| 1. |
- Aminipouri, M., et al.
(författare)
-
Urban tree planting to maintain outdoor thermal comfort under climate change: The case of Vancouver's local climate zones
- 2019
-
Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323. ; 158, s. 226-236
-
Tidskriftsartikel (refereegranskat)abstract
- Spatiotemporal variation of mean radiant temperature (Tmrt), a major driver of outdoor human thermal comfort, is driven by exposure to solar and longwave radiation, which in turn respond to local patterns of shading, wind speed, air humidity and air temperature. In this study, the SOlar and LongWave Environmental Irradiance Geometry (SOLWEIG) model was used to simulate how changes in minimum and maximum air temperature and solar radiation under Representative Concentration Pathways (RCP) 4.5 and 8.5 climate projections would change Tmrt in Vancouver over the 2070-2100 period. With micrometeorological variables representative of a changed climate, days with Tmrt above 65 degrees C were predicted to increase three-to five-fold under RCP 4.5 and 8.5, respectively. SOLWEIG was also used to quantify the potential of maximum feasible street tree cover to reduce Tmrt for the hottest day on record for Vancouver (July 29, 2009), and an end-of-century hot day under the two future climate scenarios. SOLWEIG simulations with maximum feasible street tree cover under RCP 4.5 demonstrated an average reduction of 1.3 degrees C in Tmrt, compared to the contemporary extreme heat day with current street trees. However, average Tmrt increased by 1.9 degrees C under the RCP 8.5 scenario even with maximum feasible street tree cover, relative to the contemporary extreme heat day. We conclude that adding street trees has the potential to offset Tmrt increases under the RCP 4.5 scenario, however this measure is insufficient to maintain contemporary Tmrt under the RCP 8.5 scenario.
|
|
| 2. |
- Andersson-Sköld, Yvonne, et al.
(författare)
-
An integrated method for assessing climate-related risks and adaptation alternatives in urban areas
- 2015
-
Ingår i: Climate Risk Management. - : Elsevier BV. - 2212-0963. ; 7, s. 31-50
-
Tidskriftsartikel (refereegranskat)abstract
- © 2015 The Authors. The urban environment is a complex structure with interlinked social, ecological and technical structures. Global warming is expected to have a broad variety of impacts, which will add to the complexity. Climate changes will force adaptation, to reduce climate-related risks. Adaptation measures can address one aspect at the time, or aim for a holistic approach to avoid maladaptation. This paper presents a systematic, integrated approach for assessing alternatives for reducing the risks of heat waves, flooding and air pollution in urban settings, with the aim of reducing the risk of maladaptation. The study includes strategies covering different spatial scales, and both the current climate situation and the climate predicted under climate change scenarios. The adaptation strategies investigated included increasing vegetation; selecting density, height and colour of buildings; and retreat or resist (defend) against sea-level rise. Their effectiveness was assessed with regard to not only flooding, heat stress and air quality but also with regard to resource use, emissions to air (incl. GHG), soil and water, and people's perceptions and vulnerability. The effectiveness of the strategies were ranked on a common scale (from -3 to 3) in an integrated assessment. Integrated assessments are recommended, as they help identify the most sustainable solutions, but to reduce the risk of maladaptation they require experts from a variety of disciplines. The most generally applicable recommendation, derived from the integrated assessment here, taking into account both expertise from different municipal departments, literature surveys, life cycle assessments and publics perceptions, is to increase the urban greenery, as it contributes to several positive aspects such as heat stress mitigation, air quality improvement, effective storm-water and flood-risk management, and it has several positive social impacts. The most favourable alternative was compact, mid-rise, light coloured building design with large parks/green areas and trees near buildings.
|
|
| 3. |
- Bartolino, Valerio, et al.
(författare)
-
Forecasting fish stock dynamics under climate change: Baltic herring (Clupea harengus) as a case study
- 2014
-
Ingår i: Fisheries Oceanography. - : Wiley. - 1054-6006 .- 1365-2419. ; 23:3, s. 258-269
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change and anthropogenic disturbances may affect marine populations and ecosystems through multiple pathways. In this study we present a framework in which we integrate existing models and knowledge on basic regulatory processes to investigate the potential impact of future scenarios of fisheries exploitation and climate change on the temporal dynamics of the central Baltic herring stock. Alternative scenarios of increasing sea surface temperature and decreasing salinity of the Baltic Sea from a global climate model were combined with two alternative fishing scenarios, and their direct and ecosystem-mediated effects (i.e., through predation by cod and competition with sprat) on the herring population were evaluated for the period 2010-2050. Gradual increase in temperature has a positive impact on the long-term productivity of the herring stock, but it has the potential to enhance the recovery of the herring stock only in combination with sustainable fisheries management (i.e., F-msy). Conversely, projections of herring spawning stock biomass (SSB) were generally low under elevated fishing mortality levels (F-high), comparable with those experienced by the stock during the 1990s. Under the combined effects of long-term warming and high fishing mortality uncertainty in herring SSB projections was higher and increasing for the duration of the forecasts, suggesting a synergistic effect of fishery exploitation and climate forcing on fish populations dynamics. Our study shows that simulations of long-term fish dynamics can be an informative tool to derive expectations of the potential long-term impact of alternative future scenarios of exploitation and climate change.
|
|
| 4. |
- Gebregiorgis, Daniel, et al.
(författare)
-
Does the IOD independently influence seasonal monsoon patterns in Northern Ethiopia?
- 2019
-
Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 10:8
-
Tidskriftsartikel (refereegranskat)abstract
- The dominant large-scale interannual modes in the tropical Pacific and Indian Oceans-El Niño southern oscillation (ENSO) and the Indian Ocean Dipole (IOD)-dominate seasonal rainfall patterns in Ethiopia. However, there is a clear interaction between ENSO and the IOD, and it is unclear whether the IOD has an independent influence on seasonal monsoon patterns in Northern Ethiopia. We use monthly rainfall records from 15 stations from two drought-prone regions in Northern Ethiopia (Afar and Amhara) for the period 1966-2006 to explore relationships between rainfall and circulation patterns and sea surface temperature (SST) anomalies over the tropical Indo-Pacific region. Our analysis confirms that regional summer monsoon (Kiremt) rainfalls in these regions are predominantly modulated by ENSO.Warm and cold ENSO episodes (El Niño/La Nina) are associated with below and above average summer monsoon rainfall, respectively. Lagged relationship between the IOD and Kiremt rainfall shows that positive/negative phases of the IOD are generally conducive to Kiremt rainfall increases/decreases over large parts of Ethiopia. Regression models based on the large-scale circulation indices NINO3.4 and a Dipole Mode Index (DMI)NO-ENSO representing the "ENSO-free IOD" also highlight the role of ENSO. However, the relative-weights for the models with DMINO-ENSO, calculated using Akaike Information Criteria (AIC), were 1.5 and 1.1 times the weights for the ENSO only models for the Afar and Amhara regions, respectively. This suggests that the IOD has an independent regional influence. This is in line with the conception of the IOD as a unique coupled-mode in the tropics, and may have important implications in boosting seasonal forecasting skills in the regions. No statistically significant trends were found in the regional and modeled rainfall time-series.
|
|
| 5. |
- Gustafsson, Malin, et al.
(författare)
-
Extreme rainfall events in Southern Sweden: Where does the moisture come from?
- 2010
-
Ingår i: Tellus A. - : Stockholm University Press. - 0280-6495. ; 62:5, s. 605-616
-
Tidskriftsartikel (refereegranskat)abstract
- The atmospheric transport of moisture leading to extreme summer precipitation events in southern Sweden was investigated using a Lagrangian trajectory model. Surprisingly, we found that the trajectories crossed continental Europe and the Baltic Sea before arriving over Sweden; they did not arrive directly from the North Sea. Such transport pathways were not seen for a control sample of non-extreme rainfall events. We then used a new source region identification technique to investigate the hypothesis that Europe and the Baltic are important sources of the moisture that is rained out in the extreme events. Although the results varied between events, we found that this is indeed the case. Our results establish the atmospheric transport patterns that are apparently a pre-requisite for extreme rainfall events to occur in southern Sweden, and further suggest regional moisture availability may also play a key role.
|
|
| 6. |
- Holmer, Björn, 1943, et al.
(författare)
-
How to transform the standing man from a box to a cylinder – a modified methodology to calculate mean radiant temperature in field studies and models
- 2015
-
Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July, Toulouse, France.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mean radiant temperature (Tmrt) has shown to be an important meteorological variable in studies of human comfort and health. The Tmrt is calculated as the surface temperature of a standing man approximated as a cylinder emitting the same amount of longwave radiation as all short- and longwave radiation fluxes received from the surrounding four cardinal points and down- and upwards. The calculation was introduced by Höppe in 1992 and has then been used both in models (e.g. SOLWEIG) and field studies. However, the formula by Höppe describes in fact a man shaped like a box and not a cylinder, which has resulted in some peculiar features noticed in studies of Tmrt such as a secondary daytime minimum and an influence of the orientation of the field equipment. A methodology to change the box man to a cylindrical man is proposed. It will remove the peculiarities that have been observed in earlier studies. The methodology is based on the partition of the observed shortwave fluxes in direct and diffuse radiation. The minimum shortwave radiation of the four cardinal points is used as diffuse radiation since it is monitored by a sensor that is not sunlit. By subtraction of this quantity the horizontal direct fluxes are obtained. Calculation of the resultant flux of the sunlit sensors and adjustment for solar angle gives the direct shortwave radiation. The surface of the standing man (as a cylinder) perpendicular to the direct radiation must be determined and the direct shortwave radiation received by the standing man can be calculated. Then the sum of the shortwave fluxes can be calculated. The diffuse and longwave fluxes can be calculated according to the Höppe formula since they differ little with direction. In the SOLWEIG model the direct shortwave radiation is used as an input. Thus the calculation according to the new methodology is easy to apply, only the solar position needs to be added. The new methodology is tested by model calculations with SOLWEIG and field studies in both high-latitude Gothenburg, Sweden and low-latitude Ouagadougou, Burkina Faso. The secondary minimum disappears. In Gothenburg at a site with SVF=0.95 the noon depression of Tmrt by the Höppe formula was about 2 °C and there was an overestimation of 1.5-1.7 °C two-three hours before and after noon.differences in summer. In Ouagadougou data from an open site (SVF=0.83) in the dry season the differences were slightly smaller. Sites with lower SVF and much reflected direct shortwave radiation differed less from the Tmrt obtained with the Höppe formula.
|
|
| 7. |
- Jeong, Jee-Hoon, 1976, et al.
(författare)
-
Greening in the circumpolar high-latitude may amplify warming in the growing season
- 2012
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 38:7-8, s. 1421-1431
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 8. |
- Lau, Kevin Ka-Lun, 1983, et al.
(författare)
-
The effect of urban geometry on mean radiant temperature under future climate change: a study of three European cities
- 2015
-
Ingår i: International journal of biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 59:7, s. 799-814
-
Tidskriftsartikel (refereegranskat)abstract
- Future anthropogenic climate change is likely to increase the air temperature (T a ) across Europe and increase the frequency, duration and magnitude of severe heat stress events. Heat stress events are generally associated with clear-sky conditions and high T a , which give rise to high radiant heat load, i.e. mean radiant temperature (T mrt ). In urban environments, T mrt is strongly influenced by urban geometry. The present study examines the effect of urban geometry on daytime heat stress in three European cities (Gothenburg in Sweden, Frankfurt in Germany and Porto in Portugal) under present and future climates, using T mrt as an indicator of heat stress. It is found that severe heat stress occurs in all three cities. Similar maximum daytime T mrt is found in open areas in all three cities despite of the latitudinal differences in average daytime T mrt . In contrast, dense urban structures like narrow street canyons are able to mitigate heat stress in the summer, without causing substantial changes in T mrt in the winter. Although the T mrt averages are similar for the north–south and east–west street canyons in each city, the number of hours when T mrt exceeds the threshold values of 55.5 and 59.4 °C—used as indicators of moderate and severe heat stress—in the north–south canyons is much higher than that in the east–west canyons. Using statistically downscaled data from a regional climate model, it is found that the study sites were generally warmer in the future scenario, especially Porto, which would further exacerbate heat stress in urban areas. However, a decrease in solar radiation in Gothenburg and Frankfurt reduces T mrt in the spring, while the reduction in T mrt is somewhat offset by increasing T a in other seasons. It suggests that changes in the T mrt under the future scenario are dominated by variations in T a . Nonetheless, the intra-urban differences remain relatively stable in the future. These findings suggest that dense urban structure can reduce daytime heat stress since it reduces the number of hours of high T mrt in the summer and does not cause substantial changes in average and minimum T mrt in the winter. In dense urban settings, a more diverse urban thermal environment is also preferred to compensate for reduced solar access in the winter. The extent to which the urban geometry can be optimized for the future climate is also influenced by local urban characteristics.
|
|
| 9. |
- Lindberg, Fredrik, 1974, et al.
(författare)
-
Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications
- 2014
-
Ingår i: International Journal Of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 58:5, s. 613-627
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of how the mean radiant temperature (T mrt ) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how T mrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of T mrt 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 T mrt 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 T mrt 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 T mrt during summer is similar regardless of latitudinal location. On the other hand, large differences in T mrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of T mrt . 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.
|
|
| 10. |
- Lindberg, Fredrik, 1974, et al.
(författare)
-
The impact of urban planning strategies on heat stress in a climate-change perspective
- 2016
-
Ingår i: Sustainable Cities and Society. - : Elsevier BV. - 2210-6707. ; 25, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal characteristics of outdoor heat stress for a redevelopment area in Gothenburg, Sweden, in a climate change perspective, using mean radiant temperature (Tmrt) as a proxy for heat stress are presented. The impact of climate change on Tmrt was evaluated using statistically downscaled data from a regional climate model. The simulated average Tmrt for the future scenarios was not higher than for today’s climate, because the increased longwave radiation fluxes caused by higher temperatures were offset by reduced shortwave radiation fluxes caused by increased cloudiness. The spatial pattern of Tmrt in the study area during warm and clear weather is primarily governed by the shadow patterns of buildings and vegetation. The highest average-daytime Tmrt was found at open locations, but because open areas also have the highest frequency of sunlit occasions, this does not necessarily imply that open areas are most prone to heat-stress. When considering only occasions during clear and warm weather situations, the highest Tmrt were usually found close to sun-exposed, south-facing walls. Under these criteria, denser urban environments have lower heat stress than more open urban environments. The warmest areas were also found to be the warmest areas in the future as well. Tree-shadows are an effective measure to reduce daytime Tmrt. Trees was found to have the largest impact on Tmrt in open areas where vegetation is sparse, especially when the distance to the nearest “cool” place is used as a measure of heat-stress.
|
|
