Allison Singley, Director of Parent Relations

In our new Next Page column, Allison Singley, Director of Parent Relations, shares with us the three books she is currently reading and why it might take her a while to finish them, her two desert island books (one of which inspired her doctoral dissertation), how she maintains a habit of reading poetry daily, and why she doesn’t write in books anymore — or feel the need to finish one

A new satellite-based global climatology of dust aerosol optical depth

By mass, dust is the largest contributor to global aerosol burden, yet long-term observational records of dust, particularly over the ocean, are limited. Here, two nearly global observational datasets of dust aerosol optical depth τd are created primarily on the basis of optical measurements of the aerosol column from 1) the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite spanning from 2001 to 2018 and 2) the Advanced Very High Resolution Radiometer (AVHRR) from 1981 to 2018. The quality of the new data is assessed by comparison with existing dust datasets that are spatially more limited. Between 2001 and 2018, τd decreased over Asia and increased significantly over the Sahara, Middle East, and parts of eastern Europe, with the largest increase found over the Aral Sea where emissive playa surfaces have been exposed. These daily, observational, and nearly global records of dust will allow for improvement in understanding the role of dust in climate variability

El Roque de Los Muchachos Site Characteristics. III. Analysis of Atmospheric Dust and Aerosol Extinction

Canary Islands are normally interested by dominant North-East winds that, in some meteorological conditions, can transport sand at high altitude from the Sahara desert. The dust may affect the efficiency of the telescopes and decreases the transparency of the sky. In order to maximize the scientific return of the telescopes located at the ORM, we present an analysis of the atmospheric dust content and its effects on astronomical observations. B, V and I dust aerosol astronomical extinction are derived. Using a 5 years series database of data taken from the four channel TNG dust monitor, we compute a mean hourly and daily values of the dust content. We have detected particles having size 0.3, 0.5, 1.0 and 5.0 um. Using a power law we have derived the content of 10.0 um particles. We found a typical local dust concentration ranging from 3x10^6 particles per cubic meter at 0.3 um, to 10^3 at 5.0 um and 10 at 10.0 um, increasing up to 3 order of magnitudes during the dust storms, with a relative higher increase of 1.0, 5.0 and 10.0 um particles. The number of local dust storm events is the same in winter- and summertime, but, the average background and storm-related increases in the dust concentration in summer are significantly higher than in winter. In a uniform approximation, during the dust storms, an average height of the dust layer of 2.5 km above the telescope is inferred. During the sand storms La Palma Island is affected by an almost uniform layer extending up to 5 km above the sea level, down, at least the height of the telescope. The visible extinction is dominated by particles at 1.0, 5.0 and 10.0 um. In agreement with the results from Carlsberg Automatic Meridian Circle (CAMC) we find a typical extinction during dust storms of about 0.2 mag/airmass.Comment: Accepted for publication in A&A. 9 pages, 11 figures. This work is the continuation of a series of papers concerning a detailed study of the Astroclimatology at ORM. The two previous papers (both Lombardi et al.) have reference PASP.2006.118.1198-1204 and PASP.2007.119.292-30

Solving the mystery of booming sand dunes

Desert booming can be heard after a natural slumping event or during a sand avalanche generated by humans sliding down the slip face of a large dune. The sound is remarkable because it is composed of one dominant audible frequency (70 to 105 Hz) plus several higher harmonics. This study challenges earlier reports that the dunes’ frequency is a function of average grain size by demonstrating through extensive field measurements that the booming frequency results from a natural waveguide associated with the dune. The booming frequency is fixed by the depth of the surficial layer of dry loose sand that is sandwiched between two regions of higher compressional body wave velocity. This letter presents measurements of the booming frequencies, compressional wave velocities, depth of surficial layer, along with an analytical prediction of the frequency based on constructive interference of propagating waves generated by avalanching along the dune surface

Amphibians and Reptiles of United States Department of Defense Installations

The U.S. Department of Defense (DoD) occupies approximately 10.1 million ha of land within the U.S. spanning most ecosystems contained therein. To date, no comprehensive agency-wide inventory of amphibian and reptile species has been compiled. We developed an amphibian and reptile species inventory for 415 DoD installations/sites and evaluated species diversity. The amphibian and reptile species confirmed present on DoD sites represent 66% of the total native species documented in the continental U.S. Snakes are the most widespread group found on DoD lands. Of the military services, Army sites have the greatest number of confirmed species, federally listed, state-listed, and At-risk species. There are 24 federally listed (threatened or endangered), 55 state- listed, and 70 At-risk species confirmed present on DoD sites. Thirty non-native and native transplant amphibian and reptile species/subspecies are also confirmed present on DoD sites. Lastly, we verified that approximately half of the military sites evaluated in this study have at least one venomous snake species confirmed present. Our study results assist directly with ongoing management and conservation of amphibian and reptile species on DoD lands and confirm military lands comprise a significant contribution to biodiversity conservation

Atmospheric Water Soluble Organic Nitrogen (WSON) over marine environments: A global perspective

To obtain a comprehensive picture of the spatial distribution of water-soluble organic nitrogen (WSON) in marine aerosols, samples were collected during research cruises in the tropical and southern Atlantic Ocean and also in the southern Indian Ocean (Amsterdam Island) for a 1-year period (2005). Samples were analyzed for both organic and inorganic forms of nitrogen, and the factors controlling their levels were examined. Fine-mode WSON was found to play a significant role in the remote marine atmosphere with enhanced biogenic activity, with concentrations of WSON (11.3 +/- 3.3 nmol N m(-3)) accounting for about 84% of the total dissolved nitrogen (TDN). Such concentrations are similar to those observed in the polluted marine atmosphere of the eastern Mediterranean (11.6 +/- 14.0 nmol N m(-3)). Anthropogenic activities were found to be an important source of atmospheric WSON as evidenced by the levels in the Northern Hemisphere (NH) being 10 times higher than in the remote Southern Hemisphere (SH). Furthermore, the higher contribution of fine-mode WSON to TDN (51 %) in the SH, compared to the NH (13 %), underlines the important role of organic nitrogen in remote marine areas. Finally, there was a strong association of WSON with dust in coarse-mode aerosols in the NH

Cryptic photosynthesis, Extrasolar planetary oxygen without a surface biological signature

On the Earth, photosynthetic organisms are responsible for the production of virtually all of the oxygen in the atmosphere. On the land, vegetation reflects in the visible, leading to a red edge that developed about 450 Myr ago and has been proposed as a biosignature for life on extrasolar planets. However, in many regions of the Earth, and particularly where surface conditions are extreme, for example in hot and cold deserts, photosynthetic organisms can be driven into and under substrates where light is still sufficient for photosynthesis. These communities exhibit no detectable surface spectral signature to indicate life. The same is true of the assemblages of photosynthetic organisms at more than a few metres depth in water bodies. These communities are widespread and dominate local photosynthetic productivity. We review known cryptic photosynthetic communities and their productivity. We link geomicrobiology with observational astronomy by calculating the disk-averaged spectra of cryptic habitats and identifying detectable features on an exoplanet dominated by such a biota. The hypothetical cryptic photosynthesis worlds discussed here are Earth-analogs that show detectable atmospheric biomarkers like our own planet, but do not exhibit a discernable biological surface feature in the disc-averaged spectrum.Comment: 23 pages, 2 figures, Astrobiology (TBP) - updated Table 1, typo in detectable O2 correcte

Historical Patterns of Arboviral Seroprevalence across Africa and Asia

The emergence and resurgence of arboviruses in recent history is challenging our scientific understanding of mosquito-borne diseases and their transmission. To better contextualize recent epidemics and gain insight into historical trends in arbovirus incidence, we conducted a literature review to identify serosurveys from Africa and Asia. We compiled all serosurvey data into a table and tested for variation in disease incidence across countries and between age categories. Our analysis showed that disease incidence was consistently higher in the \u3e15 age category than the \u3c15 age category and revealed significant variation in incidence across countries. In addition, the mean incidence of yellow fever virus was substantially higher than the incidences of the other diseases included in the analysis. Higher incidence in the \u3e15 age category is likely due to the long-term persistence of antibodies in human sera, while a higher incidence of yellow fever can likely be attributed to widespread vaccine use. Characteristics of countries with high disease incidence included a tropical climate, extended rainy season, and flat terrain, and countries with low disease incidence occurred at higher elevations and/or reflected a desert climate. This analysis can hopefully reveal the conditions most important in facilitating an arbovirus outbreak, leading to targeted prevention strategies in high-risk areas. It also highlights the need for continued serosurveys as a method of documenting disease spread