Scattering and radiative properties of semi-external versus external mixtures of different aerosol types

2004 ◽  
Vol 88 (1-3) ◽  
pp. 139-147 ◽  
Author(s):  
Michael I. Mishchenko ◽  
Li Liu ◽  
Larry D. Travis ◽  
Andrew A. Lacis
Keyword(s):  
Radiative Properties ◽  
Aerosol Types

scholarly journals Leipzig Ice Nucleation chamber Comparison (LINC): intercomparison of four online ice nucleation counters

2017 ◽  
Vol 17 (18) ◽  
pp. 11683-11705 ◽  
Author(s):  
Monika Burkert-Kohn ◽  
Heike Wex ◽  
André Welti ◽  
Susan Hartmann ◽  
Sarah Grawe ◽  
...  
Keyword(s):  
Water Saturation ◽  
Aerosol Particles ◽  
Birch Pollen ◽  
Ice Nucleation ◽  
Radiative Properties ◽  
Crystal Formation ◽  
Ice Crystal ◽  
Thermodynamic Conditions ◽  
Immersion Freezing ◽  
Aerosol Types

Abstract. Ice crystal formation in atmospheric clouds has a strong effect on precipitation, cloud lifetime, cloud radiative properties, and thus the global energy budget. Primary ice formation above 235 K is initiated by nucleation on seed aerosol particles called ice-nucleating particles (INPs). Instruments that measure the ice-nucleating potential of aerosol particles in the atmosphere need to be able to accurately quantify ambient INP concentrations. In the last decade several instruments have been developed to investigate the ice-nucleating properties of aerosol particles and to measure ambient INP concentrations. Therefore, there is a need for intercomparisons to ensure instrument differences are not interpreted as scientific findings.In this study, we intercompare the results from parallel measurements using four online ice nucleation chambers. Seven different aerosol types are tested including untreated and acid-treated mineral dusts (microcline, which is a K-feldspar, and kaolinite), as well as birch pollen washing waters. Experiments exploring heterogeneous ice nucleation above and below water saturation are performed to cover the whole range of atmospherically relevant thermodynamic conditions that can be investigated with the intercompared chambers. The Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the Portable Immersion Mode Cooling chAmber coupled to the Portable Ice Nucleation Chamber (PIMCA-PINC) performed measurements in the immersion freezing mode. Additionally, two continuous-flow diffusion chambers (CFDCs) PINC and the Spectrometer for Ice Nuclei (SPIN) are used to perform measurements below and just above water saturation, nominally presenting deposition nucleation and condensation freezing.The results of LACIS and PIMCA-PINC agree well over the whole range of measured frozen fractions (FFs) and temperature. In general PINC and SPIN compare well and the observed differences are explained by the ice crystal growth and different residence times in the chamber. To study the mechanisms responsible for the ice nucleation in the four instruments, the FF (from LACIS and PIMCA-PINC) and the activated fraction, AF (from PINC and SPIN), are compared. Measured FFs are on the order of a factor of 3 higher than AFs, but are not consistent for all aerosol types and temperatures investigated. It is shown that measurements from CFDCs cannot be assumed to produce the same results as those instruments exclusively measuring immersion freezing. Instead, the need to apply a scaling factor to CFDCs operating above water saturation has to be considered to allow comparison with immersion freezing devices. Our results provide further awareness of factors such as the importance of dispersion methods and the quality of particle size selection for intercomparing online INP counters.

scholarly journals Separating mixtures of aerosol types in airborne High Spectral Resolution Lidar data

2013 ◽  
Vol 6 (5) ◽  
pp. 8269-8309
Author(s):  
S. P. Burton ◽  
M. A. Vaughan ◽  
R. A. Ferrare ◽  
C. A. Hostetler
Keyword(s):  
Spectral Resolution ◽  
Radiative Forcing ◽  
Urban Pollution ◽  
Radiative Properties ◽  
High Spectral Resolution ◽  
Mixing Rules ◽  
Source Attribution ◽  
Mixing Ratios ◽  
High Spectral Resolution Lidar ◽  
Aerosol Types

Abstract. Knowledge of aerosol type is important for source attribution and for determining the magnitude and assessing the consequences of aerosol radiative forcing. However, atmospheric aerosol is frequently not a single pure type, but instead occurs as a mixture of types, and this mixing affects the optical and radiative properties of the aerosol. This paper extends the work of earlier researchers by using the aerosol intensive parameters measured by the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-1) to develop a comprehensive and unified set of rules for characterizing the external mixing of several key aerosol intensive parameters: extinction-to-backscatter ratio (i.e. lidar ratio), backscatter color ratio, and depolarization ratio. We present the mixing rules in a particularly simple form that leads easily to mixing rules for the covariance matrices that describe aerosol distributions, rather than just scalar values of measured parameters. These rules can be applied to infer mixing ratios from the lidar-observed aerosol parameters, even for cases without significant depolarization. We demonstrate our technique with measurement curtains from three HSRL-1 flights which exhibit mixing between two aerosol types, urban pollution plus dust, marine plus dust, and smoke plus marine. For these cases, we infer a time-height cross-section of mixing ratio along the flight track, and partition aerosol extinction into portions attributed to the two pure types.

scholarly journals Optical Characteristics and Radiative Properties of Aerosols in Harbin, Heilongjiang Province during 2017

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 463
Author(s):  
Jiemei Liu ◽  
Wenxiang Shen ◽  
Yuan Yuan ◽  
Shikui Dong
Keyword(s):  
Radiative Forcing ◽  
Radiative Properties ◽  
Santa Barbara ◽  
Mean Values ◽  
Aerosol Radiative Forcing ◽  
Direct Radiative Forcing ◽  
Different Seasons ◽  
Atmospheric Radiative Transfer ◽  
Aerosol Types ◽  
Aerosol Radiative

This study considers aerosol optical properties and direct radiative forcing over Harbin (126.63° E, 45.75° N), the highest latitude city in Northeast China, during 2017. Observations based on the CE-318 sun-photometer show that the annual mean values of the aerosol optical depth (AOD) at 500 nm and the Angstrom exponent (AE) at 440–870 nm over Harbin are respectively 0.26 ± 0.20 and 1.36 ± 0.26. Aerosol loading is the highest in the spring followed by winter, and the lowest loading is in autumn. AE440–870 is the highest in summer, second highest in winter, and lowest in autumn. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model is used to estimate the shortwave aerosol radiative forcing at the top of the atmosphere, on the Earth’s surface and in the atmosphere, and the annual mean values are −16.36 ± 18.42 Wm−2, −71.01 ± 27.37 Wm−2 and 54.65 ± 30.62 Wm−2, respectively, which indicate that aerosols cause climate effects of cooling the earth-atmosphere system, cooling the earth’s surface and heating the atmosphere. Four main aerosol types in Harbin are classified via AOD and AE. Specifically, clean continental, mixed type, biomass burning and urban industry, and desert dust aerosols accounted for 51%, 38%, 9%, and 2% of the total, respectively. Aerosol radiative forcing varies greatly in different seasons, and the aerosol load and type from different emission sources have an important influence on the seasonal variation of radiative forcing.

scholarly journals Leipzig Ice Nucleation chamber Comparison (LINC): Inter-comparison of four online ice nucleation counters

2017 ◽  
Author(s):  
Monika Burkert-Kohn ◽  
Heike Wex ◽  
André Welti ◽  
Susan Hartmann ◽  
Sarah Grawe ◽  
...  
Keyword(s):  
Water Saturation ◽  
Aerosol Particles ◽  
Birch Pollen ◽  
Ice Nucleation ◽  
Radiative Properties ◽  
Crystal Formation ◽  
Ice Crystal ◽  
Thermodynamic Conditions ◽  
Immersion Freezing ◽  
Aerosol Types

Abstract. Ice crystal formation in atmospheric clouds has a strong effect on precipitation, cloud lifetime, cloud radiative properties and thus the global energy budget. Primary ice formation above 235 K is initiated by nucleation on seed aerosol particles called ice nucleating particles (INPs). Instruments that measure the ice nucleating potential of aerosol particles in the atmosphere need to be able to accurately quantify ambient INP concentrations. In the last decade several instruments have been developed to investigate the ice nucleating properties of aerosol particles and to measure ambient INP concentrations. Therefore, there is a need for inter-comparisons to ensure instrument differences are not interpreted as scientific findings. In this study, we inter-compare the results from parallel measurements using four online ice nucleation chambers. Seven different aerosol types are tested including untreated and acid treated mineral dust (microcline – a K-feldspar – and kaolinite), as well as birch pollen washing waters. Experiments exploring heterogeneous ice nucleation above and below water saturation are performed to cover the whole range of thermodynamic conditions that can be investigated with the inter-compared chambers. The Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the Portable Immersion Mode Cooling chAmber coupled to the Portable Ice Nucleation Chamber (PIMCA-PINC) performed measurements in the immersion freezing mode. Additionally two continuous flow diffusion chambers (CFDCs) PINC and the Spectrometer for Ice Nuclei (SPIN) are used to perform measurements below and just above water saturation nominally presenting deposition nucleation and condensation freezing. The results of LACIS and PIMCA-PINC agree well over the whole range of measured frozen fractions (FFs) and temperature. In general PINC and SPIN compare well and the observed differences are explained by ice crystal growth and different residence times in the chamber. To study the mechanisms responsible for ice nucleation in the four instruments, FF (from LACIS and PIMCA-PINC) and activated fraction, AF (from PINC and SPIN) are compared. Measured FFs are up to a factor of three higher than AFs, but not consistent for all aerosol types and temperatures investigated. It showed that measurements from CFDCs cannot be assumed to produce the same results as those instruments exclusively measuring immersion freezing. Instead the need to apply a scaling factor to CFDCs operating above water saturation has to be considered to allow comparison with immersion freezing devices. Our results provide further awareness on factors such as the importance of dispersion methods and the quality of particle size-selection for inter-comparing online INP counters.

scholarly journals Separating mixtures of aerosol types in airborne High Spectral Resolution Lidar data

2014 ◽  
Vol 7 (2) ◽  
pp. 419-436 ◽  
Author(s):  
S. P. Burton ◽  
M. A. Vaughan ◽  
R. A. Ferrare ◽  
C. A. Hostetler
Keyword(s):  
Spectral Resolution ◽  
Radiative Forcing ◽  
Urban Pollution ◽  
Radiative Properties ◽  
High Spectral Resolution ◽  
Mixing Rules ◽  
Source Attribution ◽  
Mixing Ratios ◽  
High Spectral Resolution Lidar ◽  
Aerosol Types

Abstract. Knowledge of aerosol type is important for determining the magnitude and assessing the consequences of aerosol radiative forcing, and can provide useful information for source attribution studies. However, atmospheric aerosol is frequently not a single pure type, but instead occurs as a mixture of types, and this mixing affects the optical and radiative properties of the aerosol. This paper extends the work of earlier researchers by using the aerosol intensive parameters measured by the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-1) to develop a comprehensive and unified set of rules for characterizing the external mixing of several key aerosol intensive parameters: extinction-to-backscatter ratio (i.e., lidar ratio), backscatter color ratio, and depolarization ratio. We present the mixing rules in a particularly simple form that leads easily to mixing rules for the covariance matrices that describe aerosol distributions, rather than just single values of measured parameters. These rules can be applied to infer mixing ratios from the lidar-observed aerosol parameters, even for cases without significant depolarization. We demonstrate our technique with measurement curtains from three HSRL-1 flights which exhibit mixing between two aerosol types, urban pollution plus dust, marine plus dust, and smoke plus marine. For these cases, we infer a time-height cross-section of extinction mixing ratio along the flight track, and partition aerosol extinction into portions attributed to the two pure types.

Variability in radiative properties of major aerosol types: A year-long study over Delhi—An urban station in Indo-Gangetic Basin

2014 ◽  
Vol 473-474 ◽  
pp. 659-666 ◽  
Author(s):  
A.K. Srivastava ◽  
V. Yadav ◽  
V. Pathak ◽  
Sachchidanand Singh ◽  
S. Tiwari ◽  
...  
Keyword(s):  
Radiative Properties ◽  
Urban Station ◽  
Aerosol Types

scholarly journals Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula

2014 ◽  
Vol 14 (24) ◽  
pp. 13497-13514 ◽  
Author(s):  
D. Mateos ◽  
M. Antón ◽  
C. Toledano ◽  
V. E. Cachorro ◽  
L. Alados-Arboledas ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Near Infrared ◽  
Fine Particles ◽  
Radiative Properties ◽  
Radiative Effects ◽  
Spectral Ranges ◽  
Aerosol Radiative Effects ◽  
Aerosol Types ◽  
Aerosol Radiative

Abstract. A better understanding of aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloud-free conditions. Over the whole Iberian Peninsula, yearly aerosol radiative effects in the different spectral ranges were found to be −1.1 < AREUV < −0.7, −5.7 < AREVIS < −3.5, −2.6 < ARENIR < −1.6, and −8.8 < ARESW < −5.7 (in W m−2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV / AFESW ratio showed a higher value in the case of absorbing fine particles.

Characterizing the convective heat exchange with plastic shading nets under natural arid conditions

2019 ◽  
pp. 11-20
Author(s):  
Ahmed M Abdel-Ghanya ◽  
Ibrahim M Al-Helal
Keyword(s):  
Wind Speed ◽  
Thermal Radiation ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Convective Heat Exchange ◽  
Radiative Properties ◽  
Wooden Frame ◽  
Arid Conditions ◽  
Air Temperatures ◽  
Radiation Fluxes

Plastic nets are extensively used for shading purposes in arid regions such as in the Arabian Peninsula. Quantifying the convection exchange with shading net and understanding the mechanisms (free, mixed and forced) of convection are essential for analyzing energy exchange with shading nets. Unlike solar and thermal radiation, the convective energy, convective heat transfer coefficient and the nature of convection have never been theoretically estimated or experimentally measured for plastic nets under arid conditions. In this study, the convected heat exchanges with different plastic nets were quantified based on an energy balance applied to the nets under outdoor natural conditions. Therefore, each net was tacked onto a wooden frame, fixed horizontally at 1.5-m height over the floor. The downward and upward solar and thermal radiation fluxes were measured below and above each net on sunny days; also the wind speed over the net, and the net and air temperatures were measured, simultaneously. Nets with different porosities, colors and texture structures were used for the study. The short and long wave’s radiative properties of the nets were pre-determined in previous studies to be used. Re and Gr numbers were determined and used to characterize the convection mechanism over each net. The results showed that forced and mixed convection are the dominant modes existing over the nets during most of the day and night times. The nature of convection over nets depends mainly on the wind speed, net-air temperature difference and texture shape of the net rather than its color and its porosity.

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