This study focuses on how the treatment of the rainfall occurrences in bias correction (BC) contexts may affect the resulting precipitation, both in terms of occurrence and intensity. Three ...methodologies are compared—the “direct approach” (DA), the “Threshold Adaptation” approach (TA), and the “Positive Approach” (Pos)—as well as a method called “Singularity Stochastic Removal” (SSR) specifically developed for precipitation, all based on the same adjustment technique. Unlike the three other models, SSR allows dealing in the same way with the situations where the precipitation model has too many wet days or not with respect to the reference data. SSR also avoids separating the correction of the occurrence from that of the intensity, which constitutes a flexible tool. First, the four approaches are applied to a historical regional climate model precipitation run. Evaluations are realized through occurrence‐ and intensity‐related criteria. Although SSR, DA, and Pos may be close to each other depending on the criterion, in general, SSR provides the best results when all criteria are accounted for. This is even more true when the classical assumption that “the model precipitation had too many wet days” does not hold. The BC methods are also intercompared over the 2071–2100 period. The different BC methods are in agreement with previous studies, with relatively equivalent evolutions from 1976–2005 to 2071–2100, although nuances are present from one BC method to another. As a global conclusion, the SSR method for precipitation is a good compromise to correct both occurrences and intensities.
Key Points
Study on how the treatment of rain occurrence in bias correction affects occurrence and intensity
Bias correction method (SSR) specific to precipitation
Global conclusion: the SSR method is a good compromise to correct both occurrences and intensities
Abstract
Aircraft produce condensation trails, which are thought to increase high-level cloudiness under certain conditions. However the magnitude of such an effect and whether this contributes ...substantially to the radiative forcing due to the aviation sector remain uncertain. The very substantial, near-global reduction in air traffic in response to the COVID-19 outbreak offers an unprecedented opportunity to identify the anthropogenic contribution to the observed cirrus coverage and thickness. Here we show, using an analysis of satellite observations for the period March–May 2020, that in the 20% of the Northern Hemisphere mid-latitudes with the largest air traffic reduction, cirrus fraction was reduced by ∼9 ± 1.5% on average, and cirrus emissivity was reduced by ∼2 ± 5% relative to what they should have been with normal air traffic. The changes are corroborated by a consistent estimate based on linear trends over the period 2011–2019. The change in cirrus translates to a global radiative forcing of 61 ± 39 mW m
−2
. This estimate is somewhat smaller than previous assessments.
Two questions motivated this study: 1) Will meteorological droughts become more frequent and severe during the twenty-first century? 2) Given the projected global temperature rise, to what extent ...does the inclusion of temperature (in addition to precipitation) in drought indicators play a role in future meteorological droughts? To answer, we analyzed the changes in drought frequency, severity, and historically undocumented extreme droughts over 1981–2100, using the standardized precipitation index (SPI; including precipitation only) and standardized precipitation-evapotranspiration index (SPEI; indirectly including temperature), and under two representative concentration pathways (RCP4.5 and RCP8.5). As input data, we employed 103 high-resolution (0.44°) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), based on a combination of 16 global circulation models (GCMs) and 20 regional circulation models (RCMs). This is the first study on global drought projections including RCMs based on such a large ensemble of RCMs. Based on precipitation only, ∼15% of the global land is likely to experience more frequent and severe droughts during 2071–2100 versus 1981–2010 for both scenarios. This increase is larger (∼47% under RCP4.5, ∼49% under RCP8.5) when precipitation and temperature are used. Both SPI and SPEI project more frequent and severe droughts, especially under RCP8.5, over southern South America, the Mediterranean region, southern Africa, southeastern China, Japan, and southern Australia. A decrease in drought is projected for high latitudes in Northern Hemisphere and Southeast Asia. If temperature is included, drought characteristics are projected to increase over North America, Amazonia, central Europe and Asia, the Horn of Africa, India, and central Australia; if only precipitation is considered, they are found to decrease over those areas.
Ambitious climate change mitigation plans call for a significant increase in the use of renewables, which could, however, make the supply system more vulnerable to climate variability and changes. ...Here we evaluate climate change impacts on solar photovoltaic (PV) power in Europe using the recent EURO-CORDEX ensemble of high-resolution climate projections together with a PV power production model and assuming a well-developed European PV power fleet. Results indicate that the alteration of solar PV supply by the end of this century compared with the estimations made under current climate conditions should be in the range (-14%;+2%), with the largest decreases in Northern countries. Temporal stability of power generation does not appear as strongly affected in future climate scenarios either, even showing a slight positive trend in Southern countries. Therefore, despite small decreases in production expected in some parts of Europe, climate change is unlikely to threaten the European PV sector.
A global warming of 2 °C relative to pre-industrial climate has been considered as a threshold which society should endeavor to remain below, in order to limit the dangerous effects of anthropogenic ...climate change. The possible changes in regional climate under this target level of global warming have so far not been investigated in detail. Using an ensemble of 15 regional climate simulations downscaling six transient global climate simulations, we identify the respective time periods corresponding to 2 °C global warming, describe the range of projected changes for the European climate for this level of global warming, and investigate the uncertainty across the multi-model ensemble. Robust changes in mean and extreme temperature, precipitation, winds and surface energy budgets are found based on the ensemble of simulations. The results indicate that most of Europe will experience higher warming than the global average. They also reveal strong distributional patterns across Europe, which will be important in subsequent impact assessments and adaptation responses in different countries and regions. For instance, a North-South (West-East) warming gradient is found for summer (winter) along with a general increase in heavy precipitation and summer extreme temperatures. Tying the ensemble analysis to time periods with a prescribed global temperature change rather than fixed time periods allows for the identification of more robust regional patterns of temperature changes due to removal of some of the uncertainty related to the global models' climate sensitivity.
This is part of a research study addressing the potential co-benefits associated with selected black carbon (BC) emission reduction measures on mitigation of air pollution and climate forcing in ...Southeast Asia (SEA). This paper presents details of emission inventory (EI) results and WRF–CHIMERE model performance evaluation. The SEA regional emissions for 2007 were updated with our EI results for Indonesia, Thailand, and Cambodia and used for the model input. WRF–CHIMERE-simulated 2007 PM10, PM2.5, and BC over the SEA domain (0.25° × 0.25°) and the results were evaluated against the available meteorology and air quality monitoring data in the domain. WRF hourly simulation results were evaluated using the observed data at eight international airport stations in five SEA countries and showed a satisfactory performance. WRF–CHIMERE results for PM10 and PM2.5 showed strong seasonal influence of biomass open burning while the BC distribution showed the influence of urban activities in big SEA cities. Daily average PM10 constructed from the hourly concentrations were obtained from the automatic monitoring stations in three large SEA cities, i.e., Bangkok, Kuala Lumpur, and Surabaya, for model evaluation. The daily observed PM2.5 and BC concentrations obtained from the Improving Air Quality in Asian Developing Countries (AIRPET) project for four cities (i.e., Bangkok, Hanoi, Bandung, and Manila) were also used for model evaluation. In addition, hourly BC concentrations were taken from the measurement results of the Asian Pacific Network (APN) project at a suburban site in Bangkok. The modeled PM10 and BC satisfactorily met all suggested statistical criteria for PM evaluation. The modeled PM2.5∕PM10 ratios estimated for four AIRPET sites ranged between 0.47 and 0.59, lower than observed values of 0.6–0.83. Better agreement was found for BC∕PM2.5 ratios with the modeled values of 0.05–0.33 as compared to the observation values of 0.05–0.28. AODEM (extended aerosol optical depth module) was used to calculate the total columnar aerosol optical depth (AOD) and BC AOD up to the top of the domain at 500 hPa (∼ 5500 m), which did not include the free-tropospheric long-range transport of the pollution. The model AOD results calculated using the internal mixing assumption were evaluated against the observed AOD by both AERONET and MODIS satellite in 10 countries in the domain. Our model results showed that the BC AOD contributed 7.5–12 % of the total AOD, which was in the same range reported by other studies for places with intensive emissions. The results of this paper are used to calculate the regional aerosol direct radiative forcing under different emission reduction scenarios to explore potential co-benefits for air quality improvement, reduction in the number of premature deaths, and climate forcing mitigation in SEA in 2030 (Permadi et al., 2017a).
Climate change may alter the geographical pattern and intensity of near-surface winds which are the “fuel” for wind turbines. In a context of fast current and planned development of wind power ...worldwide, investigating the impacts of climate change on wind power generation is necessary. This study aims at assessing future changes in the potential for wind power generation over the whole Europe and in the effective wind power production from national wind farms operating at the end of 2012 and planned by 2020. For this purpose, a simplified wind power generation model is applied to an ensemble of 15 regional climate projections achieved from 10 Regional Climate Models downscaling six Global Climate Models under the SRES A1B emission scenario from the ENSEMBLES project. The use of a relatively large multi-model ensemble allows the identification of robust changes and the estimation of a range of uncertainties associated with projected changes. We show with a high level of confidence that, under the A1B scenario, over most of Europe, changes in wind power potential will remain within ±15 and ±20 % by mid and late century respectively. Overall, we find a tendency toward a decrease of the wind power potential over Mediterranean areas and an increase over Northern Europe. Changes in multi-year power production will not exceed 5 and 15 % in magnitude at the European and national scale respectively for both wind farms in operation at the end of 2012 and planned by 2020. Therefore, climate change should neither undermine nor favor wind energy development in Europe. However, accounting for climate change effects in particular regions may help optimize the wind power development and energy mix plans.
Attribution of extreme weather and climate-related events Stott, Peter A.; Christidis, Nikolaos; Otto, Friederike E. L. ...
Wiley interdisciplinary reviews. Climate change,
January/February 2016, Letnik:
7, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Extreme weather and climate‐related events occur in a particular place, by definition, infrequently. It is therefore challenging to detect systematic changes in their occurrence given the relative ...shortness of observational records. However, there is a clear interest from outside the climate science community in the extent to which recent damaging extreme events can be linked to human‐induced climate change or natural climate variability. Event attribution studies seek to determine to what extent anthropogenic climate change has altered the probability or magnitude of particular events. They have shown clear evidence for human influence having increased the probability of many extremely warm seasonal temperatures and reduced the probability of extremely cold seasonal temperatures in many parts of the world. The evidence for human influence on the probability of extreme precipitation events, droughts, and storms is more mixed. Although the science of event attribution has developed rapidly in recent years, geographical coverage of events remains patchy and based on the interests and capabilities of individual research groups. The development of operational event attribution would allow a more timely and methodical production of attribution assessments than currently obtained on an ad hoc basis. For event attribution assessments to be most useful, remaining scientific uncertainties need to be robustly assessed and the results clearly communicated. This requires the continuing development of methodologies to assess the reliability of event attribution results and further work to understand the potential utility of event attribution for stakeholder groups and decision makers. WIREs Clim Change 2016, 7:23–41. doi: 10.1002/wcc.380
This article is categorized under:
Paleoclimates and Current Trends > Detection and Attribution
Climate Models and Modeling > Knowledge Generation with Models
Many changes in European surface climate have occurred over the past decades, but most of the processes driving them are not identified. In particular, the role of atmospheric flow in driving surface ...trends needs to be evaluated to better predict future regional climate. We compare observed surface climate trends with those constructed from daily flow analogues. We find that during the last 60 years atmospheric circulation changes are the main drivers of surface weather trends in winter, but not in summer where temperature strongly interacts with the water cycle. For instance, increasing anticyclonic conditions control the decreasing summer rainfall frequency, but rainfall amount and cloud cover have not decreased accordingly, because individual rainfall events bring more rain now than decades ago. Over the past three decades the control by atmospheric flow changes has weakened, indicating evolutions in the processes steering European surface climate change.
Weather and climate extremes are identified as major areas necessitating further progress in climate research and have thus been selected as one of the World Climate Research Programme (WCRP) Grand ...Challenges. Here, we provide an overview of current challenges and opportunities for scientific progress and cross-community collaboration on the topic of understanding, modeling and predicting extreme events based on an expert workshop organized as part of the implementation of the WCRP Grand Challenge on Weather and Climate Extremes. In general, the development of an extreme event depends on a favorable initial state, the presence of large-scale drivers, and positive local feedbacks, as well as stochastic processes. We, therefore, elaborate on the scientific challenges related to large-scale drivers and local-to-regional feedback processes leading to extreme events. A better understanding of the drivers and processes will improve the prediction of extremes and will support process-based evaluation of the representation of weather and climate extremes in climate model simulations. Further, we discuss how to address these challenges by focusing on short-duration (less than three days) and long-duration (weeks to months) extreme events, their underlying mechanisms and approaches for their evaluation and prediction.
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