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Convection initiation (CI) has remained a major challenge in weather forecasting worldwide. The Hetao area in North China, the location of Asia’s largest irrigation area, contains highly heterogeneous vegetation where near-surface convergence lines (boundaries) parallel to the oasis–desert border often emerge over the desert and initiate convection. This study investigated the evolution of such a boundary and its influence on the CI process where a series of cells were successively initiated along the boundary on 4 June 2013. Our results indicated that uneven surface heating across the oasis–desert border produced mesoscale thermal circulation. The westerly oasis breeze in the thermal circulation converged with the southerly background wind and formed a boundary over the desert along the high-temperature contrast line. A middle-hemisphere westerly trough further enhanced uplift and facilitated CI. Our simulation revealed that the first 30-dBZ parcels in each cell originated from either the desert side at a low level or the oasis side at a middle level, rather than from the oasis at a low level, as indicated by previous idealized studies. Southerly low-level parcels veered above the boundary and experienced a longer lifting time over the desert, while western parcels originating from the oasis experienced a shorter lifting time and smaller vertical displacement, resulting in middle-level parcels instead of low-level parcels that reached their level of free convection. Even though CI occurred over a surface boundary without a near-surface stable layer, the inflow may have originated from middle levels rather than in contact with the surface. Significance Statement The purpose of this study is to understand the evolution of a real-world near-surface convergence line and the associated deep convection initiation (CI) along the border of Asia’s largest irrigation area and the desert in northern China. Notably, previous works have mainly focused on shallow convection over uneven vegetation distributions based on idealized simulations, which may be quite different from real-world interactions between thermal circulation and background flow. Our results highlight different parcel sources in different convections initiated by the same convergence line, which is different from the idealized situation where parcels mainly originate from the low-level oasis side.

This article reviews Fuqing Zhang’s contributions to mesoscale atmospheric science from research to mentoring to academic service over his 20-year career. His fundamental scientific contributions are highlighted on predictability, data assimilation, and dynamics of high impact weather, especially gravity wave and tropical cyclones. His extremely generous efforts in efficiently transmitting to the community the new scientific knowledge and ideas, through mentoring, interacting, workshop organizing, and reviewing are summarized. Special appreciations were given to his tremendous contributions to the development of mesoscale meteorology in China and the education of Chinese graduate students and young scientists.

Warm-sector heavy rainfall in southern China refers to the heavy rainfall that occurs within a weakly forced synoptic environment under the influence of monsoonal airflows. It is usually located near the southern coast and is characterized by poor predictability and a close relationship with coastal terrain. This study investigates the impacts of coastal terrain on the initiation, organization, and heavy rainfall potential of MCSs in warm-sector heavy rainfall over southern China using quasi-idealized WRF simulations and terrain-modification experiments. Typical warm-sector heavy rainfall events were selected to produce composite environments that forced the simulations. MCSs in these events all initiated in the early morning and developed into quasi-linear convective systems along the coast with a prominent back-building process. When the small coastal terrain is removed, the maximum 12-h rainfall accumulation decreases by ∼46%. The convection initiation is advanced ∼2 h with the help of orographic lifting associated with flow interaction with the coastal hills in the control experiment. Moreover, the coastal terrain weakens near-surface winds and thus decreases the deep-layer vertical wind shear component perpendicular to the coast and increases the component parallel to the coast; the coastal terrain also concentrates the moisture and instability over the coastal region by weakening the boundary layer jet. These modifications lead to faster upscale growth of convection and eventually a well-organized MCS. The coastal terrain is beneficial for back-building convection and thus persistent rainfall by providing orographic lifting for new cells on the western end of the MCS, and by facilitating a stronger and more stagnant cold pool, which stimulates new cells near its rear edge.

The impact of moist physics on the sensitive areas identified by conditional nonlinear optimal perturbation (CNOP) is examined based on four typical heavy rainfall cases in northern China through performing numerical experiments with and without moist physics. Results show that the CNOP with moist physics identifies sensitive areas corresponding to both the lower- (850−700 hPa) and upper-level (300−100 hPa) weather systems, while the CNOP without moist physics fails to capture the sensitive areas at lower levels. The reasons for the CNOP peaking at different levels can be explained in both algorithm and physics aspects. Firstly, the gradient of the cost function with respect to initial perturbations peaks at the upper level without moist physics which results in the upper-level peak of the CNOP, while it peaks at both the upper and lower levels with moist physics which results in both the upper- and lower-level peaks of the CNOP. Secondly, the upper-level sensitive area is associated with high baroclinicity, and these dynamic features can be captured by both CNOPs with and without moist physics. The lower-level sensitive area is associated with moist processes, and this thermodynamic feature can be captured only by the CNOP with moist physics. This result demonstrates the important contribution of the initial error of lower-level systems that are related to water vapor transportation to the forecast error of heavy rainfall associated weather systems, which could be an important reference for heavy rainfall observation targeting.

This study presents the radar-based characteristics and formation environment of supercells spawned by the tornadic landfalling Typhoon Mujigae (2015) in October 2015. More than 100 supercells were identified within a 24-hour period around the time of the typhoon’s landfall, of which three were tornadic with a rotational intensity clearly stronger than those of non-tornadic supercells. The identified supercells were concentrated within a relatively small area in the northeast quadrant beyond 140 km from the typhoon center. These supercells were found more likely to form over flat topography and were difficult to maintain in mountainous regions. During the study period, more supercells formed offshore than onshore. The mesocyclones of the identified supercells were characterized by a small diameter generally less than 5 km and a shallow depth generally less than 4 km above ground level. An environmental analysis revealed that the northeast quadrant had the most favorable conditions for the genesis of supercell in this typhoon case. The nondimensional supercell composite parameter (SCP) and entraining-SCP (E-SCP) were effective in separating supercell from non-supercell environment. Even though the atmosphere in the typhoon’s northeast quadrant was characterized by an E-SCP/SCP value supportive of supercell organization, orography was an impeditive factor for the supercell development. These findings support the use of traditional parameters obtained from midlatitude supercells to assess the supercell potential in a tropical cyclone envelope.

Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis, study, and forecasting of weather. Weather refers to the specific state of the atmosphere near the Earth’s surface during a short period of time. The spatial distribution of meteorological elements in the atmosphere can be represented by a variety of transient weather phenomena, which are caused by weather systems of different spatial and temporal scales. Weather is closely related to people’s life, and its development and evolution have always been the focus of atmospheric scientific research and operation. The development of synoptic meteorology is closely related to the development of observation systems, dynamical theories and numerical models. In China, observation networks have been built since the early 1950s. Up to now, a comprehensive meteorological observation system based on ground, air and space has been established. In particular, the development of a new generation of dense radar networks, the development of the Fengyun satellite series and the implementation of a series of large field experiments have brought our understanding of weather from large-scale environment to thermal dynamics, cloud microphysical structure and evolution characteristics of meso and micro-scale weather systems. The development of observation has also promoted the development of theory, numerical model and simulation. In the early days, China mainly used foreign numerical models. Lately, China has developed numerical model systems with independent intellectual property rights. Based on the results of high-resolution numerical simulations, in-depth understanding of the initiation and evolution mechanism and predictability of weather at different scales has been obtained. Synoptic meteorology has gradually changed from an initially independent development to a multidisciplinary approach, and the interaction between weather and the change of climate and environment has become a hot and frontier topic in atmospheric science. This paper reviews the important scientific and technological achievements made in China over the past 70 years in the fields of synoptic meteorology based on the literatures in China and abroad, from six aspects respectively including atmospheric dynamics, synoptic-scale weather, typhoon and tropical weather, severe convective weather, numerical weather prediction and data assimilation, weather and climate, atmospheric physics and atmospheric environment.

Warm-sector heavy rainfall in southern China refers to the heavy rainfall that occurs within the warm sector hundreds of kilometers south of a front or without a front during April–June, characterized by poor predictability and a close relationship with low-level jets (LLJs). Based on 45 warm-sector heavy rainfall episodes in 2013 and 2014 in southern China, this study examines their general characteristics and evaluates the performance of convection-permitting WRF Model simulations from an LLJ perspective. The results show that 64% of the warm-sector heavy rainfall episodes are associated with an LLJ (LLJ type) and 36% are not (no-LLJ type). The LLJ type is distinct from the no-LLJ type, with large rainfall accumulation along the coastal area. It is more common for LLJs to occur at both 800 and 925 hPa in the LLJ type, where there is a wide 800-hPa LLJ west of Guangdong Province and two 925-hPa LLJs over Beibu Gulf and the South China Sea (SCS). The coastal convergence associated with the terminus of the LLJ on 925 hPa is conducive to the coastal rainfall. WRF generally presents lower QPF skill in the LLJ type than in the no-LLJ type, due to the severe underestimation of coastal rainfall. The QPF skill of the LLJ type is significantly correlated with the forecast accuracy of LLJs, especially at 925 hPa. The north bias of the simulated LLJ on 925 hPa over the SCS and the associated overestimation of wind speed below ~900 hPa over the inland region weaken the coastal convergence and eventually lead to the underestimation in coastal precipitation.

BackgroundLymphangio vascular invasion (LVI) and perineural invasion (PNI) are associated with survival following resection for gastrointestinal cancer. But the relationship between LVI/PNI and survival of esophageal squamous cell carcinoma (ESCC) is still unclear. We aim to demonstrate the prognostic significance of LVI/PNI in ESCC.MethodsA total of 195 ESCC patients underwent curative surgery from 2012 to 2018 was collected in the 2nd Affiliated Hospital of Fujian Medical University. All the patients were divided into four groups based on the status of the neurovascular invasion: (1) neither LVI nor PNI (V0N0); (2) LVI alone (V1N0); (3) PNI alone (V0N1); (4) combined LVI and PNI (V1N1). First, the analysis included the Kaplan-Meier survival estimates with the Log rank test were performed to determine median overall survival (OS) in different groups divided according to the clinical factor, respectively. And the association between OS with multi clinical factors was examined using Cox regression analysis. Next, the risk factors for recurrence in patients with V1N1 were analyzed with univariate and multivariate logistic regression analyses, respectively.ResultsThe cases in V0N0, V1N0, V0N1, and V1N1 groups were 91 (46.7%), 62 (31.8%), 9 (4.6%) and 33 (16.9%), respectively. The OS in the four groups was different (P< 0.001). The 1-, 3- and 5-year OS in V0N0 group was higher than that in V1N1 group, respectively (1-year OS: 93.4%vs75.8%, 3-year OS: 53.8 %vs24.2%, 5-year OS: 48.1%vs10.5%). The OS in stage I-II for patients with V1N1 was significantly lower than that in the other groups (V0N0, V1N0, V0N1) (P< 0.001). The postoperative adjuvant chemotherapy was a significant impact factor of OS for ESCC patients with V1N1 (P= 0.004). Lymphatic invasion and LVI were significantly prognosis factors associated (P= 0.036,P= 0.030, respectively). The ulcerative type is a risk factor for V1N1 occurance (P= 0.040).ConclusionsThe LVI and PNI are important prognosis factors for ESCC patients. ESCC patients with simultaneous lymphangio vascular and perineural invasion (V1N1) showed worse OS than patients with either lymphangio vascular or perineural invasion alone (V1N0 or V0N1) or none (V0N0). In addition, adjuvant chemotherapy may prolong the OS for ESCC patients with V1N1.

We surveyed the occurrence of tropical cyclone (TC) tornadoes in China from 2006 to 2018. There were 64 cataloged TC tornadoes, with an average of five per year. About one-third of the landfalling TCs in China were tornadic. Consistent with previous studies, TC tornadoes preferentially formed in the afternoon shortly before and within about 36 h after landfall of the TCs. These tornadoes mainly occurred in coastal areas with relatively flat terrains. The maximum number of TC tornadoes occurred in Jiangsu and Guangdong provinces. Most of the TC tornadoes were spawned within 500 km of the TC center. Two notable characteristics were found: (1) TC tornadoes in China mainly occurred in the northeast quadrant (Earth-relative coordinates) rather than the right-front quadrant (TC motion-relative coordinates) of the parent TC circulation; and (2) most tornadoes were produced by TCs with a relatively weak intensity (tropical depressions/storms), in contrast with the United States where most tornadoes are associated with stronger TCs. Further analyses showed that TC tornadoes in China tend to be spawned in an environment with large low-level storm relative helicity and large convective available potential energy taking entrainment effects into account. TC tornadoes were particularly active in 2018, with 24 reported tornadoes accounting for 37.5% of the total surveyed samples. The first recorded tornado outbreak in the modern history of China occurred in the envelope of TC Yagi (2018), in which 11 tornadoes were reported in association with significant midlevel intrusions of dry air and the interaction of Yagi with an approaching midlatitude midlevel trough.

The Tibetan Plateau is regarded as the Earth's Third Pole, which is the source region of several major rivers that impact more 20% the world population. This high‐altitude region is reported to have been undergoing much greater rate of weather changes under global warming, but the existing reanalysis products are inadequate for depicting the state of the atmosphere, particularly with regard to the amount of precipitation and its diurnal cycle. An ensemble Kalman filter (EnKF) data assimilation system based on the limited‐area Weather Research and Forecasting (WRF) model was evaluated for use in developing a regional reanalysis over the Tibetan Plateau and the surrounding regions. A 3‐month prototype reanalysis over the summer months (June−August) of 2015 using WRF‐EnKF at a 30‐km grid spacing to assimilate nonradiance observations from the Global Telecommunications System was developed and evaluated against independent sounding and satellite observations in comparison to the ERA‐Interim and fifth European Centre for Medium‐Range Weather Forecasts Reanalysis (ERA5) global reanalysis. Results showed that both the posterior analysis and the subsequent 6‐ to 12‐hr WRF forecasts of the prototype regional reanalysis compared favorably with independent sounding observations, satellite‐based precipitation versus those from ERA‐Interim and ERA5 during the same period. In particular, the prototype regional reanalysis had clear advantages over the global reanalyses of ERA‐Interim and ERA5 in the analysis accuracy of atmospheric humidity, as well as in the subsequent downscale‐simulated precipitation intensity, spatial distribution, diurnal evolution, and extreme occurrence., Key Points A pilot reanalysis over the Tibetan Plateau using the PSU WRF‐EnKF system was developed and evaluated against independent soundings and satellite observations as well as ERA‐Interim and ERA5The pilot reanalysis had clear advantage in atmospheric humidity than existing global reanalysisThe subsequent downscaled precipitation forecasts from the pilot reanalysis compared favorably against those from the global reanalyses of ERA‐Interim and ERA5

An elevated convection initiation (CI) of a quasi-linear mesoscale convective system (MCS) that occurred in a weak-lifting environment in the early morning on 23 June 2016 in central-eastern China was investigated using observational analysis and convection-permitting numerical simulations. This MCS gradually developed into a surface-based MCS and eventually produced a strong supercell that spawned an EF4 tornado in Yancheng City of Jiangsu Province and killed 98 people. This elevated MCS was initiated ahead of a surface front without identifiable boundaries at the surface. An elevated moist absolutely unstable layer (MAUL) was found to be conducive to the CI. The MAUL provided negligible convective inhibition and contributed to CI without strong-lifting mechanisms. Numerical simulation results showed that the formation of the elevated MAUL was mainly attributed to adiabatic cooling by weak vertical ascent and sufficient horizontal moisture transport near the terminus of a low-level jet. The weak vertical ascent before the CI was sloping and was likely to be relevant to the layer-lifting process associated with the realization of potential instability. The results showed that the MAUL in this weak-lifting environment was characterized by a shallower depth, a weaker lapse rate, and a longer sustaining period than the conditions in a strong-lifting environment. The predictability of this elevated CI case was examined using a 10-member ensemble forecast. A total of 80% of the ensemble members captured the CI. Rather than a difference in lifting, whether having an elevated MAUL or not was the major difference between CI and non-CI members in the present case.

It is essential to investigate shale lithofacies distribution and controlling factor of the shale for geological evaluation of shale gas exploration and development. Through comprehensive analysis of cores, thin sections, cathode luminescence, whole-rock X-ray diffraction, element capture spectroscopy, major/trace element and other data, three major types and eight sub-type shale lithofacies in the shale of Wufeng Formation-Member 1 of Longmaxi Formation in Jiaoshiba area are identified by the three-end-member method and shale lithological classification nomenclature, and the spatiotemporal distribution law and main development controlling factors of shale lithofacies are well studied. In the Jiaoshiba area, vertically, the marine shale develops siliceous shale, mixed shale and argillaceous shale from bottom to top. Besides, lateral distribution of the shale is different from north to south; the shale lithofacies in the north area changes rapidly, the mixed shale in the north area is much thicker than that in the south area, while the siliceous shale in the south area is relatively thicker. Difference in the shale lithofacies is controlled by special sedimentary geologic events; development of the siliceous shale is controlled by the Ordovician-Silurian global volcanic event to some extent, while the mixed shale is significantly influenced by effect of bottom current, and the argillaceous shale is mainly affected by supply of terrestrial clastic material. Keywords: Shale lithofacies, Paleoproductivity, Redox condition, Volcanic activity, Bottom current, Wufeng formation-member 1 of Longmaxi Formation, Jiaoshiba area

Background This study aimed to simulate the visual field (VF) effects of patients with VF defects using deep learning and computer vision technology. Methods We collected 3,660 Humphrey visual fields (HVFs) as data samples, including 3,263 reliable 24-2 HVFs. The convolutional neural network (CNN) analyzed and converted the grayscale map of reliable samples into structured data. The artificial intelligence (AI) simulations were developed using computer vision technology. In statistical analyses, the pilot study determined 687 reliable samples to conduct clinical trials, and the two independent sample t-tests were used to calculate the difference of the cumulative gray values. Three volunteers evaluated the matching degree of shape and position between the grayscale map and the AI simulation, which was graded from 0 to100 scores. Based on the average ranking, the proportion of good and excellent grades was determined, and thus the reliability of the AI simulations was assessed. Results The reliable samples in the experimental data consisted of 1,334 normal samples and 1,929 abnormal samples. Based on the existing mature CNN model, the fully connected layer was integrated to analyze the VF damage parameters of the input images, and the prediction accuracy of the damage type of the VF defects was up to 89%. By mapping the area and damage information in the VF damage parameter quintuple data set into the real scene image and adjusting the darkening effect according to the damage parameter, the visual effects in patients were simulated in the real scene image. In the clinical validation, there was no statistically significant difference in the cumulative gray value (P>0.05). The good and excellent proportion of the average scores reached 96.0%, thus confirming the accuracy of the AI model. Conclusions An AI model with high accuracy was established to simulate the visual effects in patients with VF defects.

This study uses the Weather Research and Forecasting Model to simulate a deep convective cloud under a relatively polluted condition in South China. Ice nuclei (IN) aerosols near the surface are effectively transported upwards to above the 0 °C level by the strong updrafts in the convective cloud. Four cases with initial surface IN aerosol concentrations of 1, 10, 100, and 1000 L−1 are simulated. All simulations can well reproduce the major characteristics of the deep convective cloud in terms of the evolution, spatial distribution, and its track. IN aerosols have little effect on these macrophysical characteristics but can significantly affect ice formation. When IN concentration is increased, all heterogeneous nucleation modes are significantly enhanced, whereas the homogeneous freezing of cloud droplets is unchanged or weakened depending on the IN concentration and the development stages of the deep convective cloud. The homogeneous freezing of haze particles is generally not affected by increased IN but is slightly weakened in the extremely high IN case. As IN concentration is increased by 10 and 100 times, the enhanced heterogeneous nucleation is still not strong enough to compete with homogeneous freezing. Ice formation is hence still dominated by the homogenous freezing of cloud droplets and haze particles in the layer of 9–14 km, where most of the ice crystals are produced. The microphysical properties are generally unaffected in all the stages of cloud evolution. As IN concentration is increased by 1000 times and heterogeneous nucleation is further enhanced, the homogeneous freezing of cloud droplets and haze particles dominates only in the mature and dissipating stages, leading to unaffected ice number mixing ratio in the anvil region (approximately above 9 km) for these two stages. However, in the developing stage, when the supply of cloud droplets is limited, the homogeneous freezing of cloud droplets is weakened or even suppressed due to the very strong competition for liquid water with heterogeneous nucleation, leading to significantly lower ice number mixing ratio in the anvil regions. In addition, the microphysical properties in the convective core regions below the cloud anvil (approximately below 9 km) are also affected in the case of 1000 L−1. The enhanced heterogeneous nucleation produces more ice crystals below 9 km, leading to a stronger conversion from ice crystals to snow particles, and hence higher number and mass mixing ratios of snow. The IN effect on the spatial distributions and temporal evolutions of the surface precipitation and updraft velocity is generally insignificant.

An EF4 supercellular tornado hit Funing County, Yancheng, Jiangsu Province, China, from about 1410 to 1500 local standard time 23 June 2016, causing 98 fatalities and 846 injuries. It was the deadliest tornado in the past 40 years in China. This paper documents the storm environment, evolution of the radar signatures, real-time operational tornado warning services, and the damage distribution during this event. The tornado was spawned from a supercell that developed ahead of an upper-level trough extending southwestward from a low pressure vortex in northeast China and dissipated following the occlusion of the tornado vortex. The radar-based rotational velocity of the mesocyclone peaked at 42.2 m s−1. The strength of the tornado vortex signature (gate-to-gate azimuthal radial velocity difference) peaked at 84.5 m s−1. Surface observations at 1-min intervals from a mesoscale network of in situ surface weather stations revealed the surface wind pattern associated with the mesocyclone, such as convergent and rotational flows. The tornado formed after the peak updraft strength of the supercell, producing a damage swath that was 34.5 km long and with a maximum width of 4.1 km. The review of the tornado warning process for this event reveals that there is much work to be done to develop operational tornado forecast and warning services for China.