兰州大学机构库研究单元&专题: 大气科学学院
http:///ir.lzu.edu.cn/:80/handle/262010/113469
2024-03-28T21:31:18Z
2024-03-28T21:31:18Z
Preface to the Special Issue on Causes, Impacts, and Predictability of Droughts for the Past, Present, and Future
Zhao, Tianbao
http:///ir.lzu.edu.cn/:80/handle/262010/584055
2024-03-19T01:04:50Z
2024-03-19T01:04:49Z
题名: Preface to the Special Issue on Causes, Impacts, and Predictability of Droughts for the Past, Present, and Future
作者: Zhao, Tianbao
2024-03-19T01:04:49Z
Future trends in the vertical structure of Arctic warming and moistening in different emission scenarios
Nie, Hanbin
Xie, Yongkun
Zhao, Min
Su, Zifan
http:///ir.lzu.edu.cn/:80/handle/262010/583793
2024-03-15T02:28:16Z
2024-03-15T02:28:16Z
题名: Future trends in the vertical structure of Arctic warming and moistening in different emission scenarios
作者: Nie, Hanbin; Xie, Yongkun; Zhao, Min; Su, Zifan
摘要: Arctic warming is a pressing global concern, and understanding its future vertical structure is crucial for Arctic-mid-latitude connections. In this study, we employed the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model simulations to investigate the vertical structure of Arctic warming concerning its current evolving (1980–2030) and future change (2050–2100). In addition to the dry atmosphere described only by temperature, this study analyzed humidity and moist static energy (MSE) for the moist (with the effect of moisture explicitly presented) atmosphere. Under the high-emission scenario, Arctic warming is projected to accelerate, while maintaining its existing bottom-heavy structure. Amplified humidity increases are anticipated in both the tropics and the Arctic, with the Arctic exhibiting greater moisture increases in percentage. Furthermore, we find that MSE, serving as a comprehensive metric for moist atmospheric warming, is projected to accelerate in the Arctic under the high-emission scenario. As a result, the warming of both the dry and moist atmospheres will intensify in the future, with the bottom-heavy vertical structure persisting due to enhanced warming and moistening in the lower troposphere. The accelerated Arctic moistening in the future is due to meridional atmospheric moisture transport in the summer and local moisture source in the winter. In contrast, under the intermediate-emission scenario, Arctic warming and moistening are not projected to accelerate. Despite the inter-model discrepancy, our findings underscore the reliability of projections derived from the high-emission scenario. In summary, our findings highlight that the bottom-heavy vertical structure of Arctic warming will not change and that enhanced upper-level Arctic warming will not occur in the future. © 2024 Elsevier B.V.
2024-03-15T02:28:16Z
The applicability of numerical model and machine learning for near-surface ozone simulation in Lanzhou City
Zhou, Heng-Zuo
Liao, Peng
Yang, Hong
Chen, Heng-Rui
Luo, Yi-Ming
Pan, Feng
Tong, Ji-Long
Liu, Yong-Le
http:///ir.lzu.edu.cn/:80/handle/262010/583780
2024-03-15T02:27:51Z
2024-03-15T02:27:51Z
题名: The applicability of numerical model and machine learning for near-surface ozone simulation in Lanzhou City
作者: Zhou, Heng-Zuo; Liao, Peng; Yang, Hong; Chen, Heng-Rui; Luo, Yi-Ming; Pan, Feng; Tong, Ji-Long; Liu, Yong-Le
摘要: Numerical- and machine learning models with three different chemical mechanisms (CBMZ, RADM2, and CB06r3) were applied to simulate the near-surface ozone concentration in Lanzhou city in July 2019. Results show that CBMZ performed better than both RADM2 and CB06r3 did of which RADM2led to an overestimate of the near-surface ozone concentration while CB06r3 to a slightly underestimate. Then, the results from two machine learning models (XGBoost and PSO-BP) showed that in the absence of atmospheric pollutant emission inventory and only meteorological data were used, both two machine learning models performed better, regardless of single site or spatial distribution. In addition, the XGBoost model performed better for simulating the spatial distribution of near-surface ozone concentrations. Overall, the two machine learning models computed faster than the numerical models, but were significantly influenced by the input data, implying that the numerical models are more suitable for simulating pollution processes. Generally, a model suitable for simulating ground-level ozone should be selected according to the simulation requirements and data conditions. © 2024 Chinese Society for Environmental Sciences. All rights reserved.
2024-03-15T02:27:51Z
Neural network-based climate index: Advancing rainfall prediction in EI Niño contexts
Fan, Peiyi
Yang, Jie
Chen, Zheng
Zhao, Junhu
Zang, Naihui
Feng, Guolin
http:///ir.lzu.edu.cn/:80/handle/262010/583747
2024-03-15T02:25:59Z
2024-03-15T02:25:58Z
题名: Neural network-based climate index: Advancing rainfall prediction in EI Niño contexts
作者: Fan, Peiyi; Yang, Jie; Chen, Zheng; Zhao, Junhu; Zang, Naihui; Feng, Guolin
摘要: Accurate short-term climate predictions, specifically the prediction of dominant rain belts during flood seasons, represent a significant challenge, particularly in the absence of notable external forcing signal anomalies in the previous winter. To address this challenge, we propose a novel climate index based on an Auto-Encoder (AE) Neural Network that exhibits superior performance in indicating several significant precipitation events in the Yangtze and Huaihe River Basins under varying El Niño conditions. Notably, the novel climate index rectifies the discrepancy between the 2019/2020 Niño index and the 2020 summer precipitation. In order to understand the information source of AE, the causality between AE and other indices was further analyzed by Granger Causality. The results show that AE index mainly contains the information of subtropical high index and ocean index, which is consistent with previous studies. © 2024 Elsevier B.V.
2024-03-15T02:25:58Z
Influence of nose angle on performance of dense medium cyclones with volute inlet
Cai, Qinyu
Hu, Yuyang
Zhang, Zihui
Tao, Mingqing
Huo, Huanhuan
Dong, Kejun
Zhang, Yumeng
Wang, Bo
http:///ir.lzu.edu.cn/:80/handle/262010/583720
2024-03-15T02:25:10Z
2024-03-15T02:25:09Z
题名: Influence of nose angle on performance of dense medium cyclones with volute inlet
作者: Cai, Qinyu; Hu, Yuyang; Zhang, Zihui; Tao, Mingqing; Huo, Huanhuan; Dong, Kejun; Zhang, Yumeng; Wang, Bo
摘要: Dense medium cyclones (DMCs) are widely used in coal mine sorting processes to improve the quality of coal products and reduce pollution. The conventional linear inlet DMCs has the problems of unstable flow field, high turbulence density and low separation efficiency. Based on these concerns, the volute inlet DMCs was proposed, however the nose angle as one of the most critical parameters has not yet been investigated in depth. In this paper, a DMC with volute inlet is investigated, and the effect of nose angle is studied by a computational fluid dynamics model in terms of flow field, particle motion and the forces acting on the particles. The performance of the DMC is evaluated with respect to the inlet nose angle. As the nose angle increases from 0 to 180 deg., the separation efficiency has a tendency to increase and then decrease with the inflection point founding when nose angle is 180 deg. Then the flow field, particle distribution and particle force are analyzed respectively. The results show that the symmetry and stability of the flow field can be significantly improved as nose angle increases from 0 to 180 deg., but they remain almost constant when nose angle is 270°. In addition, a quantification method of the short-circuiting flow is established and it has been found that increasing the nose angle can notably reduce the short-circuiting flow. In terms of particle phase, increasing the nose angle causes heavier particle distribution tends to concentrate. During this period, the variation pattern of forces on particles with different nose angles is also analyzed. The DMC with a nose angle of 180 deg. has a longer acceleration zone at the entrance height and an increased radial force on the particles, which results in better performance. This study provides a theoretical basis and reference for the structure optimization of dense medium cyclones. © 2024 Elsevier B.V.
2024-03-15T02:25:09Z
A specific stratospheric precursory signal of overshooting convective systems over the southern slope of the Tibetan Plateau
Tian, Hongying
Zhao, Qinghong
Wang, Yan
Chao, Luyao
Tu, Xiaoxu
http:///ir.lzu.edu.cn/:80/handle/262010/583716
2024-03-15T02:25:00Z
2024-03-15T02:24:59Z
题名: A specific stratospheric precursory signal of overshooting convective systems over the southern slope of the Tibetan Plateau
作者: Tian, Hongying; Zhao, Qinghong; Wang, Yan; Chao, Luyao; Tu, Xiaoxu
摘要: Using the TRMM PR observations, ERA5 reanalysis and Outgoing Longwave Radiation (OLR) datasets, a specific stratospheric precursory signal to the occurrence of overshooting convective systems (OCSs) over the southern slope of the Tibetan Plateau (SSTP) is investigated. We compared two types of OCS events: OCSs associated with stratospheric intrusions and other OCSs. The results indicate that there is a notable decline in the tropopause height starting two days before to on the day of the OCS onset for OCSs associated with stratospheric intrusions, but the tropopause height for other OCSs increases with the occurrence of OCS. It is found that the descending of the tropopause height is accompanied by downward intrusion of stratospheric high potential vorticity (PV) air into the troposphere for the OCSs associated with stratospheric intrusions. The increase in PV near the tropopause can cause an increase in temperature and relative vorticity near the tropopause. The OCSs associated with stratospheric intrusions are closely related to strong synoptic variability. As the stratospheric intrusion deepens on the day of the OCS onset, increased relative vorticity near the tropopause, stronger upward motion in the troposphere associated with divergence and convergence, more specific humidity in the troposphere, and weakened static stability in the middle troposphere are found within the OCS region, which are conducive to the development of deep convection that penetrates into the stratospheric intrusion. Compared with OCSs associated with stratospheric intrusions, other OCS events are characterized by stronger high cloud cover (HCC) and negative Outgoing Longwave Radiation (OLR) anomaly, as well as higher upward movement in the troposphere. This is conducive to other OCSs occurring in a more barotropic convective environment characteristic of the Asian monsoon, the vertical development height of weakened static stability and upward motion are higher, promoting the development of convective activity to higher altitudes and penetrating into the tropopause, thereby causing the uplift of the tropopause. © 2024 Elsevier B.V.
2024-03-15T02:24:59Z
Prediction of seasonal sea surface temperature based on temperature and salinity of subsurface ocean using machine learning
Wei, Sentao
Wang, Chenghai
Zhang, Feimin
Yang, Kai
http:///ir.lzu.edu.cn/:80/handle/262010/583618
2024-03-15T02:26:41Z
2024-03-15T02:12:04Z
题名: Prediction of seasonal sea surface temperature based on temperature and salinity of subsurface ocean using machine learning
作者: Wei, Sentao; Wang, Chenghai; Zhang, Feimin; Yang, Kai
摘要: The sea surface temperature (SST) is not only a crucial external factor in the evolution of the atmosphere, but also a primary factor and premonition signal used in climate prediction. It is challenging to obtain a precise SST for generating accurate initial and boundary conditions in numerical models. This study employs a machine learning approach, that is, a convolutional neural network (CNN) algorithm, to predict SST on a seasonal scale. In particular, the subsurface ocean temperature (OT) and ocean salinity (OS) at depths of 5.02, 15.08, 25.16, 35.28, 45.45 and 76.55 m were used as training factors in developing a CNN prediction model. The results indicate that subsurface OT and OS can persist for 6 months or longer, with a maximum persistence of up to 12 months. Using the CNN prediction model, the SST can be reliably predicted 6 months in advance in most cases. The predicted SST has a mean bias of approximately 0-0.8 K on the globe. The bias is small (below 0.5 K) in the open ocean. The root mean square errors (RMSEs) of hindcasting for Interdecadal Pacific Oscillation, North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation indices are all less than 1.0 K. Specifically, the RMSE for El Nino prediction is less than 0.5 K. This study provides a viable method for establishing initial and boundary conditions for climate prediction. It is challenging to obtain a precise sea surface temperature (SST) for generating accurate initial and boundary conditions in numerical models. This study employs a machine learning approach, which is a convolutional neural network algorithm, to predict SST on a seasonal scale. image
2024-03-15T02:12:04Z
Impacts of stratospheric polar vortex changes on tropospheric blockings over the Atlantic region
Zhang, Chongyang
Zhang, Jiankai
Xia, Xufan
Song, Jibin
Li, Douwang
Tian, Wenshou
http:///ir.lzu.edu.cn/:80/handle/262010/583608
2024-03-15T02:11:51Z
2024-03-15T02:11:50Z
题名: Impacts of stratospheric polar vortex changes on tropospheric blockings over the Atlantic region
作者: Zhang, Chongyang; Zhang, Jiankai; Xia, Xufan; Song, Jibin; Li, Douwang; Tian, Wenshou
摘要: In recent years, extreme weather events associated with atmospheric blocking in the northern extratropics have become more frequent. This study has revealed the impacts of the stratospheric polar vortex on the blockings over the North Atlantic sector, using both reanalysis data and large-ensemble experiments performed by general circulation model. It is found that a weak stratospheric polar vortex (WPV) can cause more blockings to be generated over Greenland and move more westward than normal, while a strong stratospheric polar vortex (SPV) can cause more blockings to be generated over the south of Greenland and Western Europe. The stratospheric polar vortex could influence blocking anomalies by modulating both synoptic-scale eddy and planetary wave activities. Under WPV conditions, the generation of synoptic-scale eddies is suppressed due to decreased upper-troposphere background baroclinicity, which is favorable for positive geopotential height anomalies and more blockings over Greenland. Additionally, WPV can suppress the planetary wave train that is accompanied with lower pressure center over Greenland, further contributing to the positive geopotential height anomalies and more blockings over Greenland. The abovementioned processes under SPV conditions are nearly opposite to those under WPV conditions.
2024-03-15T02:11:50Z
Warming Climate-Induced Changes in Cloud Vertical Distribution Possibly Exacerbate Intra-Atmospheric Heating Over the Tibetan Plateau
Zhao, Yang
Li, Jiming
Wang, Yifei
Zhang, Weiyuan
Wen, Deyu
http:///ir.lzu.edu.cn/:80/handle/262010/583575
2024-03-15T02:27:36Z
2024-03-15T02:10:46Z
题名: Warming Climate-Induced Changes in Cloud Vertical Distribution Possibly Exacerbate Intra-Atmospheric Heating Over the Tibetan Plateau
作者: Zhao, Yang; Li, Jiming; Wang, Yifei; Zhang, Weiyuan; Wen, Deyu
摘要: The complex and diverse cloud vertical distribution (CVD) largely impacts radiative and precipitation properties of clouds. Using 10-year active satellite observations, we classified CVD over the Tibetan Plateau into 12 categories and found that overlapping clouds have less frequency but stronger radiative effect, heating rate and larger precipitation (partly reflecting the seeding effect) compared with single-layer non-strong convective clouds. Under a warming climate due to uniform sea surface temperature increase of 4K (quadrupling CO2 increase), extremely high (>10 km) ice clouds will increase, particularly those below the tropopause will increase slightly (largely), accompanied by clear (weak) increases in stratospheric clouds. Simultaneously, a moderate to rapid decrease will occur in clouds below 10 km. Such CVD changes could further exacerbate tropopause warming. The probability of cloud overlap is also likely to increase in warmer climates, thus possibly further causing non-convective cloud systems with stronger intra-atmospheric heating, larger precipitation intensity and proportion.
2024-03-15T02:10:46Z
Quantifying vehicle restriction related PM2.5 reduction using field observations in an isolated urban basin
Guo, Yumin
Tian, Pengfei
Li, Mengqi
Yu, Zeren
Song, Xin
Shi, Jinsen
Chang, Yi
Zhang, Lei
http:///ir.lzu.edu.cn/:80/handle/262010/583545
2024-03-15T02:10:01Z
2024-03-15T02:10:00Z
题名: Quantifying vehicle restriction related PM2.5 reduction using field observations in an isolated urban basin
作者: Guo, Yumin; Tian, Pengfei; Li, Mengqi; Yu, Zeren; Song, Xin; Shi, Jinsen; Chang, Yi; Zhang, Lei
摘要: Vehicle (related particulate matter) emissions, including primary vehicle (related particulate matter) emissions, secondary nitrate, and road dust, have become an important source of fine particulate matter (PM2.5) in many cities across the world. The relationship between vehicle emissions and PM2.5 during vehicle restrictions has not yet been revealed using field observational data. To address this issue, a three-month field campaign on physical and chemical characteristics of PM2.5 at hourly resolution was conducted in Lanzhou, an urban basin with a semi-arid climate. The Lanzhou municipal government implemented more strict vehicle restriction measure during the latter part of field campaign period. The concentration of nitrogen oxides (NOx) and PM2.5 decreased by 15.6% and 10.6%, respectively during the strict vehicle restriction period. The daily traffic fluxes decreased by 11.8% due to the vehicle restriction measure. The vehicle emission reduction led to a decrease of 2.43 mu gm(-3) in PM2.5, including the decrease of primary vehicle emissions, secondary nitrate, and road dust. The contribution of vehicle emissions to PM2.5 decreased by 9.0% based on the results derived from a positive matrix factorization model. The sources other than vehicle emissions increased by 0.2 mu gm(-3). Combining all evidence from the observations, the reduction of vehicle emissions is almost equal to the observed reduction in PM2.5. A further extrapolation that 9.0% reduction in vehicle emissions led to the observed reduction in PM2.5 (2.32 mu gm(-3)). This study clearly quantifies the vehicle restriction related PM2.5 reduction using field observations. The results provide scientific support for the implementation of effective vehicle emission reduction measures.
2024-03-15T02:10:00Z