scholarly journals Response of the Indian Ocean to the Tibetan Plateau Thermal Forcing in Late Spring

2019 ◽  
Vol 32 (20) ◽  
pp. 6917-6938 ◽  
Author(s):  
Yu Zhao ◽  
Anmin Duan ◽  
Guoxiong Wu ◽  
Ruizao Sun
Keyword(s):  
Indian Ocean ◽  
Tibetan Plateau ◽  
Mixed Layer ◽  
General Circulation ◽  
Late Spring ◽  
Water Volume ◽  
The Tibetan Plateau ◽  
Northern Indian Ocean ◽  
Thermal Forcing ◽  
The Indian Ocean

Abstract The thermal effect of the Tibetan Plateau (TP) is known to exert substantial impacts on the atmospheric general circulation, suggesting that it may also influence the wind-driven circulation in the ocean through air–sea interactions. Here, several coupled general circulation model experiments are performed in order to investigate the short-term response of the Indian Ocean to the TP surface heat source in late spring (May). The results indicate that positive TP heating anomalies can induce significant atmospheric circulation responses over the northern Indian Ocean, characterized by easterly anomalies in the upper troposphere due to the enhanced South Asian high and lower-level southwesterly anomalies from the heat pumping effect. As a result, the surface wind speed over the northern Indian Ocean is reinforced, leading to intensified oceanic evaporation and subsequently cooler potential temperatures in the mixed layer. Wind-driven currents in the mixed layer are also affected. In the Bay of Bengal, Ekman transport facilitates water volume movement from west to east. In the Arabian Sea, water movement is weaker and the southward component is relatively more important. Both these areas show local meridional circulations with offshore upwelling in the northwest. Moreover, the cross-equatorial current is also enhanced in the eastern part of the tropical Indian Ocean. Overall, the upper layer in the northern Indian Ocean is efficiently modulated by the TP thermal forcing within one month.

scholarly journals Opposite responses of the Indian Ocean to the thermal forcing of the Tibetan Plateau before and after the onset of the South Asian monsoon

2021 ◽  
pp. 1-56
Author(s):  
Yu Zhao ◽  
Anmin Duan ◽  
Guoxiong Wu
Keyword(s):  
Indian Ocean ◽  
Tibetan Plateau ◽  
South Asian ◽  
Asian Monsoon ◽  
Monsoon Onset ◽  
The Tibetan Plateau ◽  
Thermal Forcing ◽  
The North ◽  
Before And After ◽  
The Indian Ocean

AbstractThe atmospheric circulation changes dramatically over a few days before and after the onset of the South Asian monsoon in spring. It is accompanied by the annual maximum surface heating over the Tibetan Plateau. We conducted two sets of experiments with a coupled general circulation model to compare the response of atmospheric circulation and wind-driven circulation in the Indian Ocean to the thermal forcing of the Tibetan Plateau before and after the monsoon onset. The results show that the Tibetan Plateau's thermal forcing modulates the sea surface temperature (SST) of the Indian Ocean and the meridional circulation in the upper ocean with opposite effects during these two stages. The thermal forcing of the Tibetan Plateau always induces a southwesterly response over the northern Indian Ocean and weakens the northeasterly background circulation before the monsoon onset. Subsequently, wind-evaporation feedback results in a warming SST response. Meanwhile, the oceanic meridional circulation shows offshore upwellings in the north and southward transport in the upper layer crossing the equator, sinking near 15°S. After the monsoon onset, the thermal forcing of the Tibetan Plateau accelerates the background southwesterly and introduces a cooling response to the Indian Ocean SST. The response of oceanic meridional overturning circulation is limited to the north of the equator due to the location and structural evolution of the climatological local Hadley circulation. With an acceleration of the local Walker circulation, the underlying zonal currents also show corresponding changes, including a westerly drift along the equator, downwelling near Indonesia, offshore upwelling near Somalia, and a westward undercurrent.

scholarly journals Quantitative Analysis of Water Vapor Transport during Mei-Yu Front Rainstorm Period over the Tibetan Plateau and Yangtze-Huai River Basin

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Hao Yang ◽  
Guan-yu Xu ◽  
Xiaofang Wang ◽  
Chunguang Cui ◽  
Jingyu Wang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tibetan Plateau ◽  
Heavy Rainfall ◽  
Initial Position ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Huai River ◽  
The Indian Ocean

There are continuous precipitation systems moving eastward from the Tibetan Plateau to the middle and lower reaches of the Yangtze-Huai River during the Mei-yu period. We selected 20 typical Mei-yu front precipitation cases from 2010 to 2015 based on observational and reanalysis data and studied the characteristics of their environmental fields. We quantitatively analyzed the transport and sources of water vapor in the rainstorms using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT_4.9) model. All 20 Mei-yu front precipitation cases occurred in a wide region from the Tibetan Plateau to the Yangtze-Huai River. The South Asian high and upper level jet stream both had strong intensities during the Mei-yu front rainstorm periods. Heavy rainfall mainly occurred in the divergence zone to the right of the high-level jet and in the convergence zone of the low-level jet, where strong vertical upward flows provided the dynamic conditions required for heavy rainfall. The water vapor mainly originated from the Indian Ocean, Bay of Bengal, and South China Sea. 52% of the air masses over the western Tibetan Plateau originated from Central Asia, which were rich in water vapor. The water vapor contribution at the initial position was only 41.5% due to the dry, cold air mass over Eurasia, but increased to 47.6% at the final position. Over the eastern Tibetan Plateau to the Sichuan Basin region, 40% of the air parcels came from the Indian Ocean, which was the main channel for water vapor transport. For the middle and lower reaches of the Yangtze River, 37% of the air parcels originated from the warm and humid Indian Ocean. The water vapor contribution at the initial position was 38.6%, but increased to 40.2% after long-distance transportation.

Has the Tibetan plateau risen in the Early/Mid–Miocene? Constraints from plate–motion reconstructions and seismicity of the Indian Ocean lithosphere

2021 ◽  
Author(s):  
Giampiero Iaffaldano
Keyword(s):  
Indian Ocean ◽  
Tibetan Plateau ◽  
Tectonic Setting ◽  
Plate Motion ◽  
Tibet Plateau ◽  
Geochemical Data ◽  
The Tibetan Plateau ◽  
Plate Motions ◽  
The Indian Ocean ◽  
Ocean Lithosphere

Summary Magnetisation records and seismic stratigraphy of the Indian Ocean lithosphere indicate that the Early/Mid–Miocene onset of diffuse contractional deformation coincided with slowdowns of the Indian and Capricorn plate motions. At present day such deformation is evidenced by the seismicity of the Indian ocean floor. Deformation onset and past plate–motion slowdowns have been interpreted as consequences of a sudden uplift of the Tibetan plateau by 1 to 2 km, as this – following previous estimates – would generate a tectonically–significant force between 4 · 1012 and 8 · 1012 N/m. However, this view remains at odds with paleo–altimetry estimates from geological and geochemical data, which indicate no increase in plateau altitude throughout the Miocene. Here I use well–established models of viscous/brittle dynamics in inverse mode in order to constrain the amount of force that should be delivered by the Tibetan region to the Indian tectonic setting in order to explain the observations above. Results constrain such a force within the range from 4.3 · 1011 to 3.5 · 1012 N/m. By comparison with previous estimates of the force associated with topography increase, these analyses suggest that the Early/Mid–Miocene onset of contractional deformation and plate–motion slowdowns within the Indian Ocean require minimal uplift of the Tibet plateau of a few hundred meters. The seemingly–contradicting inferences on Early/Mid–Miocene Tibetan uplift that come from geophysical and geological/geochemical observations can be reconciled by noting that the required uplift amount is less than what is resolvable by modern paleo–altimetry techniques.

scholarly journals Association between regional monsoon onset in South Asia and Tibetan Plateau thermal forcing

2021 ◽  
Author(s):  
Die Hu ◽  
Anmin Duan ◽  
Ping Zhang
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Summer Monsoon ◽  
General Circulation ◽  
Diabatic Heating ◽  
Monsoon Onset ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
South Asian Summer Monsoon ◽  
Thermal Forcing

Abstract By using multiple data sources and two sensitivity experiments using the atmospheric general circulation model of CAM4.0, we investigated the effect of thermal forcing over the Tibetan Plateau (TP) on the onset of the South Asian summer monsoon, including over the Arabian Sea (AS) and India. Results indicate that the seesaw pattern of diabatic heating over the TP, with a southeastern–northwestern inverse distribution in May, shows a robust relationship with the date of monsoon onset over the AS and India, which is independent of the influences from ocean signals. A positive diabatic heating seesaw pattern can enhance the ascending (descending) motion over the southeastern (northwestern) TP, corresponding to above (below) normal in- situ precipitation. Temperature budget diagnosis reveals that the adiabatic heating by the anomalous vertical motion and relevant horizontal advection of temperature convergence in the mid-upper troposphere are contributors to the warming over the TP. Consequently, the transition of the meridional temperature gradient over South Asian regions occurs earlier. Furthermore, the diabatic heating over the TP induces an enhanced and westward-extended South Asian high (SAH), which together with the easterly along the southern flank of the SAH superimpose on the low-level westerly flow over the AS and India, resulting in intensive upper-level divergence-pumping and upward motion. This anomalous circulation configuration in lower and upper levels further facilitates an earlier onset of summer monsoon in these two regions. These findings are corroborated in the sensitivity runs based on CAM4.0.

scholarly journals Interannual Variability of the North Pacific Mixed Layer Associated with the Spring Tibetan Plateau Thermal Forcing

2019 ◽  
Vol 32 (11) ◽  
pp. 3109-3130 ◽  
Author(s):  
Ruizao Sun ◽  
Anmin Duan ◽  
Lilan Chen ◽  
Yanjie Li ◽  
Zhiang Xie ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
Mixed Layer ◽  
North Pacific ◽  
General Circulation ◽  
Sea Surface ◽  
The Tibetan Plateau ◽  
The North ◽  
Anomalous Anticyclone ◽  
The North Pacific

Abstract By using multisourced data and two sets of sensitivity runs from the coupled general circulation model CESM1.2.0, we investigated the effects of the spring [March, April, and May (MAM)] surface sensible heating over the Tibetan Plateau (SHTP) on the interannual variability of the North Pacific Ocean sea surface temperature (SST) and mixed layer. The results indicated that an above-normal MAM SHTP can generate a Rossby wave downstream and form an anomalous equivalent barotropic anticyclone over the North Pacific, inducing anticyclonic wind stress anomalies. As a result of Ekman transport and Ekman pumping, sea currents converge near 40°N, accompanied by weak downwelling motion. The mixed layer heat budget diagnosis indicates that the net heat fluxes, together with meridional advection anomalies, contributed significantly to changes in the mixed layer temperature (MLT). As a result, the SST anomalies (SSTAs) and MLT anomalies both present a horseshoelike pattern. In addition, the significant warm SSTAs show a maximum in the late spring, but the significant warm MLT anomalies centered under the sea surface (25-m depth) could be sustained until summer, acting like a signal storage for the anomalous spring SHTP. Moreover, the midlatitude ocean–atmosphere interaction provides a positive feedback on the development of the anomalous anticyclone over the North Pacific, since the SSTA pattern could strengthen the oceanic front and induce more active transient eddy activities. The eddy vorticity forcing that is dominant among the total atmospheric forcings tends to produce an equivalent barotropic atmospheric high pressure, which in turn intensifies the initial anomalous anticyclone.

An Observing System Simulation Experiment for the Indian Ocean

2007 ◽  
Vol 20 (13) ◽  
pp. 3300-3319 ◽  
Author(s):  
Gabriel A. Vecchi ◽  
Matthew J. Harrison
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Sampling Interval ◽  
Temperature Variability ◽  
Subseasonal Variability ◽  
The Indian Ocean ◽  
Moored Buoy

Abstract An integrated in situ Indian Ocean observing system (IndOOS) is simulated using a high-resolution ocean general circulation model (OGCM) with daily mean forcing, including an estimate of subdaily oceanic variability derived from observations. The inclusion of subdaily noise is fundamental to the results; in the mixed layer it is parameterized as Gaussian noise with an rms of 0.1°C; below the mixed layer a Gaussian interface displacement with an rms of 7 m is used. The focus of this assessment is on the ability of an IndOOS—comprising a 3° × 3° Argo profiling float array, a series of frequently repeated XBT lines, and an array of moored buoys—to observe the interannual and subseasonal variability of subsurface Indian Ocean temperature. The simulated IndOOS captures much of the OGCM interannual subsurface temperature variability. A fully deployed Argo array with 10-day sampling interval is able to capture a significant part of the Indian Ocean interannual temperature variability; a 5-day sampling interval degrades its ability to capture variability. The proposed moored buoy array and frequently repeated XBT lines provide complementary information in key regions, particularly the Java/Sumatra and Somali upwelling and equatorial regions. Since the subdaily noise is of the same order as the subseasonal signal and since much of the variability is submonthly, a 5-day sampling interval does not drastically enhance the ability of Argo to capture the OGCM subseasonal variability. However, as sampling intervals are decreased, there is enhanced divergence of the Argo floats, diminished ability to quality control data, and a decreased lifetime of the floats; these factors argue against attempting to resolve subseasonal variability with Argo by shortening the sampling interval. A moored array is essential to capturing the subseasonal and near-equatorial variability in the model, and the proposed moored buoy locations span the region of strong subseasonal variability. On the whole, the proposed IndOOS significantly enhances the ability to capture both interannual and subseasonal variability in the Indian Ocean.

scholarly journals Vertical Motion of Air over the Indian Ocean and the Climate in East Asia

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2641
Author(s):  
Rongxiang Tian ◽  
Yaoming Ma ◽  
Weiqiang Ma
Keyword(s):  
Indian Ocean ◽  
Tibetan Plateau ◽  
East Asia ◽  
Yangtze River Basin ◽  
Vertical Motion ◽  
The Tibetan Plateau ◽  
Comprehensive Understanding ◽  
Clockwise Rotation ◽  
The Yangtze River Basin ◽  
The Indian Ocean

The Indian Ocean and East Asia are the most famous monsoonal regions, and the climate of East Asia is affected by the change in wind direction due to monsoons. The vertical motion of the atmosphere is closely related to the amount of precipitation in whichever particular region. Climate diagnosis and statistical analysis were used to study the vertical motion of air over the Indian Ocean and its relationship with the climate in East Asia. The vertical motion of air over the Indian Ocean had a significant correlation with the climate in China—especially with precipitation in the Tibetan Plateau and the Yangtze River Basin—as a result of the interaction of the vertical motion of air from the Indian Ocean, the Tibetan Plateau and the subpolar region in the Northern Hemisphere. The vertical motion over the Indian Ocean was weakened from 1981 to 2010, except at a height of 500 hPa in winter. The vertical motion of air over the Indian Ocean had a period of 7–9 years in summer and 9–12 years in winter. An ascending motion was dominant over most of the Indian Ocean throughout the year and the central axis of the ascending motion changed from a clockwise rotation from winter to summer to a counterclockwise rotation from summer to winter as a result of the monsoonal circulation over the Indian Ocean. These results will provide a theoretical reference for a comprehensive understanding of the climate in Asia and contribute to work on climate prediction in these regions.

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