Study on atmosphere-ocean interaction through marine biogehic sulfur compounds (dimethylsulfide)

在该项目的资助下，我们完成了以下工作：（1）开发大气DMS自动测量系统;（2）在春、冬季对北太平洋西部海域和大气中DMS进行测量;（3）在八丈岛建立观测站，获得大气DMS的时间序列。此外，还利用等熵轨迹分析法分析了气溶胶的输送路径，并通过分析气溶胶的化学成分来检测海洋大气中的Kosa粒子和DMS的氧化产物。为了获得该海域叶绿素a的分布特征，利用SeaWiPs卫星遥感叶绿素a数据，结合表层海水和大气中DMS浓度、SST和风速估算了该海域海-气DMS通量。分析了海-气DMS通量与大气DMS丰度的关系，结果表明，该地区春季海水DMS含量比12月高1.5倍。来自SeaWiES的叶绿素a浓度也高于4月比12月。这些结果是由于春季海洋生产增加。此外，在1 ~ 2d内，从叶绿素a高值区输送的气溶胶中MSA和非海盐硫酸盐浓度较高。根据柱模型分析，气溶胶中DMS浓度升高的主要原因是在叶绿素a升高区DMS的高排放和高臭氧条件下DMS的快速氧化。虽然在这些观测中观察到了科萨事件，但我们没有成功地获得足够的数据来显示科萨对海洋生产的影响。

With support of this grant-in-aid, we performed following terms ; (1) development of automatic measurement system of atmospheric DMS, (2) measurement of DMS in the seawater and atmosphere over the western North Pacific in spring and winter, (3) setting up an observation station at Hachijojima Island to obtain time series of atmospheric DMS. In addition, analysis of transport pathway of air parcel by an isentropic trajectory Analysis was also performed, and we analyzed aerosol chemical compositions to detect the Kosa particle and oxidation products of DMS in the marine air. Moreover to obtain the distribution of chlorophyll-a in this area, remote sensing chlorophyll-a data derived from SeaWiPs satellite was analyzed.Sea-air DMS flux was estimated with DMS concentrations in the surface seawater and atmosphere, SST and surface wind speed. Relationship between sea-air DMS flux and atmospheric DMS abundance was analyzed.As a result of analysis, seawater DMS in spring was higher than in December by a factor of 1.5〜2 in this area. Chlorophyll-a concentration derived from SeaWiES was also higher in April than in December. These results were due to an increase of marine production in spring. In addition, high MSA and non sea-salt sulfate concentrations in aerosol were observed when air parcel was transported from the elevated chlorophyll-a area within 1〜2 days. According to column model approach, these elevated concentrations in aerosol were mainly due to the, high emission of DMS in the elevated chlorophyll-a area and rapid oxidation of DMS under the high ozone condition. Although Kosa events were observed in these observations, we did not succeed getting enough data to show any sign of impact of Kosa on marine production.