The Distribution of Deep Convection over Ocean and Land during the Asian Summer Monsoon

Abstract. Low ozone and high water vapour mixing ratios are common features in the Asian summer monsoon (ASM) anticyclone; however, low ozone and low water vapour values were observed near the tropopause over Kunming, China, within the ASM using balloon-borne measurements performed during the SWOP (sounding water vapour, ozone, and particle) campaign in August 2009 and 2015. Here, we investigate low ozone and water vapour signatures in the upper troposphere and lower stratosphere (UTLS) using FengYun-2D, FengYun-2G, and Aura Microwave Limb Sounder (MLS) satellite measurements and backward trajectory calculations. Trajectories with kinematic and diabatic vertical velocities were calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) trajectory module driven by both ERA-Interim and ERA5 reanalysis data. All trajectory calculations show that air parcels with low ozone and low water vapour values in the UTLS over Kunming measured by balloon-borne instruments originate from the western Pacific boundary layer. Deep convection associated with tropical cyclones over the western Pacific transports ozone-poor air from the marine boundary layer to the cold tropopause region. Subsequently, these air parcels are mixed into the strong easterlies on the southern side of the Asian summer monsoon anticyclone. Air parcels are dehydrated when passing the lowest temperature region (< 190 K) at the convective outflow of tropical cyclones. However, trajectory calculations show different vertical transport via deep convection depending on the employed reanalysis data (ERA-Interim, ERA5) and vertical velocities (diabatic, kinematic). Both the kinematic and the diabatic trajectory calculations using ERA5 data show much faster and stronger vertical transport than ERA-Interim primarily because of ERA5's better spatial and temporal resolution, which likely resolves convective events more accurately. Our findings show that the interplay between the ASM anticyclone and tropical cyclones has a significant impact on the chemical composition of the UTLS during summer.

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Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport

Science ◽

10.1126/science.1219371 ◽

2012 ◽

Vol 337 (6090) ◽

pp. 78-81 ◽

Cited By ~ 164

Author(s):

Adam E. Bourassa ◽

Alan Robock ◽

William J. Randel ◽

Terry Deshler ◽

Landon A. Rieger ◽

...

Keyword(s):

Sulfur Dioxide ◽

Summer Monsoon ◽

Asian Monsoon ◽

Lower Stratosphere ◽

Asian Summer Monsoon ◽

Deep Convection ◽

Volcanic Eruptions ◽

Volcanic Aerosol ◽

Upper Troposphere ◽

Asian Summer

The Nabro stratovolcano in Eritrea, northeastern Africa, erupted on 13 June 2011, injecting approximately 1.3 teragrams of sulfur dioxide (SO2) to altitudes of 9 to 14 kilometers in the upper troposphere, which resulted in a large aerosol enhancement in the stratosphere. The SO2 was lofted into the lower stratosphere by deep convection and the circulation associated with the Asian summer monsoon while gradually converting to sulfate aerosol. This demonstrates that to affect climate, volcanic eruptions need not be strong enough to inject sulfur directly to the stratosphere.

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Impact of Stochastic Entrainment in the NCAR CAM Deep Convection Parameterization on the Simulation of South Asian Summer Monsoon

Climate Dynamics ◽

10.1007/s00382-021-05870-1 ◽

2021 ◽

Author(s):

Raju Pathak ◽

Sandeep Sahany ◽

Saroj Kanta Mishra

Keyword(s):

South Asian ◽

Summer Monsoon ◽

Asian Summer Monsoon ◽

Deep Convection ◽

South Asian Summer Monsoon ◽

Asian Summer ◽

Convection Parameterization

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Seasonality of the Structure and Propagation Characteristics of the MJO

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-15-0232.1 ◽

2016 ◽

Vol 73 (9) ◽

pp. 3511-3526 ◽

Cited By ~ 33

Author(s):

Ángel F. Adames ◽

John M. Wallace ◽

Joy M. Monteiro

Keyword(s):

Summer Monsoon ◽

Asian Summer Monsoon ◽

Deep Convection ◽

Winter Season ◽

Water Model ◽

Boreal Winter ◽

Northwest Pacific ◽

Monsoon Period ◽

Asian Summer ◽

Frictional Convergence

Abstract The seasonality of the Madden–Julian oscillation (MJO) is documented in observational data, and a nonlinear shallow-water model is used to help interpret some of the contrasts in MJO structure between the boreal winter season [November–March (NDJFM)] and the Asian summer monsoon period [June–September (JJAS)]. At upper-tropospheric levels, the flanking Rossby waves remain centered around 28°N/S year-round, but they tend to be stronger in the winter hemisphere, where the climatological-mean jet stream is stronger, rendering the subtropical circulation more sensitive to forcing by a near-equatorial heat source. Amplitudes of the MJO-related deep convection and lower-tropospheric zonal wind are stronger in the summer hemisphere, where the column-integrated water vapor is larger. During NDJFM, the equatorial asymmetry is subtle: as in the annual mean, moisture convergence into swallowtail-shaped regions of enhanced deep convection is an integral part of the equatorial Rossby wave signature, and the eastward propagation is due to moistening of the air to the east of the enhanced convection by poleward moisture advection. During the Asian summer monsoon in JJAS, the convection assumes the form of northward-propagating, west-northwest–east-southeast-oriented rainbands embedded within cyclonic shear lines. These features are maintained by frictional convergence of moisture, and their northward propagation is mainly due to the presence of features in the climatological-mean fields: that is, the west–east moisture gradient over India and the Arabian Sea and the southwesterly low-level monsoon flow over the northwest Pacific.

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A PV-based determination of the transport barrier in the Asian summer monsoon anticyclone

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-10593-2015 ◽

2015 ◽

Vol 15 (7) ◽

pp. 10593-10628 ◽

Cited By ~ 3

Author(s):

F. Ploeger ◽

C. Gottschling ◽

S. Griessbach ◽

J.-U. Grooß ◽

G. Günther ◽

...

Keyword(s):

Summer Monsoon ◽

Large Scale ◽

Lower Stratosphere ◽

Transport Model ◽

Asian Summer Monsoon ◽

Deep Convection ◽

Polar Vortex ◽

Time Averaging ◽

Transport Barrier ◽

Asian Summer

Abstract. The Asian summer monsoon provides an important pathway of tropospheric source gases and pollution into the lower stratosphere. This transport is characterized by deep convection and steady upwelling, combined with confinement inside a large-scale anticyclonic circulation in the upper troposphere and lower stratosphere (UTLS). In this paper, we show that a barrier to horizontal transport along the 380 K isentrope in the monsoon anticyclone can be determined from the potential vorticity (PV) field, following the polar vortex criterion by Nash et al. (1996). Due to large dynamic variability of the anticyclone, the corresponding maximum in the PV gradient is weak and additional constraints are needed (e.g., time averaging). Notwithstanding, PV contours in the monsoon anticyclone agree well with contours of trace gas mixing ratios (CO, O3) and mean age from model simulations with a Lagrangian chemistry transport model (CLaMS) and MLS satellite observations. Hence, the PV-based transport barrier reflects the separation between air inside the anticyclone core and the background atmosphere well. For the summer season 2011 we find an average PV value of 3.6 PVU for the transport barrier in the anticyclone on the 380 K isentrope.

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Enhancement of aerosols in UTLS over the Tibetan Plateau induced by deep convection during the Asian summer monsoon

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-3169-2014 ◽

2014 ◽

Vol 14 (2) ◽

pp. 3169-3191 ◽

Cited By ~ 1

Author(s):

Q. S. He ◽

C. C. Li ◽

J. Z. Ma ◽

H. Q. Wang ◽

X. L. Yan ◽

...

Keyword(s):

Tibetan Plateau ◽

Summer Monsoon ◽

Asian Summer Monsoon ◽

Deep Convection ◽

Temporal Variations ◽

Aerosol Layer ◽

The Tibetan Plateau ◽

Aerosol Extinction ◽

Extinction Coefficients ◽

Asian Summer

Abstract. Vertical profiles of aerosol extinction coefficients were measured by an Micro Pulse Lidar at Naqu (31.5° N, 92.1° E, 4508 m a.m.s.l.), a meteorological station located on the central part of the Tibetan Plateau during summer 2011. Observations show a persistent maximum in aerosol extinction coefficients in the upper troposphere–lower stratosphere (UTLS) within an anticyclone during the Asian summer monsoon. These aerosol layers were generally located at an altitude of 18–19 km m.s.l., 1–2 km higher than the tropopause, with broad layer depth ranging approximately 3–4 km. Variations in these aerosols are found to be closely related to the intensity of underlying deep convection. Efficient vertical transport resulting from the most intensive convection is considered to be most important for the enhancement of aerosols observed near the tropopause. Temporal variations in aerosol layer in UTLS over the Plateau show a significant peak at midnight. This further indicates that deep convection plays an important role in the accumulation of aerosols in UTLS over the Tibetan Plateau.

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Sensitivity of South Asian summer monsoon simulation to land surface schemes in WRF

International Journal of Climatology ◽

10.1002/joc.7278 ◽

2021 ◽

Author(s):

Sha Lu ◽

Hongchao Zuo

Keyword(s):

South Asian ◽

Summer Monsoon ◽

Land Surface ◽

Asian Summer Monsoon ◽

South Asian Summer Monsoon ◽

Asian Summer

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Skilful predictions of the Asian summer monsoon one year ahead

Nature Communications ◽

10.1038/s41467-021-22299-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yuhei Takaya ◽

Yu Kosaka ◽

Masahiro Watanabe ◽

Shuhei Maeda

Keyword(s):

Long Range ◽

Summer Monsoon ◽

Southern Oscillation ◽

Asian Summer Monsoon ◽

Boreal Summer ◽

Climate Modelling ◽

Large Ensemble ◽

Asian Society ◽

Asian Summer ◽

One Year

AbstractThe interannual variability of the Asian summer monsoon has significant impacts on Asian society. Advances in climate modelling have enabled us to make useful predictions of the seasonal Asian summer monsoon up to approximately half a year ahead, but long-range predictions remain challenging. Here, using a 52-member large ensemble hindcast experiment spanning 1980–2016, we show that a state-of-the-art climate model can predict the Asian summer monsoon and associated summer tropical cyclone activity more than one year ahead. The key to this long-range prediction is successfully simulating El Niño-Southern Oscillation evolution and realistically representing the subsequent atmosphere–ocean response in the Indian Ocean–western North Pacific in the second boreal summer of the prediction. A large ensemble size is also important for achieving a useful prediction skill, with a margin for further improvement by an even larger ensemble.

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