中国地面气温变化趋势中的城市化影响偏差

在中国大陆2300个气象台站网中遴选出138个参考站,对614个国家级气象站和138个参考站1961 2004年的月平均气温资料进行了非均一性检验和订正,利用REOF(旋转主分量)分析方法,按照气温变率空间相关特点将中国大陆划分为6大区域,并采用经纬度网格面积加权平均法分别建立了中国大陆及其6大区域平均的国家站和参考站的月、季、年地面气温时间序列,对国家站和参考站序列进行了对比分析。结果表明,由国家站资料建立的中国大陆年平均气温序列在44年间线性增温率为0.278 C/10 a,而由参考站资料建立的中国大陆年平均气温序列同期增温率为0.202℃/10 a。就中国大陆平均来说,1961 2004年国家级站城市化增温率为0.076 C/10 a,占全部增温率的27.33%。在6大区域中,除北疆区外,其他地区年平均城市化增温率均非常显著。其中城市化影响最大的地区是江淮区,年平均热岛增温率为0.086℃/10 a,其后依次为东北华北区、青藏高原区、华南区和西北区,年平均热岛增温率分别达到0.060、0.059、0.042和0.042℃/10 a。各区域年平均热岛增温贡献率由大到小排列依次为江淮区55.48%、青藏高原区23.23%、华南区23.20%、东北华北区15.35%、西北区13.73%、北疆区-1.57%。因此,中国大陆20世纪60年代初以来城市化造成的国家站地面气温增暖偏差非常显著,今后应予以订正,以便建立代表背景气候变化的区域平均气温序列。     

中国东部地区城市化对气温影响的观测分析

现有场地观测表明,城市化对于气温的影响在静风、无云条件下的晚上最明显,而在大风、多云条件下的晚上最小.本文采用一套经过均一化处理的中国地区逐日平均、最高以及最低气温序列资料集,分析了中国东部地区在不同风速、云量条件下地面气温变化的趋势.结果表明,从1960-2008年,中国东部地区(20～45° N,110～125° ...     

Impact of land use changes on surface warming in China

Land use changes such as urbanization, agriculture, pasturing, deforestation, desertification and irrigation can change the land surface heat flux directly, and also change the atmospheric circulation indirectly, and therefore affect the local temperature. But it is difficult to separate their effects from climate trends such as greenhouse-gas effects. Comparing the decadal trends of the observation station data with those of the NCEP/NCAR Reanalysis (NNR) data provides a good method to separate the effects because the NNR is insensitive to land surface changes. The effects of urbanization and other land use changes over China are estimated by using the difference between the station and the NNR surface temperature trends. Our results show that urbanization and other land use changes may contribute to the observed 0.12℃ (10 yr)- 1 increase for daily mean surface temperature, and the 0.20℃ (10 yr)- 1 and 0.03℃ (10 yr)-1 increases for the daily minimum and maximum surface temperatures, respectively. The urban heat island effect and the effects of other land-use changes mayalso play an important role in the diurnal temperature range change. The spatial pattern of the differences in trends shows a marked heterogeneity.The land surface degradation such as deforestation and desertification due to human activities over northern China, and rapidly-developed urbanization over southern China, may have mostly contributed to the increases at stations north of about 38°N and in Southeast China, respectively. Furthermore, the vegetation cover increase due to irrigation and fertilization may have contributed to the decreasing trend of surface temperature over the lower Yellow River Basin. The study illustrates the possible impacts of land use changes on surface temperature over China.     

北疆地区城市化对地面气温趋势估算影响的特殊性

城市化对我国大部分气象站地面气温观测记录都造成了额外的增温,即引起气温观测趋势的正向偏差,但先前研究表明北疆地区城市化可能引起国家站和城市站地面气温出现变凉趋势。为了深入了解这个问题,本文利用前期研究发展的气温参考站数据集和相关分析方法,对北疆地区基准、基本站网和4个代表性城镇站记录的地面气温序列趋势变化特征进行了比较分析,探讨了造成这一特殊现象的可能原因。分析表明证实,北疆地区城镇站和基准、基本站与全国其他地区的相比,其城市化影响表现为明显的气温负趋势,基准、基本站年平均城市化影响达到-0.05℃/10a,城市化贡献为-14.1%,春、夏和秋季城市化影响均为显著的负趋势,秋季最为明显,冬季城市化影响表现出不显著的正趋势;乌苏、石河子、克拉玛依和乌鲁木齐四个城镇站年平均城市化影响介于-0.07~-0.19℃/10a,城市化贡献率介于23.3~100%。本文分析结果有助于深入理解干燥区城市化对地面气温观测序列影响的特殊性及其可能原因,对于区域气候变化检测和归因以及干燥区城市化和绿洲化气候效应研究有一定借鉴意义。     

Predicting the impacts of global warming on wildland fire

Simulations of impacts of a double-CO₂ climate with the Changed Climate Fire Modeling System in Northern California consistently projected increases in area burned and in the frequency of escaped fires compared with simulations of the present climate. However, the magnitude of those increases was strongly influenced by vegetation type, choice of atmospheric general circulation model (GCM) scenario, and choice of climatic forcing variables. The greatest projected increase in fire severity occurred in grasslands, using the Princeton Geophysical Fluid Dynamics Laboratory GCM, with wind speed, temperature, humidity and precipitation as driving variables.     

中国不同纬度城市群对夏季短期高温天气影响的模拟研究

本文利用中尺度WRF v3.2模式,通过改变中国东部京津冀、长三角、珠三角3个典型城市群下垫面类型,对大规模城市化效应进行模拟研究,探究不同纬度(不同背景环流场)不同规模的城市群发展对短期夏季高温天气的影响及可能机制,结果表明:大规模城市化后,城市扩展区近地层(地表2 m)气温均出现显著升高,城市化率越高,城市扩展面积越大,中心升温值越显著,最大升温超过了1.8℃,在不同背景风场的作用下,升温范围都向下风区扩展,长三角地区城市扩展造成的升温比京津冀强,又强于珠三角地区;城市化改变城区湿度状况,使城区出现显著干岛,湿度响应具有显著的局地性,温湿空间分布有很好的对应关系,城区整体呈现出"干暖"趋势;城市化改变地表能量平衡,使感热通量增加潜热通量减少;调整降水分布,使主城区降水较少。     

Possible climatic impacts of land cover transformations,with particular emphasis on tropical deforestation

The climatic impact of albedo changes associated with land-surface alterations has been examined. The total surface global albedo change resulting from major land-cover transformations (i.e. deforestation, desertification, irrigation, dam-building, urbanization) has been recalculated, modifying the estimates of Sagan et al., (1979). Tropical deforestation (11.1 million ha yr^-1, or 0.6% yr^-1, Lanly, 1982) ranks as a major cause of albedo change, although uncertainties in the areal extent of desertification could conceivably render this latter process of similar significance. The maximum total global albedo change over the last 30 yr for the various processes lies between 0.000 33 and 0.000 64, corresponding to a global temperature decrease of between 0.06 K and 0.09 K (scaled from the 1-D radiative convective model of Hansen et al., 1981), which falls well below the interannual and longer period variability.An upper bound to the impact of tropical deforestation was obtained by concentrating all vegetation change into a single region. The magnitude of this modification is equivalent to 35–50 yr of global deforestation at the current rate, but centered on the Brazilian Amazon. The climatic consequences of such tropical deforestation were simulated, using the GISS GCM (Hansen et al., 1983). In the simulation, a total area of 4.94 × 10⁶ km² of tropical moist forest was removed and replaced by a grass/crop cover. Although surface albedo increased from 0.11 to 0.19, the effect upon surface temperature was negligible. However, other climate parameters were altered. Rainfall decreased by 0.5–0.7 mm day^-1 and both evapotranspiration and total cloud cover were reduced. The absence of a temperature decrease in spite of the increased surface albedo arises because the reduction in evapotranspiration has offset the effects of radiative cooling. The decrease in cloud cover also counteracts the increase in surface albedo. These locally significant changes had no major impact on regional (Hadley or Walker cells) or the global circulation patterns.We conclude that the albedo changes induced by current levels of tropical deforestation appear to have a negligibly small effect on the global climate.     

Long-term surface air temperature trend and the possible impact on historical warming in CMIP5 models

模式对历史气候变化的模拟往往延用工业革命前控制试验(PICTL)的物理过程及设置,同时使用PICTL的模拟结果作为初值。因此,控制试验(PICTL)中是否存在气候漂移将直接影响模式对全球变暖的模拟。本文评估了27个CMIP5模式模拟的气温长期漂移趋势及其对全球变暖模拟的影响。结果表明,大部分模式模拟的全球平均气温的长期漂移趋势都很小(0.06°C/100 a),但个别模式对于全球变暖的模拟存在较大影响。在50°S~65°S纬度带内的南大洋,40°N以北的北大西洋和北太平洋区域,大部分模式模拟的气温漂移趋势对局地变暖的模拟影响较大(10%~20%)。大气层顶向上长波辐射和向上短波辐射共同影响全球气温的长期变化。另外,积分时间越长,中高纬深层海洋得到有效调整,气温的长期漂移趋势越小。本文量化了气候漂移,检验了模式的稳定性,这有助于评估模式对全球变暖的模拟能力。     

全球变暖情景下中国气温分区的未来变化

利用SRES A2情景下IPCC AR4的13个模式资料,结合我国月平均温度观测资料对当前和未来我国气温的分区进行对比研究。结果表明：1961-1990、2021-2050年和2071-2097年三个时段年平均气温分区在我国西部变化不大,而在我国东部发生了显著变化。1961-1990年我国东部被华北分区带分为南、北两个区;2021-2050年由于1961-1990年间的华北分区带北移,而在两广以北同时出现另一分区带,使得该时段我国东部分成东北区、华北和华中区以及华南区三个区,在2071-2097年北方分区带消失,而南方的分区带北移至长江一带,使得该时段我国东部仍可分为南、北两区。通过比较三个时段不同分区年平均温度时间变化发现,导致分区变化的原因主要是由于在不同时段各分区年平均温度的变率和增温幅度不一致所致。     

城市化对广州降水的影响分析

利用1959—2009年逐日降水观测数据,分析了广州51 a来降水的变化规律。发现城郊增城年总降水量变化趋势不明显,但大暴雨降水日数有所增加;广州年降水总量总体呈波动变化,1991年以来有微弱的增加趋势,增率为105 mm/a。而从降水等级日数和降水负荷上分析发现,1982年以来,广州年降水日数有下降的趋势,减少率为72 d/10a;而1991年以来,广州大雨以上等级降水日数和降水负荷均有明显的上升趋势,其中大雨降水日数增长率为28 d/10a,暴雨降水负荷增长率为24%/10a;城市化造成了广州大雨、暴雨和大暴雨等年强降水日数增加,相比1960—1979年,分别增加了6%、11%和23%;相对于城市化之前,从1991年开始,城市化过程使得广州降水量增加的趋势明显,城市化对广州城市降水增加的贡献率为447％。     

全球变暖形势下中国陆表水分的变化

利用政府间气候变化委员会第四次评估报告（IPCCAR4）中的10个耦合模式CO：加倍试验和控制试验的模拟结果,分析了全球变暖背景下中国水分的变化。结果表明,随着全球变暖,东亚夏季风增强,冬季风减弱,使得冬夏季向中国区域输送的水汽都增强;中国区域降水,夏季除长江流域外基本都增加,冬季除华南外都增加。夏季降水蒸发差（P—E）除了在东北和南方增加外,从长江流域一直到西北有一带状减小带;冬季几乎所有模式的P—E表现为北方增加、南方减小。在全球变暖背景下,降水、蒸发和径流的综合结果以及积雪的作用使得土壤湿度在干旱区增加,且冬季干旱区土壤变湿的强度和范围大于夏季,然而在其他区域土壤湿度减少。上述结论是基于多模式集合平均结果,对未来气候的预估具有一定的参考价值,然而模式间存在较强差异性,仍具有较大不确定性。     

青藏高原东北侧的湿柱和干暖盖

本文通过揭示雹暴发生前12小时降雹区出现湿柱与干暖盖的天气学事实,探讨其基本成因,利用有限区域细网格计算分析它们的物理结构,给出湿柱的概念模型。     

Possible impacts of climatic warming scenarios on water resources in the Saskatchewan River Sub-basin,Canada

Regional scale studies of the impacts of global warming scenarios provide a useful mechanism for identifying potential regional sensitivities, data gaps and research needs, and for raising awareness of the global warming issue at the regional level. Thus, a pilot study of water resources in the Saskatchewan River Sub-basin was undertaken in order to provide first-cut estimates of impacts in this region, and to identify future research needs. Thirty scenarios were constructed, using two hypothetical growth rates for irrigation, five scenarios based on outputs from General Circulation Models (GCMs), and ten hypothetical warming scenarios. During the course of this study, a number of methodological questions were raised, including the representativeness of data points, interpolation of observed and scenario data, and the quantification of uncertainty.Results indicated decreases in summer soil moisture and increases in irrigation demand, but no consensus on changes in runoff or annual net basin supply, primarily due to differences in the GCM-based scenario output at the Rocky Mountains, the major source region for runoff. There were a number of recommendations for follow-up research and monitoring.     

Estimating impacts of warming temperatures on California's electricity system

Despite a clear need, little research has been carried out at the regional-level to quantify potential climate-related impacts to electricity production and delivery systems. This paper introduces a bottom-up study of climate change impacts on California's energy infrastructure, including high temperature effects on power plant capacity, transmission lines, substation capacity, and peak electricity demand. End-of-century impacts were projected using the A2 and B1 Intergovernmental Panel on Climate Change emission scenarios. The study quantifies the effect of high ambient temperatures on electricity generation, the capacity of substations and transmission lines, and the demand for peak power for a set of climate scenarios. Based on these scenarios, atmospheric warming and associated peak demand increases would necessitate up to 38% of additional peak generation capacity and up to 31% additional transmission capacity, assuming current infrastructure. These findings, although based on a limited number of scenarios, suggest that additional funding could be put to good use by supporting R&D into next generation cooling equipment technologies, diversifying the power generation mix without compromising the system's operational flexibility, and designing effective demand side management programs.     

The impacts of urbanization on air quality over the Pearl River Delta in winter: roles of urban land use and emission distribution

In this study, ideal but realistic numerical experiments are performed to explore the relative effects of changes in land use and emission distribution on air quality in the Pearl River Delta (PRD) region in winter. The experiments are accomplished using the Lagrangian particle transport and dispersion model FLEXPART coupled with the Weather Research and Forecasting model under different scenarios. Experiment results show that the maximum changes in daily mean air pollution concentration (as represented by SO₂ concentration) caused by land use change alone reaches up to 2?×?10^?6 g m^?3, whereas changes in concentrations due to the anthropogenic emission distribution are characterized by a maximum value of 6?×?10^?6 g m^?3. Such results reflect that, although the impacts of land use change on air quality are non-negligible, the emission distribution exerts a more significant influence on air quality than land use change. This provides clear implications for policy makers to control urban air pollution over the PRD region, especially for the urban planning in spatial arrangements for reasonable emissions.     

The impacts of global warming on farmers in Brazil and India

How big a threat is global warming to climate-sensitive and economically important sectors such as agriculture in developing countries? How well will farmers be able to adapt to the threats of global warming? This paper attempts to shed light on these two important questions. A cross-sectional analysis is employed to estimate the climate sensitivity of agriculture in Brazil and India. Using panel data from both countries, the study measures how net farm income or property values vary with climate, and consequently, how farmers in India and Brazil react and adapt to climate. The estimated relationships are then used to predict the consequence of alternative climate scenarios. Global warming by the end of the next century could cause annual damages in Brazil between 1% and 39% and between 4% and 26% in India, although some of this effect may be potentially offset by carbon fertilization. These estimates do not factor into account climate-induced extreme weather events.     

全球变暖对台风活动影响的研究进展

全球变暖是当前热点问题之一,各大洋区时有发生的"超乎寻常"的台风活动也广为关注.全球范围内的台风活动特征是否悄然发生了变化?这种变化与全球变暖是否存在关联?这些问题已成为国际台风界的重点研究内容之一,近年来取得了许多进展.文中从全球台风活动特征变化事实的观测研究,成因分析、数值模拟与预测等方面对此进行了概述.综合各方观点,得到主要共识如下:单个台风的异常活动不宜直接归因于气候变化;全球台风频数的年际变化趋势并不明显;沿海地区人口增长和基础设施增加是近期台风对社会影响加重的主要原因;自1970年以来,一些海区的超强台风比例明显增大,比目前数值模式的模拟结果要大许多;如果全球气候持续变暖,台风的最大风速和降水很可能会继续增加;尽管在台风记录中同时有支持和不支持人类活动(全球变暖的影响)信号存在的证据,但在这一点上还不能给出一致的肯定结论.另外,由于台风和相关气候资料存在均一性方面问题,气候数值模式对台风气候特征描述也存在缺陷,这两类问题的存在使得在目前阶段确切阐明全球变暖和台风活动的关系仍有极大的不确定性.     

Effect of urbanization on the urban meteorology and air pollution in Hangzhou

Urbanization has a substantial effect on urban meteorology. It can alter the atmospheric diffusion capability in urban areas and therefore affect pollutant concentrations. To study the effects of Hangzhou’s urban development in most recent decade on its urban meteorological characteristics and pollutant diffusion, 90 weather cases were simulated, covering 9 weather types, with the Nanjing University City Air Quality Prediction System and high-resolution surface-type data and urban construction data for 2000 and 2010. The results show that the most recent decade of urban development in Hangzhou substantially affected its urban meteorology. Specifically, the average urban wind speed decreased by 1.1 m s ^?1; the average intensity of the heat island increased by 0.5°C; and the average urban relative humidity decreased by 9.7%. Based on one case for each of the nine weather types, the impact of urbanization on air pollution diffusion was investigated, revealing that the changes in the meteorological environment decreased the urban atmosphere’s diffusion capability, and therefore increased urban pollutant concentrations. For instance, the urban nitrogen oxides concentration increased by 2.1 μg m ^?3 on average; the fine particulate matter (diameter of 2.5 μm or less; PM_2.5) pollution concentration increased by 2.3 μg m ^?3 on average; in highly urbanized areas, the PM_2.5 concentration increased by 30 μg m ^?3 and average visibility decreased by 0.2 km, with a maximum decrease of 1 km; the average number of daily hours of haze increased by 0.46 h; and the haze height lifted by 100–300 m. The “self-cleaning time” of pollutants increased by an average of 1.5 h.