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The spatiotemporal and cloud features of the extreme rainfall under the warm and cold upper-level anomalies over the central Yungui Plateau (YGP) were investigated using the hourly rain gauge records, ERA5 reanalysis data, TRMM, and Fengyun satellite data, aiming to refine the understanding of different types of extreme rainfall. Extreme rainfall under an upper-level negative temperature anomaly (cold events) presents stronger convective cloud features when compared with the positive temperature anomaly (warm events). The maximum rainfall intensity and duration in cold events is much larger than that of warm events, while the brightness temperature of the cloud top is lower, and the ratio of convective rainfall is higher. In cold events, the middle-to-upper troposphere is dominated by a cold anomaly, and an unstable configuration with upper (lower) cold (warm) anomalies is observed around the central YGP. Although the upper-level temperature anomaly is positive, the anomalous divergence and convergence of southerly and northerly winds, as well as the strong moisture center and upward motions, are also found over the central YGP in warm events. The stronger atmospheric instability and higher convective energy under the upper-level cold anomalous circulation are closely associated with the rainfall features over the central YGP. The results indicate that the upper tropospheric temperature has significant influences on extreme rainfall, and thus more attention should be paid to the upper tropospheric temperature in future analyses. [ABSTRACT FROM AUTHOR]

Based on hourly rain gauge data and ERA5 reanalysis, the spatiotemporal features of the nocturnal heavy rainfall over the Yungui Plateau (YGP) are characterized, and the associated three-dimensional circulation patterns are revealed. A local rainfall center is found on the windward slope of the central YGP, and the diurnal peak of heavy rainfall there is at midnight, which differs from heavy rainfall over most eastern China and is ~ 3 h earlier than that for the weak rainfall events. Composite analyses show that the atmospheric circulation pattern of the heavy rainfall days is characterized by an upper-level warm anomaly covering most of eastern China with a center at 300–400 hPa. Under hydrostatic and geostrophic equilibriums, the warm anomaly contributes to the generation of an anticyclonic (cyclonic) anomaly in the upper (lower) troposphere. As a result, the anomalous divergence in the upper level and the convergence of the cold northwesterly wind and warm wet southeasterly wind in the lower level induce heavy rainfall over the central YGP. A vertical temperature anomaly appears over the northwestern YGP in several days before the heavy regional rainfall event days and gradually moves southeastwards and strengthens. Blocked by the topography, the anomalies stop moving southward and gradually weaken after the heavy RREs end. The findings indicate how large-scale circulations and specific topography interact to influence the heavy RREs over the central YGP. [ABSTRACT FROM AUTHOR]

This study investigates the rainfall characteristics during intense rainfall over Yaan against a cold-anomaly background, aiming to refine the understanding of different kinds of rainfall events across complex terrain. Hourly rain gauge records, ERA5 reanalysis data and the black body temperature of cloud tops derived from FY-2E were used. The results show that against a cold-anomaly background, the regional rainfall events (RREs) in Yaan exhibit west-to-east propagation, which is different from the north-to-south evolution of warm RREs. The middle and upper troposphere is dominated by a negative geopotential height anomaly corresponding to the cold anomaly. The cyclonic circulation at the higher level associated with the negative geopotential height anomaly bends the high-level jet to the south, forming a divergent zone over the Tibetan Plateau (TP) and guiding mid-level systems to move eastward. The cyclonic circulation at the mid-level produces a wind shear zone over the TP, generating anomalous vorticity that continuously moves eastward and develops to influence the rainfall over Yaan. The cold Yaan RREs are closely related to the TP low-pressure systems (both vortex and shearline). The anomalous vorticity over the TP can influence the local vortex over the eastern periphery of the TP at a distance mainly by the horizontal advection of anomalous vorticity by the mean flow and then enhance the local vortex mainly by anomalous convergence when it moves near Yaan. [ABSTRACT FROM AUTHOR]

A large amount of accumulated precipitation was recorded over the Eastern Periphery of the Tibetan Plateau (EPTP) in August 2020. Using hourly rain gauge records and the ERA5 reanalysis dataset, we analyzed the unique characteristics of rainfall in August and the accompanying circulation conditions and conducted a comparison with previous data. This record-breaking amount of accumulated rainfall was centered on the northern slope of the EPTP. This location was in contrast with the historical records of the concentration of rainfall over the middle and southern slopes. The hourly rainfall in August 2020 was both more frequent and more intense than the climatological mean rainfall. An amplification effect of the topography was observed, with the precipitation over the EPTP showing a more significant change with terrain height in August 2020. A circulation analysis showed that cold (warm) anomalies existed over the north (south) of approximately 35°N compared with those in the years when the southern EPTP received more rain. The western Pacific subtropical high was more intense and extended to the west, and the low-level cold air from the north was more active. The enhanced low-level southerly winds on the periphery of the subtropical high injected warm, moist air further north than the climatological mean. These winds became easterly near the northern EPTP and were forced to ascend by the steep terrain. [ABSTRACT FROM AUTHOR]

The eastern periphery of the Tibetan Plateau (EPTP), which connects the Tibetan Plateau in the west and the Sichuan Basin in the east, is a typical area with steep terrain. The performance of the ERA5 reanalysis data in revealing the regional rainfall events (RREs) over the EPTP was evaluated by conducting a comparison with the rain‐gauge data. The results showed that the ERA5 precipitation could capture the general spatiotemporal features of the evolution of the observed RREs with spatial correlation coefficients greater than 0.8, but obvious bias still existed. The rainfall frequency was generally greater and the rainfall intensity was weaker in the ERA5 precipitation from the Tibetan Plateau to the Sichuan Basin, with the rainfall amount being smaller over the EPTP and Sichuan Basin and larger over the eastern Tibetan Plateau. ERA5 precipitation tended to start earlier and end later relative to the RREs in the gauge data. During the RREs, the distribution of the precipitation intensity in ERA5 was weaker and more uniform than that of the gauge records, and the spatial ranges were larger, which responded well to the higher rainfall frequency but weaker intensity in ERA5 when compared with the gauge data. These findings remind us that attention should be paid when using reanalysis precipitation, especially over complex terrain such as that of the EPTP. Moreover, the incorrect timing of the ERA5 precipitation and the underestimation of the precipitation intensity indicated that problems still exist in the state‐of‐the‐art model system. [ABSTRACT FROM AUTHOR]

Accurate simulation and prediction of intense precipitation events require better understanding of their physical mechanisms. This study uses Yaan—a place with regional maximum rainfall in central China—to investigate the cause and process of intense precipitation. Hourly rain gauge records and the new ERA5 reanalysis are used to characterize the evolution process of warm season intense regional rainfall events (RREs) in Yaan and its associated three-dimensional circulation. Results show that before the start of the Yaan intense RREs, moderate rainfall amount (frequency) appears northeast of the key region. The rainfall then moves southward in the following several hours along the eastern periphery of the Tibetan Plateau where it reaches peak. It then moves to and end up in the south and southeast Sichuan Basin. The progression of the RREs is found to be associated with a counter-clockwise rotation of anomalous surface winds associated with a developing mesoscale surface low-pressure center, which is further associated with the southeastward progression of a large-scale synoptic scale wave. The easterly phase of the winds in the counter-clockwise rotation causes upslope motion perpendicularly toward the terrain that leads to maximum rainfall. The findings illustrate how large-scale circulations, mesoscale systems, and specific topographic features interact to create the RREs evolution in Yaan. [ABSTRACT FROM AUTHOR]

This study examines the differences in diurnal variations of summer (June-August) rainfall recorded in the station rain gauge data (Gdata) and Tropical Rainfall Measuring Mission 3B42 product (Tdata) over central eastern China during 1998-2006. For the diurnal variations, rainfall amount and frequency in Tdata get the maximum in the afternoon, against the double diurnal peaks in the morning and afternoon of Gdata. For the intensity, the principal morning peak in Tdata contrasts with the dominated afternoon peak in Gdata. It is found that the massive morning light rainfall, which is missed by Tdata, greatly contributes to the weakened morning diurnal peaks of amount and frequency and the stronger morning intensity in Tdata. The overestimated afternoon rainfall in Tdata, including the light rainfall detected only by Tdata and the enhanced rainfall in Tdata when both datasets measure the rainfall, strengthens the afternoon peak of rainfall amount and frequency. In addition, the light rainfall in the morning missed by Tdata is more prevalent in plains than in mountains, whereas the overestimation of afternoon rainfall is more significant in mountain regions. For the diurnal rainfall amount, the afternoon peak in Tdata differs from the morning peak in Gdata in plains and the afternoon peak of Tdata is enhanced in mountain regions. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]