Particle trajectories and simple models of transport in coherent vortices

The particle trajectories and transport effects of coherent vortices are computed and a number of advection and diffusion experiments using a time-dependent dynamical ring model are analyzed. Several features of the tracer distributions in the numerical solutions are similar to features noted in sea surface temperature images of Gulf Stream rings and are discussed from the point of view of the model. Comparisons between tracer distributions computed using the dynamic ring model and several purely kinematic ring representations demonstrate that most of the important features of ring transport are not altered by slow dynamical evolution. Loss rates from the ring trapped zone are also estimated, which permits calculation of cross-Gulf Stream chemical and biological fluxes due to ring formation. We demonstrate that the salinoty flux to the Slope Water caused by rings is comparable to that caused by the atmosphere.The transport of passive scalars produced by a series of rings moving through a channel (modeling the Slope Water region between the Shelf and the Gulf Stream) is computed. It is found that transport in the along-channel direction is enhanced by the presence of rings and is characterized by Nusselt numbers of 0(30–40). Cross-channel fluxes, while enhanced, are somewhat less affected by rings, and are generally characterized by Nusselt numbers < 0(10). The combined effect of rings on the Slope is seen to make it an anisotropic medium, with along-channel transport one to two orders of magnitude more efficient than cross-channel transport. The implications with respect to the Slope are discussed.     

Spatial Analysis of Environmental Change Impacts on Wheat Production in Mid-Lower North, South Australia

Three environmental change scenarios (the best scenario, the most likely scenario and the worst scenario) were used by the APSIM (Agricultural Production System sIMulator) Wheat module to study the possible impacts of future environmental change (climate change plus pCO₂ change) on wheat production in the Mid-Lower North of South Australia. GIS software was used to manage spatial-climate data and spatial-soil data and to present the results. Study results show that grain yield (kg ha⁻¹) was adversely affected under the worst environmental change scenario (−100% ∼ −42%) and the most likely environmental change scenario (−58% ∼ −3%). Grain nitrogen content (% N) either increased or decreased depending on the environmental change scenarios used and climate divisions (−25% ∼ +42%). Spatial variability was found for projected impact outcomes within climate divisions indicating the necessity of including the spatial distribution of soil properties in impact assessment.     

Sea-Spray-Generation Dependence on Wind and Wave Combinations: A Laboratory Study

Boundary-Layer Meteorology - We investigate the effects of wind–wave interactions on the surface sea-spray-generation flux. To this end, the Marine Aerosol Tunnel Experiment (MATE2019) was...     

Improving the Realism of Modeling Agronomic Adaptation to Climate Change: Simulating Technological Substitution

The purpose of the paper is to propose and test a new approach to simulating farmers' agronomic adaptation to climate change based on the pattern of adoption of technological innovation/substitution over time widely described as a S-shaped (or logistic) curve, i.e., slow growth at the beginning followed by accelerating and then decelerating growth, ultimately leading to saturation. The approach we developed is tested using the Erosion Productivity Impact Calculator crop model applied to corn production systems in the southeastern U.S. using a high-resolution climate change scenario. Corn is the most extensively grown crop in the southeastern U.S. The RegCM limited area model nested within the CSIRO general circulation model generated the scenario. We compare corn yield outcomes using this new form of adaptation (logistic) with climatically optimized (clairvoyant) adaptation. The results show logistic adaptation to be less effective than clairvoyant adaptation in ameliorating climate change impacts on yields, although the differences between the two sets of yields are statistically significant in one case only. These results are limited by the reliance on a single scenario of climate change. We conclude that the logistic technique should be tested widely across climate change scenarios, crop species, and geographic areas before a full evaluation of its effect on outcomes is possible.     

Africa and the Green Climate Fund: current challenges and future opportunities

Although the Green Climate Fund (GCF) is widely commendable in several ways, access to the Fund has been very challenging for many African countries. Using GCF published statistics, we identify possible challenges likely to be responsible for this. First, we present an assessment of the GCF’s Readiness Support Programme with respect to how the programme’s performance may have affected achievement of African countries’ readiness outcomes. Second, a critical evaluation of the status of African GCF portfolio (pipeline and approved projects) provides a means by which to assess how well Africa’s current portfolio aligns with GCF strategic impact areas, results areas and investment priorities. We then discuss GCF access modalities and the implications of relying on International Accredited Entities (IAEs) to indirectly access the Fund. The readiness support assessment indicates that the distribution of support requests and funding approvals is nearly equal across the regions of Africa, Asia Pacific and Latin America and the Caribbean. However, when the regions are considered individually, Africa demonstrates lower approvals with respect to requests and securing funding. Results from the GCF portfolio evaluation reveal that little or no attention has been devoted to GCF critical result areas such as forests and land use or transport, where great potentials for low-carbon development transitions exist. With respect to access modalities, the IAE financing mechanism currently provides access to the Fund for the majority of projects in both the global and African GCF portfolios. The implications of these findings are extensively discussed.

Key policy insights

• For Africa, limited readiness support and a reliance on International Accredited Entities constrains capacity building, thereby reinforcing a lack of both readiness and direct access to the GCF.

• There are opportunities for Africa to diversify its GCF portfolios, adhere to international commitments, and address its adaptation and development needs by identifying and capitalizing on linkages between GCF funding priorities, mitigation, and adaptation.

• There are leverage points within existing climate finance and governance systems that could catalyse a shift in Africa’s engagement with the GCF and generate positive, cascading effects on institutional strengthening, direct access accreditation and securing funding.

     

The evolution and orientation of early cycle 22 active regions

The evolution of six major active regions which appeared during the first phase of the present solar cycle (cycle 22) has been studied. It was found that the northern hemisphere regions exhibited a broad range of evolutionary behavior in which the commonly accepted normal pattern (whereby the follower flux moves preferentially polewards ahead of the leader flux) is represented only at one end of the range. At the other end of the range, the leader flux is displaced polewards of the follower flux. In the latter cases equatorward extensions of the polar coronal hole are noted.While it is emphasized that some of the regions in this study follow the more conventional pattern and that all regions in this study emerged during the early phase of cycle 22, the implications for theories of the solar polar field reversals are noted.     

Designing open water disposal for dredged muddy sediments

Open water disposal of muddy sediments in the estuarine environment is practiced to minimize dredging costs and to preserve contained disposal site capacity. Open water sites are usually either dispersive or retentive. Dispersive sites are used in the expectation that disposed sediments will not remain there, but will be transported out of the site, leaving room for additional disposal. Retentive sites are designed to ensure that disposed sediments mostly remain within the site. Choice of one of these approaches depends on the site character, sediment character, and disposal quantities. Design of disposal management plans for both site types is accomplished by use of field observations, laboratory tests, and numerical modeling.Three disposal site studies illustrate the methods used. At the Alcatraz site in San Francisco Bay, a dispersive condition is maintained by use of constraints on dredged mud characteristics that were developed from laboratory tests on erosion rates and from numerical modeling of the dump process. Field experiments were designed to evaluate the management procedure. In Corpus Christi Bay a numerical model was used to determine how much disposed sediment returns to the navigation channel, and to devise a location for disposal that will minimize that return. In Puget Sound a model has been used to ensure that most of the disposed material remains in the site. New techniques, including a piped disposal through 60 m of water, were investigated.     

The reconstruction of eighteenth century temperature records through the use of content analysis

The reconstruction of a temperature record for eighteenth century eastern Massachusetts is discussed. In addition to instrumental records diaries were analyzed in order to produce temperature indices. Reliability tests demonstrate that the methodology used is capable of replicating results regardless of changes in coders or intraregional variability in language. Validity tests, comparing diary reconstructions with instrumental records for the same period, produced positive results. A compilation of all climate related data shows the decades of the 1720's, 1750's, and 1760's were cool, while the 1770's and 1790's were warm.     

Large-eddy simulations of the effects of hilly terrain on the convective boundary layer

Large-eddy simulations of the convective boundary layer are compared over hilly versus flat surfaces. Moderate values for the height and horizontal spacing of the hills were selected. Thermally-direct hill-valley circulations are induced by the uneven terrain, accounting for a significant fraction of the resolved energy in the boundary-layer eddies. The probability of upward eddy motion reaches up to 70% over the hilltops and down to 15% over the valleys. Above-average values of both subgrid scale turbulent kinetic energy and upward eddy heat transport are found above the higher terrain. Horizontal spectra of vertical motion are strongly biased toward the horizontal scales of the terrain. Vertical profiles of atmospheric variables obtained by horizontal averaging, however, exhibit no significant differences between hilly and flat terrain simulations.     

Wind profile constants in a neutral atmospheric boundary layer over complex terrain

The roughness height z ₀ and the zero-plane displacement height d ₀ were determined for a region of complex terrain in the Pre-Alps of Switzerland. This region is characterized by hills of the order of 100 m above the valley elevations, and by distances between ridges of the order of 1 km; it lies about 20 to 30 km north from the Alps. The experimental data were obtained from radiosonde observations under near neutral conditions. The analysis was based on the assumption of a logarithmic profile for the mean horizontal wind existing over one half of the boundary layer. The resulting (z ₀/h) and (d ₀/h) (where h is the mean height of the obstacles) were found to be in reasonable agreement with available relationships in terms of placement density and shape factor of the obstacles, which were obtained in previous experiments with h-scales 2 to 4 orders of magnitude smaller than the present ones.