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With the aim to examine variations in the migration phenology and population of N. lugens along with the advance/retreat of the Asian summer monsoon (ASM) and lay the foundation for further study on predicting the timing and location of N. lugens outbreak, correlation analysis and spatial analysis were applied for estimating the impact of the ASM and its related meteorological factors on the migration phenology and population of N. lugens in China in this paper. The ASM had a positive effect on the occurrence and outbreak of N. lugens. First, the first appearance date of N. lugens was consistent with seasonal advances of the northernmost location of the ASM, and the ASM provided the dynamic condition for the northward migration of N. lugens. Second, outbreak of N. lugens occurred in the area under the control of the ASM, and the ASM provided the survival condition for the population of N. lugens. Third, the population was positively related to the northernmost location of the ASM, θE (850hPa) and wind speed (850hPa). Particularly, the stronger southwest wind caused the date of the first, peak and last catches of N. lugens to turn up earlier than in the extremely years. [ABSTRACT FROM AUTHOR]

This study evaluated the forecast skill of CMA-GD 3 km and CMA-GD 1 km with hourly Rapid Update Cycle (RUC) for five monsoon precipitation events in South China from 2018 to 2020, using the fraction skill score (FSS) of the neighborhood spatial verification method. The results revealed that, among the 24-lead-hour forecasts in CMA-GD 3 km, the FSS for the 0.1 mm precipitation threshold increased linearly with the lead time from 3 to 1 hour, while there was no significant improvement in other lead times. For the 5 mm precipitation threshold, the forecast skill was highest for the latest 1-hour lead time, while the FSS showed slight variation between lead times of 24 hours and 8 hours. The FSS for 10 mm and 20 mm precipitation thresholds were similar to that of 5 mm, with the difference that the best score occurred at the 2-hour lead time. Among the 6-lead-hour forecasts in CMA-GD 1 km, the forecasts of the latest 1-hour lead time were the best choices for four precipitation thresholds. When comparing CMA-GD 3 km and CMA-GD 1 km, it was found that CMA-GD 3 km had better skill for forecasts of 0.1 mm and 5 mm precipitation at 2-hour and 1-hour lead times, while CMA-GD 1 km had better skill for all other forecasts, including the forecast of 20 mm precipitation nearly all lead hours (including 3- to 6-hour, and 1-hour lead times). The results suggest that the increased resolution of the model may be beneficial for precipitation forecasts in South China, especially for short-duration heavy precipitation over a longer lead hours. However, the limited sample size of this study calls for further evaluation using more cases to validate the results′ generality. [ABSTRACT FROM AUTHOR]

Temporal and spatial evolution characteristics of the 30-60 day oscillation (intraseasonal oscillation, ISO) of summer rainfall in China and the effects of East Asian monsoon on the rainfall ISO are analyzed in this paper. Results show that the annual and decadal variations of the oscillation exist between 1960 and 2008, and the intensity is weakest in the late 1970s and early 1980s. In the typical strong years of the rainfall ISO obtained from empirical orthogonal functions (EOF mode 1), an anticyclone is in northwestern Pacific and a cyclone is in the east of China. In the typical weak years, the wind ISO is much weaker. The low-frequency zonal wind and water vapor transport from the low latitudes to mid-latitudes in the typical strong years, and the oscillation strength of diabatic heating is much stronger than that in the weak years of the rainfall ISO. The anomaly characteristics of the rainfall ISO show anti-phases between the Yangtze River basin and south of China. As for the typical strong years of the rainfall ISO in the Yangtze River basin (EOF mode 2), the main oscillation center of water vapor is in the east of China (20-30°N, 110-130°E). In the peak (break) phase of the rainfall oscillation, a low-frequency cyclone (anticyclone) is in the Yangtze River basin and an anticyclone (cyclone) is near Taiwan Island. In addition, the peak rainfall corresponds to the heat source in the Yangtze River basin and the heat sink in the Qinghai-Tibet Plateau. As for the typical strong years of the rainfall ISO in the south of China, the main oscillation center of water vapor is south of 20°N. In the peak (break) phase of the rainfall ISO, a low-frequency cyclone (anticyclone) is in the south of China and an anticyclone (cyclone) is in the Philippines. The peak rainfall corresponds to the heat source in the south of China and the South China Sea, and the heat sink in the west of Indochina. [ABSTRACT FROM AUTHOR]

The Maritime Continent (MC) is an important region where the Tropical Pacific and the Indian Ocean interact with each other via "the atmospheric bridge" and a key region for the interaction between the Asian and Australian monsoons. Using the NCEP/NCAR and CMAP monthly mean reanalysis over the period of 1979-2012, the interdecadal variations of diabatic forcing over the key region of the Maritime Continent and its possible relations with the East Asian summer monsoon have been investigated in the present paper. Our results show that climate variations in the Maritime Continent is particularly significant in the area of95-145°E, l0°S-10°N, which is thus defined as the key area of the MC (i.e., KMC area). Without the input of latent heat release in the atmosphere, distinct interdecadal change of diabatic heating is found to exist from 1979 to 2012; it intensified before 1980s and peaked in the late 1980s and weakened after this period. By analyzing each individual component that contributes to the diabatic heating in the KMC area, surface latent heat flux and net long-wave radiation in the atmosphere are found to be the two dominant components. With negative diabatic heating anomalies over KMC, there will be more precipitation on islands and less precipitation over sea, and more rainfall around the equator, which is in correspondence with the convergence center around the equator in the KMC area . Along the meridional-vertical section averaged between 115-1 20°E, the well-defined vertical circulation anomalies are observed with the ascending branches over KMC and the area around 30°N respectively, and the descending branch over the South China Sea. Water vapor transports from the Bay of Bengal and South China Sea to eastern China to benefit the positive precipitation anomalies. The meridional-vertical circulation in East Asia plays a critical role in linking the interdecadal variability of diabatic heating over the KMC and East Asian summer monsoon anomalies. [ABSTRACT FROM AUTHOR]

While heavy rainfall frequently takes place in southern China during summer monsoon seasons, quantitative precipitation forecast skills are relatively poor. Therefore, detailed knowledge about the raindrop size distribution (DSD) is useful in improving the quantitative precipitation estimation and forecast. Based on the data during 2018-2022 from 86 stations in a ground-based optical disdrometer measurement network, the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution (N(D)), mass-weighted mean diameter (Dm) and other integral DSD parameters such as radar reflectivity (Z), rainfall rate (R) and liquid water content (LWC). In addition, the effects of geographical locations, weather systems (tropical cyclones, frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered. The results are shown as follows. 1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation, and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution. The relationships between the Z and R for stratiform and convective precipitation are also derived for the province, i.e., Z = 332.34 R1.32 and Z = 366.26 R1.42 which is distinctly different from that of the Next-generation Weather Radar (NEXRAD) Z-R relationship in United States. 2) In the rainy season (April-September), the Dm, R and LWC are larger than those in the dry season (October- March). Moreover the above parameters are larger, especially in mid-May, which is the onset of the South China Sea summer monsoon. 3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dm and a larger normalized intercept parameter (log10Nw), suggestive of maritime-like rainfall. Dm is larger and log10Nw is smaller in the inland area, suggestive of continental-like rainfall. 4) Affected by such weather systems as the tropical cyclone, frontal system and summer monsoon, the DSD shows characteristics with distinct differences. Furthermore, frontal system rainfall tends to present a continental-like rainfall, tropical cyclone rainfall tends to have a maritime-like rainfall, and summer monsoon rainfall characteristic are between maritime- and continental-like cluster (raindrop concentration and diameter are higher than continental cluster and maritime cluster, respectively. [ABSTRACT FROM AUTHOR]

The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3. The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM. The monsoon indexes for East Asian summer monsoon and land-sea thermal difference, which characterize the intensity of the EASM, show an obvious increase during the onset period of the EASM. Moreover, the land-sea thermal difference is more sensitive to warmer SST. Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China, South China Sea, and the Western Pacific Ocean to the east of the Philippines. While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China, precipitation increases notably in northern China, the South China Sea, the East China Sea, the Yellow Sea, and the Western Pacific to the east of the Philippines. North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent. The surface air temperature shows a warming trend. The warming in the entire troposphere between 30°N and 50°N increases the land-sea thermal contrast, which plays an important role in the enhancement of the EASM. Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension. [ABSTRACT FROM AUTHOR]

A heavy rainstorm named Beijing "7.21" heavy rainstorm hit Beijing on 21 to 22 July 2012, which is recorded as the most severe rainstorm since 1951. The daily precipitation amount in many stations in Beijing has broken the history record. Based on the NCAR/NCEP reanalysis data and precipitation observation the large-scale conditions which caused the "7.21" heavy rainstorm are investigated, with the emphasis on the relationship between it and an equatorial convergence zone, Asian summer monsoon as well as the tropical cyclone over the ocean from the Philippines to the South China Sea (SCS). The results indicated that a great deal of southerly warm and wet moisture carried by northward migrating Asian summer monsoon provided plenty of moisture supplying for the "7.21" heavy rainstorm. When the warm and wet moisture met with the strong cold temperature advection induced by cold troughs or vortexes, an obviously unstable stratification formed, thus leading to the occurrence of heavy precipitation. Without this kind of intense moisture transport, the rainstorm only relying on the role of the cold air from mid- and higher-latitudes could not reach the record-breaking intensity. Further research suggested that the northward movement of an Asian monsoonal warm and wet moisture transport conveyor (MWWTC) was closely related with the active phase of a 30-60 day intra-seasonal oscillation of the Asian summer monsoon. During this time, the monsoon surge triggered and maintained the northward movement of the MWWTC. In addition, compared with another heavy rainstorm named "63.8" heavy rainstorm, which occurred over the Huaihe River Basin in the mid-August 1963 and seriously affected North China, a similar MWWTC was also observed. It was just the intense interaction of the MWWTC with strong cold air from the north that caused this severe rainstorm. [ABSTRACT FROM AUTHOR]

The impact of strong (weak) intraseasonal oscillation (ISO) over South China Sea (SCS) and South Asia (SA) in summer on the SCS and SA summer monsoon and the summer rainfall in Eastern China are studied by using the NCEP-NCAR analysis data and the rainfall data of 160 stations in China from 1961 to 2010. It is found that the impacts are significantly different in different months of summer. The study shows that in June and July cyclonic (anticyclonic) atmospheric circulation over SCS and SA corresponds to strong (weak) ISO over SCS. In August, however, strong (weak) ISO over SCS still corresponds to cyclonic (anticyclonic) atmospheric circulation over SA. In June and August cyclonic (anticyclonic) atmospheric circulation over South Asia corresponds to strong (weak) ISO over SA while a strong (weak) ISO corresponds to anticyclonic (cyclonic) atmospheric circulation over SA in July. Besides, in June the strong (weak) ISO over SA corresponds to cyclonic (anticyclonic) atmospheric circulation over SCS, while in July and August the atmospheric circulation is in the same phase regardless of whether the ISO over SA is strong or weak. The impacts of the strong (weak) ISO over SCS on the rainfall of eastern China are similar in June and July, which favors less (more) rainfall in Yangtze-Huaihe Rivers basin but sufficient (deficient) rainfall in the south of Yangtze River. However, the impacts are not so apparent in August. In South Asia, the strong (weak) ISO in July results in less (more) rainfall in the south of Yangtze River but sufficient (deficient) rainfall in Yangtze-Huaihe Rivers basin. The influence on the rainfall in eastern China in June and August is not as significant as in July. [ABSTRACT FROM AUTHOR]

The regional climate model (RegCM3), developed by the Abdus Salam International Centre for Theoretical Physics and nested in one-way mode within the latest version of Community Climate System Model from the National Center for Atmospheric Research, is used to conduct a set of experiments to examine its capability of climate simulation for the past 50 years and to explore possible changes in extreme precipitation (EP) in the next 100 years under the A1B scenario. Compared with the observation from the Climate Research Unit at the University of East Anglia and CPC Merged Analysis of Precipitation, RegCM3 reasonably reproduces the spatiotemporal distributions of precipitation and EP in eastern China. Based on the present-day analysis, this study examines the changes in monsoonal precipitation over eastern China in mid- and late-21st century relative to the reference period of 1970-1999. It is found that the precipitation will increase over the middle and lower reaches of the Yangtze River and areas to its north, and decrease over coastal areas to its south, especially in late-21st century. The various indices reflecting extreme events showed that the EP will enhance 10%-15% over the middle and lower reaches of the Yangtze River and areas to its north, and weaken over the areas to its south. The summer monsoon will strengthen and shift northwards under SERS A1B, bringing more water vapor and energy from the Indian Ocean and South China Sea for precipitation and eventually more precipitation over northern China. [ABSTRACT FROM AUTHOR]

The daily precipitation data of 740 stations in China (1958-2001) and the daily upper air data of European Centre for Medium-Range Weather Forecasts reanalysis dataset (1958-2001) are used to define an East Asian summer monsoon (EASM) index based on dynamic and thermal factors. The index is used to represent the front (or leading edge) of EASM to describe and characterize the advance and retreat of EASM objectively. During 1958-2001, the EASM movement underwent three interdecadal abrupt shifts in 1965, 1980 and 1994, respectively. During 1958-1964, the front primarily concentrated in South China and North China, while it stayed at the mid- and lower-Yangtze River for a short period. During 1965-1979, the front was located in South China and the lower reach of Yellow River for a long time. During 1980-1993, the time in which the front of EASM stayed at the mid- and lower-Yangtze River was much longer, but it settled in North China for just a short time. During 1994-2001, the front generally concentrated in the south of the mid- and lower-Yangtze River. The three interdecadal shifts of EASM directly resulted in rainfall anomalies, as well as frequent disasters of flood and drought in East China. [ABSTRACT FROM AUTHOR]

In this article, a new definition for the North Huaihe River rainy season (NHRS) is presented using summer daily precipitation in East China and subtropical high ridge axis at 500 hPa. By calculating the annual precipitation amounts in the NHRS and Meiyu of the Yangtze-Huaihe Rivers basin (YHMY) from 1961 to 2009, the dates of precipitation beginning and ending as well as the duration of the two rainy seasons in the 49 years are analyzed. Atmospheric circulation characteristics in positive and negative precipitation anomaly years during the NHRS are also studied. Results are shown as follows. (1) The new definition for the NHRS is much easier to use. It involves only two meteorological factors, making its application more practical. It can also distinguish two rainy periods of the NHRS more objectively. (2) The average duration of the NHRS is similar to that of the YHMY, except that its average dates of beginning and ending are about one week later than those of the YHMY. The average precipitation of the NHRS is slightly less than that of the YHMY, and the yearly precipitation variation of the two rainy seasons are similar to each other with no obvious increasing or decreasing trend in the 49 years, but with distinguished decadal and inter-annual variations. (3) In positive precipitation anomaly years, the South Asian high moves more northward and more eastward, the western Pacific subtropical high is located more northward and westward, and the summer monsoon is stronger than normal, resulting in the convergence of the warm and moist southwesterly airflow from the west side of the subtropical high and the cold air from the north side of the northeast trough in North Huaihe River basin. [ABSTRACT FROM AUTHOR]