The Global Carbon Cycle Humans Atmosphere /yr Ocean 38,000 Land 2000 ~90 ~120 7 GtC/yr ~90 About half the CO 2 released by humans is absorbed by oceans and land “Missing” carbon is hard to find among large natural fluxes

In a nutshell About half of the CO 2 emitted by human activities accumulates in the atmosphere The other half is absorbed by “sink” processes on land and in the oceans We lack a quantitative understanding of –Where the sinks are –How they work –How long they’ll keep working –Whether there’s anything we can do to make them work better or for longer

Inverse Modeling of CO 2 Air Parcel Sources Sinks wind Sample Changes in CO 2 in the air tell us about sources and sinks

Simulated Atmospheric CO 2 in 1999

Atmospheric CO 2 Observations ~2000

Atmospheric CO 2 Observations ~2006

Orbiting Carbon Observatory (Planned August 2007 launch) Global observations of fine-scale variations of column mean [CO 2 ] Sunny days only Mid-day only

Scaling Studies Across Ecosystems Mixed Temperate Forest Northern Wisconsin (WLEF-TV) 450 m tower, 5 years of fluxes Radar soundings, aircraft sampling Tropical Forest Central Brazilian Amazon (LBA) 3 sites: intact forest, logged, pasture fluxes, in-situ data, aircraft sampling Semi-arid Grass and Cropland Oklahoma/Kansas border (ARM/CART) 2 flux sites: C4 prairie and C3 wheat Frequent soundings, PBL data Process models evaluated locally against flux towers, aircraft data, and other field measurements, extrapolated using imagery

Nocturnal respiration produces extremely high concentrations in morning stable layer Surface heating and TKE generation causes entrainment of lower-CO 2 air from aloft Photosynthesis depletes CO 2 in surface layer Buoyant plumes of low-CO 2 air fill the convective boundary layer Development of a CO 2 “Mixed Layer” Coupled SiB-RAMS simulation Denning et al, 2002

Possible Sources of Bias in New Obs Surface carbon exchange (biology) covaries with meteorology on many time scales! Diurnal cycle Seasonal cycle Cloud/clearsky bias Unresolved atmospheric transport processes may significantly affect [CO 2 ] mixing ratio PBL entrainment and diurnal pumping Cumulus-scale updrafts and downdrafts Frontal lifting

Orography, rainfall, soils, and ecosystems are interactively organized at finer scales than can be simulated in today’s global climate models

Land-Atmosphere Modeling in CMMAP Current global climate models have a single atmospheric column above each land grid cell [Some (e.g., CCSM) now use non-spatially-explicit, flux-weighted “tiles” of different land-surface types under each atmospheric column] Early MMF experiments reversed this structure: hundreds of atmospheric columns over a single land point Under MMAP, we will run hydrology, ecosystem physiology, and biogeochemistry at the cloud scale! Sampling problem: how will heterogeneity be specified to represent large areas?

Photosynthetic efficiency is very different for direct beam vs diffuse radiation … clouds change both total and partition of solar radiation … photosynthesis rates will respondPhotosynthetic efficiency is very different for direct beam vs diffuse radiation … clouds change both total and partition of solar radiation … photosynthesis rates will respond What happens when rain falls on only part of the grid cell?What happens when rain falls on only part of the grid cell? Does hydrologic preconditioning in the land-surface help structure mesoscale organization of clouds and rainfall?Does hydrologic preconditioning in the land-surface help structure mesoscale organization of clouds and rainfall?

Summary By 2009, we will be swimming in hourly and daily observations of atmospheric CO 2 over terrestrial ecosystems Quantitative interpretation of the new data will be critically dependent on correct representation of cloud-scale transports and their interactions with ecosystems Under CMMAP, we will develop global simulations of the interactions among water, light, and ecosystems at the cloud scale CMMAP can make a huge contribution to Earth System science, way beyond clouds and the hydrologic cycle!