Author
Rakesh K. Hooda
Other affiliations: The Energy and Resources Institute
Bio: Rakesh K. Hooda is an academic researcher from Finnish Meteorological Institute. The author has contributed to research in topics: Aerosol & Snow. The author has an hindex of 15, co-authored 30 publications receiving 750 citations. Previous affiliations of Rakesh K. Hooda include The Energy and Resources Institute.
Topics: Aerosol, Snow, Mineral dust, Monsoon, Environmental science
Papers
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Leibniz Association1, European Space Agency2, Finnish Meteorological Institute3, National University of Ireland, Galway4, University of Hertfordshire5, Stockholm University6, National Institute of Environmental Research7, University of Warsaw8, Aristotle University of Thessaloniki9, Leipzig University10, The Energy and Resources Institute11, Deutscher Wetterdienst12, University of Leeds13, University of São Paulo14, Federal University of São Paulo15, North-West University16, Stellenbosch University17, Sun Yat-sen University18, Cyprus University of Technology19, University of Magallanes20
TL;DR: PollyNET as mentioned in this paper consists of portable, remote-controlled multiwavelength-polarization-Raman lidars (Polly) for automated and continuous 24/7 observations of clouds and aerosols.
Abstract: . A global vertically resolved aerosol data set covering more than 10 years of observations at more than 20 measurement sites distributed from 63° N to 52° S and 72° W to 124° E has been achieved within the Raman and polarization lidar network PollyNET. This network consists of portable, remote-controlled multiwavelength-polarization-Raman lidars (Polly) for automated and continuous 24/7 observations of clouds and aerosols. PollyNET is an independent, voluntary, and scientific network. All Polly lidars feature a standardized instrument design with different capabilities ranging from single wavelength to multiwavelength systems, and now apply unified calibration, quality control, and data analysis. The observations are processed in near-real time without manual intervention, and are presented online at http://polly.tropos.de/ . The paper gives an overview of the observations on four continents and two research vessels obtained with eight Polly systems. The specific aerosol types at these locations (mineral dust, smoke, dust-smoke and other dusty mixtures, urban haze, and volcanic ash) are identified by their Angstrom exponent, lidar ratio, and depolarization ratio. The vertical aerosol distribution at the PollyNET locations is discussed on the basis of more than 55 000 automatically retrieved 30 min particle backscatter coefficient profiles at 532 nm as this operating wavelength is available for all Polly lidar systems. A seasonal analysis of measurements at selected sites revealed typical and extraordinary aerosol conditions as well as seasonal differences. These studies show the potential of PollyNET to support the establishment of a global aerosol climatology that covers the entire troposphere.
192 citations
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University of Helsinki1, University of Eastern Finland2, Finnish Meteorological Institute3, Paul Scherrer Institute4, University of Birmingham5, North-West University6, Texas A&M University7, Nanjing University8, King Abdulaziz University9, Netherlands Organisation for Applied Scientific Research10, The Energy and Resources Institute11, Peking University12, University of Tartu13, Stockholm University14, Lund University15, University of Crete16, Eötvös Loránd University17, National University of Ireland, Galway18, University of Auvergne19, Leibniz Association20, Beijing University of Chemical Technology21
TL;DR: In this paper, the authors investigated the frequency of atmospheric new particle formation, formation rates of 10-nm particles, and growth rates in the size range of 10−25nm using at least 1 year of aerosol number size distribution observations at 36 different locations around the world.
Abstract: . Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10–25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March–May (on about 30 % of the days) and least frequently in December–February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01–10 cm−3 s−1) and the growth rate by about an order of magnitude (1–10 nm h−1). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.
108 citations
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TL;DR: In this article, the authors show correction methods for an artifact found to affect the instrument accuracy in environments characterized by high black carbon concentrations, which is caused by erroneous dark counts in the photodetector measuring the transmitted light, in combination with an instrument internal averaging procedure of the raw signals.
Abstract: . The Multi-Angle Absorption Photometer (MAAP) is a widely-used instrument for aerosol black carbon (BC) measurements. In this paper, we show correction methods for an artifact found to affect the instrument accuracy in environments characterized by high black carbon concentrations. The artifact occurs after a filter spot change – as BC mass is accumulated on a fresh filter spot, the attenuation of the light (raw signal) is weaker than anticipated. This causes a sudden decrease, followed by a gradual increase in measured BC concentration. The artifact is present in the data when the BC concentration exceeds ~3 μg m−3 at the typical MAAP flow rate of 16.7 L min−1 or 1 m3 h−1. The artifact is caused by erroneous dark counts in the photodetector measuring the transmitted light, in combination with an instrument internal averaging procedure of the photodetector raw signals. It was found that, in addition to the erroneous temporal response of the data, concentrations higher than 9 μg m−3 (at the flow rate of 16.7 L min−1) are underestimated by the MAAP. The underestimation increases with increasing BC accumulation rate. At a flow rate of 16.7 L min−1 and concentration of about 24 μg m−3 (BC accumulation rate ~0.4 μg min−1), the underestimation is about 30%. There are two ways of overcoming the MAAP artifact. One method is by logging the raw signal of the 165° photomultiplier measuring the reflected light from the filter spot. As this signal is not affected by the artifact, it can be converted to approximately correct absorption and BC values. However, as the typical print formats of the MAAP do not give the reflected signal as an output, a semi-empirical correction method was developed based on laboratory experiments to correct for the results in the post-processing phase. The correction function was applied to three MAAP datasets from Gual Pahari (India), Beijing (China), and Welgegund (South Africa). In Beijing, the results could also be compared against a photoacoustic spectrometer (PAS). The correction improved the quality of all three MAAP datasets substantially, even though the individual instruments operated at different flow rates and in different environments.
84 citations
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TL;DR: One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analyzed as discussed by the authors.
Abstract: . One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analysed. The data was split into four seasons: spring (March–May), summer (June–August), autumn (September–November) and winter (December–February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1–3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm−1 sr−1 and 142 Mm−1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared to other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Angstrom exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.
62 citations
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University of Grenoble1, National Research Council2, University of Auvergne3, Cooperative Institute for Research in Environmental Sciences4, National Oceanic and Atmospheric Administration5, Norwegian Institute for Air Research6, MeteoSwiss7, Norwegian Meteorological Institute8, Spanish National Research Council9, Seoul National University10, University of Puerto Rico, Río Piedras11, Commonwealth Scientific and Industrial Research Organisation12, Lund University13, University of Granada14, Higher University of San Andrés15, Bulgarian Academy of Sciences16, Finnish Meteorological Institute17, Paul Scherrer Institute18, Environment Agency19, University of Basel20, Australian National Drag Racing Association21, Cooperative Institute for Research in the Atmosphere22, University of Utah23, Swiss Federal Laboratories for Materials Science and Technology24, The Energy and Resources Institute25, Stockholm University26, South African Weather Service27, National Central University28, Virginia Tech College of Natural Resources and Environment29, Université Paris-Saclay30, University of Toulouse31, International Agency for Research on Cancer32, National Park Service33, Environment Canada34, Appalachian State University35, International Trademark Association36, University of La Réunion37, University of Bern38
TL;DR: In this article, the authors provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmospheric Watch network.
Abstract: . Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and
absorbing solar radiation, and indirectly by acting as cloud condensation
nuclei. In contrast to most greenhouse gases, aerosol particles have short
atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at
regional scale through observations involving, in particular, the in situ
near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant
in situ aerosol properties (namely wavelength dependent particle light
scattering and absorption coefficients, particle number concentration and
particle number size distribution) from all sites connected to the Global
Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported
for a reference year in 2017, providing a very extended and robust view of
the variability of these variables worldwide. The range of variability
observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with
model simulation for the different stations. The scope of the present paper
is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of
the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in
the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate
monitoring system.
61 citations
Cited by
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TL;DR: In this paper, an inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment, in which emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia.
Abstract: [i] An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO 2 , 26.8 Tg NO x , 9870 Tg CO 2 , 279 Tg CO, 107 Tg CH 4 , 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH 3 . In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE-P and ACE-Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO 2 , 11.4 Tg NO x , 3820 Tg CO 2 , 116 Tg CO, 38.4 Tg CH 4 , 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH 3 . Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s x 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE-P and ACE-Asia data interpretation. During the observation period of March/ April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO 2 to a high of ±450% for OC.
1,828 citations
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TL;DR: A copy of the Guangbo jiemu bao [Broadcast Program Report] was being passed from hand to hand among a group of young people eager to be the first to read the article introducing the program "What Is Revolutionary Love?".
Abstract: A copy of Guangbo jiemu bao [Broadcast Program Report] was being passed from hand to hand among a group of young people eager to be the first to read the article introducing the program "What Is Revolutionary Love?" It said: "… Young friends, you are certainly very concerned about this problem'. So, we would like you to meet the young women workers Meng Xiaoyu and Meng Yamei and the older cadre Miss Feng. They are the three leading characters in the short story ‘The Place of Love.’ Through the description of the love lives of these three, the story induces us to think deeply about two questions that merit further examination.
1,528 citations
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TL;DR: In this article, the authors present a recommended terminology to clarify the terms used for black carbon in atmospheric research, with the goal of establishing unambiguous links between terms, targeted material properties and associated measurement techniques.
Abstract: . Although black carbon (BC) is one of the key atmospheric particulate components driving climate change and air quality, there is no agreement on the terminology that considers all aspects of specific properties, definitions, measurement methods, and related uncertainties. As a result, there is much ambiguity in the scientific literature of measurements and numerical models that refer to BC with different names and based on different properties of the particles, with no clear definition of the terms. The authors present here a recommended terminology to clarify the terms used for BC in atmospheric research, with the goal of establishing unambiguous links between terms, targeted material properties and associated measurement techniques.
817 citations
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TL;DR: The Global Atmosphere 3.0 (GA3.0) as mentioned in this paper is a configuration of the Met Office Unified Model (MetUM) developed for use across climate research and weather prediction activities.
Abstract: . We describe Global Atmosphere 3.0 (GA3.0): a configuration of the Met Office Unified Model (MetUM) developed for use across climate research and weather prediction activities. GA3.0 has been formulated by converging the development paths of the Met Office's weather and climate global atmospheric model components such that wherever possible, atmospheric processes are modelled or parametrized seamlessly across spatial resolutions and timescales. This unified development process will provide the Met Office and its collaborators with regular releases of a configuration that has been evaluated, and can hence be applied, over a variety of modelling regimes. We also describe Global Land 3.0 (GL3.0): a configuration of the JULES community land surface model developed for use with GA3.0. This paper provides a comprehensive technical and scientific description of the GA3.0 and GL3.0 (and related GA3.1 and GL3.1) configurations and presents the results of some initial evaluations of their performance in various applications. It is to be the first in a series of papers describing each subsequent Global Atmosphere release; this will provide a single source of reference for established users and developers as well as researchers requiring access to a current, but trusted, global MetUM setup.
803 citations
01 Apr 2012
TL;DR: This article used a series of climate model experiments to investigate the South Asian monsoon response to natural and anthropogenic forcings, and found that the observed precipitation decrease can be attributed mainly to human-influenced aerosol emissions.
Abstract: Changes in monsoon rainfall are caused by human-produced aerosols slowing the tropical atmospheric circulation. Observations show that South Asia underwent a widespread summertime drying during the second half of the 20th century, but it is unclear whether this trend was due to natural variations or human activities. We used a series of climate model experiments to investigate the South Asian monsoon response to natural and anthropogenic forcings. We find that the observed precipitation decrease can be attributed mainly to human-influenced aerosol emissions. The drying is a robust outcome of a slowdown of the tropical meridional overturning circulation, which compensates for the aerosol-induced energy imbalance between the Northern and Southern Hemispheres. These results provide compelling evidence of the prominent role of aerosols in shaping regional climate change over South Asia.
752 citations