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Cloud‐related latent heat is critical to the development and maintenance of atmospheric circulation. However, it is unclear how sensitive the key large‐scale weather systems of an extreme rainfall event could be to the variation in cloud‐related latent heat. In a companion study, by investigating the indirect effects of different microphysics schemes, we hypothesized that the latent heat of condensation (CT) would play a role in the ability to simulate the extreme rainfall event that took place in Henan Province, central China, on July 19–21, 2021. To examine the proposed hypothesis, the impacts of varying the CT and the collection of cloud water by rainwater (ACW) in the Thompson, WDM6, and Morrison microphysics schemes on the simulation of the southerly flow and its indirect effect on this extreme rainfall case were studied using the Advanced Research Weather Research and Forecasting (ARW‐WRF) model. It was found that directly changing the CT and ACW had significant effects on the southerly flow and precipitation. An increase in CT generally led to a reduced temperature gradient, a smaller pressure gradient, a stronger southerly flow, and a precipitation surge of 32%–50%. Similar outcomes resulted from increasing ACW in the WDM6 scheme, which effectively diminished the cloud mixing ratio, generated higher CT, and consequently intensified the southerly flow and precipitation by 31%. This study confirmed that the accurate simulation of microphysical processes, along with latent heating, is desirable for more realistically reproducing the key weather systems in the simulation of extreme rainfall. [ABSTRACT FROM AUTHOR]

Previous numerical studies have focused on the combined effect of momentum and scalar eddy diffusivity on the intensity and structure of tropical cyclones. The separate impact of eddy diffusivity estimated by planetary boundary layer (PBL) parameterization on the tropical cyclones has not yet been systematically examined. We have examined the impacts of eddy diffusion of moisture on idealized tropical cyclones using the Advanced Research Weather Research and Forecasting model with the Yonsei University PBL scheme. Our results show nonlinear effects of moisture eddy diffusivity on the simulation of idealized tropical cyclones. Increasing the eddy diffusion of moisture increases the moisture content of the PBL, with three different effects on tropical cyclones: (1) an decrease in the depth of the PBL; (2) an increase in convection in the inner rain band and eyewall; and (3) drying of the lowest region of the PBL and then increasing the surface latent heat flux. These three processes have different effects on the intensity and structure of the tropical cyclone through various physical mechanisms. The increased surface latent heat flux is mainly responsible for the decrease in pressure. Results show that moisture eddy diffusivity has clear effects on the pressure in tropical cyclones, but contributes little to the intensity of wind. This largely influences the wind-pressure relationship, which is crucial in tropical cyclones simulation. These results improve our understanding of moisture eddy diffusivity in the PBL and its influence on tropical cyclones, and provides guidance for interpreting the variation of moisture in the PBL for tropical cyclone simulations. [ABSTRACT FROM AUTHOR]

Although realistic representation of the convective boundary layer (CBL) in the desert region in Northwest China is important for weather forecasts and climate simulations, evaluations of the performance of various planetary boundary layer (PBL) schemes in simulating the CBL in the region are rare. In this study, the performance of a scale-aware PBL scheme newly implemented into the Weather Research and Forecasting (WRF) model in simulating the CBL in the Taklimakan desert is evaluated based on a comparison with both the WRF-LES simulations and observations, with the focus on scale dependencies of the simulations compared to the conventional PBL scheme. A series of simulations are performed with a scale-aware PBL scheme (Shin-Hong) and the conventional PBL scheme (YSU) for a deep CBL observed at Tazhong station in the central Taklimakan on 1 July 2016. The CBL was over 5000 m deep with wider and deeper rolls than in a shallow boundary layer. The results showed that the vertical structure simulated with the Shin-Hong scheme was closer to that in both the WRF-LES (large-eddy-simulation) and observations than that simulated with the YSU. The simulation with the scale-aware scheme reproduced cellular rolls similar to those in the WRF-LES, while the conventional PBL scheme struggled to trigger intense convective cells rather than cellular rolls. The results strongly suggest that the scale-aware nonlocal PBL scheme can be used to adequately reproduce the scale and evolution of the observed rolls in the deep CBL in Taklimakan desert at subkilometer resolutions. [ABSTRACT FROM AUTHOR]

Three to four tropical cyclones (TCs) by average usually impact Taiwan every year. This study, using the Developmental Tested Center (DTC) version of the Hurricane WRF (HWRF) model, examines the effects of Taiwan’s island surface heat fluxes on typhoon structure, intensity, track, and its rainfall over the island. The numerical simulation successfully reproduced the structure and intensity of super Typhoon Haitang. The model, especially, reproduced the looped path and landfall at nearly the right position. Sensitive experiments indicated that Taiwan’s surface heat fluxes have significant influence on the super Typhoon Haitang. Compared to sensible heat (SH) fluxes, latent heat (LH) is the dominant factor affecting the intensity and rainfall, but they showed opposite effects on intensity and rainfall. LH (SH) flux of Taiwan Island intensified (weakened) Typhoon Haitang’s intensity and structure by transferring more energy from (to) surface. However, only LH played a major role in the looped path before the landfall of the Typhoon Haitang. [ABSTRACT FROM AUTHOR]

The extreme rainfall on 21 July 2012 is the heaviest rainfall that has occurred in Beijing since 1961. Observations and WRF (Weather Research and Forecasting) model are used to study the effect of MCS (mesoscale convective system) and topography on the rainfall. In this high-impact event, a quasi-stationary MCS developed in a favorable moist environment. The numerical simulation successfully reproduced the amount, location, and time evolution of the rainfall despite 4–6 h delay. In particular, the model reproduced the repeat passage of convective cells at the leading convergence line region along Taihang Mountains and the trailing stratiform region, producing the rainfall at nearly the right position. Results indicate the important roles of mesolow and low-level jet in maintaining the conditional instability that lifted the moist air to trigger deep convection and the repeated initiation and movement of the line shaped convective cells that produced the rainfall. The sensitive experiment was then further carried out to examine the effect of topography on this heavy rainfall. The reduction in model elevation field significantly influenced the above mesoscale systems, which lead to convective cells becoming less organized, and the peak rainfall amount in Beijing decreased by roughly 50%. [ABSTRACT FROM AUTHOR]

When typhoon Danas (2013) was located at northeast of Taiwan during 6–8 October 2013, a torrential rainfall brought by typhoon Fitow (2013) occurred over the east of China. Observations show that the rainband of Fitow, which may be impacted by Danas, caused the rainfall over north of Zhejiang. The Advanced Research version of the Weather Research and Forecast (ARW-WRF) model was used to investigate the possible effects of typhoon Danas (2013) on this rainfall event. Results show that the model captured reasonably well the spatial distribution and evolution of the rainband of Fitow. The results of a sensitivity experiment removing Danas vortex, which is conducted to determine its impact on the extreme rainfall, show that extra moist associated with Danas plays an important role in the maintenance and enhancement of the north rainband of Fitow, which resulted in torrential rainfall over the north of Zhejiang. This study may explain the unusual amount of rainfall over the north of Zhejiang province caused by interaction between the rainband of typhoon Fitow and extra moisture brought by typhoon Danas. [ABSTRACT FROM AUTHOR]

Super Typhoon Hinnamnor (2022) was a rare and unique western North Pacific typhoon, and throughout its lifespan, it exhibited all of the major features that pose current challenges in typhoon research. Specifically, during different stages of its lifespan, it experienced a sudden change of track, underwent rapid intensification, interacted and merged with another vortex, expanded in size, underwent rapid weakening, produced a strong cold wake, exhibited eyewall replacement, and underwent extratropical transition. Therefore, a timely identification and review of these features of Hinnamnor (2022), as reported in this article, will help update and enrich the case sets for each of these scientific issues and provide a background for more in-depth mechanistic studies of typhoon track, intensity, and structural changes in the future. We also believe that Hinnamnor (2022) can serve as an excellent benchmark to quickly evaluate the overall performance of different numerical models in predicting typhoon's track, intensity, and structural changes. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) constitute one of the major types of meteorological disasters in China, causing extensive damage. Based on the latest quality‐controlled provincial‐level TC disaster losses data over China from 2001 to 2020, the spatiotemporal variation in TC disaster and its link with TC activity in the form of prevailing track, precipitation, and intensity were investigated. Results showed that the areas impacted by TCs expanded significantly in the past decade (2011–2020) compared with the previous decade (2001–2010) throughout China, while the direct economic losses resulting from TCs did not increase significantly. Regionally, TC disaster losses increased in Northeast China but decreased in Fujian province. Causal analysis indicated that the increased influential TC (ITC) frequency and TC precipitation together led to the increase in damage for northern China. Also, more westward ITCs resulted in the increase in TC disasters for southwestern China. For southeastern China, the reduction in TC disasters was related to the northward shift in the northwestward ITC track. Although TC disasters increase with exposure, they are heavily influenced by TC track, precipitation, and intensity. Our findings suggest that more attention should be paid to TC prediction and early warning in northern China, especially Northeast China, where TC disasters are growing but there is greater vulnerability and insufficient capacity for TC prevention and mitigation. Plain Language Summary: China is one of the most frequently affected countries by tropical cyclones (TCs) in the world, suffering huge losses in term of human life and property. The average number of influential TCs varies little from year to year, but TC disasters vary broadly. These TC disasters involve not only the features of TCs themselves, such as precipitation, winds, and storm surges, but also socioeconomic development, the capacity of disaster prevention and preparedness. Utilizing the latest data on TC disasters, this study's results reveal that TC disasters have been aggravated in low‐impact areas, such as Northeast China. Understanding these changes in the characteristics of TC disasters is essential for TC disaster mitigation and climate change adaptation. Key Points: Tropical cyclone (TC) impacted areas expanded significantly in the past decade (2011–2020) compared with the previous decade (2001–2010) throughout ChinaTC disasters increased in Northeast China, where there is greater vulnerability and insufficient capacity for TC prevention and mitigationTC disasters are heavily influenced by TC track, precipitation, and intensity [ABSTRACT FROM AUTHOR]

Extreme rainfall associated with landfalling tropical cyclones (ERLTC) can bring severe disaster losses. Revealing the typical characteristics and formation mechanisms of ERLTC has important scientific significance and potential application value. In this study, cloud microphysical properties of extreme and non-extreme rainfall in three landfalling TCs over China under the similar climatic backgrounds are comparatively investigated based on the cloud resolving simulations with a novel quantitative separating method of cold (warm) rain from the total precipitation. Results show that the warm (cold) rain may shape (modulate) the area (intensity) of TC precipitation. During the extreme precipitation period of the strongest TC Lekima (2019), the amount of cold rain accounts for >3/4 of the total precipitation, which plays a leading role in the precipitation rapid enhancement. With the increase of precipitation intensity, the proportion of cold (warm) rain to total precipitation tends to increase (decrease). The area near eyewall is commonly dominated by warm rain due to the weak radar echoes there. During the extreme precipitation process induced by Lekima (2019), the hydrometeor contents (mainly rain water and snow) increase rapidly and maintain for a long time. The processes of water vapor condensation, accretion of cloud water by rain water and melting of snow are the most active. In addition, the comparison with Hagupit (2020) and Yagi (2018) reveals that the processes of raindrop collecting graupel then melting, and the weak evaporation of raindrop make considerable contributions to the formation of extreme precipitation caused by Lekima (2019). • Different TCs with similar backgrounds, tracks and landfalling locations can cause particularly different precipitation. • Warm rain may shape the area of TC precipitation, while cold rain may modulate the intensity of strong precipitation. • For the same precipitation intensity, the proportion of cold rain is the highest in the strongest TC Lekima. • Weak raindrop evaporation makes considerable contributions to the extreme precipitation caused by TC Lekima. [ABSTRACT FROM AUTHOR]

Extreme rainfall induced by landfalling typhoon (ERLTC) can cause destructive natural disasters throughout China. Cloud properties in ERLTC are not yet well understood and parameterized, which limits the forecast accuracy of ERLTC to some extent. The 99th percentile intensity of daily rainfall associated with LTC is objectively defined as ERLTC and using the CloudSat tropical cyclone (CSTC) dataset from 2006 to 2018, cloud macro- and microphysical characteristics are statistically investigated. Results show that the proportion of single-layer (double-layered) clouds increases (decreases) significantly on the occurrence day of ERLTC. In the TC inner core region, the proportion of deep convective cloud at 2–10 km is the highest, reaching 50%. In the TC envelop region, deep convective cloud at the height of 3–8 km and cirrus at the height of 12–14 km account for the highest proportions. For the TC outer region, cirrus around 13 km has the highest proportion. During the ERLTC period, the ice-water content is mainly distributed in 5–18 km, and is mostly distributed in the TC inner core, followed by the envelop region. A large number of smaller ice particles are gathering in the upper troposphere at 13–18 km, while a small number of larger ones is gathering in the middle levels around 8–10 km. These results are useful for evaluating the ERLTC simulations and are expected to provide new forecasting factors for ERLTC in cloud macro- and microphysical perspectives. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the effect of convection over the Naqu region of the central Tibetan Plateau (TP) on rainstorms in the downstream areas of the Yangtze River Basin (YRB) accompanied by water vapor transport during August 15–19, 2014. The hourly maximum C-band frequency-modulated continuous-wave (C-FMCW) radar echo intensity at Naqu obtained from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III) was applied to represent local convective motion during this rainstorm process. Results based on hourly rain-gauge station data, National Centers for Environmental Prediction (NCEP) Final (FNL) Operational Global Analysis data, and Weather Research and Forecasting (WRF) simulations revealed that convection at Naqu was a strong signal over the TP. Convection over the Naqu region could impact rainstorms in the middle and lower reaches of the YRB via a three-dimensional water vapor flux vortex (WVFV) structure with high-level divergence and low-level convergence. The eastward propagation of the WVFV structure would enhance convection and thereby develop rainstorms downstream of the YRB. A FLEXible PARTicle (FLEXPART) dispersion model tracked the trajectory of air masses originating from the TP toward the middle–lower reaches of the YRB, which supported the robustness of the diagnostic results. Highlights • C-band radar echo intensity was employed to measure convection. • Convection over the Tibetan Plateau had an eastward propagation. • This convection was sustained and developed by moisture flux vortex. • The eastward movement of convection facilitated rainstorm over the Yangtze River. [ABSTRACT FROM AUTHOR]

Interannual variation of summer precipitation in East China, and frequency of rainstorms during the monsoon season from 1961 to 2010, are analyzed in this study. It is found that the two variables show opposite trends on a decadal time scale: frequency of rainstorms increases significantly after the 1990s, while summer precipitation in East China decreases during the same period. Analysis of the spatial distribution of summer rainstorm frequency from 1961 to 2010 indicates that it decreases from the southeast to the northwest at the east edge of the large-scale topography associated with the plateaus. Spatial distribution of rainstorms with daily rainfall greater than 50 mm is characterized by a 'high in the southeast and low in the northwest' pattern, similar to the staircase distribution of the topography. However, the spatial distribution of variation in both summer precipitation and frequency of extreme rainstorms under global warming differs significantly from the three-step staircase topography. It is shown that moisture characteristics of summer precipitation and extreme rainstorms during the monsoon season in East China, including moisture transport pathways, moist flow pattern, and spatial structure of the merging area of moist flows, differ significantly. Areas of frequent rainstorms include the Yangtze River Valley and South China. Column- integrated moisture transport and its spatial structure could be summarized as a 'merging' of three branches of intense moist flows from low and middle latitude oceans, and 'convergence' of column-integrated moisture fluxes. The merging area for moist flow associated with rainstorms in the high frequency region is located slightly to the south of the monsoonal precipitation or non-rainstorm precipitation, with significantly strong moisture convergence. In addition, the summer moist flow pattern in East China has a great influence on the frequency of extreme rainstorms. Moisture flux vectors in the region of frequent rainstorms correspond to vortical flow pattern. A comparison of moisture flux vectors associated with non-rainstorms and rainstorms indicates that the moist vortex associated with rainstorms is smaller in size and located to the south of the precipitation maximum, while the moist vortex associated with non-rainstorms is larger and located to the north. It is shown that column- integrated moist transport vortices and the structure of moist flux convergence have significant impacts on the north-south oscillation of frequent rainstorm areas in East China, which is synchronized with the maximum vorticity of moisture transport and the minimum of convergence on the decadal time scale. Synthesis of moisture transport pathways and related circulation impacts leads to a conceptual model of moisture flow associated with rainstorms. [ABSTRACT FROM AUTHOR]