Investigating the diurnal variability of trace gases in the TROpical West PACific measured by solar absorption spectrometry in the infrared (TROPAC)

西太平洋的海洋全年温度为30°C，是世界上最温暖的海洋。在热带西太平洋，边界层气温是全球最高的，上空臭氧最低。由于步行者环流从东部向东输送的对流层中低层平流，热带西太平洋上空长期处于清洁、温暖和潮湿的环境中，因此，热带地区氧气和臭氧前体物NOx的损失持续时间较长，导致臭氧浓度非常低。这增加了寿命短的生物和人为化学物种的寿命。此外，高海面温度有利于热带西太平洋的强对流活动，这可能导致对流层上层对流流出区的低臭氧混合比。西太平洋暖池也是平流层空气的主要来源。因此，短寿命物种寿命增加的区域与平流层空气的源区是重合的。因此，该地区对流层大气的组成在很大程度上决定了全球平流层的组成，臭氧是气候评估的重要示踪气体，因为温度变化、动力学变化和臭氧之间存在反馈过程。由于西太平洋暖池是平流层空气的主要来源区域，了解臭氧和其他寿命较短的痕量气体对于了解痕量气体向平流层的输送也很重要。我们的项目的目的是使用高分辨率的太阳吸收FTIR光谱测量臭氧和其他痕量气体的日变化。测量产生的总柱密度高达20种痕量气体。对于一些痕量气体，如O3，光谱线形状的分析允许检索高达约4个大气高度层的浓度分布。这些观测将得到臭氧气球探测仪、紫外线辐射连续测量和使用化学迁移模型的建模活动的补充。观察计划于2022年8月至10月进行，分析和解释计划于2022年11月至2023年1月进行。

The ocean in the West Pacific with temperatures of 30°C year-round is the warmest ocean worldwide. In the tropical West Pacific the boundary layer air temperature is highest globally and overhead ozone lowest. Due to the general low and mid-tropospheric advection from the east by the Walker circulation across the Pacific, air above the tropical West Pacific has been in a clean, warm and humid environment for a long time.Thus, the loss of odd oxygen and ozone precursors like NOx proceeded longer than elsewhere in the tropics, leading to very low ozone concentrations. This increases the lifetimes of short-lived biogenic and anthropogenic chemical species. Furthermore, high sea surface temperatures favor strong convective activity in the tropical West Pacific, which can lead to low ozone mixing ratios in the convective outflow regions in the upper troposphere. The West Pacific warm pool is also a major source region for stratospheric air. Hence, the region where the lifetimes of short lives species is increased and the source region of stratospheric air are coincident. Thus, the composition of the tropospheric atmosphere in this region determines the global stratospheric composition to a large extent.Ozone is an important trace gas for the climate assessment because of feedback processes among changing temperature, dynamics and ozone. Since the West Pacific warm pool is the major source region for stratospheric air, the knowledge of ozone and other shorter lived trace gases is also important to understand the transport of trace gases into the stratosphere. The aim of our project is to measure the diurnal variability of ozone and other trace gases using the high resolution solar absorption FTIR-spectrometry. The measurements yield the total columns densities of up to 20 trace gases. For a few trace gases, like O3, the analysis of the spectral line shape allows to retrieve the concentration profiles in up to about 4 atmospheric height layers. The observations will be complemented by ozone balloon sondes, continuous measurements of the UV-radiation, and modelling activities using a chemistry transport model. The observations are planned for August to October 2022, the analysis and interpretation from November 2022 until January 2023.