Smoke Aerosols, Clouds, Rainfall and Climate (SMOCC) An EU Research Project, led by Prof. Meinrat O. Andreae Max Planck Institute for Chemistry, Mainz

How do aerosols influence climate? I) Direct Effects (i.e., not involving cloud) a) Backscattering of sunlight into space  increased albedo  cooling

Ib) Absorption of sunlight At surface: cooling In atmosphere: warming Effects: reduced convection and cloudiness reduced evaporation from ocean reduced rainfall downwind The key parameter is the black carbon content of the aerosol and its mixing state

Aerosol Mixing State of Black Carbon Forcing (W m-2, Jacobson, 2000) External Mixing +0.27 Black Carbon Core +0.54 Internal Mixing +0.78

II) Indirect Effects Each cloud droplet needs a "seed" or nucleus to be able to form: "Cloud Condensation Nucleus” (CCN) For a given cloud, the more CCN in the air, the more droplets Since the water supply in a cloud is limited: more droplets means smaller droplets

IIa) First Indirect Effect Ship tracks off the Washington coast Adding CCN makes clouds with more, smaller droplets. These clouds are whiter, reflect more sunlight  net cooling

IIb) Second Indirect Effect “Overseeding“: To produce rain, cloud droplets need to be bigger than ~ 14 µm radius. When there are too many CCN, this radius is not reached and rainfall is suppressed. Therefore: Adding CCN increases cloud lifetime and cloud abundance  Cooling

This rain-suppression applies only to "warm" clouds (those not containing ice) If there is enough latent heat available (tropics) the air will rise and rain-production mechanisms involving ice will take over. The result is a shift in the energy-release from lower levels (warm clouds) to upper levels in the troposphere. Since the tropics are the heat-engines of the atmosphere, this has far-reaching climatic effects!

Is there evidence that this is happening? Wet season data from Amazon basin indicate CCN are very low in “natural” state  “Green Ocean” Dry “smoky” season data show strong increase in CCN due to biomass smoke  More tall convection and lightning  Latent heat release at higher levels

Large Scale Biosphere-Atmosphere Experiment over Amazônia CLAIRE ‘98 Balbina, Amazonas 28 March - 15 April EUSTACH ‘99 Rebio Jaru: forest Nossa Senhora: pasture Rondônia 7 April – 21 May 15 Sept. – 1 Nov. Aircraft Experiment 2 – 14 September

Summary of CCN Spectra

Clear day Visibility ~ ??? km NCN ~ 500 cm-3 BC ~ 0.2 mg m-3 Smoke haze Visibility ~ 800 m NCN ~ 10000 cm-3 BC ~ 7 mg m-3

The “Green Ocean”: Maritime clouds over the Amazon April - the wet and clean time of year: Note the shallow precipitating clouds, extensive warm rainout, glaciation at T>-10oC, and few lightning events VIRS T-Re TRMM VIRS+PR, Amazon, 1998 04 13 16:28

Clear day Visibility ~ ??? km NCN ~ 500 cm-3 BC ~ 0.2 mg m-3 Smoke haze Visibility ~ 800 m NCN ~ 10000 cm-3 BC ~ 7 mg m-3

The “Green Ocean” turns dry: Smoky clouds over the Amazon September: The Fire Season Note that clouds do not precipitate before reaching height of 6.5 km or –12oC isotherm, while containing ample cloud water. TOMS Aerosol Index 13 September 1998 VIRS+PR, Amazon, 1998 13 SEP 14:15 VIRS T-Re

When the “smoky clouds” become Cb, they spark lightning and high Z VIRS T-Re PR H-Z VIRS+PR, Amazon, 1998 09 15 18:16

GCM simulation of the impact of biomass burning in the tropics on the global circulation in the extra-tropics. (Graf et al., 2000).

GCM simulation of the impact of biomass burning in the tropics on the global circulation in the extra-tropics. (Graf et al., 2000).

SMOCC Objectives 1) Make field measurements of aerosol and supporting parameters in the Amazon Basin; 2) chemically characterize the aerosols produced by biomass burning, with particular attention to the organic fraction; 3) determine the link between the aerosol’s chemical/physical properties and its hygroscopic and cloud-nucleating properties; 4) model the effect of biomass burning aerosol on cloud microphysics at the cloud and regional level; 5) investigate the effect of smoke aerosols on climate dynamics and the resulting large-scale climate effects; and 6) use satellite data to detect, validate and quantify the effect of smoke aerosol on cloud properties and precipitation processes.

Partner 1 – The Max Planck Institute for Chemistry (MPIC), Mainz, Germany The role of Partner 1 is: to act as Co-ordinator for the proposed project; to act as Lead Contractor for WP1; to organise and conduct a field experiment in Amazonia, including a ground-based and an aircraft component (WP1); to collect and supply aerosol samples to WP2; to take aerosol measurements during the field campaign, including CCN spectra (WP3), and accompanying data, and provide them to WP3, WP4, and WP6; to analyse aerosol samples by GC-MS and EGA (evolved gas analysis)

SMOCC Field Campaign: LBA-CLAIRE-2002 near Ji-Paraná, Rondonia: FNS pasture site INPE Bandeirante 1 Sept. arrival, 7 Sept. fully operational measurements as long as 30 Nov. MPIC, MPI-BGC, USP, Bologna, Lund, Veszprem, Gent, ...