To help satellite retrieval of aerosols and studies of their radiative effects, we demonstrate that daytime aerosol optical depth over low-level clouds is similar to that in neighboring clear skies ...at the same heights. Based on recent airborne lidar and sun photometer observations above the southeast Atlantic, the mean aerosol optical depth (AOD) difference at 532 nm is between 0 and −0.01, when comparing the cloudy and clear sides, each up to 20 km wide, of cloud edges. The difference is not statistically significant according to a paired t test. Systematic differences in the wavelength dependence of AOD and in situ single scattering albedo are also minuscule. These results hold regardless of the vertical distance between cloud top and aerosol layer bottom. AOD aggregated over ∼2∘ grid boxes for each of September 2016, August 2017 and October 2018 also shows little correlation with the presence of low-level clouds. We posit that a satellite retrieval artifact is entirely responsible for a previous finding of generally smaller AOD over clouds (Chung et al., 2016), at least for the region and time of our study. Our results also suggest that the same values can be assumed for the intensive properties of free-tropospheric biomass-burning aerosol regardless of whether clouds are present below.
Aerosol heating due to shortwave absorption has implications for local atmospheric stability and regional dynamics. The derivation of heating rate profiles from space-based observations is ...challenging because it requires the vertical profile of relevant properties such as the aerosol extinction coefficient and single-scattering albedo (SSA). In the southeastern Atlantic, this challenge is amplified by the presence of stratocumulus clouds below the biomass burning plume advected from Africa, since the cloud properties affect the magnitude of the aerosol heating aloft, which may in turn lead to changes in the cloud properties and life cycle. The combination of spaceborne lidar data with passive imagers shows promise for future derivations of heating rate profiles and curtains, but new algorithms require careful testing with data from aircraft experiments where measurements of radiation, aerosol, and cloud parameters are better colocated and readily available.
Determining the direct aerosol radiative effect (DARE) of absorbing aerosols above clouds from satellite observations alone is a challenging task, in part because the radiative signal of the aerosol ...layer is not easily untangled from that of the clouds below. In this study, we use aircraft measurements from the NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) project in the southeastern Atlantic to derive it with as few assumptions as possible. This is accomplished by using spectral irradiance measurements (Solar Spectral Flux Radiometer, SSFR) and aerosol optical depth (AOD) retrievals (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research, 4STAR) during vertical profiles (spirals) that minimize the albedo variability of the underlying cloud field – thus isolating aerosol radiative effects from those of the cloud field below. For two representative cases, we retrieve spectral aerosol single scattering albedo (SSA) and the asymmetry parameter (g) from these profile measurements and calculate DARE given the albedo range measured by SSFR on horizontal legs above clouds. For mid-visible wavelengths, we find SSA values from 0.80 to 0.85 and a significant spectral dependence of g. As the cloud albedo increases, the aerosol increasingly warms the column. The transition from a cooling to a warming top-of-aerosol radiative effect occurs at an albedo value (critical albedo) just above 0.2 in the mid-visible wavelength range. In a companion paper, we use the techniques introduced here to generalize our findings to all 2016 and 2017 measurements and parameterize aerosol radiative effects.
In this paper, we use observations from the NASA ORACLES
(ObseRvations of CLouds above Aerosols and their intEractionS) aircraft
campaign to develop a framework by way of two parameterizations that
...establishes regionally representative relationships between aerosol-cloud
properties and their radiative effects. These relationships rely on new
spectral aerosol property retrievals of the single scattering albedo (SSA)
and asymmetry parameter (ASY). The retrievals capture the natural
variability of the study region as sampled, and both were found to be fairly
narrowly constrained (SSA: 0.83 ± 0.03 in the mid-visible, 532 nm;
ASY: 0.54 ± 0.06 at 532 nm). The spectral retrievals are well suited
for calculating the direct aerosol radiative effect (DARE) since SSA and ASY are tied directly to the irradiance measured in the presence of aerosols – one of the inputs to the spectral DARE. The framework allows for entire campaigns to be generalized into a set of
parameterizations. For a range of solar zenith angles, it links the
broadband DARE to the mid-visible aerosol optical depth (AOD) and the albedo (α) of the underlying scene (either clouds or clear sky) by way of the first parameterization: P(AOD, α). For ORACLES, the
majority of the case-to-case variability of the broadband DARE is
attributable to the dependence on the two driving parameters of P(AOD,
α). A second, extended, parameterization PX(AOD, α, SSA)
explains even more of the case-to-case variability by introducing the
mid-visible SSA as a third parameter. These parameterizations establish a direct link from two or three mid-visible (narrowband) parameters to the broadband DARE, implicitly accounting for the underlying
spectral dependencies of its drivers. They circumvent some of the
assumptions when calculating DARE from satellite products or in a modeling context. For example, the DARE dependence on aerosol microphysical
properties is not explicit in P or PX because the asymmetry parameter varies
too little from case to case to translate into appreciable DARE variability.
While these particular DARE parameterizations only represent the ORACLES
data, they raise the prospect of generalizing the framework to other
regions.
Southern Africa produces almost a third of the Earth’s biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ...ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts
of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well
as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ~ 350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ~ 100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.
Starch production and industrial use Ellis, R.P; Cochrane, M.P; Dale, M.F.B ...
Journal of the science of food and agriculture,
July 1998, Letnik:
77, Številka:
3
Journal Article
Recenzirano
This review of starch is concerned with its industrial uses, origins and structure. The current demand for starch is met by a restricted range of crops, the most important of which are potatoes, ...maize, wheat and tapioca. Improvements in the properties of starches for industrial uses can be achieved through chemical and physical modification of extracted starch and through the manipulation of starch biosynthesis in the plant itself. We examine starch structure and composition in relation to its use and exploitation by industry. The current understanding of physiological and biochemical mechanisms influencing starch formation in higher plants is described. This information is set in the context of the need to know the physical/chemical specification for each individual starch and to understand the genetic control of these characteristics in order to identify target genes for manipulation.
This paper explores the concept of cultural capital and suggests a framework for assessing its influence in the management and use of natural capital. Cultural capital has been described as the ...underlying factors that provide human societies with the means and adaptations to maintain themselves in their environment. Sustainable development calls for a shift in the way in which natural capital is managed and used and much effort has gone into discussing and analysing the sustainable development process and mechanisms by which natural capital levels can be maintained. Cultural capital is an important, but much neglected, element in this process. There have been attempts to analyse the role of culture in development, but these have been few and isolated. This paper identifies three key areas in which cultural capital has influence: ‘management objectives’, ‘efficiency of process’ and ‘demand’. These three areas form the basis of an analysis framework, designed to assess the presence of various cultural traits with regard to the main functions of natural capital—the provision of: raw materials, sinks, environmental services and amenity services.
Temporal patterns of crop raiding by elephants were studied for 13 months in 1996/1997 at Kibale Forest National Park, Uganda. To determine the influence of environmental factors on the timing of ...raiding, we tested for correlations between crop raiding patterns and the quality of natural forage within the forest as well as crop availability beyond park boundaries. Crop raiding occurred throughout the year with peaks in dry seasons when crop availability was high. Bananas and maize were the main crops raided. Variations in forage quality were moderate with small seasonal fluctuations and peaks in dry seasons. Monthly crop raiding incidences were not influenced by forage quality but by ripening of maize. Comparison of forage quality and temporal distribution of crop raiding between savanna and forest habitats suggests that crop availability is more important in forest habitats, whereas in savanna habitats large seasonal fluctuations in forage quality have a greater influence on temporal patterns of crop raiding.
Résumé
Les modèles temporels de l'incursion des cultures par éléphants étaient étudiés pendant 13 mois en 1996/97 au parc national de Kibale Forest au Uganda. Afin de déterminer l'influence d’éléments liéà l'environnement sur le timing des incursions, nous avons essayé de trouver les corrélations entre les modèles d'incursion et la qualité du fourrage naturel dans la forêt ainsi que la disponibilité de cultures au‐delà des frontières du parc. L'incursion des cultures s'est produite à travers l'année et culminait pendant les périodes sèches quand la disponibilité des cultures etaient au plus élevé. Les cultures ciblées le plus souvent étaient les bananes et le maïs. Des variations dans la qualité de fourrage était modérées, avec les petites fluctuations saisonnières et les points culminants pendant les périodes sèches. Les survenances mensuelles d'incursion des cultures n’étaient pas influencèes par la qualité de fourrage mais par le mûrissement du maïs. Une comparaison de qualité de fourrage et la distribution temporale des incursions entre les habitats forestiers et savanes suggère que la question de disponibilité est plus important dans les habitats forestiers, tandis que dans les habitats savanes des grandes fluctuations saisonnières au niveau de la qualité de fourrage exercent un influence plus marquée sur les modèles temporels de l'incursion des cultures.
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