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Characteristics of summer rainfall droplet spectra in mountainous and non-mountainous areas of the Jianghuai region
JIN Qi, SHI Chun'e, GAO Jinlan, LU Dejin
 doi: 10.11676/qxxb2023.20220200
[Abstract](80) [FullText HTML](23) [PDF 2835KB](39)
Analysis of raindrop spectrum characteristics is an important method to study the microphysical characteristics of precipitation. In this paper, raindrop spectrum data collected at four stations in Anhui province from June to August of 2011—2012 are used to investigate raindrop spectra of convective precipitation and stratiform precipitation in mountainous and non-mountainous areas and compare their similarities and differences. The precipitation is divided into convective precipitation and stratiform precipitation according to the rainfall rate and its variation with time. The main conclusions are as follows. The mountain terrain has a greater impact on the raindrop spectrum of convective precipitation, but a smaller impact on the raindrop spectrum of stratiform precipitation. When the rainfall intensity is the same, the concentration of raindrops in convective precipitation in mountainous areas is larger than that in non-mountainous areas, while the size of raindrops is smaller than that in non-mountainous areas. The raindrop number concentration and raindrop size of convective precipitation in mountainous and non-mountainous areas both increase with rainfall intensity. The relationship between Nw (standardization parameter) and raindrop number concentration is studied. It is found that Nw is related to raindrop number concentration, but it cannot fully reflect the change of raindrop number concentration, and is not sensitive to the change of rain intensity. When the rainfall intensity is the same, the difference in raindrop number concentration between mountainous and non-mountainous convective precipitation is small, yet the difference in Nw is obvious, which indicates that Nw can better reflect the difference of precipitation mechanism between mountainous and non-mountainous areas. For weak convective precipitation with rainfall intensity less than 30 mm/h, the concentration of small raindrops in mountainous areas is relatively close to that in non-mountainous areas, while the concentration of large raindrops is lower than that in non-mountainous areas, which corresponds to a narrower spectral width of raindrops, indicating that terrain impact on raindrop spectra is more obvious. For strong convective precipitation with rainfall intensity greater than 30 mm/h, the rainfall droplet spectra in mountainous and non-mountainous areas are relatively close, which indicates that terrain impact on the rainfall droplet spectra is significantly weakened. Precipitation type have little influence on the Z (radar reflectivity)-R (rainfall rate) relationship in mountainous area.
Different ENSO impacts on early and late winter synoptic-scale air temperature variability over eastern China and possible mechanisms
WU Di, ZHANG Wenjun, GENG Xin, XUE Aoyun, HU Suqiong
 doi: 10.11676/qxxb2023.20220186
[Abstract](76) [FullText HTML](19) [PDF 4969KB](21)
Based on daily mean air temperature data from the first-generation global atmosphere reanalysis product (CRA) of China, the reconstructed monthly sea surface temperature data from National Oceanic and Atmospheric Administration (NOAA), and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) atmospheric circulation reanalysis data, the present study investigates influences of El Niño-Southern Oscillation (ENSO) on the early and late winter synoptic-scale air temperature variability over eastern China and possible mechanisms. It is revealed that the ENSO impacts differ remarkably between early and late winter. That is, the synoptic-scale air temperature response to ENSO over eastern China is weak in early winter but strong in late winter. In late winter, there is a significant positive correlation between ENSO and the synoptic temperature variability in the middle and lower reaches of the Yangtze River of eastern China. It suggests that the synoptic-scale air temperature variability and temperature fluctuation in late winters of El Niño (La Niña) years are usually stronger (weaker) than that in normal years. In late winter, ENSO can modulate the atmospheric baroclinicity by changing the meridional temperature gradient in the middle and high latitudes of Eurasia, which affects the synoptic-scale variation of atmospheric circulation in East Asia and subsequently affects the synoptic-scale air temperature variability over eastern China. Specifically, in late winters of El Niño years, the north-south temperature gradient is larger and the corresponding atmospheric baroclinicity is stronger, which could lead to more active meridional wind activities and more frequent cold air activities. Roughly opposite mechanisms apply during late winters of La Niña years. However, in early winter, ENSO has a weak influence on the meridional temperature gradient in the middle and high latitudes of Eurasia, and thus exhibits minor effects on the synoptic-scale temperature variability over eastern China. The results can enrich our understanding of the ENSO impact on air temperature variability in China, and provide references for improving seasonal prediction of wintertime air temperature over China.
Evolution of environmental circulation and dynamic and thermodynamic conditions before and after the onset of typhoon rapid intensification
GAO Shuanzhu, LÜ Xinyan
 doi: 10.11676/qxxb2023.20220175
[Abstract](74) [FullText HTML](19) [PDF 3032KB](20)
Using the tropical cyclone best track data from Shanghai Typhoon Institute of China Meteorological Administration for the period 1949—2020 and the reanalysis interim data of the European Centre for Medium-Range Weather Forecasts (ERA-Interim) for the period 1991—2020, the EOF combination analysis of u and v components of the wind field on the 200 and 850 hPa is conducted to summarize characteristics of larger-scale environmental circulation at the onset of typhoon rapid intensification and the evolutions of environmental dynamic and thermal conditions before and after the onset are further analyzed. The results indicate that in lower levels, the main environmental circulation of EOF decomposition is the confluence pattern of monsoon trough at the onset of typhoon irapid ntensification, and the circulation is conducive to low-level water vapor transport. The upper-level circulation shows obvious typhoon outflow channels, and this characteristic can be used as a typical circulation pattern for the rapid intensification forecast. The thermal condition (such as sea surface temperature, water vapor and convective instability) and the dynamic condition (such as environmental vertical wind shear and the strength of upper-level outflow) can generally reach the fitness range of conditions that are favorable for typhoon intensification. However, the values of the above environmental factors have not changed significantly or suddenly during the transition from slow intensification process to rapid intensification process. Some extreme cases even show that some of environmental factors change towards unfavorable conditions for typhoon intensification. These research results provide a reference for the prediction of typhoon rapid intensification and further typhoon studies in the future. As for the unfavorable conditions shown in some RI cases, further studied are necessary to determine whether there are other favorable factors that offset the negative effects of these conditions and what are the corresponding physical processes.
Interdecadal increase of summer precipitation in North China in early 2010s and its relationship with atmospheric circulation anomalies
ZHAO Jiacheng, LI Qingquan, DING Yihui, LIU Yunyun, TAN Guirong, SHEN Xinyong, WU Qingyuan
 doi: 10.11676/qxxb2023.20220198
[Abstract](42) [FullText HTML](10) [PDF 5551KB](16)
North China is a major agricultural and industrial production area in China with population aggregation, where drought and flood disasters will cause serious economic losses and environmental impact. Based on monthly observation data of summer precipitation in the past 61 years (1961—2021), an interdecadal variation is found in summer precipitation over North China in the early 2010s, that is, it experienced a change from dry to wet around 2011/2012. Differences in the associated atmospheric circulation over North China between the dry and wet periods are further analyzed by selecting 1999—2011/2012—2021 as the dry/wet period respectively. The results show that the change in East Asian summer monsoon bears little to the interdecadal change from dry to wet in North China, which is different from the interdecadal changes in the late 1970s and the late 1990s. During the wet period of 2011—2021, the circulations in the mid-lower troposphere show cyclonic circulation anomalies over Mongolia-Northeast China. The northerly winds on the west side of the cyclone transport cold air from the high latitudes to North China, which is conducive to the intersection of cold and warm air in the area. In the upper troposphere, the cyclone circulation anomalies over the Mongolia-Baikal Lake result in the enhancement of the East Asian westerly jet. The diagnosis of vorticity equation shows that horizontal advection term of relative vorticity significantly contributes to the northward and eastward extension of the jet, which is favorable for the enhancement of upward motion in North China. Meanwhile, the pseudo-equivalent potential temperature increases and its vertical variation enhances, indicating that the atmosphere over North China is warmer and wetter at low level with more unstable atmospheric stratification, which is also favorable for the development of anomaly upward motion. The changes in dynamic and thermal conditions lead to a significant increase in summer precipitation over North China from 2012 to 2021.
Anti-phase relation of water vapor mass between the Northern and Southern hemispheres in CMIP6 models:Differences under different greenhouse gas emission scenarios
QIAO Nian, LU Chuhan, GUAN Zhaoyong, HU Yang
 doi: 10.11676/qxxb2023.20220207
[Abstract](42) [FullText HTML](9) [PDF 4252KB](8)
Changes in water vapor mass can obviously counteract seasonal changes of the interhemispheric oscillation. In the present paper, the outputs of CMIP6 models from January 2015 to December 2100 are used to analyze seasonal cycle characteristics of water vapor mass under four greenhouse gas emission scenarios and compare with the historical run from 1958 to 2015. It is found that the water vapor mass in both hemispheres show obvious seasonal cycles. In the Northern Hemisphere, water vapor mass is characterized by low value in winter and high value in summer, while the opposite is true in the Southern Hemisphere. Regardless of the Northern and Southern Hemispheres, the annual range of water vapor mass is the smallest under the SSP1-2.6 (Shared Socioeconomic Pathway) scenario, and large water vapor mass changes occur in winter and summer. With the increase of CO2, the annual range of water vapor mass in the Northern Hemisphere under the SSP3-7.0 scenario is the largest, which increases by 26.49% compared with that of the historical run. The situation in the Southern Hemisphere is different to that in the Northern Hemisphere. With the increase of CO2 after the SSP1-2.6 scenario, the annual range of water vapor mass in the Southern Hemisphere also increases, reaching the maximum under the SSP5-8.5 scenario. The annual range of water vapor mass IHO increases with the increase of CO2 concentration, and reaches the maximum under the SSP5-8.5 scenario. However, the increase amplitude decreases. The change of CO2 concentration has the most obvious influence on the abnormal change of water vapor mass near the Equator. Meanwhile, the closer to the Antarctic, the smaller the abnormal change of water vapor mass. However, the closer to the Arctic, the greater the abnormal change of water vapor mass in summer than in winter. In addition, the increase of CO2 concentration will lead to gradual accumulation of water vapor mass in summer towards the mid-latitudes of the Northern Hemisphere. These conclusions are conducive to better understanding of the response of water vapor mass change to the increase in CO2 concentration, and provide clues to future climate policy formulation on precipitation.
Study on the Microphysical Characteristics of Ice Particles and Melting Layer in Stratiform cloud of Hebei Province
 doi: 10.11676/qxxb0.20230120
[Abstract](20) [PDF 6271KB](9)
Decay processes and statistical characteristics of continental Northeast China Cold Vortex from April to September
FAN Ziqi, ZHU Kefeng, XUE Ming
 doi: 10.11676/qxxb2023.20220171
[Abstract](102) [FullText HTML](22) [PDF 6790KB](40)
The Northeast China Cold Vortex (NCCV) is a major precipitation-producing weather system in northern China. Based on the ERA-Interim reanalysis data, the NCCV cases from April to September during 2009—2018 are identified and objectively clustered into 5 categories according to the location of the NCCV center. Among them, the northwest type, northeast type and southeast type continental NCCVs, named based on their locations, have significant impacts on northern China. The NCCV decay mainly involves two processes: The erosion of upper level PV by diabatic heating and reabsorption of the vortex PV (potential vorticity) back into the stratospheric reservoir. Statistical characteristics of the three types of continental NCCV that decay in the above two ways respectively are compared and analyzed. It is found that: (1) The decay of the northwest and southeast vortexes is mostly caused by diabatic processes, while the decay of the NCCVs is mostly attributed to reabsorption; (2) the intensity of the reabsorption decay type is generally stronger than that of diabatic decay type, as the north stratospheric reservoir is closer to the former. Besides, the latter is continuously weakened by latent heat release associated with precipitation; (3) the lifetime as well as the fraction of the decay phase for the diabatic decay type are longer than those of reabsorption decay type; (4) the location of the high-level trough relative to the NCCV and precipitation within the NCCV are two main factors that impact the NCCV decay. Strong precipitation near the NCCV center can directly erode the core of the vortex, resulting in diabatic decay. When the NCCV is ahead of or at the bottom of the high-level trough, the NCCV can be easily advected northward, leading to its absorption by the stratospheric reservoir.
Shift of the warmest water in the Indo-Pacific Warm Pool and onset of the South China Sea summer monsoon
 doi: 10.11676/qxxb2024.20230096
[Abstract](24) [PDF 3341KB](6)
Atmospheric trace gases along the R/V Beijing cruise track between China and Antarctica: Data QA/QC and preliminary results
ZOU Xuanyu, ZHAO Shoudong, TANG Jie, ZHENG Xiangdong, ZHANG Dongqi, BIAN Lingen
 doi: 10.11676/qxxb2023.20220211
[Abstract](48) [FullText HTML](15) [PDF 2846KB](18)
Atmospheric chemistry observations aboard ships are vulnerable to pollution from ship fuel engine exhaust. This local pollution leads to an increase in CO and CO2 and a decrease in O3. Concentrations (presented as volume mixing ratio) of CO, CO2, O3, CH4 and N2O in the marine-atmosphere boundary layer were measured along the R/V Beijing cruise track between Bohai bay of China and the Ross sea in Antarctica from January to April 2020. Based on the successive observations of 1-minute resolution, the impact of local pollution emission on the measured values of each trace gas is respectively implied by the persistence of variations in CO, CO2, and combinations of CO and CO2 and CO/CO2 for the study of data quality assessment quality controls (QA/QC). The results show that CO, CO2 and O3 (CH4 and N2O) data are significantly (slightly) contaminated by local pollution. A method of trace concentration difference threshold between any immediate adjacent 1-minute is proposed, which can effectively remove the outliers of CH4 and N2O from their time series datasets. The pollution period implied by CO or CO2 can be partially but not completely used to identify the contaminations in the dataset. The ratio of CO/CO2 implication can effectively determine the global baseline concentration of CO or CO2 in highly polluted region but at a high cost of discarding many data samples. The combination of CO2 and CO (CO2+CO) is the best method to imply the pollution signals in the CO2, CO and O3 datasets, and this method decreases the measured values of CO and CO2 concentrations in the southern hemisphere and the pristine region by (5—11)×10−9 (10%—18%) and (3—7)×10−6 (1%—2%) respectively, while O3 increases by (3—5)×10−9 (20%—25%). The final version concentration data of each trace gas are reasonably comparable with those measured at continental sites and the concentration differences of CO, CO2, CH4 and N2O in the southern ocean and Antarctica are respectively within 2×10−9, 0.7 ×10−6, 1.4×10−9 and 0.5×10−9. All the atmospheric trace gases data after QA/QC display their concentration features of high (low) in the northern (southern) hemisphere, and they remain stable in the south of the Southern Ocean and Antarctica region. Additionally, regional distribution characteristics of atmospheric O3 and their mechanisms are quite reasonable. All these reflect the rationality and accuracy of the proposed QA/QC method applied for the trace gases observations along the R/V Beijing cruise.
Predictors analysis and statistical prediction model establishment for summer precipitation in North China
TANG Xiao, TAO Li, DENG Minjun
 doi: 10.11676/qxxb2023.20220178
[Abstract](46) [FullText HTML](17) [PDF 24012KB](14)
Drought and flood disasters occur frequently in North China, where summer precipitation is under strong influence of the East Asian summer monsoon. Further studies are necessary to analyze predictors of summer precipitation and its seasonal prediction in North China. The first two leading modes of summer (July−August) precipitation in North China during 1981−2020 are the whole anomaly mode and dipole mode obtained by empirical orthogonal function (EOF) analysis. Based on the causality of the information flow method, the predictors of the first two leading modes of summer precipitation in North China are selected first and further screened by multiple stepwise regression, and a statistical prediction model for summer precipitation in North China is then established. Three predictors are selected for the first leading mode, i.e., 5-month-lead sea surface temperature (SST) in the western tropical Indian Ocean, 6-month-lead 850 hPa meridional wind in the West Siberian plain, and 2-month-lead 850 hPa meridional wind in the tropical mid Pacific. Four predictors are selected for the second leading mode, i.e., 2-month-lead SST in the central southern Indian Ocean, 3-month-lead outgoing longwave radiation (OLR) in the Sea of Okhotsk, 2-month-lead 850 hPa meridional wind in the tropical West Pacific, and 9-month-lead North Atlantic Oscillation (NAO). The area averaged time correlation coefficient (TCC) between the reconstructed field based on the hindcast/forecast PCs of the first two modes and observations is 0.46. The pattern correlation coefficient (PCC) between the reconstructed field based on the hindcast/forecast PCs of the first two modes and observations show a large interannual variation, and the 40-year average PCC is 0.35, which is similar to the inter-annual variation of PCC between the reconstructed field based on actual PCs of the first two modes and observations. It is found that the prediction model performs well in the years when the precipitation can be reconstructed by the first two modes. Finally, possible mechanisms for the impacts of these predictors on summer precipitation in North China are preliminarily discussed.
Research progress in observation and shape classification of natural snow and ice crystals
DUAN Jing, GUO Heng, HU Jinrong, ZHOU Xu, WU Xi, CHEN Baojun
 doi: 10.11676/qxxb2023.20220180
[Abstract](175) [FullText HTML](53) [PDF 2768KB](56)
Snow and ice crystals are important components of hydrometeors in clouds. Different shapes of snow and ice crystals are determined by their different physical formation and growth processes. Accurate observation of the shapes of snow and ice crystals is an important prerequisite for revealing the microphysical structure and precipitation mechanism of clouds. This paper summarizes studies and methods of observing crystals of ice and snow in the past half-century. The development of crystal measurement and shape classification technology for snow and ice is reviewed. The new progress of snow and ice crystal observation and shape classification and recognition technology is analyzed and summarized. The aim is to provide a reference of images for further studies of cloud microphysical structure and precipitation mechanism in China.
Retrieval of liquid water content in warm precipitating stratiform-convective clouds from airborne millimeter-wavelength radar and comparison with aircraft observations
YANG Xiao, HUANG Xingyou, SUN Hongping, WANG Yuying, LI Peiren
 doi: 10.11676/qxxb2023.20220209
[Abstract](78) [FullText HTML](16) [PDF 1931KB](29)
Liquid Water Content (LWC) is a key variable of clouds and has great implication for understanding cloud microphysical processes and validating weather modification. However, the application of relationships between reflectivity (Z) and LWC proposed in previous studies is limited. In this study, the reliability of the airborne Ka-band millimeter wavelength cloud radar (Ka-band Precipitation Radar, KPR) and cloud particle detection instruments are validated first. Cloud data collected by the radar and the particle instrument onboard airplane during 2018—2020 are then processed and smoothed within different cloud diameter ranges and radar reflectivity ranges to build a new Z-LWC relationship suitable for precipitating stratiform-convective cloud. The new relationship is $ Z=2454.71\times {\mathrm{L}\mathrm{W}\mathrm{C}}^{1.614} $, with determination coefficient of 0.995 and root mean squared error (RMSE) is 0.2 g/m3. Verification shows that the retrieved LWC is consistent with the measurements by the cloud particle detection instruments, and the discrepancy between the retrieval and observations is smaller than that between retrievals by other Z-LWC relationships and observations.
Research progress and prospect of drought formation mechanism and prediction theory and its disaster risk characteristics
 doi: 10.11676/qxxb2024.20230095
[Abstract](13) [PDF 2991KB](7)
Application of dynamic vertical change rate downscaling method in gridded temperature forecast
ZHAO Ruixia, DAI Kan, WANG Yong, CAO Yong, ZHU Yuejian, WANG Baoli
 doi: 10.11676/qxxb2023.20220208
[Abstract](60) [FullText HTML](13) [PDF 49695KB](13)
To improve spatially fine characteristics and accuracy of objective gridded temperature forecast, a dynamic vertical change rate downscaling method (DRD) considering elevation is proposed. Real-time vertical changes of surface air temperature with elevation (VCE) are calculated using the relationship between surface air temperature forecast and elevation at different grid points in the numerical model, and the results are applied to downscaling forecasts at target grids and stations to generate a more accurate initial background forecast field. Based on ECMWF model forecasts, 5 km resolution gridded elevation information, observations collected at 10154 stations and their geographic information in China, forecast experiments for spring, summer, autumn and winter are carried out. Spatial and temporal distribution characteristics of VCE, the accuracy of DRD temperature forecast and its ability to depict spatially fine characteristics are analyzed. The results show obvious diurnal, seasonal and spatial variations of VCE over China corresponding to diurnal and seasonal variations of surface long wave radiation, thermal properties and topographic dynamic effects. The value of VCE usually reaches the largest in the morning and the smallest in the evening. This means that surface air temperature decreases the slowest or increases the fastest with increasing height in the morning, and decreases the fastest or increases the slowest in the evening. Spatial variability of VCE is the largest in winter and the smallest in summer. The VCE value is closely related to the distributions of topography, land-sea, and inland lakes. Large VCE values usually appear over large topography edges, daytime land-sea margins, and inland lake edges in the daytime in spring and the whole day in summer. VCE often varies more greatly in complex terrain areas. The DRD surface air temperature forecast is significantly better than the bilinear-interpolated value of model prediction (DMO), especially over complex terrain areas. For example, the mean absolute error (MAE) of DRD forecast is about 14.3%—52.3% smaller than that of DMO over the southern Qinghai-Tibet Plateau in spring. At the same time, DRD significantly improves the ability of describing the spatially fine characteristics of surface air temperature. Overall, it is concluded that the DRD method can effectively improve the performance of objective gridded temperature forecast.
Hail size discrimination based on Bayesian method
WU Juxiu, HU Zhiqun, XIA Fan, PAN Jiawen
 doi: 10.11676/qxxb2023.20230020
[Abstract](68) [FullText HTML](15) [PDF 3038KB](27)
The size of hails directly affects the severity degree of weather disasters. To meet the need of hail size identification, based on statistical data of hails detected by two S-band dual-polarization radars in Jinan and Qingdao, a hail dataset is trained first, and the probability distributions of radar horizontal reflectance factor (ZH), differential reflectance (ZDR) and correlation coefficient (CC) for small, large and giant hails are then obtained. Finally, the hail size discrimination model (HSDM) based on Bayesian method is developed and verified by two supercell storm processes. The study yields the following results. (1) The results obtained from HSDM are consistent with the real situation and agree with the analysis of the scattering and polarization parameters characteristics of different size hails and dynamic and microphysical characteristics for supercell hail storm. (2) Horizontal and vertical distribution characteristics of hail size agree with the precipitation particles filtering mechanisms and the hail growth mechanism of supercell storm. Large hails and giant hails are mainly located in strong echo area near the front side of the V-shaped groove. On the lower side of the suspension echo of supercell, small hails are found. Large hails and giant hails are mainly generated in the high reflectance area with large gradient above the weak echo area and then fall along the strong echo wall, but smaller hails fall on the side far away from the updraft. (3) Small hails near the updraft are mainly distributed in the ZDR column, KDP column and between them, large hails and giant hails are mainly located on the other side of the KDP column away from the ZDR column. The landing concentration of heavy hails can be determined comprehensively by combining the identification results at the height below 2 km.
Mechanism analysis of a downslope windstorm outbreak
 doi: 10.11676/qxxb2024.20230083
[Abstract](26) [PDF 2900KB](5)
Characteristics of the formation and development of North Atlantic storm Eunice by satellite remote sensing
 doi: 10.11676/qxxb0.20230006
[Abstract](19) [PDF 10221KB](2)
Simulation of Moist Physics Parameterization Scheme Based on Machine Learning
 doi: 10.11676/qxxb0.20230030
[Abstract](22) [PDF 2603KB](5)
Observational analysis of the impact of Mount Tai on an extreme rainfall event at the edge of subtropical high
 doi: 10.11676/qxxb0.20230094
[Abstract](26) [PDF 6609KB](18)
Extrapolation of radar echoes based on self-attention and gated recurrent neural networks
 doi: 10.11676/qxxb0.20230053
[Abstract](27) [PDF 1359KB](7)
Differences in the effects of 10–20-day and 30–60-day low-frequency oscillations on persistent heavy rainfall during the pre-flood period in southern China and associated mechanisms
 doi: 10.11676/qxxb0.20230033
[Abstract](32) [PDF 2665KB](6)
Lightning channel state change parameterization is established and numerical simulation of cutoff and rebreakdown
 doi: 10.11676/qxxb0.20230079
[Abstract](25) [PDF 807KB](2)
Moist C-vector and its applications
 doi: 10.11676/qxxb2023.20220187
[Abstract](71) [PDF 1771KB](18)
ZDR column identification and application research of dual polarization radar based on convective storm structure
 doi: 10.11676/qxxb2023.20230050
[Abstract](124) [PDF 2162KB](74)
Reason Analysis of the Rapid Intensification of Typhoon Mekkhala in Southern Taiwan Strait
 doi: 10.11676/qxxb2023.20220217
[Abstract](37) [PDF 3913KB](13)
Variations of maximum solar radiation in Xinzhuang Shanghai during 2007-2021and its favorable circulation regimes
 doi: 10.11676/qxxb2023.20230031
[Abstract](49) [PDF 5576KB](13)
Cloud cover characteristics in Sichuan-Chongqing region based on geostationary satellite data
 doi: 10.11676/qxxb2023.20230067
[Abstract](56) [PDF 2647KB](19)
Review “21·7” extreme rainstorm in Henan
 doi: 10.11676/qxxb2023.20230038
[Abstract](107) [PDF 1879KB](61)
The impact of high-resolution orography data application on the prediction of ground meteorological elements in the CMA-MESO model
 doi: 10.11676/qxxb2023.20230010
[Abstract](35) [PDF 3261KB](7)
The characteristics and formation of seas of cloud around Mt. Lu by FY-4A satellite
 doi: 10.11676/qxxb2023.20220188
[Abstract](81) [PDF 2867KB](14)
Research on surface temperature and wind speed forecast method of Winter Olympic stations in complex terrain based on CMA-BJ numerical weather prediction model products
 doi: 10.11676/qxxb2023.20220199
[Abstract](44) [PDF 1754KB](11)
Development and Application of CMA-BJv2.0 Hourly Rapid Catch-up Cycling Assimilation and Forecast System I: Data assimilation and system construction
 doi: 10.11676/qxxb2023.20220172
[Abstract](61) [PDF 4145KB](11)
Effects of vortex structure and environment on the intensity of typhoon Hagupit(2020)
 doi: 10.11676/qxxb2023.20220163
[Abstract](48) [PDF 3350KB](19)
Quality evaluation and optimization of global microwave land surface emissivity products
 doi: 10.11676/qxxb2023.20230041
[Abstract](33) [PDF 2310KB](7)
2023year No.4
Display Method:
A spring rainstorm which was underestimated by subjective quantitative precipitation forecast struck southern North China on 21 April 2018. The mesoscale and large scale dynamic processes of the backdoor cold front and associated mesoscale convective system (MCS) were studied using high spatial and temporal resolution observations, the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis and high-resolution numerical simulations. Results showed that the rainstorm was produced by the backdoor cold front. The backdoor cold front consisted of two sections, and the western one was oriented along the south-north direction while the eastern one was oriented along the east-west direction. Cold air was concentrated below 1.5 km. With the strengthening of northeasterly or easterly winds behind the front, the front moved southward, the height of cold air dam on the east side of Taihang mountain increased, and the front intensified. The rainstorm was brought by the MCS, which occurred in the horizontal wind convergence region ahead of warm air climbing along the backdoor front. The formation and maintenance of MCS occurred near the backdoor front accompanied by frontogenesis. The enhancement of the northeasterly winds behind the front resulted in rapid southward movement of the front and higher cold air dam, while the MCS was enhanced and the convective center also moved southward. The ascending motion favorable for MCS formation was mainly contributed by the resultant force of vertical pressure gradient force and buoyancy. Diagnostic analysis showed that the large value center of the resultant force was ahead of the warm and moist air climbing along the front, corresponding to the region of large horizontal equivalent potential temperature gradient. These results explain the southward movement of the convective center and the development of MCS. This work reveals the key mesoscale dynamic processes of the MCS and backdoor cold front in spring rainstorm in North China, and sheds light on the improvement of related numerical model physical processes and forecasting techniques in the future.
To investigate the climate background for the extreme rainfall anomaly in 2021 over the mid-lower reaches of the Yellow river, this study analyzes the leading mode of autumn rainfall over the mid-lower reaches of the Yellow river during 1951—2021 and its relationship with the extreme rainfall anomaly in 2021. Rainfall data collected at 160 stations in China and NCEP/NCAR atmospheric circulation reanalysis as well as NOAA sea surface temperature (SST) reanalysis are used. The result of Empirical Orthogonal Function analysis reveals a consistent autumn rainfall pattern from the southeast of Gansu province to the west of Shandong province, which covers the mid-lower reaches of the Yellow river. This pattern is regarded as the leading mode of autumn rainfall over the mid-lower reaches of the Yellow river. The time coefficient in 2021 is the maximum since 1951, consistent with the extreme precipitation in 2021 in the region. The extreme event in 2021 is a typical example corresponding to the leading mode. This study uses the time series of Autumn Rainfall over the Yellow river (ARYR) to represent the variability of this leading mode. Analysis reveals that the interannual and interdecadal variations of this mode are affected by El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) with more rainfall during La Niña phase and negative PDO phase. Further, the leading rainfall mode over the mid-lower reaches of the Yellow river is closely related to SST anomalies in the mid-latitude North Pacific with more rainfall under higher SST. The mid-latitude North Pacific SST (MNPSST) index is calculated over the key region in the North Pacific, where the correlation is the most significant. The MNPSST index is the highest in 2021 since 1951. When the MNPSST index is high, the regressed high-level (low-level) anticyclone (cyclonic) shear occurs over the mid-lower reaches of the Yellow river, and strong upward motions develop over the mid-lower reaches of the Yellow river and the Marine Continent (MC) region. In the autumn of 2021, there are strong upward motions in the northern South China Sea, and anomalous easterly winds over the northern Pacific are obviously stronger. As a result, water vapor flux anomalies could split to southern and eastern branches, reaching the mid-lower reaches of the Yellow river basin. The leading mode of autumn rainfall over the mid-lower reaches of the Yellow river is strongly related to the intensity of SST anomaly in the North Pacific. Positive SST anomalies in the mid-latitude North Pacific are one of the most important factors affecting extreme rainfall over the mid-lower reaches of the Yellow river in autumn 2021.
Northeast Cold Vortex (NECV) is a deep cold low-pressure system occurring in the troposphere over Northeast Asia, and anomalies of its activity can often bring great uncertainty to summer precipitation prediction. To improve precipitation prediction technology, this article analyzes climatological characteristics of NECV and its influence on summer precipitation in the Haihe river basin based on precipitation data collected at more than 2400 stations in China and NCEP/NCAR reanalysis circulation data for the period 1961−2021. Machine automatic recognition, correlation analysis and regression reconstruction are employed in this study. Major results are as follows: (1) The occurrence time and geographical location of NECV have obvious climatological characteristics. It can appear all year round, and the number of cold vortex days is the largest in summer. From May to September, there are more cold vortex processes, especially in June. In summer, the center of cold vortex is located further south in June, further west in July, and further northeast in August. (2) There is no significant correlation between summer precipitation in the Haihe river basin and the overall number of days of NECV throughout the year or in summer. However, there is a significant positive correlation with the number of days of summer Western Vortex (<120°E) and a significant negative correlation with the number of days of summer Eastern Vortex (≥120°E). The frequent activities of the Western Vortex in summer are conducive to higher summer precipitation in the Haihe river basin, while the frequent activities of the Eastern Vortex in summer may result in less summer precipitation in the Haihe river basin. (3) NECV can affect summer precipitation in the Haihe river basin through anomalies of dynamic circulation and water vapor transport. Corresponding to the Western Vortex, the westerly jet at 200 hPa is significantly stronger over Haihe river basin, and Haihe river basin at 500 hPa is located in the rising zone in front of the low pressure trough in the blocking circulation pattern of "high in the east and low in the west". Meanwhile, anomalous southerly winds at 850 hPa over East Asia enhance water vapor transport to Haihe river basin. Corresponding to the Eastern Vortex, the westerly jet at 200 hPa shows no obvious anomalies over Haihe river basin, while Haihe river basin at 500 hPa is in the divergence area in front of the high pressure ridge of "low in the east and high in the west" circulation pattern, and there is no obvious water vapor transport anomaly at 850 hPa over East Asia.
Based on "The Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-Ⅲ)" and the routine meteorological operational sounding data, the European Centre for Medium-Range Weather Forecasts Fifth Generation Reanalysis (ERA-5) data, and the ISCCP cloud cover data during the summers (June, July, and August) of 2013—2015, influences of the east-west difference in the convective boundary layer (CBL) height over the Tibetan Plateau (TP) on synoptic-scale atmospheric circulation are analyzed by statistic and physical diagnosis methods. It is found that the east-west difference in CBL shows an obvious diurnal variation. The CBL is high in the west and low in the east from the noon to the late afternoon, which is mainly attributed to the larger rise of the western CBL height. Corresponding to the large east-west difference in the CBL, temporal change of surface virtual potential temperature displays a "high in the west-low in the east" feature and the change in the western TP (WTP) is larger than that in the eastern TP (ETP). Meanwhile, temperature within the CBL increases in the WTP but slightly decreases in the ETP. Pressure decreases in the CBL but increases in higher levels in the WTP. The anomalous low pressure in the WTP is shallow. At the same time, low-level pressure increases in the ETP. The low-level east-west pressure difference may result in east-west pressure gradient anomaly and anomalous southerly winds over the central TP, which is accompanied by low-level convergence and high-level divergence in the WTP. The shallow low pressure anomaly is favorable for the development of low clouds.

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