Radial basis functions with compact support for multivariate geostatistics

Matrix-valued radially symmetric covariance functions (also called radial basis functions in the numerical analysis literature) are crucial for the analysis, inference and prediction of Gaussian vector-valued random fields. This paper provides different methodologies for the construction of matrix-valued mappings that are positive definite and compactly supported over the sphere of a d-dimensional space, of a given radius. In particular, we offer a representation based on scaled mixtures of Askey functions; we also suggest a method of construction based on B-splines. Finally, we show that the very appealing convolution arguments are indeed effective when working in one dimension, prohibitive in two and feasible, but substantially useless, when working in three dimensions. We exhibit the statistical performance of the proposed models through simulation study and then discuss the computational gains that come from our constructions when the parameters are estimated via maximum likelihood. We finally apply our constructions to a North American Pacific Northwest temperatures dataset.     

Temperate rainforest response to climate change and disturbance agents in northwestern Patagonia (41°S) over the last 2600 years

We present detailed pollen and charcoal records from Lago Pichilafquén (~ 41°S) to decipher the effects of climate change and varying disturbance regimes on the composition and structure of the vegetation on the Andean foothills of northwestern Patagonia during the last 2600 yr. Here, temperate rainforests have dominated the landscape since 2600 cal yr BP with variations ranging from cool-temperate and wet north Patagonian rainforests to relatively warm and summer-drought-resistant Valdivian rainforests. We interpret relatively warm/dry conditions between 1900–2600, 690–750 and 320–430 cal yr BP, alternating with cold/wet conditions between 1500–1900, 750–1100 and 430–690 cal yr BP. Rapid deforestation and spread of plants introduced by Europeans occurred at 320 and 140 cal yr BP. The record includes five tephras with ages of 2130, 1460, 1310, 1210, and 340 cal yr BP, all of which precede local fire events and increases in trees favored by disturbance by less than 100 yr. We conclude that centennial-scale changes in the southern westerlies were the primary driver of vegetation shifts in northwestern Patagonia over the last 2600 yr. Within this interval, local disturbance regimes altered the structure, composition, and dynamics of the lowland rainforest vegetation during several discrete, short-lived episodes.     

Lateglacial and Holocene palaeohydrology in the western Mediterranean region: The Lake Estanya record (NE Spain)

The multi-proxy analysis of sediment cores recovered in karstic Lake Estanya (42°02′ N, 0°32′ E; 670 m a. s. l., NE Spain), located in the transitional area between the humid Pyrenees and the semi-arid Central Ebro Basin, provides the first high-resolution, continuous sedimentary record in the region, extending back the last 21 000 years. The integration of sedimentary facies, elemental and isotopical geochemistry and biogenic silica, together with a robust age model based on 17 AMS radiocarbon dates, enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation.Arid conditions, represented by shallow lake levels, predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum (21–18 cal kyrs BP) and the lateglacial, reaching their maximum intensity during the period 18–14.5 cal kyrs BP (including Heinrich event 1) and the Younger Dryas (12.9–11.6 cal kyrs BP). Less saline conditions characterized the 14.5–12.6 cal kyrs BP period, suggesting higher effective moisture during the Bölling/Allerød. The onset of more humid conditions started at 9.4 cal kyrs, indicating a delayed hydrological response to the onset of the Holocene which is also documented in several sites of the Mediterranean Basin. Higher, although fluctuating, Holocene lake levels were punctuated by a mid Holocene arid period between 4.8 and 4.0 cal kyrs BP. A major lake-level rise occurred at 1.2 cal kyrs BP, conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop, occurring around 800 cal yrs BP, which coincides with the Medieval Climate Anomaly.The main hydrological stages in Lake Estanya are in phase with most Western Mediterranean and North Atlantic continental and marine records, but our results also show similarities with other Iberian and northern African reconstructions, emphasizing peculiarities of palaeohydrological evolution of the Iberian Peninsula during the last deglaciation.     

California coastal management with a changing climate

With over 2,000 miles (3,218 km) of ocean and estuarine coastline, California faces significant coastal management challenges as a result of climate change-induced sea level rise. Under high emission scenarios, recent models predict 1.4 m or more of sea level rise by 2100, accompanied by increasing storm surges. This article investigates the most important issues facing coastal managers, explores the policy tools available for adapting to the impacts of climate change, assesses institutional constraints to adaptation, and identifies priorities for future research and policy action. We find that adaptation tools exist for dealing with anticipated increases in coastal erosion and flooding, but they involve significant costs and tradeoffs. In particular, coastal armoring, such as seawalls, can protect developed coastal lands, but destroys beaches and habitat. Although California already has policies and institutions that aim to balance the competing objectives for coastal development, management agencies are at the early stages of understanding how to facilitate adaptation. Research priorities to inform coastal adaptation planning include: (i) inventorying coastal resources to provide a firmer basis for balancing decisions on property and habitat protection, (ii) identifying opportunities for coastal habitat migration, (iii) assessing the vulnerabilities of existing and planned coastal infrastructure, and (iv) experimenting with alternatives to armoring as a way of managing the changing coastline.     

An objective Bayesian analysis of the change point problem

The Bayesian literature on the change point problem deals with the inference of a change in the distribution of a set of time-ordered data based on a sample of fixed size. This is the so-called retrospective or off-line analysis of the change point problem. A related but different problem is that of the sequential change point detection, mainly analyzed from a frequentist viewpoint. While the former typically focuses on the estimation of the position in which the change point occurs, the latter is a testing problem which has a natural formulation as a Bayesian model selection problem. In this paper we provide such a Bayesian formulation, which generalizes previous formulations such as the well-known CUSUM stopping rule. We show that the conventional improper priors (also called non-informative, objective or default), cannot be used either for sequential detection of the change or for retrospective estimation. Then, we propose objective intrinsic prior distributions for the unknown model parameters. The normal and Poisson cases are studied in detail and examples with simulated and real data are provided.     

Stratigraphical evidence of Late Holocene barrier breaching and extreme storms in lagoonal sediments of Ria Formosa, Algarve, Portugal

Stratigraphical, sedimentological and paleoecological studies undertaken in lagoonal sediments of the Ria Formosa barrier lagoon indicate that a number of present-day aligned beaches outcropping within the marsh and detached from mainland (marsh detached beaches, MDB) represent the remnants of former ephemeral flood deltas, which established following barrier breaching induced by extreme storms from circa 1270 BC onwards. Dating of these beaches suggests that they resulted from multiple events of flooding separated both in time and space. Repeated emplacement of tidal deltas following overwash of the same location of the barrier is represented in the stratigraphical record by buried and partly overlapping marsh beaches. It is suggested that further refinement of the data presented in this paper and the extension of the stratigraphic survey to the entire lagoonal space will substantiate the usefulness of the stratigraphic record as a proxy to hindcast a time series of extreme storminess extending far beyond the instrumental and historical records.     

Entropy Econometrics for combining regional economic forecasts: A Data-Weighted Prior Estimator

Forecast combination has been studied in econometrics for a long time, and the literature has shown the superior performance of forecast combination over individual predictions. However, there is still controversy on which is the best procedure to specify the forecast weights. This paper explores the possibility of using a procedure based on Entropy Econometrics, which allows setting the weights for the individual forecasts as a mixture of different alternatives. In particular, we examine the ability of the Data-Weighted Prior Estimator proposed by Golan (J Econom 101(1):165–193, 2001) to combine forecasting models in a context of small sample sizes, a relative common scenario when dealing with time series for regional economies. We test the validity of the proposed approach using a simulation exercise and a real-world example that aims at predicting gross regional product growth rates for a regional economy. The forecasting performance of the Data-Weighted Prior Estimator proposed is compared with other combining methods. The simulation results indicate that in scenarios of heavily ill-conditioned datasets the approach suggested dominates other forecast combination strategies. The empirical results are consistent with the conclusions found in the numerical experiment.     

Landslide risk perception and communication for disaster risk management in mountain areas of developing countries: a Mexican foretaste

The increasing impact of disasters at local,national,regional and global scales in recent decades has provided enough evidence to urgently direct attention towards the necessity of disaster risk reduction and management,and this requires knowledge.Knowledge without communication is barren,and to communicate the risk of disaster it is necessary to understand the perception of the people at risk.In particular,this paper deals with the necessity to delineate strategies of risk communication in pursuance of risk knowledge as a core of disaster risk reduction and management,especially in mountain areas of developing countries.To portray this issue,an analysis of landslide risk perception in terms of experience,landslide risk awareness,exposure,preparedness,and risk communication and trust was undertaken in the municipality of Teziutlán,Puebla,Mexico,an area that has been affected for several decades by episodes of mass movement.Analysis of the responses to a risk perception questionnaire has offered valuable insights in terms of the information and knowledge most required by the people living in the area of interest,in order to devise a realistic and functional strategy to communicate the risk of a landslide disaster.This includes better understanding of controlling factorsand drivers of this risk,and the establishment of potential trusted sources of risk communication.Beyond considering practical matters of risk assessment and management,risk perception and communication can increase the resilience of vulnerable people,and can enhance capacity building for present and future generations.