scholarly journals Asian monsoon projection with a new large-scale monsoon definition

2021 ◽  
Author(s):  
Xingang Dai ◽  
Yang Yang ◽  
Ping Wang
Keyword(s):  
South Asia ◽  
Summer Monsoon ◽  
Moisture Transport ◽  
Large Scale ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Northwest China ◽  
Winter Monsoon ◽  
Climate Simulation ◽  
Northwestern Part

Abstract This paper focuses on Asian monsoon projection with CMIP5 multi-model outputs. A large-scale monsoon herewith is defined as a vector field of vertically integrated moisture flux from the surface to 500 hPa. Results demonstrate that the model ensemble mean underestimated the summer monsoon and overestimated slightly the winter monsoon over South Asia in both CMIP5 historical climate simulation and the monsoon projection for 2006–2015. The major of the bias is the model climate drift (MCD), which is removed in the monsoon projection for 2016–2045 under scenarios RCP4.5 for reducing the uncertainty. The projection shows that two increased moisture flows northward appeared across the Equator of Indian Ocean, the first is nearby Somalia coast toward northwestern part of South Asia, leading to excess rainfall in where the wet jet could reach, and the second starts from the equatorial Sect. (80°E–100°E) toward northeastern Bay of Bengal, leading to more rainfall spreading over the northwestern coast of Indochina Peninsula. In addition, a westward monsoon flow is intensified over the Peninsula leading to local climate moisture transport belt shifted onto South China Sea, which would reduce moisture transport toward Southwest China on one hand, and transport more moisture onto the southeast coast of the China mainland. The anomalous monsoon would result in a dry climate in Northwest China and wet climate in the coast belt during summer monsoon season for the period. Besides, the Asian winter monsoon would be seemingly intensified slightly over South Asia, which would bring a dry winter climate to Indian subcontinent, Northwest China, but would be more rainfall in southeast part of Arabian Peninsula with global climate warming.

scholarly journals Asian Monsoon Projection With a New Large-Scale Monsoon Definition

2021 ◽  
Author(s):  
Xingang Dai ◽  
YANG Yang ◽  
WANG Ping
Keyword(s):  
South Asia ◽  
Summer Monsoon ◽  
Moisture Transport ◽  
Large Scale ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Northwest China ◽  
Winter Monsoon ◽  
Climate Simulation ◽  
Northwestern Part

Abstract This paper focuses on Asian monsoon projection with CMIP5 multi-model outputs. A large-scale monsoon herewith is defined as a vector field of vertically integrated moisture flux from the surface to 500 hPa. Results demonstrate that the model ensemble mean underestimated the summer monsoon and overestimated slightly the winter monsoon over South Asia in both CMIP5 historical climate simulation and the monsoon projection for 2006-2015. The major of the bias is the model climate drift (MCD), which is removed in the monsoon projection for 2016 -2045 under scenarios RCP4.5 for reducing the uncertainty. The projection shows that two increased moisture flows northward appeared across the Equator of Indian Ocean, the first is nearby Somalia coast toward northwestern part of South Asia, leading to excess rainfall in where the wet jet could reach, and the second starts from the equatorial section (80°E-100°E) toward northeastern Bay of Bengal, leading to more rainfall spreading over the northwestern coast of Indochina Peninsula. In addition, a westward monsoon flow is intensified over the Peninsula leading to local climate moisture transport belt shifted onto South China Sea, which would reduce moisture transport toward Southwest China on one hand, and transport more moisture onto the southeast coast of the China mainland. The anomalous monsoon would result in a dry climate in Northwest China and wet climate in the coast belt during summer monsoon season for the period. Besides, the Asian winter monsoon would be seemingly intensified slightly over South Asia, which would bring a dry winter climate to Indian subcontinent, Northwest China, but would be more rainfall in southeast part of Arabian peninsula with global climate warming.

Using a long-term climate simulation to address future changes in Western Europe precipitation regimes due to global warming

2020 ◽  
Author(s):  
Pedro M. Sousa ◽  
Alexandre M. Ramos ◽  
Ricardo M. Trigo ◽  
Christoph C. Raible ◽  
Martina Messmer ◽  
...  
Keyword(s):  
Global Warming ◽  
Moisture Transport ◽  
Large Scale ◽  
Western Europe ◽  
Warming Trend ◽  
Water Vapor Transport ◽  
Climate Simulation ◽  
Wet Season ◽  
Precipitation Regimes

<p>Moisture transport and Atmospheric Rivers (ARs) over the Northeastern Atlantic are a very relevant process for the inter-annual variability of precipitation over Western Europe. Based on a long-term transient simulation (850-2100CE) from the CESM model, we have showed that moisture transport towards Western Europe (using the vertically integrated horizontal water vapor transport, IVT) has been increasing significantly since pre-industrial period, in a clear association with the global warming trend. Both current and projected changes (using RCP 8.5) significantly exceed the range given by inter-annual to inter-decadal internal/external variability observed during the last millennium.</p><p>We have checked the emergence of the temperature, IVT and precipitation signals in Iberia and the UK, showing that while the first two have now clearly emerged from the pre-warming state, precipitation series are still slightly below that threshold. Nevertheless, projections clearly show an increase in rainfall at higher latitudes (i in phase with a warmer and moister atmosphere); and a decrease at lower latitudes decoupled from the overall increase in moisture availability. Additionally we have explored the role played by large-scale circulation and atmospheric dynamics for these contrasting projections. Overall, results show that a poleward migration of moisture corridors and ARs explain a significant fraction of these projected trends. Based on the Clausius–Clapeyron relation we have separated the thermodynamical from dynamical changes. We also show how that a significant increase in subtropical anticyclonic activity over Iberia is responsible for: i) dynamical circulation changes; ii) a shortening of the wet season; iii) to less efficient precipitation regimes in the region. These results highlight the urge to adapt to a drying trend in Mediterranean-type climates, as a consequence of Global Warming.</p><p> </p><p>The financial support for this work was possible through the following FCT project: HOLMODRIVE - North Atlantic Atmospheric Patterns influence on Western Iberia Climate: From the Lateglacial to the Present [PTDC/CTA-GEO/29029/2017]</p>

scholarly journals Lower tropospheric ozone over India and its linkage to the South Asian monsoon

2017 ◽  
Author(s):  
Xiao Lu ◽  
Lin Zhang ◽  
Xiong Liu ◽  
Meng Gao ◽  
Yuanhong Zhao ◽  
...  
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Tropospheric Ozone ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Meteorological Conditions ◽  
South Asian Monsoon ◽  
Summer Monsoon Season ◽  
The South

Abstract. Lower tropospheric (surface to 600 hPa) ozone over India poses serious risks to local human and crops, and potentially affects global ozone distribution through frequent deep convection in tropical regions. Our current understanding of processes controlling seasonal to long-term variations in lower tropospheric ozone over this region is rather limited due to spatially and temporally sparse observations. Here we present an integrated process analysis of the seasonal cycle, interannual variability, and long-term trends of lower tropospheric ozone over India and its linkage to the South Asian Monsoon using the Ozone Monitoring Instrument (OMI) satellite observations for years 2006–2014 interpreted with a global chemical transport model (GEOS-Chem) simulation for 1990–2010. OMI observed lower tropospheric ozone over India averaged for 2006–2010 show the highest concentrations (54.1 ppbv) in the pre-summer monsoon season (May) and the lowest concentrations (40.5 ppbv) in the summer monsoon season (August). Process analyses in GEOS-Chem show that hot and dry meteorological conditions and active biomass burning together contribute to 5.8 Tg more ozone produced in the lower troposphere of India in May than January. The onset of the summer monsoon brings ozone-unfavorable meteorological conditions and strong upward transport, all lead to large decreases in the lower tropospheric ozone burden. Interannually, we find that both OMI and GEOS-Chem indicate strong interannual positive correlations (r = 0.55–0.58) between ozone and surface temperature in pre-summer monsoon seasons, with larger correlations found in high NOx emission regions reflecting NOx-limited production conditions. Summer monsoon seasonal mean ozone levels are strongly controlled by monsoon strengths. Lower ozone concentrations are found in stronger monsoon seasons mainly due to less ozone net chemical production. Furthermore, model simulations over 1990–2010 estimate a mean annual trend of 0.19 ± 0.07 (p-value 

scholarly journals Characteristics of a persistent "pool of inhibited cloudiness" and its genesis over the Bay of Bengal associated with the Asian summer monsoon

2011 ◽  
Vol 29 (7) ◽  
pp. 1247-1252 ◽  
Author(s):  
Anish Kumar M. Nair ◽  
K. Rajeev ◽  
S. Sijikumar ◽  
S. Meenu
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Surface Wind ◽  
Spatial Gradient ◽  
Dynamical Response ◽  
Monsoon Circulation ◽  
Asian Summer

Abstract. Using spatial and vertical distributions of clouds derived from multi-year spaceborne observations, this paper presents the characteristics of a significant "pool of inhibited cloudiness" covering an area of >106 km2 between 3–13° N and 77–90° E over the Bay of Bengal (BoB), persisting throughout the Asian summer monsoon season (ASM). Seasonal mean precipitation rate over the "pool" is <3 mm day−1 while that over the surrounding regions is mostly in the range of 6–14 mm day−1. Frequency of occurrence of clouds in this "pool" is ~20–40 % less than that over the surrounding deep convective regions. Zonal and meridional cross sections of the altitude distribution of clouds derived from CloudSat data reveal a vault-like structure at the "pool" with little cloudiness below ~7 km, indicating that this "pool" is almost fully contributed by the substantially reduced or near-absence of low- and middle-level clouds. This suggest the absence of convection in the "pool" region. Spaceborne scatterometer observations show divergence of surface wind at the "pool" and convergence at its surroundings, suggesting the existence of a mini-circulation embedded in the large-scale monsoon circulation. Reanalysis data shows a mini-circulation extending between the surface and ~3 km altitude, but its spatial structure does not match well with that inferred from the above observations. Sea surface at the south BoB during ASM is sufficiently warm to trigger convection, but is inhibited by the subsidence associated with the mini-circulation, resulting in the "pool". This mini-circulation might be a dynamical response of the atmosphere to the substantial spatial gradient of latent heating by large-scale cloudiness and precipitation at the vast and geographically fixed convective zones surrounding the "pool". Subsidence at the "pool" might contribute to the maintenance of convection at the above zones and be an important component of ASM that is overlooked hitherto.

Coupling of South and East Asian Monsoon Precipitation in July–August*

2015 ◽  
Vol 28 (11) ◽  
pp. 4330-4356 ◽  
Author(s):  
Jesse A. Day ◽  
Inez Fung ◽  
Camille Risi
Keyword(s):  
East Asia ◽  
South Asia ◽  
Bay Of Bengal ◽  
Moisture Transport ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Southern China ◽  
East Asian ◽  
Monsoon Circulation ◽  
Yunnan Plateau

Abstract The concept of the “Asian monsoon” masks the existence of two separate summer rainfall régimes: convective storms over India, Bangladesh, and Nepal (the South Asian monsoon) and frontal rainfall over China, Japan, and the Korean Peninsula (the East Asian monsoon). In addition, the Himalayas and other orography, including the Arakan Mountains, Ghats, and Yunnan Plateau, create smaller precipitation domains with abrupt boundaries. A mode of continental precipitation variability is identified that spans both South and East Asia during July and August. Point-to-point correlations and EOF analysis with Asian Precipitation–Highly-Resolved Observational Data Integration Toward Evaluation of the Water Resources (APHRODITE), a 57-yr rain gauge record, show that a dipole between the Himalayan foothills (+) and the “monsoon zone” (central India, −) dominates July–August interannual variability in South Asia, and is also associated in East Asia with a tripole between the Yangtze corridor (+) and northern and southern China (−). July–August storm tracks, as shown by lag–lead correlation of rainfall, remain mostly constant between years and do not explain this mode. Instead, it is proposed that interannual change in the strength of moisture transport from the Bay of Bengal to the Yangtze corridor across the northern Yunnan Plateau induces widespread precipitation anomalies. Abundant moisture transport along this route requires both cyclonic monsoon circulation over India and a sufficiently warm Bay of Bengal, which coincide only in July and August. Preliminary results from the LMDZ version 5 (LMDZ5) model, run with a zoomed grid over Asia and circulation nudged toward the ECMWF reanalysis, support this hypothesis. Improved understanding of this coupling may help to project twenty-first-century precipitation changes in East and South Asia, home to over three billion people.

scholarly journals Penultimate deglaciation Asian monsoon response to North Atlantic circulation collapse

2021 ◽  
Author(s):  
Jasper A. Wassenburg ◽  
Hubert B. Vonhof ◽  
Hai Cheng ◽  
Alfredo Martínez-García ◽  
Pia-Rebecca Ebner ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
North Atlantic ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Isotope Effects ◽  
Meridional Overturning Circulation ◽  
The North ◽  
Kinetic Isotope ◽  
Monsoon System ◽  
Meridional Overturning

AbstractDuring glacial terminations, massive iceberg discharges and meltwater pulses in the North Atlantic triggered a shutdown of the Atlantic Meridional Overturning Circulation (AMOC). Speleothem calcium carbonate oxygen isotope records (δ18OCc) indicate that the collapse of the AMOC caused dramatic changes in the distribution and variability of the East Asian and Indian monsoon rainfall. However, the mechanisms linking changes in the intensity of the AMOC and Asian monsoon δ18OCc are not fully understood. Part of the challenge arises from the fact that speleothem δ18OCc depends on not only the δ18O of precipitation but also temperature and kinetic isotope effects. Here we quantitatively deconvolve these parameters affecting δ18OCc by applying three geochemical techniques in speleothems covering the penultimate glacial termination. Our data suggest that the weakening of the AMOC during meltwater pulse 2A caused substantial cooling in East Asia and a shortening of the summer monsoon season, whereas the collapse of the AMOC during meltwater pulse 2B (133,000 years ago) also caused a dramatic decrease in the intensity of the Indian summer monsoon. These results reveal that the different modes of the AMOC produced distinct impacts on the monsoon system.

scholarly journals Impact of solar variability on the frequency variability of the Indian summer monsoon

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 67-82
Author(s):  
J. R. KULKARNI ◽  
M. MUJUMDAR ◽  
S. P. GHARGE ◽  
V. SATYAN ◽  
G. B. PANT
Keyword(s):  
Time Series ◽  
Summer Monsoon ◽  
Solar Irradiance ◽  
General Circulation ◽  
Large Scale ◽  
Monsoon Season ◽  
Circulation Model ◽  
Solar Constant ◽  
Good Correspondence ◽  
The Impact

Earlier investigations into the epochal behavior of fluctuations in All India Summer Monsoon Rainfall (AISMR) have indicated the existence of a Low Frequency Mode (LFM) in the 60-70 years range. One of the probable sources of this variability may be due to changes in solar irradiance. To investigate this, time series of 128-year solar irradiance data from 1871-1998 has been examined. The Wavelet Transform (WT) method is applied to extract the LFM from these time series, which show a very good correspondence. A case study has been carried out to test the sensitivity of AISMR to solar irradiance. The General Circulation Model (GCM) of the Center of Ocean-Land-Atmosphere (COLA) has been integrated in the control run (using the climatological value of solar constant i.e., 1365 Wm-2) and in the enhanced solar constant condition (enhanced by 10 Wm-2) for summer monsoon season of 1986. The study shows that the large scale atmospheric circulation over the Indian region, in the enhanced solar constant scenario is favorable to good monsoon activity. A conceptual model for the impact of solar irradiance on the AISMR at LFM is also suggested.

scholarly journals Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006

2008 ◽  
Vol 26 (9) ◽  
pp. 2569-2595 ◽  
Author(s):  
S. Janicot ◽  
C. D. Thorncroft ◽  
A. Ali ◽  
N. Asencio ◽  
G. Berry ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Land Surface ◽  
Large Scale ◽  
Monsoon Season ◽  
Regional Scale ◽  
West African ◽  
Future Research ◽  
Atmospheric Conditions ◽  
African Monsoon ◽  
Continental Hydrology

Abstract. The AMMA (African Monsoon Multidisciplinary Analysis) program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas.

scholarly journals Widespread air pollutants of the North China Plain during the Asian summer monsoon season: A case study

2018 ◽  
Author(s):  
Jiarui Wu ◽  
Naifang Bei ◽  
Xia Li ◽  
Junji Cao ◽  
Tian Feng ◽  
...  
Keyword(s):  
Air Quality ◽  
Summer Monsoon ◽  
North China Plain ◽  
North China ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Northwest China ◽  
Summer Monsoon Season ◽  
The North ◽  
Asian Summer

Abstract. During the Asian summer monsoon season, prevailing southeasterly – southwesterly winds are subject to delivering air pollutants from the North China Plain (NCP) to the Northeast and Northwest China. In the present study, the WRF-CHEM model is used to evaluate contributions of trans-boundary transport of the NCP emissions to the air quality in the Northeast and Northwest China during a persistent air pollution episode from 22 to 28 May 2015. The WRF-CHEM model generally performs well in capturing the observed temporal variation and spatial distribution of fine particulate matters (PM2.5), ozone (O3), and NO2. The simulated temporal variation of aerosol species is also in good agreement with measurements in Beijing during the episode. Model simulations show that the NCP emissions contribute substantially to the PM2.5 level in Liaoning and Shanxi provinces, the adjacent downwind areas of the NCP, with an average of 24.2 and 13.9 μg m−3 during the episode, respectively. The PM2.5 contributions in Jilin and Shaanxi provinces are also appreciable, with an average of 9.6 and 6.5 μg m−3, respectively. The NCP emissions contribute remarkably to the O3 level in Liaoning province, with an average of 46.5 μg m−3, varying from 23.9 to 69.5 μg m−3. The O3 level in Shanxi province is also influenced considerably by the NCP emissions, with an average contribution of 35.1 μg m−3. The average O3 contributions of the NCP emissions to Jilin and Shaanxi provinces are 28.7 and 20.7 μg m−3, respectively. The effect of the NCP emissions on the air quality in Inner Mongolia is generally insignificant however. Therefore, effective mitigations of the NCP emissions not only improve the local air quality, but also are beneficial to the air quality in the Northeast and Northwest China during the Asian summer monsoon season.

scholarly journals Lower tropospheric ozone over India and its linkage to the South Asian monsoon

2018 ◽  
Vol 18 (5) ◽  
pp. 3101-3118 ◽  
Author(s):  
Xiao Lu ◽  
Lin Zhang ◽  
Xiong Liu ◽  
Meng Gao ◽  
Yuanhong Zhao ◽  
...  
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Tropospheric Ozone ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Meteorological Conditions ◽  
South Asian Monsoon ◽  
Summer Monsoon Season ◽  
The South

Abstract. Lower tropospheric (surface to 600 hPa) ozone over India poses serious risks to both human health and crops, and potentially affects global ozone distribution through frequent deep convection in tropical regions. Our current understanding of the processes controlling seasonal and long-term variations in lower tropospheric ozone over this region is rather limited due to spatially and temporally sparse observations. Here we present an integrated process analysis of the seasonal cycle, interannual variability, and long-term trends of lower tropospheric ozone over India and its linkage to the South Asian monsoon using the Ozone Monitoring Instrument (OMI) satellite observations for years 2006–2014 interpreted with a global chemical transport model (GEOS-Chem) simulation for 1990–2010. OMI observed lower tropospheric ozone over India averaged for 2006–2010, showing the highest concentrations (54.1 ppbv) in the pre-summer monsoon season (May) and the lowest concentrations (40.5 ppbv) in the summer monsoon season (August). Process analyses in GEOS-Chem show that hot and dry meteorological conditions and active biomass burning together contribute to 5.8 Tg more ozone being produced in the lower troposphere in India in May than January. The onset of the summer monsoon brings ozone-unfavorable meteorological conditions and strong upward transport, which all lead to large decreases in the lower tropospheric ozone burden. Interannually, we find that both OMI and GEOS-Chem indicate strong positive correlations (r=0.55–0.58) between ozone and surface temperature in pre-summer monsoon seasons, with larger correlations found in high NOx emission regions reflecting NOx-limited production conditions. Summer monsoon seasonal mean ozone levels are strongly controlled by monsoon strengths. Lower ozone concentrations are found in stronger monsoon seasons mainly due to less ozone net chemical production. Furthermore, model simulations over 1990–2010 estimate a mean annual trend of 0.19 ± 0.07 (p value < 0.01) ppbv yr−1 in Indian lower tropospheric ozone over this period, which are mainly driven by increases in anthropogenic emissions with a small contribution (about 7 %) from global methane concentration increases.

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