Projected potential vegetation change in China under the SRES A2 and B2 scenarios

The ability of seven global coupled ocean-atmosphere models to reproduce East Asian monthly surface temperature and precipitation climatologies during 1961 1990 is evaluated. January and July climate differences during the 2050s and 2090s relative to 1961-1990 projected by the seven-model ensemble under the Special Report on Emission Scenarios （SRES） A2 and B2 scenarios are then briefly discussed. These projections, together with the corresponding atmospheric CO2 concentrations under the SRES A2 and B2 scenarios, are subsequently used to drive the biome model BIOME3 to simulate potential vegetation distribution in China during the 2050s and 2090s. It is revealed that potential vegetation belts during the 2050s shift northward greatly in central and eastern China compared to those during 1961-1990. In contrast, potential vegetation change is slight in western China on the whole. The spatial pattern of potential vegetation during the 2090s is generally similar to that during the 2050s, but the range of potential vegetation change against 1961 1990 is more extensive during the 2090s than the 2050s, particularly in western China. Additionally, there exists model-dependent uncertainty of potential vegetation change under the SRES A2 scenario during the 2090s, which is due to the scatter of projected climate change by the models. The projected change in potential vegetation under the SRES A2 scenario during the 2090s is attributable to surface temperature change south of 35°N and to the joint changes of surface temperature, precipitation, and atmospheric CO2 concentration north of 35°N.     

Sensitivity of East Asian climate to the progressive uplift and expansion of the Tibetan Plateau under the mid-Pliocene boundary conditions

A global atmospheric general circulation model has been used to perform eleven idealized numerical experiments, i.e., TP10, TP10, .., TP100, corresponding to different percentages of the Tibetan Plateau altitude. The aim is to explore the sensitivity of East Asian climate to the uplift and expansion of the Tibetan Plateau under the reconstructed boundary conditions for the mid-Pliocene about 3 Ma ago. When the plateau is progressively uplifted, global annual surface temperature is gradually declined and statistically significant cooling signals emerge only in the Northern Hemisphere, especially over and around the Tibetan Plateau, with larger magnitudes over land than over the oceans. On the contrary, annual surface temperature rises notably over Central Asia and most parts of Africa, as well as over northeasternmost Eurasia in the experiments TP60 to TP100. Meanwhile, the plateau uplift also leads to annual precipitation augmentation over the Tibetan Plateau but a reduction in northern Asia, the Indian Peninsula, much of Central Asia, parts of western Asia and the southern portions of northeastern Europe. Additionally, it is found that an East Asian summer monsoon system similar to that of the present initially exists in the TP60 and is gradually intensified with the continued plateau uplift. At 850 hPa the plateau uplift induces an anomalous cyclonic circulation around the Tibetan Plateau in summertime and two anomalous westerly currents respectively located to the south and north of the Tibetan Plateau in wintertime. In the mid-troposphere, similarto-modern spatial pattern of summertime western North Pacific subtropical high is only exhibited in the experiments TP60 to TP100, and the East Asian trough is steadily deepened in response to the progressive uplift and expansion of the Tibetan Plateau.     

“一带一路”区域气候变化事实、影响及可能风险

“一带一路”区域国家经济、政治发展极不平衡,随着全球气候变暖,区域内的自然环境、气候资源、水资源等都将面临着显著而复杂的变化,并且干旱、洪涝等多种气候灾害是“一带一路”区域可持续发展和重大基础设施建设面临的重大威胁之一。目前,“一带一路”倡议已经进入实质性建设阶段,沿线地区的气候变化及其灾害风险关乎“一带一路”倡议能否顺利实施及亚投行的投资安全。在此背景下,2016—2018年中国科学院地球科学学部实施了“‘一带一路’区域气候变化问题”咨询评议项目,项目针对该区域气候变化的事实、未来变化预估、气候变化的可能影响以及带来的潜在风险等问题进行了系统的调研,并开展了若干分析和研究。经过两年的努力,项目组完成了有关进展报告四份,包括一份总报告和三份分报告。本文扼要地概括和介绍了项目取得的主要成果。     

大样本初始化十年际预测试验（CESM-DPLE）对东亚夏季气候预测的评估

基于气温和降水观测资料以及美国国家环境预报中心/国家大气研究中心（NCEP/NCAR）大气再分析资料,系统评估了大样本初始化十年际预测试验（CESM-DPLE）对1959—2016年东亚夏季气候预测的能力。结果表明,CESM-DPLE能较好地模拟东亚夏季气候以及相关主要大气环流系统的基本态特征,在年际尺度上对东亚气温有很高的预测技巧但对降水几乎没有预测能力。CESM-DPLE再现了北大西洋多年代际振荡（AMO）经由激发遥相关波列所引起的中高纬度大气环流、东亚夏季风和气候的异常。20世纪90年代末之后,北大西洋多年代际振荡由冷位相转为暖位相,遥相关波列位相调整,东亚受异常低压控制,东亚夏季风偏强,夏季气温偏高、降水偏多。总体上,尽管还存在着不足,但CESM-DPLE对东亚夏季温度年际变化以及与20世纪90年代末北大西洋多年代际振荡位相转变相联的东亚夏季气候年代际变化具备一定的预测能力,是目前研究和预测东亚气候变化的一套较好试验数据。      

东亚季风区夏季风强度和降水的配置关系

1979～2000年东亚地区夏季风强度和夏季总降水之间的关系被分为四种类型:A:强季风、强降水;B:强季风、弱降水;C:弱季风、强降水;D:弱季风、弱降水.通过研究不同关系对应的大气环流特征和SST异常,并分析不同要素在季风和降水关系变化中的作用,发现在季尺度上东亚季风区夏季风强度和地区同期降雨总量的关系具有多面性特征,此关系取决于环流场的整体配置,其中西太平洋副高﹑南亚高压和中高纬阻塞形式为三个起主导作用的因素.另外,海温变化对东亚季风和总降水的关系有明显的影响,尤其是北太平洋﹑印度洋和南海区域海温.合成分析结果表明500 hPa东亚异常波列和东亚夏季风强度密切相关,但波形与东亚季风区夏季总降水强弱没有明显联系.     

SRES A2情景下中国气候未来变化的多模式集合预测结果

采用政府间气候变化委员会资料中心的模式预测结果,本文分析了SRES A2温室气体和气溶胶排放情景下中国大陆21世纪前30年的10年际气候变化趋势. 研究揭示：大陆冬季和夏季表面温度、表面最高温度和最低温度分别升高0.3～2.3℃、0.1～2.0℃、0.5～2.7℃,增幅大体上呈现东西向带状分布,由南至北升温逐渐加强,且增幅随时间加大. 此外,上述三气候要素冬季升温幅度要大于同期夏季、表面最低温度升幅要强于同期表面最高温度,冬季和夏季表面温度的季节内变化范围减小. 冬季东亚地区海平面气压异常幅度在-1.0hPa至0.4hPa之间变化,呈东西向带状分布,表现为南正北负、随时间推进异常幅度有所加大,正负交界面向南扩展;同时,东北、华北和西部海平面气压负异常较大. 夏季海平面气压异常空间分布与冬季相似. 2001～2030年,青藏高原大部、大陆东南部和河套大部分地区降水量增加0.1～0.8mm/d.     

1961～2018年中国生长季变化

在全球变暖背景下,中国区域生长季发生了改变,但以往研究时段偏短、数据分辨率低且空间覆盖相对有限。本文利用0.25°×0.25°高水平分辨率日平均气温资料CN05.1,研究了1961～2018年中国生长季开始日、结束日和长度的气候态特征、变化趋势及其与季节平均温度的关系。结果表明,1961～2018年中国平均生长季开始日和结束日分别为3月31日和10月29日,长度为212 d。空间上,开始日由东南向西北逐渐推迟,结束日呈反向变化,长度由东南向西北缩短。整体而言,1961～2018年中国平均生长季开始日提前、结束日推迟、长度延长,其速率分别为?1.3 d (10 a)?1、0.9 d (10 a)?1、2.2 d (10 a)?1,其中开始日提前对长度延长的影响更大。此外,中国平均生长季开始日提前和长度增加主要源于春季升温,而结束日推迟则与秋季变暖有关。     

关于末次盛冰期青藏高原大范围冰盖存在可能性的再研究

通过4组数值敏感性试验,利用BIOME3生态模式对末次盛冰期中国大陆植被分布状况进行了数值模拟,再次研究了该时期青藏高原大范围冰盖存在的可能性问题.结果表明,末次盛冰期大陆植被发生了大规模的变化,总体呈退化趋势;在降温5℃、降水减少10%、二氧化碳下降145×10-6和地球轨道参数轻微变化的情况下,青藏高原约1/2的地区已经被冰覆盖;进一步的降温和干燥则会加大高原冰的覆盖面积和大陆其余地区植被的退化.     

大气初始异常在跨季度短期气候预测中作用的研究

针对大气初始异常在跨季度短期气候预测中的可能作用,利用中国科学院大气物理研究所9层大气环流格点模式(简称IAP 9L-AGCM)对全球夏季气候进行了30年(1970～1999年)集合回报试验,系统地考察了基于大气初始异常条件下模式对跨季度短期气候异常的可预测性.结果表明,在热带、副热带及高纬都存在气候异常的可预测性区域,说明大气初始场异常本身对跨季度短期气候预测有很重要的影响.相对于全球来说,大气初始异常对跨季度短期气候预测的影响在东亚地区更为显著,其作用不可忽略.通过对典型年份的个例分析发现,在某些气候异常剧烈的特殊年份,春季大气初始异常在我国夏季气候形成中扮演着尤为重要的角色.     

沙漠化扩展对区域气候影响的数值模拟研究

利用GCM -SSiB全球大气环流谱模式,设计两组数值模拟试验(即控制试验(CE)和沙漠面积扩大试验(DE)),研究了大陆沙漠化对我国区域气候变化的影响。模拟结果表明:沙区扩展后,大陆年平均地表温度降低,海平面气压上升,纬向风速、季风加强,夏季低空上升运动减弱,冬季下沉运动增强,降雨量显著减少,地表蒸发、感热和潜热通量亦显著减少。我国区域气候随大陆沙漠化扩展趋向冷干、风速加大,沙漠扩展与区域气候恶化存在正反馈。