Properties of identified ship tracks

The ship track database of is used, which used "day microphysics" images comprised of a composite of visible, near and thermal infrared channels were used to manually locate likely positions of ship tracks. Identification was assisted by examining the CDNC, calculated from the MYD06 level 2 cloud retrieval products from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite. The CDNC is calculated based on the adiabatic assumption, using the cloud optical depth and cloud effective radius from the MODIS MYD06 level 2 product. Ship locations were sourced from their automatic identification system (AIS) data, allowing an observed ship track to be linked to the generating ship. Local meteorology was gathered from the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data, and ships mass emission rates were calculated using their specific fuel consumption and estimated drag. Data labels: trackno: Ship track identifier (-) sox: SO emission rate (kg s^-1) cbh: Cloud base height (m) blh: Boundary layer height (m) cth: Cloud top height (m) spd_res: Relative velocity between ship velocity and wind velocity (m s^-1) nd_cln: Background cloud droplet number concentration (cm^-3) nd_pol: Ship track cloud droplet number concentration (cm^-3) cf_liq: Liquid cloud fraction (-) lwp: Liquid water path (g m^-2) t1000: Temperature at 1000 hPa (K) LTS: Low tropospheric stability (K) ctt: Cloud top temperature (K) ctrc: Cloud top radiative cooling (W m^-2) is_coupled: Flag for cloud coupling according to cloud base height indicator (cbh<1000 m)本数据集采用的船舶尾迹数据库，使用由可见光、近红外与热红外波段合成的"day microphysics"图像，手动定位船舶尾迹的疑似位置。识别过程借助对云凝结核数浓度（Cloud Condensation Number Concentration，CDNC）的分析辅助完成，该浓度基于Aqua卫星上搭载的中分辨率成像光谱仪（Moderate Resolution Imaging Spectroradiometer，MODIS）的MYD06二级云反演产品计算得到。CDNC的计算依托绝热假设，使用MODIS MYD06二级产品中的云光学厚度与云有效半径参数。 船舶位置信息源自其自动识别系统（Automatic Identification System，AIS）数据，可将观测到的船舶尾迹与对应船舶进行关联。局地气象数据取自欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts）的ERA5再分析资料，船舶的污染物排放速率则通过其单位燃油消耗量与估算阻力计算得到。 数据标签说明如下： trackno：船舶尾迹标识符（无量纲） sox：硫氧化物（Sulfur Oxides，SOₓ）排放率（kg·s⁻¹） cbh：云底高度（m） blh：边界层高度（m） cth：云顶高度（m） spd_res：船舶航速与风速的相对速度（m·s⁻¹） nd_cln：背景云凝结核数浓度（cm⁻³） nd_pol：船舶尾迹云凝结核数浓度（cm⁻³） cf_liq：液态云占比（无量纲） lwp：液态水路径（g·m⁻²） t1000：1000百帕高度处的气温（K） LTS：低层对流层稳定度（Low Tropospheric Stability，LTS）（K） ctt：云顶温度（K） ctrc：云顶辐射冷却率（W·m⁻²） is_coupled：基于云底高度指标（cbh<1000 m）的云耦合状态标记