Mobile Lidar Profiling of Tropical Aerosols and Clouds

Abstract Lidar profiling of atmospheric aerosols and clouds in the lower atmosphere has been in progress at the Indian Institute of Tropical Meteorology (IITM), Pune (18°32′N, 73°52′E, 559 m MSL), India, for more than two decades. To enlarge the scope of these studies, an eye-safe new portable dual polarization micropulse lidar (DPMPL) has been developed and installed at this station. The system utilizes a diode-pumped solid-state (DPSS) neodymium–yttrium–aluminum–garnet (Nd:YAG) laser second harmonic, with either parallel polarization or alternate parallel and perpendicular polarization, as a transmitter and a Schmidt–Cassegrain telescope, with a high-speed detection and data acquisition and processing system, as a receiver. This online system in real-time mode provides backscatter intensity profiles up to about 75 km at every minute in both parallel and perpendicular polarization channels, corresponding to each state of polarization of the transmitted laser radiation. Thus, this versatile lidar system is expected to play a vital role not only in atmospheric aerosol and cloud physics research and environmental monitoring but also in weather and climate modeling studies of the impact of radiative forcing on the earth–atmosphere radiation balance and hydrological cycle. This paper provides a detailed description of Asia’s only lidar facility and presents initial observations of space–time variations of boundary layer structure from experiments carried out during winter 2005/06.

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Black carbon vertical profiles strongly affect its radiative forcing uncertainty

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-2423-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 2423-2434 ◽

Cited By ~ 157

Author(s):

B. H. Samset ◽

G. Myhre ◽

M. Schulz ◽

Y. Balkanski ◽

S. Bauer ◽

...

Keyword(s):

Black Carbon ◽

Vertical Profile ◽

Radiative Forcing ◽

Global Radiation ◽

Radiation Balance ◽

Upper Troposphere ◽

Aerosol Model ◽

Intercomparison Project ◽

To Come ◽

The Impact

Abstract. The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

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A novel methodology for large-scale daily assessment of the direct radiative forcing of smoke aerosols

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5471-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5471-5483 ◽

Cited By ~ 7

Author(s):

E. T. Sena ◽

P. Artaxo

Keyword(s):

Remote Sensing ◽

Spatial Distribution ◽

Radiative Transfer ◽

Biomass Burning ◽

Satellite Remote Sensing ◽

Radiative Forcing ◽

High Temporal Resolution ◽

Radiation Balance ◽

Direct Radiative Forcing ◽

The Impact

Abstract. A new methodology was developed for obtaining daily retrievals of the direct radiative forcing of aerosols (24h-DARF) at the top of the atmosphere (TOA) using satellite remote sensing. Simultaneous CERES (Clouds and Earth's Radiant Energy System) shortwave flux at the top of the atmosphere and MODIS (Moderate Resolution Spectroradiometer) aerosol optical depth (AOD) retrievals were used. To analyse the impact of forest smoke on the radiation balance, this methodology was applied over the Amazonia during the peak of the biomass burning season from 2000 to 2009. To assess the spatial distribution of the DARF, background smoke-free scenes were selected. The fluxes at the TOA under clean conditions (Fcl) were estimated as a function of the illumination geometry (θ0) for each 0.5° × 0.5° grid cell. The instantaneous DARF was obtained as the difference between the clean (Fcl (θ0)) and the polluted flux at the TOA measured by CERES in each cell (Fpol (θ0)). The radiative transfer code SBDART (Santa Barbara DISORT Radiative Transfer model) was used to expand instantaneous DARFs to 24 h averages. This new methodology was applied to assess the DARF both at high temporal resolution and over a large area in Amazonia. The spatial distribution shows that the mean 24h-DARF can be as high as −30 W m−2 over some regions. The temporal variability of the 24h-DARF along the biomass burning season was also studied and showed large intraseasonal and interannual variability. We showed that our methodology considerably reduces statistical sources of uncertainties in the estimate of the DARF, when compared to previous approaches. DARF assessments using the new methodology agree well with ground-based measurements and radiative transfer models. This demonstrates the robustness of the new proposed methodology for assessing the radiative forcing for biomass burning aerosols. To our knowledge, this is the first time that satellite remote sensing assessments of the DARF have been compared with ground-based DARF estimates.

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Investigation of radiative effects of the optically thick dust layer over the Indian tropical region

Annales Geophysicae ◽

10.5194/angeo-31-647-2013 ◽

2013 ◽

Vol 31 (4) ◽

pp. 647-663 ◽

Cited By ~ 9

Author(s):

S. K. Das ◽

J.-P. Chen ◽

M. Venkat Ratnam ◽

A. Jayaraman

Keyword(s):

Heating Rate ◽

Radiative Forcing ◽

Hydrological Cycle ◽

Southern India ◽

Lower Atmosphere ◽

Tropical Region ◽

Radiative Effects ◽

Heating Rates ◽

Dust Layer ◽

Aerosol Radiative Forcing

Abstract. Optical and physical properties of aerosols derived from multi-satellite observations (MODIS-Aqua, OMI-Aura, MISR-Terra, CALIOP-CALIPSO) have been used to estimate radiative effects of the dust layer over southern India. The vertical distribution of aerosol radiative forcing and heating rates are calculated with 100 m resolution in the lower atmosphere, using temperature and relative humidity data from balloon-borne radiosonde observations. The present study investigates the optically thick dust layer of optical thickness 0.18 ± 0.06 at an altitude of 2.5 ± 0.7 km over Gadanki, transported from the Thar Desert, producing radiative forcing and heating rate of 11.5 ± 3.3 W m−2 and 0.6 ± 0.26 K day−1, respectively, with a forcing efficiency of 43 W m−2 and an effective heating rate of 4 K day−1 per unit dust optical depth. Presence of the dust layer increases radiative forcing by 60% and heating rate by 60 times at that altitude compared to non-dusty cloud-free days. Calculation shows that the radiative effects of the dust layer strongly depend on the boundary layer aerosol type and mass loading. An increase of 25% of heating by the dust layer is found over relatively cleaner regions than urban regions in southern India and further 15% of heating increases over the marine region. Such heating differences in free troposphere may have significant consequences in the atmospheric circulation and hydrological cycle over the tropical Indian region.

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Rapid cloud removal of dimethyl sulfide oxidation products limits SO2 and cloud condensation nuclei production in the marine atmosphere

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2110472118 ◽

2021 ◽

Vol 118 (42) ◽

pp. e2110472118

Author(s):

Gordon A. Novak ◽

Charles H. Fite ◽

Christopher D. Holmes ◽

Patrick R. Veres ◽

J. Andrew Neuman ◽

...

Keyword(s):

Radiative Forcing ◽

Dimethyl Sulfide ◽

Cloud Condensation Nuclei ◽

Sulfide Oxidation ◽

Radiation Balance ◽

Marine Atmosphere ◽

Condensation Nuclei ◽

Near Surface ◽

Loss Process ◽

The Impact

Oceans emit large quantities of dimethyl sulfide (DMS) to the marine atmosphere. The oxidation of DMS leads to the formation and growth of cloud condensation nuclei (CCN) with consequent effects on Earth’s radiation balance and climate. The quantitative assessment of the impact of DMS emissions on CCN concentrations necessitates a detailed description of the oxidation of DMS in the presence of existing aerosol particles and clouds. In the unpolluted marine atmosphere, DMS is efficiently oxidized to hydroperoxymethyl thioformate (HPMTF), a stable intermediate in the chemical trajectory toward sulfur dioxide (SO2) and ultimately sulfate aerosol. Using direct airborne flux measurements, we demonstrate that the irreversible loss of HPMTF to clouds in the marine boundary layer determines the HPMTF lifetime (τHPMTF < 2 h) and terminates DMS oxidation to SO2. When accounting for HPMTF cloud loss in a global chemical transport model, we show that SO2 production from DMS is reduced by 35% globally and near-surface (0 to 3 km) SO2 concentrations over the ocean are lowered by 24%. This large, previously unconsidered loss process for volatile sulfur accelerates the timescale for the conversion of DMS to sulfate while limiting new particle formation in the marine atmosphere and changing the dynamics of aerosol growth. This loss process potentially reduces the spatial scale over which DMS emissions contribute to aerosol production and growth and weakens the link between DMS emission and marine CCN production with subsequent implications for cloud formation, radiative forcing, and climate.

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The key role of aerosol-radiation-interactions on cloud formation and precipitation in the Amazon

10.5194/egusphere-egu21-15593 ◽

2021 ◽

Author(s):

Lixia Liu ◽

Yafang Cheng ◽

Siwen Wang ◽

Chao Wei ◽

Mira Pöhlker ◽

...

Keyword(s):

Energy Balance ◽

Radiative Forcing ◽

Amazon Basin ◽

Hydrological Cycle ◽

Global Climate ◽

Cloud Formation ◽

Emission Rates ◽

Liquid Water Path ◽

Aerosol Loading ◽

The Impact

Biomass burning (BB) aerosols can influence regional and global climate through interactions with radiation, clouds, and precipitation. Here, we investigate the impact of BB aerosols on the energy balance and hydrological cycle over the Amazon Basin during the dry season. We performed WRF-Chem simulations for a range of different BB emission scenarios to explore and characterize nonlinear effects and individual contributions from aerosol&#8211;radiation interactions (ARIs) and aerosol&#8211;cloud interactions (ACIs). For scenarios representing the lower and upper limits of BB emission estimates for recent years (2002&#8211;2016), we obtained total regional BB aerosol radiative forcings of -0.2 and 1.5Wm-2, respectively, showing that the influence of BB aerosols on the regional energy balance can range from modest cooling to strong warming. We find that ACIs dominate at low BB emission rates and low aerosol optical depth (AOD), leading to an increased cloud liquid water path (LWP) and negative radiative forcing, whereas ARIs dominate at high BB emission rates and high AOD, leading to a reduction of LWP and positive radiative forcing. In all scenarios, BB aerosols led to a decrease in the frequency of occurrence and rate of precipitation, caused primarily by ACI effects at low aerosol loading and by ARI effects at high aerosol loading. Overall, our results show that ACIs tend to saturate at high aerosol loading, whereas the strength of ARIs continues to increase and plays a more important role in highly polluted episodes and regions. This should hold not only for BB aerosols over the Amazon, but also for other light-absorbing aerosols such as fossil fuel combustion aerosols in industrialized and densely populated areas. The importance of ARIs at high aerosol loading highlights the need for accurately characterizing aerosol optical properties in the investigation of aerosol effects on clouds, precipitation, and climate.

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Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

10.5194/hess-2016-551 ◽

2016 ◽

Author(s):

Felix N. Matt ◽

John F. Burkhart ◽

Joni-Pekka Pietikäinen

Keyword(s):

Radiative Forcing ◽

Hydrological Cycle ◽

Wave Radiation ◽

Maximum Effect ◽

Effect Estimate ◽

Model Parameters ◽

Snow Melt ◽

Catchment Scale ◽

Temporal Shift ◽

The Impact

Abstract. Light absorbing impurities in snow and ice (LAISI) originating from atmospheric deposition enhance the snow melt by increasing the absorption of short wave radiation. The consequences are a shortening of the snow duration due to increased snow melt and, on a catchment scale, a temporal shift in the discharge generation during the spring melt season. In this study, we present a newly developed snow algorithm for application in hydrolgical models that allows for an additional class of input variables: the deposition rate of various species of light absorbing aerosols. To show the sensitivity of different model parameters, we first use the model as 1-D point model forced with representative synthetic data and investigate the impact of parameters and variables specific to the algorithm determining the effect of LAISI. We then demonstrate the significance of the additional forcing by simulating black carbon deposited on snow of a remote south Norwegian catchment over a six years period, from September 2006 to August 2012. Our simulations suggest a significant impact of BC in snow on the hydrological cycle, with an average increase in discharge of 2.5 %, 9.9 %, and 21.4 % for our minimum, central and maximum effect estimate, respectively, over a two months period during the spring melt season compared to simulations where radiative forcing from LAISI is turned off. The increase in discharge is followed by a decrease caused by melt limitation due to faster decrease of the catchment's snow covered fraction in the scenarios where radiative forcing from LAISI is applied. The central effect estimate produces reasonable surface BC concentrations in snow with a strong annual cycle, showing increasing surface BC concentration during spring melt as consequence of melt amplification. However, we further identify large uncertainties in the representation of the surface BC concentration and the subsequent consequences for the snowpack evolution.

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The impact threshold of the aerosol radiation forcing on the boundary layer structure in the pollution region

10.5194/acp-2020-553 ◽

2020 ◽

Author(s):

Dandan Zhao ◽

Jinyuan Xin ◽

Chongshui Gong ◽

Jiannong Quan ◽

Yuesi Wang ◽

...

Keyword(s):

Boundary Layer ◽

Radiative Forcing ◽

Layer Structure ◽

Atmospheric Environment ◽

Absolute Difference ◽

Air Pollution Control ◽

Aerosol Radiative Forcing ◽

Boundary Layer Structure ◽

Improvement Measures ◽

The Impact

Abstract. Recently, there has been increasing interest in the relation between particulate matter (PM) pollution and atmospheric boundary layer (ABL) structure. However, this has yet to be fully understood because most studies have been superficial. This study aimed to qualitatively assess the interaction between PM and ABL structure in essence, and to further quantitatively estimate the effects of aerosol radiative forcing (ARF) on the ABL structure. Multi-episode contrastive analysis stated the key to determining whether haze outbreak or dissipation was the ABL structure (i.e., stability and turbulence kinetic energy (TKE)) satisfied relevant conditions. However, it seemed that the ABL structure change was in turn highly related to the PM level and ARF. |SFC-ATM| (SFC and ATM is respectively the ARF at the surface and interior of the atmospheric column) is the absolute difference between ground and atmosphere layer ARFs, and the change in |SFC-ATM| is linearly related to the PM mass concentration. However, the influence of ARF on the boundary layer structure is nonlinear. With increasing |SFC-ATM|, the TKE level exponentially decreased, which was notable in the lower layers/ABL but disappeared above the ABL. Moreover, the threshold of the ARF effects on the ABL structure was determined for the first time, namely, once |SFC-ATM| exceeded ~ 55 W m−2, the ABL structure would quickly stabilize and would thereafter change little with increasing ARF. The threshold of the ARF effects on the boundary layer structure could provide useful information for relevant atmospheric environment improvement measures and policies, such as formulating the objectives of phased air pollution control.

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Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

Hydrology and Earth System Sciences ◽

10.5194/hess-22-179-2018 ◽

2018 ◽

Vol 22 (1) ◽

pp. 179-201 ◽

Cited By ~ 13

Author(s):

Felix N. Matt ◽

John F. Burkhart ◽

Joni-Pekka Pietikäinen

Keyword(s):

Radiative Forcing ◽

Hydrological Cycle ◽

Synthetic Data ◽

Aerosol Deposition ◽

Shortwave Radiation ◽

Model Parameters ◽

Catchment Scale ◽

Temporal Shift ◽

Mixing Ratios ◽

The Impact

Abstract. Light absorbing impurities in snow and ice (LAISI) originating from atmospheric deposition enhance snowmelt by increasing the absorption of shortwave radiation. The consequences are a shortening of the snow duration due to increased snowmelt and, at the catchment scale, a temporal shift in the discharge generation during the spring melt season. In this study, we present a newly developed snow algorithm for application in hydrological models that allows for an additional class of input variable: the deposition mass flux of various species of light absorbing aerosols. To show the sensitivity of different model parameters, we first use the model as a 1-D point model forced with representative synthetic data and investigate the impact of parameters and variables specific to the algorithm determining the effect of LAISI. We then demonstrate the significance of the radiative forcing by simulating the effect of black carbon (BC) deposited on snow of a remote southern Norwegian catchment over a 6-year period, from September 2006 to August 2012. Our simulations suggest a significant impact of BC in snow on the hydrological cycle. Results show an average increase in discharge of 2.5, 9.9, and 21.4 %, depending on the applied model scenario, over a 2-month period during the spring melt season compared to simulations where radiative forcing from LAISI is not considered. The increase in discharge is followed by a decrease in discharge due to a faster decrease in the catchment's snow-covered fraction and a trend towards earlier melt in the scenarios where radiative forcing from LAISI is applied. Using a reasonable estimate of critical model parameters, the model simulates realistic BC mixing ratios in surface snow with a strong annual cycle, showing increasing surface BC mixing ratios during spring melt as a consequence of melt amplification. However, we further identify large uncertainties in the representation of the surface BC mixing ratio during snowmelt and the subsequent consequences for the snowpack evolution.

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Influence of Dynamic and Thermal Forcing on the Meridional Transport of Taklimakan Desert Dust in Spring and Summer

Journal of Climate ◽

10.1175/jcli-d-18-0361.1 ◽

2019 ◽

Vol 32 (3) ◽

pp. 749-767 ◽

Cited By ~ 10

Author(s):

Tiangang Yuan ◽

Siyu Chen ◽

Jianping Huang ◽

Dongyou Wu ◽

Hui Lu ◽

...

Keyword(s):

East Asia ◽

Radiative Forcing ◽

Hydrological Cycle ◽

Tianshan Mountains ◽

Dust Particles ◽

Total Output ◽

Radiation Balance ◽

Taklimakan Desert ◽

The Tibetan Plateau ◽

Meridional Transport

The Weather Research and Forecasting Model coupled with chemistry (WRF-Chem) associated with in situ measurements and satellite retrievals was used to investigate the meridional transport of Taklimakan Desert (TD) dust, especially in summer. Both satellite observations and simulations reveal that TD dust particles accumulate over the Tibetan Plateau (TP) and the Tianshan Mountains in summer, resulting in higher dust concentration up to 85 μg m−3 here. The proportions of meridional transport of TD dust in summer increase up to 30% of the total output dust over the TD. Further, the impacts of thermal and dynamic forcing on the meridional transport of TD dust to the TP and Tianshan Mountains are investigated based on composite analysis and numerical modeling. It is found that the weakness of the westerly jet over East Asia significantly decreases the eastward transport of TD dust. More TD dust particles lifted to higher altitude reach up to 8 km induced by the enhanced sensible heating in summer. Under the influence of the northerly airflow over the TD regions, the TD dust particles are strengthened southward and transported to the northern slope of the TP through topographic forcing. Moreover, the cyclonic circulation raises dust particles to higher altitude over the TP. It can further intensify the TP heat source by direct radiative forcing of dust aerosols, which may have a positive feedback to the southward transport of TD dust. This research provides confidence for the investigation of the role of TP dust with regard to the radiation balance and hydrological cycle over East Asia.

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Comparison of climate response to marine cloud brightening and ocean albedo modification: A model study

10.5194/egusphere-egu21-1877 ◽

2021 ◽

Author(s):

Mengying Zhao ◽

Long Cao ◽

Lei Duan ◽

Govindasamy Bala ◽

Ken Caldeira

Keyword(s):

Global Warming ◽

Solar Radiation ◽

Land Surface ◽

Radiative Forcing ◽

Hydrological Cycle ◽

Lower Atmosphere ◽

Shortwave Radiation ◽

Climate Response ◽

Tropical Ocean ◽

Climate Effect

Solar radiation modification (SRM), an artificial intervention to reduce the amount of solar radiation reaching the surface, has been proposed as a potential option to ameliorate some undesired consequences of global warming. Marine cloud brightening (MCB) and ocean albedo modification (OAM) are two proposed SRM approaches. MCB aims to cool the planet by increasing marine cloud albedo that might be achieved by injecting sea salt into low marine cloud.&#160; OAM aims to cool the planet by increasing surface ocean albedo that might be achieved by using highly reflective microbubbles over ocean. There is speculation that climate effect of OAM and MCB would be similar as forcing is applied only over ocean in both cases.In this study, we use NCAR CESM model to compare climate response in &#160;these two SRM approaches under the framework of &#8220;fast versus slow response&#8221;. The term &#8220;fast&#8221; refers to climate adjustment that is associated with rapid adjustment of the atmosphere and land surface, and &#8220;slow&#8221; refers to climate feedbacks that are associated with the slow evolution of sea surface temperature.In our simulation we find that to offset global warming from a doubling of atmospheric CO2, OAM requires a stronger negative effective radiative forcing than that of MCB, indicating MCB is more effective in producing cooling per unit of radiative forcing. This is mainly associated with differing fast climate adjustment between OAM and MCB forcing. OAM increases upward shortwave radiation from surface and heats the lower atmosphere, causing low-level clouds to dissipate. A reduction in low cloudiness allows more solar radiation to reach the surface, partly offsetting the negative radiative forcing from increase in ocean albedo. At equilibrium state, however, OAM and MCB produces similar pattern of change in temperature and hydrological cycle, but prominent differences in climate response is observed over the tropical ocean where OAM produces larger reduction in precipitation and evaporation than that of MCB. Our results indicate that there is similarity between climate response to marine cloud brightening and ocean albedo increase, but caution should be exercised when using climate response from one to infer the other.&#160;

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