A look at synoptic CO2 in the midlatitudes and tropics using continuous CO2 observations and Transcom continuous results Nicholas Parazoo Transcom 2008 June 2-5
Scales of Variation Diurnal Synoptic Seasonal
Three Stories Mechanisms controlling synoptic variations of [CO2] in the tropics vs midlatitudes Transcom continuous results and continuous observations from North America, South America, and Europe suggest choice of land surface model can be important control on day-to-day variability Cold fronts important source of variability in midlatitudes
Data Continuous [CO2] Observations in North America, South America, and Europe Hourly station output from Transcom Continuous experiment using hourly SiB and 3-hourly CASA from 2002-2003
Variance strongest over continents, generally during growing season Magnitude of day-today variations at tropical site as large as midlatitude sites, but weather is Mid-afternoon [CO 2 ] (left axis) Monthly Standard Deviation (right axis)
Synoptic Variability in Midlatitudes and Tropics In tropics, primary energy source is due to latent heat release associated with convective cloud systems Strong vertical mixing In midlatitudes, large store of zonal mean available potential energy, which becomes baroclinically unstable and waves develop to transport heat poleward Strong horizontal mixing
CO 2 Budget C + RT { t p z 123 1 i ii F c C + K m 123 z iii + W C { z iv + V H H C 14 2 34 + g MC p v 123 vi = 0 Source/Sink Transport i. Time rate of change of [CO 2 ] ii. iii. iv. F c = Surface Flux of CO 2, z i = lowest model level (~50m), K m = eddy diffusivity C = [CO 2 ], M = Cloud Mass Flux, W = vertical wind, V H = horizontal wind Biogenic, fossil fuel, and oceanic flux Turbulent diffusion Vertical advection v. Horizontal advection vi. Convective mixing For boundary layer budget, all terms solved for within lowest 500 meters (~ lowest 3 model layers)
Transport Simulations Using PCTM 1.25x1deg GEOS4
Monthly Standard Deviation of Midday CO2 ppm Observations CONTROL NOCLOUD NOFLUX ppm/hr Monthly Mean Hourly CO 2 Budget for CONTROL Horizontal Advection Convective Mixing Midlatitudes Tropics Annual Mean Percentage
Continental/Midlatitude Monthly Mean Hourly CO 2 Budget for CONTROL Horizontal Advection Convective Mixing Vertical Advection Surface Flux Tropical Island/Coastal
Standard Deviation Midday CO2 Hourly Budget Observations Transcom Average (SiB) Transcom Average (CASA) Transport Surface Flux
Model and Site Evaluation Use taylor plots to show correlation and model standard deviation across each forward model For site evaluation, calculate average model response at each site and compare to other sites For model evaluation, calculate average signal for all sites for each model, compare to other models
ALT BRW CDL Model SiB CASA FRD HEI HUN
LEF MHD PAL SiB CASA SBL SGP Model
Frontal Signals Create CO2 climatology for midlatitude sites using continuous observations and PCTM driven by SiB Identify frontal events and average together, compare model to observations Create model average climatology driven by SiB and CASA
Frontal Identification ρ (water vapor) wind direction pressure GGρ Cold Front!
Summer Frontal CO 2 Climatology o-o-o Observations (left axis) Transport Model (left) Fraction of Horizontal Advection (right) July Mean Surface Flux Transient spikes and air mass replacement characterize frontal variations
Summer Frontal CO 2 Climatology: Transcom Models SiB+FF+Taka CASA+FF+Taka
Summer Frontal CO 2 Climatology: Transcom Models Observations SiB CASA
Winter Frontal CO 2 Climatology: Transcom Models SiB+FF+Taka CASA+FF+Taka
Winter Frontal CO 2 Climatology: Transcom Models Observations SiB CASA
Deformational Flow PCTM [CO 2 ] at 50m shear deformation - tracer field rotated by shear vorticity + stretching deformation - tracer field deformed by stretching = Clouds!
Courtesy of Kathy Corbin
Conclusions Midlatitudes: Synoptic variations of CO 2 dominated by horizontal mixing Tropics: Synoptic variations dominated by vertical mixing Transcom models give different magnitudes and seasonality of synoptic variability transport and surface flux important Cold fronts contain strong variations hidden by clouds
NOAA GMD CarboEurope Special Thanks!
Monthly Standard Deviation of Midday CO2 Observations CONTROL NOCLOUD NOFLUX Monthly Mean Hourly CO 2 Budget for CONTROL Horizontal Advection Convective Mixing