Adaptive Blending of Model and Observations for Automated Short-Range Forecasting: Examples from the Vancouver 2010 Olympic and Paralympic Winter Games

An automated short-range forecasting system, adaptive blending of observations and model (ABOM), was tested in real time during the 2010 Vancouver Olympic and Paralympic Winter Games in British Columbia. Data at 1-min time resolution were available from a newly established, dense network of surface observation stations. Climatological data were not available at these new stations. This, combined with output from new high-resolution numerical models, provided a unique and exciting setting to test nowcasting systems in mountainous terrain during winter weather conditions. The ABOM method blends extrapolations in time of recent local observations with numerical weather predictions (NWP) model predictions to generate short-range point forecasts of surface variables out to 6 h. The relative weights of the model forecast and the observation extrapolation are based on performance over recent history. The average performance of ABOM nowcasts during February and March 2010 was evaluated using standard scores and thresholds important for Olympic events. Significant improvements over the model forecasts alone were obtained for continuous variables such as temperature, relative humidity and wind speed. The small improvements to forecasts of variables such as visibility and ceiling, subject to discontinuous changes, are attributed to the persistence component of ABOM.     

Quantitative aspects of inorganic nutrient fluxes in the Gazi Bay (Kenya): implications for coastal ecosystems

Fluxes of dissolved inorganic nutrients: NH4+, NO2-, NO3-, PO4(3-) and Si(OH)4 from nearshore sediments of Gazi Bay were measured in situ within mangrove, seagrass and coral reef biotopes using benthic flux bell-jar chambers of cross-sectional area 0.066 m2 and volume 0.0132 m3. The objectives were: (1) to determine the influence of benthic fluxes, fluvial discharge and seasonal variations on the nutrient budget in the Bay waters; (2) to determine the effect of tidal and spatial variations on nutrient loads in the water column and (3) to establish the relative importance of the nutrient sources with regard to total community production of the Bay. The directly measured fluxes ranged from -270 to +148 micromol NH4+-N/m2/h; -60 to +63 micromol NO2(-)-N/m2/h; -79 to +41 micromol NO3(-)-N/m2/h; -79 to +75 micromol PO4(3-)-P/m2/h and +30 to +350 micromol Si(OH)4-Si/m2/h for and respectively. It was established that benthic fluxes are the major sources of dissolved inorganic NH4+, NO2- and Si(OH)4 while fluvial sources are important for NO3- and PO4(3-) into Gazi Bay waters. Seasonal variations had an appreciable effect on the PO4(3-) fluxes, N:Si ratio, river nutrient discharge, plankton productivity and important environmental factors such as salinity and temperature. Tidal and spatial variations had no significant effect on nutrient concentrations and net fluxes within the water column. The results imply that benthic fluxes are largely responsible for the nutrient dynamics of the nearshore coastal ecosystems especially where direct terrestrial inputs do not contribute significantly to the nutrient budget.     

Applying Cost/Benefit Analysis to Evaluate Investment in GIS: The Case of Ghana's Lands Commission Secretariat, Accra

One of the many reasons why GIS programmes in Africa and elsewhere in the developing world never get started is that top management are not fully persuaded to support such innovations. A favourable financial analysis of GIS investment will greatly enhance its chances of approval and continued funding if the computation is tied to the goals set by organisations. We argue that an approach provided by a score and weight process that is part of the Investment Evaluation Methodology (IEM) developed by Digital Equipment Corporation USA, for cost benefit analysis fulfils this objective as it is designed to assist top managers and policy‐makers in coming to an understanding of the nature and scope of the proposed GIS project. The methodology involves measuring benefits that are quantifiable (tangibles) and identifying those that are not (intangibles). A coherent and consistent framework for evaluating the GIS project is therefore made. The methodology is generic enough to be applied in any developing country context.     

Determination of Geoid over South China Sea and Philippine Sea from Multi-satellite Altimetry Data

A new computational procedure for derivation of marine geoid on a 2.5′×2.5′grid in a non-tidal system over the South China Sea and the Philippine Sea from multi-satellite altimeter sea surface heights is discussed. Single-and dual-satellite crossovers were performed, and components of deflections of the vertical were determined at the crossover positions using Sand-well's computational theory, and gridded onto a 2.5′×2.5′resolution grid by employing the Shepard's interpolation procedure. 2.5′×2.5′grid of EGM96-derived components of deflections of the vertical and geoid heights were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Molodensky-like formula via 1D-FFT technique to predict the geoid heights over the South China Sea and the Philippine Sea from the gridded altimeter-derived components of deflec-tions of the vertical. Statistical comparisons between the altimeter-and the EGM96- derived geoid heights showed that there was a root-mean-square agreement of ±0.35 m between them in a region of less tectonically active geological structures. However, over areas of tectonically active structures such as the Philippine trench, differences of about -19.9 m were obtained.     

Organic carbon accumulation in oligotrophic coastal lakes in southern Brazil during the last century

Journal of Paleolimnology - We report organic carbon (OC) accumulation rates in three freshwater ecosystems in southern Brazil, along the largest shallow coastal lagoon ecosystem in the world, the...     

Major Ion Chemistry in a Freshwater Coastal Lagoon from Southern Brazil (Mangueira Lagoon): Influence of Groundwater Inputs

This paper characterizes major ion distributions and investigates whether groundwater exerts a major control on the chemical functioning of Mangueira Lagoon, a large (90 km long), shallow (∼4–5 m deep), and fresh coastal lagoon in southern Brazil. Water volumes equivalent to ∼80% of the total annual input are used in the summer for irrigating nearby rice plantations, the most important regional economic activity. While Na⁺ and Cl⁻ are the major ions in local groundwater, Na⁺ and HCO₃⁻ are the most enriched ions in lagoon water. The ion concentrations measured in Mangueira Lagoon were homogeneous, except for a few samples affected by rainwater and groundwater inputs. A shore-normal transect starting at the pump house of a rice irrigation canal indicated strong groundwater input at this canal. In spite of the small volume contribution (∼2% of precipitation), groundwater discharge accounts for 50–70% of major ion inputs into the lagoon, with ∼70% of the groundwater inputs being anthropogenically derived (e.g., from the rice irrigation canals). This may have serious implications for the management of the coastal water resources from Mangueira Lagoon and other similar areas as groundwater associated with agricultural systems may be contaminated by fertilizers and pesticides. The results imply that groundwater should not be neglected in dissolved species’ budgets even when its volume contribution is small.     

Developing a GIS-Based Online Survey Instrument to Elicit Perceived Neighborhood Geographies to Address the Uncertain Geographic Context Problem

Although neighborhood factors have been consistently associated with health, technological difficulties in eliciting self-defined neighborhoods from large cohorts have compromised the interpretability of this research. Here, we offer a mixed-methods approach to elicit and validate self-defined neighborhoods. Participants used a customized Google.Maps interface to “draw” their neighborhood and answered questions about perceived map accuracy, neighborhood definition, and neighborhood activities. We compared geographic concordance of drawn and narrative neighborhood definitions, quantified differential accuracy by demographic characteristics, and examined factors influencing neighborhood definitions. We found similar geographic concordance between narrative and mapped boundaries in two cities, with no differences by neighborhood size. Self-reported neighborhoods had greater concordance with larger administrative areas (e.g., police precincts) than for smaller units (e.g., census tracts). To delineate their neighborhood boundaries, participants reported using administrative definitions, walking distance, their familiarity with people and structures, where they spend time, and physical landmarks. In New York City, participants also reported considering sociodemographic characteristics and transportation. Our method demonstrates the feasibility of collecting perceived (egocentric) neighborhoods through online mapping surveys, adaptable to many study settings.