Fengjiao Chen

Shear‐relative, quadrant‐scale differences in precipitation microphysics between intensifying tropical cyclones (ITCs) and weakening tropical cyclones (WTCs) are investigated using Ku/Ka‐band observations from the Global Precipitation Measurement (GPM) Dual‐frequency Precipitation Radar (DPR) over the western North Pacific during 2014–2024. The results indicate that ITCs exhibit a higher fraction of convective pixels and statistically significantly larger near‐surface drop sizes compared with WTCs, despite their weaker instantaneous storm intensities. Notably, the downshear right (DR) quadrant of ITCs acts as a convective initiation zone, exhibiting the highest convective fraction yet the lowest mean storm echo top height, with microphysical signatures of more active drop breakup. In contrast, the downshear left (DL) quadrant emerges as particularly critical for intensification, showing the greatest enhancement in precipitation properties, especially in rain rate and storm echo top height, while the corresponding enhancement for WTCs is comparatively subdued. Additionally, the presence of significantly greater Z _e and larger drop sizes observed above the melting layer in the DL quadrant of ITCs indicates vigorous ice‐phase processes (e.g., riming and aggregation), while in WTCs, rapid Z _e increases are confined to a shallow layer, consistent with weaker updrafts that limit vertical ice growth. These results suggest that monitoring storm echo top heights and drop‐size evolution, particularly within the DR and DL quadrants, likely provide valuable insight towards early‐warning indicators of TC intensification and offer observational constraints for improving TC intensity forecasting.

Understanding the macro and micro characteristics of precipitation in landfall typhoons is crucial to predicting the path and intensity of tropical cyclones by using numerical models. In this study, we use observations from the Global Precipitation Measurement Mission to analyze the microphysics of convection and stratiform precipitation during the landfall of Typhoon Lekima. The statistical results show that the correlation coefficient of the reflectivity factors of the spaceborne and ground-based radars is 0.77 and that the water content detected by the 18.7 GHz low-frequency vertical channel is positively correlated with the intense-precipitation rate. The storm top height is generally consistent with the location of heavy precipitation. The average near-surface precipitation rate and liquid water content of convective precipitation are higher than those of stratiform precipitation. The average mass-weighted raindrop diameter and particle number concentration of convective (stratiform) precipitation at a distance of 2 km above ground level are 1.52 mm (1.29 mm) and 39.52 (36.44, in decibel scale), respectively. Below the melting layer, there is a significant increase in average particle diameter, indicating that the collision aggregation growth process of raindrops is dominant. These results are potentially helpful in validating and improving microphysics parameterization in numerical models.

In order to study the detection performance of the Advanced Direction Time Lightning Detection System (ADTD) over mainland China, the relationship between the detection efficiency (DE) and distance for ADTD sensor is analyzed using lightning location data by ADTD during 2014–2020, which fits well with the probability density function of the Gamma distribution. The DE and location accuracy of ADTD across China are hereafter evaluated according to the constructed probability density function. The results show that the DE of a single sensor first increases rapidly and then decreases slowly with the increase of the detection distance, and the model constructed based on the probability density function of Gamma distribution can explain this relationship well. In the regions with dense sensors such as central and eastern China, the DE of ADTD can reach 95%, with the majority of regions having lower location errors (less than 1,000 m). While, in the areas where sensors are sparse such as the Qinghai-Tibet Plateau and at the edge of ADTD, the DE of ADTD is less than 90% (in some areas it is even lower than 50%), and the location error greater than 1,000 m. In general, ADTD can accurately detect cloud-to-ground lightning events in most areas of China, but its accuracy is limited in some areas due to sparse sensors and instrument parameter settings.

The northeastern China cold vortex (NCCV) is the main weather system affecting Northeast China. Based on the precipitation products from the dual-frequency precipitation radar (DPR) onboard the Global Precipitation Measurement core observatory (GPM) satellite, the precipitation structures and microphysical properties for different rain types in 6432 NCCVs from 2014 to 2019 were studied using dynamic composite analysis. Our results show that the precipitation in NCCVs is dominated by stratiform precipitation. Regions with high stratiform and convective precipitation frequency have a comma shape. The growth mechanism of precipitation particles changes at ~4 km in altitude, the lower particles grow through collision (more pronounced in convective precipitation), and the upper hydrometeors grow through the Bergeron process. Additionally, the precipitation structures and microphysical properties exhibit great regional variations in NCCVs. The rainfall for all rain types is the strongest in the southeast region within an NCCV, mainly characterized by higher near-surface droplet concentration, while precipitation events occur more frequently in the southeast region for all rain types. There are active rimming growth processes above the melting layer for convective precipitation in the western region of an NCCV. In the southeast region of an NCCV, the collision growth of droplets in both types of precipitation is the most obvious.

The statistical characteristics of precipitation microphysics in lightning clouds are not yet fully understood, as a result of the limitations of traditional observational methods. Using the latest observations from the dual-frequency radar and microwave imager onboard the Global Precipitation Mission (GPM) and ground-based lightning observations, the precipitation microphysics of precipitation features with and without lightning (LPFs and NLPFs) was investigated across four typical regions of China in summer during the time period of 2014–2021. The statistical results show that the LPFs are characterized by smaller concentration and larger mass-weighted mean diameter (D_m) for rain and ice hydrometeors than those of NLPFs. Below the melting layer, the radar reflectivity (Z_e) for both the LPFs and NLPFs generally decreases toward the surface, indicating the evaporation or strong break-up of rain hydrometeors. Above the melting layer, the Z_e values mainly increase as the altitudes decrease for both LPFs and NLPFs, indicating the rimming, aggregation, or deposition processes. However, the change in slope is much smaller for the LPFs than for the NLPFs, which suggests a more uniform distribution of large ice hydrometeors at high altitudes, probably as a result of the stronger updrafts within the LPFs. The microphysical structures of the LPFs show great regional differences among the four regions of China, which is characterized by the low concentration of large-sized rain hydrometeors over Northeast China, and a high concentration of small-sized rain hydrometeors near the surface over the Yangtze-Huaihe River basin.

Investigated in this study are the seasonal and semi‐diurnal variations of the cloud‐phase climatology over the southern Himalayas and adjacent regions by using 5 years of Himawari‐8 cloud‐product data (2016–2020). The four selected regions from south to north are the Gangetic Plains (I), Himalayan foothills (II), southern slope of the Himalayas (III), and the Himalayan–Tibetan Plateau region (IV), respectively. Results showed that the cloud frequency of cloud gradually increases from region I via II to III, then sharply decreases as the altitude increases up to IV. Ice‐phase clouds occurs more frequently over regions I/II (III/IV) during boreal summer (winter), while water‐phase cloud has a higher frequency over region III/IV (I/II) in summer (winter), respectively. All of the different cloud phases have a clear seasonal cycle. Furthermore, the semi‐diurnal variation shows that water‐phase clouds tends to have an occurrence frequency peak around noon (in the later afternoon) over regions I/II/III in summer (winter), whereas over region IV it only occurs more in the morning in both seasons. Ice‐phase cloud generally occurs more in the late afternoon in both boreal summer and winter, especially over region IV. Further analysis showed that the differences in the cloud‐phase characteristics over the southern Himalayas and adjacent regions are likely related to the interactions of the synoptic‐scale circulation, the topography, and the water vapor transport.

A knowledge of precipitation microphysics of tropical cyclones (TCs) is crucial for forecasts of the TC track and intensity using numerical weather models. Based on five years of measurements of TCs over the western North Pacific from the dual‐frequency precipitation radar and the microwave imager on board the Global Precipitation Measurement satellite, the precipitation characteristics and microphysical processes in different regions of TCs and their associations with ice scattering signals are investigated. In the region close to the TC center, the storm top height (STH) and near‐surface rain rate are high, and the hydrometeors have a high concentration and a relatively low mass‐weighted mean diameter (D_m). In the outer TC region, the distributions of the reflectivity factor (Z_e) and D_m become broader as the mean D_m increases. Z_e and D_m values generally increase below the melting layer, indicating the predominant role of collision–coalescence processes. The occurrence probability of collision–coalescence is greater than 90% when STH is less than 5 km and the polarization‐corrected temperature at 89 GHz is greater than 250 K. When the STH exceeds 5 km, the collision–coalescence process is also predominant in the eyewall region; however, the influence of the breakup process increases in the rainband regions.

Using observations from the dual‐frequency precipitation radar (DPR) onboard the Global Precipitation Measurement mission (GPM) satellite, this study analyzes the microphysical structures and processes of tropical cyclone (TC) precipitation over the western North Pacific in terms of different precipitation efficiency indices (PEIs). The statistical results show that the mean mass‐weighted mean diameter of raindrops (D_m) at 2 km is 1.67 mm (1.37 mm) for convective (stratiform) precipitating clouds. Precipitating clouds with high PEI have higher liquid water path than nonliquid water path for both convective and stratiform clouds. The mean D_m of convective and stratiform precipitation increases as the PEI increases. The vertical profiles of D_m and reflectivity (Z_e) for convective and stratiform precipitating clouds in TCs differ substantially as the PEI changes. Below the melting level, there is a clear decrease (increase) in D_m and Z_e toward the surface for clouds with low (high) PEI. In general, clouds within TCs producing the most efficient precipitation are characterized by strong coalescence, not only for small droplets but also for relatively large raindrops; in contrast, the breakup of hydrometeors is the dominant process in convective and stratiform precipitating clouds with low PEI. These results will help validate and improve the hydrometeor parameterization schemes in cloud and climate models.

Many studies have reported on the trends of precipitation in Mid-Eastern China (EC). However, the trends of convective and stratiform precipitation are still unknown. Here, we examine the trends of summer convective and stratiform precipitation in EC from 2002 to 2012 on the basis of the TRMM observations. Results revealed that the rain frequency (RF) for both convective and stratiform precipitation increased in majority regions of Southern EC (SEC), but decreased in Northwest part of Northern EC (NEC). The decreasing rate of RF for stratiform precipitation in NEC is twice as much as that for convective precipitation, while the increase of convective precipitation in SEC is more evident than stratiform precipitation. The rain rate (RR) exhibited a decreasing trend in most portions of EC for both convective and stratiform precipitation. In SEC, neither PW nor WVT has good ability in explaining the precipitation variability. However, in NEC, PW is closely correlated to convective RF and WVT is more closely related to stratiform RF.