Steven M. Babin

A New Model of the Oceanic Evaporation Duct

Abstract Failure to consider anomalous propagation of microwave radiation in the troposphere may result in erroneous meteorological radar measurements. The most commonly occurring anomalous propagation phenomenon over the ocean is the evaporation duct. The height of this duct is dependent on atmospheric variables and is a major input to microwave propagation prediction models. This evaporation duct height is determined from an evaporation duct model using bulk measurements. Two current evaporation duct models in widespread operational use are examined. We propose and test a new model that addresses deficiencies in these two models. The new model uses recently refined bulk similarity expressions developed for the determination of the ocean surface energy budget in the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. Comparison of these models is made using data collected from a boat off Wallops Island, Virginia, during a range of seasons and weather conditions and from the tid...

Pediatric patient asthma-related emergency department visits and admissions in Washington, DC, from 2001–2004, and associations with air quality, socio-economic status and age group

BackgroundThe District of Columbia (DC) Department of Health, under a grant from the US Centers for Disease Control and Prevention, established an Environmental Public Health Tracking Program. As part of this program, the goals of this contextual pilot study are to quantify short-term associations between daily pediatric emergency department (ED) visits and admissions for asthma exacerbations with ozone and particulate concentrations, and broader associations with socio-economic status and age group.MethodsData included daily counts of de-identified asthma-related pediatric ED visits for DC residents and daily ozone and particulate concentrations during 2001–2004. Daily temperature, mold, and pollen measurements were also obtained. After a cubic spline was applied to control for long-term seasonal trends in the ED data, a Poisson regression analysis was applied to the time series of daily counts for selected age groups.ResultsAssociations between pediatric asthma ED visits and outdoor ozone concentrations were significant and strongest for the 5–12 year-old age group, for which a 0.01-ppm increase in ozone concentration indicated a mean 3.2% increase in daily ED visits and a mean 8.3% increase in daily ED admissions. However, the 1–4 yr old age group had the highest rate of asthma-related ED visits. For 1–17 yr olds, the rates of both asthma-related ED visits and admissions increased logarithmically with the percentage of children living below the poverty threshold, slowing when this percentage exceeded 30%.ConclusionSignificant associations were found between ozone concentrations and asthma-related ED visits, especially for 5–12 year olds. The result that the most significant ozone associations were not seen in the age group (1–4 yrs) with the highest rate of asthma-related ED visits may be related to the clinical difficulty in accurately diagnosing asthma among this age group. We observed real increases in relative risk of asthma ED visits for children living in higher poverty zip codes versus other zip codes, as well as similar logarithmic relationships for visits and admissions, which implies ED over-utilization may not be a factor. These results could suggest designs for future epidemiological studies that include more information on individual exposures and other risk factors.

A data-driven epidemiological prediction method for dengue outbreaks using local and remote sensing data

BackgroundDengue is the most common arboviral disease of humans, with more than one third of the world’s population at risk. Accurate prediction of dengue outbreaks may lead to public health interventions that mitigate the effect of the disease. Predicting infectious disease outbreaks is a challenging task; truly predictive methods are still in their infancy.MethodsWe describe a novel prediction method utilizing Fuzzy Association Rule Mining to extract relationships between clinical, meteorological, climatic, and socio-political data from Peru. These relationships are in the form of rules. The best set of rules is automatically chosen and forms a classifier. That classifier is then used to predict future dengue incidence as either HIGH (outbreak) or LOW (no outbreak), where these values are defined as being above and below the mean previous dengue incidence plus two standard deviations, respectively.ResultsOur automated method built three different fuzzy association rule models. Using the first two weekly models, we predicted dengue incidence three and four weeks in advance, respectively. The third prediction encompassed a four-week period, specifically four to seven weeks from time of prediction. Using previously unused test data for the period 4–7 weeks from time of prediction yielded a positive predictive value of 0.686, a negative predictive value of 0.976, a sensitivity of 0.615, and a specificity of 0.982.ConclusionsWe have developed a novel approach for dengue outbreak prediction. The method is general, could be extended for use in any geographical region, and has the potential to be extended to other environmentally influenced infections. The variables used in our method are widely available for most, if not all countries, enhancing the generalizability of our method.

Surface Duct Height Distributions for Wallops Island, Virginia, 19851994

Abstract A surface duct is defined as a layer of air adjacent to the earths surface, in which temperature and humidity gradients cause microwave energy originating within the layer to be sufficiently refracted so that it becomes trapped into propagating along the surface. This layer then acts as a waveguide for microwave propagation and results in propagation beyond the horizon. Failure to consider such conditions may result in erroneous radar meteorological measurements. These ducts can be located by examining refractivity profiles derived from atmospheric measurements. Since 1985, over 3900 profiles of microwave refractivity have been measured using an instrumented helicopter over the Atlantic Ocean off the coast of Wallops Island, Virginia. This helicopter data acquisition system provides higher-resolution measurements than those obtained from radiosondes. This paper presents the heights and associated frequency distributions of surface ducts as determined from these profiles. The year is divided into...

Satellite Imagery of Sea Surface Temperature Cooling in the Wake of Hurricane Edouard (1996)

It is well documented that in the wake of a hurricane there is significant cooling of sea surface temperature (SST) (Hazelworth 1968; Brand 1971; Federov 1972; Stramma et al. 1986; Shay et al. 1992; Pudov et al. 1978; Pudov 1980; Black and Holland 1995). Figure 1 represents a dramatic recent example of such cooling observed from satellite radiometer data after the passage of Hurricane Edouard (1996) off the east coast of the United States. The figure is a composite of SSTs derived from Advanced Very High Resolution Radiometer (AVHRR) data broadcast over 3 days (0531 UTC 31 August 1996–1001 UTC 3 September 1996) by the polar-orbiting NOAA-12 and NOAA-14 satellites. This sea surface temperature image clearly shows a swath of water approximately 48C less than the surrounding water centered slightly east of the track of Hurricane Edouard’s eye. In this paper, we describe the process used to construct Fig. 1 from AVHRR data. We also review the various mechanisms by which hurricanes induce SST cooling.

A meta-analysis of point-of-care laboratory tests in the diagnosis of novel 2009 swine-lineage pandemic influenza A (H1N1)

This paper reviews 14 published studies describing performance characteristics, including sensitivity and specificity, of commercially available rapid, point-of-care (POC) influenza tests in patients affected by an outbreak of a novel swine-related influenza A (H1N1) that was declared a pandemic in 2009. Although these POC tests were not intended to be specific for this pandemic influenza strain, the nonspecialized skills required and the timeliness of results make these POC tests potentially valuable for clinical and public health use. Pooled sensitivity and specificity for the POC tests studied were 68% and 81%, respectively, but published values were not homogeneous with sensitivities and specificities ranging from 10% to 88% and 51% to 100%, respectively. Pooled positive and negative likelihood ratios were 5.94 and 0.42, respectively. These results support current recommendations for use of rapid POC tests when H1N1 is suspected, recognizing that positive results are more reliable than negative results in determining infection, especially when disease prevalence is high.

Data-driven approach for creating synthetic electronic medical records

BackgroundNew algorithms for disease outbreak detection are being developed to take advantage of full electronic medical records (EMRs) that contain a wealth of patient information. However, due to privacy concerns, even anonymized EMRs cannot be shared among researchers, resulting in great difficulty in comparing the effectiveness of these algorithms. To bridge the gap between novel bio-surveillance algorithms operating on full EMRs and the lack of non-identifiable EMR data, a method for generating complete and synthetic EMRs was developed.MethodsThis paper describes a novel methodology for generating complete synthetic EMRs both for an outbreak illness of interest (tularemia) and for background records. The method developed has three major steps: 1) synthetic patient identity and basic information generation; 2) identification of care patterns that the synthetic patients would receive based on the information present in real EMR data for similar health problems; 3) adaptation of these care patterns to the synthetic patient population.ResultsWe generated EMRs, including visit records, clinical activity, laboratory orders/results and radiology orders/results for 203 synthetic tularemia outbreak patients. Validation of the records by a medical expert revealed problems in 19% of the records; these were subsequently corrected. We also generated background EMRs for over 3000 patients in the 4-11 yr age group. Validation of those records by a medical expert revealed problems in fewer than 3% of these background patient EMRs and the errors were subsequently rectified.ConclusionsA data-driven method was developed for generating fully synthetic EMRs. The method is general and can be applied to any data set that has similar data elements (such as laboratory and radiology orders and results, clinical activity, prescription orders). The pilot synthetic outbreak records were for tularemia but our approach may be adapted to other infectious diseases. The pilot synthetic background records were in the 4-11 year old age group. The adaptations that must be made to the algorithms to produce synthetic background EMRs for other age groups are indicated.

A survey of usage protocols of syndromic surveillance systems by state public health departments in the United States

OBJECTIVE To broadly describe current syndromic surveillance systems in use throughout the United States and to provide basic descriptive information on responses to syndromic system signals. METHODS Cross-sectional survey (telephone and e-mail) of state epidemiologists in all 50 states and the District of Columbia. RESULTS Forty-one states participated in the survey for a response rate of 80 percent. Thirty-three states (80%) had at least one syndromic surveillance system in addition to BioSense operating within the state. Every state with an urban area at highest risk of a terrorist attack reported monitoring syndromic surveillance data, and a states overall preparedness level was not related to the presence (or lack) of operational syndromic surveillance systems. The most common syndromic surveillance systems included BioSense (n = 20, 61%) and RODS (n = 13, 39%). Seventy-six percent of states with syndromic surveillance initiated investigations at the state level, 64 percent at the county level, and 45 percent at both the state and county levels. CONCLUSIONS The majority of states reported using syndromic surveillance systems, with greatest penetration in those at highest risk for a terrorist attack. Most states used multiple systems and had varied methods (central and local) of responding to alerts, indicating the need for detailed response protocols.

LKB-Based Evaporation Duct Model Comparison with Buoy Data

Abstract A wave-riding catamaran with a mast-traveling sensor package (profiling buoy) was developed to make fine-scale atmospheric measurements within the first meter above the ocean surface. These measurements are used to generate time-averaged modified refractivity (M) profiles that are then compared with those determined from four evaporation duct models based on the surface layer theory of Liu, Katsaros, and Businger (LKB). Model inputs are derived from measurements from masts on the R/V Chessie and from a tethered sea surface temperature buoy. Because electromagnetic propagation is critically dependent on the M-profile slopes, different analytical techniques are employed to compare the curvature of the model profiles with that of the profiles measured by the profiling buoy. One comparison criterion was to use the rms M slope difference between the model and a curve fit to the buoy profile data. Another analytical technique was to use the rms M difference after mean M removal between the model and th...

Medicaid patient asthma-related acute care visits and their associations with ozone and particulates in Washington, DC, from 1994–2005

The primary objective of this ecologic and contextual study is to determine statistically significant short-term associations between air quality (daily ozone and particulate concentrations) and Medicaid patient general acute care daily visits for asthma exacerbations over 11 years for Washington, DC residents, and to identify regions and populations that may experience increased asthma exacerbations related to air quality. After removing long-term trends and day-of-week effects in the Medicaid data, Poisson regression was applied to daily time series data. Significant associations were found between asthma-related general acute care visits and ozone concentrations. Significant associations with both ozone and PM2.5 concentrations were observed for 5- to 12-year-olds. While poor air quality was closely associated with asthma exacerbations observed in acute care visits in areas where Medicaid enrollment was high, the strongest associations between asthma-related visits and air quality were not always for the areas with the highest Medicaid enrollment.