bahc-sun set... synthesis volume currently in print; ready october 2003 synthesis papers, science...

BAHC-sun set...

• Synthesis volume currently in print; ready October 2003

• Synthesis Papers, Science series by the end of 2003

• Last SSC meeting (jointly with ISLSCP/GEWEX in September 02(China)

• IPO BAHC was funded until end 2002

BAHC sun set….

• Sun-set clause and IGBP transition taken seriously(?!), no compromising scenarios for prolonged life duration

• BAHC community contributing to 3 elements of the transition process: (I) Water Project, (II) Land-Atmosphere Project, and Land Project

Land - Atmosphere ProjectiLEAPS

• off-spring of BAHC, IGAC, GCTE, GAIM

• full and pro-active partnership with WCRP, story of a truly complementary approach

• learning from the past, capitalizing on successes of this collaboration (GEWEX-BAHC, LBA, ...)

• stepping stone for future joint programmes (mainly with WCRP GEWEX)

ILEAPSIntegrated Land Ecosystem Atmosphere Processes


Goals:

• How do interacting physical, chemical and biological processes transport and transform energy and materials through the land-atmosphere system?

• What are the implications for the dynamics of the Earth System?

• How are human activities influencing the land-atmosphere system (and vice versa)?

• To what extent does the vegetation optimize its physical and chemical environment on various temporal and spatial scales?

NO-NO2-O3-VOC canopy transfer

NO emitted from the forest soil has to pass the trunk space and the canopy layer before being released into the above-canopy atmospheric boundary layer

within the canopy, NO can

react with O3 to form NO2,

which could be deposited on/into vegetation elements

this internal cycling reduces the NO and net NOx emission from the

forest ecoysystem

Meixn

er et al., First LB

A S

cientific Conference, B

elém/P

ará, Brazil, 28-JU

N-00

What do land vegetation & fires emit?

• CO2 – (climatically relevant only when there is no regrowth -

e.g., deforestation)

• NOx, CO, CH4, other hydrocarbons– Ingredients of smog chemistry, greenhouse gases

• Halogenated hydrocarbons (e.g. CH3Br)– stratospheric ozone chemistry

• Aerosols– light scattering and absorbing, cloud condensation nuclei

Biota, Aerosols, Clouds, and Climate

• Biosphere/climate feedback proposed in 1987, in which marine phytoplankton emits a volatile sulfur-containing substance (DMS)

• DMS oxidized to sulfate aerosol particles that serve as cloud condensation nuclei (CCN)

• Increased CCN ->more cloud droplets -> clouds brighter ->reduced amount of sunlight absorbed by the Earth

• Earth cooling -> changing the living conditions for plankton, and thus their rate of DMS emissions

Biota, Aerosols, Clouds, and Climate

• feedback thought to be relevant mostly to the oceans, continental regions considered always to have high levels of CCN, so that clouds would never be “CCN-starved” and any additional CCN would have little effect

• recent work in the Amazon shows this assumption to be wrong: in the wet season with no detectable anthropogenic input, the balance of natural sources and sinks produces a CCN number concentration almost identical to marine values.

Aerosol - Clouds - Climate Interactions• More, smaller droplets reflect more light:

climate gets cooler

• When the drops are smaller than a certain size, they cannot coagulate to rain drops, precipitation is impossible, unless...

• …. There is enough energy (e.g., in the tropics) to move rain formation up higher, and involve ice formation

• This results in:– more intensive convection

– increased lightning activity (more NOx)

– energy and mass transfer to higher altitudes

– changes in the large scale circulation of the atmosphere: less rain in West Africa, enhanced storm activity in Europe...

• 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!


Focus 1:

Land-atmosphere exchange of carbon and its feedbacks within the Earth System

CO2

MethaneNon-methane VOC


Focus 1: Land-atmosphere exchange of reactive carbon and its feedbacks within the Earth System

Issues:•CO2 fluxes at interlinked scales•Control of interannual variation of CH4 fluxes•Relationship of VOC fluxes to carbon exchange and Net Biome Production•Feedbacks hydrology/aerosols/VOC•Self-regulation of VOC fluxes•In-canopy processes


Focus 2A: Interactions and feedbacks between biogenic/ anthropogenic aerosol production, cloud processes, climate and the water cycle

Issues:•What controls natural CCN abundance?•How do changes in CCN affect the cycles of water, energy, and chemical species•What are the chemical/microphysical effect of carbonaceous aerosols?•Dust aerosols: cloud effects, anthropogenic perturbation•Role of aerosol absorption in climate change•Representation of above processes in climate models


Focus 2B: Role of the biosphere in the self-cleansing mechanisms of the atmosphere

•Role of terrestrial biosphere in self-cleaning (NOx, VOC, …)

•Effects of global change (land-use, climate) on biospheric inputs to self-cleaning

•Effects of changing self-cleaning on biosphere (e.g., via oxidants, UV, …)

ILEAPSFocus 3: Feedbacks and teleconnections in the land surface -

vegetation - water - atmosphere system

•Effects of land-use and vegetation dynamics on climate and hydrology•Interactions of soil moisture with energy and water flux•Are there multiple stable states, and what are the thresholds between them?•Relative importance of human-induced changes (land-use, greenhouse gases, aerosols) on climate•Effects of changing radiation fields

LE = 0.65 R nLE = 0.25 R n

H = 0.3 R n

H = 0.65 R n

BorealForest

TemperateForest

Bio-geophysical feedbacks: Energy Balance Link R n = LE + H + S

0.10 R g

R n = 0.87 R g

0.10 R g

R n = 0.87 R g

S = 0.03 R n

S = 0.07 R n

25 m10 m

PBL1500 m

PBL3000 m

CAPE + cloud activity characteristics

Atmosphere - Biosphere Coupling Principles

1 Convective Boundary Layer (CBL) Effects

Boundary layer structure, including its depth, is directly

influenced by the surface heat and

moisture fluxes

2 Local Wind and Mesoscale Circulation Effects

Local and mesoscale (wind) circulations can subsequently

result from horizontal variations in land surface heat fluxes and the depth of CBL (e.g. sea- and

land breezes)

Local wind circulation lead to

boundary wind convergence, which

lead to increased measures of the

potential for deep cumulus convection

3 Effects on Convective Available Potential Energy (CAPE)

CAPE can considerably

increases/decreases in response to

surface moisture and surface temperature


Focus 4: Land/Atmosphere Exchange - Theory and Tools


Focus 4: Land/Atmosphere Exchange - Theory and Tools

· Night-time and stably-stratified flows · Vegetation canopies and complex terrain· Diurnal patterns and low frequency motions· Dry deposition


Implementation Strategies

· Integrated („LBA-type“ studies) · Integration of results into regional and global models· Long-term measurements (FLUXNET, ...)· Development of scaling techniques

Possible “bridging areas/projects (LAND, ILEAPS, SOLAS, IGAC, …)-FLUXNET, BATREX, alikes..-Integrated studies + hot-spots such as mega-cities, costal-Ecosystem response to BGC-feedbacks in L-A system-(regional) coupled atmospheric-bgc models

bahc-sun set... synthesis volume currently in print; ready october 2003 synthesis papers, science...

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