Melt pond depth retrieval applying airborne spectral imaging and the potential of a new RGB band approach

Melt ponds are important features on summer Arctic sea ice leading to a surface albedo reduction and thereby altering the energy budget. Besides the spatial pond coverage, the melt pond depth is of importance in context of meltwater volume distribution across the sea ice surface. In this study, the melt pond depth is retrieved based on airborne reflectance measurements performed in the framework of an Arctic field campaign. An already existing approach uses the spectral reflectance slope and is widely independent of the pond ice bottom reflectance contribution. However, the surface coverage of the imaging spectrometer, providing the required spectrally resolved information, is limited due to the narrow field of view. To capture a larger number of melt ponds, a commercial digital camera with fisheye-lens provides reflectances in the red, green, and blue (RGB) spectral ranges. To retrieve the melt pond depth a new RGB band approach was developed and validated by the established spectral retrieval approach. The depth deviation of the approaches ranged between 0.1 cm and 27.6 cm depending on prior information on the pond ice bottom reflectance.Schmelztümpel stellen wichtige Oberflächenmerkmale des arktischen Meereises im Sommer dar, da sie die Albedo senken und somit Einfluss auf das Energiebudget haben. Neben der Fläche, die die Tümpel bedecken, ist ebenfalls deren Tiefe im Rahmen der Schmelzwasserverteilung relevant. In dieser Studie wird die Schmelztümpeltiefe von flugzeuggetragenen Reflektanzmessungen abgeleitet, die während einer Messkampagne in der Arktis durchgeführt wurden. Ein bereits bestehender Ansatz verwendet den spektralen Reflektanzanstieg und ist weitgehend unabhängig von der Reflexion am Eisboden des Tümpels. Jedoch ist die räumliche Abdeckung des bildgebenden Spektrometers, das spektral aufgelöste Messungen ermöglicht, durch den schmalen Öffnungswinkel des Instruments limitiert. Um eine größere Anzahl von Tümpeln zu beobachten, kann eine kommerzielle Digitalkamera mit Fischaugenlinse verwendet werden, mit welcher Reflektanzen im roten, grünen und blauen (RGB) Spektralbereich bestimmt werden können. Um die Tümpeltiefe abzuleiten, wurde ein neuer RGB Ansatz entwickelt und mit dem bestehenden spektralen Ansatz validiert. Die Abweichungen der abgeleiteten Tiefen variierten zwischen 0.1 cm und 27.6 cm abhängig von den bereitgestellten Informationen zur Reflektanz des Eises am Tümpelboden

Global Roughness Texture of the Moon and Mars

Statistical measures of patterns (textures) in surface roughness are used to quantitatively differentiate regional geomorphic units on the Moon and Mars (e.g. cratered highlands, volcanic terrains and planar lowlands). The existence of vastly distinct crustal types on Mars and the Moon is well established [e.g. 1, 2, 3, & 4]. Here, a new methodology developed for differentiating terrestrial volcanic deposits using ~1 m resolution topography data [5], is tested on two global data sets where roughness pixels are much larger (1/4 of a degree)

Observations on the American White Pelican

This is where the abstract of this record would appear. This is only demonstration data

International collaboration to enhance the fight against HIV/AIDS: Report of a consultative meeting between the University of Buea in Cameroon and the Goldfarb School of Nursing in the USA

HIV/AIDS is a major public health pandemic affecting the development, survival and life of young people both in Cameroon and the USA. Youths are more adaptive to change and less hindered by prejudice than adults. Student-to-student peer mentoring is a non-formal way for students to learn new life skills and different cross-cultural values. We report on a two-day consultative meeting on developing international collaboration for the fight against HIV/AIDS between Cameroonian and USA nursing students. We used adult learning approaches consisting of presentations, discussions, questions and answer sessions, role plays and demonstrations. Deliberations and resolutions from the consultative meeting enabled the Vice-Chancellor of the University of Buea to sign a memorandum of understanding with the Goldfarb School of Nursing in the USA on HIV/AIDS international collaboration paving the way forward for more developmental health projects in this domain

Measurements and modeling of optical-equivalent snow grain sizes under arctic low-sun conditions

The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (r$_{opt}$) or, alternatively, the specific surface area (SSA) using satellite, airborne, and ground-based observations are compared and used to evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols and Reactive Trace gases) simulations. The retrieval methods are based on optical measurements and rely on the r$_{opt}$-dependent absorption of solar radiation in snow. The measurement data were taken during a three-week campaign that was conducted in the North of Greenland in March/April 2018, such that the retrieval methods and radiation measurements are affected by enhanced uncertainties under these low-Sun conditions. An adjusted airborne retrieval method is applied which uses the albedo at 1700 nm wavelength and combines an atmospheric and snow radiative transfer model to account for the direct-to-global fraction of the solar radiation incident on the snow. From this approach, we achieved a significantly improved uncertainty (<25%) and a reduced effect of atmospheric masking compared to the previous method. Ground-based in situ measurements indicated an increase of r$_{opt}$ of 15 µm within a five-day period after a snowfall event which is small compared to previous observations under similar temperature regimes. ICON-ART captured the observed change of r$_{opt}$ during snowfall events, but systematically overestimated the subsequent snow grain growth by about 100%. Adjusting the growth rate factor to 0.012 µm$^{2}$ s$^{-1}$ minimized the difference between model and observations. Satellite-based and airborne retrieval methods showed higher r$_{opt}$ over sea ice (<300 µm) than over land surfaces (<100 µm) which was reduced by data filtering of surface roughness features. Moderate-Resolution Imaging Spectroradiometer (MODIS) retrievals revealed a large spread within a series of subsequent individual overpasses, indicating their limitations in observing the snow grain size evolution in early spring conditions with low Sun

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact

Contribution of spores to the ability of Clostridium difficile to adhere to surfaces.

Clostridium difficile is the commonest cause of hospital-acquired infection in the United Kingdom. We characterized the abilities of 21 clinical isolates to form spores; to adhere to inorganic and organic surfaces, including stainless steel and human adenocarcinoma cells; and to germinate. The composition of culture media had a significant effect on spore formation, as significantly more spores were produced in brain heart infusion broth (Student's t test; P = 0.018). The spore surface relative hydrophobicity (RH) varied markedly (14 to 77%) and was correlated with the ability to adhere to stainless steel. We observed no correlation between the ribotype and the ability to adhere to steel. When the binding of hydrophobic (DS1813; ribotype 027; RH, 77%) and hydrophilic (DS1748; ribotype 002; RH, 14%) spores to human gut epithelial cells at different stages of cell development was examined, DS1813 spores adhered more strongly, suggesting the presence of surface properties that aid attachment to human cells. Electron microscopy studies revealed the presence of an exosporium surrounding DS1813 spores that was absent from spores of DS1748. Finally, the ability of spores to germinate was found to be strain and medium dependent. While the significance of these findings to the disease process has yet to be determined, this study has highlighted the importance of analyzing multiple isolates when attempting to characterize the behavior of a bacterial species