44 research outputs found
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Synthesis of Pacific Ocean Climate and Ecosystem Dynamics
The goal of the Pacific Ocean Boundary Ecosystem and Climate Study
(POBEX) was to diagnose the large-scale climate controls on regional transport
dynamics and lower trophic marine ecosystem variability in Pacific Ocean boundary
systems. An international team of collaborators shared observational and eddy-resolving
modeling data sets collected in the Northeast Pacific, including the Gulf of
Alaska (GOA) and the California Current System (CCS), the Humboldt or Peru-Chile
Current System (PCCS), and the Kuroshio-Oyashio Extension (KOE) region. POBEX
investigators found that a dominant fraction of decadal variability in basin- and
regional-scale salinity, nutrients, chlorophyll, and zooplankton taxa is explained by a
newly discovered pattern of ocean-climate variability dubbed the North Pacific Gyre
Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO). NPGO dynamics
are driven by atmospheric variability in the North Pacific and capture the decadal
expression of Central Pacific El Niños in the extratropics, much as the PDO captures
the low-frequency expression of eastern Pacific El Niños. By combining hindcasts
of eddy-resolving ocean models over the period 1950â2008 with model passive
tracers and long-term observations (e.g., CalCOFI, Line-P, Newport Hydrographic
Line, Odate Collection), POBEX showed that the PDO and the NPGO combine to
control low-frequency upwelling and alongshore transport dynamics in the North
Pacific sector, while the eastern Pacific El Niño dominates in the South Pacific.
Although different climate modes have different regional expressions, changes in
vertical transport (e.g., upwelling) were found to explain the dominant nutrient and
phytoplankton variability in the CCS, GOA, and PCCS, while changes in alongshore
transport forced much of the observed long-term change in zooplankton species
composition in the KOE as well as in the northern and southern CCS. In contrast,
cross-shelf transport dynamics were linked to mesoscale eddy activity, driven by
regional-scale dynamics that are largely decoupled from variations associated with
the large-scale climate modes. Preliminary findings suggest that mesoscale eddies
play a key role in offshore transport of zooplankton and impact the life cycles of
higher trophic levels (e.g., fish) in the CCS, PCCS, and GOA. Looking forward,
POBEX results may guide the development of new modeling and observational
strategies to establish mechanistic links among climate forcing, mesoscale circulation,
and marine population dynamics
Family Resources in Two Generations and School Readiness Among Children of Teen Parents
Overall, children born to teen parents experience disadvantaged cognitive achievement at school entry compared with children born to older parents. However, within this population, there is variation, with a significant fraction of teen parentsâ children acquiring adequate preparation for school entry during early childhood. We ask whether the family background of teen parents explains this variation. We use data on children born to teen mothers from three waves of the Early Childhood Longitudinal Study-Birth Cohort (N ~ 700) to study the association of family background with childrenâs standardized reading and mathematics achievement scores at kindergarten entry. When neither maternal grandparent has completed high school, childrenâs scores on standardized assessments of math and reading achievement are one-quarter to one-third of a standard deviation lower compared with families where at least one grandparent finished high school. This association is net of teen mothersâ own socioeconomic status in the year prior to childrenâs school entry
A comparison of methods for temporal analysis of aoristic crime
Objectives: To test the accuracy of various methods previously proposed (and one new method) to estimate offence times where the actual time of the event is not known.
Methods: For 303 thefts of pedal cycles from railway stations, the actual offence time was determined from closed-circuit television and the resulting temporal distribution compared against commonly-used estimated distributions using circular statistics and analysis of residuals.
Results: Aoristic analysis and allocation of a random time to each offence allow accurate estimation of peak offence times. Commonly-used deterministic methods were found to be inaccurate and to produce misleading results.
Conclusions: It is important that analysts use the most accurate methods for temporal distribution approximation to ensure any resource decisions made on the basis of peak times are reliable