[1] We present a model and application designed to study the coupled land-atmosphere hydrologic cycle, following water from its inflow into a region by horizontal atmospheric transport through surface-atmosphere exchange processes and aquifer recharge to outflow as runoff and river discharge. The model includes a two-way water flow among its major reservoirs (atmosphere, vadose zone, groundwater, surface water, river). A unique feature of the model is that phreatophytic interactions are included when the water table intersects the root zone. The model emulates a uniform grid box of an atmospheric general circulation model, but with finer horizontal resolution for the land processes, and forms a test bed for developing continental-scale simulation of the hydrologic cycle. The model is calibrated using the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) observations for 1987 and validated using FIFE observations for 1988 and 1989. Four physical factors emerge as important for simulating the FIFE water cycle: effective relative humidity for initiating stable (large scale) condensation, length of the growing season, amount of available soil water, and cloud cover parameterization. Further evaluation uses water table and river discharge measurements for years up to 1993. The model simulates multiyear behavior in the hydrologic cycle reasonably well. Average differences between FIFE observations and simulated fluxes during the calibration period are only a few percent, including fluxes not specifically calibrated. Model-observation differences in surface sensible and latent heat fluxes are larger during the 1988 drought but recover to relatively small values for 1989, suggesting some difficulty in simulating hydrologic extremes occurring outside the calibration conditions. A model sensitivity study using statistical disaggregation to allow precipitation to fall on only a portion of the landscape indicates that spatial disaggregation of precipitation can have strong impact on groundwater storage and surface discharge, potentially improving agreement between observed and simulated streamflow. Water redistributed through the model's aquifer-river network can at times raise the water table high enough for water to seep back to the vegetation root zone and increase evapotranspiration. During relatively dry periods, up to 33% of monthly evapotranspiration was derived from groundwater-supported evapotranspiration, emphasizing the need to quantify better aquifer-atmosphere interaction. The work also demonstrates the feasibility and utility of fully coupled water budgeting schemes.

A total of 188 yearling steers of predominantly Angus and Hereford breeds, with mean body weight of 299 kg, were used in this study, which started on 8 April and finished on 3 October, to assess the effects of environmental factors on feed intake of steers in various housing systems. Housing consisted of outside lots with access to overhead shelter, outside lots with no overhead shelter and a cold confinement building. Ad libitum corn, 2.27 kg of 35% dry matter whole plant sorghum silage and 0.68 kg of a 61% protein-vitamin-mineral supplement was offered. Feed that was not consumed was measured to determine feed intake. The temperature data were recorded by hygro-thermographs. Hourly temperatures and humidity were used to develop weather variables. Regression analysis was used and weather variables were regressed on dry matter intake (DMI). When addition of a new variable did not improve R (2) more than one unit, then the number of variables in the model was truncated. Cattle in confinement had lower DMI than those in open lots and those in open lots with access to an overhead shelter (P < 0.05). Cattle in outside lots with access to overhead shelter had similar DMI compared to those in open lots (P = 0.065). Effect of heat was predominantly displayed in August in the three housing systems. In terms of explaining variation in DMI, in outside lots with access to overhead shelter, average and daytime temperatures were important factors, whereas in open lots, nocturnal, peak and average temperatures were important factors. In confinement buildings, the previous day's temperature and humidity index were the most important factors explaining variation in DMI. Results show the effect of housing and weather variables on DMI in summer and when considering these results, cattle producers wishing to improve cattle feedlot performance should consider housing conditions providing less stress or more comfort.

IMPORTANCEIn the United States, Black and Hispanic children have higher rates of asthma and asthma-related morbidity compared with White children and disproportionately reside in communities with economic deprivation.OBJECTIVE To determine the extent to which neighborhood-level socioeconomic indicators explain racial and ethnic disparities in childhood wheezing and asthma. DESIGN, SETTING, AND PARTICIPANTSThe study population comprised children in birth cohorts located throughout the United States that are part of the Children's Respiratory and Environmental Workgroup consortium. Cox proportional hazard models were used to estimate hazard ratios (HRs) of asthma incidence, and logistic regression was used to estimate odds ratios of early and persistent wheeze prevalence accounting for mother's education, parental asthma, smoking during pregnancy, child's race and ethnicity, sex, and region and decade of birth.EXPOSURES Neighborhood-level socioeconomic indicators defined by US census tracts calculated as z scores for multiple tract-level variables relative to the US average linked to participants' birth record address and decade of birth. The parent or caregiver reported the child's race and ethnicity.MAIN OUTCOMES AND MEASURES Prevalence of early and persistent childhood wheeze and asthma incidence. RESULTSOf 5809 children, 46% reported wheezing before age 2 years, and 26% reported persistent wheeze through age 11 years. Asthma prevalence by age 11 years varied by cohort, with an overall median prevalence of 25%. Black children (HR, 1.47; 95% CI, and Hispanic children (HR, 1.29; 95% CI, 1.09-1.53) were at significantly increased risk for asthma incidence compared with White children, with onset occurring earlier in childhood. Children born in tracts with a greater proportion of low-income households, population density, and poverty had increased asthma incidence. Results for early and persistent wheeze were similar. In effect modification analysis, census variables did not significantly modify the association between race and ethnicity and risk for asthma incidence; Black and Hispanic children remained at higher risk for asthma compared with White children across census tracts socioeconomic levels. CONCLUSIONS AND RELEVANCEAdjusting for individual-level characteristics, we observed neighborhood socioeconomic disparities in childhood wheeze and asthma. Black and Hispanic children had more asthma in neighborhoods of all income levels. Neighborhood-and individual-level characteristics and their root causes should be considered as sources of respiratory health inequities.

This study explores surface-layer stability effects on the Penman-Monteith (P-M) method, one of the most widely used methods to estimate evapotranspiration (ET). Stability correction is applied to the original (neutral stability) formula by using atmospheric exchange coefficients developed by LOUIS et al. (1981). First, the effects of stability on the P-M formula are explored theoretically. ET is then computed from field data using both P-M formulas and the values are compared to measured ET from Bowen-ratio and lysimeter data. Theoretical investigation of the P-M formula is performed by varying stability conditions for a range of vapor pressure deficit and canopy conductance. Infinitely large canopy conductance (zero canopy resistance) gives potential ET with results similar to MAHRT and EK (1984): the stability-dependent formula gives larger (smaller) potential ET than the original formula under unstable (stable) conditions. For finite canopy conductance, ET behaves differently from potential ET as a result of coupling between canopy and atmospheric conductances. Stability-dependent ET values become smaller than the original formula values under extreme unstable conditions (when atmospheric conductance becomes large compared to canopy conductance) because stability-dependent sensible heat flux is considerably larger than its neutral counterpart under same net input energy. Field data collected during both wet and dry growing seasons indicate that both P-M formulas track the Bowen-ET estimates and lysimeter measurements quite closely.

A sensitivity study is performed to examine the potential effect of spatial variations in sea surface temperature (SST) that typically are not resolved in general climate models (GCMs). The study uses a single-column atmospheric model, representing a grid box of a GCM, that overlies a surface domain divided into many subgrid cells. The model is driven by boundary conditions representative of the Gulf Stream off the mid-Atlantic coast of the United States, for the year 1987. A heterogeneous simulation, which includes subgrid spatial variability in SST, is contrasted with a homogeneous simulation, which assigns spatial mean SST to all cells. In summer, the presence of both stable and unstable surface layers in the heterogeneous domain causes heterogeneous-homogeneous differences in monthly, spatially averaged surface latent-heat flux of up to 47%. In contrast, in winter, the surface layer is unstable everywhere and heterogeneous-homogeneous differences in latent heat flux are smaller. Spatially averaged, surface sensible heat flux shows less influence of SST heterogeneity because this flux during summer is small. Further simulation suggests that a GCM can capture the effect of spatially varying boundary layer stability by resolving it just at the surface. The SST heterogeneity is also capable of driving sea-breeze-type circulations. Scale analysis suggests that typical resolution of contemporary climate GCMs will generally be insufficient to resolve these circulations. Disciplines