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Author: Ana Barros
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 0
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Book Description
In mountainous regions, the nonlinear thermodynamics of orographic land-atmosphere interactions (LATMI) in organizing and maintaining moisture convergence patterns on the one hand, and aerosol-cloud-precipitation interactions (ACPI) in modulating the vertical structure of precipitation and space-time variability of surface precipitation on the other, are difficult to separate unambiguously because the physiochemical characteristics of aerosols themselves exhibit large sub-regional scale variability. In this chapter, ACPI in the Central Himalayas are examined in detail using aerosol observations during JAMEX09 (Joint Aerosol Monsoon Campaign 2009) to specify CCN activation properties for simulations of a premonsoon convective storm using the Weather Research and Forecasting (WRF) version 3.8.1. The focus is on contrasting AIE during episodes of remote pollution run-up from the Indo-Gangetic Plains and when only local aerosols are present in Central Nepal. This study suggests strong coupling between the vertical structure of convection in complex terrain that governs the time-scales and spatial organization of cloud development, CCN activation rates, and cold microphysics (e.g. graupel production is favored by slower activation spectra) that result in large shifts in the spatial distribution of precipitation, precipitation intensity and storm arrival time.
Author: Ana Barros
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 0
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Book Description
In mountainous regions, the nonlinear thermodynamics of orographic land-atmosphere interactions (LATMI) in organizing and maintaining moisture convergence patterns on the one hand, and aerosol-cloud-precipitation interactions (ACPI) in modulating the vertical structure of precipitation and space-time variability of surface precipitation on the other, are difficult to separate unambiguously because the physiochemical characteristics of aerosols themselves exhibit large sub-regional scale variability. In this chapter, ACPI in the Central Himalayas are examined in detail using aerosol observations during JAMEX09 (Joint Aerosol Monsoon Campaign 2009) to specify CCN activation properties for simulations of a premonsoon convective storm using the Weather Research and Forecasting (WRF) version 3.8.1. The focus is on contrasting AIE during episodes of remote pollution run-up from the Indo-Gangetic Plains and when only local aerosols are present in Central Nepal. This study suggests strong coupling between the vertical structure of convection in complex terrain that governs the time-scales and spatial organization of cloud development, CCN activation rates, and cold microphysics (e.g. graupel production is favored by slower activation spectra) that result in large shifts in the spatial distribution of precipitation, precipitation intensity and storm arrival time.
Author: Yuan Wang
Publisher: Springer
ISBN: 3662471752
Category : Science
Languages : en
Pages : 100
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Book Description
The studies in this dissertation aim at advancing our scientific understandings about physical processes involved in the aerosol-cloud-precipitation interaction and quantitatively assessing the impacts of aerosols on the cloud systems with diverse scales over the globe on the basis of the observational data analysis and various modeling studies. As recognized in the Fifth Assessment Report by the Inter-government Panel on Climate Change, the magnitude of radiative forcing by atmospheric aerosols is highly uncertain, representing the largest uncertainty in projections of future climate by anthropogenic activities. By using a newly implemented cloud microphysical scheme in the cloud-resolving model, the thesis assesses aerosol-cloud interaction for distinct weather systems, ranging from individual cumulus to mesoscale convective systems. This thesis also introduces a novel hierarchical modeling approach that solves a long outstanding mismatch between simulations by regional weather models and global climate models in the climate modeling community. More importantly, the thesis provides key scientific solutions to several challenging questions in climate science, including the global impacts of the Asian pollution. As scientists wrestle with the complexities of climate change in response to varied anthropogenic forcing, perhaps no problem is more challenging than the understanding of the impacts of atmospheric aerosols from air pollution on clouds and the global circulation.
Author: Andreas Mühlbauer
Publisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN: 9783838106809
Category : Aerosols
Languages : de
Pages : 0
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Book Description
Aerosols are ubiquitous in the Earth's atmosphere and influence the climate system through their interactions with clouds and radiation. With their ability to serve as cloud condensation nuclei and ice nuclei aerosols influence microphysical processes in clouds thereby potentially affecting precipitation. In this book the possible effects of aerosols on orographic precipitation are investigated with a numerical model.
Author: Jessie Marie Creamean
Publisher:
ISBN: 9781267646668
Category :
Languages : en
Pages : 236
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Book Description
Atmospheric aerosols have significant implications for human health and climate. For instance, aerosols impact climate directly by scattering and absorbing solar and terrestrial radiation and indirectly by acting as cloud condensation nuclei (CCN) and ice nuclei (IN), which facilitate cloud droplet and ice crystal formation, respectively. Changes in chemistry, size, and number concentrations between different locations and over time alter how aerosols impact air quality and cloud formation, and can have broader implications on precipitation efficiency and phase. Further, aerosol composition largely depends on meteorology, which influences sources and chemical transformation in the atmosphere. Aerosol-cloud-precipitation interactions represent one of the largest sources of uncertainty in climate science; therefore, a better understanding of the aerosols that contribute to these effects is needed. To address this source of uncertainty, the chemical composition of individual ambient aerosols and aerosols as insoluble residues in precipitation samples was determined using aerosol time-of-flight mass spectrometry (ATOFMS) and provided insight into their potential to serve as cloud seeds at three different locations over time. A three-year summer study (2005-2007) in Riverside, CA afforded information on the inter-annual variability of the urban aerosol due to changes in aerosol transport and meteorological conditions. In the summer of 2008 in Atlanta, GA, tropical cyclones shifted the representative aged urban aerosol to a less-aged, less-CCN active aerosol population, having implications on regional cloud formation after extreme weather events. At a remote site in the Sierra Nevada Mountains in the winter of 2009, observations of newly-formed aerosols presented a new source of CCN. Inter-annual trends in precipitation at the same remote site showed how IN transported from the Sahara and Asia potentially influenced precipitation processes during three winter seasons (2009-2011). Investigating changes in cloud seeds represents a longer-term goal to reduce uncertainties associated with modeling aerosol-cloud-precipitation interactions. Larger spatial and temporal coverage is needed to better understand trends in cloud formation and precipitation and to provide more detail for regional and global model parameterization. The results presented herein represent a noteworthy advancement towards understanding variation in composition and sources of cloud seeds in different regions and in most cases long time periods.
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309443458
Category : Science
Languages : en
Pages : 53
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Book Description
One of the most significant and uncertain aspects of climate change projections is the impact of aerosols on the climate system. Aerosols influence the climate indirectly by interacting with nearby clouds leading to small changes in cloud cover, thickness, and altitude, which significantly affect Earth's radiative balance. Advancements have been made in recent years on understanding the complex processes and atmospheric interactions involved when aerosols interact with surrounding clouds, but further progress has been hindered by limited observations. The National Academies of Sciences, Engineering, and Medicine organized a workshop to discuss the usefulness of the classified observing systems in advancing understanding of cloud and aerosol interactions. Because these systems were not developed with weather and climate modeling as a primary mission objective, many participants said it is necessary for scientists to find creative ways to utilize the data. The data from these systems have the potential to be useful in advancing understanding of cloud and aerosol interactions. This publication summarizes the presentations and discussions from the workshop.
Author: Peter V. Hobbs
Publisher: Academic Press
ISBN: 0080959962
Category : Science
Languages : en
Pages : 259
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Book Description
Aerosol and clouds play important roles in determining the earth's climate, in ways that we are only beginning to comprehend. In conjunction with molecular scattering from gases, aerosol and clouds determine in part what fraction of solar radiation reaches the earth's surface, and what fraction of the longwave radiation from the earth escapes to space. This book provides an overview of the latest research on atmospheric aerosol and clouds and their effects on global climate. Subjects reviewed include the direct and indirect effects of aerosol on climate, the radiative properties of clouds and their effects on the Earth's radiation balance, the incorporation of cloud effects in numerical weather prediction models, and stratospheric aerosol and clouds.
Author: Kuan-Ting O
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Book Description
Recent observational studies have shown that ultraclean layers (UCLs) and optically thin veil clouds associated with precipitating deep cumulus are common features of the marine boundary layer in the stratocumulus to cumulus transition. The very low number concentration of cloud droplet and cloud condensation nuclei in UCLs, strong precipitation in the associated cumulus, together with the low optical thickness of optically thin veil clouds, make such a system particularly appealing for the study of aerosol-cloud-precipitation interactions. More importantly, low cloud radiative properties biases (i.e., too few, too bright low cloud bias) in the current generation of global climate models (GCMs) seems strongly associated with the uncertainty in representing optically thin veil clouds, and these clouds may serve as an important constraint on the too few, too bright problem. However, systematic investigation of (1) global contribution and seasonal variability of optically thin veil clouds and (2) aerosol-cloud-precipitation interactions in UCLs and optically thin veil clouds is still lacking. We aim to investigate these problems with aircraft remote sensing, satellite measurements and a cloud resolving model. The dissertation is organized into the following three sections: • Using high resolution aircraft remote sensing measurement to characterize optically thin veil clouds in the stratocumulus to cumulus transition (SCT): Aircraft remote sensing measurements (i.e., lidar and radar) taken abroad NSF/NCAR GV-HIAPER research flights flown during the Cloud System Evolution in the Trades field campaign (CSET) sampled marine air masses between Sacramento, California (38.68N, 121.58W), and Kona (19.68N, 156.08W) are used in our study. Optically thin veil clouds, defined as the subset of low clouds with cloud bases > 1 km that do not fully attenuate high-spectral-resolution lidar signal (HSRL) (i.e., indicating optical depths 3), comprise considerable cover of low clouds (~ 40 %) over the SCT. It is found that optically thin veil clouds are also geometrically thin with cloud thickness ~ 200 m, and commonly reside in the upper boundary layer with average cloud base 1.5 km. • Investigating deeper, precipitating PBLs associated with optically thin veil clouds in the Sc-Cu Transition using spaceborne satellite measurements: Variability and vertical structure of optically thin veil clouds over SCT regions around the globe are investigated using both passive and active satellite observations. These observations reveal pronounced relationships between optically thin veil clouds, strong precipitation, deep planetary boundary layer (PBL) height and low cloud droplet number concentration (CDNC). The results are in agreement with the hypothesis that the low optical thickness of veil clouds over the SCT is contingent on the low CDNC caused by strong precipitation scavenging occurring in active cumuli, a process whose efficiency is strongly dependent on maximum condensate amount in updrafts and thus is highly constrained by PBL height. • Exploring aerosol-cloud-precipitation processes in UCLs and optically thin veil clouds system using a cloud resolving model: Characteristics of UCLs and optically thin veil clouds are investigated in the cloud resolving model (CRM). The domain mean cloud and aerosol properties in UCLs and optically thin veil clouds from CRM simulations agree with recent observational studies in general. The simulation results show that the detrainment from active precipitating cumulus produces the stratiform veil clouds, which are strongly depleted in particle concentration due to very efficient coalescence-scavenging process in ascending parcels passing through cumulus towers. The simulation shows a median CDNC in thin veil clouds of 5.8 cm−3, implying that majority of thin veil clouds are UCLs as well and confirming the strong connection between veil clouds and UCLs. In addition, there is a strong correlation between surface precipitation and the fraction of low clouds that are UCLs, and such correlation implies the importance of precipitation scavenging for the formation of UCLs. A cloud resolving model coupled with a prognostic aerosol scheme is used in our study, enabling characterization of the spatiotemporal variability of aerosol in the boundary layer. The results show that depletion of aerosol concentration starts first in the upper boundary layer that is associated with in-cloud coalescence scavenging process. The evaporation of veil clouds leaves very low CCN number concentration (Na
Author: Hsiang-He Lee
Publisher:
ISBN: 9781321363142
Category :
Languages : en
Pages :
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Book Description
The source-oriented Weather Research and Forecasting chemistry model (SOWC) was modified to include warm/cold cloud processes and applied to investigate 1) how source-oriented aerosols influence fog formation and optical properties in the atmosphere, 2) how aerosol mixing state influences cloud and ice formation and atmospheric optical properties during a winter storm, and 3) the direct, semi-direct, and indirect effects of long-range transport dust on severe weather over California and the Eastern Pacific. SOWC tracks 6-dimensional chemical variables (X, Z, Y, Size Bins, Source Types, Species) through an explicit simulation of atmospheric chemistry and physics. In this study, all aerosol source types can activate to form cloud condensation nuclei (CCN) based on the Köhler theory, but the dust is the only source of ice nuclei (IN). Furthermore, a new source-oriented cloud module in the two-moment Purdue Lin microphysics scheme, and a new module with all source-oriented hydrometeors (cloud, ice, rain, snow and graupel) in the Morrison two-moment microphysics scheme were implemented into the SOWC model to study fog events and winter storm cases, respectively. In Chapter 2, the enhanced SOWC model was used to study a fog event that occurred on January 17th, 2011, in the Central Valley of California. The SOWC reasonably portrays the spatial distribution and duration of the fog event consistent with observations. The source-oriented mixture representation of particles reduced cloud droplet number relative to the internal mixture approach that artificially coats hydrophobic particles with hygroscopic components. The fraction of aerosols activating into CCN at a supersaturation of 0.5% in the Central Valley decreased from 86% in the internal mixture model to 68% in the source-oriented model. This increased the surface energy flux by 3-5 W m-2 and surface temperature by as much as 0.15 K. In Chapter 3, the enhanced SOWC model was used to study a winter storm that occurred on March 6th, 2011, in California. Compared to ground based observations, SOWC with the modified Morrison microphysics scheme and modified Goddard radiation schemes predicted reasonable precipitation, but the onset of precipitation is delayed by 5 hours. Immersion freezing was the main mechanism for ice nuclei formation. Secondary coatings on dust particles increased IN from immersion freezing but decreased IN from contact freezing. Increasing CCN and IN in the internal mixing experiment produced more ice crystals and cloud droplets but did not significantly alter total perception under the conditions studied. However, because of the reducing riming efficiency from snow to graupel in the source-oriented mixing experiment, it resulted more snowfall (less rainfall) on the ground, especially over the mountain area. In Chapter 4, the SOWC model was used to understand the direct, semi-direct, and indirect effects of long-range transport dust on severe weather over Eastern Pacific Ocean. The maximum averaged IN nucleation rate increased 36% after adding long-range transport dust. Because clouds in mid-latitude originate precipitately via the ice phase, an increase in IN can enhance ice formation from supercooled water by heterogenetic freezing (mainly contact freezing) and then to alter hydrometer water amount. Adding long-range transport dust increased the mixing ratio and number concentration for almost all hydrometers. However, the changes of adding local dust in local+LR_dust from LR_dust is more complicated due to the importance of hydrometers in the cumulus scheme. The change in the strength of convection after adding long-range transport dust (or local dust) also produces a noticeable distinction in the precipitation pattern, but the total precipitation did not have major difference after adding long-range transport dust (or local dust).
Author: Miguel A. C. Teixeira
Publisher: Frontiers Media SA
ISBN: 2889450163
Category :
Languages : en
Pages : 162
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Book Description
Mountainous regions occupy a significant fraction of the Earth's continents and are characterized by specific meteorological phenomena operating on a wide range of scales. Being a home to large human populations, the impact of mountains on weather and hydrology has significant practical consequences. Mountains modulate the climate and create micro-climates, induce different types of thermally and dynamically driven circulations, generate atmospheric waves of various scales (known as mountain waves), and affect the boundary layer characteristics and the dispersion of pollutants. At the local scale, strong downslope winds linked with mountain waves (such as the Foehn and Bora) can cause severe damage. Mountain wave breaking in the high atmosphere is a source of Clear Air Turbulence, and lee wave rotors are a major near-surface aviation hazard. Mountains also act to block strongly stratified air layers, leading to the formation of valley cold air-pools (with implications for road safety, pollution, crop damage, etc.) and gap flows. Presently, neither the fine-scale structure of orographic precipitation nor the initiation of deep convection by mountainous terrain can be resolved adequately by regional-to global-scale models, requiring appropriate downscaling or parameterization. Additionally, the shortest mountain waves need to be parameterized in global weather and climate prediction models, because they exert a drag on the atmosphere. This drag not only decelerates the global atmospheric circulation, but also affects temperatures in the polar stratosphere, which control ozone depletion. It is likely that both mountain wave drag and orographic precipitation lead to non-trivial feedbacks in climate change scenarios. Measurement campaigns such as MAP, T-REX, Materhorn, COLPEX and i-Box provided a wealth of mountain meteorology field data, which is only starting to be explored. Recent advances in computing power allow numerical simulations of unprecedented resolution, e.g. LES modelling of rotors, mountain wave turbulence, and boundary layers in mountainous regions. This will lead to important advances in understanding these phenomena, as well as mixing and pollutant dispersion over complex terrain, or the onset and breakdown of cold air pools. On the other hand, recent analyses of global circulation biases point towards missing drag, especially in the southern hemisphere, which may be due to processes currently neglected in parameterizations. A better understanding of flow over orography is also crucial for a better management of wind power and a more effective use of data assimilation over complex terrain. This Research Topic includes contributions that aim to shed light on a number of these issues, using theory, numerical modelling, field measurements, and laboratory experiments.
Author: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Book Description
Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. - Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate - Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry - Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
