Atmospheric and Oceanic Science Letters最新文献

The active layer, acting as an intermediary of water and heat exchange between permafrost and atmosphere, greatly influences biogeochemical cycles in permafrost areas and is notably sensitive to climate fluctuations. Utilizing the Chinese Meteorological Forcing Dataset to drive the Community Land Model, version 5.0, this study simulates the spatial and temporal characteristics of active layer thickness (ALT) on the Tibetan Plateau (TP) from 1980 to 2020. Results show that the ALT, primarily observed in the central and western parts of the TP where there are insufficient station observations, exhibits significant interdecadal changes after 2000. The average thickness on the TP decreases from 2.54 m during 1980–1999 to 2.28 m during 2000–2020. This change is mainly observed in the western permafrost region, displaying a sharp regional inconsistency compared to the eastern region. A persistent increasing trend of ALT is found in the eastern permafrost region, rather than an interdecadal change. The aforementioned changes in ALT are closely tied to the variations in the surrounding atmospheric environment, particularly air temperature. Additionally, the area of the active layer on the TP displays a profound interdecadal change around 2000, arising from the permafrost thawing and forming. It consistently decreases before 2000 but barely changes after 2000. The regional variation in the permafrost active layer over the TP revealed in this study indicates a complex response of the contemporary climate under global warming.

摘要

活动层是多年冻土和大气之间的缓冲层, 对气候波动十分敏感, 其冻融变化对多年冻土区的地球生物化学循环有较大影响. 本研究利用高分辨率气象数据集CMFD和陆面过程模式CLM5.0模拟分析了青藏高原1980–2020年活动层的变化. 结果表明: 青藏高原的活动层厚度在2000年后有显著的年代际变化, 青藏高原整体活动层厚度由1980–1999的2.54 m减少到2000–2020年的2.28 m. 这种变化主要发生在西部的多年冻土区, 与东部相比存在明显的区域差异. 在东部, 多年冻土区的活动层厚度呈持续增加趋势, 而不是年代际变化. 此外, 活动层面积在2000年也发生了年代际突变, 之前持续下降, 但之后几乎没有变化. 本文还发现青藏高原多年冻土活动层的区域变化受到气温和降水等环境因子的显著影响, 这反映了其在全球变暖背景下对气候变化的复杂响应.

Precipitation projections over the Tibetan Plateau (TP) show diversity among existing studies, partly due to model uncertainty. How to develop a reliable projection remains inconclusive. Here, based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity (ECS) and the climatological precipitation performance, the authors constrain the CMIP6 (phase 6 of the Coupled Model Intercomparison Project) model projection of summer precipitation and water availability over the TP. The best estimates of precipitation changes are 0.24, 0.25, and 0.45 mm d⁻¹ (5.9 %, 6.1 %, and 11.2 %) under the Shared Socioeconomic Pathway (SSP) scenarios of SSP1–2.6, SSP2–4.5, and SSP5–8.5 from 2050–2099 relative to 1965–2014, respectively. The corresponding constrained projections of water availability measured by precipitation minus evaporation (P–E) are 0.10, 0.09, and 0.22 mm d⁻¹ (5.7 %, 4.9 %, and 13.2 %), respectively. The increase of precipitation and P–E projected by the high-ECS models, whose ECS values are higher than the upper limit of the likely range, are about 1.7 times larger than those estimated by constrained projections. Spatially, there is a larger increase in precipitation and P–E over the eastern TP, while the western part shows a relatively weak difference in precipitation and a drier trend in P–E. The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6 °C–1.2 °C under all three scenarios during 2050–2099. This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.

摘要

青藏高原是气候变化敏感区, 可靠的气候预估对气候变化应对至关重要. 青藏高原夏季降水变化的预估结果在CMIP6气候模式间存在较大的不确定性, 原因部分地和这些模式对温室气体强迫的敏感度不同有关. 作者在对CMIP6模式性能进行评估基础上, 选择了具有较高气候态降水模拟技巧的模式用于预估研究, 并根据IPCC AR6估算的平衡态气候敏感度 (ECS) 的可能性范围, 对青藏高原夏季降水的中远期 (2050–2099) 变化进行约束. 结果表明, 在SSP1–2.6, SSP2–4.5 和 SSP5–8.5情景下, 青藏高原夏季降水将分别增多0.24, 0.25 和 0.45 mm d⁻¹ (5.9 %, 6.1 %, 和 11.2 %), 水资源可用性 (P–E) 将分别增加0.10, 0.09和0.22 mm d⁻¹(5.7 %, 4.9 % 和13.2 %) . 与约束预估相比, 高ECS模式预估的水文敏感度约为约束后的1.2–1.4倍, 升温幅度偏高0.6 °C–1.2 °C, 这二者共同导致高ECS模式预估的高原降水增幅约为约束预估的1.7倍. 本文指出气候敏感度是影响未来青藏高原水资源预估不确定性的重要来源, 同时基于IPCC AR6对ECS的最佳估算, 给出了高原夏季降水和水资源的最佳预估结果.

The alpine meadow ecosystem accounts for 27 % of the total area of the Tibetan Plateau and is also one of the most important vegetation types. The Dangxiong alpine meadow ecosystem, located in the south-central part of the Tibetan Plateau, is a typical example. To understand the carbon and water fluxes, water use efficiency (WUE), and their responses to future climate change for the alpine meadow ecosystem in the Dangxiong area, two parameter estimation methods, the Model-independent Parameter Estimation (PEST) and the Dynamic Dimensions Search (DDS), were used to optimize the Biome-BGC model. Then, the gross primary productivity (GPP) and evapotranspiration (ET) were simulated. The results show that the DDS parameter calibration method has a better performance. The annual GPP and ET show an increasing trend, while the WUE shows a decreasing trend. Meanwhile, ET and GPP reach their peaks in July and August, respectively, and WUE shows a “dual-peak” pattern, reaching peaks in May and November. Furthermore, according to the simulation results for the next nearly 100 years, the ensemble average GPP and ET exhibit a significant increasing trend, and the growth rate under the SSP5–8.5 scenario is greater than that under the SSP2–4.5 scenario. WUE shows an increasing trend under the SSP2–4.5 scenario and a significant increasing trend under the SSP5–8.5 scenario. This study has important scientific significance for carbon and water cycle prediction and vegetation ecological protection on the Tibetan Plateau.

摘要

全球气候变化对青藏高原生态系统产生了深远影响, 暖湿化背景下青藏高原植被碳, 水通量变化趋势值得关注. 高寒草甸是青藏高原最主要的植被类型之一, 为理解青藏高原当雄地区高寒草甸生态系统碳, 水通量, 水分利用效率及其对未来气候变化的响应, 本研究利用PEST和DDS两种参数率定方法优化Biome-BGC模型, 进而模拟2000–2019年当雄站的总初级生产力 (GPP) 和蒸散量 (ET) . 研究结果表明: DDS参数率定方法具有更优的性能. GPP和ET在研究时段内呈上升趋势, 而水分利用效率 (WUE) 则呈下降趋势. 同时, ET和GPP分别在7月和8月达到峰值, 而WUE则呈“双峰”变化, 分别于5月和11月达到峰值. 此外, 未来近百年的模拟表明GPP和ET的集合平均结果呈显著增加趋势, 其中在SSP5–8.5情景下的增速大于SSP2–4.5情景. WUE在SSP2–4.5情景下呈增加趋势, 而在SSP5–8.5情景下呈显著增加趋势. 本研究结果可为青藏高原碳, 水循环预测研究和植被生态保护的应用研究提供参考和借鉴.

Based on daily observation data of the Three Gorges Region (TGR) of the Yangtze River basin and global reanalysis data, the climate characteristics, climate events, and meteorological disasters of the TGR in 2022 and 2023 were analyzed. For the TGR, the average annual temperature for 2022 and 2023 was 0.8 °C and 0.4 °C higher than normal, respectively, making them the two warmest years in the past decade. In 2022, the TGR experienced its warmest summer on record. The average air temperature was 2.4 °C higher than the average, and there were 24.8 days of above-average high temperature days during summer. Rainfall in the TGR varied significantly between 2022 and 2023. Annual rainfall was 18.4 % below normal and drier than normal in most parts of the region. In contrast, the precipitation in 2023 was considerably higher than the long-term average, and above normal for almost the entire year. The average wind speed exhibited minimal variation between the two years. However, the number of foggy days and relative humidity increased in 2023 compared to 2022. In 2022–2023, the TGR mainly experienced meteorological disasters such as extreme high temperatures, regional heavy rain and flooding, overcast rain, and inverted spring chill. Analysis indicates that the abnormal western Pacific subtropical high and the abnormal persistence of the eastward-shifted South Asian high were the two important drivers of the durative enhancement of record-breaking high temperature in the summer of 2022.

摘要

基于长江三峡地区观测资料和全球再分析资料, 分析了该地区 2022–2023年气候特征, 酸雨状况以及主要天气气候事件. 2022 年和2023年三峡地区平均气温分别较常年偏高0.8 °C和0.4 °C, 是近十年来最暖的两年, 特别是2022年夏季出现破记录极端高温; 2022年三峡地区降水量较常年偏少18.4 %, 2023年降水量转为偏多15.3 %. 在这两年中该地区主要出现了极端高温, 区域性暴雨洪涝, 连阴雨和倒春寒等气候事件. 分析表明, 西太平洋副热带高压和南亚高压协同异常是2022年夏季极端高温维持的两个重要因素.

China witnessed a warm and dry climate in 2023. The annual surface air temperature reached a new high of 10.71°C, with the hottest autumn and the second hottest summer since 1961. Meanwhile, the annual precipitation was the second lowest since 2012, at 615.0 mm. Precipitation was less than normal from winter to summer, but more in autumn. Consistent with the annual condition, precipitation in the flood season from May to September was also the second lowest since 2012, which was 4.3% less than normal, with the anomalies in the central and eastern parts of China being higher in central areas and lower in the north and south. On the contrary, the West China Autumn Rain brought much more rainfall than normal, with an earlier start and later end. Although there was less annual precipitation in 2023, China suffered seriously from heavy precipitation events and floods. In particular, from the end of July to the beginning of August, a rare, extremely strong rainstorm caused by Typhoon Dussuri hit Beijing, Tianjin, and Hebei, causing an abrupt alteration from drought to flood conditions in North China. By contrast, Southwest China experienced continuous drought from the previous autumn to current spring. In early summer, North China and the Huanghuai region experienced the strongest high-temperature process since 1961. Nevertheless, there were more cold-air processes than normal impacting China, with the most severe of the year occurring in mid-January. Unexpectedly, in spring, there were more sand and dust occurrences in northern China.

摘要

2023年, 我国气候暖干特征明显, 全国平均气温10.71°C, 为1951年以来最暖; 全国平均降水量615.0 mm, 较常年偏少3.9%, 为2012年以来第二少. 汛期 (5–9月), 全国平均降水量为2012年以来第二少, 中东部降水总体呈“中间多南北少”的分布. 2023年, 我国区域性气象干旱多发, 西南地区遭遇冬春连旱; 春季北方沙尘天气过程偏多; 夏季前期, 华北和黄淮遭受1961年以来最强高温过程; 7月底至8月初, 受台风杜苏芮影响, 京津冀地区发生历史罕见极端强降雨过程, 华北地区出现“旱涝急转”; 华西秋雨开始早, 结束晚, 雨量多.

The Tibetan Plateau (TP) is a prevalent region for convection systems due to its unique thermodynamic forcing. This study investigated isolated deep convections (IDCs), which have a smaller spatial and temporal size than mesoscale convective systems (MCSs), over the TP in the rainy season (June–September) during 2001–2020. The authors used satellite precipitation and brightness temperature observations from the Global Precipitation Measurement mission. Results show that IDCs mainly concentrate over the southern TP. The IDC number per rainy season decreases from around 140 over the southern TP to around 10 over the northern TP, with an average 54.2. The initiation time of IDCs exhibits an obvious diurnal cycle, with the peak at 1400–1500 LST and the valley at 0900–1000 LST. Most IDCs last less than five hours and more than half appear for only one hour. IDCs generally have a cold cloud area of 7422.9 km², containing a precipitation area of approximately 65%. The larger the IDC, the larger the fraction of intense precipitation it contains. IDCs contribute approximately 20%–30% to total precipitation and approximately 30%–40% to extreme precipitation over the TP, with a larger percentage in July and August than in June and September. In terms of spatial distribution, IDCs contribute more to both total precipitation and extreme precipitation over the TP compared to the surrounding plain regions. IDCs over the TP account for a larger fraction than MCSs, indicating the important role of IDCs over the region.

摘要

本文利用卫星观测资料, 研究了2001–2020年雨季 (6–9月) 青藏高原上孤立深对流 (Isolated deep convections, IDCs) 的气候特征. IDCs定义为比中尺度对流系统 (Mesoscale convective systems, MCSs) 时空尺度小的对流. 结果显示, 每年雨季青藏高原上平均的IDC数量为54.2个, 主要分布在高原的南部. IDCs的初始时刻呈现明显的日循环, 在下午14–15时为峰值, 在上午9–10时为谷值. 大部分IDCs持续时间在5小时以内, 超过一半的IDCs仅持续1小时. IDCs的冷云平均面积约为7422.9km², 其中包含65%的降水面积. IDC面积越大, 包含的强降水范围也越大. IDCs对青藏高原总降水的贡献约为20%–30%, 对极端降水贡献约为30%–40%, 在7月和8月的占比大于6月和9月. 在空间分布方面, 青藏高原上IDCs对总降水和极端降水的贡献大于周围平原地区. 青藏高原上IDCs对降水的贡献大于MCSs, 表明IDCs在该地区起着重要作用.

Extreme snowfall events over the Tibetan Plateau (TP) cause considerable damage to local society and natural ecosystems. In this study, the authors investigate the projected changes in such events over the TP and its surrounding areas based on an ensemble of a set of 21st century climate change projections using a regional climate model, RegCM4. The model is driven by five CMIP5 global climate models at a grid spacing of 25 km, under the RCP4.5 and RCP8.5 pathways. Four modified ETCCDI extreme indices—namely, SNOWTOT, S1mm, S10mm, and Sx5day—are employed to characterize the extreme snowfall events. RegCM4 generally reproduces the spatial distribution of the indices over the region, although with a tendency of overestimation. For the projected changes, a general decrease in SNOWTOT is found over most of the TP, with greater magnitude and better cross-simulation agreement over the eastern part. All the simulations project an overall decrease in S1mm, ranging from a 25% decrease in the west and to a 50% decrease in the east of the TP. Both S10mm and Sx5day are projected to decrease over the eastern part and increase over the central and western parts of the TP. Notably, S10mm shows a marked increase (more than double) with high cross-simulation agreement over the central TP. Significant increases in all four indices are found over the Tarim and Qaidam basins, and northwestern China north of the TP. The projected changes show topographic dependence over the TP in the latitudinal direction, and tend to decrease/increase in low-/high-altitude areas.

摘要

基于RegCM4区域气候模式的气候变化预估试验数据, 开展了青藏高原及其周边地区极端降雪事件的未来变化研究. 结果表明, 总降雪量在高原大部分地区呈减少趋势, 降雪日数在高原也将明显减少, 尤其是在东部. 大雪日数和五日最大降雪量在高原东部将减少, 而在中部和西部明显增加. 在高原周边的塔里木和柴达木盆地及中国西北地区, 极端降雪事件同样增加显著. 极端降雪事件在高原上呈现出东西方向上的地形依赖性, 在低/高海拔地区呈减少/增加趋势.

The Second Tibetan Plateau Scientific Expedition and Research Program tasked a research team with the “Investigation of the water vapor channel of the Yarlung Zsangbo Grand Canyon (INVC)” in the southeastern Tibetan Plateau (TP). This paper summarizes the scientific achievements obtained from the data collected by the INVC observation network and highlights the progress in investigating the development of heavy rainfall events associated with water vapor changes. The rain gauge network of the INVC can represent the impacts of the Yarlung Zsangbo Grand Canyon (YGC) topography on precipitation at the hourly scale. The microphysical characteristics of the precipitation in the YGC are different than those in the lowland area. The GPM-IMERG (Integrated Multi-satellitE Retrievals for Global Precipitation Measurement) satellite precipitation data for the YGC region should be calibrated before they are used. The meridional water vapor flux through the YGC is more important than the zonal flux for the precipitation over the southeastern TP. The decreased precipitation around the YGC region is partly due to the decreased meridional water vapor flux passing through the YGC. High-resolution numerical models can benefit precipitation forecasting in this region by using a combination of specific schemes that capture the valley wind and water vapor flux along the valley floor.

摘要

第二次青藏高原科学考察研究在青藏高原东南部组建了雅鲁藏布大峡谷水汽通道科学考察分队, 本文主要总结了该科考分队近几年开展的观测研究以及利用该分队建立的观测网收集的观测数据所取得的科学成果, 重点介绍了与大峡谷水汽输送相关的强降雨过程的研究进展; 研究主要发现科考分队在大峡谷建立的雨量筒观测网可以代表该地区地形对小时降水量的空间影响; 藏东南降水的微物理特征与低海拔地区有明显差异; GPM卫星降水数据在大峡谷地区存在干偏差的问题, 使用前需进行校准; 穿越大峡谷的经向水汽输送对青藏高原东南部的降水有重要影响, 大峡谷周边区域降水量的减少可能是由于穿越大峡谷经向水汽通量的减少造成; 使用特定云降水方案的高分辨率数值模型可以较好的捕捉大峡谷内的风场和水汽输送时, 该模型能对该地区夜间强降水做出准确预报.

The distinctive conditions present on the north and south slopes of Mount Qomolangma, along with the intricate variations in the underlying surfaces, result in notable variations in the surface energy flux patterns of the two slopes. In this paper, data from TESEBS (Topographical Enhanced Surface Energy Balance System), remote sensing data from eight cloud-free scenarios, and observational data from nine stations are utilized to examine the fluctuations in the surface heat flux on both slopes. The inclusion of MCD43A3 satellite data enhances the surface albedo, contributing to more accurate simulation outcomes. The model results are validated using observational data. The RMSEs of the net radiation, ground heat, sensible heat, and latent heat flux are 40.73, 17.09, 33.26, and 30.91 W m⁻², respectively. The net radiation flux is greater on the south slope and exhibits a rapid decline from summer to autumn. Due to the influence of the monsoon, on the north slope, the maximum sensible heat flux occurs in the pre-monsoon period in summer and the maximum latent heat flux occurs during the monsoon. The south slope experiences the highest latent heat flux in summer. The dominant flux on the north slope is sensible heat, while it is latent heat on the south slope. The seasonal variations in the ground heat flux are more pronounced on the south slope than on the north slope. Except in summer, the ground heat flux on the north slope surpasses that on the south slope.

摘要

珠穆朗玛峰南北坡独特的地形条件和复杂的下垫面, 导致了南北坡地表通量分布的显著差异. 本文利用地形增强地表能量平衡模式 (Topographical Enhanced Surface Energy Balance System (TESEBS)), 遥感数据和站点观测数据, 对季风和非季风期南北坡的地表热通量变化进行了研究. 首先, 把MCD43A3卫星数据加入TESEBS, 改进了地表反照率, 使模拟结果更准确. 受季风影响, 北坡季风期感热通量最大值出现在季风前期, 潜热通量最大值出现在季风期. 南坡季风期潜热通量最大. 全年北坡以感热交换为主, 南坡以潜热交换为主. 土壤热通量的季节变化在南坡比北坡更明显.