A year of H₂ measurements at Weybourne Atmospheric Observatory, UK

Figures & data

Fig. 1.  Map showing the location of Weybourne Atmospheric Observatory (red star). Major centres of H₂ production (four facilities and over) in the UK and the Benelux region are highlighted using semi-transparent red circles. Map Source: Google Maps.

Fig. 2.  Example of RGA3 non-linearity results for July 2008. ‘H₂ expected’ is the mixing ratio expected from a linear relationship determined from a single point calibration and this point lies on the dashed line.

Fig. 3.  Time series of H₂ measured at Weybourne for period March 2008–February 2009. Note the change in axis scale above 800 ppb. The red markers represent the background H₂ estimated in Section 3.1.

Fig. 4.  Monthly means and medians of H₂ and CO at Weybourne. The lines represent sine wave fits to the mean values.

Fig. 5.  Hourly means for H₂ mixing ratio and hourly means for irradiance at Weybourne for MAM, JJA, SON and DJF. Error bars represent±one sigma standard deviation of the hourly mean H₂ mixing ratio.

Fig. 6.  Wind rose showing the distribution of ΔH₂ for (a) all positive ΔH₂ and (b) data above a ΔH₂ of 40 ppb. Radial axis represents probability and the legends show mixing ratio ranges colour coded. A wind rose showing the wind distribution is shown on each panel in black.

Fig. 7.  ΔH₂ vs. ΔCO for all data collected between March 2008 and February 2009. Dashed boxes labelled 1 and 2 correspond to event 1 and event 2 in Section 3.6, respectively. Note the change in scale on y-axis above 300 ppb H₂.

Fig. 8.  ΔH₂ vs. ΔCO in each of four seasons for elevated ΔH₂ (≥10 ppb) and also filtered for polluted conditions (NO_x>5 ppb). ΔH₂ values above 150 ppb have been excluded as these belong almost exclusively to the periods of anomalously high H₂ (i.e. corresponding to boxes 1 and 2 in Fig. 7). Regression analysis was performed for the data where NO_x was above 5 ppb NO_x. The dashed lines in each panel represent ΔH₂/ΔCO ratios of approximately 0.36 to 0.6, which are representative of near-source vehicle emission ratios reported in the literature (see text in Section 3.5).

Fig. 9.  NAME back-maps showing surface exposure (0–100 m) for air arriving at Weybourne between (a) 06:00 and 09:00 on the 5 July 2008 and (b) 03:00 and 06:00 on the 5 February 2009. The percentage of total air mass is the fraction of the 30 000 particles released that are detected in each 0.05°×0.05° grid box during the 2 d prior to the release.

Fig. 10.  H₂ deposition events used to estimate H₂ deposition velocity for (a) 11–17 June 2008 and (b) 25–30 July 2008. Events used are highlighted using blue transparent rectangles.

Fig. 11.  RASS potential temperature for the H₂ deposition events used to estimate H₂ deposition velocity for (a) 11–17 June 2008 and (b) 25–30 July 2008. Black circles represent the nBL heights estimated from O₃ deposition in Section 3.7 and corresponding to the blue transparent rectangles shown in Fig. 10.

Table 1. Comparison of H₂ deposition velocity estimates using a ‘top-down’ approach

Environment	H2 deposition velocity (×10^−4 m s^−1)	Method	Citation
Boreal forest	7.3±1.5 (0.9–5.6)	Concentration gradients	Rahn et al. (2002)
Urban	0.5–1^a	Nocturnal H2 decay	Steinbacher et al. (2007)
Rural	1.5 (0–0.33)	Concentration gradients	Constant et al. (2008)
Urban	3±0.7 (2.3–3.7)	Radon tracer	Hammer and Levin (2009)
Urban	2.4±1.3 (0–5.1)	Radon tracer	Yver et al. (2009)
Urban	2.2 (0.9–5.7)	Nocturnal H2 depletion and calculated BL heights	Grant et al. (2010a)
Rural/coastal	2.6^b	Ozone box	Simmonds et al. (2000)
	5.3±1.6 (1.8–12.9)	Ozone box	Simmonds et al. (2011)
Urban	1.3–7^a	Radon tracer	Lallo et al. (2009)
Rural/coastal	3.5±0.7 (2.7–4.4) (June 2008)	Ozone box	This work
	1.9±1 (1.3–3.2) (July 2008)

^aNo mean value reported.

^bNo range reported.

Fig. 12.  H₂, CO, O₃, NO, NO₂ and wind direction for the period of strong northerly flow observed during May 2008. The dashed lines numbered 1–4 correspond to number air-mass trajectory maps numbered 1–4 shown in Fig. 13.

Fig. 13.  Ten-day NAME back-maps showing the probability of surface influence (0–1000 m) for 12:00–14:00 h for 15 May 2008 (top left), 16 May 2008 (top right), 20 May 2008 (bottom left) and 23 May 2008 (bottom right).

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