Lightning NO_x influence on large-scale NO_y and O₃ plumes observed over the northern mid-latitudes

Figures & data

Fig. 1 Trace gas measurements along the flight track between Frankfurt and Houston and between 85°W and 40°W, on 13 June 2003. The data were averaged every 0.1°. NO_y (ppbv×100, red line), CO (green), O₃ (black) mixing ratios (ppbv), and PV (pvu×10, pink). Blue dashed lines delimit the stratospheric influence and the black dotted line point out an LSP.

Fig. 2 Scatter plots of MOZAIC O₃ vs. CO mixing ratios collared with simultaneous NO_y mixing ratios during June–July–August 2003 in the UTLS over the American continent. Left: UTLS (Upper Troposphere Lower Stratosphere region, pressure <300 hPa); middle: tropospheric data with remaining stratospheric influence (instant potential vorticity, PVi <2 pvu.); right: tropospheric data (PV <2 pvu. during the 72 hours before observations).

Table 1. Statistics (median, mean and third quartile) of NO_y for the upper tropospheric air masses observed in MOZAIC between 2001 and 2005 for three different regions (North America: 30°N-60°N/120°W-60°W, Atlantic: 0°N-60°N/60°W-25°W, and Europe: 35°N-70°N/25°W-40°E)

Season (number of flights)	NOy (ppb)	North America	Atlantic	Europe
DJF (490)	Median	0.24	0.25	0.23
	Mean	0.29	0.28	0.25
	Third quartile	0.38	0.35	0.31
MAM (407)	Median	0.75	0.65	0.56
	Mean	0.95	0.80	0.61
	Third quartile	1.20	1.05	0.78
JJA (467)	Median	1.22	0.80	0.88
	Mean	1.28	0.89	0.98
	Third quartile	1.60	1.13	1.25
SON (321)	Median	0.51	0.43	0.42
	Mean	0.56	0.47	0.45
	Third quartile	0.70	0.61	0.56

Table 2. Statistics (median, mean and third quartile) of CO for the upper tropospheric air masses observed in MOZAIC between 2001 and 2005 for three different regions (North America: 30°N-60°N/120°W-60°W, Atlantic: 0°N-60°N/60°W-25°W, and Europe: 35°N-70°N/25°W-40°E)

Season	CO (ppb)	North America	Atlantic	Europe
DJF	Median	98	94	99
	Mean	100	98	102
	Third quartile	111	108	112
MAM	Median	115	109	115
	Mean	116	109	115
	Third quartile	125	117	125
JJA	Median	95	90	93
	Mean	96	91	94
	Third quartile	105	102	103
SON	Median	86	84	87
	Mean	87	86	88
	Third quartile	94	93	94

Fig. 3 Frequency distributions of the horizontal extent of the NO_y lightning-related plumes (see Sections 3.2 and 3.3) observed in JJA over the regions NAM, ATL, and EU.

Fig. 4 Seasonal variations (DJF, MAM, JJA and SON) of the frequency distribution (box and whisker plots) of NO_y for plumes with a horizontal extent <300 km (left) and within the LSPs of >300 km (right) for the three different regions (NAM, ATL and EU). Boxes: interquartile range (Q1 and Q3); red line: median; whiskers: 5th and 95th percentiles.

Fig. 5 Convective origin below 3 km and between 9 and 12 km of a 6 d integration of the transatlantic NO_y LSPs as calculated with the FLEXPART model, with a horizontal resolution of 1°×1°, as the normalised residence time (normalised to (1) the cumulative residence time and (2) the fraction of flights recording transatlantic LSPs against total number of MOZAIC flights, for both over each season) in% (a), the occurrence of the IR brightness temperature <220 K in% observed by GOES (b) and the distribution of lightning flashes observed by NLDN (c). NLDN and GOES observations are sampled at the same time and location as the FLEXPART model. Parameters are represented over seasons (top: MAM, middle: JJA, bottom: SON).

Fig. 6 Number of NO_y LSPs identified for the different seasons (DJF, MAM, JJA, SON) over the regions NAM, ATL, EU, AFR and ASIA using the criteria described in Sections 3.2 and 3.3.

Table 3. Seasonal distribution of the LSPs (top) and origin of the convection (bottom)

Season	DJF	MAM	JJA	SON
Number of observed LSPs	5	38	41	43
Origin
Western Atlantic Basin	2	22	25	16
Europe/Mediterranean Sea	3	16	13	20
Africa			3	5
Asia				2
Type of convection
Continental	0	30	31	24
Maritime	5	8	10	19

Fig. 7 Origin of the NO_y LSPs as calculated with the FLEXPART model with a horizontal resolution of 1°×1°, for the four seasons over the North mid-latitudes (20°N–70°N). Colours represent the normalised residence time (normalised to (1) the cumulative residence time and (2) the fraction of flights recording LSPs against total number of MOZAIC flights, both over each season) of the particles initialised inside each LSP in the 0–3 km (LT) and 9–12 km (UT) layers during the 6 d backward simulation. The three black rectangles in the upper left panel define the study areas.

Fig. 8 Seasonally averaged NO_y mixing ratios (ppbv) in the LSPs determined as described in Section 3. Values are averaged over 1°latitude×1°longitude and for each season over the North mid-latitudes.

Fig. 9 Frequency distributions (box and whisker plots) of NO_y, O₃ and CO in the transatlantic LSPs for the three different regions (NAM, ATL, EU) during spring (MAM), summer (JJA) and autumn (SON). Boxes: interquartile range (Q1 and Q3); red line: median; whiskers: 5th and 95th percentiles.