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Tornadoes, as highly destructive weather events, require accurate detection for effective decision‐making. Traditional radar‐based tornado detection algorithms (TDA) face challenges with limited tornado feature extraction capabilities, leading to high false alarm rates and low detection probabilities. This study introduces the Multi‐Task Identification Network (MTI‐Net), leveraging Doppler radar data to enhance tornado recognition. MTI‐Net integrates tornado detection and estimation tasks to acquire comprehensive spatial and locational information. As part of MTI‐Net, we introduce a novel backbone network of Multi‐Head Convolutional Block (MHCB), which incorporates Spatial and Channel Attention Units (SAU and CAU). SAU optimizes local tornado feature extraction, while CAU reduces false alarms by enhancing dependencies among input variables. Experiments demonstrate the superiority of MTI‐Net over TDA, with a decrease in false alarm rates from 0.94 to 0.46 and an increase in hit rates from 0.23 to 0.81, highlighting the effectiveness of MTI‐Net in handling small‐scale tornado events. Plain Language Summary: Tornadoes, highly destructive small‐scale weather phenomena, demand accurate detection for informed decision‐making. Although meteorological radars are commonly utilized for tornado identification, current methods often suffer from false alarms or missed detections due to radar noise. In this study, we introduce the multi‐task learning‐based identification network (MTI‐Net), which not only enables tornado detection but also estimates tornado counts within radar data. We integrate Convolutional Neural Networks (CNNs) with Transformer techniques to enhance the model's ability to capture tornado information. CNNs detect local details using filters, while Transformers manage global connections through attention mechanisms. A series of experiments demonstrate significant improvements in tornado detection with MTI‐Net compared to traditional methods. Key Points: A tornado dataset with detailed radar features was created over China from 2017 to 2023Multi‐task learning was designed to simultaneously infer tornado detection and tornado number estimationIntegration of spatial and channel attention units can better extract tornado features from radar data [ABSTRACT FROM AUTHOR]

We present the first continuous observations of three‐dimensional spatially resolved wind fields and atmospheric motions in the mesosphere and lower thermosphere in the mid‐latitudes of the Northern Hemisphere. Our observations were performed during a 19‐month campaign from January 2022 to July 2023 and exploited the composite data from the first multistatic meteor radar system in China and an adjacent monostatic meteor radar. To retrieve the atmospheric kinetic properties, we introduce an improved volume velocity processing method including coordinate transformations and non‐linear constraints to minimize errors. The vertical winds are estimated separately from the iteration of the horizontal divergence to avoid potential biases or contamination from the horizontal winds. The winds and air motions show annual/semiannual variation characteristics within certain altitudes, usually more variable around the equinoxes. The vertical winds are basically within the magnitude of 1 m/s and are upward as expected at the mesopause during the summer, which corresponds to the adiabatic cooling. Plain Language Summary: The mesosphere and lower thermosphere (MLT) is a coupling region between the upper and lower atmosphere and contains various dynamic and chemical processes. Meteor is a convenient and reliable tool for MLT mean horizontal wind observations. Multistatic meteor radars can investigate the more sophisticated dynamic properties of the MLT winds from different viewing angles. In this work, for the first time, we reported 3‐dimensional spatially resolved MLT winds and atmospheric motions in the mid‐latitudes of the Northern Hemisphere. To minimize errors in the retrieved winds, we proposed improvements to the volume velocity processing method by performing coordinate transformations and adding non‐linear constraints. The mean winds and air motions show annual/semiannual variations and are more variable near the equinoxes. Due to the small value of the vertical wind, we estimated it from the integration of the horizontal divergence and obtained a reasonable range of less than 1 m/s. The upwelling in the summer mesopause corresponds to the adiabatic cooling. Key Points: The first continuous observations of 3‐D spatially resolved winds and air motions in the Northern Hemisphere mid‐latitudes are reportedA newly developed volume velocity processing method including coordinate transformations and non‐linear constraints is introducedThe vertical wind is basically less than 1 m/s and is upward at the mesopause during summer, corresponding to the adiabatic cooling [ABSTRACT FROM AUTHOR]

Previous theoretical simulations showed the generation of double‐layer structures of E‐region field‐aligned irregularities (FAIs). In this study, we report the double‐layer structures of E‐region FAIs observed by an all‐sky radar at low latitude Ledong (18.4°N, 109°E), China. These FAIs appeared at the altitudes ∼90 and 110 km respectively. Both layers displayed quasi‐periodic patterns with synchronized spatial features, that is, being manifested as spatially separated patches or wavelike structures over similar longitudes at the two layers simultaneously. The neutral wind observations revealed the existence of wind shears at two separated altitudes where the double FAI layers occurred. The two wind shears created two vertically separated sporadic E layers and possibly drove the generation of the double‐layer FAIs via gradient drift instability. The synchronized spatial features of the FAIs at the two layers could be modulated by gravity waves. Plain Language Summary: The E‐region field‐aligned irregularities (FAIs) were observed usually in a form of single layer. Due to the limited field of view of narrow‐beam radars which were traditionally employed for observing ionospheric irregularity, the spatial morphology and evolution of E‐region FAIs in a small region were resolved. Owing to the recently developed capability of all‐sky radars in observing E‐region irregularities, the spatial features of E‐region irregularities over a larger zonal region up to hundreds of kilometers in the horizontal plane can be derived. Further, the spatial features of E‐region irregularities in the vertical direction can be unambiguously determined. Utilizing an all‐sky radar at low latitude Ledong, China, a case of double‐layer structures of E‐region FAIs, which occurred at ∼90 and 110 km altitudes respectively, was observed. The double layers of FAIs spanned a zonal coverage ∼250 km, showing as synchronized spatially separated quasi‐periodic patches or wavelike structures in two layers. Especially, the wavelike structures synchronized in the two layers could provide solid evidence for the crucial role of gravity waves in modulating E‐region irregularities. In combination with the collocated ionosonde Es and neutral wind observations, the physical mechanisms responsible for the generation of the double‐layer E‐region FAIs were discussed. Key Points: Double layer structures of E‐region field‐aligned irregularity (FAI) were observed at low latitude by an all‐sky radarBoth layers of FAIs were quasi‐periodic type and synchronously manifested as spatially separated patches or wavelike structuresThe double‐layer FAIs were likely generated by wind shear driven gradient drift instability and modulated by gravity waves [ABSTRACT FROM AUTHOR]

The complexity of ice particles in the atmosphere makes it difficult to model microphysical growth processes accurately. In this study, we simulated a snowfall case over Northern China Plain using two different microphysics schemes, that is, Thompson and Morrison schemes, in the Advanced Research WRF (Weather Research and Forecasting) model. Both schemes are able to reproduce the event, albeit with a slightly weaker precipitation compared with the surface observation. However, the radar reflectivity factor in Morrison simulation is higher than the radar observation to ∼10 dBZ. Further analysis reveals that such stronger radar reflectivity in the Morrison simulation might be caused by larger collection efficiency, which would lead to more active self‐aggregation process in prediction of snow number concentration and then larger snow particle size. Sensitivity tests show that using an alternative formula of collection efficiency produces smaller radar reflectivity that is in better agreement with observations. This study highlights the accurate representation of self‐aggregation process and underscores the needs of further improvement of ice microphysics schemes for the better snowfall simulations. Plain Language Summary: Understanding how snow forms in the atmosphere is complicated. We did a case study using two different microphysics schemes in numerical weather model to simulate a snowfall event over Northern China. Both schemes did a pretty good job in simulating the snowfall, but one of them, the Morrison scheme, showed much larger radar signal compared to what was really happening. We do further analysis to find out why this was the case. It turned out that the Morrison scheme simulated the snowflakes stick together more than they actually do in nature. This made the size of snowflakes in the simulation much larger. We ran more tests by changing the way the Morrison scheme making snowflakes stick together. When we did this, the simulation results showed more accurate radar reflectivity factor. So, what did we learn? How the snowflakes stick together is a big deal. If we get it wrong, the models will give us the unreasonable estimation of radar signal. This study helps remind scientists that they need to be very careful when they use these microphysics schemes. Key Points: Radar reflectivity factor from Morrison simulation exceeds 10 dBZ compared with observations, but Thompson scheme performs betterThe overestimation of radar reflectivity factor in Morrison simulation could be attributed to larger snow particlesLarger snow particles in Morrison simulation are caused by active self‐aggregation process of snow and higher collection efficiency [ABSTRACT FROM AUTHOR]

Understanding the diurnal variation of horizontal wind in the atmospheric boundary layer is important for weather and climate research and wind energy applications. Here we analyze the hourly data from 91 wind profiler radar sites in China and observe that the power spectral density of horizontal wind in lower troposphere approximately follows the −5/3 power law in the mesoscale range over the ocean and coastal areas. However, in inland areas, the slopes of the power spectra are significantly greater than −5/3. We characterize the temporal and spatial variations of maximum wind speed and low level jets and find that the thermal wind effect may partially contribute to the high percentage of low‐level jets observed in the southeastern coast of China and Hainan Island. While the ERA5 reanalysis reproduces wind spectrum well for time scales >1 day, its spectrum diverges significantly from that of profiler data at shorter time scales. Plain Language Summary: Understanding how the horizontal wind changes throughout the day in the lower part of the atmosphere is important for studying weather and climate and using wind energy. In this study, we looked at data from 91 radar sites in China that measure wind every hour. We found that the pattern of how the wind changes follows a specific mathematical relationship, called a power law, where the wind decreases in a particular way with decreasing spatial and temporal scales. This pattern holds true mostly over the ocean and coastal areas, but in areas further inland, the wind behaves a bit differently. We also studied how the low‐level jet (LLJ), which are fast winds at low altitudes, change over time and space. We discovered that the difference in temperature across the region contributes to the occurrence of these LLJs in coastal areas in southeast China and Hainan Island. Finally, we compare our findings with the ERA5 reanalysis, which demonstrates excellent agreement in reproducing the wind spectrum for time scales greater than 1 day. However, the spectrum derived from the ERA5 reanalysis diverges significantly from the profiler data at shorter time scales. Key Points: Wind spectrum density from wind profiler radars over China shows a less negative slope over inland sites than the −5/3 power law over oceanTemporal and spatial variation of maximum wind speed in the lower troposphere and low level jets are characterizedWind spectrum from ERA5 reanalysis is realistic (deficient) for time scales >1 day (<1 day) compared with profiler data [ABSTRACT FROM AUTHOR]

Mesoscale convective systems (MCSs) are crucial in modifying the water cycle and frequently induce high‐impact weather events over eastern China. Radar and Climate Prediction Center (CPC)‐4 km satellite‐derived infrared cloud top temperature (Tb) data were used to thoroughly analyze the long‐term climatology of MCSs over eastern China, particularly in the Yangtze–Huaihe River Basin (YHR) in the warm season from 2013 to 2018. For the first time, we contrasted the effects of data set selection and threshold setting on research outcomes. The large‐scale environments of MCSs initiation were also investigated using the latest global reanalysis data ERA5. It is found that striction of thresholds, including duration, reflectivity/Tb, area, and linearity, would lead to a greater proportion of early‐morning MCSs. Satellite‐identified MCSs differed from radar‐derived ones, exhibiting afternoon diurnal peaks, faster movement speeds, longer travel distances, and expansive impact areas. The center of MCS and related precipitation shifted northward from Pre‐Meiyu to Post‐Meiyu seasons, contributing to up to 20% of total rainfall, with most MCSs moving along eastward trajectories. MCSs typically had the most substantial impact in the Meiyu season because of the most prolonged duration, largest convective core area, and strongest precipitation intensity. Warm‐season MCSs initiated ahead of midlevel troughs and were related to strong anomalous low‐level convergence and midlevel upward. The circulation anomalies were the strongest in the Pre‐Meiyu season among the three subseasons, with most moisture sourced from the southwest. Plain Language Summary: This work used radar and satellite data to analyze the climate characteristics of a kind of large thunderstorms known as mesoscale convective systems (MCSs) in the Yangtze–Huaihe River Basin (YHR) in eastern China. These systems cover large areas, lasting from a few hours to a few days. The analysis revealed that stricter tracking thresholds would lead to more early‐morning MCSs. Satellite‐identified MCSs differed from those identified by radar. They tended to have more thunderstorms in the afternoon, move faster, travel longer distances, and cover larger areas. MCSs also contributed to up to 20% of the total warm‐season rainfall in the YHR. MCSs typically had the most substantial impact in the rainy season of eastern China from mid‐June to mid‐July. Warm‐season MCSs initiated ahead of low‐pressure systems and were related to strong anomalous low‐level convergence and midlevel upward motion. During the time before the rainy season, the large‐scale forcing needed to be anomaly enough to trigger MCS formation. Most of the moisture that caused MCSs came from southwest direction instead of stemming locally during this period. Key Points: Six‐year climatology of warm‐season mesoscale convective systems (MCSs) in Yangtze–Huaihe River Basin is investigated using satellite, radar data, and ERA5Criteria setting for tracking MCSs noticeably influences the derived featuresMeiyu season MCSs featured longest duration, largest areas, and heaviest precipitation, while the background circulation anomalies are the weakest [ABSTRACT FROM AUTHOR]

During 6–7 May 2017, a record‐breaking nocturnal rainfall event occurred in Guangzhou, China, and it was a typical warm‐sector heavy rainfall event under weak synoptic forcing. A prior observational study by the authors revealed that warm‐rain microphysical processes were dominant and responsible for the record‐breaking precipitation. In this study, the double‐moment Morrison, Thompson and NSSL microphysics schemes in WRF are evaluated against polarimetric radar observations in their ability of reproducing observed microphysical characteristics. The Thompson scheme shows the greatest fidelity to the observed raindrop size distribution (RSD) median value, corresponding to the most amount of precipitation forecast. While the Morrison and NSSL simulations overestimate (underestimate) the raindrop size (number concentration), exhibiting continental‐type convective precipitation. The three experiments slightly overestimate differential reflectivity (ZDR), but significantly underestimate specific differential phase (KDP) and liquid water content by about 30%–50%, implying the undervaluation of number of medium‐sized raindrops. Examinations of the occurrence frequencies of ZDR, KDP, mass‐weighted diameter, and logarithmic normalized intercept parameter for rain suggest that all three schemes fail to reproduce the full variability of observed RSD for the extreme rainfall. The vertical variations of RSD parameters and the Kumjian‐Ryzhkov parameter space suggest that the collision–coalescence is the dominant warm‐rain microphysical process but the simulated process is too weak. This may be attributed to the misrepresented RSD near the melting layer, where the raindrops with lower number concentration and larger sizes cannot grow through the collision–coalescence process as actively. Plain Language Summary: Extreme rainfall is of great concern due to its potential to cause major disasters. Cloud microphysics has been considered one of the main sources of uncertainty in predicting rainfall at cloud‐resolving resolutions. This study investigates the performances of three commonly used schemes representing cloud precipitation processes in an extreme rainfall case that occurred in the warm and moist environment of South China. The Thompson scheme is found to perform better in simulating raindrop sizes and surface precipitation. None of the three schemes reproduces the full variation of observed raindrops, and all of them underestimate raindrop size growth through collision processes. These results suggest areas needing improvement in microphysics schemes for predicting extreme precipitation in sub‐tropical regions. Key Points: Thompson scheme better reproduces raindrop median size and number concentration than two other schemes in a Guangzhou extreme rain eventNone of the three schemes examined adequately predicts the full variability of raindrop size distribution important for extreme rainfallLow raindrop concentration and excessively large sizes in simulations jointly cause the too weak collision–coalescence processes [ABSTRACT FROM AUTHOR]

We report for the first time a case of wavelike structures of E‐region irregularities observed by an all‐sky radar at Ledong (18.44°N, 108.97°E), China. The wavelike structures covered up to 250 km zonally, fluctuated in the vertical and horizontal planes, and were observed in the directions perpendicular and significantly off‐perpendicular to the geomagnetic field. The wavelength, and vertical and horizontal oscillating amplitudes were estimated at about 20–70, 5, and 2 km, respectively. Eventually, the large‐scale wavelike structure broke into spatially separated small‐scale patches and disappeared. The case provides observational evidence for the wave modulating sporadic E (Es) mechanism, which suggests that the wavelike structures of E‐region irregularity were primarily generated by wind shears and modulated by gravity waves. The wavelike structure was possibly an intermediate state between the continuous‐type and quasiperiodic‐type E‐region irregularities. The mechanism responsible for the echoing structure observed in off‐perpendicular directions is unclear. The possible contributions from refraction and reflection by intense Es layer/structure were discussed. Plain Language Summary: The E‐region irregularities were usually observed using narrow‐beam very high frequency radars. Due to the limited field‐of‐view (FOV) of the narrow‐beam radars, the spatial morphology of large‐scale irregularity structures could not be obtained. Over low latitudes, the E‐region irregularities were traditionally classified into two main types: the continuous type linked with the tidal sporadic E (Es) layer and the quasiperiodic (QP) type due to the drift of small irregularity patches. Facilitating from the very large FOV of the all‐sky radar at Ledong, we report a case of E‐region irregularities with different echo patterns from the continuous and the QP types. These E‐region irregularities showed wavelike structures covering up to 250 km in the zonal direction and were observed in directions both perpendicular and significantly off‐perpendicular to the geomagnetic field. In combination with the collocated Es and neutral wind measurements, the possible mechanisms responsible for the wavelike irregularity structures are discussed. Key Points: Wavelike structures of E‐region irregularities elongating up to 250 km are reported at low latitudes for the first timeThe wavelike structures were most likely generated by wind shears and modulated by gravity wavesThe wavelike structures may be an intermediate state between the continuous‐type and quasiperiodic‐type E‐region irregularities [ABSTRACT FROM AUTHOR]

This study analyzes microphysical signatures relevant to the short‐cycle lightning activity in the inner core of Typhoon Hato (2017) before landfall in China. Observations reveal that the lightning bursts were accompanied by enhanced inner‐core convection with a behavior cycle of about 3 hr. The coupling between wavenumber‐2 vortex Rossby waves (VRWs) and shear‐forced convective asymmetries resulted in a local updraft enhancement. Furthermore, supercooled liquid water droplets invigorated a striking enhancement of graupel via riming immediately above the freezing level, further enhancing charge separation and lightning generation outside the eyewall. Furthermore, when similar phase‐locking was associated with other propagating VRWs, graupel and updraft volumes were significantly boosted, leading to short‐cycle lightning outbreaks in the inner core. Plain Language Summary: Lightning behavior is one of the well‐defined indicators of convection within the Tropical cyclone (TC) circulation. Before the landfall of Typhoon Hato (2017), we found short‐cycle lightning outbreaks in the inner core of this typhoon. The interaction between the internal structures of the storm and changes in wind speed and direction with height could strikingly reinforce convection, thereby favorable for the short‐cycle electrification enhancement. This scenario is distinct from diurnal lightning bursts within TCs, which were found in previous studies. The diurnal lightning activity is thermodynamically governed by radiation, while vortex‐environment interactions in the inner core of Hato dynamically force the short‐cycle lightning outbreaks revealed here. Therefore, the findings presented in this case study suggest that interactions between the internal structures of a TC and the environment warrant an adequate focus in the short‐range forecasting of inner‐core convection in landfalling TCs. Key Points: Short‐cycle lightning outbreaks were found in the inner core of Typhoon Hato (2017)Interactions between vortex Rossby waves and the shear‐induced convective enhancement likely led to the quasi‐periodic lightning behaviorStrengthened updrafts and the significant growth of graupel enhanced the charge separation and lightning outbreaks [ABSTRACT FROM AUTHOR]

The microphysical characteristics, including the ice types and growth mechanisms, in two snowstorms over East China in 2016 (E16) and 2018 (E18) were explored using joint observations of a polarimetric radar and a disdrometer. In both events, the dendritic‐growth‐layer (DGL) signature (enhancements in differential reflectivity ZDR and specific differential phase KDP) was observed, indicative of the existence of horizontally‐oriented dendrites and plate‐like crystals. The KDP in the DGL, related to the total mass of ice particles, was used for snowfall nowcasting. According to the lagged correlation analysis, the reflectivity factor (ZH) near the ground, a proxy for snowfall intensity, could be well predicted by the KDP in the DGL with a 40‐min lead time and a correlation coefficient over 0.7 in E16. In contrast, E18 had a worse nowcasting performance, with the maximum correlation coefficient being ∼0.53, which could be attributed to its more complex ice microphysical structures and processes. The snow in E16 mainly grew from the deposition in the DGL (mainly dendrites and plates) and aggregation below. In comparison, the snowstorm was deeper in E18, and the less oblate crystals (with larger aspect ratios) from above the DGL could grow and mix with the dendrites and plates in the DGL, weakening the correlation between the KDP and ice mass. Below the DGL, snow growth in E18 was contributed by aggregation and more active riming according to both radar and disdrometer observations, which further lowered the nowcasting performance of snowfall by the KDP in the DGL. Plain Language Summary: Using cooperative radar and disdrometer observations, we found similarities and differences in the precipitation structures of two representative snowstorms on 21 January 2016 and 4 January 2018 in East China. Near the −15°C isotherm, oblate crystals like dendrites and plates grew in both storms, known as the dendritic growth layer (DGL). The radar measurements in the DGL were a good predictor for near‐surface snowfall in the snowstorm in 2016, with a lead time of 40 min. The particle sizes grew during falling below the DGL, through the clumping together of snow crystals in the process called aggregation. In contrast, in the 2018 case, the correlation between the radar measurements in the DGL and the near‐surface snowfall rates was lower than that in the 2016 case, which can be explained by the higher complexity of its precipitation structure. First, the ice crystals above the DGL can grow and mix with those within the DGL in this case. Meanwhile, in addition to aggregation, the ice particles can grow via collision with supercooled droplets (riming), which led to snow mass growth. These findings from the two snowstorms may be used as a sort of guidance for improving the snowstorm numerical modeling and nowcasting. Key Points: Different microphysical structures and processes in two snowstorms in East China with different snow terminal velocities at the groundDifferent snowfall nowcasting performances using specific differential phase in the dendritic growth layers that were found in both eventsNowcasting performance linked to the complexity of ice microphysical structures and processes [ABSTRACT FROM AUTHOR]

Vertical profiles of cloud microphysical properties importantly determine the lifetime and precipitation rate of clouds. The 94‐GHz cloud profiling radar (CPR) onboard the CloudSat satellite can measure the vertical profile of radar reflectivity, from which the microphysical properties of cloud can be retrieved. The retrievals bear variations due to various assumptions and auxiliary products used. This study targets on the mid‐latitude clouds in the northern hemisphere, and intercompares the CloudSat products describing the vertical profiles of cloud microphysics and evaluate the uncertainties for each retrieval algorithm, with further evaluation by aircraft in‐situ observations over the North China Plain region during 2013–2017. For those retrieval products performing phase apportion, the ambient temperature‐based linear apportioning on mixed‐phase clouds can produce reasonable estimation on ice water content, apart from the heavily precipitating clouds. The retrieved liquid water content constrained by cloud optical depth well matched in‐situ observations, however its effective size is overestimated (hereby underestimating the number concentration of water droplets) because of the influence of larger precipitating hydrometeors on size distribution. The CPR‐only retrieval can well produce the effective diameter and number concentration of ice for deep convection clouds, but using additional lidar constraint underestimates the effective diameter due to the intense attenuation by thick clouds. The analysis here suggests the appropriate parameters from various products for different cloud types, and provides guidance for future development of retrieval algorithms on vertical profiles of cloud microphysical properties. Plain Language Summary: Vertical profiles of cloud microphysical properties play an important role in the cloud lifetime and precipitation rate. The 94‐GHz cloud profiling radar (CPR) onboard the CloudSat satellite can retrieve the vertical profile of cloud microphysical properties based on measured radar reflectivity. However, the retrievals bear variations due to different assumptions and auxiliary products used. By comparing various CloudSat products and aircraft in‐situ measurements over the North China Plain, our results demonstrate that radar retrievals constrained by cloud optical depth can well produce liquid water content but overestimate its effective diameter. For the temperature‐based linear apportioning products, the mixed‐phase clouds can produce reasonable estimation on ice water content, apart from the heavily precipitating clouds. These indicate the appropriate cloud microphysical parameters under certain circumstances using different retrieval algorithms and measurement constraints should be specific for cloud types. Key Points: Vertical profiles of cloud microphysics from various CloudSat products and aircraft in‐situ observations are intercompared over the North China PlainRadar retrievals constrained by cloud optical depth can well produce liquid water content but overestimate its effective diameterAmbient temperature‐based linear apportioning on mixed‐phase clouds can produce reasonable estimates on ice water content apart from the heavily precipitating clouds [ABSTRACT FROM AUTHOR]

The performance of 4‐km Weather Research and Forecasting model in predicting reflectivity structure in China over three summer months is investigated using three‐dimensional (3D) reflectivity observations. Three verification domains, namely Southern China (SC), Central and Eastern China , and North China, that correspond to the three major rainfall centers of mainland China are selected. Results show that the forecasts reproduce the distribution and diurnal variation of precipitation well, but significant differences exist in the vertical distributions of the predicted and observed reflectivities. In observations, the highest frequency (of reflectivity ≥35 dBZ) occurs between 3 and 6 km, whereas it is at the surface in the forecast. The forecasts tend to over‐predict reflectivity intensity at the lower levels, especially in SC. Further evaluation using object‐based verification methods show that the forecasts greatly underestimate the afternoon peak frequency of precipitation clouds with reflectivity >30 dBZ. The forecasts fail to reproduce the diurnal variation of 35 dBZ mean and maximum height of the objects, producing less variation than observations. Analyses show that the failure in properly reproducing small‐scale reflectivity objects (with diameter <100 km) is primarily responsible for the underestimation of the mean and maximum object heights. Evaluation using additional 3D information show that the forecasts tend to produce a greater proportion of faster‐moving small‐scale objects. This study reveals that the simulation of the 3D structure of precipitation clouds in terms of reflectivity remains a great challenge, especially for smaller convective cells. Plain Language Summary: The simulation of precipitation clouds is associated carries the largest uncertainty in numerical weather prediction and climate models. With continued advancement in observations and numerical models, forecasts of horizontal distribution, intensity, diurnal variation and propagation of precipitation have been greatly improved. However, faithful representation of three‐dimensional (3D) cloud structure remains a great challenge, with the lack of systematic evaluations being one of the key causes. In this study, 3D gridded radar reflectivity observations are used to evaluate the precipitation clouds structure (with reflectivity ≥30 dBZ) predicted at a convection‐permitting‐resolution (CPR) over three summer months of 2016 in China. The evaluation reveals differences between the simulated and observed reflectivity structures, including the reflectivity intensity profile, the 35 dBZ mean and maximum height, the fraction of fast‐moving objects. CPR models still have difficulties in simulating 3D reflectivity structures especially for relatively small‐scale objects (with diameter <100 km). Key Points: Reflectivity structure predicted by the 4‐km Weather Research and Forecasting model are evaluated using 3D radar observationsThe model overpredicts the intensity of reflectivity at lower levels and fails to reproduce the diurnal variation of object heightThe failure to correctly reproduce the structure of smaller reflectivity objects is primarily responsible for the deviations [ABSTRACT FROM AUTHOR]

Finally, the convective windstorm identification process was determined when two adjacent stations near the convective system had a maximum wind gust reaching gale force. Based on the radar data of these convective -windstorm cases, convective cell recognition was conducted.[1] These studies will provide a reference for the automatic identification and early prediction of convective windstorms. (b) Monthly convective gale gust distribution in Hubei Province from 2010 to 2016. gl Sources and movement paths of convective windstorms Using the SWAN reflectivity mosaic product of the convective windstorms identification process, we noted 212 convective systems, whose sources and directions were clearly identifiable. [Extracted from the article]

Since early 2019, the Lunar Penetrating Radar (LPR) onboard Chang'e‐4 (CE‐4)'s Yutu‐2 rover has been gathering data relating to the subsurface structure of the Von Kármán crater within the South Pole‐Aitken Basin (SPA) on the lunar farside. Low‐frequency radar data have the potential of carrying geological information of about 300 m worth of strata below the traversed path. Forty‐two days' data have revealed a bifurcated structure within the layered structure beneath the CE‐4 surveying area for the first time, affecting the overlying reflectors between 90 and 310 m. This study suggests that, based on the morphological characteristics, thickness, depth (timing sequence) and direction of the newly found structure, its origin might be linked to the deposition of ejecta from the Schrödinger impact. The local stratigraphy is interpreted as consisting of distinct geological layers, corresponding to the superposition of ejecta from different impact craters, paleo‐regolith, and basaltic lava flows. Plain Language Summary: A radar (the Lunar Penetrating Radar, or LPR), built to look at the rocks below the surface, is presently traveling across an area of the lunar farside onboard a rover, called Yutu‐2 sent by China to shed some light on the striking difference between the Earth‐facing side of the Moon and its farside. So far, the radar has revealed layered structures interpreted as distinct volcanic flows, thus helping to unravel their history. The rover has been surveying the floor of the Von Kármán crater inside one of the oldest and largest impact structures of the Moon, the South Pole‐Aitken (SPA) Basin. By analyzing 42 lunar days of data, we found a new layer with a hunched upper surface and a relatively flat bottom inserted into a multilayered structure. Based on the morphology, thickness, depth, and direction of the new feature, we argue that its source could represent the ejecta deposition from one of the ancient lunar impact basins: Schrödinger. The subsurface structure revealed by the radar shows a complicated geologic history on the farside including multiple lava eruption events, the deposition of ejecta from different impact craters and weathering layers that develop during the quiescent stage. Key Points: The CH‐1 Lunar Penetrating Radar data of Chang'e‐4 reveals ∼300 m deep subsurface stratigraphy of the lunar farsideA unique bifurcated structure that resembles an ejecta discontinuity affects the overlying and underlying strataThe geologic evolution of the Von Kármán crater and the ejecta layer might be connected to the Schrödinger basin [ABSTRACT FROM AUTHOR]

MS of cells without convective windstorms reaching a maximum at 10kmh SP -1 sp , and that of the cells generating convective windstorms reached a maximum at 30kmh SP -1 sp . In general, the IMARC of cells generating convective windstorms was higher than those of cells without, that is, the radial convergence of the cells generating convective windstorms was stronger than those of cells without convective windstorms. However, distribution of ZMAX of the cells generating convective windstorms was higher than those of the cells without windstorms. The MRV of cells without convective windstorms was distributed around a value of 5ms SP -1 sp , and the MRV of the cells generating convective windstorms was mostly distributed from 5 to 15ms SP -1 sp (Figure 1j). [Extracted from the article]

This work compares the characteristics of the first echoes of thunderstorms and nonthunderstorms retrieved from S‐band polarimetric radar observations. Observations of 57 (39) isolated thunderstorm (nonthunderstorm) cells with roughly equivalent aerosol and water vapor conditions but different convective available potential energy were obtained with a S‐band polarimetric radar and three independent lightning location systems during 2016/2017 in southern China. Storms with the first echoes were divided into three types based on echo top heights, namely, type 1 (below 0°C layer), type 2 (0°C to −10°C), and type 3 (above −10°C layer). Our observations show median values of radar reflectivity (ZH) and differential reflectivity (ZDR) of type 1 and type 2 in warm phase layer (below 0°C layer) are obviously greater in nonthunderstorms than in thunderstorms, but this feature is not significant in type 3 storms. In the mixed 1 phase layer (0°C to −10°C), median ZH in type 2 is greater in nonthunderstorms while median ZDR in type 3 is slightly smaller. In the mixed 2 phase layer (−10°C to −38°C), median ZH is greater in thunderstorms while median ZDR is smaller, and ZDR values in nonthunderstorms are closer to zero. Although results of ZDR comparisons in the mixed phase are likely affected by random errors and/or residual bias errors, these different signatures suggest different characteristics of liquid or ice particles between thunderstorms and nonthunderstorms. This study is expected to advance our understanding of physical processes responsible for the generation of the first flash. Plain Language Summary: Thunderstorms generally show stronger convective activity than nonthunderstorms do. What are thunderstorms and nonthunderstorms like at the beginning of precipitation radar detection? Observations of 57 (39) isolated thunderstorm (nonthunderstorm) cells based on a S‐band polarimetric radar and three independent lightning location systems during 2016/2017 in southern China are investigated. We found that polarimetric radar parameters of the first echoes are different between thunderstorms and nonthunderstorms, especially, the larger echo intensity in nonthunderstorms below −10°C layer. Comparative results in different height layers suggest different characteristics of liquid/ice particles of the first echoes between thunderstorms and nonthunderstorms. This study would help us to understand the characteristics of microphysics in the formation of thunderstorms. Key Points: The first echoes of thunderstorms and nonthunderstorms determined using radar are manually retrievedThe parameters of polarimetric radar of the first echoes are different between thunderstorms and nonthunderstormsDifferent properties suggest different characteristics of liquid/ice particles of the first echoes between thunderstorms and nonthunderstorms [ABSTRACT FROM AUTHOR]

Southwest China is with complex topography including basins, mountains, hills and plains, where abrupt heavy rainfall events (AHREs) occur frequently and are difficult to quantitatively estimate due to limited ground‐based observations. Using the data of ground rain gauges and GPM dual‐frequency precipitation radar during April to September in 2014–2020, this study investigates vertical structures of AHREs over southwest China. Both mass‐weighted mean diameter (Dm) and reflectivity (Ze) of AHREs increase rapidly in ice‐phase process but slowly in liquid‐phase process. For convective rainfall of AHREs, abundant water vapour and strong atmospheric convective motion cause higher Dm and Ze but lower generalized intercept parameter (dBNw) than those for stratiform rainfall. Moreover, ice‐phase process is active while liquid‐phase process is weak in the mountains, but the situation is opposite in the plains, which results in large‐size and low‐concentration raindrops in the mountains while small‐size and high‐concentration raindrops in the plains. Furthermore, statistical models of vertical profile of reflectivity (VPR) indicate that VPR patterns are affected by surface rain intensity and present different trends around the 0°C level between stratiform and convective rainfalls. In addition, higher rain top height in the mountains is conducive to ice‐phase process while lower terrain height in the plains is favourable for liquid‐phase process. Therefore, the VPR pattern depends on rain type, terrain and rainfall intensity, and its fine model is beneficial for understanding microphysical process of AHREs and improving quantitative precipitation estimation by ground‐based radars. [ABSTRACT FROM AUTHOR]

In this study, multi‐source data, especially weather radar data, were used in the analysis of structural features and evolution of a squall line‐like rainband (SLLR) of a linear mesoscale convective system (MCS) in the eastern slope of the Taihang Mountains on 12 and 13 August 2018 and reached the following conclusions: (a) The SLLR, located in north of the linear MCS, exhibited a significant horizontal gradient of reflectivity and large vertical extension. The front‐to‐rear flow that appeared between the surface and the stratosphere was lifted upward immediately in front of a cold pool that formed rearward‐tilting updrafts. (b) As the SLLR passed over, surface meteorological quantities changed drastically, coinciding with the heavy precipitation. (c) The SLLR, when propagating northeastward, showed a complex convective development of sequential intensification, weakening, and re‐intensification within a 2.5‐hr period. The temporal intensification was related not only to the development of a low‐level rear‐inflow jet but also to the dynamic interaction between the vertical environmental wind shear and the cold pool. The lifted rear‐inflow jet, which formed over a vertically stacked horizontal vorticity couplet behind the leading edge, provides a reasonable explanation for the intensification of the SLLR, resulting in the reduction of the cold pool circulation and enhancement of the convective updraft. Topographic forcing might play a crucial role in the re‐intensification of the SLLR, which suggests the importance of the cold pool and topography in structural features and convective evolution of the squall line‐like rain bands. Key Points: The squall line‐like rainband (SLLR) in a linear mesoscale convective system exhibited the characteristics of the typical squall lineThe SLLR was associated with a complex convective development of sequential intensification, weakening, and re‐intensificationThe cold pool and topography play crucial roles in structural features and convective evolution of the SLLR [ABSTRACT FROM AUTHOR]

Mars Orbiter Subsurface Investigation Radar (MOSIR) is carried by China's first Mars probe, Tianwen‐1 orbiter, investigating the Martian subsurface stratification. Surface clutter from topography off‐nadir will overlap with the subsurface echoes, which affects the recognition of Martian subsurface reflections. Surface clutter simulation can effectively distinguish the nadir and off‐nadir radar echoes. In this paper, we choose the facet method to model the Mars surface topography and combine the roughness parameter with the radar backscatter function. We also provide an analytic expression of the echo phase considering the distance variation in the whole facet. The Chinese first Mars landing site is on Utopia Planitia, which is also one of the key investigating regions of MOSIR. Therefore, we also carried on surface clutter simulation of this region and generated simulation radargram with the Chirp Scaling algorithm. Furthermore, we use the contrast method to compensate for ionospheric error introduced by the NeMars Mars ionosphere model. Our surface clutter simulation program will significantly support MOSIR subsurface investigation, and provide a chance to verify the related data processing. Key Points: Wavelength‐scale surface roughness is introduced into the proposed surface clutter simulation methodThe proposed surface clutter simulation method is applied to verify the ionospheric error correction approachEcho peak power simulated by the proposed method is in good agreement with MRO SHARAD radargram [ABSTRACT FROM AUTHOR]

Led by the Institute of Geology and Geophysics, Chinese Academy of Sciences, we have built a brand‐new modular active digital phased array, with all solid‐state transmission and digital receiving incoherent scatter radar (ISR) in Sanya (18.3°N, 109.6°E), a station in low latitude China called Sanya ISR (SYISR) since 2015. The development of SYISR involved the indoor design and development of key components, an outdoor prototype test, and the production and debugging of the entire array. The unique features of SYISR include a single‐channel directly connected T/R unit and antenna, a radar array monitoring and calibration network, environmental adaptability design and open architecture. The entire radar has 4,096 channels and 5,930 modules in total. All the technical indices, mainly including a >2 MW peak power, a 43 dBi antenna gain and a <120 K noise temperature, either meet or are superior to the designed value through an independent evaluation. Waveforms of single pulse, linear frequency modulation, Barker code, long pulse and alternating code have been implemented to meet multiple purposes. Four observational modes for ionospheric experiments, including zenith stare, perpendicular to geomagnetic field, meridian scan, and all sky scan, have been developed. We have implemented time domain decoding, frequency domain decoding, and statistical inversion methods in calculating the autocorrelation function and power spectra in signal processing. The preliminary experimental results on ionospheric parameters, plasma lines, irregularities and hard targets are reasonable and encouraging, which greatly enhances our confidence in achieving our scientific goals in the future. Plain Language Summary: The Earth's ionosphere (∼60–1,000 km above the sea level) is composed of dense plasma, which shows complicated variations versus altitude, geographic location, and solar activity level. When a ground‐based radio wave is transmitted onto these plasmas, it will generate stimulated radiation, with a small portion of them radiating back to the ground. If this backscattered radiation is collected by a ground‐based radar, a variety of ionospheric parameters, including plasma density, temperature, and movement speed, can be derived through a complicated signal processing algorithm. An ionospheric monitoring method called incoherent scatter radar (ISR) was therefore developed. However, since this backscattered radiation is very weak, the ISR should be built with sufficiently large power (usually megawatts) and apertures (usually hundreds of square meters). This leads to the high cost of building an ISR, with only a few having been built in the world thus far. In this paper, we describe a newly built ISR, called Sanya ISR (SYISR), in low latitude China by applying modern radar technologies, such as modular active digital phased arrays, all solid‐state transmitting and digital receiving. The development of SYISR followed the principle of a gradual and orderly progress, including indoor design, outdoor prototype testing and the entire radar construction and debugging. The radar technical indices have been evaluated, and all meet the designed value. We also developed a signal processing algorithm and a variety of observational modes. Finally, preliminary experimental results are shown, which are reasonable and encouraging. In the future, we will gradually achieve our scientific goals via effective data accumulation and analysis. Key Points: Sanya incoherent scatter radar (SYISR) is a newly built incoherent scatter radar in low latitude China with modular active electronic scanning, digital phased array, solid‐state transmitting, and digital receivingThis paper details the hardware, key parameters, data processing and preliminary experimental results of SYISRThe key parameters meet or are superior to the original design, and the preliminary observations are encouraging [ABSTRACT FROM AUTHOR]

The Meteor and ionospheric Irregularity Observation System (MIOS), which consists of multi‐station optical subsystem at Ledong (18.4°N, 109°E) and Sanya (18.3°N, 109.6°E), and radar subsystem including a 38.9 MHz all‐sky interferometric radar and a 47.5 MHz coherent phased array radar at Ledong, has been in full operational since December 2021. This paper describes the system design and first results of meteor plasma density irregularities and corresponding meteoroids. The MIOS optical subsystem consists of a few tens of video cameras for observing optical meteor trail and spectrum. The MIOS phased array is composed of 135 Yagi antennas, arranged in sword‐like grid and grouped into 15 identical subarrays, with distances separated by 2–19.5 times the wavelength for unambiguous interferometry measurements. The phased array can form narrow and wide beams, with half power width of 8° and 24° in azimuth, respectively, allowing narrow‐beam pulse‐to‐pulse steering and wide‐beam multi‐baseline imaging observations in the east‐west direction. Observational results show that the MIOS is capable of unambiguously locating various meteor echoes, that is, head, specular and non‐specular echoes, revealing the structural evolution of field‐aligned and non‐field‐aligned irregularity, and of determining the properties of meteoroids producing/not producing irregularities. Cases of bright meteors producing non‐field‐aligned irregularities and not producing field‐aligned irregularities respectively are presented, and possible factors affecting the generation of meteor trail irregularities are discussed based on current understanding. It is expected that the MIOS will provide an important tool to study the generation and evolution of various meteor trail irregularities and the properties of the corresponding meteoroids. Plain Language Summary: Meteoroids entering the Earth's atmosphere significantly disturb the background ionosphere, producing ionized columns and plasma density irregularities, change the ionospheric composition, and even seed large‐scale ionospheric irregularity structures. However, due to the limitations of previous measurements, some physical processes, for example, how efficiently various meteoroids affect the background ionosphere, either producing or not producing some specific meteor trail irregularity phenomena, and the related meteoroid properties and origins, are less well understood. This calls for a facility to measure the properties of both the meteor trail and its corresponding meteoroid, and thus to reveal potential factors affecting the generation of meteor trail irregularities and the disturbance of the background ionosphere. Under the support of national natural science foundation of China, a Meteor and ionospheric Irregularity Observation System (MIOS) was designed to simultaneously capture the radar and optical signatures of meteors and plasma density irregularities. Here we report the initial measurements of the MIOS, which demonstrate its capabilities for observing various meteor and irregularity phenomena. Key Points: An optical and radar facility (MIOS) intended to study how meteoroids change the Earth's background ionosphere has been developedFirst observations of field‐ and non field‐aligned meteor irregularities and the corresponding meteoroids from the facility are presentedThe facility is expected to play an important role in the study of various meteors, their origin and possible processes affecting ionosphere [ABSTRACT FROM AUTHOR]

Utilizing the measurements and retrievals from the Global Precipitation Measurement dual‐frequency precipitation radar data during the summer of 2014–2020, this study analyzes the precipitation microphysics for summer rainfall over the Yangtze‐Huai River Valley (YHRV) region in China with respect to the precipitation efficiency index (PEI). The results show that the mean near‐surface rain rate and PEI for convective precipitation are generally larger than that for stratiform precipitation. There are larger raindrops in near‐surface rainfall for convective precipitation than that for stratiform precipitation. The High PEI precipitation is characterized by the larger ratio of convective precipitation samples compared to that for the other two categories of precipitation. The mean mass‐weighted mean diameter (Dm) of the near‐surface raindrops increase along with the precipitation top height (PTH) in Moderate PEI precipitation for convective and stratiform precipitating clouds. The larger PEI indicates the larger occurrence of the heavy raindrops and strong radar echoes near the ground. The growth process of raindrops falling below the melting layer in the High PEI precipitation is dominated by collision‐coalescence while the collisional break up is the dominant process below the melting layer in Low PEI precipitation. It is further verified that the microphysical characteristics and mechanisms of summer rainfall over the YHRV region are similar to that of precipitation derived from tropical cyclones over the ocean during the monsoon period. Key Points: The near‐surface raindrops increase along with the precipitation top height in the moderate precipitation efficiency index (PEI) precipitationThe higher PEI indicates the larger occurrence of near‐surface heavy raindrops and strong radar echoesThe microphysical mechanisms in the summer precipitation process are analyzed in terms of various PEI [ABSTRACT FROM AUTHOR]

The impact of assimilating China's operational X‐band Phased‐Array radar's (X‐PAR) data on the analysis and warning forecast of the vortex structure and intensity of the June 8, 2018 Foshan, Guangdong province, tornadic storm was investigated for the first time using an Ensemble Kalman Filter (EnKF) data assimilation system. Both radar radial velocity (Vr) and reflectivity (Z) from two S‐band operational radars and one X‐PAR were assimilated. Deterministic forecasts were launched every 6 min from 05:42 UTC (20 min before the tornado touched down) to 06:00 UTC from the EnKF mean analysis field. Five experiments were conducted to examine the added capability of Z assimilation of the EnKF system, and to investigate the impact of assimilating X‐PAR data on the analysis and prediction of the tornadic storm. Compared to the experiment without Z assimilation, the assimilation of Z reduced the analysis error and greatly reduced the forecast error of Z. The assimilation of X‐PAR data greatly improved the vortex structure of the tornadic storm at low levels, and improved the intensity of the rear inflow of the tornadic storm, especially with a higher assimilation frequency. Compared to the experiments without X‐PAR data assimilation, assimilating X‐PAR data improved the predictability of tornadic storm. Plain Language Summary: Tornadoes are difficult to predict worldwide. However, the scan speed of current operational S‐band (10 cm wavelength) radar is too slow to capture the evolution of tornadoes. The newly built X‐band (3 cm wavelength) Phase‐Array radar (X‐PAR) network in Guangdong Province, China, are hopeful to fill in the gap with their higher scan frequency and higher spatial resolution, which can capture the fine‐scale structure and rapid evolution of small scale systems such as tornadic storms. This study focuses on a case where a tornado embedded within the typhoon Ewiniar was well captured by the X‐PAR network. It demonstrated for the first time the use of X‐PAR data on the prediction of a tornadic storm in China. We used ensemble‐based data assimilation techniques named Ensemble Kalman Filter to utilize the information provided by the X‐PAR data. With the improved information, the analyzed tornadic storm vortex structure at low levels was greatly improved, especially with a higher assimilation frequency. Compared to the experiments without X‐PAR data, the experiment using X‐PAR data successfully predicted the tornadic vortex a few minutes in advance. Key Points: The impact of assimilating China's X‐band Phased‐Array radar (X‐PAR) radar data on the analysis and forecast of a tornadic storm was first investigated using an Ensemble Kalman Filter systemThe assimilation of X‐PAR data helps to produce a more realistic‐looking tornadic storm structure, especially at low levelsIncreasing assimilation frequency of X‐PAR data reduces the analysis error and subsequently improves the 8‐min tornadic storm forecast [ABSTRACT FROM AUTHOR]

Typhoon Lekima (2019) possessed a double‐eyewall structure before making landfall in eastern China, with its outer eyewall showing quasi‐periodic convective intensification. Several physical mechanisms that may cause eyewall convection asymmetries were examined. The upshear occurrence of the strongest convection could not be explained by either the typhoon's motion or the effect of descending inflow from outer rainbands. Radar reflectivity analysis showed that phase locking occurred between the wavenumber‐2 vortex Rossby waves (VRWs) propagating radially outward from the inner eyewall and the azimuthally propagating wavenumber‐1 VRWs on the inner edge of the outer eyewall. Additional phase locking further arose between the aforementioned wavenumber‐1 VRWs and the azimuthally propagating wavenumber‐2 VRWs on the outer edge of the outer eyewall. These two phase‐locking processes led to the pronounced quasi‐periodic intensification of the convective asymmetry in the western semicircle of Lekima's outer eyewall. Plain Language Summary: Tropical cyclone eyewalls are commonly accompanied by torrential rainfall that tends to cause flooding and devastation. In particular, precipitation prediction becomes more challenging when the eyewall convective activity exhibits a markedly asymmetric structure. This work focuses on the repeated occurrence of strong convection in the outer eyewall of Typhoon Lekima (2019) before it made landfall in China. The coastal ground‐based radar observations show that phase locking between waves associated with the double eyewalls serves as a plausible mechanism for the presence of the repeated strong precipitation in Lekima's outer eyewall. The findings in this study highlight the merit of coastal ground‐based radar observations in examining physical processes of tropical cyclone structure evolution, particularly in regions without aircraft reconnaissance. Key Points: Radar observations revealed quasi‐periodic intensification of convective asymmetries in the outer eyewall of Typhoon LekimaThe strongest convection in the outer eyewall occurred upshearPhase locking between vortex Rossby waves in the concentric eyewalls led to the occurrence of quasi‐periodic asymmetric convection [ABSTRACT FROM AUTHOR]

Monsoon coasts are characterized by active convection, but the features of associated convection initiation (CI) are not well understood. An analysis of kilometer‐resolution radar observations in South China reveals a distinct dependence of CI on monsoon activity, land‐sea contrast, and coastal orography. The CI occurrence becomes highly active after the monsoon onset and extends northward in summer. Several CI hotspots appear on tropical islands, peninsulas, and windward slopes of coastal mountains. Daytime CI occurrences are concentrated on land within 100 km of the coastline. The nocturnal CI maxima are located on coastlines and in the offshore areas with adjacent mountains. CI shows an offshore propagation after midnight prior to rainfall, probably due to the convergence of land breezes or downslope winds with diurnally enhanced onshore monsoon flows. The improved understanding of CI may provide additional benefit for forecasting severe weather because CI foretells the development of full‐fledged deep convection. Plain Language Summary: A large fraction of global rainfall occurs in the coastal areas of summer monsoon which are highly populated. Characterizing convective activity along monsoon coasts has been an important issue in regional/global climate and hydrological studies. For the first time, this study presents a long‐term radar climatology of convection initiation (CI) on the monsoon coasts of South China which have dense observation networks. The results show that CI becomes highly active after the summer monsoon onset. Most CI occurrences are concentrated within 100 km of the coastline, and the local maxima are strongly affected by topography and land‐sea contrast. The triggering of coastal convection also shows strong diurnal cycles with a daytime maximum on land and an offshore propagation after midnight. The findings provide key information to improve our understanding of how convective activity emerges in monsoon coastal areas. Key Points: We present the first long‐term climatology of convection initiation on the coasts where monsoon flows interact with local circulationsConvection initiation is highly active within 100 km of the coastline, with maxima near local mountains during onshore southwesterliesThe triggering of convection is dominant on land in the afternoon and off the coast after midnight, particularly in the monsoon season [ABSTRACT FROM AUTHOR]

This study examines the impacts of humidity adjustment in a cloud analysis system on the analysis and forecast of a squall line that occurred in southeast China on 23–24 April 2007. Radial velocity data are assimilated using the ARPS three‐dimensional variational system while reflectivity data are assimilated by a cloud analysis system. Experiments with two different humidity adjustment schemes are performed, with the original and enhanced versions. Another experiment does not adjust moisture. Both schemes generally decrease the humidity in front of the convective line and increase the humidity within the convective and stratiform regions of squall line compared to no humidity adjustment, and the original scheme produces the higher humidity within precipitation regions, especially the stratiform region. Both schemes improve the forecast of squall line structure, including the leading convective line, a transition zone, and a trailing stratiform region. Among the three experiments, the enhanced scheme produces the highest precipitation forecast skill. The latent heating rates are also diagnosed to investigate the microphysical responses to the humidity adjustment. The cooling outside of the observed precipitation regions corresponding to the humidity reduction also acts to suppress spurious precipitation. Water vapor condensation into cloud water and cloud water evaporation generally dominate the latent heating/cooling below the freezing level. Compared to the enhanced scheme, the original scheme releases much more latent heat in the middle troposphere, causing more warming. This is linked to the higher cloud water condensation rate, due to the higher amount of moisture addition/adjustment by the original scheme. Key Points: An enhanced vertical velocity‐dependent moisture adjustment scheme produces better squall line structures in both analysis and forecastThe "overwarming" issue associated with the original scheme is linked to more latent heat release associated with higher condensation rateCondensation into and evaporation of cloud water dominates latent heating/cooling below the freezing level [ABSTRACT FROM AUTHOR]

Dual‐frequency radar (DFR) could improve the accuracy of estimating the microphysical properties of rain profiles. Unfortunately, factors that cause inaccuracies in retrieved rain profiles include uncertainties in raindrop size distribution (DSD) parameterizations, DFR retrieval methods and radar measurement errors. The primary objective of this study was to assess the uncertainties in retrieving rain profiles to offer insight into application considerations for ground‐based DFRs in China. The uncertainties caused by DSD models are assessed by comparing attenuation coefficients and rain rates from DFR algorithms with those directly derived from DSD spectra from disdrometers. Then, based on a DSD model, the impacts of retrieval methods, radar range resolution, measurement error and errors in temperature on DFR retrievals are explored by comparing the rain profiles obtained using DFR algorithms with those directly output from the Weather Research and Forecasting model. Overall, the impact of measurement error on the DFR retrievals is relatively significant for both the forward retrieval method and the iterative backward retrieval method and should be eliminated in practical applications. At an individual uncertainty level, the impact of DSD parameterizations on the retrievals from the dual‐frequency technique is less than ±10% bias when the shape factor μ of the gamma distribution ranges from 2 to 4. The retrieved rain profiles from the forward retrieval method are relatively sensitive to radar range resolution and the retrieval performance can be improved with increasing the range resolution, while the iterative backward retrieval method exhibits stable retrieval performance. The impact of temperature errors on the retrieved rain profiles is negligible. [ABSTRACT FROM AUTHOR]

The Urumqi Institute of Desert Meteorology under the China Meteorological Administration (CMA) launched an observational experiment with a boundary layer wind-profiling radar in Urumqi City in February to March 2010. As described in this paper, wind profiles from the experiment were used to first compare with radiosonde data measured simultaneously to verify the confidence of wind-profiling radar data, which was used to analyse the wind field characteristics and other related issues in a snowstorm process that took place in Urumqi on 28 March 2010. Both wind direction and speed derived from wind-profiling radar data have good consistency with those from radiosonde data (wind velocity coefficient: 0.85; wind direction coefficient: 0.78). Before the snowstorm, a surface wind shear occurred. After outbreak of the event, the local weather was dominated by northwesterly and northerly winds at increasing velocities, while temperature was dropping and air pressure increased. Through in-depth analyses of the time-height profiles of the snowstorm process, it can be determined on a preliminary basis that the snowstorm was induced by a cold front system that entered the area around 2200-2300 LST on 27 March. A shear line that developed from a lower to a higher altitude represented both height and location of the frontal zone, and the cold front motion was broadly in a northeast-southwest direction. The wind direction in the process changed counterclockwise with height: this was mainly governed by cold advection, and baroclinic instability was established soon after the overpass of the cold front, eventually leading to the snowstorm. During the weather event, the equivalent reflectivity factor Ze was consistent with the onset and end of the snowstorm, the height at which rain (snow) particles were formed and snowfall intensity. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

1 A network of light-traps, an aerial net carried by kytoon (balloon) and two entomological radars were used to investigate whether ground beetles migrate nocturnally through China. The network-wide, simultaneous sudden increase in light trap catches, and after subsequent decrease, indicated a seasonal long-distance night migration of ground beetles, with Pseudoophonus griseus (Panzer) predominant, in August. 2 Aerial net trapping indicated that carabids were able to ascend to altitudes of at least 200 m and become windborne. Radar observations indicated that the migratory beetles formed high-density layer concentrations at approximately 200–300 m. 3 These concentrations were coincident with the top of the temperature inversion and a wind speed maximum, which suggested that the carabids tended to select warm, fast moving air for their long-distance migration. 4 The ground beetles orientated and displaced towards the downwind direction in southerly winds. Their air speed decreased as the tailwind increased and, thus, migrating beetles appeared to be conserving energy. 5 The mean ± SD displacement speed (ground speed) and air speed were 6.85 ± 1.73 m/s ( n= 172) and 4.45 ± 1.54 m/s ( n= 172), respectively. The duration of flight, estimated from the variation in area density derived from radar data, was approximately 9–10 h, indicating that the beetles might migrate hundreds of kilometres in a single flight. [ABSTRACT FROM AUTHOR]

The vertical characteristics of raindrop size distributions (DSD) and Z‐R relationships for monsoon frontal rainfall have been investigated using the co‐located two‐dimensional video disdrometer and micro rain radar at the Xianning surface site, and the S‐band weather radar at the Wuhan radar site during the Integrative Monsoon Frontal Rainfall Experiment (IMFRE). In this study, a total of 1,896 rain samples (1‐min resolution) were collected and classified into three categories of convective rain (CR), stratiform rain (SR), and light rain (LR), and their corresponding rain microphysical properties were explored. The LR category is dominated by the evaporation of smaller raindrops and the break‐up processes of larger raindrops, resulting in decreasing trends in radar reflectivity and rain rate as the raindrops fall. The SR category undergoes a competition of break‐up and coalescence processes, with weak increases in radar reflectivity and rain rate. Whereas, for the CR category, the coalescence process is dominant on the falling path of raindrops, especially below 1 km, leading to sharp increases in radar reflectivity and rain rate. The microrain radar data at height of 200 m is quantitatively compared with the two‐dimensional video disdrometer data, and a good agreement is found between them. Further, the number concentrations of raindrops are negatively correlated with the diameters of raindrops and discrepant significantly at different heights among the three rain categories. The height‐dependent Z‐R relationships found for LR, SR, and CR categories will provide insightful information for improving radar rainfall estimate of monsoon frontal rainfall over central China in the future. Key Points: The vertical distributions of rain parameters and Z‐R relationships during 2018 monsoon season over central China were investigatedDifferent formation processes of raindrops for classified light rain, stratiform rain, and convective rain were revealedThe MRR retrieved rain parameters were validated using surface 2DVD measurements [ABSTRACT FROM AUTHOR]