Isokinetic total water content probe in a naturally aspirating configuration: initial aerodynamic design and testing

Recent measurements in wind tunnel and flight experiments have demonstrated that water loss prior to complete evaporation is possible for the hot-wire total water content probes. Other cloud water content probes similarly have their own operating problems. To enhance the efficiency of water particle capture and water mass retention, isokinetic sampling is appealing. The probe described in this paper represents an extension of a concept that was developed and tested through the then RAE Farnborough, UK. The intention is to quantify and minimize possible departures from isokinetic sampling during operation - something that is difficult to achieve in the original RAE configuration. This paper describes the design methodologies and the experiments that have been performed to characterize the aerodynamic performance of the prototype

In-situ observations of volcanic ash clouds from the FAAM aircraft during the eruption of Eyjafjallajökull in 2010

During April–May 2010 the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft flew 12 flights targeting volcanic ash clouds around the UK. The aircraft observed ash layers between altitudes of 2–8 km with peak mass concentrations typically between 200–2000 μg/m3, as estimated from a Cloud and Aerosol Spectrometer (CAS). A peak value of 2000–5000 μg/m3 was observed over Scotland on 14 May 2010, although with considerable uncertainty due to the possible contamination by ice. Aerosol size distributions within ash clouds showed a fine mode (0.1–0.6 μm) associated with sulphuric acid and/or sulphate, and a coarse mode (0.6–35 μm) associated with ash. The ash mass was dominated by particles in the size range 1–10 μm (volume-equivalent diameter), with a peak typically around 3–5 μm. Electron-microscope images and scattering patterns from the SID-2H (Small Ice Detector) probe showed the highly irregular shape of the ash particles. Ash clouds were also accompanied by elevated levels of SO2 (10–100 ppbv), strong aerosol scattering (50–500 × 10−6 m−1), and low Ångstrom exponents (−0.5 to 0.4) from the 3-wavelength nephelometer. Coarse-mode mass specific aerosol extinction coefficients (kext), based on the CAS size distribution varied from 0.45–1.06 m2/g. A representative value of 0.6 m2/g is suggested for distal ash clouds (∼1000 km downwind) from this eruption.Peer reviewe

Comparisons of Cloud In-Situ Microphysical Properties of Deep Convective Clouds to Appendix D/P, using Data from the HAIC-HIWC and HIWC RADAR I Flight Campaigns

International audienc

Why Are Daphnia in Some Lakes Sicker? Disease Ecology, Habitat Structure, and the Plankton

© 2010 American Institute of Biological Sciences. Permalink: http://www.bioone.org/doi/abs/10.1525/bio.2010.60.5.6DOI: 10.1525/bio.2010.60.5.6Some aspects of habitat seem to enhance the spread of disease whereas others inhibit it. Here, we illustrate and identify mechanisms that connect habitat to epidemiology using a case study of disease in plankton. We see a pronounced relationship between the basin shapes of lakes and fungal (Metschnikowia bicuspidata) disease in the zooplankton grazer Daphnia dentifera. As we work through seven mechanisms that could explain why Daphnia in some lakes are sicker, we can eliminate some hypotheses (i.e., those relating an index of lake productivity to disease through host density, links between resource quality and transmission rate, and variation in host susceptibility) and find support for others involving food-web actors (e.g., selective predation on infected hosts by fishes, “sloppy predation” by an invertebrate, a possible dilution effect in V-shaped lakes). Furthermore, we identify physical mechanisms (gravity currents, turbulence) that could lead to greater transport of fungal spores to habitat occupied by Daphnia hosts in U-shaped lakes. These results highlight how habitat structure, through its effects on food-web structure and physical processes, can shape wildlife disease