Influence of Indian Summer Monsoon on Aerosol Loading in East Asia

Abstract The spatial and temporal variations of aerosol loading over eastern Asia specified in terms of the aerosol optical depth (AOD) at the 550-nm wavelength during July are examined in conjunction with the intensity of the Indian summer monsoon. AOD derived from Moderate Resolution Imaging Spectroradiometer (MODIS) observations, gridded reanalyses, and ground-based measurements are used in the analysis. Two contrasting years, 2002 and 2003, which represent weak and active Indian summer monsoon events, respectively, are selected for the study, with a focus on an eastern Asian southern subregion (SR; 23°–32°N, 105°–120°E) and an eastern Asian northern subregion (NR; 35°–44°N, 115°–130°E). It is shown that the interannual variation of July mean wind intensity is a major factor in regulating the midsummer spatial pattern of aerosols over eastern Asia when the Indian monsoon index is anomalously large. The AOD anomalies in the NR and SR are positive and negative, respectively, during an active monsoon year, whereas the opposite is observed during a weak monsoon year. The variation patterns of less cloudy-day visibility, observed at four meteorological stations in the SR and NR subregions, also show spatial–temporal aerosol variability evident in the MODIS AOD data. Relative to the case of a weak monsoon year, meridional winds and convection are stronger and more clouds and precipitation are observed in the NR subregion during the active monsoon year. The opposite pattern is observed in the SR subregion. The spatial–temporal variation pattern of aerosols over eastern Asia illustrates the nonnegligible role of transport and dispersal mechanisms associated with the Indian summer monsoon in the region.

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CCN characteristics during the Indian Summer Monsoon over a rain-shadow region

10.5194/acp-2020-45 ◽

2020 ◽

Author(s):

Venugopalan Nair Jayachandran ◽

Mercy Varghese ◽

Palani Murugavel ◽

Kiran S. Todekar ◽

Shivdas P. Bankar ◽

...

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Monsoon Season ◽

Cloud Condensation Nuclei ◽

Geometric Mean ◽

Empirical Relationship ◽

Shadow Region ◽

Air Mass ◽

Aerosol Loading ◽

Marine Air

Abstract. Continuous aerosol and Cloud Condensation Nuclei (CCN) measurements carried out at the ground observational facility situated in the rain-shadow region of the Indian sub-continent are illustrated. These observations were part of the Cloud-Aerosol Interaction Precipitation Enhancement EXperiment (CAIPEEX) during the Indian Summer Monsoon season (June to September) of 2018. Observations are classified as dry-continental (monsoon break) and wet-marine (monsoon active) according to air mass history. CCN concentrations measured for a range of supersaturations (0.2–1.2 %) are parameterized using Twomey's empirical relationship. CCN concentrations even at low (0.2 %) supersaturation (SS) were high (> 1,000 cm-3) during continental conditions associated with high black carbon (BC~2,000 ng m-3) and columnar aerosol loading. During the marine air mass conditions, CCN concentrations diminished to ~ 350 cm-3 at 0.3 % SS and low aerosol loading persisted (BC~900 ng m-3). High CCN activation fraction (AF) of ~ 0.55 (at 0.3 % SS) were observed before the monsoon rainfall, which reduced to ~ 0.15 during the monsoon and enhanced to ~ 0.32 after that. Mostly mono-modal aerosol number-size distribution (NSD) with a mean geometric mean diameter (GMD) of ~ 85 nm, with least (~ 9 %) contribution from nucleation mode (

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A long-term observational analysis of aerosol-cloud-rainfall associations over Indian Summer Monsoon region

10.5194/acp-2016-947 ◽

2016 ◽

Author(s):

Chandan Sarangi ◽

Sachchida Nand Tripathi ◽

Vijay P. Kanawade ◽

Ilan Koren ◽

D. Sivanand Pai

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Satellite Observations ◽

Monsoon Region ◽

Cloud Systems ◽

Aerosol Cloud ◽

Aerosol Loading ◽

Surface Rainfall ◽

Summer Monsoon Region ◽

Ice Phase

Abstract. Monsoonal rainfall is the primary source of surface water in India. Using 12 years of in-situ and satellite observations, we examined association of aerosol loading with cloud fraction, cloud top pressure, cloud top temperature, and daily surface rainfall over Indian summer monsoon region (ISMR). The analyses showed positive correlations between aerosol loading and cloud properties as well as rainfall. A decrease in outgoing longwave radiation and increase in reflected shortwave radiation at the top of the atmosphere with an increase in aerosol loading further supported a seminal role of aerosols on cloud systems. Significant perturbation in liquid- and ice-phase microphysics was also evident over ISMR. For the polluted cases, delay in the onset of collision-coalescence processes and enhancement in the condensation efficiency, allows for more condensate mass to be lifted up to the mixed-colder phases. This results in the higher mass concentration of bigger sized ice-phase hydrometeors and, therefore, implies that the delayed rain processes eventually lead to more surface rainfall. Numerical simulation of a typical rainfall event case over ISMR using spectral bin microphysical scheme coupled with Weather Research Forecasting (WRF-SBM) model was also performed. Simulated microphysics also illustrated the initial suppression of warm rain coupled with increase in updraft velocity under high aerosol loading leads to enhanced super-cooled liquid droplets above freezing level and ice-phase hydrometeors, resulting in increased accumulated surface rainfall. Thus, both observational and numerical analysis suggest that high aerosol loading may induce cloud invigoration and thereby increasing surface rainfall over the ISMR. While the meteorological variability influence the strength of the observed positive associations, our results suggest that the persistent aerosol-associated deepening of cloud systems and intensification of surface rain amounts was applicable to all the meteorological sub-regimes over the ISMR. Hence, we believe that these results provide a step forward in our ability to address aerosol-cloud-rainfall associations based on satellite observations over ISMR.

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Investigation of the aerosol–cloud–rainfall association over the Indian summer monsoon region

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-5185-2017 ◽

2017 ◽

Vol 17 (8) ◽

pp. 5185-5204 ◽

Cited By ~ 26

Author(s):

Chandan Sarangi ◽

Sachchida Nand Tripathi ◽

Vijay P. Kanawade ◽

Ilan Koren ◽

D. Sivanand Pai

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Satellite Observations ◽

Monsoon Region ◽

Cloud Systems ◽

Aerosol Cloud ◽

Aerosol Loading ◽

Surface Rainfall ◽

Summer Monsoon Region ◽

Ice Phase

Abstract. Monsoonal rainfall is the primary source of surface water in India. Using 12 years of in situ and satellite observations, we examined the association of aerosol loading with cloud fraction, cloud top pressure, cloud top temperature, and daily surface rainfall over the Indian summer monsoon region (ISMR). Our results showed positive correlations between aerosol loading and cloud properties as well as rainfall. A decrease in outgoing longwave radiation and an increase in reflected shortwave radiation at the top of the atmosphere with an increase in aerosol loading further indicates a possible seminal role of aerosols in the deepening of cloud systems. Significant perturbation in liquid- and ice-phase microphysics was also evident over the ISMR. For the polluted cases, delay in the onset of collision–coalescence processes and an enhancement in the condensation efficiency allows for more condensate mass to be lifted up to the mixed colder phases. This results in the higher mass concentration of larger-sized ice-phase hydrometeors and, therefore, implies that the delayed rain processes eventually lead to more surface rainfall. A numerical simulation of a typical rainfall event case over the ISMR using a spectral bin microphysical scheme coupled with the Weather Research Forecasting (WRF-SBM) model was also performed. Simulated microphysics also illustrated that the initial suppression of warm rain coupled with an increase in updraft velocity under high aerosol loading leads to enhanced super-cooled liquid droplets above freezing level and ice-phase hydrometeors, resulting in increased accumulated surface rainfall. Thus, both observational and numerical analysis suggest that high aerosol loading may induce cloud invigoration, thereby increasing surface rainfall over the ISMR. While the meteorological variability influences the strength of the observed positive association, our results suggest that the persistent aerosol-associated deepening of cloud systems and an intensification of surface rain amounts was applicable to all the meteorological sub-regimes over the ISMR. Hence, we believe that these results provide a step forward in our ability to address aerosol–cloud–rainfall associations based on satellite observations over the ISMR.

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On the spatio-temporal variations of the tropopause height over india and indian summer monsoon activity

Advances in Atmospheric Sciences ◽

10.1007/bf02656973 ◽

1993 ◽

Vol 10 (4) ◽

pp. 481-488 ◽

Cited By ~ 3

Author(s):

J. R. Kulkarni ◽

R. K. Verma

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Temporal Variations ◽

Tropopause Height ◽

Spatio Temporal

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Spatial and temporal variations of wave energy in the nearshore waters of the central west coast of India

Annales Geophysicae ◽

10.5194/angeo-34-1197-2016 ◽

2016 ◽

Vol 34 (12) ◽

pp. 1197-1208 ◽

Cited By ~ 3

Author(s):

M. M. Amrutha ◽

V. Sanil Kumar

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Water Depth ◽

Wave Energy ◽

West Coast ◽

Temporal Variations ◽

Wave Power ◽

Monsoon Period ◽

West Coast Of India ◽

Water Depths

Abstract. Assessment of wave power potential at different water depths and time is required for identifying a wave power plant location. This study examines the variation in wave power off the central west coast of India at water depths of 30, 9 and 5 m based on waverider buoy measured wave data. The study shows a significant reduction ( ∼  10 to 27 %) in wave power at 9 m water depth compared to 30 m and the wave power available at 5 m water depth is 20 to 23 % less than that at 9 m. At 9 m depth, the seasonal mean value of the wave power varied from 1.6 kW m−1 in the post-monsoon period (ONDJ) to 15.2 kW m−1 in the Indian summer monsoon (JJAS) period. During the Indian summer monsoon period, the variation of wave power in a day is up to 32 kW m−1. At 9 m water depth, the mean annual wave power is 6 kW m−1 and interannual variations up to 19.3 % are observed during 2009–2014. High wave energy ( >  20 kW m−1) at the study area is essentially from the directional sector 245–270° and also 75 % of the total annual wave energy is from this narrow directional sector, which is advantageous while aligning the wave energy converter.

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Perceptible changes in Indian summer monsoon rainfall in relation to Indian Monsoon Index

Global and Planetary Change ◽

10.1016/j.gloplacha.2017.08.016 ◽

2017 ◽

Vol 157 ◽

pp. 83-92 ◽

Cited By ~ 4

Author(s):

C.V. Naidu ◽

A. Dharma Raju ◽

P. Vinay Kumar ◽

G.Ch. Satyanarayana

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Monsoon Rainfall ◽

Indian Monsoon ◽

Indian Summer Monsoon Rainfall ◽

Summer Monsoon Rainfall ◽

Monsoon Index

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Impact of Northward-Propagating Intraseasonal Variability on the Onset of Indian Summer Monsoon

Journal of Climate ◽

10.1175/jcli-d-13-00214.1 ◽

2014 ◽

Vol 27 (1) ◽

pp. 126-139 ◽

Cited By ~ 32

Author(s):

Lei Zhou ◽

Raghu Murtugudde

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Large Scale ◽

Southern Oscillation ◽

Indian Subcontinent ◽

Intraseasonal Variability ◽

Monsoon Index ◽

Process Understanding ◽

Simple Regression Model ◽

Predictive Understanding

Abstract The onset of the Indian summer monsoon (ISM) has a pronounced interannual variability, part of which originates from the large-scale circulation and its thermodynamic properties. While the northward-propagating intraseasonal variabilities (ISVs) are a prominent characteristic of the ISM, they tend to initiate an early onset by transferring moisture and momentum from the deep tropics to the Indian subcontinent. However, not all early onsets of ISM are attributable to strong ISVs and not all strong ISVs can lead to early ISM onsets. With a daily Indian monsoon index and a simple regression model, the onsets of ISM from 1982 to 2011 are separated into two groups. The years in which the early onsets of ISM are closely related to the northward-propagating ISVs are categorized as the ISVO years, and the other years in which the ISM onsets are not closely related to ISVs are categorized as non-ISVO years. The former category is the focus of this study. Before the onset of ISM in the ISVO years, the convective features are prominent, such as a cyclone over the Bay of Bengal (BoB) and the associated strong convection. The ocean–atmosphere interaction is found to be important for the northward-propagating ISVs before the ISM onset in the ISVO years. Evidence shows that warm SST anomalies drive the atmosphere and lead to atmospheric instability and convection. This reinforces the more recent view that the ocean does not just play a passive role in the northward-propagating ISVs. This process understanding helps shape the path to enhancing predictive understanding and monsoon prediction skills with obvious implications for the prediction of El Niño–Southern Oscillation.

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