Cloud — Aerosol interaction during lightning activity over land and ocean: Precipitation pattern assessment

The present study attempts to identify the land - ocean contrast in cloud - aerosol relation during lightning and non-lightning days and its effect on subsequent precipitation pattern. The thermal hypothesis in view of Convective Available Potential Energy (CAPE) behind the land - ocean contrast is observed to be insignificant in the present study region. The result shows that the lightning activities are significantly and positively correlated with aerosols over both land and ocean in case of low aerosol loading whereas for high aerosol loading the correlation is significant but, only over land. The study attempts to comprehend the mechanism through which the aerosol and lightning interact using the concept of aerosol indirect effect that includes the study of cloud effective radius, cloud fraction and precipitation rate. The result shows that the increase in lightning activity over ocean might have been caused due to the first aerosol indirect effect, while over land the aerosol indirect effect might have been suppressed due to lightning. Thus, depending on the region and relation between cloud parameters it is observed that the precipitation rate decreases (increases) over ocean during lightning (non-lightning) days. On the other hand during non-lightning days, the precipitation rate decreases over land.     

Landslide detection and susceptibility mapping using LiDAR and an artificial neural network approach: a case study in the Cuyahoga Valley National Park,Ohio

The purpose of this study was to detect shallow landslides using hillshade maps derived from light detection and ranging (LiDAR)-based digital elevation model (DEM) derivatives. The landslide susceptibility mapping used an artificial neural network (ANN) approach and backpropagation method that was tested in the northern portion of the Cuyahoga Valley National Park (CVNP) located in northeast Ohio. The relationship between landslides and predictor attributes, which describe landform classes using slope, profile and plan curvatures, upslope drainage area, annual solar radiation, and wetness index, was extracted from LiDAR-based DEM using geographic information system (GIS). The approach presented in this paper required a training study area for the development of the susceptibility model and a validation study area to test the model. The results from the validation showed that within the very high susceptibility class, a total of 42.6 % of known landslides that were associated with 1.56 % of total area were correctly predicted. In contrast, the very low susceptibility class that represented 82.68 % of the total area was associated with 1.20 % of known landslides. The results suggest that the majority of the known landslides occur within a small portion of the study area, consistent with field investigation and other studies. Sample probabilistic maps of landslide susceptibility potential and other products from this approach are summarized and presented for visualization to help park officials in effective management and planning.     

When Is Asia?

Recently, in geography and related disciplines, there has been a call to generate conceptual frameworks from the Global South. Such a call does not imply cataloging the diversity and plurality of the world but rather requires new understandings of relationalities and transformations. In this article, I contribute to these ongoing endeavors by thinking from Asia. In doing so, I interpret Asia not as a bounded geographical location but instead as interconnected space. In particular, I pay attention to how such interconnections reference Asian models of development, thereby creating a politics of futurity. A study of the making of Asian futures allows a broader understanding of the renewal of development in a rearranged south–north world.     

Modeling the Population Effects of Hypoxia on Atlantic Croaker (<Emphasis Type="Italic">Micropogonias undulatus</Emphasis>) in the Northwestern Gulf of Mexico: Part 1—Model Description and Idealized Hypoxia

We developed a spatially explicit, individual-based model to analyze how hypoxia effects on reproduction, growth, and mortality of Atlantic croaker in the northwestern Gulf of Mexico lead to population-level responses. The model follows the hourly growth, mortality, reproduction, and movement of individuals on a 300 × 800 spatial grid of 1-km² cells for 140 years. Chlorophyll-a concentration, water temperature, and dissolved oxygen (DO) were specified daily for each grid cell and repeated for each year of the simulation. A bioenergetics model was used to represent growth, mortality was assumed stage- and age-dependent, and the movement behavior of juveniles and adults was modeled based on temperature and avoidance of low DO. Hypoxia effects were imposed using exposure effect submodels that converted time-varying exposures to low DO to reduced hourly growth, increased hourly mortality, and reduced annual fecundity. Results showed that 100 years of either mild or intermediate hypoxia produced small reductions in population abundance, while repeated severe hypoxia caused a 19% reduction in long-term population abundance. Relatively few individuals were exposed to low DO each hour, but many individuals experienced some exposure. The response was dominated by a 5% average reduction in annual fecundity of individuals. Under conditions of random sequences of mild, intermediate, and severe hypoxia years occurring in proportion to their historical frequency, the model predicted a 10% decrease in the long-term population abundance of croaker. A companion paper substitutes hourly DO values from a three-dimensional water quality model for the idealized hypoxia and results in a more realistic population reduction of about 25%.     

The First Hop: Use of Beaufort Sea Deltas by Hatch-Year Semipalmated Sandpipers

River deltas along Alaska’s Beaufort Sea coast are used by hatch-year semipalmated sandpipers (Calidris pusilla) after leaving their terrestrial natal sites, but the drivers of their use of these stopover sites on the first “hop” of fall migration are unknown. We quantified sandpiper temporal distribution and abundance as related to food resources at three river deltas during the beginning of their fall migration (post-breeding period) to compare the habitat quality among these deltas. We conducted population counts, sampled invertebrates, and captured birds to collect blood samples from individuals for triglyceride and stable isotope analyses to determine fattening rates and diet. Patterns of sandpiper and invertebrate abundance were complex and varied among deltas and within seasons. River deltas were used by sandpipers from late July to late August, and peak sandpiper counts ranged from 1000 to 4000 individuals, of which 98% were hatch-year semipalmated sandpipers. Isotopic signatures from blood plasma samples indicated that birds switched from a diet of upland tundra to delta invertebrate taxa as the migration season progressed, suggesting a dependence on delta invertebrates. Despite differences in diet among deltas, we found no differences in fattening rates of juvenile sandpipers as indicated by triglyceride levels. The number of sandpipers was positively associated with abundance of Amphipoda and Oligochaeta at the Jago and Okpilak-Hulahula deltas; an isotopic mixing model indicated that sandpipers consumed Amphipoda and Oligochaeta at Jago, mostly Chironomidae at Okpilak-Hulahula and Spionidae at Canning. Regardless of the difference in sandpiper diets at the Beaufort Sea deltas, their similar fattening rates throughout the season indicate that all of these stopover sites provide a critical food resource for hatch-year sandpipers beginning their first migration.     

Evaluating Tidal Wetland Restoration Performance Using National Estuarine Research Reserve System Reference Sites and the Restoration Performance Index (RPI)

Evaluations of tidal wetland restoration efforts suffer from a lack of appropriate reference sites and standardized methods among projects. To help address these issues, the National Estuarine Research Reserve System (NERRS) and the NOAA Restoration Center engaged in a partnership to monitor ecological responses and evaluate 17 tidal wetland restoration projects associated with five reserves. The goals of this study were to (1) determine the level of restoration achieved at each project using the restoration performance index (RPI), which compares change in parameters over time between reference and restoration sites, (2) compare hydrologic and excavation restoration projects using the RPI, (3) identify key indicator parameters for assessing restoration effectiveness, and (4) evaluate the value of the NERRS as reference sites for local restoration projects. We found that the RPI, modified for this study, was an effective tool for evaluating relative differences in restoration performance; most projects achieved an intermediate level of restoration from 2008 to 2010, and two sites became very similar to their paired reference sites, indicating that the restoration efforts were highly effective. There were no differences in RPI scores between hydrologic and excavation restoration project types. Two abiotic parameters (marsh platform elevation and groundwater level) were significantly correlated with vegetation community structure and thus can potentially influence restoration performance. Our results highlight the value of the NERRS as reference sites for assessing tidal wetland restoration projects and provide improved guidance for scientists and restoration practitioners by highlighting the RPI as a trajectory analysis tool and identifying key monitoring parameters.     

Location-based environmental factors contributing to rainfall-triggered debris flows in the Ba river catchment,northwest Viti Levu island,Fiji

Mass movements in tropical Pacific small island developing states (SIDS) can be devastating although studies are relatively few and contributing environmental factors are not often investigated in detail. On 25 January 2012, following 3 days of heavy monsoonal rainfall (c. 550 mm) during a La Niña episode, more than 150 debris flows were triggered in the western part of the Ba river catchment of northwest Viti Levu island, Fiji. Reconnaissance field survey and geographical information system (GIS) analyses using high-resolution satellite imagery were carried out to investigate factors that may have led to the occurrence of the debris flows in the catchment. We evaluated the correlation between the density of mass movements (number of mass movements/km²) and several continuous variables using data measured within the GIS. There was a weak but significant positive correlation between mass movement density and elevation (r = 0.38, p value < 0.01), cyclonic precipitation (r = 0.37, p value < 0.01) and stream density (r = 0.31, p value < 0.01). Ninety-three percent of the mass movements occur within a plantation of Pinus caribaea (Caribbean pine) on slopes oriented mainly to the northeast and east on (trade) windward slopes and may be significant factors for their development. Although forests generally have a stabilizing effect on slopes, the plantation at Ba was a mature stand on its second plantation cycle and is a species that has a shallow rooting system making it more susceptible to failure.