Biosphere/Atmosphere Interactions in the Tropics

NO emission from soil

VOC emitted from leaf surface

O3 deposition to leaf surface

O3 and NO2 deposition to

stomata

NO + O3 NO2 + O3

NO + O3 NO2 + O2

NO2 + O2 NO + O3

RO’2 + NO RO’ + NO2

NO, NO2, O3, VOC

hv

VOC NO

NO2

NO2

NO2

NO

O3

O3

Modified after Coe et al. 1993

HNO3NH3

HONO?

OH and the Amazon,an untested hypothesis

Some Questions

• What are the timescales of transport and chemical processes in nitrogen cycling between ecosystems and atmosphere?

• How do they interact to determine N species flux in and out the ecosystems?

• How does ecosystem exchange on VOC and N species affect the atmospheric oxidant cycle?

CCN sources in the “clean” tropics:

• Dust, Sea Spray: Over the humid continental tropics, too few to be important

• Marine biogenic sulfate (from DMS): Probably important some of the time

• Terrestrial biogenic sulfate (from DMS and H2S): May play a key role in providing soluble aerosol component

• Secondary Organic Aerosol: May provide a significant part of aerosol mass, but mode of particle formation still under question

• Primary biogenic aerosol: Bacteria, spores, plant debris may account for a large fraction of aerosol mass and number!

CCN Efficiency Spectra

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.5 1.0 1.5

Supersaturation, %

CC

N E

ffici

ency

as

CC

N/C

N r

atio

Aged Smoke in Cloud Layer

Fresh Smoke in Mixed Layer

Green Ocean (CLAIRE98)

Pyrogenic CCN have

pronounced impact on

cloud droplet size spectra!

Aerosol pollution increases the height where cloud drops grow big enough to grow by coagulation and form “warm” rain

(Andreae et al., SCIENCE, 2004)

Some Questions

• What is the source of “background” Amazonian aerosols, and what are their properties?

• What determines the cloud droplet and ice nucleating ability of Amazonian aerosols?

• How do aerosols affect the formation and properties of ice phase in clouds over Amazonia?

• How do aerosols affect rainfall amount and rain rate over Amazonia?

Compare flash rates in January...

… and in September

How does smoke get into the stratosphere??

Simulation of a Pyrocumulus Blowup

Potential Temperature on the 100 µg/m³ aerosol-isosurface

Some Questions

• Do aerosols affect the amount and distribution of lightning over Amazonia?

• Does this affect the chemical properties of the atmosphere?

• Do fires and aerosols affect the intensity of deep convection in the tropics?

• Is this important for the chemistry and physical properties of the UTLS?