The Joint Aerosol–Monsoon Experiment: A New Challenge for Monsoon Climate Research

Lau, K. M.; Ramanathan, V.; Li, Z.; Tsay, Si Chee; Hsu, Christina; Sikka, R.; Holben, B. N.; Lü, Daren; Tartari, Gianni; Chin, Mian; Koudelova, Petra; Chen, H.; Ma, Yingtao; Huang, Jianping; Taniguchi, Kenji; Zhang, Renjian

doi:10.1175/bams-89-3-369

Cited by 259 publications

(207 citation statements)

References 31 publications

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“…Aerosols can also influence the hydrological cycle by altering the mechanisms that form precipitation in clouds (Ferek et al 2000;Rosenfeld 2000). Aerosols may have a substantial influence on the Asian monsoon circulation (Ramanathan et al 2005;Lau et al 2008): absorbing aerosols over the Indo-Gangetic plain near the foothills of the Himalayas act as an extra heat source aloft, enhancing the incipient monsoon circulation (Lau and Kim 2006). The same aerosols lead to a surface cooling over central India, shifting rainfall to the Himalayan region.…”

Section: Aerosol Loadingmentioning

confidence: 99%

A safe operating space for humanity

Rockström

Steffen

Noone

et al. 2009

Nature

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The article presents a study that investigates on the importance of identifying and quantifying planetary boundaries to prevent human activities in affecting environmental condition. The author states the industrial revolution and advancement in human civilization has caused the unstability of the environmental state that is less conducive for humans to live and affect their health condition. The author notes that planetary boundaries served a control variables to secure the safety of its citizen as well as protect the environment from shifting to dangerous levels. It also cites the different planetary boundaries, along with its impact on climate change and Earth system degradation

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Section: Aerosol Loadingmentioning

confidence: 99%

A safe operating space for humanity

Rockström

Steffen

Noone

et al. 2009

Nature

9,415

5,320

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“…We also use aerosol loading information from the space borne Moderate Resolution Imaging Spectroradiometer (MODIS) instrument over both vegetated as well as arid regions (Hsu et al, 2004;Levy et al, 2007). Aerosol vertical distribution information is obtained from the CloudAerosol Lidar with Orthogonal Polarization (CALIOP) instrument that provides global vertically-resolved measurements of aerosol and clouds in the atmosphere (Winker et al, 2003).…”

Section: Datamentioning

confidence: 99%

Aerosol and rainfall variability over the Indian monsoon region: distributions, trends and coupling

et al. 2009

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Abstract. Aerosol solar absorption over the Indian monsoon region has a potential role of modulating the monsoon circulation and rainfall distribution as suggested by recent studies based on model simulations. Prior to the onset of the monsoon, northern India is influenced by significant dust transport that constitutes the bulk of the regional aerosol loading over the Gangetic-Himalayan region. In this paper, a multi-sensor characterization of the increasing premonsoon aerosol loading over northern India, in terms of their spatial, temporal and vertical distribution is presented. Aerosol transport from the northwestern arid regions into the Indo-Gangetic Plains and over the foothills of the Himalayas is found to be vertically extended to elevated altitudes (up to 5 km) as observed from the space-borne lidar measurements (CALIPSO). In relation with the enhanced pre-monsoon aerosol loading and the associated solar absorption effects on tropospheric temperature anomalies, this paper investigates the monsoon rainfall variability over India in recent past decades from an observational viewpoint. It is found that the early summer monsoon rainfall over India is on the rise since 1950s, as indicated by historical rainfall data, with over 20% increase for the period 1950-2004. This large sustained increase in the early summer rainfall is led by the observed strengthening of the pre-monsoon tropospheric land-sea thermal gradient over the Indian monsoon region as indicated by microwave satellite measurements (MSU) of tropospheric temperatures from 1979-2007. Combined analysis of changes in tropospheric temperatures and summer monsoon rainfall in the past three decades, suggest a future possibility of an emerging rainfall pattern of a wetter monsoon over South Asia in early summer followed by a drier period.

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“…This potentially has a strong effect on the microphysics of orographic precipitation in this region by modulating the cloud condensation nuclei (CCN) spectrum (the so called indirect effect). Since both riming and collision of water droplets following coalescence is prerequisite for efficient precipitation (White et al, 2003;Lascaux et al, 2006;Rotunno and Houze, 2007), inhibition of this cloud microphysical process due to an increase in CCN concentration influences the precipitation efficiency of the system (Barros and Lettenmaier, 1994;Rosenfeld and Lensky, 1998;Khain et al, 2000;Ramanathan et al, 2001;Andreae et al, 2004;Tao et al, 2007;Lau et al, 2008;and many others). In order to study the aerosol indirect effect, a direct measurement of the CCN spectrum is required or, alternatively, it can be estimated from observed aerosol size distribution and chemical composition.…”

Section: P Shrestha Et Al: Pre-monsoon Aerosol Properties In Centramentioning

confidence: 99%

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

2010

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Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May-June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14-340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and watersoluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional periods of boundary layer growth and collapse. The increase in number concentration during the peak periods was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shalCorrespondence to: A. P. Barros (barros@duke.edu) low concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM 2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64-68%) of the aerosol concentration followed by ionic species (24-26%, mainly SO 2− 4 and NH + 4 ). Elemental Carbon (EC) compromised 7-10% of the total composition and 27% of OC was found to be water soluble at both sites. The day-to-day variability observed in the time series of aerosol composition could be explained by the synoptic scale haze that extended to the sampling region from the Indian Gangetic Plain (IGP), and rainfall occurrence. In the presence of regional scale haze during dry periods, the mean volume aerosol concentration was found to increase and so did the aerosol mass concentrations.

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The Joint Aerosol–Monsoon Experiment: A New Challenge for Monsoon Climate Research

Cited by 259 publications

References 31 publications

A safe operating space for humanity

A safe operating space for humanity

Aerosol and rainfall variability over the Indian monsoon region: distributions, trends and coupling

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

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