- 著者
- CHANDRA Naveen PATRA Prabir K. BISHT Jagat S. H. ITO Akihiko UMEZAWA Taku SAIGUSA Nobuko MORIMOTO Shinji AOKI Shuji JANSSENS-MAENHOUT Greet FUJITA Ryo TAKIGAWA Masayuki WATANABE Shingo SAITOH Naoko CANADELL Josep G.
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- pp.2021-015, (Released:2020-12-04)
- 被引用文献数
- 38
Methane (CH4) is an important greenhouse gas and plays a significant role in tropospheric and stratospheric chemistry. Despite the relevance of methane (CH4) in human-induced climate change and air pollution chemistry, there is no scientific consensus on the causes of changes in its growth rates and variability over the past three decades. We use a well-validated chemistry-transport model for simulating CH4 concentration and estimation of regional CH4 emissions by inverse modelling for the period of 1988-2016. The control simulations are performed using a seasonally varying hydroxyl (OH) concentrations and assumed no interannual variability. Using inverse modelling of atmospheric observations, emission inventories, a wetland model, and a δ13C-CH4 box model, we show that reductions in emissions from Europe and Russia since 1988, particularly from oil-gas exploitation and enteric fermentation, led to decreased CH4 growth rates in the 1990s. This period was followed by a quasi-stationary state of CH4 in the atmosphere during the early 2000s. CH4 resumed growth from 2007, which we attribute to increases in emissions from coal mining mainly in China and intensification of ruminant farming in tropical regions. A sensitivity simulation using interannually varying OH shows that regional emission estimates by inversion are unaffected for the mid- and high latitude areas. We show that meridional shift in CH4 emissions toward the lower latitudes and the increase in CH4 loss by hydroxyl (OH) over the tropics finely balance out, which keep the CH4 gradients between the southern hemispheric tropical and polar sites relatively unchanged during 1988-2016. The latitudinal emissions shift is confirmed using the global distributions of the total column CH4 observations by satellite remote sensing. There is no evidence of emission enhancement due to climate warming, including the boreal regions, during our analysis period. These findings highlight key sectors for effective emission reduction strategies toward climate change mitigation.
- 著者
- YAMASHITA Yousuke TAKIGAWA Masayuki GOTO Daisuke YASHIRO Hisashi SATOH Masaki KANAYA Yugo TAKETANI Fumikazu MIYAKAWA Takuma
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- pp.2021-014, (Released:2020-12-02)
- 被引用文献数
- 3
Atmospheric transport of aerosols such as black carbon (BC) affects the absorption/scattering of solar radiation, precipitation, and snow/ice cover, especially in areas of low human activity such as the Arctic. The resolution dependency of simulated BC transport from Siberia to the Arctic, related to the well-developed low-pressure systems in September, was evaluated using the Nonhydrostatic Icosahedral Atmospheric Model–Spectral Radiation Transport Model for Aerosol Species (NICAM-SPRINTARS) with fine (∼ 56 km) and coarse (∼ 220 km) horizontal resolutions. These low-pressure systems have a large horizontal scale (∼ 2000 km) with the well-developed central pressure located on the transport pathway from East Asia to the Arctic through Siberia. The events analysis of the most developed low-pressure system in recent years indicated that the high-BC area in the Bering Sea observed by the Japanese Research Vessel Mirai in September 26-27th, 2016 moved to the Arctic with a filamental structure from the low's center to the behind of the cold front and ahead of the warm front in relation to its ascending motion on September 27-28th, 2016. The composite analysis for the developed low-pressure events in September from 2015-2018 indicated that the high-BC area was located eastwards of the low's center in relation to the ascending motion over the low's center and northward/eastward area. Since the area of the maximum ascending motion has a small horizontal scale, this was not well simulated by the 220-km experiment. The study identified the transport of BC to the Arctic in September is enhanced by the well-developed low-pressure systems. The results of transport model indicate that the material transport processes to the Arctic by the well-developed low-pressure systems are enhanced in the fine horizontal resolution (∼ 56 km) models relative to the coarse horizontal resolution (∼ 220 km) models.