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Title: Use of in situ cloud condensation nuclei, extinction, and aerosol size distribution Measurements to test a method for retrieving cloud condensation nuclei profiles from surface measurements

Abstract

If the aerosol size distribution and composition below cloud are uniform the vertical profile of cloud condensation nuclei concentration can be retrieved entirely from surface measurements, thus providing the potential for long-term measurements. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. The CCN retrieval works better than expected if in situ measurements of extinction are used. The retrieval works better for supersaturations of 0.1% than for 1%, because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. The performance of the retrieval varies significantly from day to day, particularly at 1% supersaturation. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval.

Authors:
; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
962527
Report Number(s):
PNNL-SA-43562
KP1205010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research. D. (Atmospheres), 111(D05S10)
Country of Publication:
United States
Language:
English

Citation Formats

Ghan, Steven J., Rissman, Tracey A., Elleman, Robert, Ferrare, Richard, Turner, David D., Flynn, Connor J., Wang, Jian, Ogren, J. A., Hudson, James, Jonsson, Haf, VanReken, Timothy, Flagan, Richard C., and Seinfeld, John H. Use of in situ cloud condensation nuclei, extinction, and aerosol size distribution Measurements to test a method for retrieving cloud condensation nuclei profiles from surface measurements. United States: N. p., 2006. Web. doi:10.1029/2004JD005752.
Ghan, Steven J., Rissman, Tracey A., Elleman, Robert, Ferrare, Richard, Turner, David D., Flynn, Connor J., Wang, Jian, Ogren, J. A., Hudson, James, Jonsson, Haf, VanReken, Timothy, Flagan, Richard C., & Seinfeld, John H. Use of in situ cloud condensation nuclei, extinction, and aerosol size distribution Measurements to test a method for retrieving cloud condensation nuclei profiles from surface measurements. United States. doi:10.1029/2004JD005752.
Ghan, Steven J., Rissman, Tracey A., Elleman, Robert, Ferrare, Richard, Turner, David D., Flynn, Connor J., Wang, Jian, Ogren, J. A., Hudson, James, Jonsson, Haf, VanReken, Timothy, Flagan, Richard C., and Seinfeld, John H. Thu . "Use of in situ cloud condensation nuclei, extinction, and aerosol size distribution Measurements to test a method for retrieving cloud condensation nuclei profiles from surface measurements". United States. doi:10.1029/2004JD005752.
@article{osti_962527,
title = {Use of in situ cloud condensation nuclei, extinction, and aerosol size distribution Measurements to test a method for retrieving cloud condensation nuclei profiles from surface measurements},
author = {Ghan, Steven J. and Rissman, Tracey A. and Elleman, Robert and Ferrare, Richard and Turner, David D. and Flynn, Connor J. and Wang, Jian and Ogren, J. A. and Hudson, James and Jonsson, Haf and VanReken, Timothy and Flagan, Richard C. and Seinfeld, John H.},
abstractNote = {If the aerosol size distribution and composition below cloud are uniform the vertical profile of cloud condensation nuclei concentration can be retrieved entirely from surface measurements, thus providing the potential for long-term measurements. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. The CCN retrieval works better than expected if in situ measurements of extinction are used. The retrieval works better for supersaturations of 0.1% than for 1%, because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. The performance of the retrieval varies significantly from day to day, particularly at 1% supersaturation. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval.},
doi = {10.1029/2004JD005752},
journal = {Journal of Geophysical Research. D. (Atmospheres), 111(D05S10)},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 19 00:00:00 EST 2006},
month = {Thu Jan 19 00:00:00 EST 2006}
}
  • If the aerosol composition and the shape of the aerosol size distribution below cloud are uniform the vertical profile of cloud condensation nuclei concentration can be retrieved entirely from surface measurements, thus providing the potential for long-term measurements of CCN concentrations near cloud base. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. If in situ measurements of extinction are used the CCN retrieval works better than expected for the high supersaturations of the in situ CCN measurements.more » The retrieval works better for supersaturations of 0.1% than for 1%, because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. The performance of the retrieval varies significantly from day to day, particularly at 1% supersaturation. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval, but this vertical structure is difficult to measure from remote sensing at visible wavelengths.« less
  • In situ stratospheric aerosol measurements, from University of Wyoming optical particle counters (OPCs), are compared with Stratospheric Aerosol Gas Experiment (SAGE) II (versions 6.2 and 7.0) and Halogen Occultation Experiment (HALOE) satellite measurements to investigate differences between SAGE II/HALOE-measured extinction and derived surface area and OPC-derived extinction and surface area. Coincident OPC and SAGE II measurements are compared for a volcanic (1991-1996) and nonvolcanic (1997 2005) period. OPC calculated extinctions agree with SAGE II measurements, within instrumental uncertainty, during the volcanic period, but have been a factor of 2 low during the nonvolcanic period. Three systematic errors associated with themore » OPC measurements, anisokineticity, inlet particle evaporation, and counting efficiency, were investigated. An overestimation of the OPC counting efficiency is found to be the major source of systematic error. With this correction OPC calculated extinction increases by 15 30% (30 50%) for the volcanic (nonvolcanic) measurements. These changes significantly improve the comparison with SAGE II and HALOE extinctions in the nonvolcanic cases but slightly degrade the agreement in the volcanic period. These corrections have impacts on OPC-derived surface area density, exacerbating the poor agreement between OPC and SAGE II (version 6.2) surface areas. This disparity is reconciled with SAGE II version 7.0 surface areas. For both the volcanic and nonvolcanic cases these changes in OPC counting efficiency and in the operational SAGE II surface area algorithm leave the derived surface areas from both platforms in significantly better agreement and within the 40% precision of the OPC moment calculations.« less
  • In situ stratospheric aerosol measurements, from University of Wyoming optical particle counters (OPCs), are compared with Stratospheric Aerosol Gas Experiment (SAGE) II (versions 6.2 and 7.0) and Halogen Occultation Experiment (HALOE) satellite measurements to investigate differences between SAGE II/HALOE-measured extinction and derived surface area and OPC-derived extinction and surface area. Coincident OPC and SAGE II measurements are compared for a volcanic (1991-1996) and nonvolcanic (1997-2005) period. OPC calculated extinctions agree with SAGE II measurements, within instrumental uncertainty, during the volcanic period, but have been a factor of 2 low during the nonvolcanic period. Three systematic errors associated with the OPCmore » measurements, anisokineticity, inlet particle evaporation, and counting efficiency, were investigated. An overestimation of the OPC counting efficiency is found to be the major source of systematic error. With this correction OPC calculated extinction increases by 15-30% (30-50%) for the volcanic (nonvolcanic) measurements. These changes significantly improve the comparison with SAGE II and HALOE extinctions in the nonvolcanic cases but slightly degrade the agreement in the volcanic period. These corrections have impacts on OPC-derived surface area density, exacerbating the poor agreement between OPC and SAGE II (version 6.2) surface areas. Furthermore, this disparity is reconciled with SAGE II version 7.0 surface areas. For both the volcanic and nonvolcanic cases these changes in OPC counting efficiency and in the operational SAGE II surface area algorithm leave the derived surface areas from both platforms in significantly better agreement and within the ± 40% precision of the OPC moment calculations.« less
  • A method of retrieving vertical profiles of cloud condensation nuclei (CCN) concentration from surface measurements is proposed. Surface measurements of the CCN concentration are scaled by the ratio of the backscatter (or extinction) vertical profile to the backscatter (or extinction) at or near the surface. The backscatter (or extinction) profile is measured by Raman lidar, and is corrected to dry conditions using the vertical profile of relative humidity (also measured by Raman lidar) and surface measurements of the dependence of backscatter (or extinction) on relative humidity. The method assumes the surface aerosol size distribution and composition are representative of themore » vertical column. Aircraft measurements of aerosol size distribution are used to test the dependence of the retrieval on the uniformity of aerosol size distribution. The retrieval is found to be robust for supersaturations less than 0.02%, but breaks down at higher supersaturations if the vertical profile of aerosol size distribution differs markedly from the distribution at the surface. Such conditions can be detected from the extinction/backscatter ratio.« less
  • Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). Our measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site.The CCN measurements were continuously cycled through 10 levels of supersaturation ( S=0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S = 1.10 % to 172more » nm at S = 0.11 %. Furthermore, the particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode ( κ Ait = 0.14 ± 0.03), higher values for the accumulation mode ( κ Acc = 0.22 ± 0.05), and an overall mean value of κ mean = 0.17 ± 0.06, consistent with high fractions of organic aerosol.The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentration. Here, we find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes.For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.« less