First Science Team Meeting

Notes from Discussion Group B: Use of Transport Modeling in Integrated Climatologies

Moderator: Joyce Penner; Rapporteur: Cathy Chuang

Discussion outline:

- In what specific areas will transport models contribute the most for the development of aerosol climatology?
- What types of aerosol source data are available and what else do modelers need in simulation of global aerosol cycle?
- How to use current satellite and in situ data for validation of model simulations?
- What kinds of new data will be available from the Science Team?

To examine the climate impacts by aerosols first requires a quantitative understanding, on a global basis, of the sources, transformation and removal processes for aerosols and aerosol precursors, as well as the cycles and budgets for the trace species which comprise the aerosols. Although field studies and satellite measurements provide useful data of aerosol distribution, a global model might be the best approach able to identify and analyze the responsible processes as well as to address the relative importance of anthropogenic and natural emissions in the global aerosol distribution. The model studies performed within the Science Team domain are listed in Table 1.

Table 1. Model studies

Investigator	Aerosol types	Meteorology
M. Chin	sulfate, dust, sea salt, carbonaceous	Geos DAS
C. Chuang	sulfate, dust, sea salt, carbonaceous	NCAR CCM
A. Del Genio	sulfate, dust, sea salt, carbonaceous	GISS CCM
U. Lohmann	sulfate, dust, sea salt, carbonaceous	ECHAM
J. Penner	dust, biomass aerosols	Nudged ECHAM
G. Pitari	sulfate, aircraft aerosols	low resolution climate model
P. Rasch	sulfate, dust, carbonaceous	CCM3
O.B. Toon	dust	NCEP
D. Westphal	sulfate, dust, sea salt, carbonaceous	NOGAPS

Atmospheric aerosols are derived from a variety of sources. Complete aerosol emission inventory is a crucial element in the future advancement of climate/aerosol models. The available emission data for aerosols and aerosol precursors at this moment include:

for a particular single year

SO₂,, DMS, H₂S and COS

dust

biomass burning and fossil fuel carbonaceous aerosols

sea salt

natural organic aerosols

1996 burned area in Africa (Barbosa et al., 1998)

1993 world fire atlas (burned spots)

1950 - 1994 fossil fuel SO₂

However, the modelers also need both source inventories and meteorological fields for 1980 - present in order to quantitatively define the global distributions of aerosol (direct and indirect) radiative forcings for the period of satellite data (1979-near future).

One of the most important tasks for modelers is to compare the simulated total aerosol concentrations and optical properties not only with the in-situ data from field campaigns or from surface networks designed for long-term observations but also with data retrieved from remote sensing instruments. These comparisons can validate whether the aerosol emission fields are correct and whether the treatments of transport and transformation are reasonable. The data sets available for validation at this moment include:

TOMS absorbing index (1978 - present)

AVHRR aerosol optical depth (1979 - present)

SAM II, SAGE I, SAGE II (1978 - present)

GLOBE Lidar (1989, 1990)

LITE (1994)

Raman Lidar aerosol height profiles

Data compilation - optical depth (Dave Covert)

Surfaced-based AERONET data

SO₂ surface concentration data and sulfate wet deposition data:

EMEFS, July 1988 to May 1990

EMEP, 1983 - 1992

Organic and black carbon data (various data)

AEROCE, NOAA, and IMPROVE surface data sets

WMO observing stations with free troposphere data sets (e.g., Mauna Loa; Iza¤a; Summit, Greenland; Jungfraujoch)

U. Wyoming Balloon Sondes

The new data sets which will be available from the Science Team members are listed in Table 2.

Table 2. New data sets available from the Science Team

Investigators	Data types
A. Clarke	spatial, temporal, regional and meteorological characterization of aerosol size distribution, optical properties and chemistry for the North and South Pacific
T. Bates	shipboard aerosol properties
G. Kukla	hourly surface solar radiation for clear, partly cloudy and overcast sky at selected stations
Z. Li	climatology of clear sky difference between observed and pollution-free radiative energy using satellite and surface measurements over boreal forest and oceans
T. Novakov	TC, OC, and BC data evaluation plus changes over last 20 years
L. Poole	aerosol extinction profiles at 1 ?m (1978-1993; 1979-1981) and profiles at 4 wavelengths (1984-present); aerosol backscatter profiles at Langley since 1974
C. Randall	El Chichon aerosols
L. Remer/Y. Kaufman	smoke effects on clouds
P. Russell	airborne sunphotometer(events campaigns)
L. Stowe	AVHRR Pathfinder
P. Stackhouse	site specific, monthly average clear sky broadband difference between observed and pollution-free solar insolation (1983-1992)
R. Stuhlmann	arctic haze and clouds - March/April 1998 and Meteosat ERB aerosol and cloud properties > 2000
O. Torres	clear sky optical depth of non-absorbing aerosols and clear sky optical depth of absorbing aerosols when vertical distribution is available (1979-1985; 1996-1997; 1997-present)
E. Uthe	aerosol/cloud optical characteristic from campaigns , DC-8 LIDAR - vertical distribution
D. Winker	aerosol extinction and backscatter cross section, optical depth, boundary layer height - September 1994

Recommendation 1: Dust particles play an important role in the assessment of aerosol climate forcing but the estimates of global dust source strength vary in a large range (500 - 5000 Tg/year), a workshop should be held for comparison of dust source algorithm and the model simulated dust distribution.

Recommendation 2: To further validate the chemistry and transport processes in global models, a thorough comparison to detailed mesoscale models which have higher resolution in apace and time might be helpful to reduce the uncertainty resulted from the computational limitation in global models.

Return to Conference Homepage