Moderate Weather Research Articles

Evaluation of adaptive thermal comfort models in moderate climates and their impact on energy use in office buildings

Abstract Thermally Activated Building Systems (TABS) are regarded as top-cooling systems rather than full air-conditioning systems. Therefore, adaptive thermal comfort models (ASHRAE55, ISSO74 or EN15251) are supposed to be applicable to TABS buildings, although the comfort model conditions are not necessarily satisfied. This paper investigates whether, for a moderate climate and with the heating and cooling set points chosen according to the adaptive models, the building’s energy use reduces. After all, applying adaptive models, if appropriate, is thought to lower energy use because higher maximum operative zone temperatures T op, max are allowed, compared to the conventional ISO7730 model. For purpose of generality, a building with an ideal heating and cooling system is considered. Analysis of moderate climate weather data reveals a low energy reducing potential for the ASHRAE55 and ISSO74 model, because high reference outdoor temperatures hardly occur. EN15251 on the other hand, allows very high T op, max and will lower the cooling need. A 2-zone building simulation demonstrates a higher cooling need for ASHRAE55 and ISSO74, compared to ISO7730. Because cooling is needed during the whole year, the lower winter T op, max of these adaptive models causes these unexpected results. With real data of warmer years or varying gains, this conclusion holds.

Moisture and Condensation in Residential Buildings in aRelatively Dry Region

It is not unusual to face moisture problems in buildings in cold climates and wet regions. It is, however, unusual to have the same problem in a relatively dry region such as Jordon, which has moderate weather conditions and mild winters. Nevertheless, a significant proportion of houses and residential apartments in Jordan are affected. The monitoring of inside air conditions, wall surface temperatures, ventilation and living style has shown that a high relative humidity (RH >75%) occurs at walls resulting in possible condensation. These conditions, with visible or invisible condensation, enhance mould growth and damage walls. This apparently results from actual living conditions which fall short of comfort conditions due to high energy cost, poverty, limited ventilation and poor wall thermal insulation. Measurements indicated that actual inside wall surface temperatures were occasionally below the dew point. This was confirmed by a simple thermal analysis of typical walls showing the possible drop of inside surface temperatures down to 11oC. Additional factors to the problem in this region include lack of building quality control, the demand for cheap housing in which ventilation and thermal specifications are not a priority and in which heating is only intermittent heating.

Effect of turbulence on feeding intensity and survival of Japanese flounder Paralichthys olivaceus pelagic larvae

Three-day rearing experiments were conducted to study the effect of turbulence on the feeding intensity and survival of pelagic larvae of Japanese flounder Paralichthys olivaceus. Four levels of turbulence as control (10(-7.2) m2 s(-3)), low (10(-6.2) m2 s(-3)), mid (10(-5.6) m2 s(-3)) and high (10(-5.0) m2 s(-3)) were set by changing the flow rate of water pumped through pipes set on the bottom of the tanks. In B-stage larvae, defined as having buds of elongated dorsal fin rays, the feeding intensity and growth were higher in the low and mid turbulence levels, while survival was highest in the control level. Most of the larvae surviving in the control level, however, were judged to be in a seriously starved condition leading to subsequent high mortality. Because the three-day span of the rearing experiments was thought to be a little shorter than the periods before starvation-induced, high mortality occurs. In contrast, for D-stage larvae, their feeding and growth were optimal in the control and low levels. Feeding was more adversely affected in the high level for D-stage larvae compared with B-stage larvae. This is probably due to the compressed body shape and elongated dorsal fin rays of D-stage larvae, which may be more strongly affected by turbulence and, as a consequence, the larval feeding behaviour such as pursuit and capture of prey organisms becomes less efficient than in lower turbulence. Considering the vertical distribution of B and D-stage larvae in the oceanic water column, the optimum turbulence level range found in the present study corresponded to a wind speed of 7-10 m s(-1). Therefore, moderate weather conditions of this wind speed range are considered to potentially enhance survival of early larval stages of P. olivaceus.

Roof-harvested rainwater for potable purposes: Application of solar collector disinfection (SOCO-DIS)

The efficiency of solar disinfection (SODIS), recommended by the World Health Organization, has been determined for rainwater disinfection, and potential benefits and limitations discussed. The limitations of SODIS have now been overcome by the use of solar collector disinfection (SOCO-DIS), for potential use of rainwater as a small-scale potable water supply, especially in developing countries. Rainwater samples collected from the underground storage tanks of a rooftop rainwater harvesting (RWH) system were exposed to different conditions of sunlight radiation in 2-L polyethylene terephthalate bottles in a solar collector with rectangular base and reflective open wings. Total and fecal coliforms were used, together with Escherichia coli and heterotrophic plate counts, as basic microbial and indicator organisms of water quality for disinfection efficiency evaluation. In the SOCO-DIS system, disinfection improved by 20–30% compared with the SODIS system, and rainwater was fully disinfected even under moderate weather conditions, due to the effects of concentrated sunlight radiation and the synergistic effects of thermal and optical inactivation. The SOCO-DIS system was optimized based on the collector configuration and the reflective base: an inclined position led to an increased disinfection efficiency of 10–15%. Microbial inactivation increased by 10–20% simply by reducing the initial pH value of the rainwater to 5. High turbidities also affected the SOCO-DIS system; the disinfection efficiency decreased by 10–15%, which indicated that rainwater needed to be filtered before treatment. The problem of microbial regrowth was significantly reduced in the SOCO-DIS system compared with the SODIS system because of residual sunlight effects. Only total coliform regrowth was detected at higher turbidities. The SOCO-DIS system was ineffective only under poor weather conditions, when longer exposure times or other practical means of reducing the pH were required for the treatment of stored rainwater for potable purposes.

Relationship between landscape structure and burn severity at the landscape and class levels in Samchuck, South Korea

Fuel treatments for reducing fire risk are necessarily tied to the landscape structure including forest composition and configuration. Thus understanding the relationships between landscape structure and burn severity is important for developing guidelines and management strategies for fire-resilient forests. The goal of this study was to investigate the relationship between landscape structure as described by spatial pattern metrics and burn severity at the landscape and class levels. In 2000, a mostly severe fire burned 16,210 ha of dense forest located in Samchuck on the east coast of the Korean peninsula. Spatial pattern metrics including patch density, largest patch index, mean shape index, area-weighted mean shape index, Euclidean nearest neighborhood distance, and Shannon's diversity index, as well as topographic characteristics of slope and elevation, were correlated with burn severity based on delta Normalized Burn Ratio (dNBR) assessments. Regression tree analysis was also carried out with the same variables to avoid spatial autocorrelation and to reveal the relative importance of variables to burn severity. The results of this study strongly suggest that both composition and configuration of the forest cover patches are closely tied to burn severity. In particular, both the correlation analysis and regression tree analysis indicated that the area of red pine tree forest cover was the most significant factor in explaining the variance of burn severity. Topography and spatial configuration of forest cover patches were also significantly related to burn severity. The heterogeneity of forests also had a significant influence on burn severity. To reduce fire risk and increase the fire resilience of forests, forest managers and agencies need to consider enhancing the heterogeneity of forests when implementing fuel treatment schemes. However, such fuel treatments for landscape structure may only be effective under moderate weather conditions.

Modeling the impact of wind and waves on suspended particulate matter fluxes in the East Frisian Wadden Sea (southern North Sea)

Suspended particulate matter (SPM) fluxes and dynamics are investigated in the East Frisian Wadden Sea using a coupled modeling system based on a hydrodynamical model [the General Estuarine Transport Model (GETM)], a third-generation wave model [Simulating Waves Nearshore (SWAN)], and a SPM module attached to GETM. Sedimentological observations document that, over longer time periods, finer sediment fractions disappear from the Wadden Sea Region. In order to understand this phenomenon, a series of numerical scenarios were formulated to discriminate possible influences such as tidal currents, wind-enhanced currents, and wind-generated surface waves. Starting with a simple tidal forcing, the considered scenarios are designed to increase the realism step by step to include moderate and strong winds and waves and, finally, to encompass the full effects of one of the strongest storm surges affecting the region in the last hundred years (Storm Britta in November 2006). The results presented here indicate that moderate weather conditions with wind speeds up to 7.5 m/s and small waves lead to a net import of SPM into the East Frisian Wadden Sea. Waves play only a negligible role during these conditions. However, for stronger wind conditions with speeds above 13 m/s, wind-generated surface waves have a significant impact on SPM dynamics. Under storm conditions, the numerical results demonstrate that sediments are eroded in front of the barrier islands by enhanced wave action and are transported into the back-barrier basins by the currents. Furthermore, sediment erosion due to waves is significantly enhanced on the tidal flats. Finally, fine sediments are flushed out of the tidal basins due to the combined effect of strong erosion by wind-generated waves and a longer residence time in the water column because of their smaller settling velocities compared to coarser sediments.

Fusarium head blight in wheat: Impact of tillage and other agronomic practices under natural infection

Fusarium head blight (FHB) is a destructive disease of the world's wheat-growing areas. In Argentina, the area under reduced tillage has increased due to soil erosion that threatened productivity. The effect of conventional and no tillage systems on FHB combined with other agronomic practices such as nitrogen fertilization, and the influence of the environmental conditions was analysed under natural infection on different cultivars. Wheat trials were conducted in three consecutive years; maize was the previous crop in the first and wheat the previous crop in the subsequent two years of the study. The experimental design was a split plot, with tillage treatments (conventional tillage and no-till) as the main plots. Fertilizer treatments were applied as a range of urea concentrations. Fusarium head blight was observed in all three experimental years. Differences of disease expression among trials were associated with the environmental factors prevailing during the experiments. In the first year, with moderate weather conditions, the only interactions for FHB incidence were between no-till and urea split doses. Seedling emergence, seed health, thousand kernel weight and deoxynivalenol (DON) concentration did not differ suggesting that the fertilizers and genotypes did not affect disease susceptibility. Climatic conditions prevailing in the second year were more conducive to disease development and severe FHB infection was observed. Tillage and fertilization treatments did not affect the variables analysed. Only cultivars showed significant differences and DON values were high. In the third year, unfavourable conditions for disease development resulted in low disease levels and no effect or interaction among variables was observed. The results obtained would suggest that favourable weather conditions are likely to be more important than tillage practice and fertilizer treatments. Since soil conservation practices have been widely adopted in most areas of Argentina, an integrated used of all the available strategies should be considered to decrease FHB damage.

Two daily smoke maxima in eighteenth century London air

Varied electrostatics experiments followed Benjamin Franklin's pioneering atmospheric investigations. In Knightsbridge, Central London, John Read (1726–1814) installed a sensing rod in the upper part of his house and, using a pith ball electrometer and Franklin chimes, monitored atmospheric electricity from 1789 to 1791. Atmospheric electricity is sensitive to weather and smoke pollution. In calm weather conditions, Read observed two daily electrification maxima in moderate weather, around 9 am and 7 pm. This is likely to represent a double diurnal cycle in urban smoke. Before the motor car and steam railways, one source of the double maximum smoke pattern was the daily routine of fire lighting for domestic heating.

FIRE AND FOREST HISTORY AT MOUNT RUSHMORE

Mount Rushmore National Memorial in the Black Hills of South Dakota is known worldwide for its massive sculpture of four of the United States' most respected presidents. The Memorial landscape also is covered by extensive ponderosa pine (Pinus ponderosa) forest that has not burned in over a century. We compiled dendroecological and forest structural data from 29 plots across the 517-ha Memorial and used fire behavior modeling to reconstruct the historical fire regime and forest structure and compare them to current conditions. The historical fire regime is best characterized as one of low-severity surface fires with occasional (> 100 years) patches (< 100 ha) of passive crown fire. We estimate that only approximately 3.3% of the landscape burned as crown fire during 22 landscape fire years (recorded at > or = 25% of plots) between 1529 and 1893. The last landscape fire was in 1893. Mean fire intervals before 1893 varied depending on spatial scale, from 34 years based on scar-to-scar intervals on individual trees to 16 years between landscape fire years. Modal fire intervals were 11-15 years and did not vary with scale. Fire rotation (the time to burn an area the size of the study area) was estimated to be 30 years for surface fire and 800+ years for crown fire. The current forest is denser and contains more small trees, fewer large trees, lower canopy base heights, and greater canopy bulk density than a reconstructed historical (1870) forest. Fire behavior modeling using the NEXUS program suggests that surface fires would have dominated fire behavior in the 1870 forest during both moderate and severe weather conditions, while crown fire would dominate in the current forest especially under severe weather. Changes in the fire regime and forest structure at Mount Rushmore parallel those seen in ponderosa pine forests from the southwestern United States. Shifts from historical to current forest structure and the increased likelihood of crown fire justify the need for forest restoration before a catastrophic wildfire occurs and adversely impacts the ecological and aesthetic setting of the Mount Rushmore sculpture.

Measuring the Rate of Spread of Chaparral Prescribed fires in Northern California

Prescribed fire is a common method used to produce desired ecological effects in chaparral by mimicking the natural role of fire. Since prescribed fires are usually conducted in moderate fuel and weather conditions, models that accurately predict fire behavior and effects under these scenarios are important for management. In this study, explosive audio devices and steel stakes were used to record the location of the flaming front during seven prescribed fires in mature, chamise (Adenostoma fasciculatum) dominated chaparral in northern California. Intervals between detonations measured the time required for five fires to transverse a fixed distance and were used to estimate the rate of spread (ROS) during headfire burning conditions. In two other fires, a stopwatch was used to measure the time required to travel successive 5 m distances and ROS was calculated. Burns were completed during moderate weather conditions: average temperature 17 °C, average relative humidity 42 %, and wind light and variable, generally from the west ranging from 0 km h−1 to 8 km h−1. Average percent moisture was 92.1 % for chamise live one-hour fuels, and 8.8 % for chamise dead one-hour fuels. Live fuel height averaged 1.2 m. Overall average ROS was 0.36 m s−1 (range 0.22 m s−1 to 0.56 m s−1) for areas where the flaming front advanced upslope. Measurements of ROS were indeterminable for many of the points along the line transects due to lack of visibility from smoke and from fire not traversing the terrain as predicted. For comparison, BehavePlus fire modeling was performed using five different shrub fuel models (NFFL 4, SH5, SH7, SCAL15, SCAL17); all models underestimated ROS and flame length with NFFL model 4 producing values most similar to that recorded during the prescribed fires. Users of the recently developed fuel models may benefit from field studies to verify model adequacy and fire behavior predictions.

Changes in Stream Channel Morphology Caused by Replacing Road-Stream Crossings on Timber Harvesting Plans in Northwestern California

Abstract Past studies have shown that roads used for timber management and recreation are major sources of sedimentation in many streams throughout the Pacific Northwestern United States. Stream crossings are portals for the entry of sediment derived from road surface erosion. They are also prone to catastrophic failure during stressing weather events if they are undersized or otherwise deficient in design or construction. In recent years, public and private landowners have replaced or removed numerous deficient crossings in forested watersheds throughout California and elsewhere in the West. The benefits of replacing these crossings include eliminating both chronic and episodic inputs of sediment to streams. When old crossings are replaced with new, properly designed and installed crossings, there is a potential for construction-related erosion. This research examined the postconstruction erosion associated with the replacement of 30 stream crossings in coastal California. Channel surveys were conducted immediately after construction and after the passage of one winter rainy season. The results indicated very little erosion on most sites; 11 experienced no erosion at all. On those sites where erosion did occur, the amounts did not exceed 10 cubic yards. A few sites experienced aggradation or erosion unrelated to upgrading but due to upstream landslides. This research shows upgraded stream crossings on commercial timberland may contribute little sediment to streams after construction under moderate weather conditions if adequate erosion control measures are implemented.

Estimation of building component UA and gA from outdoor tests in warm and moderate weather conditions

Accurate knowledge of the thermal properties of building components is necessary to implement adequate energy saving strategies in buildings. Outdoor experiments using test cells are very useful tools for realistic estimation of these properties. This paper describes the analyses performed, and the procedure followed in identifying and solving some problems found when building components are tested for UA and gA in a test cell under warm and moderate weather conditions. A window component was tested in a PASLINK test cell at the CIEMAT’s ‘Plataforma Solar de Almería (PSA-CIEMAT)’ in Tabernas (Almería, Spain) and several data sets recorded under quite different weather and test conditions were analysed. First the problems identified when applying the usual test and linear analysis procedures are described. Then hypotheses about the cause of these problems are formulated. Afterwards, strategies followed for testing these hypotheses are described. Once the cause of the problems had been identified, they were fine tuned to find a model for accurate UA and gA estimation. This study demonstrated that nonlinear models, in which long wave radiation is considered as nonlinear effect, yield remarkably better performance than the commonly used linear models, for estimating the component UA and gA values.

Use of MODIS and synthetic aperture radar wind speed imagery to describe the morphology of open cell convection

Moderate resolution imaging spectroradiometer (MODIS) imagery, meteorological analyses, and numerical weather prediction model forecasts for a 28–29 October 2006 case study are employed to argue that squall-and-lull patterns observed within a corresponding synthetic aperture radar (SAR) derived wind speed image are the result of open cell convection. In addition, the suite of data is exploited to advance a new conceptual model of open cell convection. MODIS imagery reveals that the open cell convection reported in this paper is composed primarily of cumulus humulus and cumulus congestus clouds, with cloud shadow measurements yielding a factor-of-three variation in cloud top height between the highest clouds (those on the leading or downwind edge of the cells) and the more shallow clouds along the sides and rear of the cells. The MODIS imagery reveals that the tallest clouds typically contain ice, which suggests that precipitation-driven downdrafts may cause the wind squalls seen in SAR-derived wind speed imagery. Individual squall-and-lull features have an elliptical boundary with an arc-shaped squall along the downwind edge of the feature, with wind speed decreasing gradually across the feature to its upwind edge.

Determinants of changes in the regional urban heat island in metropolitan Phoenix (Arizona, USA) between 1990 and 2004

We investigated the spatial and temporal variation in June mean minimum tempera- tures for weather stations in and around metropolitan Phoenix, USA, for the period 1990 to 2004. Temperature was related to synoptic conditions, location in urban development zones (DZs), and the pace of housing construction in a 1 km buffer around fixed-point temperature stations. June is typi- cally clear and calm, and dominated by a dry, tropical air mass with little change in minimum tem- perature from day to day. However, a dry, moderate weather type accounted for a large portion of the inter-annual variability in mean monthly minimum temperature. Significant temperature variation was explained by surface effects captured by the type of urban DZ, which ranged from urban core and infill sites, to desert and agricultural fringe locations, to exurban. An overall spatial urban effect, derived from the June monthly mean minimum temperature, is in the order of 2 to 4 K. The cumula- tive housing build-up around weather sites in the region was significant and resulted in average increases of 1.4 K per 1000 home completions, with a standard error of 0.4 K. Overall, minimum tem- peratures were spatially and temporally accounted for by variations in weather type, type of urban DZ (higher in core and infill), and the number of home completions over the period. Results compare favorably with the magnitude of heating by residential development cited by researchers using differing methodologies in other urban areas.

Impact of climate change on area burned in Alberta's boreal forest

Eight years of fire weather data from sixteen representative weather stations within the Boreal Forest Natural Region of Alberta were used to compile reference weather streams for low, moderate, high, very high and extreme Fire Weather Index (FWI) conditions. These reference weather streams were adjusted to create daily weather streams for input into Prometheus – the Canadian Wildland Fire Growth Model. Similar fire weather analyses were completed using Canadian Regional Climate Model (CRCM) output for northern Alberta (174 grid cells) to generate FWI class datasets (temperature, relative humidity, wind speed, Fine Fuel Moisture Code, Duff Moisture Code and Drought Code) for 1 ×, 2 × and 3 × CO2 scenarios. The relative differences between the CRCM scenario outputs were then used to adjust the reference weather streams for northern Alberta. Area burned was calculated for 21 fires, fire weather classes and climate change scenarios. The area burned estimates were weighted based on the historical frequency of area burned by FWI class, and then normalized to derive relative area burned estimates for each climate change scenario. The 2 × and 3 × CO2 scenarios resulted in a relative increase in area burned of 12.9 and 29.4% from the reference 1 × CO2 scenario.

Acoustic bottom detection and seabed classification in the German Bight, southern North Sea

To investigate the hydrodynamic activity of the seabed in the German Bight, underwater remote sensing was carried out over an area of 32 km2 located 20 km northeast of Helgoland island in the southern North Sea in January, May and August 2001. On the basis of acoustic seabed classification, six seabed types have been identified by the combined evaluation of side-scan sonar records, wave-shape analysis of echo-sounder data, and 100 grab samples. In five seabed types, the acoustic classes can be distinguished on the basis of sediment characteristics, comprising size components ranging from coarse pebbles to fine sand. The sixth seabed type corresponds to large pebbles and cobbles which are completely overgrown with brown algae. Statistically, the complex spatial patchiness of the six classes varied significantly in the course of the study period. During the winter period (January 2001), the study site was dominated by coarse material, except for a small area of finer sediment in the centre. With the onset of more moderate weather conditions in spring (May 2001), a general fining trend in sediment composition was observed, especially in the deeper western parts of the study area. In summer (August 2001), finer sediments still dominated but a slight increase in signal roughness suggests an overprint by coarser lag deposits and/or denser coverage by benthic organisms (e.g. Lanice conchilega) which then were found more frequently in grab samples, in association with finer sand. These findings demonstrate that the distribution of seafloor sediments and their benthic fauna in the deeper part of the German Bight region are controlled largely by seasonal changes in hydrodynamic conditions. These changes are reflected in correspondingly high variability in the complex patchiness of sediment distribution patterns, which would not have been adequately resolved by any standard sampling procedure.

Pilot Testing of Upflow Continuous Backwash Filters for Tertiary Denitrification and Phosphorus Removal

Pilot testing of upflow continuous backwash filter (UCB) for tertiary denitrification and phosphorus removal was conducted at the Hagerstown wastewater treatment plant. The pilot testing was conducted to determine denitrification performance capabilities of the upflow continuous backwash filters under cold weather operation and low effluent total nitrogen (TN) and total phosphorus limits. As part of a state-wide strategy for meeting the nutrient reduction goals of the Chesapeake 2000 Agreement with the U.S. Environmental Protection Agency and the other Chesapeake Bay watershed states, the State of Maryland is requiring all WWTPs > 0.5 mgd be upgraded to meet “limit of technology” (LOT) effluent standards of 3 mg/L TN and 0.3 mg/L TP on an annual average basis. The testing program included operation over a range of hydraulic and nitrate mass loading rates, moderate and cold weather operation, with and without chemical phosphorus removal; and testing the response of the filters to nitrate, solids spikes and wet weather flows. At hydraulic loading rates up to 4.0 gpm/ft

On the influence of several meteorological factors on polarization state of microwave signals, propagating in semi-arid terrestrial links

The cause for the changes in polarization state of microwave signals is searched after physical properties of the channel of propagation and their variations in accordance with atmospheric state. The characteristics of the air, as propagation medium, are determined by the content, concentration and physical properties of the suspended particulates; especially it is noticeable in the surface layer over the areas with high levels of aerosol concentration and humidity (urban, semi-arid, highways, etc.). The interaction between aerial water and solid particulates leads to the appearance of increased amounts of enlarged grains with changed dielectric permittivity /spl epsiv//spl tilde//sub g/, which value depends on the water fraction in the grain, particularly in the centimeter wave range. The formation of less or more dense volumes with various /spl epsiv//spl tilde//sub g/ entails displacement of the transmitted signal, while wind exerts control over the distribution of such irregularities in the air. Fairly high correlation (with coefficients |/spl rho/|>0.45) between temperature, humidity, concentration of suspended particles and winds, and the power P/sub r/ and cross-polarization discrimination (XPD) characteristics (XPD and /spl delta/) of microwave signals was observed under moderate weather conditions. During a quiet 24-h cycle the mean level of P/sub r/ and XPD changes in /spl sim/ 10% and 30%, correspondently; fastest variations in depolarization degree are obtained close to sunset and after sunrise, when the large gradients of meteorological parameters and maximum instability of air streams take place. Seasonal fluctuations of P/sub r/ and XPD are registered, too.

Comparison between an indoor and an outdoor 6-minute walk test among individuals with chronic obstructive pulmonary disease

Brooks D, Solway S, Weinacht K, Wang D, Thomas S. Comparison between an indoor and an outdoor 6-minute walk test among individuals with chronic obstructive pulmonary disease. Objectives: To investigate the feasibility of an outdoor 6-minute walk test (6MWT) as a measure of functional status among individuals with chronic obstructive pulmonary disease (COPD), and to examine the relationship between performance on an indoor and an outdoor 6MWT. Design: An experimental, repeated-measures crossover design. Subjects were studied on 2 separate days in the same week. Two 6MWTs—one indoors and the other outdoors—were performed on each study day, with a rest in between. The test order was randomly selected on the first day and reversed on the second day. Outdoor tests were performed on days of moderate weather conditions (mean temperature ± standard deviation, 21°±3°C; mean wind speed, 15±7km/h; no precipitation) and on a flat surface (sidewalk). Setting: Outpatient rehabilitation program in Ontario. Participants: Eighteen subjects with COPD (10 men, 8 women; age, 70±8y), 5 using supplemental oxygen at rest (forced expiratory volume in 1s, 1.0±0.3L; 42%±8% of predicted). Interventions: Not applicable. Main Outcome Measures: Distance walked in 6 minutes (in meters), duration of rest (in seconds), and change in rate of perceived dyspnea. Results: There was no significant effect of setting (indoors vs outdoors) on distance walked (394±86m vs 398±84m, P=0.4), duration of rest (13±28s vs 9±20s, P=0.4), or change in rate of perceived dyspnea (2.3±1.7 vs 2.3±2.0, P=0.8). Testing day had no significant effect on walk test performance (all P>0.1). Conclusions: The results indicate that the 6MWT performed outdoors within reasonable climatic parameters may be reflective of 6MWT performance indoors.

Factors influencing fire behaviour in shrublands of different stand ages and the implications for using prescribed burning to reduce wildfire risk

Fire behaviour under experimental conditions is described in nine Mediterranean gorse shrublands ranging from 3–12 years of age with different fuel loads. Significant differences in the fire-line intensity, fuel load and rate of fire spread have been found to be related to the stage of development of the communities. Fire spread is correlated with fuel moisture using multiple regression techniques. Differences in fuel moisture between mature and young communities under moderate weather conditions have been found. The lower moisture content identified in the mature shrubland is due both to the decreasing moisture content of senescent shrubland in some species, mainly in live fractions of Ulex parviflorus Pourr. fuel, and to a substantial increase in dead fuel fractions with low percentages of moisture content. The result is that the older the shrubland is, the greater will be the decrease in the total moisture content of the vegetation. In these moderate weather conditions, the fire intensity of the mature community was as high as the maximum intensity recommended for prescribed fires. This fact seems to indicate that, even under moderate conditions, prescribed burning as an alternative management tool in the mature shrubland must always take into account fuel control; on the other hand, this technique could be applied more easily when the shrubland is at an intermediate growth stage (4–5 years of age). Therefore, more frequent low-intensity prescribed fires are indicated to abate the risk of catastrophic fire.