Paul E. Bieringer

The Impact of Temperature on the Bionomics of Aedes (Stegomyia) Aegypti, with Special Reference to the Cool Geographic Range Margins

ABSTRACT The mosquito Aedes (Stegomyia) aegypti (L.), which occurs widely in the subtropics and tropics, is the primary urban vector of dengue and yellow fever viruses, and an important vector of chikungunya virus. There is substantial interest in how climate change may impact the bionomics and pathogen transmission potential of this mosquito. This Forum article focuses specifically on the effects of temperature on the bionomics of Ae. aegypti, with special emphasis on the cool geographic range margins where future rising temperatures could facilitate population growth. Key aims are to: 1) broadly define intra-annual (seasonal) patterns of occurrence and abundance of Ae. aegypti, and their relation to climate conditions; 2) synthesize the existing quantitative knowledge of how temperature impacts the bionomics of different life stages of Ae. aegypti; 3) better define the temperature ranges for which existing population dynamics models for Ae. aegypti are likely to produce robust predictions; 4) explore potential impacts of climate warming on human risk for exposure to Ae. aegypti at its cool range margins; and 5) identify knowledge or data gaps that hinder our ability to predict risk of human exposure to Ae. aegypti at the cool margins of its geographic range now and in the future. We first outline basic scenarios for intra-annual occurrence and abundance patterns for Ae. aegypti, and then show that these scenarios segregate with regard to climate conditions in selected cities where they occur. We then review how near-constant and intentionally fluctuating temperatures impact development times and survival of eggs and immatures. A subset of data, generated in controlled experimental studies, from the published literature is used to plot development rates and survival of eggs, larvae, and pupae in relation to water temperature. The general shape of the relationship between water temperature and development rate is similar for eggs, larvae, and pupae. Once the lower developmental zero temperature (10–14°C) is exceeded, there is a near-linear relationship up to 30°C. Above this temperature, the development rate is relatively stable or even decreases slightly before falling dramatically near the upper developmental zero temperature, which occurs at ∼38–42°C. Based on life stage-specific linear relationships between water temperature and development rate in the 15–28°C range, the lower developmental zero temperature is estimated to be 14.0°C for eggs, 11.8°C for larvae, and 10.3°C for pupae. We further conclude that available population dynamics models for Ae. aegypti, such as CIMSiM and Skeeter Buster, likely produce robust predictions based on water temperatures in the 16–35°C range, which includes the geographic areas where Ae. aegypti and its associated pathogens present the greatest threat to human health, but that they may be less reliable in cool range margins where water temperatures regularly fall below 15°C. Finally, we identify knowledge or data gaps that hinder our ability to predict risk of human exposure to Ae. aegypti at the cool margins of its range, now and in the future, based on impacts on mosquito population dynamics of temperature and other important factors, such as water nutrient content, larval density, presence of biological competitors, and human behavior.

METHODS FOR ESTIMATING THE ATMOSPHERIC RADIATION RELEASE FROM THE FUKUSHIMA DAI-ICHI NUCLEAR POWER PLANT

WHat: A multidisciplinary group of scientists and engineers from academia/private industry/ government/national laboratories in the United States, Japan, and Europe convened to discuss the Fukushima Dai-ichi nuclear power plant incident, observations of the radiation deposition patterns, and methods to use these measurements to better estimate the total radioactive material released into the atmosphere. WHEn: 22–23 February 2012 WHErE: National Center for Atmospheric Research, Boulder, Colorado O n 11 March 2011, a 9.0-magnitude earthquake off the east coast of Japan and subsequent tsunami caused widespread damage in northeastern Japan and resulted in a cooling system failure, partial reactor core meltdown, and radiation release from the Fukushima Dai-ichi nuclear power plant (FD-NPP). Following the devastating earthquake and tsunami that severely damaged the nuclear power plant in Fukushima, Japan, an unknown quantity of radioactive material was released into the air and water surrounding the crippled nuclear power plant. Assessments of the remaining nuclear fuel following the incident have allowed the scientific community to approach a consensus on the total amount of radioactive material released from the FD-NPP. What is still unclear, however, is the timing of the releases and how much of the radioactive material was released into the atmosphere versus directly into the nearby ocean. The complexity of this disaster—which included disabled observation systems; multiple intermittent explosive releases of radioactive materials combined with a long-duration continuous release of radiation at an unknown rate; and changes in boundary layer depth, wind speed/direction, and precipitation in the region surrounding the FD-NPP—complicates these estimates. An accurate estimate of the radiation released into the atmosphere from the FD-NPP is necessary for scientists and government officials to make informed decisions that impact the estimation of long-term doses and the safety of people living and working near Fukushima. While extensive observational surveys of the radiation fallout pattern have been made, using these measurements to estimate the magnitude and timing of radiation released into the atmosphere versus the ocean remains a challenging undertaking. Despite the large number of observations available, they cover only a small fraction of the area and time period. Consequently, current estimates include a large degree of uncertainty, resulting in correspondingly large uncertainties regarding the total amount of radiation fallout and associated environmental impacts, which significantly hamper the Japanese

A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part 2: Gas Tracer Dispersion

The Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The first method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model’s Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.

A source term estimation method for a nuclear accident using atmospheric dispersion models

The objective of this study is to develop an operational source term estimation (STE) method applicable for a nuclear accident like the incident that occurred at the Fukushima Dai-ichi nuclear power station in 2011. The new STE method presented here is based on data from atmospheric dispersion models and short-range observational data around the nuclear power plants. The accuracy of this method is validated with data from a wind tunnel study that involved a tracer gas release from a scaled model experiment at Tokai Daini nuclear power station in Japan. We then use the methodology developed and validated through the effort described in this manuscript to estimate the release rate of radioactive material from the Fukushima Dai-ichi nuclear power station.

The Effect of Topographic Variability on Initial Condition Sensitivity of Low-Level Wind Forecasts. Part II: Experiments Using Real Terrain and Observations

AbstractA study by Bieringer et al., which is Part I of this two-part study, demonstrated analytically using the shallow-water equations and numerically in controlled experiments that the presence of terrain can result in an enhancement of sensitivities to initial condition adjustments. The increased impact of adjustments to initial conditions corresponds with gradients in the flow field induced by the presence of the terrain obstacle. In cross-barrier flow situations the impact of the initial condition adjustments on the final forecast increases linearly as the height of the terrain obstacle increases. While this property associated with initial condition perturbations may be present in an analytic and controlled numerical environment, it is often difficult to realize these benefits in a more operationally realistic setting. This study extends the prior work to a situation with actual terrain, Doppler radar wind observations over the terrain, and observations from a surface mesonet for model verification...

The Effect of Topographic Variability on Initial Condition Sensitivity of Low-Level Wind Forecasts. Part I: Experiments Using Idealized Terrain

AbstractThe concept of improving the accuracy of numerical weather forecasts by targeting additional meteorological observations in areas where the initial condition error is suspected to grow rapidly has been the topic of numerous studies and field programs. The challenge faced by this approach is that it typically requires a costly observation system that can be quickly adapted to place instrumentation where needed. The present study examines whether the underlying terrain in a mesoscale model influences model initial condition sensitivity and if knowledge of the terrain and corresponding predominant flow patterns for a region can be used to direct the placement of instrumentation. This follows the same concept on which earlier targeted observation approaches were based, but eliminates the need for an observation system that needs to be continually reconfigured. Simulations from the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) a...

Method for Comparison of Large Eddy Simulation- Generated Wind Fluctuations with Short-Range Observations

The often prohibitive costs of comprehensive field trials coupled with relatively cheap and abundant computational power leads to a strong desire to use modelling tools to supplement field testing of system components. These modelling tools must be capable of reproducing key environmental variables present during field testing and require rigorous validation. The Virtual THreat Response Emulation and Analysis Testbed (VTHREAT) modelling system is composed of a suite of models designed to provide a virtual Chemical, Biological, Radiological and Nuclear (CBRN) release environment. Two key variables that VTHREAT is designed to realistically simulate are agent concentration and wind velocity. Typical validation studies compare mean predicted and observed quantities of interest such as mean concentration and mean wind speed and direction. This paper attempts to develop techniques to evaluate fluctuations – in particular, two-dimensional wind vector fluctuations.

Simulation of Airborne Transport and Dispersion for Urban Waterside Releases

AbstractResults are presented from a tracer-release modeling study designed to examine atmospheric transport and dispersion (“T&D”) behavior surrounding the complex coastal–urban region of New York City, New York, where air–sea interaction and urban influences are prominent. The puff-based Hazard Prediction Assessment Capability (HPAC, version 5) model is run for idealized conditions, and it is also linked with the urbanized COAMPS (1 km) meteorological model and the NAM (12 km) meteorological model. Results are compared with “control” plumes utilizing surface meteorological input from 22 weather stations. In all configurations, nighttime conditions result in plume predictions that are more sensitive to small changes in wind direction. Plume overlap is reduced by up to 70% when plumes are transported during the night. An analysis of vertical plume cross sections and the nature of the underlying transport and the dispersion equations both suggest that heat flux gradients and boundary layer height gradients...