Direct cloud water recovery by inertial impaction: Implications for large scale water supply in the Cape Verde Islands

Summary In this study, we explore the idea of harvesting cloud water in mountainous areas of the drought prone Cape Verde Islands as a year-round fresh water resource based on three cloud water collection experiments in the islands. Cloud water was collected by impaction on a commercially available, plastic, agricultural shade cloth at Serra Malagueta, Santiago, and at Monte Verde, São Vicente. This shade screen possesses superior properties to other reported materials for cloud water collection, including an impact-efficient mesh shape, high tensile strength and durability, tear resistance, and excellent water drainage characteristics. Collection efficiency of monofilament knitted shade screen varied with the mesh density (50% or 70% shading) and height of the screens, but for Monte Verde all screens above 3 m collected greater than 6 lm^–2 day^–1 on average for 315 days of measurement. Dry season collection for the most effective panel, a double layer of 50% shading screen, ranged from 1.3 lm^–2 day^–1 in December, 1988, to 7.8 and 7.7 lm^–2 day^–1 in November and April, 1988 respectively. Based on these measurements, we discuss a logical next phase for implementation of a large scale cloud water catchment system.With 3 Figures     

上海地区高温过程中局地气候区尺度城市热岛特征分析

本文以超大城市上海为研究对象,选取2017年7月为夏季代表月,利用自动气象站网观测得到的逐小时气温和风速数据,基于局地气候分区方法分析了上海市各局地气候区(Local Climate Zone,LCZ)在不同天气条件下的气温和城市热岛强度(Urban Heat Island Intensity,UHII)时空特征及其成因。结果表明:由于城市几何形态、建筑材料、表面不透水面占比以及人类活动的不同,上海市夏季典型月各LCZ的气温和UHII表现出明显差异,在高温日,UHII日变化曲线可以分为"W "型、浅" U"型、"V"型、日间型和平稳型这五类。城市建筑形态对城市风、热环境具有较为复杂的影响,UHII与天空可视因子(Sky View Factor,SVF)的相关系数在00时(北京时,下同)为负,而在12、16时为正,这是由于建筑物对城市冠层内的辐射传输的影响和建筑物的热量储存导致的;城乡风速之比与SVF在00、12和16时都为正相关,说明了高大密集的建筑物对风速有衰减作用,同时风速通过影响大气的平流输送进一步影响UHII。     

Modelling the spatial and temporal distribution of rainfall intensity at local scale

Summary Accurate estimates of rainfall intensity distribution with high temporal and spatial resolution are necessary in most urban hydrological studies, such as planning, simulation or control of sewer networks. Traditionally, these data are obtained from intensity-duration-frequency (IDF) curves at sites with long rainfall intensity time-series, however, little attention is given to the spatial features of precipitation. In this paper, a mathematical model of a local scale storm that takes account of the spatial variability of rainfall and rain-cell movement is proposed. The model has been calibrated with a dense network of raingauges and a long rainfall intensity timeseries (60 years) and its parameters have been calculated for convective storms of return periods up to 15 years with their most frequently-observed rain-cell velocities (1 to 4 m/s).This work has been supported by the DGICYT, Project NAT91-0596.With 6 Figures     

Progress in the scale modeling of urban climate: Review

Summary This paper describes progress made in the scale modeling of urban climate. The studies reviewed are mainly indoor and outdoor experiments that use an array of urban-like flow obstacles or roughness elements such as cubes, blocks, and cylinders. Except for several important and unique studies, the many experiments that use a single obstacle, or those that use an array of elements to create a vegetation-like roughness are excluded from this review. Topics considered include turbulent flow, scalar dispersion, local transfer coefficient, radiative transfer, and the surface energy balance. More than 40 relevant studies are cited, and both significant developments and remaining problems are described. The future application of scale models to obtain a comprehensive understanding of urban climate is also examined, with the focus mainly upon the possibility of outdoor experiments.     

Secular spring rainfall variability at local scale over Ethiopia: trend and associated dynamics

Spring rainfall secular variability is studied using observations, reanalysis, and model simulations. The joint coherent spatio-temporal secular variability of gridded monthly gauge rainfall over Ethiopia, ERA-Interim atmospheric variables and sea surface temperature (SST) from Hadley Centre Sea Ice and SST (HadISST) data set is extracted using multi-taper method singular value decomposition (MTM-SVD). The contemporaneous associations are further examined using partial Granger causality to determine presence of causal linkage between any of the climate variables. This analysis reveals that only the northwestern Indian Ocean secular SST anomaly has direct causal links with spring rainfall over Ethiopia and mean sea level pressure (MSLP) over Africa inspite of the strong secular covariance of spring rainfall, SST in parts of subtropical Pacific, Atlantic, Indian Ocean and MSLP. High secular rainfall variance and statistically significant linear trend show consistently that there is a massive decline in spring rain over southern Ethiopia. This happened concurrently with significant buildup of MSLP over East Africa, northeastern Africa including parts of the Arabian Peninsula, some parts of central Africa and SST warming over all ocean basins with the exception of the ENSO regions. The east-west pressure gradient in response to the Indian Ocean warming led to secular southeasterly winds over the Arabian Sea, easterly over central Africa and equatorial Atlantic. These flows weakened climatological northeasterly flow over the Arabian Sea and southwesterly flow over equatorial Atlantic and Congo basins which supply moisture into the eastern Africa regions in spring. The secular divergent flow at low level is concurrent with upper level convergence due to the easterly secular anomalous flow. The mechanisms through which the northwestern Indian Ocean secular SST anomaly modulates rainfall are further explored in the context of East Africa using a simplified atmospheric general circulation model (AGCM) coupled to mixed-layer oceanic model. The rainfall anomaly (with respect to control simulation), forced by the northwestern Indian Ocean secular SST anomaly and averaged over the 30-year period, exhibits prevalence of dry conditions over East and equatorial Africa in agreement with observation. The atmospheric response to secular SST warming anomaly led to divergent flow at low levels and subsidence at the upper troposphere over regions north of 5^° S on the continent and vice versa over the Indian Ocean. This surface difluence over East Africa, in addition to its role in suppressing convective activity, deprives the region of moisture supply from the Indian Ocean as well as the Atlantic and Congo basins.     

Simultaneous measurements of ozone and its precursors on a diurnal scale at a semi urban site in India

Simultaneous observations of surface ozone (O₃) with its precursors namely, carbon monoxide (CO) and oxides of nitrogen (NO_x) have been taken on diurnal scale from a tropical semi-urban site, Pune (18.54°N, 73.81°E) in India. We present the data for one year (2003–2004) period to study the salient features of these trace gases. The peak in amplitude of ozone is found during the noontime whereas in CO and NO_X it is observed in the morning hours between 0800 and 0900 H. The concentration of these pollutants drop down considerably during southwest monsoon months and the diurnal pattern also become very weak. The diurnal trends of these gases are found to be different for different seasons, which are specific to the receptor site. Model simulations using 3-D chemical-transport model with regional emission inventories and observed winds have also been carried out. The comparison of model results with observations, on seasonal basis yielded a reasonable qualitative agreement. The relative role of local emissions and long range transport in the diurnal pattern for different seasons has been outlined, which reveals that the ozone is highly influenced by regional/long range transport in this region. The effect of precursor amounts in the morning on afternoon ozone peak levels has been investigated using the lag correlation study, which reveals that a time lag of 5–7 h is required for most of these precursor gases to photo-chemically produce ozone to its maximum potential. Results are discussed in the light of available topographic and meteorological conditions.     

Rainfall rate distribution in a local scale: The case of Barcelona city

Summary Convective rainfall rate distribution is not very uniform even at a local scale. In order to make an evaluation of it in the urban area of Barcelona, a dense rain gauge network has been stablished in this city. The gauges are of high resolution tilting bucket type. In this paper, preliminary results are presented. The distributions obtained show a strong variation of the rainfall rate for the several parts of the city. The intensity-duration curves for severe storms have been made in the various points of measure together with the areal reduction factors of rainfall. The analysis of raincell movement gives E-W as a predominant direction and a speed in the 3–12 m/s range.With 9 Figures     

云分辨尺度下一种综合调整水物质含量的闪电资料同化方法

在直接调整水汽含量（称为F12）和直接调整冰相粒子浓度（称为Q14）两种闪电资料同化方法的基础上,提出了一种综合调整冰相粒子浓度和水汽含量（称为C17）的闪电资料同化方法,选取一次具有完整闪电观测资料（云闪加地闪）的飑线过程,利用WRF在云分辨尺度进行数值模拟,详细比较了3种闪电资料同化方法的模拟结果。与不进行闪电资料同化的控制试验相比,闪电资料同化试验明显改进了模式对流活动的模拟能力,但是不同同化方法有所差异。在同化时段内,F12方法中回波强度较小,形成大范围层云区,回波中心比实测偏向下游;Q14方法回波强度和落区同实测最为接近,但是对层云区的模拟无明显改进;C17方法综合了F12和Q14方法的优势,与F12方法相比,回波强度增大,落区更加接近实测,层云区面积扩大。同化结束后,F12方法冷池有所增强,雨区向东北方向延伸,但是强度较弱,形成大范围的弱降水区,同化正面效果保持最久;Q14方法低层大气偏干,地表冷池偏强,对流系统迅速移动并衰减,降水区域比实测偏南,同化正面效果消失较快;C17方法冷池范围和强度与实际观测最为接近,降水较F12方法增强,模拟出的飑线形态得到调整,模拟出了实测中的另一降水中心,同化正面效果保持时间延长。      

Estimation of precipitable water at different locations using surface dew-point

Summary The Reitan (1963) regression equation of the form lnw =a +bT _d has been examined and tested to estimate precipitable water vapor content from the surface dew point temperature at different locations. The results of this study indicate that the slopeb of the above equation has a constant value of 0.0681, while the intercepta changes rapidly with latitude. The use of the variable intercept technique can improve the estimated result by about 2%.With 6 Figures     

Effects of local drought condition on public opinions about water supply and future climate change

A growing body of research indicates that opinions about long-term climate change and other natural resource issues can be significantly affected by current weather conditions (e.g., outside air temperature) and other highly contingent environmental cues. Although increased severity and frequency of droughts is regarded as a likely consequence of anthropogenic climate change, little previous research has attempted to relate the experience of drought with public attitudes about water supply or water-related climate change issues. For this study, a large set (n?=?3,163) of public survey data collected across nine states of the southern United States was spatio-temporally linked with records of short-term (~12 weeks) and long-term (~5 years) drought condition at the level of each respondent’s zip code. Multivariate ordinal logistic regression models that included numerous other independent variables (environmental ideology, age, gender, education, community size, residency duration, and local annual precipitation) indicated highly significant interactions with long-term drought condition, but showed no significant effect from short-term drought condition. Conversely, attitudes about water-related climate change showed highly significant interactions with short-term drought, with weaker to no effects from long-term drought. While the finding of significant effects from short-term drought condition on opinions about future drought is broadly consistent with previous public opinion research on climate change, the finding of water supply attitudes being more responsive to longer term drought condition is, to our knowledge, a novel result. This study more generally demonstrates the methodological feasibility and applied importance of accounting for local drought condition when public opinion information is used to evaluate outreach programs for water conservation and climate change.     

A hybrid approach to improving the skills of seasonal climate outlook at the regional scale

A hybrid seasonal forecasting approach was generated by the National Centers for Environmental Prediction operational Climate Forecast System (CFS) and its nesting Climate extension of Weather Research and Forecasting (CWRF) model to improve forecasting skill over the United States. Skills for the three summers of 2011–2013 were evaluated regarding location, timing, magnitude, and frequency. Higher spatial pattern correlation coefficients showed that the hybrid approach substantially improved summer mean precipitation and 2-m temperature geographical distributions compared with the results of the CFS and CWRF models. The area mean temporal correlation coefficients demonstrated that the hybrid approach also consistently improved the timing prediction skills for both variables. In general, the smaller root mean square errors indicated that the hybrid approach reduced the magnitude of the biases for both precipitation and temperature. The greatest improvements were achieved when the individual models had similar skills. The comparison with a North American multi-model ensemble further proved the feasibility of improving real-time seasonal forecast skill by using the hybrid approach, especially for heavy rain forecasting. Based on the complementary advantages of CFS the global model and CWRF the nesting regional model, the hybrid approach showed a substantial enhancement over CFS real-time forecasts during the summer. Future works are needed for further improving the quality of the hybrid approach through CWRF’s optimized physics ensemble, which has been proven to be feasible and reliable.     

Water on an urban planet: Urbanization and the reach of urban water infrastructure

Urban growth is increasing the demand for freshwater resources, yet surprisingly the water sources of the world's large cities have never been globally assessed, hampering efforts to assess the distribution and causes of urban water stress. We conducted the first global survey of the large cities’ water sources, and show that previous global hydrologic models that ignored urban water infrastructure significantly overestimated urban water stress. Large cities obtain 78 ± 3% of their water from surface sources, some of which are far away: cumulatively, large cities moved 504 billion liters a day (184 km³ yr⁻¹) a distance of 27,000 ± 3800 km, and the upstream contributing area of urban water sources is 41% of the global land surface. Despite this infrastructure, one in four cities, containing $4.8 ± 0.7 trillion in economic activity, remain water stressed due to geographical and financial limitations. The strategic management of these cities’ water sources is therefore important for the future of the global economy.     

Case study of urban interactions with a synoptic scale cold front

Summary A two-day test period (10–11 March 1966) during which a slow moving synoptic cold front passed over New York City has been analyzed. As the front passed over the city it was destroyed near the surface by the urban roughness effect. The upper segment of the front passed over the city and rejoined the rest of the front downwind of the city. Evidence for the above phenomenon was seen in both the pibal wind and helicopter (temperature and SO₂) soundings.Distortion of the front forced polluted surface urban air upwards, as within the warm sector of an occluding synoptic frontal system. The outward spreading of this air aloft produced increasing concentrations over the city at heights above 200 m.With 7 Figures     

An assessment of the climate change impacts on groundwater recharge at a continental scale using a probabilistic approach with an ensemble of GCMs

This study used 16 Global Climate Models and three global warming scenarios to make projections of recharge under a 2050 climate for the entire Australian continent at a 0.05° grid resolution. The results from these 48 future climate variants have been fitted to a probability distribution to enable the results to be summarised and uncertainty quantified. The median results project a reduction in recharge across the west, centre and south of Australia and an increase in recharge across the north and a small area in the east of the continent. The range of results is quite large and for large parts of the continent encompasses both increases and decreases in recharge. This makes it difficult to utilise for water resources management so the results have been analysed with a risk analysis framework; this enables the future projections for groundwater recharge to be communicated to water managers in terms of likelihood and consequence of a reduction in recharge. This highlights an important message for water resource managers that in most areas of Australia they will be making decisions on water allocations under considerable uncertainty as to the direction and magnitude of recharge change under a future climate and that this uncertainty may be irreducible.     

Evaluation of the impact of climate changes on water storage and groundwater recharge at the watershed scale

 The increase of concentration of carbon dioxide and other greenhouse gases in the atmosphere will certainly affect hydrological regimes. Global warning is thus expected to have major implications on water resources management. Our objective is to present a general approach to evaluate the effect of potential climate changes on groundwater resources. In the current stage of knowledge, large-scale global climate models are probably the best available tools to provide estimates of the effects of raising greenhouse gases on rainfall and evaporation patterns through a continuous, three dimensional simulation of atmospheric, oceanic and cryospheric processes. However their spatial resolution (generally some thousands of square kilometers) is not compatible with that of watershed hydrologic models. The main purpose of this study is to evaluate the impact of potential climate changes upon groundwater resources. A general methodology is proposed in order to disaggregate outputs of large-scale models and thus to make information directly usable by hydrologic models. As an illustration, this method is applied to a CO₂-doubling scenario through the development of a local weather generator, although many uncertainties are not yet assessed about the results of climate models. Two important hydrological variables: rainfall and potential evapotranspiration are thus generated. They are then used by coupling with a physically based hydrological model to estimate the effects of climate changes on groundwater recharge and soil moisture in the root zone. Received: 17 April 1998 / Accepted: 29 September 1998     

Climate change at the ecosystem scale: a 50-year record in New Hampshire

Observing the full range of climate change impacts at the local scale is difficult. Predicted rates of change are often small relative to interannual variability, and few locations have sufficiently comprehensive long-term records of environmental variables to enable researchers to observe the fine-scale patterns that may be important to understanding the influence of climate change on biological systems at the taxon, community, and ecosystem levels. We examined a 50-year meteorological and hydrological record from the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, an intensively monitored Long-Term Ecological Research site. Of the examined climate metrics, trends in temperature were the most significant (ranging from 0.7 to 1.3 °C increase over 40–50 year records at 4 temperature stations), while analysis of precipitation and hydrologic data yielded mixed results. Regional records show generally similar trends over the same time period, though longer-term (70–102 year) trends are less dramatic. Taken together, the results from HBEF and the regional records indicate that the climate has warmed detectably over 50 years, with important consequences for hydrological processes. Understanding effects on ecosystems will require a diversity of metrics and concurrent ecological observations at a range of sites, as well as a recognition that ecosystems have existed in a directionally changing climate for decades, and are not necessarily in equilibrium with the current climate.     

城市热岛效应热点问题研究进展

概述了国内外城市热岛效应研究热点及不足,探讨了时空替代性、评价指标合理性、模拟空间尺度适宜性及理论与应用研究相结合等问题,指出未来城市热岛效应研究应注重新方法与新思路的集成、城市群热岛效应监测、城市热岛与全球异常环境要素间的生态关联性、缓解城市热岛效应的生态途径与技术方法。     

城市热岛效应热点问题研究进展

概述了国内外城市热岛效应研究热点及不足,探讨了时空替代性、评价指标合理性、模拟空间尺度适宜性及理论与应用研究相结合等问题,指出未来城市热岛效应研究应注重新方法与新思路的集成、城市群热岛效应监测、城市热岛与全球异常环境要素间的生态关联性、缓解城市热岛效应的生态途径与技术方法。     

Perceptions of climate change: Linking local and global perceptions through a cultural knowledge approach

Understanding public perceptions of climate change is fundamental to both climate science and policy because it defines local and global socio-political contexts within which policy makers and scientists operate. To date, most studies addressing climate change perceptions have been place-based. While such research is informative, comparative studies across sites are important for building generalized theory around why and how people understand and interpret climate change and associated risks. This paper presents a cross-sectional study from six different country contexts to illustrate a novel comparative approach to unraveling the complexities of local vs global perceptions around climate change. We extract and compare ‘cultural knowledge’ regarding climate change using the theory of ‘culture as consensus’. To demonstrate the value of this approach, we examine cross-national data to see if people within specific and diverse places share ideas about global climate change. Findings show that although data was collected using ethnographically derived items collected through place-based methods we still find evidence of a shared cultural model of climate change which spans the diverse sites in the six countries. Moreover, there are specific signs of climate change which appear to be recognized cross-culturally. In addition, results show that being female and having a higher education are both likely to have a positive effect on global cultural competency of individuals. We discuss these result in the context of literature on environmental perceptions and propose that people with higher education are more likely to share common perceptions about climate change across cultures and tentatively suggest that we appear to see the emergence of a ‘global’, cross-cultural mental model around climate change and its potential impacts which in itself is linked to higher education.     

Some implications of a new approach to the water vapour feedback

The water vapour feedback is the largest physical climate feedback. It also gives the second-largest contribution to the range of uncertainty in climate sensitivity in General Circulation Models (GCMs). Tracing these differences back to their physical causes in the hope of constraining climate sensitivity requires an appropriate quantification. Yet the Intergovernmental Panel on Climate Change judge that the conventional diagnosis of a “water vapour feedback” and a “lapse rate feedback” provides little insight into differences between GCMs’ climate sensitivities. We show that the conventionally diagnosed water vapour feedback is in fact formally useless for investigating differences between GCMs’ climate sensitivities—the anticorrelation between conventional “water vapour feedback” and “lapse rate feedback” makes the correlation between the “water vapour feedback” and their sum insignificant: i.e. statistically, knowing this “feedback” allows one to conclude nothing about the sum and thence about climate sensitivity. This follows primarily from how little relative humidity (RH) changes with climate change in GCMs. A more detailed physical analysis concludes that the overall mean decrease of RH on warming seen in GCMs is robustly physically based. This and other physical arguments then suggest that the stronger the positive “water vapour feedback”, the less sensitive climate can be expected to be. A diagnosis based on the “partly-Simpsonian” model of water vapour feedback avoids these problems. On the conventional view of the water vapour feedback, naive extrapolation of variations within present-day climate suggests that parts of our planet are close to locally reaching conditions that would allow a run-away water vapour greenhouse effect once they were extensive enough. Of course this has never occurred in geological history, and is not seen in Earth-like GCMs. Again, the “partly-Simpsonian” approach provides a simple qualitative explanation, by showing that the water vapour feedback can only cancel part of the basic Planck’s Law negative feedback.