Abstract
Nitrous oxide (N2O) is a potent and long-lived greenhouse gas that contributes to global warming with a global warming potential (GWP) 298 times that of carbon dioxide (CO2). In this paper, we analyzed the trend of N2O concentration in vertical layers of the stratosphere from 2005 to 2020 using the N2O observed from the Microwave Limb Sounder (MLS) that is on board the Aura satellite. We found that the local N2O concentration showed a downward trend in the lower stratosphere but rose or fluctuated in the upper stratosphere. The reduction reached −5 ppb/yr at pressure levels of 31.62 hPa and 68.13 hPa, with a confidence level of over 90%. The growth was around 1–2 ppb/yr in the upper stratosphere. In addition, a concentration anomaly was observed in the tropical stratosphere in 2013. After the appearance of this anomaly, the N2O concentration in the middle and lower layers of the tropical stratosphere was lower than before 2013. We speculated that the enhancement of the Brewer–Dobson circulation (BDC) upwelling before and after stratospheric sudden warming (SSW) is the main reason for the abnormal concentration distribution in 2013. Stratospheric N2O has changed significantly in the past 16 years with the mutual coupling effect of BDC and SSW and such changes can have further impact on the chemical equilibrium and radiation balance in the stratosphere, as well as on the persistent climate-warming trend.
Highlights
Received: 26 December 2021As one of the most important greenhouse gases, nitrous oxide (N2 O) has a global warming potential (GWP) 298 times that of carbon dioxide (CO2 ) on a per-molecule basis [1].N2 O is mainly produced as a by-product of microbial nitrification and denitrification in soil and the ocean [1,2]
We found that the N2 O concentration showed a downward trend in the lower stratoWe but found the N2O concentration showed a downward trend the mean lower of stratsphere rosethat or fluctuated in the upper stratosphere
We found that the N2 O concentration showed a downward trend in the lower stratosphere but rose or fluctuated in the upper stratosphere
Summary
Received: 26 December 2021As one of the most important greenhouse gases, nitrous oxide (N2 O) has a global warming potential (GWP) 298 times that of carbon dioxide (CO2 ) on a per-molecule basis [1].N2 O is mainly produced as a by-product of microbial nitrification and denitrification in soil and the ocean [1,2]. As one of the most important greenhouse gases, nitrous oxide (N2 O) has a global warming potential (GWP) 298 times that of carbon dioxide (CO2 ) on a per-molecule basis [1]. Due to the use of nitrogen-containing fertilizers in agricultural production, the tropospheric volume mixing ratio (VMR) of N2 O increased by 20%, from 270 ppb in pre-industrial times to 324 ppb in 2011 [3]. In the context of global warming, controlling N2 O is regarded as a crucial part of controlling the greenhouse effect [4]. Resulting from the globe’s extensive use of synthetic nitrogen fertilizer, global human-induced emissions have increased by 30% over the past four decades and exceeded all the shared socioeconomic pathways (SSPs) described in the sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC) [5]
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