Search Results (7)

Using multi-source precipitation datasets including NASA GPM (IMERG), GPCP, ECMWF ERA5, and station precipitation data from the China Meteorological Administration (CMA), along with ERA5 reanalysis fields for atmospheric circulation analysis, this study investigates the extreme precipitation events during the “Dragon-Boat Precipitation” period from 20 May to 21 June over South China in 2022 using the synoptic diagnostic method. The results indicate that the total precipitation during this period significantly exceeded the climatological average, with multiple large-scale extreme rainfall events characterized by high intensity, extensive coverage, and prolonged duration. The spatial distribution of precipitation exhibited a north-more-south-less pattern, with the maximum rainfall center located in the Nanling Mountains, particularly in the Shaoguan–Qingyuan–Heyuan region of Guangdong Province, where peak precipitation exceeded 1100 mm, and the mean precipitation was approximately 1.7 times the climatology from the GPM data. The average daily precipitation throughout the period was 17.5 mm/day, which was 6 mm/day higher than the climatological mean, while the heaviest rainfall on 13 June reached 39 mm/day above the average, exceeding two standard deviations. The extreme precipitation during the “Dragon-Boat Precipitation” period in 2022 was associated with an anomalous deep East Asian trough, an intensified South Asian High, a stronger-than-usual Western Pacific Subtropical High, an enhanced South Asian monsoon and South China Sea monsoon, and the dominance of a strong Southwesterly Low-Level Jet (SLLJ) over South China. Two major moisture transport pathways were established: one from the Bay of Bengal to South China and another from the South China Sea, with the latter contributing a little higher amount of water vapor transport than the former. The widespread extreme precipitation on 13 June 2022 was triggered by the anomalous atmospheric circulation conditions. In the upper levels, South China was located at the northwestern periphery of the slightly stronger-than-normal Western Pacific Subtropical High, intersecting with the base of a deep trough associated with an anomalous intense Northeast China Cold Vortex (NCCV). At lower levels, the region was positioned along a shear line formed by anomalous southwesterly and northerly winds, where exceptionally strong southwesterly moisture transport, significant moisture convergence, and intense vertical updraft led to the widespread extreme rainfall event on that day. Full article

Understanding the characteristics of the Northeast China Cold Vortex (NCCV) during the warm season (May to September) is essential for enhancing the forecast skills in Northeast China. This study employed ERA5 reanalysis data over 2012–2022 and the optimized K-means clustering algorithm to classify NCCV tracks into five types: (A) eastward-moving dissipative, (B) eastward-moving retrogressive, (C) short-range eastward-moving offshore, (D) long-range eastward-moving offshore, and (E) long-range southeastward-moving offshore. The results demonstrated that variations in circulation configurations governed the tracks of the NCCVs, bringing about the diversity in the center intensity, lifespan, movement speed, and rainstorm probability results. Specifically, the blocking high (BH) over the Sea of Okhotsk served as the primary control system, favoring slow-moving, long-lived NCCVs (type A and type B), which were associated with a higher probability of cold vortex (CV) rainstorms. However, fast-moving, the short-lived NCCVs (type C) had a weaker impact on precipitation. A spatiotemporal analysis further revealed obvious inter-monthly variation in NCCV tracks. From May to August, under the influence of the northward-moving subtropical high and the strengthening of the BH, the occurrence of types A and B increased, while the occurrence of other types decreased. This synoptic shift promoted moisture transport into Northeast China, increasing the frequency of CV rainstorms in July and August. Full article

Rainstorms always occur in the southeast and northeast quadrants of the Northeast China Cold Vortex (NCCV), resulting in significant flooding. This study investigated water vapor and trigger mechanisms for rainstorms within these two regions of an NCCV event during 11–14 June 2022 in terms of Lagrangian backward tracking, stratification stability, and upward motion using the ERA5 reanalysis. In the mid-troposphere, a quasi-stationary “ridge-NCCV-ridge” pattern resided over northeastern China, with an “anticyclonic-cyclonic-anticyclonic” airflow in the lower troposphere. As a result, water vapor originated from the Yellow Sea and was transported in an “L” shape toward both two regions. The southeast region was influenced by southwesterly and northwesterly airflows, resulting in the convergence of moist air from the Yangtze River and Lake Baikal and significant vertical shear of positive vorticity advection. This dynamic created deep and pronounced upward currents in the southeast of the NCCV, leading to the development of intensive and extensive rainstorms in situ. In contrast, the northeast region of the NCCV was dominated by southerly airflow. The moist air converged against the lee side of the Great Khingan Mountains and generated shallow, unstable stratification. The upward motion in this area was relatively weaker and thus induced regional rainstorms. Full article

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. Full article

In the early summer (June) of 2022, the spatial mean precipitation in northeast China (NEC) was 62% higher than normal and broke the historical record since 1951. Based on the precipitation data of 245 meteorological stations in NEC and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, this paper analyzes the role of large-scale circulation and sea-surface temperature (SST) associated with anomalous precipitation over NEC in June using singular value decomposition (SVD), correlation analysis, regression analysis, and composite analysis methods, and further investigates the possible cause of the abnormal precipitation in June 2022. Results show that the northeast China cold vortex (NCCV) accompanying the blocking high in the Okhotsk Sea (BHOS) has been the primary mid-to-high latitude atmospheric circulation pattern affecting NEC precipitation in June since 2001. This circulation pattern is closely related to the tripole SST pattern over the North Atlantic (NAT) in March. In June 2022, the NAT SST anomaly in March stimulates eastward-propagating wave energy, resulting in the downstream anomalous circulation pattern in which the NCCV cooperates with the BHOS in the mid-high latitudes of East Asia. Under this background atmospheric circulation favorable for precipitation, the Kuroshio region SST anomaly in June led to a more northward and stronger anomalous anticyclone in the northwestern Pacific through local air–sea interaction, which provides more sufficient water vapor for NEC, resulting in unprecedented precipitation in June 2022. Full article

In this study, by using the ERA5 data of the atmospheric circulation field that was re-analyzed by the ECMWF (European Centre for Medium-Range Weather Forecasts), we revealed the features of the Northeast China Cold Vortex (NCCV) from 1950 to 2020 (including active days, occurrence time of NCCV processes, and process durations). This study focused on a comparative analysis of the differences in the NCCV’s climate characteristics in the cold and warm periods to help future predictions. The results revealed the following: From 1950 to 2020, the NCCV occurred 2961 times on 9782 days. The average annual occurrence time of NCCV processes, annual average of cold vortex days, and average process duration of the NCCVs were 41.7 times, 137.8 days, and 3.6 days, respectively. These indicators of the NCCVs showed an increasing trend, but the trend was not significant. The NCCVs occurred most frequently in May, followed by June, and were located at the southernmost point in June. Therefore, it had the most active days and a relatively long process duration in May and June, significantly impacting Northeast China. During the cold period (1950–1980), the annual occurrence time of NCCV processes, number of cold vortex days, and the process duration of the NCCVs all showed an increasing trend, while in the warm period, these showed a decreasing trend. In addition, the durations of the NCCVs decreased significantly in the warm period, which indicated that the NCCV processes continued to weaken after climate warming. During the warm period (1981–2020), the frequency and active days of the NCCVs throughout the year and most months increased, and its general location was more southerly than in the cold period. Moreover, the annual average occurrence time of NCCV processes, number of active days, and average duration of the NCCV in the warm period were more than those in the cold period. Finally, the NCCVs continued for longer in autumn and winter than in spring and summer, and the durations of the NCCVs increased in warm periods. Full article

The Northeast China cold vortex (NCCV) often occurs in spring and summer, causing extreme weather such as rainstorm and hail in Northeast China. The brightness temperature (TB) observations of Microwave Temperature Sounder-2 (MWTS-2) on board Fengyun-3D (FY-3D), which can provide atmospheric temperature in various vertical layers, are firstly limb-corrected and then applied to track the origin and movement of four NCCV cases in June and July 2019. Results show that a cold core is observed at the location of NCCVs in TB observations of channels 4 and 5, whose peak weighting function (WF) altitudes are 700 and 400 hPa, respectively, indicating the cold structure of NCCVs in the middle and lower troposphere. The TB observations of channels 6 and 7, which measure the atmospheric temperature around 250 and 200 hPa, respectively, capture a warm core structure of NCCVs in the upper troposphere and lower stratosphere. Being less affected by the low-level cloud and rain, TB observations of channels 6 and 7 are applied to identify and track the warm cores of NCCVs. The NCCV tracks of movement identified by MWTS-2 observations compare well with those determined by the 500 hPa geopotential height and the 300 hPa potential vorticity (PV) anomaly from the ERA5 reanalysis. Both clearly show that the NCCVs were originated from high latitudes, then moved southeastward, and finally entered Northeast China. The entire process took several days. Therefore, TB observations of MWTS-2 can be used to identify the precursors of NCCVs and monitor their appearances, developments, and movements in time. With the flourishing development of Fengyun satellite series in China as well as the already existing 40 years of microwave sounder observations worldwide, this research provides a new way to investigate the synoptic and climatological features of NCCVs. Full article