Impacts of SST Warming in tropical Indian Ocean on CMIP5 model-projected summer rainfall changes over Central Asia

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.

Download Full-text

Effects of Whole SST Anomaly in the Tropical Indian Ocean on Summer rainfall Over Central Asia

Frontiers in Earth Science ◽

10.3389/feart.2021.738066 ◽

2021 ◽

Vol 9 ◽

Author(s):

Lixia Meng ◽

Yong Zhao ◽

Mingang Li

Keyword(s):

Indian Ocean ◽

Central Asia ◽

Tropical Indian Ocean ◽

Summer Rainfall ◽

Westerly Jet ◽

Anomalous Anticyclone ◽

Sst Anomaly ◽

Hadley Centre ◽

Subtropical Westerly Jet ◽

Anomalous Cyclone

The effects of sea surface temperature (SST) anomaly in the tropical Indian Ocean (IO) on summer rainfall over central Asia (CA) are investigated using NCEP/NCAR reanalysis circulation data, Hadley Centre SST data, and GPCC gridded precipitation data for 1971–2016. Results show that the SST anomalies over the whole tropical IO play important roles in modulating summer rainfall over southeast CA via the subtropical westerly jet. When the SSTs in the tropical IO are in positive phases, the south Asian monsoon is weakened, which reduces summer rainfall in the Indian monsoon regions corresponding to less release of latent heat. There is an anomalous anticyclone over the Indian Peninsula and an anomalous cyclone in the upper troposphere over CA, corresponding to a shift of the subtropical westerly jet farther south over CA. The southward shift of westerly jet would be responded to anomalous cyclone at 500 hPa over CA and water vapor transported into CA through two steps from the Arabian Sea, above both contribute to more summer rainfall over CA.

Download Full-text

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

Journal of Climate ◽

10.1175/2008jcli1959.1 ◽

2009 ◽

Vol 22 (2) ◽

pp. 201-216 ◽

Cited By ~ 62

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.

Download Full-text

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

Journal of Climate ◽

10.1175/jcli-d-14-00217.1 ◽

2014 ◽

Vol 27 (18) ◽

pp. 7086-7101 ◽

Cited By ~ 16

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).

Download Full-text

Dynamics of 2015 positive Indian Ocean Dipole

Journal of Southern Hemisphere Earth System Science ◽

10.1071/es19002 ◽

2019 ◽

Vol 69 (1) ◽

pp. 75

Author(s):

Putri Adia Utari ◽

Mokhamad Yusup Nur Khakim ◽

Dedi Setiabudidaya ◽

Iskhaq Iskandar

Keyword(s):

Heat Flux ◽

Indian Ocean ◽

Indian Ocean Dipole ◽

Tropical Indian Ocean ◽

Boreal Summer ◽

The South ◽

South Eastern ◽

Positive Indian Ocean Dipole ◽

Sst Warming ◽

Dipole Pattern

Evolution of typical positive Indian Ocean Dipole (pIOD) event was dominated by a significant sea-surface temperature (SST) cooling in the south-eastern tropical Indian Ocean. Interestingly, during the evolution of 2015 pIOD event, the SST in the south-eastern tropical Indian Ocean did not reveal significant cooling, instead anomalous strong SST warming took place in the western tropical Indian Ocean off the East African coast. This anomalous SST warming was associated with a weakening of the Asian summer monsoon. Furthermore, analysis on the mixed layer heat budget demonstrated that the evolution of the 2015 pIOD event could be attributed mainly to the air-sea heat flux. By decomposing the air-sea heat flux, it is found that reduced latent heat loss plays an important role on the SST warming in the western pole and keeping SST warm in the eastern pole. We note that a residual term also may play a role during the initial development of the event. In contrast to the SST pattern, the subsurface temperature revealed a clear positive dipole pattern. Shallow (deep) 20°C isothermal layer in the eastern (western) equatorial Indian Ocean was observed during boreal summer. This robust subsurface dipole pattern indicated that the subsurface ocean response was largely wind driven through the equatorial wave dynamics as previously suggested.

Download Full-text

Inhomogeneous warming of the Tropical Indian Ocean in the CMIP5 model simulations during 1900–2005 and associated mechanisms

Climate Dynamics ◽

10.1007/s00382-015-2602-5 ◽

2015 ◽

Vol 46 (1-2) ◽

pp. 619-636 ◽

Cited By ~ 5

Author(s):

Shuai-Lei Yao ◽

Gang Huang ◽

Ren-Guang Wu ◽

Xia Qu ◽

Dong Chen

Keyword(s):

Indian Ocean ◽

Tropical Indian Ocean ◽

Cmip5 Model ◽

Model Simulations

Download Full-text

The decadal variability of the tropical Indian Ocean SST–the South Asian High relation: CMIP5 model study

Climate Dynamics ◽

10.1007/s00382-014-2285-3 ◽

2014 ◽

Vol 45 (1-2) ◽

pp. 273-289 ◽

Cited By ~ 6

Author(s):

X. Qu ◽

G. Huang

Keyword(s):

Indian Ocean ◽

South Asian ◽

Decadal Variability ◽

Tropical Indian Ocean ◽

South Asian High ◽

Cmip5 Model ◽

The South ◽

Model Study

Download Full-text

Interdecadal Difference of Interannual Variability Characteristics of South China Sea SSTs Associated with ENSO

Journal of Climate ◽

10.1175/jcli-d-15-0057.1 ◽

2015 ◽

Vol 28 (18) ◽

pp. 7145-7160 ◽

Cited By ~ 11

Author(s):

Yali Yang ◽

Shang-Ping Xie ◽

Yan Du ◽

Hiroki Tokinaga

Keyword(s):

Indian Ocean ◽

South China Sea ◽

South China ◽

El Niño ◽

El Nino ◽

Tropical Indian Ocean ◽

Easterly Wind ◽

China Sea ◽

Sst Warming ◽

The Indian Ocean

Abstract The correlation between sea surface temperature (SST) and El Niño–Southern Oscillation (ENSO) persists into post-ENSO September over the South China Sea (SCS), the longest correlation in the World Ocean. Slow modulations of this correlation are analyzed by using the International Comprehensive Ocean–Atmosphere Dataset (ICOADS). ENSO’s influence on SCS SST has experienced significant interdecadal changes over the past 138 years (1870–2007), with a double-peak structure correlation after the 1960s compared to a single-peak before the 1940s. According to the ENSO correlation character, the analysis period is divided into four epochs. In epoch 3, 1960–83, the SST warming and enhanced precipitation over the southeastern tropical Indian Ocean, rather than the Indian Ocean basinwide warming, induce easterly wind anomalies and warm up the SCS in the summer following El Niño. Besides the Indian Ocean effect, during epochs 2 (1930–40) and 4 (1984–2007), the Pacific–Japan (PJ) pattern of atmospheric circulation anomalies helps sustain the SCS SST warming through summer (June–August) with easterly wind anomalies. The associated increase in shortwave radiation and decrease in upward latent heat flux cause the SCS SST warming to persist into the summer. Meanwhile, the rainfall response around the SCS to ENSO shows interdecadal variability, with stronger variability after the 1980s. The results suggest that both the remote forcing from the tropical Indian Ocean and the PJ pattern are important for the ENSO teleconnection to the SCS and its interdecadal modulations.

Download Full-text

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

10.21203/rs.3.rs-966527/v1 ◽

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.

Download Full-text

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

Journal of Climate ◽

10.1175/2009jcli3336.1 ◽

2010 ◽

Vol 23 (9) ◽

pp. 2389-2403 ◽

Cited By ~ 145

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.

Download Full-text