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2022 Vol. 27, No. 6

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Influence of the Maintenance of Upper Jet Stream on Snowstorms in the Southern Part of China
Qunjie ZUO, Wancheng ZHANG, Shouting GAO
2022, 27(6): 679-687. doi: 10.3878/j.issn.1006-9585.2021.21165
Abstract(310) HTML (41) PDF (10266KB)(43)
The effects of the kinetic energy of upper jet disturbances on snowstorms on 9 February 2014, 5 December 2015, 20 January 2016, and 20 January 2018 were analyzed using ERA-Interim data. During snowstorms, an upper jet is usually present, causing vertical upward motion that aids in developing the snowstorm. The vertical motion serves two purposes. First, it transports warm and moist air at a low level to a high level, thus providing a continuous stream of water vapor for snowstorms. Second, it transports the kinetic energy of the jet disturbances downward to a intersection area of warm and cold air at a low level. This area exhibits wind shear that provides the kinetic energy of the disturbance to the local area and further promotes the occurrence and development of snowstorms.
Evaluating Energy Fluxes of the Common Land Model Based on FLUXNET Dataset
Qi GUO, Shaofeng LIU, Hua YUAN, Hongmei LI
2022, 27(6): 688-706. doi: 10.3878/j.issn.1006-9585.2021.21084
Abstract(201) HTML (58) PDF (12070KB)(20)
Model evaluation is an important part of model development. In this study, the eddy covariance measurements from 30 FLUXNET sites of FLUXNET2015 dataset were used to evaluate the performance of the Common Land Model, version 2014 (CoLM2014) over different land-cover types, focusing on energy fluxes. The results show that the model captures the variation characteristics of sensible heat flux, latent heat flux, and net radiation flux at different time scales, such as the daily, seasonal, and annual averages, and has a good simulation ability for these fluxes. The simulation effect of net radiation is the best, followed by that of latent heat flux. When simulating seasonal variation, the spatial dispersion degree of sensible and latent heat fluxes under different vegetation types is greater in summer than in winter, and the simulation effect varies greatly among different stations. The variation range of net radiation standard deviation is smaller than sensible and latent heat fluxes, and the deviation of the simulation effect between different stations is small. The evaluation performances for evergreen needleleaf forests, savannas, grasslands, and croplands were relatively good, but poor performances were obtained when simulating the sensible heat flux in wetlands and deciduous broadleaf forests. This study provides a useful reference for improving and developing CoLM2014.
Similarities and Differences of ISO Activity Characteristics over the Tropical Indian Ocean and Pacific
Lifeng LI, Xiong CHEN, Chongyin LI, Xin LI, Minghao YANG
2022, 27(6): 707-718. doi: 10.3878/j.issn.1006-9585.2021.21158
Abstract(150) HTML (26) PDF (10714KB)(15)
The characteristics of atmospheric Intraseasonal Oscillation (ISO) activity over the tropical Indian Ocean and the Pacific are compared based on the reanalysis data. The results show seasonal jumps in the ISO activity centers over the Indian Ocean and the western Pacific in April and October. In addition, the meridional jumping distance of the ISO activity center over the western Pacific is larger than that over the Indian Ocean. The activity centers of stronger ISO are also the areas with greater annual amplitude in ISO intensity, and the ISO intensity of each activity center reached the peak at significantly different times. Considerable interannual and interdecadal variation is observed in ISO activity, and the intensity and variation trend of ISO show an obvious turning point in the 1980s. In summer, a strong northward propagation of ISO occurs over the Indian Ocean and the western Pacific. The equatorial ISO over the Indian Ocean is stronger than the ISO beyond the equator, and the ISO beyond the equator over the western Pacific is stronger than the equatorial ISO. Moreover, the northward propagation of ISO is slower over the western Pacific Ocean than over the Indian Ocean. When the ISO is active over the Indian Ocean and Western Pacific in winter and summer, its spatial distribution and vertical structure characteristics are obviously discrepant.
Analysis of the Causes of a Heavy Pollution Fog/Haze Weather in Qingdao City in January 2018
Xiaoting FAN, Ying LI, Yingchen LIU
2022, 27(6): 719-728. doi: 10.3878/j.issn.1006-9585.2022.21040
Abstract(188) HTML (44) PDF (6486KB)(28)
The pollutant trajectory, atmospheric circulation background, and meteorological factors of a heavy air pollution fog/haze event in Qingdao from 15 January to 22 January 2018, were analyzed using routine weather observation, air quality monitoring data, and ECMWF reanalysis data. The results indicate that during the early stages of pollution in Qingdao, the primary sources were the convergence and accumulation of dry and cold air from Mongolia and wet air from the Yangtze–Huaihe River basin. In the late stage, the major sources were the local air pollutants in Shandong Province, with PM10 being the primary pollutant. During the pollution process, controlled by the ural blocking high and cold low pressure in central Siberia, the East Asian transverse trough remained stable over the mid-high latitude area at 500 hPa. Over Qingdao, westerly airflow was dominant, with low wind speeds near the ground. As the transverse trough turned vertical, the zonal circulation changed to meridional, the cold air moved southward, the wind speed increased drastically, and the fog/haze dissipated rapidly. Under stable atmospheric circulation, when the surface layer had a weak wind or continuous land breeze, the ascending and descending motion of the air in the lower troposphere was weak, and the water vapor condition was favorable for the maintenance of fog/haze. Thus, by analyzing the relationship among relative humidity, PM2.5 concentration, and visibility at various stages of the process, it was observed that during the haze stage, the influence of both factors was comparable; moreover, during the fog stage, visibility was primarily affected by relative humidity, and accumulation and increase of PM2.5 concentration under static and steady conditions were the primary factors affecting visibility during the fog and haze mixing stage.
Subseasonal Evolution of the East Asian Summer Monsoon Simulated by Two BCC Climate Models Participating in CMIP6
Xiaoxiao ZHANG, Feng XUE, Xiao DONG, Renping LIN
2022, 27(6): 729-746. doi: 10.3878/j.issn.1006-9585.2021.21112
Abstract(181) HTML (28) PDF (15936KB)(20)
In this study, the simulations of the subseasonal evolution of the East Asian summer monsoon (EASM) by BCC-CSM2-MR and BCC-ESM1 models, two models from the Beijing Climate Center participating in the 6th phase of the Coupled Model Intercomparison Project (CMIP6), are analyzed, including the characteristics of the climatological mean state and features in different ENSO phases. This study compares the results of the atmospheric general circulation model (AGCM) experiments, in which the AGCM is driven by observed sea ice/sea surface temperature (AMIP experiment), with the results of the Historical experiment using the air-sea coupled model. Results show that both models can reasonably reproduce the climate mean state features of the circulation and precipitation associated with the EASM. Compared to the AGCM, the coupled model can significantly improve the simulation of the climate mean state of EASM. For instance, the coupled model simulates the subseasonal variation of the western Pacific subtropical high (WPSH) with northward and eastward shifts from June to August better. With respect to the composites for El Niño decaying years and La Niña years, the atmospheric model can simulate the westward extension (eastward retreat) of WPSH and the associated weakening (strengthening) of convection in El Niño decaying years (La Niña years) to some extent. However, there are deviations in the simulation of the location and intensity of WPSH and convection centers, particularly on a subseasonal scale. Compared to the AGCM, the coupled model does not appear to significantly improve the simulation of the subseasonal evolution of the EASM with the ENSO cycle, which may be caused by the deviation of the ENSO simulation in the coupled model. To improve the simulation of the subseasonal evolution of the EASM and its interannual variation with the ENSO phase, the simulation of ENSO in the coupled model should be enhanced.
Changes of Comfort Index over Beijing in Recent 15 Years Based on Automatic Station Data
Jiang JIANG, Jingjing MIN, Hua WANG, Ting LEI, Yuan QIAO, Zhi JIANG
2022, 27(6): 747-755. doi: 10.3878/j.issn.1006-9585.2022.21147
Abstract(144) HTML (30) PDF (3629KB)(31)
The effective temperature in Beijing has been studied by the entire available observation data. The results demonstrate the following: 1) The annual temperature, wind speed, and effective temperature in Beijing were significantly affected by the topographic distribution, without a significant difference in the relative humidity between the mountainous and the urban areas. Beijing became drier and warmer over the study period. Regionally, the stations with the largest increase in the annual and effective temperatures were concentrated in the urban areas, and the stations with the smallest increase were located in the northwest and northeast mountainous areas. Relative humidity decreased evenly across the entire area of interest. 2) According to the thermal grades of effective temperature, the temperature of winter belonged to “very cold”, that of the annual average, spring, and autumn belonged to “cold”, and that of summer belonged to “warm”. The area became dryer and warmer in the spring, summer, and winter. However, in autumn, the regional temperature difference was obvious. 3) The “weather-friendly” days in Beijing accounted for 41.3%, with large regional differences. Over half the sites showed a reduction in the number of “weather-friendly” days. The “weather-friendly” days in spring increased in number, while those in summer decreased, without any consistency in autumn. In winter, there were nearly no “weather-friendly” days, just “very cold” and “cold” days.
Multidimensional Observation Analysis of the Air Quality Changes in Wuhan during the Coronavirus Disease-2019 Pandemic
Yao WANG, Xiao TANG, Keyi CHEN, Ke HU, Shengwen LIANG, Hongyan LUO, Yating SONG, Xuechun LUO, Zifa WANG
2022, 27(6): 756-768. doi: 10.3878/j.issn.1006-9585.2022.21159
Abstract(261) HTML (22) PDF (6377KB)(28)
Based on the state-controlled sites and local-controlled sites, using the hourly monitoring data of six conventional pollutants and PM2.5 component data from 1 January to 13 February 2020, the temporal and spatial variation characteristics of air pollutants in the Wuhan area before and after the coronavirus disease 2019 (COVID-19) controls and the impact of control measures at different types of sites were evaluated. The results showed that after implementing epidemic control measures, the particulate matter concentration in Wuhan decreased significantly. Based on the calculation of two observation networks (89 stations), the change rates of PM2.5 and PM10 concentrations were −23.44% and −32.95%, respectively, but the O3 concentration increased significantly, at a rate of 55.22%, 10.6% higher than that of the state-controlled sites. In terms of the spatial distribution, the particulate matter concentration is higher in the north and lower in the south but decreases more at stations in south Wuhan, which is related to the increased frequency of southerly wind, resulting in more control measures affecting the downwind area. The decrease in NO2 concentration at the stations in the south is greater, while the O3 concentration increases. The reason is that as the NO concentration decreases greatly, the titration reaction weakens, and the meteorological conditions are also conducive to continuously accumulating O3 and maintaining a high concentration of O3. From the difference in concentration change among different types of stations, the epidemic control measures have the greatest impact on secondary pollutants at traffic and industrial stations. The concentration change rates calculated based on the two observation networks exceed those of state-controlled stations. The change rates of PM2.5 and O3 are 6% and 18% lower at state-controlled stations compared to traffic stations, respectively. The primary pollutants, SO2 and CO, show small concentration changes at rates of −6.10% and −5.61%, respectively, possibly because key emission sources were not shut down during the epidemic. Among the six conventional pollutants, the NO2 concentration changed the most, decreasing by −55.26%, which is directly related to traffic control. Comparing and analyzing the aerosol component concentrations in the same periods in 2019 and 2020 reveals that during the epidemic control period in 2020, the \begin{document}$ {\mathrm{N}\mathrm{O}}_{3}^{-} $\end{document}/\begin{document}$ {\mathrm{S}\mathrm{O}}_{4}^{2-} $\end{document} ratio decreased closer to 1, and the OC/EC ratio increased to 6.07, indicating a decrease in the proportion of mobile sources, such as automobile exhaust, and an increase in the impact of coal combustion.
Verification and Analysis of the Impact of Cold Wave Weather Process on the Numerical Prediction Skills of Wind/Photovoltaic Power Resource Elements
Ji WU, Weidong CHEN, Yucheng ZI, Ying XIAO
2022, 27(6): 769-777. doi: 10.3878/j.issn.1006-9585.2021.21173
Abstract(117) HTML (46) PDF (2543KB)(16)
Based on the reanalysis data of ERA-5 and the 120-h prediction data of Global Forecast System (GFS), which is the NCEP prediction system, this paper examines the prediction skills of near-surface wind speed and net downward short-wave radiation flux of the numerical model during nine cold waves in East China from December 2020 to March 2021. The following test results are obtained: 1) The GFS prediction system can accurately predict the cold wave process (cooling range and minimum temperature) 1–4 days in advance, with an average prediction accuracy > 80%. 2) The near-surface wind speed increases significantly during the cold wave. Even though the Threat Score (TS) of the wind speed of grades 0–2 is significantly low, the TS score of the wind speed of grades 3–5 and >6 is higher than the general weather process. The relative error in the prediction of the net downward short-wave radiation flux is larger than the general weather processes, particularly on the day of the cold wave outbreak. 3) The prediction skills exhibit significant diurnal variation, during the cold wave. The prediction skill of the wind speed of grades 0–2 is the lowest in the afternoon, particularly on the strongest day of the cold wave. The TS score of the wind speed of grades 3–5 is generally the lowest at around 1800 LST and is extremely low at night on the strongest day of the cold wave. After the afternoon, particularly on the day of the cold wave outbreak, the error in the prediction of the net downward short-wave radiation flux increases significantly. 4) The prediction skills decrease and the prediction time increases during the cold wave. The 24-h prediction has the highest TS score and the minimum error, while the 72-h prediction has the lowest TS score and the maximum error.
Analysis on the Meteorological Causes and Environmental Characteristics of a Snowstorm Event in the Dadu River Basin
Yuan CHEN, Ling YAN, Yushu ZHOU, Lingkun RAN, Shuai YANG, Fan PING
2022, 27(6): 778-786. doi: 10.3878/j.issn.1006-9585.2021.21177
A heavy snowstorm process in the reaches of the Dadu River basin in late February 2016 was analyzed. Through synoptic diagnosis and environmental meteorological parameter refinement, it was revealed that a strong cold air outbreak is a precursor of heavy snowfall in the upper reaches of the Dadu River basin, which can be predicted 2–3 days in advance. The occurrence of a blizzard requires the cooperation of cold air with warm air. For the Dadu River basin, the primary moisture sources come from two paths: 1) The plateau shear line formed by a meeting of cold air with warm and wet air in front of the south trough, which is the dominant synoptic system at the middle level in the upper reaches of the Dadu River basin. 2) The warm and humid air stream that enters the northwestern part of the Sichuan Basin at a low level along the east of the Hengduan Mountains, providing sufficient water vapor conditions for snowfall in the region. The ascending motion driven by the dynamical configuration with convergence at the low level and divergence at the high level lifts the water vapor from the low level to the upper level. The water vapor then directly sublimates into snowflakes because of the cold environment, falling in the upper reaches of the Dadu River basin. The temperature and humidity conditions during this heavy snowstorm process can be summarized as follows: The temperature at 700 hPa is not higher than −5°C, the temperature at 500 hPa is not higher than −9°C, and the surface temperature is not higher than 0°C. The relative humidity of the ambient atmosphere is higher than 70%, and the moisture content in the air reaches above 4 g kg−1.
Science and Technology Progress on Air Pollution Prevention and Control in Recent Ten Years and Future Prospect in China
Lanying WANG, Lei WANG, Wang ZHANG
2022, 27(6): 787-794. doi: 10.3878/j.issn.1006-9585.2022.22015
Facing the urgent requirements of air pollution prevention and control in China, the relevant national ministries and scientific research institutions have set up a number of scientific and technological programs to provide continuous support. Great progress has been made in theoretical research, monitoring methods, numerical simulation, and air pollution control and prevention technology, which provides a strong scientific and technological support for the practice of air pollution prevention and control in China and the successful conclusion of the battle of blue sky defense. This paper summarizes the deployment and progress of air pollution prevention and control science and technology in recent ten years, and analyzes the current situation and problems of air pollution prevention and control in China. Aiming at the 14th Five-Year Plan (2021−2025), suggestions on three aspects, that is basic research of air pollution, research and development of key technologies for pollution prevention and control, and application demonstrations are proposed. Focus on the coordination of PM2.5 and O3 control, pollution reduction and carbon reduction, the authors will further advance scientific and technological work on air pollution prevention and control, and provide key scientific and technological support for the building of a Beautiful China Planning and the goal of carbon neutrality and carbon peak.