Sensitivity of CO₂ and CH₄ Annual Cycles to Different Meteorological Variables at a Rural Site in Northern Spain

Table 3

Differences between average concentrations calculated with observations selected for different boundary layer thresholds and the annual cycle for daytime observations. Availabilities and days without observations (gaps) are also included.

Type of test	Boundary layer height threshold (m)	Availability (%)	Gap (days)	CO2 difference		CH4 difference
				ppm	%	ppm	%
Above	500	64.6	15	−1.8	−0.45	−0.009	−0.48
	600	56.8	27	−2.0	−0.51	−0.010	−0.53
	700	48.9	47	−2.2	−0.56	−0.011	−0.58
	800	41.7	72	−2.5	−0.63	−0.012	−0.65
	900	35.1	94	−2.8	−0.70	−0.013	−0.67
	1000	28.5	126	−3.1	−0.79	−0.014	−0.76
Below	300	13	79	7.3	1.85	0.026	1.37
	400	20.9	12	6.3	1.60	0.023	1.22
	500	29.2	1	4.9	1.24	0.018	0.96
	600	37.1	1	3.8	0.97	0.015	0.77
	700	44.9	0	3.0	0.75	0.012	0.61
	800	52.1	0	2.4	0.60	0.009	0.50