Daniel F. Steinhoff

The Dengue Virus Mosquito Vector Aedes aegypti at High Elevation in México

México has cities (e.g., México City and Puebla City) located at elevations > 2,000 m and above the elevation ceiling below which local climates allow the dengue virus mosquito vector Aedes aegypti to proliferate. Climate warming could raise this ceiling and place high-elevation cities at risk for dengue virus transmission. To assess the elevation ceiling for Ae. aegypti and determine the potential for using weather/climate parameters to predict mosquito abundance, we surveyed 12 communities along an elevation/climate gradient from Veracruz City (sea level) to Puebla City (∼2,100 m). Ae. aegypti was commonly encountered up to 1,700 m and present but rare from 1,700 to 2,130 m. This finding extends the known elevation range in México by > 300 m. Mosquito abundance was correlated with weather parameters, including temperature indices. Potential larval development sites were abundant in Puebla City and other high-elevation communities, suggesting that Ae. aegypti could proliferate should the climate become warmer.

On the Seasonal Occurrence and Abundance of the Zika Virus Vector Mosquito Aedes Aegypti in the Contiguous United States.

Introduction: An ongoing Zika virus pandemic in Latin America and the Caribbean has raised concerns that travel-related introduction of Zika virus could initiate local transmission in the United States (U.S.) by its primary vector, the mosquito Aedes aegypti. Methods: We employed meteorologically driven models for 2006-2015 to simulate the potential seasonal abundance of adult Aedes aegypti for fifty cities within or near the margins of its known U.S. range. Mosquito abundance results were analyzed alongside travel and socioeconomic factors that are proxies of viral introduction and vulnerability to human-vector contact. Results: Meteorological conditions are largely unsuitable for Aedes aegypti over the U.S. during winter months (December-March), except in southern Florida and south Texas where comparatively warm conditions can sustain low-to-moderate potential mosquito abundance. Meteorological conditions are suitable for Aedes aegypti across all fifty cities during peak summer months (July-September), though the mosquito has not been documented in all cities. Simulations indicate the highest mosquito abundance occurs in the Southeast and south Texas where locally acquired cases of Aedes-transmitted viruses have been reported previously. Cities in southern Florida and south Texas are at the nexus of high seasonal suitability for Aedes aegypti and strong potential for travel-related virus introduction. Higher poverty rates in cities along the U.S.-Mexico border may correlate with factors that increase human exposure to Aedes aegypti. Discussion: Our results can inform baseline risk for local Zika virus transmission in the U.S. and the optimal timing of vector control activities, and underscore the need for enhanced surveillance for Aedes mosquitoes and Aedes-transmitted viruses.

Foehn Winds in the McMurdo Dry Valleys, Antarctica: The Origin of Extreme Warming Events

Foehn winds are warm, dry and gusty downslope winds resulting from the topographic modification of the airstream in the lee of mountain barriers. They are a climatological feature common to many of the world’s mountainous regions, however, detailed investigations into foehn winds in polar regions and their effects on environmental processes are rare. In the McMurdo Dry Valleys (MDVs) of Antarctica, frequent episodes of strong foehn winds are experienced. Here they cause dramatic warming at onset and are suspected to significantly affect landscape forming processes, however, no detailed scientific investigation of foehn in the MDVs has been conducted. As a result, they are often misinterpreted as adiabatically warmed katabatic winds draining from the Polar Plateau. This thesis integrates observations from surface weather stations, numerical model output from the Antarctic Mesoscale Prediction System (AMPS), hydrological data and remote sensing techniques to understand the dynamics and influences of foehn wind events in the MDVs. Results show that foehn winds in the MDVs are caused by topographic modification of south-southwesterly airflow which is channelled into the valleys from higher levels. Modelling of a winter foehn event identifies mountain wave activity similar to that associated with mid-latitude foehn winds. These events are found to be caused by strong pressure gradients over the mountain ranges of the MDVs related to synoptic-scale cyclones positioned in the Amundsen/Ross Sea region. Importantly, these results clarify that a foehn mechanism is responsible for the strong warm wind events in the MDVs and that the influence of katabatic surges from the Polar Plateau as an origin or triggering mechanism of events is minimal. A 20-year climatology of foehn winds is presented from observational records in the MDVs. The intra- and inter-annual frequency and intensity of foehn events varies in response to the position and frequency of cyclones in this region. These cyclones are well known to be influenced by the El Nino Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Statistically significant relationships are found between the SAM and foehn wind frequency during the Antarctic summer and autumn months whereas ENSO only holds significant correlations with winter air temperatures in the MDVs. Foehn winds are a major climatological feature of the MDVs with their frequency and duration affecting the region’s temperature records and their trends. Accordingly, analysis of the region’s weather and climate records and predictions of future impacts of climate change on the MDVs is incomplete without consideration of foehn winds and their influence. In the past, the influence of foehn wind events on landscape processes of this polar desert has not been well understood. Hydrological data and remote sensing techniques are used to quantify the influence of foehn winds on environmental processes in the MDVs. Foehn winds frequently cause summer temperatures to rise above 0°C leading to extensive melt and thaw in the MDVs. Sublimation, stream discharge and snow persistence are shown to be significantly influenced by foehn winds and the effects of foehn are demonstrated to outlive the duration of the event. It is concluded that foehn winds in the MDVs are the major cause of contemporary landscape change. Future changes in the MDVs landscape may be linked to variability in teleconnections (e.g., SAM and ENSO) and their influence on synoptic circulation patterns that drive cyclone activity in the Ross Sea region and the foehn wind regime.

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.

A Case Study of a Ross Ice Shelf Airstream Event: A New Perspective*

Abstract A case study illustrating cloud processes and other features associated with the Ross Ice Shelf airstream (RAS), in Antarctica, is presented. The RAS is a semipermanent low-level wind regime primarily over the western Ross Ice Shelf, linked to the midlatitude circulation and formed from terrain-induced and large-scale forcing effects. An integrated approach utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery, automatic weather station (AWS) data, and Antarctic Mesoscale Prediction System (AMPS) forecast output to study the synoptic-scale and mesoscale phenomena involved in cloud formation over the Ross Ice Shelf during a RAS event. A synoptic-scale cyclone offshore of Marie Byrd Land draws moisture across West Antarctica to the southern base of the Ross Ice Shelf. Vertical lifting associated with flow around the Queen Maud Mountains leads to cloud formation that extends across the Ross Ice Shelf to the north. The low-level cloud has a warm signature in thermal infrare...

A Dynamical Investigation of the May 2004 McMurdo Antarctica Severe Wind Event Using AMPS

On 15–16 May 2004 a severe windstorm struck McMurdo, Antarctica. The Antarctic Mesoscale Prediction System (AMPS) is used, along with available observations, to analyze the storm. A synoptic-scale cyclone weakens as it propagates across the Ross Ice Shelf toward McMurdo. Flow associated with the cyclone initiates a barrier jet along the Transantarctic Mountains. Forcing terms from the horizontal equations of motion are computed in the barrier wind to show that the local time tendency and momentum advection terms are key components of the force balance. The barrier jet interacts with a preexisting near-surface radiation inversion over the Ross Ice Shelf to set up conditions favorable for the development of large-amplitude mountain waves, leading to a downslope windstorm in the Ross Island area. Hydraulic theory can explain the structure of the downslope windstorms, with amplification of the mountain waves possibly caused by wave-breaking events. The underestimation of AMPS wind speed at McMurdo is caused by the misplacement of a hydraulic jump downstream of the downslope windstorms. The dynamics associated with the cyclone, barrier jet, and downslope windstorms are analyzed to determine the role of each in development of the severe winds.

Projected impact of twenty-first century ENSO changes on rainfall over Central America and northwest South America from CMIP5 AOGCMs

Due to the importance that the El Niño-Southern Oscillation (ENSO) has on rainfall over the tropical Americas, future changes in ENSO characteristics and teleconnections are important for regional hydroclimate. Projected changes to the ENSO mean state and characteristics, and the resulting impacts on rainfall anomalies over Central America, Colombia, and Ecuador during the twenty-first century are explored for several forcing scenarios using a suite of coupled atmosphere–ocean global climate models (AOGCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Mean-state warming of eastern tropical Pacific sea surface temperatures, drying of Central America and northern Colombia, and wetting of southwest Colombia and Ecuador are consistent with previous studies that used earlier versions of the AOGCMs. Current and projected future characteristics of ENSO (frequency, duration, amplitude) show a wide range of values across the various AOGCMs. The magnitude of ENSO-related rainfall anomalies are currently underestimated by most of the models, but the model ensembles generally simulate the correct sign of the anomalies across the seasons around the peak ENSO effects. While the models capture the broad present-day ENSO-related rainfall anomalies, there is not a clear sense of projected future changes in the precipitation anomalies.

Research on Emissions, Air quality, Climate, and Cooking Technologies in Northern Ghana (REACCTING): study rationale and protocol

BackgroundCooking over open fires using solid fuels is both common practice throughout much of the world and widely recognized to contribute to human health, environmental, and social problems. The public health burden of household air pollution includes an estimated four million premature deaths each year. To be effective and generate useful insight into potential solutions, cookstove intervention studies must select cooking technologies that are appropriate for local socioeconomic conditions and cooking culture, and include interdisciplinary measurement strategies along a continuum of outcomes.Methods/DesignREACCTING (Research on Emissions, Air quality, Climate, and Cooking Technologies in Northern Ghana) is an ongoing interdisciplinary randomized cookstove intervention study in the Kassena-Nankana District of Northern Ghana. The study tests two types of biomass burning stoves that have the potential to meet local cooking needs and represent different “rungs” in the cookstove technology ladder: a locally-made low-tech rocket stove and the imported, highly efficient Philips gasifier stove. Intervention households were randomized into four different groups, three of which received different combinations of two improved stoves, while the fourth group serves as a control for the duration of the study. Diverse measurements assess different points along the causal chain linking the intervention to final outcomes of interest. We assess stove use and cooking behavior, cooking emissions, household air pollution and personal exposure, health burden, and local to regional air quality. Integrated analysis and modeling will tackle a range of interdisciplinary science questions, including examining ambient exposures among the regional population, assessing how those exposures might change with different technologies and behaviors, and estimating the comparative impact of local behavior and technological changes versus regional climate variability and change on local air quality and health outcomes.DiscussionREACCTING is well-poised to generate useful data on the impact of a cookstove intervention on a wide range of outcomes. By comparing different technologies side by side and employing an interdisciplinary approach to study this issue from multiple perspectives, this study may help to inform future efforts to improve health and quality of life for populations currently relying on open fires for their cooking needs.

The Impact of Climate Change on Meningitis in Northwest Nigeria: An Assessment Using CMIP5 Climate Model Simulations

AbstractMeningitis remains a major health burden throughout Sahelian Africa, especially in heavily populated northwest Nigeria with an annual incidence rate ranging from 18 to 200 per 100 000 people for 2000–11. Several studies have established that cases exhibit sensitivity to intra- and interannual climate variability, peaking during the hot and dry boreal spring months, raising concern that future climate change may increase the incidence of meningitis in the region. The impact of future climate change on meningitis risk in northwest Nigeria is assessed by forcing an empirical model of meningitis with monthly simulations of seven meteorological variables from an ensemble of 13 statistically downscaled global climate model projections from phase 5 of the Coupled Model Intercomparison Experiment (CMIP5) for representative concentration pathway (RCP) 2.6, 6.0, and 8.5 scenarios, with the numbers representing the globally averaged top-of-the-atmosphere radiative imbalance (in W m−2) in 2100. The results su...

Intra-Annual Changes in Abundance of Aedes (Stegomyia) aegypti and Aedes (Ochlerotatus) epactius (Diptera: Culicidae) in High-Elevation Communities in México

ABSTRACT We examined temporal changes in the abundance of the mosquitoes Aedes (Stegomyia) aegypti (L.) and Aedes (Ochlerotatus) epactius Dyar & Knab from June to October 2012 in one reference community at lower elevation (Rio Blanco; ≈1,270 m) and three high-elevation communities (Acultzingo, Maltrata, and Puebla City; 1,670–2,150 m) in Veracruz and Puebla States, México. The combination of surveys for pupae in water-filled containers and trapping of adults, using BG-Sentinel traps baited with the BG-Lure, corroborated previous data from 2011 showing that Ae. aegypti is present at low abundance up to 2,150 m in this part of México. Data for Ae. aegypti adults captured through repeated trapping in fixed sites in Acultzingo—the highest elevation community (≈1,670 m) from which the temporal intra-annual abundance pattern for Ae. aegypti has been described—showed a gradual increase from low numbers in June to a peak occurrence in late August, and thereafter declining numbers in September. Ae. epactius adults were collected repeatedly in BG-Sentinel traps in all four study communities; this is the first recorded collection of this species with a trap aiming specifically to collect human-biting mosquitoes. We also present the first description of the temporal abundance pattern for Ae. epactius across an elevation gradient: peak abundance was reached in mid-July in the lowest elevation community (Rio Blanco) but not until mid-September in the highest elevation one (Puebla City). Finally, we present data for meteorological conditions (mean temperature and rainfall) in the examined communities during the study period, and for a cumulative measure of the abundance of adults over the full sampling period.