The Antarctic Oscillation (AAO), which is the main mode of extratropical circulation in the Southern Hemisphere, also has a substantial effect on the Northern Hemisphere climate. We investigated the influence of the early AAO on the frequency of late severe pollution events (SPEF) in the Beijing-Tianjin-Hebei region (SPEFBTH) of China during winter. The results show that the winter (December-January-February) SPEFBTH is negatively correlated with the AAO from the previous autumn (August-September-October). The controlling mechanism can be briefly described as follows: the autumn AAO is positively correlated with the mid-latitude sea surface temperature (SST) in the South Atlantic Ocean. The SST preserves the autumn anomaly signal into the following winter. This anomalous SST regulates changes in the tropical western Indian Ocean-Intertropical Convergence Zone (IN-ITCZ) via air-sea coupling. Subsequently, as a response to the IN-ITCZ anomalies, anomalous wave trains are excited in the upper troposphere from the tropical western Indian Ocean to East Asia. In addition, the local meridional circulation is modulated; therefore, the circulation field and other meteorological elements favorable for the SPEFBTH appear and exacerbate the SPEFBTH. This study describes a new physical mechanism for the pathway of the AAO influence on subsequent SPEFBTH and finds a predictable source in the Southern Hemisphere air-sea system. The anomalous sea surface temperature in the mid-latitude Southern Atlantic Ocean and the anomalous Intertropical Convergence Zone in the tropical western Indian Ocean play an important role in the impact of the Antarctic Oscillation on severe pollution events in the Beijing-Tianjin-Hebei region. Autumn Antarctic Oscillation and the winter frequency of severe pollution events in the Beijing-Tianjin-Hebei region are negatively related Autumn Antarctic Oscillation achieves cross-seasonal and cross-equatorial impacts via "coupled oceanic-atmospheric bridge" Sea surface temperature and equatorial convergence zone precipitation anomalies are important components of the air-sea coupling bridge

The Yangtze River basin (YRB) and its southern region in China (20 degrees-34 degrees N, 104 degrees-123 degrees E, YRBSC) are highly susceptible to climate change and experience extreme hydrological events. To understand the spatial and temporal distribution of summer runoff in these regions, a statistical diagnosis method was applied using monthly mean runoff grid data, global Sea Surface Temperature (SST) data and meteorological reanalysis data from 1980 to 2022. The analysis revealed that variations in the isotropic phase within the YRBSC and the north-south inverse phase with the Yangtze River as the boundary are the main modes of summer runoff. Furthermore, a strong correlation was observed between winter SST anomalies (SSTAs) and late summer runoff in the YRBSC, as determined through singular value decomposition (SVD). In the first type of positive SSTA years, the eastward advance of the South Asian high pressure (SAH) and westward shift of the subtropical high pressure (SH) result in sufficient water vapour, strong upward movement and increased summer runoff. The second type of positive SSTA years exhibits a westward retreat of the SAH, upward movement north of 28 degrees N, and downward movement between 20 degrees N and 28 degrees N. These conditions, combined with water vapour intermixing and dispersion, lead to a northward increase and southward decrease of summer runoff in the YRBSC, with the boundary at 28 degrees N. Additionally, the study analysed the extreme drought situation observed in the YRB during the summer of 2022. The findings of this research provide valuable insights for ecological environmental protection, water resource planning and management in the region. This study enhances our understanding of the impact of SST on runoff. Results show a strong correlation between winter SST anomalies and late summer runoff in the Yangtze River basin and its southern region, SST affects summer runoff by influencing weather systems and is a reliable predictor of runoff. image

A previous study found that the September–October (SO) Antarctic Oscillation (AAO) shows an out‐of‐phase variation of late January–February (JF) wet and cold weather (wet–cold) in southern China. This study explored the underlying mechanism and found that Antarctic sea ice may be responsible partially for such a relationship. The SO AAO stimulates the Antarctic sea‐ice dipole pattern (ADP) anomalies, which induce the anomalous convective precipitation of the Inter‐Tropical Convergence Zone (ITCZ) in Latin America‐Atlantic (LAA) and Western Pacific (WP) in following JF. The anomalous convections over the ITCZ regions trigger planetary wave dispersions from the tropical LAA and WP to adjust the East Asian atmospheric circulation. Through the bridge of anomalous ITCZ, an increased JF ADP decreases the invasion of both northerly cold air flow and southwesterly moist airflow into southern China, resulting in the dissipation of wet–cold and vice versa. Furthermore, the variation of JF ADP is well correlated with the in‐phased polar vortex, connecting to the stratospheric Quasi‐Biennial Oscillation (QBO). The variation of JF QBO induces the anomalous convection over the tropical North Atlantic and ITCZ in LAA and WP, in turn modulating the contemporary invasion of cold and wet airflow into southern China by Rossby wave dispersion, subsequently wet–cold in southern China. To summarize, JF ADP affects the simultaneous wet–cold in southern China through the anomalous ITCZ. The turning phase of QBO modulates such correlation by inducing the anomalous ITCZ correlated with ADP and the anomalous convection due to QBO itself over tropical North Atlantic.

This study investigates the interannual cross‐seasonal association between the winter energetic particle precipitation, which is related to the geomagnetic activity (GA), and the southern annular mode (SAM) in the following summer by employing the ERA5 reanalysis dataset. The results reveal a marked negative correlation between these variables on an interannual timescale. Therefore, we analyse the GA signatures in the southern atmosphere and find that the evolution of SAM to the negative phase driven by GA may be caused by the following two mechanisms: First, for high GA levels, the middle and lower stratospheric polar vortex becomes weaker from October to November, with considerable changes in the stratospheric thermal structure and more anomalous planetary wave upwelling, accompanied by weakening of the circumpolar westerly. Over time, the anomalous signal from the upper layer can be transmitted downward and is conducive to inducing and strengthening the negative SAM in the following summer, which may serve as the stratospheric pathway for the geomagnetic impact on the SAM and Southern Hemisphere (SH) climate. Second, another possible way is that the preceding GA also appreciably regulates negative anomalies in the Ferrel circulation in SH, implying poleward anomalies in the direction of the pressure gradient, which promotes the development and enhancement of the negative phase of the SAM. In addition, easterly quasi‐biennial oscillation conditioning plays a positive role in the response of the southern atmosphere to geomagnetic forcing, thereby strengthening the connection between them.

The leading mode of the singular value decomposition (SVD) of geopotential height (GPH) and boundary layer structure index (BLSI).

Based on the Empirical Orthogonal Functions decomposition of the Sea level pressure (SLP) anomalies over the southern extratropic, the second pattern is defined as a southern second mode (SMD2), and its corresponding principal component is named the southern second mode index. The most significant feature of SMD2 is the seesaw pattern of SLP, which indicates the opposite phase of the Amundsen Low and surroundings. The spatial mode of EOF2 varies in different months but EOF2 in March is most similar to SMD2. This study shows that the March SMD2 is negatively associated with the June precipitation in southern China. The mechanisms can be briefly summarized as follows: The March SMD2 is negatively correlated with sea surface temperature (SST) in the midlatitude. Surface wind changes can affect surface heat flux and heat transport, leading to the SST changes. The SST anomaly acts as the “oceanic bridge” to preserve the March SMD2 signal and persists into late summer. The key area of SST is associated with Maritime Continent convective activity anomalies, which can excite and maintain the Pacific‐Japan pattern resulting in precipitation anomalies in south China. Through sea‐air interactions, the SMD2 can affect the precipitation in southern China across seasons. This work is expected to provide a new perspective for forecasting summer precipitation in southern China.

Alteration in Land Use/Cover (LULC) considered a major challenge over the recent decades, as it plays an important role in diminishing biodiversity, altering the macro and microclimate. Therefore, the current study was designed to examine the past 30 years (1987–2017) changes in LULC and Land Surface Temperature (LST) and also simulated for next 30 years (2047). The LULC maps were developed based on maximum probability classification while the LST was retrieved from Landsat thermal bands and Radiative Transfer Equation (RTE) method for the respective years. Different approaches were used, such as Weighted Evidence (WE), Cellular Automata (CA) and regression prediction model for the year 2047. Resultantly, the LULC classification showed increasing trend in built-up and bare soil classes (13 km2 and 89 km2), and the decreasing trend in vegetation class (−144 km2) in the study area. In the next 30 years, the built-up and bare soil classes would further rise with same speed (25 km2 and 36.53 km2), and the vegetation class would further decline (−147 km2) until 2047. Similarly for LST, the temperature range for higher classes (27 -< 30 °C) increased by about 140 km2 during 1987–2017, which would further enlarge (409 km2) until 2047. The lower LST range (15 °C to <21 °C) showed a decreasing trend (−54.94 km2) and would further decline to (−20 km2) until 2047 if it remained at the same speed. Prospective findings will be helpful for land use planners, climatologists and other scientists in reducing the increasing LST associated with LULC changes.

Land-use/land cover (LULC) changes have an impact on land surface temperature (LST) at the local, regional, and global scales. To simulate the LULC and LST changes of the environmentally important area of northern Pakistan, this research focused on spatio-temporal LULC and associated LST changes since 1987 and made predictions to 2047. We classified LULC from Landsat TM and ETM data, using the maximum probability supervised categorization approach. LST was retrieved using the Radiative Transfer Equation (RTE) methodology. Furthermore, we simulated LULC using the integrated approaches of Cellular Automata (CA) and Weighted Evidence (WE) and used a regression model to predict LST. The built-up areas and vegetation have increased by 2.1% and 11% due to a decline in the barren land by −8.5% during the last 30 years. The LULC is expected to increase, particularly the built-up and vegetation classes by 2.74% and 13.66%, respectively, and the barren land would decline by −4.2% by 2047. Consequently, the higher LST classes (i.e., 27 °C to <30 °C and ≥30 °C) soared up by about 25.18% and 34.26%, respectively, during the study period, which would further expand to 30.19% and 14.97% by 2047. The lower LST class (i.e., 12 °C to <21 °C) indicated a downtrend of about −41.29% and would further decrease to −3.13% in the next 30 years. The study findings are useful for planning and management, especially for climatologists, land-use planners, and researchers in sustainable land use with rapid urbanization.

The Antarctic Oscillation (AAO) is the dominant mode of the southern extratropical atmospheric mass variability which has potential influences on the Northern Hemisphere (NH). This study reveals a significantly negative correlation between the September–October (SO) AAO index (AAOI) and the occurrence rate of following January–February (JF) wet-cold weather (the latter is quantified by a Precipitation-Temperature (PT) Index) in Southern China (SC) especially the Middle and Lower Reaches of Yangtze River Basin (MLRY). JF PT of SC (SCPT) is modulated by both northerly air flow in the lower troposphere and southerly air flow in the middle-lower troposphere. The SO AAO stimulates Southern Ocean Dipole (SOD) pattern-like sea surface temperature anomalies (SST anomalies: SSTA), which induces a Northern Atlantic Oscillation (NAO)-like atmospheric response along with the tropical northern Atlantic (NA) precipitation anomalies in the following JF through ocean-air interaction. As for wet-cold conditions, there exists an eastward propagational wave train from the tropical-subtropical NA to the East Asian atmospheric patterns, in turn influencing the intensity of East Asian Winter Monsoon (EAWM) and Middle East Jet Stream (MEJS), subsequently the penetration of northerly cold flow and southerly wet flow into MLRY. The variation of JF SOD also regulates the local meridional-vertical cells, in turn influencing the intensity of precipitation over the tropical NA and SC, accompanied with the penetration of wet-warm flow into SC and the adjacent regions. In addition to the tropospheric processes, the stratospheric Quasi Biennial Oscillation (QBO) may serve as the stratospheric pathway for the impact of SOD on NH climate, inducing/reducing the JF SCPT response to SOD SST. To summarize, SO AAO affects the JF SCPT by modulating both dry-cold northerly air flow and wet-warm southerly air flow through tropospheric and stratospheric pathway.

利用2013～2019年武汉市生态环境局监测数据、L波段雷达探空资料、NCEP/NCAR逐日再分析资料,对夏季和秋冬季武汉地区污染日的大气污染特征、边界层结构、环流形势、物理量场进行研究,建立了武汉地区大气污染的天气概念模型.主要结论如下:(1)武汉市空气质量具有季节性变化特征,大气污染程度四季分布表现为冬＞秋＞春＞夏.夏季首要污染物是臭氧,冬季首要污染物是PM2.5.(2)比较挑选出的夏季清洁日和污染日的气象要素特征,污染日逆温的平均强度约为清洁日的一倍,逆温底高一般在600 m以下,空气质量一般为轻度-中度污染;静风频率(37.1％)明显高于清洁日的静风频率(2.9％);污染日平均风速小(0.8 m/s),边界层内相对湿度较低.同样比较秋冬季两类天气的气象要素特征,污染日逆温底高低、厚度小,不及清洁日的一半,不利于污染物的扩散,易出现重度污染天气.静风频率(20％)高于清洁日的静风频率(7.5％),风速小(1.6 m/s),污染日边界层内呈明显上千下湿的格局.(3)建立了夏季大气污染的天气概念模型,污染日副高偏弱位置偏东,长江流域易少雨干旱;地面我国东部大范围地区处于均压场中,武汉地区为偏东北异常小风,不利于大气污染物的扩散.(4)建立了秋冬季大气污染的天气概念模型,长江流域环流平直少波动,配合地面弱低压的天气形势和较强的逆温使得大气污染物聚集在近地面.蒙古冷高压强度偏弱,使得入侵我国的冷空气强度偏弱;武汉地区为偏北小风,对雾霾的移除和稀释扩散作用差.该研究结论可供大气污染预测预警研究和环境管理部门大气污染的联防联控参考.

长江上游地区的水能资源对于我国能源发展具有重要意义,研究长江上游水文的周期和突变规律,可以提前预防旱涝灾害给农业带来的损失.利用线性回归方法对长江上游清溪场水文站的水位资料进行插补延长,然后用小波分析方法和Mann-Kendall方法对三峡大坝蓄水前的1890～2002年旱季1～3月份和雨季6～8月份的水位序列的周期性、阶段性和突变特征进行了比较分析.结果 表明:(1)旱季水位在1890～ 1940年偏高,1940～2002年偏低;雨季水位在1965年以后持续偏低.(2)清溪场水文站旱季的水位存在5～8年的年际变化主周期,其中1900～1950年间5～8年的周期变化是显著的;清溪场水文站雨季水位的主周期为35年左右的年代际变化周期,1940～1960年存在8年左右的年际变化显著周期.(3)旱季水位在1933年发生突变,1933年以后水位由高向低转变,1940年以后水位持续偏低;雨季水位在1957年以后水位由高变低,1965年水位下降趋势加大,到1993年雨季水位显著降低,1997年以后雨季水位有升高的趋势.(4)长江上游流域面雨量与清溪场水位变化趋势相一致,明清小冰期东亚夏季风偏弱长江上游气候偏湿润水位整体较高,20世纪30年代、40年代全球气候相对变暖而东亚夏季风偏强,导致雨带偏北,长江上游气候转而偏干水位整体偏低.

基于2008-2017年全国自动气象观测站逐旬土壤相对湿度观测数据,综合评估中国气象局陆面数据同化系统(CMA Land Data Assimilation System,CLDAS)0～20 cm层融合土壤相对湿度产品在中国地区的适用性,评估表明CLDAS土壤相对湿度产品在中国东北、西北、江南大部及华南等地区存在较大系统性误差,总体上适用性较差.为消除CLDAS土壤相对湿度产品的系统性误差,采用回归订正法、7旬滑动平均订正法和临近加权前旬订正法对CLDAS 土壤相对湿度产品进行误差订正处理,对订正结果评估发现:订正处理后CLDAS土壤相对湿度产品与站点观测的相关性显著增加,系统偏差基本消除,适用性明显提高,3种订正方法中临近加权前旬订正法的订正效果最优.最后,采用经不同方法订正后的CLDAS土壤相对湿度产品对2017年5月东北—华北地区一次气象干旱个例进行重现,对比验证表明:相对其他两种订正方法,经临近加权前旬订正法处理后的CLDAS 土壤相对湿度产品能更为精准地重现2017年5月东北—华北地区气象干旱的落区和强度.

Wind, temperature, relative humidity and aerosol mass concentration were monitored simultaneously in Wuhan, China. Several observations were found after analyzing the physical fields of these data. It was obvious that weak pressure and saddle patterns occurred during fog-haze episodes. An inversion layer occurred before heavy fog-haze events and became thicker during fog-haze events. The boundary layer structure index was relatively higher during fog-haze days and had a significant negative correlation with the planetary boundary layer height and turbulence parameters. Wind speeds were generally less than 5 m/s and rarely exceeded this speed on the selected polluted days. Turbulence variation characteristics had special representations, especially before foghaze events. Turbulence intensities always reached abnormal peak values before fog-haze processes, while the intensities remained steady before and during pollution processes with low relative humidity. Both the turbulence kinetic energy and momentum flux decreased to near zero before heavy fog-haze processes. Momentum flux often presented abnormal disturbances before heavy fog-haze processes. These disturbances were often in an active phase before and during pollution processes with low relative humidity, a situation that is not similar to fog-haze events that maintained high relative humidity. There was a feedback mechanism between solar radiation and aerosol mass concentration, and the occurrence of turbulence anomalies may be related to the regulation of atmospheric circulation by wave-flow interaction. The results presented in this study suggest that the turbulence parameters, which display anomalies before the occurrence of heavy fog-haze processes under the background of inversion layers and stable atmospheric patterns, can serve as a means of predicting disastrous weather conditions such as fog-haze pollution.

通过计算CLDAS的0-20cm土壤相对湿度融合产品与农业气象观测站逐句10cm土壤相对湿度观测值的相关性和偏差,综合分析CLDAS在东北地区的适用性.结果 表明:CLDAS融合土壤相对湿度能较合理地反映东北地区10cm深度土壤相对湿度的空间分布,但是在对极值的描述上有所欠缺,其中CLDAS对辽宁西部和黑龙江西南部的土壤相对湿度模拟偏高较明显,而在黑龙江的东北部地区对实际土壤相对湿度的模拟偏低;总体上,CLDAS融合土壤相对湿度资料在东北地区的适用性由西南向东北方向递减,在吉林和辽宁省的适用性更好.回归订正和7旬滑动平均订正法对CLDAS产品的误差订正表明,订正结果大大提高了CLDAS产品的精度,其订正后产品可以应用于土壤湿度干旱监测业务.

从教学内容、教学方法以及教学与科研关系等方面对有中国地质大学(武汉)特色的《地理与气象学》本科生课程建设和教学改革进行探讨,并对《地理与气象学》课程的教学实践进行总结,提出了教学改革的一些经验、认识和思路,以期为搞好后续的《气候学》课程教学提供参考.

该文在考虑气温和降水影响干旱的权重不同基础上,对前人提出的降水温度均一化指标(简称S)进行修正,定义为Sm.通过对比修正前后干旱指数在干旱频率、年干旱强度以及与其他干旱指数的相关性等方面,分析了修正后效果及其在西南地区的适用性.结果 表明:Sm可以准确地描述旱季和雨季,优于S;修正前后的干旱指数在年干旱强度方面没有显著差异,但Sm减弱了S的部分不合理跳跃现象,且11a平滑得到的结果与统计事实较为一致;对比修正前后指数与相对湿润度指数(M)、综合气象干旱指数(CI)以及标准化降水指数(SPI)的相关性发现,Sm不仅矫正了S与M、CI的负相关,而且与M的相关性非常好,能较好地反映土壤的干湿状况,与各个时间尺度的SPI的相关性均超过了99％显著性检验;运用Sm定义的西南地区旱涝年具有统计学意义,且典型旱涝年的时空分布与事实一致.因此认为,Sm在西南地区有较好的适用性.

Ambient air quality monitoring data and radar tracking sonde data were used to study the atmospheric boundary layer structure (ABLS) and its changing characteristics over Wuhan. The boundary layer structure index (BLSI), which can effectively describe the ABLS, was accordingly developed and its ability to describe the near-surface air quality was analyzed. The results can be summarized as follows. (1) An analysis of the ABLS during seriously polluted cases revealed that the ABLS was usually dry and warm with a small ventilation index (VI); meanwhile, the ABLS during clean cases was usually wet and cold with a large VI. (2) The correlation between the air quality and BLSI at 100~300 m was good and passed the confidence level limit at 99%. Moreover, the correlation coefficient increased with the altitude at 10~250 m and showed a downward trend at 250~500 m. The correlation between the BLSI at 250 m and the ground air quality was the most significant (r = 0.312), indicating that the layer ranging from 0 to 250 m is essential for determining the ground air quality. (3) The BLSI considers both the vertical diffusion capability and horizontal removal capability of the atmosphere. Therefore, it is highly capable of describing the ABLS and the ground air quality.

Measurement of PM2.5 concentration, dry and wet deposition of water-soluble inorganic ions (WSII) and their deposition flux was carried out. During sampling, a total number of 31 samples of PM2.5, five wet deposition samples and seven dry deposition samples were collected. The analyses results showed that the average concentration of PM2.5 was 122.95 µg/m3 whilst that of WSII was 51.63 µg/m3, equivalent to 42% of the total mass of PM2.5. The correlation coefficients between WSII in samples of PM2.5 was significant (r = 0.50 and p-value of 0.0019). Ions of SO 4 2 − , NO 3 − , Cl − , and NH 4 + were dominant in the entire samples (PM2.5, dry and wet depositions), nevertheless, the average concentration of both SO 4 2 − and Cl − were below the China environmental quality standard for surface water. The ratio of dominant anions in wet deposition ( SO 4 2 − / NO 3 − ) was 1.59, whilst that for dry deposition ( SO 4 2 − / Cl − ) was 1.4, indicating that acidity was mainly derived from sulphate. In the case of dominant cations, the dry and wet deposition ratios ( Ca 2 + / NH 4 + ) were 1.36 and 1.37, respectively, suggesting the alkaline substances were mainly dominated by calcium salts. Days with higher recorded concentrations of PM2.5 were accompanied by dry and warm boundary layer structure, weak low-level wind and strong inversion layer.

The original version of this article unfortunately contained an error in the Figure 2 caption.

In this study, we investigated six air pollutants from 21 monitoring stations scattered throughout Wuhan city by analyzing meteorological variables in the atmospheric boundary layer (ABL) and air mass backward trajectories from HYSPLIT during the pollution events. Together with this, ground meteorological variables were also used throughout the investigation period: 1 December 2015 to 30 November 2016. Analysis results during this period show that the city was polluted in winter by PM2.5 (particulate matter with aerodynamics of less than 2.5 microns) and in summer by ozone (O3). The most polluted day during the investigation period was 25 December 2015 with an air quality index (AQI) of 330 which indicates ‘severe pollution’, while the cleanest day was 26 August 2016 with an AQI of 27 indicating ‘excellent’ air quality. The average concentration of PM2.5 (O3) on the most polluted day was 265.04 (135.82) µg/m3 and 9.10 (86.40) µg/m3 on the cleanest day. Moreover, the percentage of days which exceeded the daily average limit of NO2, PM10, PM2.5, and O3 for the whole year was 2.46%, 14.48%, 23.50%, and 39.07%, respectively, while SO2 and CO were found to be below the set daily limit. The analysis of ABL during PM2.5 pollution events showed the existence of a strong inversion layer, low relative humidity, and calm wind. These observed conditions are not favorable for horizontal and vertical dispersion of air pollutants and therefore result in pollutant accumulation. Likewise, ozone pollution events were accompanied by extended sunshine hours, high temperature, a calm wind, a strongly suspended inversion layer, and zero recorded rainfall. These general characteristics are favorable for photochemical production of ozone and accumulation of pollutants. Apart from the conditions of ABL, the results from backward trajectories suggest trans-boundary movement of air masses to be one of the important factors which determines the air quality of Wuhan.