Seasonal variation of methane, water vapor, and nitrogen oxides near the tropopause: Satellite observations and model simulations

Abstract

[1] Seasonal variations of several trace constituents near the tropopause are analyzed based on satellite measurements, and results are compared to a recent numerical model simulation. We examine methane, water vapor, and nitrogen oxides (NO x ) derived from Halogen Occultation Experiment (HALOE) satellite observations; these species have strong gradients near the tropopause, so that their seasonality is indicative of stratospheretroposphere exchange (STE) and circulation in the near-tropopause region. Model results are from the Model for Ozone and Related Chemical Tracers (MOZART) stratospheretroposphere chemical transport model (CTM). Results show overall good agreement between observations and model simulations for methane and water vapor, whereas nitrogen oxides near the tropopause are much lower in the model than suggested by HALOE data. The latter difference is probably related to the lightning and convective parameterizations incorporated in MOZART, which produce NO x maxima not near the tropopause, but in the upper troposphere. Constituent seasonal variations highlight the imporatance of the Northern Hemisphere (NH) summer monsoons as regions for transport into the lowermost stratosphere. In MOZART, there is clear evidence that air from the monsoon region is transported into the tropics and entrained into the upward BrewerDobson circulation, bypassing the tropical tropopause.

Greenhouse gas relationships in the Indian summer monsoon plume measured by the CARIBIC passenger aircraft

“…These observations were explained to be due to convective uplifting of boundary layer air in the monsoon region (Randel and Park, 2006) and were shown to be in agreement with model results, for example from the MOZART model. Simulations predicted high mixing ratios of CH 4 in the anticyclone between 60 • E and 120 • E around 30 • N at pressure altitudes between 300 and 100 hPa, as well as elevated levels of H 2 O and NO x , in accordance with observations from the HALOE instrument (Park et al, 2004). The model also calculated a CO maximum at ∼15 km altitude, in agreement with MLS and ACE-FTS measurements (Park et al, 2009).…”

“…High summer time mixing ratios over South Asia were reported for CO (Fu et al, 2006;Park et al, 2008), for H 2 O (Park et al, 2004;Fu et al, 2006;Randel and Park, 2006), and for CH 4 (Park et al, 2004;Schneising et al, 2009;Xiong et al, 2009). Other trace gases that were observed to be enhanced in the monsoon region included NO x (Park et al, 2004), HCN, C 2 H 6 , and C 2 H 2 (Park et al, 2008). In addition, a concomitant decrease of O 3 was observed (Randel and Park, 2006;).…”

“…Satellite instruments, despite their limited vertical resolution, can also provide information on the altitude range of the observed tracer enhancements. The observed monsoon plume in CH 4 is for example reported by the AIRS instrument to be situated in the altitude interval from 500 hPa to 150 hPa (Xiong et al, 2009), the MOZART model predicts a vertical extension from ∼300-150 hPa (Park et al, 2004).…”

Reconstructing terrestrial nutrient cycling using stable nitrogen isotopes in wood

“…Differences can even exist among power plants depending on the type of catalytic reduction employed (Felix et al 2012). Pollutant δ 15 N values may also vary between the point source emission value and the broader N deposition footprint after NOx experiences atmospheric alteration (Freyer et al 1993) and transboundary pollution transport (Park et al 2004, Schaub et al 2005. For example, 15 NOx near a motorway can reach values up to +2 to +8 ‰ (Ammann et al 1999), despite the low signature of emissions straight from the tailpipe.…”

Validation of Tropospheric Emission Spectrometer ozone profiles with aircraft observations during the Intercontinental Chemical Transport Experiment–B

“…An overview of the TES retrieval algorithm and error estimation are discussed by Bowman et al [2002] and Worden et al [2004], and the characterization of errors and vertical information for individual TES profiles are discussed by Kulawik et al [2006]. TES ozone retrievals use a priori information from a climatology developed using the MOZART model [Brasseur et al, 1998;Park et al, 2004]. The vertical resolution of TES nadir ozone profiles is about 6 km in cloud-free conditions [Bowman et al, 2002;Worden et al, 2004].…”