Inter-annual variability of moisture transport over the northern Indian Ocean and South Asian summer monsoon

2018 ◽  
Vol 75 (1) ◽  
pp. 23-31 ◽  
Author(s):  
FS Syed ◽  
A Hannachi
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Summer Monsoon ◽  
Moisture Transport ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
Northern Indian Ocean ◽  
Annual Variability ◽  
Asian Summer

scholarly journals Three types of positive Indian Ocean dipoles and their relationships with the South Asian summer monsoon

2021 ◽  
pp. 1-67
Author(s):  
Jilan Jiang ◽  
Yimin Liu ◽  
Jiangyu Mao ◽  
Jianping Li ◽  
Shuwen Zhao ◽  
...  
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Mature Phase ◽  
Asian Summer ◽  
Type C ◽  
Southeasterly Wind

AbstractThe relationship between the Indian Ocean dipole (IOD) and the South Asian summer monsoon (SASM), which remains a subject of controversy, was investigated using data analyses and numerical experiments. We categorized IOD events according to their sea surface temperature anomaly (SSTA) pattern: Type-W and Type-E are associated with stronger SSTA amplitudes in the western and eastern poles of the IOD, respectively, while Type-C has comparable SSTA amplitudes in both poles during boreal autumn. Type-W is associated with a weak SASM from May to summer, which contributes to substantial warming of the western pole in autumn; the east–west SST gradient linked to the warming of the western pole causes weak southeasterly wind anomalies off Sumatra and feeble and cold SSTAs in the eastern pole during the mature phase. Type-E is associated with a strong SASM and feeble warming of the western pole; interaction between the strong SASM and cold SSTAs in the eastern pole in summer results in strong southeasterly wind anomalies off Sumatra and substantial cooling of the eastern pole during the mature phase. For Type-C, warming of the western pole and cooling of the eastern pole develop synchronously without apparent SASM anomalies, and reach comparable intensities during the mature phase. Observations and numerical simulation results both indicate the role of disparate SASM anomalies in modulating SSTA patterns during the development of positive IODs. Warming of the tropical Indian Ocean becomes established in the winter and spring following Type-W and Type-C IODs, but not following Type-E events.

scholarly journals Improved Simulation of the South Asian Summer Monsoon in a Coupled GCM with a More Realistic Ocean Mixed Layer

2012 ◽  
Vol 69 (5) ◽  
pp. 1681-1690 ◽  
Author(s):  
Yajuan Song ◽  
Fangli Qiao ◽  
Zhenya Song
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Summer Monsoon ◽  
Mixed Layer ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
Ocean Mixed Layer ◽  
Differential Heating ◽  
Asian Summer

Abstract Simulation and prediction of the South Asian summer monsoon in a climate model remain a challenge despite intense efforts by the atmosphere and ocean research community. Because the phenomenon arises from the interaction of the atmosphere with the upper ocean, a deficiency in the simulation of the latter can lead to a poor simulation of the atmospheric meridional circulation. This study demonstrates that a significant improvement can be obtained in the simulation of the summer monsoon by correcting a prevailing deficiency in the mixed layer simulation of the Indian Ocean. A particular physical process of the nonbreaking wave–ocean mixing parameterized as Bυ, which has not been considered in any climate model, is included in this study to enhance the vertical mixing in the upper ocean. Results show that the inclusion of this mixing process in a climate model leads to a better simulation of the ocean mixed layer, especially in the regions where the mixing was previously underestimated. The improved mixed layer simulation further results in stronger meridional differential heating, which drives stronger low-level monsoonal winds and results in stronger moisture transport and convergence, especially in the northern Indian Ocean. Moisture convergence into the Bay of Bengal is significantly enhanced and in general the spatial distribution of moisture is more consistent with observations. The directly driven monsoonal winds by the differential heating are further amplified by the resultant latent heating, which generates not only a wind amplitude comparable to the observations but also a correct vertical structure.

scholarly journals Tracing the origin of the South Asian summer monsoon precipitation and its variability using a novel Lagrangian framework

2021 ◽  
pp. 1-40
Author(s):  
Dipanjan Dey ◽  
Kristofer Döös
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Monsoon Precipitation ◽  
South Asian Summer Monsoon ◽  
The South ◽  
South Indian Ocean ◽  
South Indian ◽  
Asian Summer

AbstractThe water sources and their variability responsible for the South Asian summer monsoon precipitation were analyzed using Lagrangian atmospheric water-mass trajectories. The results indicated that evaporated waters from the Central and South Indian Ocean are the major contributors to the South Asian summer monsoon rainfall, followed by the contribution from the local recycling (precipitated water that evapotranspirated from the South Asian landmass), the Arabian Sea, remote sources and the Bay of Bengal. It was also found that although the direct contribution originating from the Bay of Bengal is small, it still provides a pathway for the atmospheric water that come from other regions. This pathway is hence only crossing over the Bay of Bengal. The outcomes further revealed that the evaporated waters originating from the Central and South Indian Ocean are responsible for the net precipitation over the coastal regions of the Ganges-Brahmaputra-Meghna Delta, Northeast India, Myanmar, the foothills of the Himalayas and Central-East India. Evaporated waters from the Arabian sea are mainly contributing to the rainfall over the Western coast and West-Central India. Summer monsoon precipitation due to the local recycling is primarily restricted to the Indo-Gangetic plain. No recycled precipitation was observed over the mountain chain along the West coast of India (Western Ghats). The month-to-month precipitation variation over South Asia was analysed to be linked with the Somali Low Level jet variability. The inter-annual variability of the South Asian summer monsoon precipitation was found to be mainly controlled by the atmospheric waters that were sourced and travelled from the Central and South Indian Ocean.

scholarly journals Differences in The Causes of Light And Extreme Precipitation For The Qaidam Basin In Summer

2021 ◽  
Author(s):  
Yan Li ◽  
Chunyan Lv ◽  
Jun Chen ◽  
Juan Feng ◽  
Qingyi Yang
Keyword(s):  
Heat Source ◽  
South Asian ◽  
Summer Monsoon ◽  
Extreme Precipitation ◽  
Moisture Transport ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
Extreme Precipitation Events ◽  
Asian Summer ◽  
Precipitation Events

Abstract The Qaidam Basin (QB) locates over the northeast of the Tibetan Plateau (TP), where precipitation especially extreme precipitation possesses obvious local characteristics compared with that over the whole TP. This study tries to investigate cause of light (50% threshold) and extreme (95% threshold) precipitation in boreal summer in the QB, which is helpful to deepen understanding of the mechanism of precipitation formation in different regions of the TP. The extreme (light) precipitation thresholds in the eastern QB are greater than that in the western QB, with a value of 6~16mm (2mm) for most regions. There are two main moisture transport channels for light and extreme precipitation events. One is from the Eurasia and carried by the westerlies, which provides 48.2% and 55.8% of moisture for light and extreme precipitation events, respectively. The other moisture transport channel is from the Arabian Sea and the Bay of Bengal, which is transported toward the QB at the joint role of the South Asian summer monsoon and the plateau monsoon, contributing 51.8% and 44.2% of moisture for light and extreme precipitation events, respectively. The stronger moisture transport to precipitation mostly attributes to the enhanced moisture influxes from the western and southern boundaries. Additionally, the weaker moisture outflux across the eastern boundary is also responsible for the extreme precipitation. The circulation characteristics shows that, the precipitation in the QB has a closely relationship with the weak ridge over the Caspian Sea and Aral Sea, the enhanced South Asian summer monsoon and plateau monsoon, which are conducive to the moisture transport from the Eurasia and low-latitudes toward the QB. The meridional circulation enhances, meantime the westerly jet stream splits into east- and west-branch, and the south Asian high (SAH) strengthens, which are beneficial for the stronger convective motion. Especially, the trough in the northwest of the QB and the more significant east- and west-branch structure of westerly jet are the main circulation characteristics for the extreme precipitation events. Further analysis reveals that the apparent heat source over the QB is contributed to more synchronous moisture transport around the TP and its surrounding areas for light precipitation events, while the apparent heat source enhances 1 day prior to moisture transport from the east part region of the South Asian summer monsoon to around the eastern TP for extreme precipitation events. Meantime, the apparent heat source triggers an abnormal cyclone over the TP which can positively strength the local convective motion. Such abnormal configuration of atmospheric circulation and the influence of apparent heat source can explain the difference in cause of precipitation with different magnitude to a great extent in the QB.

scholarly journals Sources of errors in the simulation of south Asian summer monsoon in the CMIP5 GCMs

2016 ◽  
Vol 49 (1-2) ◽  
pp. 193-223 ◽  
Author(s):  
Moetasim Ashfaq ◽  
Deeksha Rastogi ◽  
Rui Mei ◽  
Danielle Touma ◽  
L. Ruby Leung
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
Asian Summer ◽  
Cmip5 Gcms

scholarly journals Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: A test for future predictions

2021 ◽  
Vol 7 (23) ◽  
pp. eabg3848
Author(s):  
Steven C. Clemens ◽  
Masanobu Yamamoto ◽  
Kaustubh Thirumalai ◽  
Liviu Giosan ◽  
Julie N. Richey ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
South Asian ◽  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Precipitation Amount ◽  
Monsoon Precipitation ◽  
Orbital Eccentricity ◽  
South Asian Summer Monsoon ◽  
Asian Summer

South Asian precipitation amount and extreme variability are predicted to increase due to thermodynamic effects of increased 21st-century greenhouse gases, accompanied by an increased supply of moisture from the southern hemisphere Indian Ocean. We reconstructed South Asian summer monsoon precipitation and runoff into the Bay of Bengal to assess the extent to which these factors also operated in the Pleistocene, a time of large-scale natural changes in carbon dioxide and ice volume. South Asian precipitation and runoff are strongly coherent with, and lag, atmospheric carbon dioxide changes at Earth’s orbital eccentricity, obliquity, and precession bands and are closely tied to cross-equatorial wind strength at the precession band. We find that the projected monsoon response to ongoing, rapid high-latitude ice melt and rising carbon dioxide levels is fully consistent with dynamics of the past 0.9 million years.

Sign in / Sign up

Export Citation Format

Share Document