Domain choice in an experimental nested modeling prediction system for South America

The purposes of this paper are to evaluate the new version of the regional model, RegCM3, over South America for two test seasons, and to select a domain for use in an experimental nested prediction system, which incorporates RegCM3 and the European Community-Hamburg (ECHAM) general circulation model (GCM). To evaluate RegCM3, control experiments were completed with RegCM3 driven by both the NCEP/NCAR Reanalysis (NNRP) and ECHAM, using a small control domain (D-CTRL) and integration periods of January–March 1983 (El Niño) and January–March 1985 (La Niña). The new version of the regional model captures the primary circulation and rainfall differences between the two years over tropical and subtropical South America. Both the NNRP-driven and ECHAM-driven RegCM3 improve the simulation of the Atlantic intertropical convergence zone (ITCZ) compared to the GCM. However, there are some simulation errors. Irrespective of the driving fields, weak northeasterlies associated with reduced precipitation are observed over the Amazon. The simulation of the South Atlantic convergence zone is poor due to errors in the boundary condition forcing which appear to be amplified by the regional model. To select a domain for use in an experimental prediction system, sensitivity tests were performed for three domains, each of which includes important regional features and processes of the climate system. The domain sensitivity experiments were designed to determine how domain size and the location of the GCM boundary forcing affect the regional circulation, moisture transport, and rainfall in two years with different large scale conditions. First, the control domain was extended southward to include the exit region of the Andes low level jet (D-LLJ), then eastward to include the South Atlantic subtropical high (D-ATL), and finally westward to include the subsidence region of the South Pacific subtropical high and to permit the regional model more freedom to respond to the increased resolution of the Andes Mountains (D-PAC). In order to quantify differences between the domain experiments, measures of bias, root mean square error, and the spatial correlation pattern were calculated between the model results and the observed data for the seasonal average fields. The results show the GCM driving fields have remarkable control over the RegCM3 simulations. Although no single domain clearly outperforms the others in both seasons, the control domain, D-CTRL, compares most favorably with observations. Over the ITCZ region, the simulations were improved by including a large portion of the South Atlantic subtropical high (D-ATL). The methodology presented here provides a quantitative basis for evaluating domain choice in future studies

Deepwater Horizon oil spill exposure and child health: a longitudinal analysis

The BP Deepwater Horizon oil spill (DHOS) created widespread concern about threats to health among residents of the Louisiana Gulf Coast. This study uses data from the Resilient Children, Youth, and Communities study—a longitudinal cohort survey of households with children in DHOS-affected areas of South Louisiana—to consider the effect of DHOS exposure on health trajectories of children, an especially vulnerable population subgroup. Results from latent linear growth curve models show that family DHOS exposure via physical contact and job/income loss both negatively influenced initial child health. However, the effects of physical exposure dissipated over time while the effects of job/income loss persisted. This pattern holds for both general child health and the number of recent physical health problems children had experienced. These findings help to bridge the literature on disaster impacts and resilience/vulnerability, with the literature on socioeconomic status as a fundamental cause of health outcomes over the life course

Intraseasonal (30-60 day) variability in the global tropics: principal modes and their evolution

The evolution of the 30-60 day intraseasonal (Madden-Julian) oscillation (MJO), during boreal winter and summer, is studied by means of extended empirical orthogonal function analyses. For both seasons, the patterns describe an eastward traveling large-scale oscillatory regime with a period of approximately 45 days. Several atmospheric variables display a zonal wavenumber one pattern approximately symmetric about the equator. The seasonal variation of the MJO is investigated, especially in terms of the intraseasonal variability of the tropical convection. We find that the latitudinal location of the largest outgoing longwave radiation anomalies is directly related to the seasonal meridional shifts of the tropical convection in the Indo-Australian and Central American-South American regions. In the eastern hemisphere, the MJO affects the monsoons over India during boreal summer and over Australia during austral summer. In the western hemisphere the MJO has the greatest impact on convection over Northeast Brazil during austral summer and over Central America during boreal summer. The MJO-related evolution of 925-hPa specific humidity patterns (not previously documented) show remarkable seasonal dependence. The boreal summer patterns contain a large-scale component quite similar to that shown in the sea level pressure patterns. The austral summer patterns show strong regional variability that might indicate the interactions of the MJO with deep tropical convection in certain areas, such as along the South Pacific Convergence Zone and over northern South America.Pages: 373-38