Nitrogen oxides in the global upper troposphere: interpreting cloud-sliced NO<sub>2</sub> observations from the OMI satellite instrument

Abstract

Abstract. Nitrogen oxides (NOx≡NO+NO2) in the upper troposphere (UT) have a large impact on global tropospheric ozone and OH (the main atmospheric oxidant). New cloud-sliced observations of UT NO2 at 450–280 hPa (∼6–9 km) from the Ozone Monitoring Instrument (OMI) produced by NASA and the Royal Netherlands Meteorological Institute (KNMI) provide global coverage to test our understanding of the factors controlling UT NOx. We find that these products offer useful information when averaged over coarse scales (20∘×32∘, seasonal), and that the NASA product is more consistent with aircraft observations of UT NO2. Correlation with Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) satellite observations of lightning flash frequencies suggests that lightning is the dominant source of NOx to the upper troposphere except for extratropical latitudes in winter. The NO2 background in the absence of lightning is 10–20 pptv. We infer a global mean NOx yield of 280±80 moles per lightning flash, with no significant difference between the tropics and midlatitudes, and a global lightning NOx source of 5.9±1.7 Tg N a−1. There is indication that the NOx yield per flash increases with lightning flash footprint and with flash energy.

Midlatitude Lightning NOx Production Efficiency Inferred From OMI and WWLLN Data

“…The Allen et al tropical results do not provide compelling evidence of a systematic difference in PE between the tropics and midlatitudes, since the error bars in theirs and the present study have significant overlap. This conclusion was also reached by Marais et al (), who obtained a relatively large PE of 280 mol/fl. However, their use of climatological NO 2 data from cloud slicing and an OTD/LIS lightning climatology in constraining the GEOS‐Chem model differs from the present study and complicates direct comparisons with our results.…”

Lightning NOx Production in the Tropics as Determined Using OMI NO2 Retrievals and WWLLN Stroke Data

“…Since LNO x PE is related to flash energy (Wang et al, ), Beirle et al () state that it is likely that LNO x PE is higher at locations where the flash radiance is large (i.e., the Mediterranean, the Pacific downwind from Australia, and the eastern United States) and is lower at locations where the flash radiance is small (i.e., central Africa and India). Marais et al () used the Beirle et al data set to examine the relationship between cloud‐slicing derived estimates of PE from OMI and flash energy, duration, and footprint and found correlations of 0.40, 0.25, and 0.50, respectively. The results from this study also support the hypothesis that LNO x PE is correlated with flash energy, as PE is found to lower over continental locations than over marine locations.…”

“…Recent satellite‐based estimates of LNO x production efficiency (LNO x PE) include 33–50 mol per flash (Beirle et al, ), 87–246 mol per flash (Bucsela et al, ), and 80 ± 45 mol per flash (Pickering et al, ). Marais et al () used a cloud‐slicing technique (Choi et al, ; Ziemke et al, ) to estimate upper tropospheric (UT) NO 2 from the Ozone Monitoring Instrument (OMI) and then used the relationship between seasonal mean OTDLIS flashes and seasonal mean UT NO 2 from OMI and version 10‐01 of the GEOS‐Chem CTM to estimate LNO x PE. They obtained a PE of 280 ± 80 mol per flash.…”

Global Occurrence and Chemical Impact of Stratospheric Blue Jets Modeled With WACCM4

“…Nault et al () results indicate higher LNO x in the midlatitudes than in the tropical regions, in agreement with Schumann and Huntrieser (). However, the latest estimations of the global lightning NO x emissions by new cloud‐sliced observations of UT NO 2 in the 6–9 km range from the Ozone Monitoring Instrument of the Aura mission combined with the GEOS‐Chem model point to a global lightning NO x source of 5.5 Tg N/year (Marais et al, ). Marais et al () reports no significant difference in LNO x production per flash between the tropics and midlatitudes.…”

“…However, the latest estimations of the global lightning NO x emissions by new cloud‐sliced observations of UT NO 2 in the 6–9 km range from the Ozone Monitoring Instrument of the Aura mission combined with the GEOS‐Chem model point to a global lightning NO x source of 5.5 Tg N/year (Marais et al, ). Marais et al () reports no significant difference in LNO x production per flash between the tropics and midlatitudes. Stratospheric NO can cause ozone depletion through the processes (Crutzen, ) …”