Summer Rainfall Variability in Low-Latitude Highlands of China and Subtropical Indian Ocean Dipole

2014 ◽  
Vol 27 (2) ◽  
pp. 880-892 ◽  
Author(s):  
Jie Cao ◽  
Ping Yao ◽  
Lin Wang ◽  
Kui Liu
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Arabian Sea ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Wind Component ◽  
Vertical Circulation ◽  
Low Latitude ◽  
Divergent Wind ◽  
Rainfall Variations

Abstract Based on reanalysis and observational datasets, this study proposes a reasonable mechanism for summer rainfall variations over the low-latitude highlands (LLH) of China, in which a subtropical Indian Ocean dipole (SIOD)-like pattern is the key external thermal forcing. In summers with a positive SIOD-like pattern, sea surface temperature (SST) anomalies may lead to lower-tropospheric divergence over the tropical Indian Ocean and convergence over the subtropical southwestern Indian Ocean and Arabian Sea. The convergence over the Arabian Sea can induce easterly anomalies of the divergent wind component off the eastern coast of the Bay of Bengal (BOB), while the divergence over the tropical Indian Ocean can change the interhemispheric vertical circulation and produce a descending motion over the same area and cyclonic anomalies in the rotational wind component over the Indian peninsula. The combined effect of the divergent and rotational wind anomalies and enhanced interhemispheric vertical circulation facilitates easterly anomalies and weakens climatological water vapor flux to the northern BOB. Therefore, anomalous water vapor divergence and less precipitation are observed over the LLH. In summers with a negative SIOD-like pattern, the situation is approximately the same but with opposite polarity and a weaker role of the divergent wind component. Further analyses indicate that the summertime SIOD-like pattern can be traced to preceding seasons, especially in positive SIOD-like years. The SST–wind–evaporation feedback mechanism could account for maintenance of the SIOD-like pattern. These results provide efficient prediction potential for summer rainfall variations over the LLH.

scholarly journals Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

2009 ◽  
Vol 22 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Lina Zhang ◽  
Bizheng Wang ◽  
Qingcun Zeng
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Energy Propagation ◽  
Southeast China ◽  
The Indian Ocean ◽  
The Impact ◽  
The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

scholarly journals Variability of Summer Rainfall in Northeast China and Its Connection with Spring Rainfall Variability in the Huang-Huai Region and Indian Ocean SST

2014 ◽  
Vol 27 (18) ◽  
pp. 7086-7101 ◽  
Author(s):  
Zongting Gao ◽  
Zeng-Zhen Hu ◽  
Jieshun Zhu ◽  
Song Yang ◽  
Rong-Hua Zhang ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Northeast China ◽  
General Circulation ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Rainfall Anomaly ◽  
Atmospheric Modeling ◽  
Late Spring ◽  
Local Soil ◽  
The Impact

Abstract In this work, the variability of summer [June–August (JJA)] rainfall in northeast China is examined and its predictors are identified based on observational analyses and atmospheric modeling experiments. At interannual time scales, the summer rainfall anomaly in northeast China is significantly correlated with the rainfall anomaly over the Huang-Huai region (32°–38°N, 105°–120°E) in late spring (April–May). Compared with climatology, an earlier (later) rainy season in the Huang-Huai region favors a wet (dry) summer in northeast China. Also, this connection has strengthened since the late 1970s. In addition to the impact of the sea surface temperature anomaly (SSTA) in the tropical Indian Ocean, the local soil moisture anomalies caused by the rainfall anomaly in the Huang-Huai region in late spring generate summer general circulation anomalies, which contribute to the rainfall anomaly in northeast China. As a result, when compared with the SSTA, the rainfall anomaly in the Huang-Huai region in late spring can be used as another and even better predictor for the summer rainfall anomaly in northeast China. The results from atmospheric general circulation model experiments forced by observed SST confirm the diagnostic results to some extent, including the connection of the rainfall anomaly between the Huang-Huai region in April–May and northeastern China in JJA as well as the influence from SSTA in the tropical Indian Ocean. It is shown that eliminating the internal dynamical processes by using the ensemble mean intensifies the connection, implying that the connection of rainfall variation in the two different seasons/regions may be partially caused by the external forcing (e.g., SSTA in the tropical Indian Ocean).

scholarly journals Tropical Origins of the Record-breaking 2020 Summer Rainfall Extremes in East Asia

2021 ◽  
Author(s):  
Sunyong Kim ◽  
Jae-Heung Park ◽  
Jong-Seong Kug
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
Wave Train ◽  
East Asian ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Ocean Basin ◽  
Boreal Summer ◽  
Rainfall Extremes ◽  
East Asian Rainfall

Abstract The East Asian countries have experienced heavy rainfalls in boreal summer 2020. Here, we investigate the dynamical processes driving the East Asian rainfall extremes during July and August. The Indian Ocean basin warming in June can be responsible for the anticyclonic anomalies in the western North Pacific (WNP), which contribute to the zonally-elongated rainfalls in East Asia during July through an atmospheric Rossby wave train. In August, the East Asian rainfall increase is also related to the anticyclonic anomalies in the subtropical WNP, although it is located further north. It is suggested that the north tropical Atlantic warming in June partly contributes to the subtropical WNP rainfall decrease in August through a subtropical teleconnection. The rainfall decrease in the subtropical WNP region during August drives the local anticyclonic anomalies that cause the rainfall increase in East Asia. The tropical Indian Ocean anomalously warmed in June and the subtropical WNP rainfall decreased in August 2020, which played a role in modulating the WNP anticyclonic anomalies. Therefore, the record-breaking rainfalls in East Asia occurred during July and August 2020 can potentially be explained by the teleconnections induced by the tropical origins, such as tropical Indian Ocean warming and subtropical WNP rainfall decrease.

scholarly journals An Interdecadal Change in Southern China Summer Rainfall around 1992/93

2010 ◽  
Vol 23 (9) ◽  
pp. 2389-2403 ◽  
Author(s):  
Renguang Wu ◽  
Zhiping Wen ◽  
Song Yang ◽  
Yueqing Li
Keyword(s):  
Indian Ocean ◽  
Temperature Change ◽  
Southern China ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Interdecadal Change ◽  
The Tibetan Plateau ◽  
Anomalous Anticyclone ◽  
Upper Level

Abstract The present study documents a pronounced interdecadal change in summer rainfall over southern China around 1992/93 and explores the plausible reasons for this change. The summer rainfall is persistently below normal during 1980–92 and above normal during 1993–2002. Coherent changes in atmospheric circulation are identified over East Asia and the South China Sea (SCS)–western North Pacific (WNP). The increase in rainfall is accompanied by an increase in lower-level convergence, midtropospheric ascent, and upper-level divergence over southern China. The changes in lower-level winds feature two anomalous anticyclones: one over the SCS–subtropical WNP, and the other over north China–Mongolia. The outflows from the two anomalous anticyclones converge over southern China, leading to anomalous moisture convergence, enhanced ascent, and increased rainfall. The development of the northern anticyclone is related to an increase in the Tibetan Plateau snow cover in the preceding winter–spring that leads to a contrast in temperature change between the plateau and the surrounding regions. The relatively small temperature change over the plateau, coupled with increases in temperature to the west and the east, leads to an increase in surface pressure extending northward from the plateau. The development of the southern anticyclone is related to an increase in sea surface temperature in the equatorial Indian Ocean that enhances lower-level convergence and ascent. The accompanying upper-level divergent flows from the tropical Indian Ocean to the SCS–WNP lead to the development of anomalous descent and lower-level anomalous anticyclone over the SCS–WNP.

scholarly journals Breakdown of the Relationship between Australian Summer Rainfall and ENSO Caused by Tropical Indian Ocean SST Warming

2018 ◽  
Vol 31 (6) ◽  
pp. 2321-2336 ◽  
Author(s):  
Zhiwei Zhu
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
La Niña ◽  
Maritime Continent ◽  
La Nina ◽  
Sst Warming ◽  
The Indian Ocean ◽  
Rainfall Anomalies ◽  
The Relationship

The relationship between El Niño–Southern Oscillation (ENSO) and Australian summer rainfall (ASR) during 1960–2015 experienced an interdecadal change around the mid-1980s. Before the mid-1980s, ASR was significantly correlated with tropical central Pacific (TCP) sea surface temperature (SST), whereas after that it was not. While El Niño was always independent from ASR, La Niña had a close relationship with ASR. However, this relationship was weakened after the mid-1980s. The Indian Ocean SST warming might contribute to the weakening relationship between La Niña and ASR. For La Niña events before the mid-1980s, the negative SSTA over TCP and the southern tropical Indian Ocean induced a large-scale lower-level cyclonic anomaly over Australia, leading to nearly uniform positive precipitation over Australia. In this manner, a significant relationship between ASR and La Niña was established. On the contrary, for the La Niña events after the mid-1980s, because of the Indian Ocean SST warming, the equatorial eastern Indian Ocean and Maritime Continent presented positive SSTAs and enhanced moisture, favoring enhanced rainfall anomalies over the equatorial Maritime Continent. This enhanced rainfall condensation heating induced a lower-level cyclonic anomaly to the west of Australia. The northerly anomalies at the eastern flank of this cyclonic anomaly counteracted the southerly anomalies at the western flank of the cyclonic anomaly over eastern Australia induced by the negative TCP SSTA, leading to insignificant circulation and rainfall anomalies over Australia. As such, being interfered with by the equatorial Maritime Continent heating, the relationship between ASR and La Niña was weakened.

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