Sensitivity of Medium-Range Weather Forecasts to the Use of Reference Atmosphere

In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represented variables, temperature, geopotential height and orography, are replaced by their deviations from the reference atmosphere. Two modified semi- implicit schemes have been proposed to alleviate the computational instability due to the introduction of reference atmosphere. Concerning the deviation of surface geopotential height from reference atmosphere, an exact computational formulation has been used instead of the approximate one in the earlier work. To re duce aliasing errors in the computations of the deviation of the surface geopotential height, a spectral fit has been used slightly to modify the original Gaussian grid-point values of orography.A series of experiments has been performed in order to assess the impact of the reference atmosphere on ECMWF medium- range forecasts at the r     

A Response to the Letter of Da-Lin Zhang

We appreciate many of Zhang's critical comments and constructive recommendations(Zhang 2002) for the reform of Advances in Atmospheric Sciences (AAS). An annualAAS Editorial Board meeting was held on 19 December 2001 at the Institute of AtmosphericPhysics (IAP) of Chinese Academy of Sciences. Zhang's letter (Zhang 2002) was distributed to     

Progress of MJO Prediction at CMA from Phase I to Phase II of the Sub-Seasonal to Seasonal Prediction Project

As one of the participants in the Subseasonal to Seasonal(S2S) Prediction Project, the China Meteorological Administration(CMA) has adopted several model versions to participate in the S2S Project. This study evaluates the models’ capability to simulate and predict the Madden-Julian Oscillation(MJO). Three versions of the Beijing Climate Center Climate System Model(BCC-CSM) are used to conduct historical simulations and re-forecast experiments(referred to as EXP1, EXP1-M, and EXP2, respectively)...     

Correction to “the vertical distribution of climate forcings and feedbacks from the surface to top of atmosphere”

We discuss here a mistake in the analysis of Previdi and Liepert (Clim Dyn, 2011). In that article, the surface albedo radiative kernels were calculated incorrectly. We present in this brief comment the corrected albedo kernels. We then use these kernels to compute the surface albedo radiative feedback in climate model simulations driven by increasing carbon dioxide, as in Previdi and Liepert (Clim Dyn, 2011). We find that the use of the corrected albedo kernels does not change the conclusions of our earlier work.     

Are homeowners willing to adapt to and mitigate the effects of climate change?

The need to adapt to climate change impacts, whilst simultaneously limiting greenhouse gas emissions, requires that the government’s efforts are joined by public action. In England and Wales, housing contributes significantly to the emissions and many properties are at risk of flooding. This paper investigates the preparedness of homeowners in England and Wales to make changes to their homes in response to the predicted effects of climate change. A telephone survey of 961 homeowners investigated their interest in purchasing mitigation and adaptation improvements against their concern about climate change, awareness of flood risk and attribution of responsibility for action. Whilst the majority of homes had some energy-saving improvements, few were found to have property-level flood protection. The high levels of awareness about climate change and flooding were coupled with the perception of risks as low. Whilst some respondents accepted personal responsibility for action, most believed that the authorities were responsible for flood protection, and would not pay the costs required to make their home more energy-efficient and better prepared for the eventuality of floods. The results suggest that there is scope for further improvement of energy-saving measures, and that the levels of adoption of flood-protection measures are very low. Multi-faceted strategies, including more effective communication of risks and responsibilities, incentives, and material support for the poorest, will need to be developed to overcome the current reluctance by homeowners to invest in flood-protection measures and further energy conservation solutions in the future.     

The sensitivity of the Indian summer monsoon to a global warming of 2��C with respect to pre-industrial times

In this study the potential future changes in different aspects of the Indian summer monsoon associated with a global warming of 2°C with respect to pre-industrial times are assessed, focussing on the role of the different mechanisms leading to these changes. In addition, these changes as well as the underlying mechanisms are compared to the corresponding changes associated with a markedly stronger global warming exceeding 4.5°C, associated with the widely used SRES A1B scenario. The study is based on two sets of four ensemble simulations with the ECHAM5/MPI-OM coupled climate model, each starting from different initial conditions. In one set of simulations (2020?C2200), greenhouse gas concentrations and sulphate aerosol load have been prescribed in such a way that the simulated global warming dioes not exceed 2°C with respect to pre-industrial times. In the other set of simulations (1860?C2200), greenhouse gas concentrations and sulphate aerosol load have been prescribed according to observations until 2000 and according to the SRES A1B scenario after 2000. The study reveals marked changes in the Indian summer monsoon associated with a global warming of 2°C with respect to pre-industrial conditions, namely an intensification of the summer monsoon precipitation despite a weakening of the large-scale monsoon circulation. The increase in the monsoon rainfall is related to a variety of different mechanisms, with the intensification of the atmospheric moisture transport into the Indian region as the most important one. The weakening of the large-scale monsoon circulation is mainly caused by changes in the Walker circulation with large-scale divergence (convergence) in the lower (uppper) troposphere over the Indian Ocean in response to enhanced convective activity over the Indian Ocean and the central and eastern Pacific and reduced convective activity over the western tropical Pacific. These changes in the Walker circulation induce westerly (easterly) wind anomalies at lower (upper) level in the Indian region. The comparison with the changes in the Indian summer monsoon associated with a global warming of 4.5°C reveals that both the intensification of the monsoon precipitation and the weakening of the large-scale monsoon circulation (particularly in the lower troposphere) are relatively strong (with respect to the magnitude of the projected global warming by the end of the twentieth century for the two scenarios) in the scenario with a global warming of 2°C. The relatively strong intensification of the monsoon rainfall is related to rather strong increases in evaporation over the Arabian Sea and the Bay of Bengal, while a rather weak amplification of the meridional temperature gradient between the Indian Ocean and the land areas to the north contributes to the relatively strong reduction of the large-scale monsoon flow.     

Weapons of the vulnerable? A review of popular resistance to climate adaptation

Climate adaptation is not a neutral or apolitical process, but one that ignites social resistance. Government responses to risks of floods, droughts, or hurricanes – even those using a language of participation – might follow historical development pathways, strive to maintain the status quo, and directly or indirectly serve elite interests. Little attention has been paid to how people defy or resist top-down adaptation processes, overtly or covertly, in particular cultural, historical, and legal contexts. Drawing on sociological thought on popular resistance, this paper systematises research on people’s resistance to climate adaptation by scrutinising the sites, repertoires, and consequences of such resistance. We identified overt and covert resistance in 56 scientific adaptation articles, which concentrated on 5 ‘sites’ of resistance: Rural livelihoods, Urban informal settlements, Islands, First Nations, and Institutional landscapes. The findings imply that resistance to adaptation occurs globally, and not least in the context of relocation processes and participatory adaptation. We show how a resistance lens can help understand contemporary political behaviours, shed light on dynamic and compound vulnerability, and’unlock’ more context-sensitive and even transformative adaptation. Meanwhile, resistance and popular movements are not only progressive, and there might be conceptual barriers to moving from resistance to transformation or reconciling resistance with actions by or with the state.     

A social–ecological systems analysis of impediments to delivery of the Aichi 2020 Targets and potentially more effective pathways to the conservation of biodiversity

The Aichi 2020 Targets, under the Convention on Biological Diversity (CBD), aim to halt the loss of biodiversity by 2020, in order to ensure that ecosystems continue to provide essential services. Here we apply a social–ecological systems analysis to provide insight into the diverse system interactions that pose impediments to delivery of the Aichi Targets. We applied an analytical framework of pair-wise exchanges along six axes between the social, economic, environmental and political loci of the global social–ecological system. The analysis identified that many impediments result from partial decoupling in the system through phenomena including delayed feedbacks and insufficient information flows. It suggests 15 of the Aichi Targets are unlikely to be delivered; 3 are likely to be delivered in part; and 2 in full. We considered how interventions at leverage points may overcome the impediments, and compared these to actions included within the Implementation Decision for the Aichi Targets, to find gaps. These new leverage points to fill identified gaps involve many aspects of system re-coupling: co-production of knowledge and more equitable food systems governance (environmental–social axis); support for social change movements (social–political axis); an appropriate financial target for biodiversity conservation investment, with a clear means of implementation such as a currency transaction tax (economic–political axis); and co-governance of natural resources (environmental–political axis). The recently released Global Biodiversity Outlook 4 shows that 18 of the 20 Aichi Targets are tracking in accordance with our analysis; and that current efforts are unlikely to result in an improvement in the base state of biodiversity by 2020, confirming some of our results. We argue that attention to the interactions within, and the partial decoupling of, the global social–ecological system provides new insights, and is worthy of further attention both for delivery of the Aichi Targets and for guiding longer term actions for the conservation of biodiversity.     

Determinants of farmers’ choice of adaptation methods to climate change in the Nile Basin of Ethiopia

This study identifies the major methods used by farmers to adapt to climate change in the Nile Basin of Ethiopia, the factors that affect their choice of method, and the barriers to adaptation. The methods identified include use of different crop varieties, tree planting, soil conservation, early and late planting, and irrigation. Results from the discrete choice model employed indicate that the level of education, gender, age, and wealth of the head of household; access to extension and credit; information on climate, social capital, agroecological settings, and temperature all influence farmers’ choices. The main barriers include lack of information on adaptation methods and financial constraints.     

Application of the Hilbert–Huang Transform to the Estimation of Air-Sea Turbulent Fluxes

The Hilbert–Huang transform (HHT) is applied to analyzing the turbulent time series obtained within the atmospheric boundary layer over the ocean. A method based on the HHT is introduced to reduce the influence of non-turbulent motions on the eddy-covariance based flux by removing non-turbulent modes from the time series. The scale dependence of the flux is examined and a gap mode is identified to distinguish between turbulent modes and non-turbulent modes. To examine the effectiveness of this method it is compared with three conventional methods (block average, moving-window average, and multi-resolution decomposition). The data used are from three sonic anemometers installed on a moored buoy at about 6, 4 and 2.7 m height above the sea surface. For each method, along-wind and cross-wind momentum fluxes and sensible heat fluxes at the three heights are calculated. According to the assumption of a constant-flux layer, there should be no significant difference between the fluxes at the three heights. The results show that the fluxes calculated using HHT exhibit a smaller difference and higher correlation than the other methods. These results support the successful application of HHT to the estimation of air-sea turbulent fluxes.     

Response of the Intensity of Subtropical High in the Northern Hemisphere to Solar Activity

Using the intensity data of each northern subtropical high measured by monthly 500 hPa height charts for the recent 38 years (1954-1991), we calculate their correlations with the monthly sunspot number and monthly solar radio flux at 10.7 cm wave length, respectively. Through strict test, we further confirm a series of high correlations. Next, using a method called the non-integer (year) wave, the significant response of each subtropical high’s intensity to so-lar activity at its main period of 10.9-year length is found. Special attention is paid to that of the eastern Pacific high, the possible mechanism of such sensible response is also analysed.     

Modeling to evaluate the response of savanna-derived cropland to warming–drying stress and nitrogen fertilizers

Many savannas in West Africa have been converted to croplands and are among the world’s regions most vulnerable to climate change due to deteriorating soil quality. We focused on the savanna-derived cropland in northern Ghana to simulate its sensitivity to projected climate change and nitrogen fertilization scenarios. Here we show that progressive warming–drying stress over the twenty-first century will enhance soil carbon emissions from all kinds of lands of which the natural ecosystems will be more vulnerable to variation in climate variables, particularly in annual precipitation. The carbon emissions from all croplands, however, could be mitigated by applying nitrogen fertilizer at 30–60 kg N ha^???1 year^???1. The uncertainties of soil organic carbon budgets and crop yields depend mainly on the nitrogen fertilization rate during the first 40 years and then are dominated by climate drying stress. The replenishment of soil nutrients, especially of nitrogen through fertilization, could be one of the priority options for policy makers and farm managers as they evaluate mitigation and adaptation strategies of cropping systems and management practices to sustain agriculture and ensure food security under a changing climate.     

New Approach to Study the Evolution of Rossby Wave Packet

The average variational principle was employed in this paper to study the evolution of large-scale and slowly varying Rossby wave packet with basic flow both in barotropic and baroclinic atmospheres. The evolution of the structure of Rossby wave packet with both time and space was studied. The results obtained in this paper are similar to the results of by WKBJ method. In addition, the dispersive process of the wave packet was analysed by taking Gaussian type wave packet as an initial disturbance. The valid time scale for application of wave packet theory in the atmosphere was obtained.     

Sensitivity Experiments of an Eastward-Moving Southwest Vortex to Initial Perturbations

Whether the initial conditions contain pronounced mesoscale signals is important to the simulation of the southwest vortex. An eastward-moving southwest vortex is simulated using the PSU/NCAR MM5. A modest degree of success is achieved, but the most serious failure is that the formation and displacement of the simulated vortex in its early phase are about fourteen hours later than the observed vortex. Considering the relatively sparse data on the mesoscale vortex and in an attempt to understand the cause of the forecast failure, an adjoint model is used to examine the sensitivity of the southwest vortex to perturbations of initial conditions. The adjoint sensitivity indicates how small perturbations of model variables at the initial time in the model domain can influence the vortex. A large sensitivity for zonal wind is located under 400 hPa, a large sensitivity for meridional wind is located under 500 hPa, a large sensitivity for temperature is located between 500 and 900 hPa, and almost all of the large sensitivity areas are located in the southwestern area. Based on the adjoint sensitivity results, perturbations are added to initial conditions to improve the simulation of the southwest vortex. The results show that the initial conditions with perturbations can successfully simulate the formation and displacement of the vortex; the wind perturbations added to the initial conditions appear to be a cyclone circulation under the middle level of the atmosphere in the southwestern area with an anticyclone circulation to its southwest; a water vapor perturbation added to initial conditions can strengthen the vortex and the speed of its displacement.     

Adaptation of California’s electricity sector to climate change

Climate change is likely to pose considerable new challenges to California’s electricity sector. This paper primarily focuses on the adaptation challenges of an important component of the energy arena: electricity demand in the residential and commercial sectors and electricity supply. The primary challenge to California’s electricity sector will likely be the increase in demand for air conditioning as a result of rising temperatures. In addition, renewable energy sources, which are an increasing share of the electricity portfolio, are particularly vulnerable to climate change. Many of the key players have been actively considering the implications of climate change. Because electricity generation accounts for nearly 30% of greenhouse gas emissions, this sector has been a target of the state’s efforts to reduce emissions. Fortunately, many of the same tools can simultaneously improve the sector’s resilience to a changing climate. Demand management strategies and supply diversification are both important strategies. Local governments can play a central role in encouraging the adoption of more energy efficient building codes and the use of more renewable sources, such as solar energy. The positive steps taken by many local governments are encouraging. Steps to increase public awareness are an important, often missing component, however. Increases in research, development, and demonstration to improve system resiliency and develop new energy conservation tools are also needed.     

Advancing the use of scenarios to understand society’s capacity to achieve the 1.5 degree target

With a range of potential pathways to a sustainable future compatible with the Paris Agreement 1.5 °C target, scenario analysis has emerged as a key tool in studies of climate change mitigation and adaptation. A wide range of alternative scenarios have been created, and core amongst these are five socio-economic scenarios (Shared Socio-economic Pathways or SSPs) and four emission scenarios (Representative Concentration Pathways or RCPs). Whilst mitigation scenarios (the Shared Policy Assumptions, or SPAs) have been developed for each SSP-RCP combination, describing the actions necessary to match the climate pathway of the RCP, there has not yet been a systematic approach to address whether and how these actions can be enabled in practice.We present a novel and transferable framework to understand society’s capacity to achieve the 1.5 °C target, based on four participatory case studies using the SSP-RCP scenarios. The methodology builds on a framework for categorising different types of societal capitals and capacities and assessing their impact on the potential to implement different types of mitigation actions. All four case studies show that SSP1 has the highest potential to reach the target. Although environmental awareness is high in both SSP1 and SSP4, continued social inequalities in SSP4 restrict society’s capacity to transform, despite economic growth. In the two least environmentally-aware SSPs, SSP3 and SSP5, the transformation potential is low, but the view on capitals and capacities nonetheless helps identify opportunities for actors to develop and implement mitigation actions.The study highlights that techno-economic assessments of climate strategies need to be complemented by consideration of the critical role played by social and human capital, and by societal capacity to mobilise and create these capitals despite different socio-economic trends. These capitals and capacities are essential to enable the rapid innovation, behavioural change and international co-ordination needed to achieve the 1.5 °C target.