Research

24 pages, 15016 KiB

Open AccessArticle

Spatiotemporal Characteristics of Tropical Cyclone Precipitation in Guangdong Province, China, from 1961 to 2020

by Jing Zheng, Siying Guo, Li Zhuo and Hongyu Wu

Atmosphere 2023, 14(9), 1367; https://doi.org/10.3390/atmos14091367 - 30 Aug 2023

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Tropical cyclones (TCs) are often accompanied by heavy precipitation, which may lead to natural disasters and a serious threat to life and property. However, they also provide indispensable water resources. Studying the temporal and spatial characteristics of TC precipitation is of great importance [...] Read more.

Tropical cyclones (TCs) are often accompanied by heavy precipitation, which may lead to natural disasters and a serious threat to life and property. However, they also provide indispensable water resources. Studying the temporal and spatial characteristics of TC precipitation is of great importance for TC precipitation forecasting, TC disaster mitigation, and water resource utilization. Guangdong is one of the most frequently and severely TC-affected provinces in China. Due to the different methods used to identify TC precipitation, the conclusions offered by the existing studies are often inconsistent. Moreover, their analyses of the spatiotemporal characteristics of TC precipitation in Guangdong are not sufficiently thorough. In this study, we first selected the historical TCs that affected Guangdong from 1961 to 2020, using an objective separation method for TC wind and rain, based on the observation data from 86 national meteorological stations in Guangdong Province. From these observations covering the past 60 years, the temporal and spatial variations in TC precipitation in Guangdong for four different periods, namely the first rainy season (FRS), the second rainy season (SRS), the non-rainy season (NRS), and over the whole year (WY), were then explored using statistical analysis and multiple cluster methods. The results show that TC frequencies in the four periods all showed a decreasing trend. TC precipitation also showed a decreasing trend in the SRS and NRS, as well as for the WY, but showed a slightly increasing trend in the FRS. Both TC frequency and TC precipitation showed an apparent inter-annual fluctuation and a quasi-periodic pattern. The spatial distribution of TC precipitation in the four periods all showed a decreasing trend from the coastal to the inland stations, but the western coastal areas had higher TC precipitation values than the eastern coastal areas for the SRS, NRS, and WY periods. The spatial variations of TC precipitation in Guangdong in the four periods of the last six decades were quite similar, exhibiting three primary spatial modes and six patterns. Among them, the spatial distribution of TC precipitation being less than normal across the whole province is the most common pattern. The 86 stations can be classified into six groups when using the spatial clustering method and into four groups when using the time-series clustering method. Stations with higher TC precipitation and large inter-annual fluctuations are often distributed in the coastal areas, while stations with less precipitation and small inter-annual fluctuations are distributed in inland areas. However, the primary areas that are affected by TCs may vary in the different periods. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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17 pages, 5725 KiB

Open AccessArticle

Comparing Quality Control Procedures Based on Minimum Covariance Determinant and One-Class Support Vector Machine Methods of Aircraft Meteorological Data Relay Data Assimilation in a Binary Typhoon Forecasting Case

by Jiajing Li, Yu Zhang, Siqi Chen, Duanzhou Shao, Jiazheng Hu, Junjie Feng, Qichang Tan, Deping Wu and Jiaqi Kang

Atmosphere 2023, 14(9), 1341; https://doi.org/10.3390/atmos14091341 - 25 Aug 2023

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Abstract

This study investigates the impact of assimilating Aircraft Meteorological Data Relay (AMDAR) observations on the prediction of two typhoons, Nesat and Haitang (2017), using the Gridpoint Statistical Interpolation (GSI) assimilation system and the Weather Research and Forecasting (WRF) model. Two quality control (QC) [...] Read more.

This study investigates the impact of assimilating Aircraft Meteorological Data Relay (AMDAR) observations on the prediction of two typhoons, Nesat and Haitang (2017), using the Gridpoint Statistical Interpolation (GSI) assimilation system and the Weather Research and Forecasting (WRF) model. Two quality control (QC) methods, Minimum Covariance Determinant (MCD) and one-class Support Vector Machine (OCSVM), were employed to perform QC on the AMDAR observations before data assimilation. The QC results indicated that both methods significantly reduced kurtosis, skewness, and discrepancies between the AMDAR data and the reanalysis data. The data distribution after applying the MCD-QC method exhibited a closer resemblance to a Gaussian distribution. Four numerical experiments were conducted to assess the impact of different AMDAR data qualities on typhoon forecasting, including a control experiment without data assimilation (EXP-CNTL), assimilating all AMDAR observations (EXP-RAW), assimilating observations after applying MCD-QC (EXP-MCD), and assimilating observations after applying OCSVM-QC (EXP-SVM). The results demonstrated that using AMDAR data in assimilation improved the track and intensity prediction of the typhoons. Furthermore, utilizing QC before assimilation enhanced the performance of track forecasting prediction, with EXP-MCD showing the best performance. As for intensity prediction, the three assimilation experiments exhibited varying strengths and weaknesses at different times, with EXP-MCD showing smaller intensity forecast errors on average. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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23 pages, 7323 KiB

Open AccessArticle

Spatiotemporal Distributions and Related Large-Scale Environmental Conditions of Extreme Rainfall from Tropical Cyclones with Different Tracks and Seasons in Guangxi, South China: A Comparative Climatological Study

by Yuexing Cai, Fengqin Zheng, Cai Yao, Qianqian Lu, Weijian Qin, Hui He and Cuiyin Huang

Atmosphere 2023, 14(8), 1277; https://doi.org/10.3390/atmos14081277 - 12 Aug 2023

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Abstract

This study investigates the main climatological features of extreme precipitation (TCER) induced by tropical cyclones (TCs) affecting Guangxi (GX), South China using multiple datasets and a 99th percentile threshold during 1981–2020, with an emphasis on the rainfall diversities of different high-impact TC groups [...] Read more.

This study investigates the main climatological features of extreme precipitation (TCER) induced by tropical cyclones (TCs) affecting Guangxi (GX), South China using multiple datasets and a 99th percentile threshold during 1981–2020, with an emphasis on the rainfall diversities of different high-impact TC groups and their associated mechanisms. Results show that there are large regional differences and a seasonal imbalance in the climatological features of TCER in GX. In summer (fall), TCs with TCER events primarily move northward or eastward (northwestward or westward), namely, S-NWTCs and S-ETCs (F-WTCs and F-NWTCs). The rainfall centers exhibit asymmetrical features with S-NWTCs and F-NWTCs located in the northeast quadrant, but S-ETCs and F-WTCs in the southwest and northeast quadrants, respectively. Comparisons of atmospheric circulations and environmental factors indicate that the intense rainfall of F-WTCs is mainly attributed to the trough–TC interaction, which is accompanied by stronger upper-level westerly jet and cold air intrusion, thus increasing baroclinic energy and uplifting for the strongest rainfall among these four groups. This interaction is absent for other groups due to a greater South Asian high and western North Pacific subtropical high. Instead, the increased rainfall in S-NWTCs and F-NWTCs can mainly be attributed to the stronger low-level southwesterly jet, which, in combination with low-level warm advection and convergence induced by land–sea friction, promotes the release of latent heat through moisture condensation. S-ETCs differ from S-NWTCs and F-NWTCs in that moisture convergence is weaker due to the much-weakened TC circulation. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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21 pages, 5764 KiB

Open AccessArticle

Reinforcing the Effect of Warm Ocean Anomalies in the South China Sea on the Extended Tropical-Depression-Induced Heavy Rainfall Event in Hainan Island

by Sai Hao, Li Chen, Xiaoyan Liu, Kewei Liu and Wei Peng

Atmosphere 2023, 14(7), 1137; https://doi.org/10.3390/atmos14071137 - 11 Jul 2023

Cited by 1 | Viewed by 666

Abstract

An unusually persistent and heavy rainfall event occurred in Hainan Island from 1 to 9 October 2010, in association with one extended tropical depression (TD) over the South China Sea (SCS). Based on rain-gauge precipitation, satellite altimetry, in situ Argo profile, air–sea enthalpy [...] Read more.

An unusually persistent and heavy rainfall event occurred in Hainan Island from 1 to 9 October 2010, in association with one extended tropical depression (TD) over the South China Sea (SCS). Based on rain-gauge precipitation, satellite altimetry, in situ Argo profile, air–sea enthalpy flux, and reanalysis data, this study investigates the impact of warm ocean anomalies in the SCS on the formation and intensification of the extended TD, and their reinforcing effect on TD-related heavy rainfall. The TD intensified and migrated northward to the vicinity of Hainan Island. A thicker-than-normal warm subsurface layer that was present beneath the positive sea surface temperature (SST) anomalies contained a sufficient upper-ocean heat content to effectively restrain the TD’s self-induced SST cooling effect, and available enthalpy fluxes were therefore sufficient to support the maintenance of the TD. The composite analyses confirm the reinforcing effect of warm oceanic anomalies in the central SCS off the south-central coast of Vietnam on heavy rainfall in Hainan Island, with the composite precipitation of “Warm eddy” cases being significantly larger in Hainan Island and northern Vietnam than that of the “Normal” cases, using reanalysis and remote sensing precipitation data over 29 years (1993–2021). Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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14 pages, 4621 KiB

Open AccessArticle

Attenuation Correction of the X-Band Dual-Polarization Phased Array Radar Based on Observed Raindrop Size Distribution Characteristics

by Jiabao Feng, Xiantong Liu, Feng Xia, Yu Zhang and Xiaona Rao

Atmosphere 2023, 14(6), 1022; https://doi.org/10.3390/atmos14061022 - 14 Jun 2023

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Abstract

X-band dual-polarization phased array radar (XPAR-D) possesses high resolution and plays a significant role in detecting meso- and micro-scale convective systems. However, the precipitation attenuation it endures necessitates an effective correction method. This study selected radar data from XPAR-D at the peak of [...] Read more.

X-band dual-polarization phased array radar (XPAR-D) possesses high resolution and plays a significant role in detecting meso- and micro-scale convective systems. However, the precipitation attenuation it endures necessitates an effective correction method. This study selected radar data from XPAR-D at the peak of Maofeng Mountain in Guangzhou during 16–17 May 2020 from three precipitation stages after quality control. Attenuation coefficients were calculated for different precipitation types through scattering simulations of raindrop size distribution (RSD) data. Next, an attenuation correction algorithm (MZ_H-K_DP method) was proposed for the radar reflectivity factor (Z_H) according to different raindrop types and compared to the Z_H-K_DP method currently in use. The results indicate that the attenuation amount of XPAR-D echoes depends on the attenuation path and echo intensity. When the attenuation path is shorter and the echo intensity is weaker, the amount of attenuation and correction is smaller. Difficulties arise when there are noticeable deviations, which are challenging to resolve using attenuation correction methods. Longer attenuation paths and stronger echoes highlight the advantages of the MZ_H-K_DP method, while the Z_H-K_DP method tends to overcorrect the bias. The MZ_H-K_DP method outperforms the Z_H-K_DP method for different precipitation types. The superior correction capability of the MZ_H-K_DP method provides a significant advantage in improving the performance of XPAR-D for the detection of extreme weather. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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17 pages, 49393 KiB

Open AccessArticle

An Improved S-Band Polarimetric Radar-Based QPE Algorithm for Typhoons over South China Using 2DVD Observations

by Zeyong Guo, Sheng Hu, Guangyu Zeng, Xingdeng Chen, Honghao Zhang, Feng Xia, Jiahui Zhuang, Min Chen and Yuwen Fan

Atmosphere 2023, 14(6), 935; https://doi.org/10.3390/atmos14060935 - 26 May 2023

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Abstract

Polarimetric radar data are an important tool for quantitative precipitation estimation (QPE), which is essential for monitoring and forecasting precipitation. Previous studies have shown that the drop size distribution (DSD) and polarimetric radar parameters of typhoon-induced precipitation differ significantly from those of other [...] Read more.

Polarimetric radar data are an important tool for quantitative precipitation estimation (QPE), which is essential for monitoring and forecasting precipitation. Previous studies have shown that the drop size distribution (DSD) and polarimetric radar parameters of typhoon-induced precipitation differ significantly from those of other types of rainfall. South China is a region that frequently experiences typhoons and heavy rainfall, which can cause serious disasters. Therefore, it is critical to develop a QPE algorithm that is suitable for typhoon precipitation over South China. In this study, we constructed four simple QPE estimators, R(Z_H), R(Z_H, Z_DR), R(K_DP) and R(K_DP, Z_DR) based on two-dimensional video disdrometer (2DVD) DSD observations of typhoon-induced precipitation over South China in 2017–2018. We analyzed the DSD characteristics and the estimation accuracy of these four QPE estimators in the reflectivity–differential reflectivity (Z_H–Z_DR) space, as well as the S-band polarimetric radar (S-POL) data of seven typhoon-induced precipitation events that affected South China in 2017–2019. We used these data to quantitatively determine the optimal ranges of the estimators and establish a typhoon precipitation QPE algorithm for typhoon-induced precipitation over South China (2DVD-Typhoon). The evaluation results showed that: (1) compared to R(Z_H) and R(K_DP), R(Z_H, Z_DR) and R(K_DP, Z_DR) had lower performance in estimating typhoon-induced rainfall after incorporating the polarimetric parameter Z_DR, as strong crosswind of the typhoon caused some bias in the raindrop-induced ZDR; (2) the 2DVD-Typhoon algorithm utilizes the respective advantages of the individual estimators to generate the best QPE results; (3) the QPE performance of 2DVD-Typhoon and the Colorado State University–Hydrometeor Identification Rainfall Optimization (CSU-HIDRO) is used as a comparison for hourly rainfall, cumulative rainfall and different rainfall intensity. The comparison shows that 2DVD-Typhoon gives a better normalized error (NE), root mean square error (RMSE) and correlation coefficient (CC), indicating its strength in rainfall estimation for typhoons over South China. The above results provide theoretical support for improving typhoon-induced rainfall monitoring and numerical weather forecasting models in South China. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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16 pages, 6332 KiB

Open AccessArticle

Formation Mechanisms of the “5·31” Record-Breaking Extreme Heavy Rainfall Process in South China in 2021

by Fangli Chen, Huiqi Li, Sheng Hu, Shuai Jiang, Jiaojiao Li and Ruoting Wu

Atmosphere 2023, 14(5), 872; https://doi.org/10.3390/atmos14050872 - 16 May 2023

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Abstract

Based on the fifth-generation European Center for Medium-Range Weather Forecasts reanalysis data (ERA5), the real-time observation data from weather stations, and the radar products in Guangdong Province, we analyze the precipitation properties and formation mechanisms of the “5·31” extreme heavy rainfall process with [...] Read more.

Based on the fifth-generation European Center for Medium-Range Weather Forecasts reanalysis data (ERA5), the real-time observation data from weather stations, and the radar products in Guangdong Province, we analyze the precipitation properties and formation mechanisms of the “5·31” extreme heavy rainfall process with record-breaking 3-h accumulated rainfall in South China during 2021. The results show that the extreme heavy rainfall process is caused by the joint actions of weather systems such as a weak upper-level short-wave trough, a surface stationary front, and a low-level southwesterly jet. Before the heavy precipitation process, there is large precipitable water content and deep warm clouds, which provides a potential for the occurrence and development of the heavy rainfall process in Longhua Town of Longmen County and its surrounding areas. Simultaneously, the low-level southwesterly jet provides abundant warm-wet water vapor for the heavy rainfall area. The vertical atmospheric environmental conditions, such as strong horizontal temperature gradient, high convective available potential energy, high-temperature difference between 850 hPa and 500 hPa, and low convective inhibition, maintain for a long duration in the heavy rainfall area, which are favorable for the occurrence and development of high-efficiency convective precipitation caused by water vapor condensation due to the uplift of low-level warm-wet airflows. The combined effects of the enhanced low-level southwesterly airflow, the stationary front, the mesoscale surface convergence line generated by cold pool outflows, the terrain influence, and the train effect of the precipitation echoes make heavy precipitation near Longhua last longer and stronger than other areas, leading to the extreme heavy rainfall with the record-breaking 3-h accumulated rainfall in Longhua. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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22 pages, 9581 KiB

Open AccessArticle

Hourly and Sub-Hourly Rainfall under Synoptic Patterns during the Anomalous Meiyu Season 2020

by Liye Li and Fan Zhang

Atmosphere 2023, 14(4), 727; https://doi.org/10.3390/atmos14040727 - 18 Apr 2023

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Abstract

The 2020 Meiyu season has received extensive attention due to its record-breaking rainfall in the Yangtze–River Huai Basin (YHRB) region of China. Although its rainfall features have been well studied on various time scales, the sub-hourly/hourly rainfall features are unknown. In this study, [...] Read more.

The 2020 Meiyu season has received extensive attention due to its record-breaking rainfall in the Yangtze–River Huai Basin (YHRB) region of China. Although its rainfall features have been well studied on various time scales, the sub-hourly/hourly rainfall features are unknown. In this study, a wavelet analysis was applied to 1 min rainfall data from 480 national rain gauges across the YHRB, and hourly synoptic patterns during the Meiyu season were grouped using an obliquely rotated principal component analysis in T-mode (PCT). The results suggest that variances on the sub-hourly and hourly scales contributed 63.4% of the 2020 Meiyu rainfall. The hourly synoptic variations in the Meiyu season can be categorized into three major patterns: weak synoptic forcing (P1), a convergence line (P2), and a vortex (P3). The rainfalls under P1 were spatially dispersed over the YHRB and on the shortest time scale, with a 70.4% variance from sub-hourly to hourly rainfalls. P2 had a peak wavelet variance around 30 min–1 h, with rainfalls concentrated to the south of the convergent line. The rainfalls under P3 were locally distributed with a longer duration of around 1–4 h. Compared with the climate mean, hourly rainfall frequencies are indispensable to understanding the 2020 accumulated Meiyu rainfall anomaly. This research highlights the dominant role of synoptic patterns on the temporal and spatial features of the Meiyu rainfall. Full article

(This article belongs to the Special Issue Monsoon and Typhoon Precipitation in Asia: Observation and Prediction)

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