are put forward. Some techniques, such as calculus of variations, energy method multiplicative commutation rule of difference operators, decomposition of high order difference operators, and the theory of prior estimates and techniques are adopted. Optimal order estimates in L2 norm are derived to determine the error in the approximate solution.© 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2008 [source] The upwind finite difference fractional steps methods for two-phase compressible flow in porous mediaNUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 1 2003Yirang Yuan Abstract The upwind finite difference fractional steps methods are put forward for the two-phase compressible displacement problem. Some techniques, such as calculus of variations, multiplicative commutation rule of difference operators, decomposition of high-order difference operators, and prior estimates, are adopted. Optimal order estimates in L2 norm are derived to determine the error in the approximate solution. This method has already been applied to the numerical simulation of seawater intrusion and migration-accumulation of oil resources. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 67,88, 2003 [source] Survival rates for a declining population of bottlenose dolphins in Doubtful Sound, New Zealand: an information theoretic approach to assessing the role of human impactsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009Rohan J. C. Currey Abstract 1.The bottlenose dolphins of Doubtful Sound, New Zealand are a declining population at the southern limit of the species' range, exposed to impacts from tourism and habitat modification. Patterns in apparent annual survival were analysed from photographic resightings of naturally marked adults (1990 to 2008) and calves within the first year of life (1994 to 2008) using capture-recapture models. 2.The most parsimonious model for adults provided a time-invariant, sex-invariant estimate of survival (,a(1990,2008)=0.9374; 95% CI: 0.9170,0.9530), marginally lower than prior estimates for wild bottlenose dolphins. 3.The most parsimonious model for calves indicated a significant time-variant decline in survival from an estimate similar to other populations (,c(1994,2001)=0.8621; 95% CI: 0.6851,0.9473) to a current estimate that is, to our knowledge, the lowest recorded for free-ranging bottlenose dolphins (,c(2002,2008)=0.3750; 95% CI: 0.2080,0.5782). 4.Information theoretic evidence ratios suggested that observed patterns in calf survival were 22 times more likely to be explained by a decline coincident with the opening of a second tailrace tunnel for a hydroelectric power station than by a decline in any other year or across multiple years. 5.Projections using an age-structured stochastic population model indicated that the current level of calf survival was unsustainable (population decline: 100% of model runs; population extinction: 41.5% of model runs) and was a key factor in the observed population decline in Doubtful Sound. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||