David Rayner

Wind speed climatology and trends for Australia, 1975–2006: Capturing the stilling phenomenon and comparison with near‐surface reanalysis output

[1] Near-surface wind speeds (u) measured by terrestrial anemometers show declines (a ‘stilling’) at a range of midlatitude sites, but two gridded u datasets (a NCEP/NCAR reanalysis output and a surface-pressure-based u model) have not reproduced the stilling observed at Australian stations. We developed Australia-wide 0.01 resolution daily u grids by interpolating measurements from an expanded anemometer network for 1975–2006. These new grids represented the magnitude and spatialvariability of observed u trends, whereas grids from reanalysis systems (NCEP/NCAR, NCEP/DOE and ERA40) essentially did not, even when minimising the sea-breeze impact. For these new grids, the Australianaveraged u trend for 1975–2006 was 0.009 m s 1 a 1 (agreeing with earlier site-based studies) with stilling over 88% of the land-surface. This new dataset can be used in numerous environmental applications, including benchmarking general circulation models to improve the representation of key parameters that govern u estimation. The methodology implemented here can be applied globally. Citation: McVicar, T. R., T. G. Van Niel, L. T. Li, M. L. Roderick, D. P. Rayner, L. Ricciardulli, and R. J. Donohue (2008), Wind speed climatology and trends for Australia, 1975 – 2006: Capturing the stilling phenomenon and comparison with near-surface reanalysis output, Geophys. Res. Lett., 35, L20403,

Impact of climate change on the hydroclimatology of Lake Tana Basin, Ethiopia

[1] Climate change has the potential to reduce water resource availability in the Nile Basin countries in the forthcoming decades. We investigated the sensitivity of water resources to climate change in the Lake Tana Basin, Ethiopia, using outputs from global climate models (GCMs). First, we compiled projected changes in monthly precipitation and temperature in the basin from 15 GCMs. Although the GCMs uniformly suggest increases in temperature, the rainfall projections are not consistent. Second, we investigated how changes in daily temperature and precipitation might translate into changes in streamflow and other hydrological components. For this, we generated daily climate projections by modifying the historical data sets to represent the changes in the GCM climatologies and calculated hydrological changes using the Soil and Water Assessment Tool (SWAT). The SWAT model itself was calibrated and validated using the flows from four tributaries of Lake Tana. For the Special Report on Emissions Scenarios A2 scenario, four of the nine GCMs investigated showed statistically significant declines in annual streamflow for the 2080–2100 period. We interpret our results to mean that anthropogenic climate changes may indeed alter the water balance in the Lake Tana Basin during the next century but that the direction of change cannot be determined with confidence using the current generation of GCMs.

Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications

Knowledge of how the mean radiant temperature (Tmrt) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how Tmrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of Tmrt in three high latitude cities are investigated in order to analyse the impact of geographical context and climate conditions. Results showed large spatial variations between sunlit and shaded areas during clear weather conditions, with the highest values of Tmrt close to sunlit walls and the lowest values in the areas shaded by buildings and vegetation. As cloudiness increases, the spatial pattern is altered and the differences are reduced. The highest Tmrt under cloudy conditions is instead found in open areas where the proportion of shortwave diffuse radiation from the sky vault is high. A regional comparison between three Swedish coastal cities showed that Tmrt during summer is similar regardless of latitudinal location. On the other hand, large differences in Tmrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of Tmrt. However, extensive areas of shadow are usually not desired within outdoor urban environments at high latitude cities. One solution is to create diverse outdoor urban spaces in terms of shadow and also ventilation. This would provide individuals with access to a choice of thermal environments which they can use to assist their thermal regulation, based on personal needs and desires.

Greening in the circumpolar high-latitude may amplify warming in the growing season

We present a study that suggests greening in the circumpolar high-latitude regions amplifies surface warming in the growing season (May–September) under enhanced greenhouse conditions. The investigation used a series of climate simulations with the Community Atmospheric Model version 3—which incorporates a coupled, dynamic global vegetation model—with and without vegetation feedback, under both present and doubled CO2 concentrations. Results indicate that climate warming and associated changes promote circumpolar greening with northward expansion and enhanced greenness of both the Arctic tundra and boreal forest regions. This leads to additional surface warming in the high-latitudes in the growing season, primarily through more absorption of incoming solar radiation. The resulting surface and tropospheric warming in the high-latitude and Arctic regions weakens prevailing tropospheric westerlies over 45–70N, leading to the formation of anticyclonic pressure anomalies in the Arctic regions. These pressure anomalies resemble the anomalous circulation pattern during the negative phase of winter Arctic Oscillation. It is suggested that these circulation anomalies reinforce the high-latitude and Arctic warming in the growing season.

Climate Change Impact on Agricultural Water Resources Variability in the Northern Highlands of Ethiopia

Climate Change impact on Agricultural Water Resources Variability in the Northern Highlands of Ethiopia

Climate Change Impact on Water Resources and Adaptation Strategies in the Blue Nile River Basin

We compared projected changes in precipitation and temperature across global climate models (GCMs) for two future periods to get an indication of the consistency of the projected changes in the Lake Tana subbasin of the Blue Nile basin. We found that the models projected temperature increases of around 2 °C to 5 °C for 2080–2100, depending on the model and emission scenario. The interquartile ranges of the projected temperature increases for 2070–2100 for the three emission scenarios show 2.0−4.4 °C in the wet season and 2.2−4.9 °C in the dry season. The ensemble of GCMs we examined includes models that project increases and decreases in seasonal precipitation. The interquartile ranges of the projected rainfall changes for 2070–2100 for the three emission scenarios show − 13 to + 12 % in the wet season and − 14 to + 16 % in the dry season. The study investigated how changes in temperature and precipitation might translate into changes in streamflows and other hydrological components using downscaled outputs from different climate models. The direction of streamflow changes followed the direction of changes in rainfall. The responses of evapotranspiration, soil moisture (SW), and groundwater (GW) were also examined, and it was found that changes in GW flow may be a significant component of the changes in streamflow.

Can participants predict where ambulance-requiring cases occur at a half marathon?

Despite endurance races leading to a substantial number of ambulance‐requiring cases (ARC), little is known regarding where they occur, meaning that knowing where to place medical teams, ambulance pick‐up points, etc, is difficult. This article investigates whether the location of ARCs can be identified by race participants.

PA 13-2-0532 Testing a novel method for identifying where serious medical encounters occur at marathons in order to improve medical preparedness and runners’ safety

During the last decade, an increasing global popularity of endurance events has been seen, with a particular increase in the number of both half and full city marathons. Although events that promote physical activity are important, particularly from a public health perspective, endurance events also lead to a considerable number of medical emergencies. Despite this, very little is known regarding where serious life-threatening medical encounters (SLTMEs) occur during a race. Also, it is not known if the locations coincide with where runners experience the race as the most exhausting. Using the world’s largest half marathon (Gothenburg half marathon) as a case, SLTME data collected from the local ambulance provider (over 7 years), and data from runners’ experiences (n=237) is presented. Level of agreement tests are performed and, using the runners’ experiences as a template, specific high-risk clusters are presented. SLTMEs are shown to be considerably more common towards the end of the race and in uphill sections. By asking runners where they found the race most exhausting, it is possible to identify places where the risk of SLTMEs will be greater and thereby where medical personnel should be stationed. From a practical perspective, using this method could considerably increase the safety of competitors as well as improving the cost-effectiveness of safety interventions at endurance races.