A 2D Microphysical Analysis of Aerosol Nucleation in the Polar Winter Stratosphere: Implications for H2SO4 Photolysis and Nucleation Mechanisms

Each spring a layer of small particles forms between 20 and 30 km in the polar regions. Results are presented from a 2D microphysical model of sulfate aerosol, which provide the first self-consistent explanation of the observed "CN layer." Photochemical conversion of sulfuric acid to SO2 in the upper stratosphere and mesosphere is necessary for this layer to form. Recent laboratory measurements of H2SO4 and SO3 photolysis rates are consistent with such conversion, though an additional source of SO2 may be required. Nucleation throughout the polar winter extends the top of the aerosol layer to higher altitudes, despite strong downward transport of ambient air. This finding may be important to heterogeneous chemistry at the top of the aerosol layer in polar winter and spring

Spatial confidentiality and GIS: re-engineering mortality locations from published maps about Hurricane Katrina

BACKGROUND: Geographic Information Systems (GIS) can provide valuable insight into patterns of human activity. Online spatial display applications, such as Google Earth, can democratise this information by disseminating it to the general public. Although this is a generally positive advance for society, there is a legitimate concern involving the disclosure of confidential information through spatial display. Although guidelines exist for aggregated data, little has been written concerning the display of point level information. The concern is that a map containing points representing cases of cancer or an infectious disease, could be re-engineered back to identify an actual residence. This risk is investigated using point mortality locations from Hurricane Katrina re-engineered from a map published in the Baton Rouge Advocate newspaper, and a field team validating these residences using search and rescue building markings. RESULTS: We show that the residence of an individual, visualized as a generalized point covering approximately one and half city blocks on a map, can be re-engineered back to identify the actual house location, or at least a close neighbour, even if the map contains little spatial reference information. The degree of re-engineering success is also shown to depend on the urban characteristic of the neighborhood. CONCLUSION: The results in this paper suggest a need to re-evaluate current guidelines for the display of point (address level) data. Examples of other point maps displaying health data extracted from the academic literature are presented where a similar re-engineering approach might cause concern with respect to violating confidentiality. More research is also needed into the role urban structure plays in the accuracy of re-engineering. We suggest that health and spatial scientists should be proactive and suggest a series of point level spatial confidentiality guidelines before governmental decisions are made which may be reactionary toward the threat of revealing confidential information, thereby imposing draconian limits on research using a GIS

The potential impacts of a sulfur- and halogen-rich supereruption such as Los Chocoyos on the atmosphere and climate

The supereruption of Los Chocoyos (14.6°N, 91.2°W) in Guatemala ∼84kyr ago was one of the largest volcanic events of the past 100000 years. Recent petrologic data show that the eruption released very large amounts of climate-relevant sulfur and ozone-destroying chlorine and bromine gases (523±94Mt sulfur, 1200±156Mt chlorine, and 2±0.46Mt bromine). Using the Earth system model (ESM) of the Community Earth System Model version 2 (CESM2) coupled with the Whole Atmosphere Community Climate Model version 6 (WACCM6), we simulated the impacts of the sulfur- and halogen-rich Los Chocoyos eruption on the preindustrial Earth system. Our simulations show that elevated sulfate burden and aerosol optical depth (AOD) persists for 5 years in the model, while the volcanic halogens stay elevated for nearly 15 years. As a consequence, the eruption leads to a collapse of the ozone layer with global mean column ozone values dropping to 50DU (80% decrease) and leading to a 550% increase in surface UV over the first 5 years, with potential impacts on the biosphere. The volcanic eruption shows an asymmetric-hemispheric response with enhanced aerosol, ozone, UV, and climate signals over the Northern Hemisphere. Surface climate is impacted globally due to peak AOD of >6, which leads to a maximum surface cooling of >6K, precipitation and terrestrial net primary production decrease of >25%, and sea ice area increases of 40% in the first 3 years. Locally, a wetting (>100%) and strong increase in net primary production (NPP) (>700%) over northern Africa is simulated in the first 5 years and related to a southward shift of the Intertropical Convergence Zone (ITCZ) to the southern tropics. The ocean responds with pronounced El Niño conditions in the first 3 years that shift to the southern tropics and are coherent with the ITCZ change. Recovery to pre-eruption ozone levels and climate takes 15 years and 30 years, respectively. The long-lasting surface cooling is sustained by an immediate increase in the Arctic sea ice area, followed by a decrease in poleward ocean heat transport at 60°N which lasts up to 20 years. In contrast, when simulating Los Chocoyos conventionally by including sulfur and neglecting halogens, we simulate a larger sulfate burden and AOD, more pronounced surface climate changes, and an increase in column ozone. By comparing our aerosol chemistry ESM results to other supereruption simulations with aerosol climate models, we find a higher surface climate impact per injected sulfur amount than previous studies for our different sets of model experiments, since the CESM2(WACCM6) creates smaller aerosols with a longer lifetime, partly due to the interactive aerosol chemistry. As the model uncertainties for the climate response to supereruptions are very large, observational evidence from paleo archives and a coordinated model intercomparison would help to improve our understanding of the climate and environment response

Atmospheric oxidation chemistry and ozone production: Results from SHARP 2009 in Houston, Texas

This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies

A review of cricket fielding requirements

Cricket is played in three formats at elite level: Test, One Day and Twenty20. Fielding is an important component of cricket, as all players are obliged to field. However, there is a paucity of literature on fielding compared with that on batting and bowling. We review the available literature in terms of technical, mental, physiological and physical factors important to fielding, to identify knowledge gaps and better understand the performance requirements of fielding in cricket