17:15 〜 18:45
[AAS10-P07] ACE-FTSデータを用いた成層圏水蒸気増加に対するメタン酸化寄与の影響の検討
Water vapor is the most important greenhouse gas in the troposphere and plays a key role in determining the radiative cooling effect in the stratosphere. In January 2022, Hunga Tonga-Hunga Ha‘apai eruption injected tropospheric water vapor into the stratosphere, reaching a maximum of 10ppmv, and this led decrease of the stratospheric temperature by 3 K. The global satellite observations by Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) have confirmed an increase of approximately 0.3ppmv from 2004 to 2020. The following two processes mainly contribute to produce stratospheric water vapor: one is the transportation of tropospheric water vapor, and the other is the oxidation of stratospheric methane and hydrogen (Net: CH4 + 2O2 → 2H2O + CO2, H2 + OH → H2O + O). Atmospheric methane is increasing by approximately 0.1ppmv and 60% of global methane emissions is attributed to human activity. In this study, we investigated the contribution of methane oxidation to the increase of stratospheric water vapor globally using ACE-FTS data including deuterium isotopologues (HDO and CH3D) observations.
We used the version 5.2 data of ACE-FTS onboard the satellite SCISAT-1 developed by the Canadian Space Agency. ACE-FTS observes the absorption of solar radiances by molecules in the atmosphere: i.e, solar occultation method. ACE-FTS continues observing since February 2004, in the altitude range of 5 – 150 km, with the vertical resolution of 2 – 6 km. The wavenumber range of ACE-FTS observation is 750 – 4400 cm-1, with the spectral resolution of 0.02 cm-1. ACE-FTS simultaneously observes atmospheric molecules such as H2O, CH4, HDO, CH3D, and so on.
We extracted a region where the increase of stratospheric water vapor is controlled only by methane oxidation (methane oxidation region). We conducted the data screening by extracting observations only from a common orbit of all four molecules (H2O, CH4 and their deuterium isotopologues), and removing outliers occurred during the retrieval processes. The numbers of data changed from about 14 million to 13 million by the data screening. We divided data into four seasons: winter (December, January and February), spring (March, April and May), summer (June, July and August) and autumn (September, October and November). The ratio of ΔH2O/ΔCH4 and ΔHDO/ΔCH3D was derived for all ACE-FTS methane and water observations in all areas delimited by 5° latitude and 1 km altitude to extract the region which the increase of stratospheric water vapor controlled by only methane oxidation.
We found the latitude and altitude distribution of the methane oxidation region in each season. We will present details of their distribution and discuss the effects of photolysis, transport, and chemical reactions in the atmosphere.
We used the version 5.2 data of ACE-FTS onboard the satellite SCISAT-1 developed by the Canadian Space Agency. ACE-FTS observes the absorption of solar radiances by molecules in the atmosphere: i.e, solar occultation method. ACE-FTS continues observing since February 2004, in the altitude range of 5 – 150 km, with the vertical resolution of 2 – 6 km. The wavenumber range of ACE-FTS observation is 750 – 4400 cm-1, with the spectral resolution of 0.02 cm-1. ACE-FTS simultaneously observes atmospheric molecules such as H2O, CH4, HDO, CH3D, and so on.
We extracted a region where the increase of stratospheric water vapor is controlled only by methane oxidation (methane oxidation region). We conducted the data screening by extracting observations only from a common orbit of all four molecules (H2O, CH4 and their deuterium isotopologues), and removing outliers occurred during the retrieval processes. The numbers of data changed from about 14 million to 13 million by the data screening. We divided data into four seasons: winter (December, January and February), spring (March, April and May), summer (June, July and August) and autumn (September, October and November). The ratio of ΔH2O/ΔCH4 and ΔHDO/ΔCH3D was derived for all ACE-FTS methane and water observations in all areas delimited by 5° latitude and 1 km altitude to extract the region which the increase of stratospheric water vapor controlled by only methane oxidation.
We found the latitude and altitude distribution of the methane oxidation region in each season. We will present details of their distribution and discuss the effects of photolysis, transport, and chemical reactions in the atmosphere.