A Study of the Dynamics of the Marine Stratocumulus Boundary Layer Using Fast Dimethyl Sulfide (DMS) Measurements

这笔拨款支持在2001年7月的DYCOMS-II项目（海洋层状云动力学和化学）中部署一种快速响应的机载仪器，用于测量二甲基硫化物（DMS）的浓度。DMS是一种大气微量气体，是海洋边界层与自由大气混合的有效指标。它的主要来源是海洋表面，它在大气中的寿命约为一天。因此，它在边界层中的浓度相对较高，而在自由大气中的浓度较低。边界层顶部浓度的波动表明了边界层与上方空气之间的混合强度和传质速率。该仪器是一种快速响应电离质谱仪，能够产生时间分辨率为50毫秒的数据。与其他测量温度、垂直空气速度、湿度、云滴浓度和大小、气溶胶大小和组成的飞机仪器相结合，它将提供云顶夹带过程的信息。这些数据将用于海洋层积云混合大涡模拟的测试和评价。

This grant supports the deployment of a fast-response, airborne instrument for measuring the concentration of dimethyl sulfide (DMS) during the DYCOMS-II project in July 2001 (Dynamics and Chemistry of Marine Stratocumulus). DMS is an atmospheric trace gas which is an effective indicator of mixing between the marine boundary layer and the free atmosphere. Its main source is the ocean surface and its lifetime in the atmosphere is about one day. It therefore has relatively high concentration in the boundary layer and low concentration in the free atmosphere. Fluctuations in the concentration at the top of the boundary are an indication of the strength of mixing and the rate of mass transfer between the boundary layer and the air above. The instrument is a fast-response ionization mass spectrometer capable of yielding data with a time resolution of 50 ms. In combination with other aircraft instruments that measure temperature, vertical air velocity, humidity, cloud droplet concentration and sizes, and aerosol sizes and composition, it will provide information on entrainment processes at cloud top. The data will be used in the testing and evaluation of large eddy simulations of mixing in marine stratocumulus clouds.