Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009
Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009
复制标题
高纬度火山羽向赤道扩散及其与亚洲夏季风的关系：以2009年萨雷切夫火山喷发为例
DOI：
10.5194/acp-17-13439-2017
复制
发表时间：
2017-11-13
影响因子：
6.3
通讯作者：
Hoffmann, Lars
中科院分区：
文献类型：
--
作者：
Wu, Xue;Griessbach, Sabine;Hoffmann, Lars
热带火山喷发因其对平流层气溶胶负荷和全球气候影响的显着贡献而被广泛研究，但高纬度火山喷发对平流层气溶胶层的影响尚不清楚，气溶胶从高纬度输送到热带平流层的路径也不清楚。在这项工作中，我们重点研究 2009 年 6 月喷发的高纬度火山萨里切夫火山（北纬 48.1 度，东经 153.2 度），以及亚洲夏季风 (ASM) 对火山羽流向赤道扩散的影响。首先，通过大气红外探测器 (AIRS) 的 SO2 观测和使用拉格朗日粒子分散模型大规模并行轨迹计算 (MPTRAC) 的向后轨迹方法来估计萨里切夫喷发的二氧化硫 (SO2) 排放时间序列和羽流高度。然后，使用导出的 SO2 排放时间序列模拟羽流的传输和扩散。将传输模拟与 AIRS 的 SO2 观测进行比较，并通过迈克尔逊被动大气探测干涉仪 (MIPAS) 的气溶胶观测进行验证。 MPTRAC模拟显示，大约4%的硫排放在喷发开始后50天内被输送到热带平流层，羽流通过副热带急流上方的等熵输送向热带对流层顶层（TTL）扩散。 MPTRAC 模拟和 MIPAS 气溶胶数据均表明，在 360 至 400 K 的潜在温度水平之间，赤道输送主要是由北半球夏季 ASM 增强的反气旋 Rossby 波破碎驱动的。火山羽流被反气旋流夹带并到达TTL，同时向西南输送到反气旋下游的深热带地区。此外，ASM反气旋通过隔离ASM内部的“气溶胶孔”来影响气溶胶的路径，该孔被外部富含气溶胶的空气包围。使用位涡梯度方法可以最好地指示这种传输势垒。长期MIPAS气溶胶探测表明，进入TTL后，萨里切夫喷发产生的气溶胶在热带平流层停留了约10个月，并缓慢上升。上升速度与水蒸气录音机的上升速度非常吻合。此外，还对冬季喷发进行了假设的 MPTRAC 模拟。结果表明，在冬季大气环流条件下，副热带急流和波浪破碎事件会抑制羽流向赤道的输送。在这种假设情况下，高纬度火山喷发将无法对热带平流层气溶胶层做出贡献。
Tropical volcanic eruptions have been widely studied for their significant contribution to stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1 degrees N, 153.2 degrees E), which erupted in June 2009, and the influence of the Asian summer monsoon (ASM) on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission time series and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach using the Lagrangian particle dispersion model Massive-Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived SO2 emission time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The MPTRAC simulations show that about 4% of the sulfur emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The MPTRAC simulations and MIPAS aerosol data both show that between the potential temperature levels of 360 and 400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported southwestwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an "aerosol hole" inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of the water vapor tape recorder. Furthermore, a hypothetical MPTRAC simulation for a wintertime eruption was carried out. It is shown that under winter atmospheric circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetical scenario, a high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.