C. sampling strategy D. source configuration F. source-receptor matrix I. estimation of fluxes J. strategy evaluation uncertainty G. concentration pseudo-data H. inversion (16) fluxes noise E. influence functions B. LPD simulation A. meteorological simulation Figure 1: Modeling framework to evaluate sampling strategies

Figure 2. Approximation of diurnal variations of CO 2 flux with assimilation (A-tracer) and respiration (R-tracer) fluxes

CWCW 1000 km x z D q samples DDD q0q0 Figure 3: Configuration of inversion experiments

Figure 4: Concentrations at different heights within the PBL as a function of sampling time for two area sources with the upwind stretch D=100 km (left) and 1000 km (right): R- and A-tracers with a unit emission rate (top and middle), and CO 2 -tracer (bottom)

Figure 5. Influence functions of surface fluxes derived for tracer concentration samples taken at different times of day (third day of meteorological simulation) at height of 400m: (a) R-tracer, (b) A-tracer (contour values: 1, 5, 10, 50, 100 x m -3 s)

Figure 6: Crosswind integrated influence functions for the upwind tracer flux for the concentration samples taken during 24 hours at the height of 50 m (left) and 1050 m (right) at the distance D= 100km (top) and D=500km (bottom) from the upwind boundary (contour values: 0.01, 0.02, 0.05, 0.075, 0.1, 0.2 m -1 ).

Figure 7: Root mean square error (normalized by flux) of R-, A-, and net CO 2 flux estimation using vertical aircraft profiles at different times of day as a function of the source area size (no inflow flux)

Figure 8: Estimation errors, E 1 and E 2, for the net CO 2 flux using different amount of concentration data from two tall towers

Figure 9: Root mean square error (normalized by flux) of R and A fluxes estimation from R- and A-tracer concentration data respectively (left) and from CO 2 data (right) using 24 hour time concentration series from a tall tower with the estimation of inflow flux.

Figure 10: Estimation of R, A, and net CO 2 flux from 200 km source area using 24 hour time concentration series from two towers with the estimation of inflow flux: two 400m towers (top), 400m and 30m towers (middle), and two 30m towers (bottom).

Figure 11: Estimation of R and A surface fluxes from a series of source areas using a single tall tower data: R- and A- tracer concentrations correspondingly (top), CO 2 concentration (bottom)