Associations among chlorophyll concentration and climatic variables for Suisun Bay and the Sacramento-San Joaquin Delta [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The recent changes in phytoplankton production and community composition within the Suisun Bay and Sacramento-San Joaquin Delta may be related to climate. Chlorophyll a concentration, decreased by 42% (spring-summer) and 29% (fall) between 1972 through 1976 and 1977 through 1981. The decrease in biomass was characterized by a shift in phytoplankton community dominance from Skeletonema spp., Cyclotella spp. and Coscinodiscus spp. to Melosira granulata. The possible influence of climate on phytoplankton abundance was suggested by multivariate statistical analyses that demonstrated an association between changes in phytoplankton community composition and abundance between 1975 and 1982 and the climate related variables wind velocity, precipitation, river flow and water temperature.

Application of neural networks to the ranking of perinatal variables influencing birthweight.

In this paper we compare Multi-Layer Perceptrons (a neural network type) with Multivariate Linear Regression in predicting birthweight from nine perinatal variables which are thought to be related. Results show, that seven of the nine variables, i.e., gestational age, mother's body-mass index (BMI), sex of the baby, mother's height, smoking, parity and gravidity, are related to birthweight. We found no significant relationship between birthweight and each of the two variables, i.e., maternal age and social class.

A preliminary description of climatology in the western United States

We describe the climatology of the western United States as seen from two 1-month perspectives, January and July 1988, of the National Meteorological Center large-scale global analysis, the Colorado State University Regional Atmospheric Modeling System (RAMS), and various station observation sets. An advantage of the NMC analysis and the RAMS is that they provide a continuous field interpolation of the meteorological variables. It is more difficult to describe spatial meteorological fields from the available sparse station networks. We assess accuracy of the NMC analysis and RAMS by finding differences between the analysis, the model, and station values at the stations. From these comparisons, we find that RAMS has much more well-developed mesoscale circulation, especially in the surface wind field. However, RAMS climatological and transient fields do not appear to be substantially closer than the larger-scale analysis to the station observations. The RAMS model does provide other meteorological variables, such as precipitation, which are not readily available from the archives of the global analysis. Thus, RAMS could, at the least, be a tool to augment the NMC large-scale analyses.

Time series analyses of biological and environmental variables for Suisun Bay and the Sacramento and San Joaquin rivers

EXTRACT (SEE PDF FOR FULL ABSTRACT): Arima analysis was used to compute cross-correlations between principal component axes that described environmental variables, chlorophyll concentration and zooplankton density for the Sacramento and San Joaquin rivers and Suisun Bay. ... Cross-correlations among the time series may provide information about links between environmental and biological variables within the estuary and the possible influence of climate.

Interactions between climatic variables controlling subalpine tree growth: implications for climatic history of the Sierra Nevada, California

EXTRACT (SEE PDF FOR FULL ABSTRACT): Tree-ring records from foxtail pine (Pinus balfouriana) and western juniper (Juniperus occidentalis) growing near tree line in the eastern Sierra Nevada, California, show strong correlations with summer temperature and winter precipitation. Response surfaces portraying tree growth as a function of summer temperature and winter precipitation indicate a strong interaction between these variables in controlling growth. ... Above average growth for both foxtail pine and western juniper from AD 1480 to 1570 can be interpreted as indicating an extended period of warm, moist conditions unequalled during the 20th century.