Atmospheric and Oceanic Science Letters最新文献

The Last Glacial Maximum (LGM; 21 000 years ago) East Asian monsoon was revisited using all available simulations performed by the latest generation of climate models participating in phase 4 of the Paleoclimate Modelling Intercomparison Project (PMIP4). With respect to the preindustrial period, all five models consistently showed a weakening of the East Asian monsoon by 1%–18% in winter and by 2%–32% in summer during that glacial period. Regionally, the LGM monsoon circulation was dominated by southerly wind anomalies in winter but northerly wind anomalies in summer over East Asia in AWI-ESM-1-1-LR, MIROC-ES2L, and MPI-ESM1-2-LR. In the two versions of CESM2, large regional differences existed in the LGM change in the East Asian monsoon, especially for summer. Such changes in the East Asian monsoon can be explained by the various geographical distributions of surface cooling and sea level pressure difference, mainly due to the large volume of ice sheets and lower atmospheric greenhouse gas concentrations during the LGM. The spread among the models and the uncertainty among the proxy data call for further simulation and reconstruction efforts to comprehend the change in the East Asian monsoon during the glacial period.

摘要

利用PMIP4多模式试验数据, 本文重新检查了末次冰盛期 (距今约21 000年) 东亚季风变化. 结果表明: 相对于工业革命前期, 所有5个模式一致模拟显示末次冰盛期东亚季风减弱, 冬季和夏季减幅分别为1 %–18 %和2–32 %; 不同模式中东亚季风环流变化的空间分布存在差异, 这主要源于该时期大尺度变冷和海平面气压梯度变化的空间分布不同; 由于模式之间的差异和重建记录之间的不确定性, 未来有待开展更多模拟和重建工作以更好地理解冰期东亚季风变化.

The Microwave Radiation Imager for the Rainfall Mission (MWRI-RM) onboard the FengYun 3G satellite (FY3G), launched in April 2023, will provide massive brightness temperature (Tb) measurements at 17 frequencies from 10.65 GHz to 183 GHz. The operationally calibrated MWRI-RM Level 1B Tb data have been released since 23 October 2023. The MWRI-RM measurements are compared with the simultaneous measurements from the GPM Microwave Imager (GMI) to provide a first overview of the MWRI-RM measurement quality. A radiative transfer model (RTM) is performed for the double difference (DD) analysis. The results show that the Tbs of MWRI-RM are in good agreement with those of GMI, with mean bias error (MBE) and root-mean-square error (RMSE) values of less than 1 K for most channels. Larger differences are observed at the horizontal polarization of 36.5 and 89 GHz, with an RMSE of about 2 K. RTM simulations reflect that the Tb difference between MWRI-RM and GMI due to the different Earth incidence angle of the sensors is about 0.5 K over the sea. The DD analysis results suggest that MWRI-RM demonstrates quite similar performance to GMI for most channels, especially for the first used channels at 166 GHz and 183 GHz.

摘要

2023年4月发射的FY-3G上搭载17个频率的测雨微波成像仪 (MWRI-RM) , 其业务定标的微波亮温 (Tb) 数据于2023年10月23日公开发布. 本文比对了发布10天的MWRI-RM与全球降水测量 (GPM) 卫星上的微波成像仪 (GMI) 相匹配的Tb数据, 并借助辐射传输模式进行双差分 (DD) 交叉定标分析, 旨在快速评估新一代MWRI-RM观测数据质量. 观测比较表明, MWRI-RM 与 GMI测量的Tb一致性很好, 大多通道的平均偏差 (MBE) 和均方根误差 (RMSE) 均小于 1 K. 两种传感器由于观测角度略有不同在水面产生约 0.5 K差异. DD分析也展示出MWRI-RM的大多数通道性能与GMI相当接近, 尤其是首次启用的高频166 GHz和183 GHz.

Siberia, neighboring the Arctic Ocean, has a cold and dry climate. The famous Siberian forest, Taiga, has been greening in recent decades, mainly driven by climate factors. Besides the warming trend, summer rainfall is also critical for the vegetation variations there. This study finds that summer mean rainfall in western Siberia significantly increases after 1995 and decreases again slightly after 2012. The extreme rainfall shows similar interdecadal variations. Three periods are identified as 1982–1994 (P1), 1995–2011 (P2), and 2012–2021 (P3). The significant anomalous cyclone/anticyclone and water vapor convergence/divergence over western Siberia are responsible for the increased/decreased summer rainfall from P1 to P2/P2 to P3. All the extreme rainfall days show strong cyclonic anomalies in the lower level and a northwest–southeast-oriented anomalous cyclone–anticyclone dipole pattern in the upper level over western Siberia. The above anomalous circulation patterns are strongest during P2, when there are more extreme rainfall days with enhanced intensity. Distinct characteristics also exist in the developing processes of extreme rainfall events in the three periods.

摘要

本文研究发现, 西西伯利亚夏季降水在1995年后显著增加, 2012年后又有所减少, 极端降水日数和强度呈现一致的变化特征. 伴随这两次降水的年代际增加/减少, 西西伯利亚上空出现异常气旋/反气旋和水汽幅合/幅散. 极端降水发生时的区域环流特征在三个时段基本一致: 西西伯利亚低空出现气旋性异常, 高空为西北–东南向的异常气旋–反气旋偶极子型. 1995–2011年期间, 极端降水日数更多, 强度更强, 上述异常环流型也更强.

Turbulent fluxes at the air–sea interface were estimated with data collected in 2011–2020 with a low‐profile platform named OCARINA during eight experiments in five regions: 2011, 2015, and 2016 in the Iroise Sea; 2012 in the tropical Atlantic; 2014 in the Chilie–Peru upwelling; 2017 and 2018 in the Mediterranean Sea, and 2018 and 2020 in Barbados. The observations were carried out with moderate winds (2–10 m s⁻¹) and average wave heights of 1.5 m. In this study, the authors used the fluxes calculated by the bulk method using OCARINA-sampled data as the input. These data can validate the fluxes estimated from ERA5 reanalysis data. The OCARINA and ERA5 data were taken concomitantly. To do this, the authors established an algorithm to extract the OCARINA data as closely as possible to the reanalysis data in time and position. The measurements of the OCARINA platform can conclude on the relevance of the widely used reanalysis data.

Compound drought events, in which several types of drought occur at the same time, usually causes more harm to human society than just one type of drought event on its own. In this study, skill scoring methods are used to evaluate models, and then several drought indices are calculated to characterize meteorological, agricultural, and hydrological droughts, separately. Finally, the projected future changes in compound drought events, and associated population and GDP exposure to them, are further studied based on CMIP6. The results show that the frequency of compound drought events is likely to increase in northern Northwest China, Southwest China, and South China, but decrease in North and Northeast China. The projected changes in duration and severity are similar to those of frequency, i.e., mainly increasing in a few parts of northern Northwest and South China, but decreasing in Northeast and North China. The population exposure to compound drought events is expected to increase greatly in the area south of the Yangtze River Basin, slightly in Northwest China, and decrease greatly in the northeast of the Yangtze River Basin. Both climate and population have important effects on the change in population exposure. Due to the expected rapid growth in GDP, the exposure of GDP to compound drought events in almost all regions of China is projected to increase in the future, especially in eastern China, and the relative contribution of the GDP effect to the change in GDP exposure will be the largest.

摘要

相较于一种类型的干旱, 几种类型的干旱同时发生的复合型干旱事件对人类社会造成的危害更加严重. 本研究采用CMIP6资料, 研究中国复合型干旱事件及其相关社会经济暴露度的未来变化. 结果表明, 西北北部, 西南和华南地区复合型干旱事件频次, 持续时间和严重程度增加, 而华北和东北地区则减少. 复合型干旱事件的人口暴露度在长江流域南部大幅增加, 在长江流域以北的东部大幅减少, 其中气候和人口均对人口暴露度的变化有重要影响. 由于GDP的快速增长, 中国未来几乎所有地区复合型干旱事件的GDP暴露度增加, 特别是在中国东部, GDP效应对GDP暴露度变化的相对贡献最大.

In July–August 2022, eastern China was hit by an extreme drought event characterized by extraordinarily long persistence. The authors selected the minimum accumulated precipitation during a consecutive seven-week period during July–August (Rx49day) as the criterion to capture persistent drought extremes. Quantified by Rx49day, the 2022 drought extreme was 57.5% dryer than the climatology, and estimated as a 1-in-73-year event based on a statistical analysis. Utilizing the DAMIP (Detection and Attribution Model Intercomparison Project) runs, the study shows that anthropogenic forcing increases the occurrence probability of a 2022Drought-like event by 56%. This change is probably associated with the change in mean state over eastern China, including decreased moisture and weakened upward motion. Further, three GHG emission scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) were employed to investigate how the risk of a 2022Drought-like event will change under global warming. The projected results show that such an event is 92% less likely to occur under the low-emissions scenario, which is related to the increased background moisture and enhanced upward motion. In sharp contrast, the high-emissions scenario simulations projected an increased occurrence probability that is 79% higher than the present-day climate, probably caused by the strengthened background descending motion. The results indicate a nonlinear change in 2022Drought-like events in response to a warmer world. It is hoped that this work will provide useful information for policymakers in developing strategies that prevent eastern China from experiencing similar natural disasters.

摘要

2022年夏季中国东部地区遭遇了一次持续性极端高温干旱事件. 本文利用CMIP6检测归因比较计划 (DAMIP) 数据, 量化了人为强迫对类2022年极端干旱事件发生概率的影响, 并基于未来不同增暖情景试验给出了此类极端干旱事件的未来变化预估. 通过分析不同外强迫因子作用下此类极端干旱事件的发生概率变化, 发现人为强迫使此类极端干旱事件的发生概率提高约56%, 这主要与人为强迫下中国东部平均水汽减少和平均上升运动减弱有关. 进一步通过分析此类极端干旱事件对不同温室气体排放情景 (SSP1-2.6, SSP2-4.5, SSP5-8.5) 的响应, 发现在低排放情景下类2022年极端干旱事件的发生概率较当今气候显著下降, 这主要与中国东部平均水汽的增加和平均环流的变化有关, 而在高排放情景 (SSP5-8.5) 下, 此类极端干旱事件的发生概率较当今气候增加约79%, 这主要与高排放情景下平均下沉运动增强有关. 该研究表明, 人为强迫通过调制气候平均背景场从而引起极端事件发生频次的变化是人类活动影响极端气候事件的重要途径之一, 极端干旱事件对温室气体排放量的响应可能是非线性的.

The authors built an electrochemical concentration cell ozonesonde and have been launching it weekly from Beijing on the North China Plain since 2013. This study is the first to use ozonesonde measurements collected over Beijing during 2013–2019 to evaluate vertical ozone profiles derived from the Atmospheric Infrared Sounder (AIRS) onboard the Aqua satellite and Microwave Limb Sounder (MLS) onboard the Aura satellite. The total column ozone calculated from the ozonesonde measurements is also compared with retrievals from AIRS and the Ozone Monitoring Instrument (OMI) onboard the Aura platform. Overall, the ozonesonde measurements and satellite retrievals show similar variability in the ozone profiles (with a relative difference mostly < 10%), albeit with a relatively large discrepancy arising at certain levels. The total column ozone derived from the three instruments shows reasonable agreement and similar annual variation. The annual average total column ozone is 351.8 ± 18.4 DU, 348.8 ± 19.5 DU, and 336.9 ± 14.2 DU for the ozonesonde, AIRS, and OMI, respectively. Further comparative analysis of ozonesonde data collected in the future from multiple sites in China will improve the understanding of their consistency with satellite retrievals over different regions in China.

摘要

从2013年开始, 作者团队使用自主研发电化学原理臭氧探空仪在华北平原北京地区进行每周一次观测. 本研究首次使用2013–2019年期间北京地区臭氧探空数据评估Aqua卫星搭载大气红外探测仪 (AIRS) 和Aura卫星搭载微波临边探测器 (MLS) 反演垂直臭氧廓线, 并对比臭氧探空, AIRS和Aura卫星搭载臭氧监测仪 (OMI) 臭氧柱总量结果. 尽管臭氧探空与卫星反演垂直臭氧廓线在局部高度处差异较大, 但整体来说两者较为接近 (相对偏差大多<10%). 臭氧探空, AIRS和OMI三种仪器测量臭氧柱总量的年变化特征较为一致, 其年均臭氧柱总量分别为351.8 ± 18.4 DU, 348.8 ± 19.5 DU和336.9 ± 14.2 DU. 后续对国内多站点观测数据分析将有助于进一步理解臭氧探空与卫星反演臭氧资料在不同区域的一致性.

The authors analyzed cold air processes of different intensities and their effect on the number of patients with respiratory illnesses visiting a hospital outpatient department in Handan City in different seasons from 2016 to 2019. For cold air events of the same intensity (apart from cold waves), the number of patients with respiratory illnesses visiting the outpatient department was highest in winter. During the cold waves, the number of patients increased sharply to greater than 55 patients per day, and the number of patients was higher in spring than in autumn. The probability density of the number of patients with respiratory illnesses visiting the outpatient department gradually changed to a positive skewness as the cold air intensity increased. Although the incidence of respiratory illnesses was the highest in winter and lowest in summer, the impact of cold air on respiratory illnesses was the largest in summer and spring, when the number of people with respiratory illnesses visiting the outpatient department increased by 18.4% and 13.3% two and five days after a cold air day. By contrast, the number people visiting the outpatient department with respiratory illnesses in winter only increased by 3.2% three days after a cold air day. The lag time of the health impact decreased with increasing cold air intensity in summer, autumn and winter, whereas the lag time was always long in spring. These findings provide a targeted basis for a scientific response to the risks to human health caused by global climate change.

摘要

本文利用2016年到2019年邯郸市气象要素和呼吸系统疾病门诊数据, 分析了不同季节不同强度的冷空气过程及其对呼吸系统疾病的影响. 结果显示: 尽管呼吸系统疾病在冬季高发, 夏季最低, 但冷空气对呼吸系统疾病的影响在夏, 春季最大, 就诊人数分别在冷空气日后两天和五天增加18.4%和13.3%, 而冬季就诊人数在冷空气日后三天仅增加3.2%.冷空气对疾病影响的滞后时间在夏, 秋和冬季随冷空气强度的增加而减少, 而春季的滞后时间总是很长. 这些发现可为科学应对气候异常导致的人群健康风险提供针对性依据.

Decadal prediction, also known as “near-term climate prediction”, aims to forecast climate changes in the next 1–10 years and is a new focus in the fields of climate prediction and climate change research. It lies between seasonal-to-interannual predictions and long-term climate change projections, combining the aspects of both the initial value problem and external forcing problem. The core technique in decadal prediction lies in the accuracy and efficiency of the assimilation methods used to initialize the model, which aims to provide the model with accurate initial conditions that incorporate observed internal climate variabilities. The initialization of decadal predictions often involves assimilating oceanic observations within a coupled framework, in which the observed signals are transmitted through the coupled processes to other components such as the atmosphere and sea ice. However, recent studies have increasingly focused on exploring coupled data assimilation (CDA) in coupled ocean–atmosphere models, based on which it has been suggested that CDA has the potential to significantly enhance the skill of decadal predictions. This paper provides a comprehensive review of the research status in three aspects of this field: initialization methods, the predictability and prediction skill for decadal climate prediction, and the future development and challenges for decadal prediction.

摘要

年代际预测, 也称为“近期气候预测”, 旨在预测未来1–10年内的气候变化, 是气候预测和气候变化研究领域的一个新关注点. 它位于季节至年际预测和长期气候变化预测之间, 结合了初值问题和外部强迫问题的两个方面. 年代际预测的核心技术在于用于模式初始化的同化方法的准确性和效率, 其目标是为模式提供准确的初始条件, 其中包含观测到的气候系统内部变率. 年代际预测的初始化通常涉及在耦合框架内同化海洋观测, 其中观测到的信号通过耦合过程传递到其他分量, 如大气和海冰. 然而, 最近的研究越来越关注在海洋-大气耦合模式中探索耦合数据同化 (CDA) , 有人认为CDA有潜力显著提高年代际预测技巧. 本文综合评述了该领域的三个方面的研究现状: 初始化方法, 年代际气候预测的可预测性和预测技巧, 以及年代际预测的未来发展和挑战.

Observations show significant trends in Southern Hemisphere extratropical climate in the late 20th century, including a strong positive trend in the austral summer Southern Hemisphere Annular Mode (SAM) accompanied by warming of the Antarctic Peninsula and melting sea ice in the Bellingshausen Sea. Statistical analysis and model simulations have shown that these trends were driven mainly by Antarctic stratospheric ozone depletion. Here, results show that the widely reported summer SAM trend has flattened since around the year 2001 against the background of the ozone recovery, supporting results from previous model simulations that predicted a slowing down of the well-documented positive summer SAM trend. Four SAM indices based on different definitions from different datasets show consistency in this slowdown. Furthermore, changes in surface air temperature (SAT) in the Antarctic and sea-ice concentration (SIC) around the Antarctic are detected. Different from the SAM, in which the signs of trends only slow down but do not reverse after the ozone recovery, the signs of trends in Antarctic SAT and SIC have reversed. The warming of the Antarctic Peninsula has turned into a cooling trend, and the melting of sea ice in the Bellingshausen Sea has turned into an increasing trend. Additional diagnostics studies with observational and model data could go a long way towards enhancing our understanding of changes in Southern Hemisphere surface climate against the background of ozone recovery.

摘要

20世纪末期, 南半球热带外地区经历了显著的气候变化, 包括夏季南半球环状模(SAM)的显著上升趋势, 伴随着南极半岛的增暖和别林斯高晋海的海冰融化. 这些趋势主要是由20世纪末期南极平流层臭氧消耗所驱动的. 本文发现, 自2001年左右以来, 在南极平流层臭氧恢复的背景下, 观测到的夏季SAM的上升趋势已经趋于平缓, 验证了前人利用数值模拟预测的夏季SAM上升趋势减缓现象. 与SAM在臭氧恢复后趋势只减缓但没有逆转不同, 南极地表气温和海冰的趋势发生了逆转. 南极半岛由变暖趋势转为降温趋势, 别林斯高晋海域的海冰由融化趋势转为增多趋势.