Statistics for Spatial Data.

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

「脆弱性(Vulnerability)」とは何か

応用水文 = Applied hydrology

[1] Arctic amplification (AA) – the observed enhanced warming in high northern latitudes relative to the northern hemisphere – is evident in lower-tropospheric temperatures and in 1000-to-500 hPa thicknesses. Daily fields of 500 hPa heights from the National Centers for Environmental Prediction Reanalysis are analyzed over N. America and the N. Atlantic to assess changes in north-south (Rossby) wave characteristics associated with AA and the relaxation of poleward thickness gradients. Two effects are identified that each contribute to a slower eastward progression of Rossby waves in the upper-level flow: 1) weakened zonal winds, and 2) increased wave amplitude. These effects are particularly evident in autumn and winter consistent with sea-ice loss, but are also apparent in summer, possibly related to earlier snow melt on high-latitude land. Slower progression of upper-level waves would cause associated weather patterns in mid-latitudes to be more persistent, which may lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding, cold spells, and heat waves.

Retrieval of nearshore bathymetry from Landsat 8 images: A tool for coastal monitoring in shallow waters

Coastal hazards affect the majority of sandy shores worldwide, and are responsible for damage to, and destruction of, property and infrastructure. The research reported here presents an integrated method for defining set-back lines associated with coastal hazards on sandy shores for a 50-year period of interest. The method is based on a worst-case scenario approach, the shoreline evolutionary trend being the basis for the initial set-back line determination. Set-back lines are afterwards adjusted by incorporating changes associated with the acceleration of sea-level rise and the evaluation of the consequences (instantaneous shoreline retreat and overwash) of an extreme storm. The method considers different approaches depending on the shoreline behaviour (erosion, dynamic stability or accretion). The set-back lines as determined are plotted over rectified aerial photographs, allowing for a straight-forward interpretation of results. The method was applied to a test case within a barrier island system (Ancao Peninsula, Ria Formosa, Algarve, Portugal). This study area was chosen because it exhibits the three different types of shoreline evolution. The method easily shows the differences in erosion-related coastal hazards along the study area, being an important tool for coastal management. However, the method should be able to be refined at every 5–10 years, for a new 50-year period, by integrating new formulations based on advances in coastal science, and by including updated information and data about the areas to which the method is applied.

An integrated method for the determination of set-back lines for coastal erosion hazards on sandy shores

This study analyses beach morphological change during six consecutive storms acting on the meso-tidal Faro Beach (south Portugal) between 15 December 2009 and 7 January 2010. Morphological change of the sub-aerial beach profile was monitored through frequent topographic surveys across 11 transects. Measurements of the surf/swash zone dimensions, nearshore bar dynamics, and wave run-up were extracted from time averaged and timestack coastal images, and wave and tidal data were obtained from offshore stations. All the information combined suggests that during consecutive storm events, the antecedent morphological state can initially be the dominant controlling factor of beach response; while the hydrodynamic forcing, and especially the tide and surge levels, become more important during the later stages of a storm period. The dataset also reveals the dynamic nature of steep-sloping beaches, since sub-aerial beach volume reductions up to 30 m3/m were followed by intertidal area recovery (–2 < z < 3 m) with rates reaching ~10 m3/m. However, the observed cumulative dune erosion and profile pivoting imply that storms, even of regular intensity, can have a dramatic impact when they occur in groups. Nearshore bars seemed to respond to temporal scales more related to storm sequences than to individual events. The formation of a prominent crescentic offshore bar at ~200 m from the shoreline appeared to reverse the previous offshore migration trend of the inner bar, which was gradually shifted close to the seaward swash zone boundary. The partially understood nearshore bar processes appeared to be critical for storm wave attenuation in the surf zone; and were considered mainly responsible for the poor interpretation of the observed beach behaviour on the grounds of standard, non-dimensional, morphological parameters. Copyright © 2011 John Wiley & Sons, Ltd.

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Beach erosion and recovery during consecutive storms at a steep‐sloping, meso‐tidal beach

Burrowing behavior of Procambarus clarkii in Portugal was investigated at 6 sites (3 rice fields, 2 reservoirs, and 1 marsh) from February 1991 to February 1993. Average burrow density (number of burrows/m2), relation between burrow density and substrate type, burrowing activity, burrow occupation (sex, size, and maturation of the animals), burrow morphology (burrow complexity, mean tunnel depth), and burrow distribution in relation to the water level were studied. Average burrow (b) density ranged from 0.013 b/m2 to 6.28 b/m2, the highest density being in a rice-field drainage channel. A burrowing activity index was estimated, indicating that burrowing is mostly a seasonal activity, being most intense from May-October. Burrowing activity occurred only when the ratio of fine particles over coarser particles was higher than 0.1-0.2. Mean carapace length of burrowing animals varied from 35.3-43.8 mm. Most of the individuals in burrows were mature. Immature and juvenile animals occupied burrows in late fall, winter, and early spring, while mature crayfish were found in late spring, summer, and early fall. The burrow morphology was generally simple, but more complex burrows were also observed. Mean tunnel depth ranged from 0.28-0.58 m. The longer burrows measured approximately 4.20 m long. The burrows were generally located at the water level in rice-field sites and above the water level in marsh and reservoir sites. Burrows were observed only in a zone of Myriophillum sp. in marsh and reservoir sites.

Óscar Ferreira

Papers

Retrieval of nearshore bathymetry from Landsat 8 images: A tool for coastal monitoring in shallow waters

An integrated method for the determination of set-back lines for coastal erosion hazards on sandy shores

Beach erosion and recovery during consecutive storms at a steep‐sloping, meso‐tidal beach

Burrowing Behavior of the Introduced Red Swamp Crayfish Procambarus Clarkii (Decapoda: Cambaridae) in Portugal

Classification of washover dynamics in barrier islands