GACP Projects
Form A: GACP ACCOMPLISHMENT REPORT
Name: Tihomir NOVAKOVInstitution: Lawrence Berkeley National Laboratory
Environmental Energy Technologies Division
MS - 73
One Cyclotron Road
Berkeley, CA 94720
TITLE: Distribution and Properties of Carbonaceous aerosols: An Analysis of Existing Data
ABSTRACT: The objective of this project is to compile, summarize, analyze, and estimate the uncertainties in past field measurements of total (TC), organic (OC) and black carbon (BC), as well as, the physical and chemical properties of this aerosol component. The values of reported concentrations may be influenced by method and sampling dependent artifacts which, if unaccounted for, may either over- or underestimate the actual concentrations. Consequently, evaluation of uncertainties is important because these may be large enough to render some of the reported concentrations unacceptable for achieving either mass or radiative closure. This activity will identify global regions where useful data exists and regions where there is a severe lack of data, and provide a needed level of quality assurance of the existing field data. The secondary objective is to examine the changes that occurred over the past 20 years in regional use of fuels whose combustion is the principal sources of anthropogenic carbonaceous aerosols. The purpose is to derive surrogates for changing aerosol concentration that can be used as indicators of geographic regions where aerosol forcing might be detectable from space-based observations.
GOALS: Long-term research goal is to develop a comprehensive understanding of the role of carbonaceous aerosol component in both direct and indirect aerosol forcing.
OBJECTIVES: Specific research objectives, related to the objectives of GACP, are to critically evaluate existing data on concentrations and properties of natural and anthropogenic carbonaceous aerosols. The project has three tasks. The firsts is to compile and summarize the data on mass concentrations (and properties) of total (TC), organic (OC) and black carbon (BC) measured in different parts of the world over the past two decades. These data are complemented with concurrently measured data on aerosol mass and concentrations of inorganic species whenever available. The second task is to estimate the uncertainties in the reported data. These data may be influenced by method and sampling dependent artifacts which, if unaccounted for, may either over- or underestimate the actual concentrations. Consequently, evaluation of uncertainties is important because these may be large enough to render some of the reported concentrations unacceptable for achieving either mass or radiative closure. The third task is to empirically analyze the data (obtained from the above tasks) to infer the global distributions, geographic and temporal trends of carbonaceous aerosols. This activity will include an examination of regional emissions that can be used as surrogates for primary carbonaceous aerosols and their gaseous precursors. These activities will provide a needed level of quality assurance of the existing field data, and identify global regions where useful data exists and regions where there is a severe lack of data. Both will help in designing future field measurements.
APPROACH: The methodology used to accomplish the first task of the research objectives of the project involved obtaining journal papers that contain the relevant data. So far we have assembled about one hundred such papers. These were further subdivided into URBAN, RURAL, MARINE and REMOTE sites. For each site the data on concentrations and methods of measurements were abstracted and compiled (see below).
TASKS COMPLETED: During the first year of GACP we have focused on the first
task, described above. We have thoroughly examined the data obtained since
approximately 1978 at 197 locations and sites worldwide. The locations used
in the compilations completed so far pertain to:
URBAN SITES:
81 locations in the US, Canada and South America.
18 in Europe
12 in Asia.
RURAL SITES;
32 in the US
13 in Europe
5 in Asia
MARINE
32 locations in Atlantic and Pacific ocean regions
REMOTE
9 sites
For each site the following information has been compiled: Year and month
of measurements, mass concentrations of all reported aerosol species,
sample type, particle size distributions, sample size cuts, analytical
methods used, corrections (if any) made by the authors, and bibliographical
information (references). Additionally, several papers give information
about specific properties of carbonaceous aerosols such as the
water-soluble organic carbon fraction, altitude dependence of aerosol
species concentrations, and absorption cross section of black carbon. This
information has been compiled and presented separately from the mass
concentrations data.
FUTURE PLANS: Future plans involve completion of task one, and work on the remaining two tasks (see below).
RESULTS: The results of first year accomplishments are presented in document (compendium) containing all information compiled and grouped by location and year of data acquisition. A hard copy draft version of this document will be available for distribution at the forthcoming GACP Science Team Meeting.
FORM C: FUTURE PLANS
Name: Tihomir NOVAKOV
Institution: Lawrence Berkeley National Laboratory
Research plan for the second year of our participation in GACP focuses on data evaluation with the objective of estimating the uncertainties in the reported data. Furthermore, we will augment the data survey by examining the literature that was either unavailable or not yet published during the first year of the project.
