TCOM-COF2: TOMCAT CTM and Occultation measurement-based COF2 profile data set

TCOM-COF2: TOMCAT CTM and Occultation measurement-based Stratospheric TCOM-COF2 profile data set Sandip S. Dhomse School of Earth and Enviro, University of Leeds, Leeds, UK National Centre for Earth Observations, University of Leeds, Leeds, UK email: [e-mail] The TOMCAT simulation was conducted at a T64L32 resolution, consistent with previous work by Dhomse and Chipperfield (2023), covering the period from 2000 to 2024. These simulations utilized ERA-5 reanalysis data. COF2 Profile Processing and Bias Correction Collocated COF2 profiles are organized into five distinct latitude bins: NH polar: 90∘N - 50∘N NH mid-lat: 20∘N - 70∘N Tropics: 40∘S - 40∘N SH mid-lat: 70∘S - 20∘S SH polar: 90∘S - 50∘S Initially, TOMCAT tracers are interpolated on the ACE FTS height (1km to 50km) Separate XGBoost regression models are trained to predict ACE FTS measurements for a given altitude /latitude bin if more than 2000 measurements are available. XGBoost model is then used to estimate COF2 volume mixing ratios for all the TOMCAT grids. Height resolved data are then interpolated on 22-pressure levels. For overlapping latitude bins, we use averages and then calculate daily zonal mean values. For more details see attached presentation. Dataset also includes two files containing daily mean zonal mean COF2 profiles on height (1-50 km) and pressure (300-1 hPa) – 22 levels (9132 days/64 latitudes). Files also include uncertainties estimated using quantile regression and uncertainty = NaN means data is from TOMCAT CTM (scientifically useful range 10 to 35km). zmcof2_tcom_hlev_2000-2024_V2.0.nc – height level data (1 to 50 km) zmcof2_tcom_plev_2000-2024_V2.0.nc – pressure level data (300 to 1 hPa) Daily 3D profiles on height and pressure levels would be made available on request. Xarrays “resample” can be used to get monthly means. (Attached pdf file gives more details. This data set improves from our previous methodology (Dhomse and Chipperfield, 2023, ESSD) and manuscript describing to those updates is submitted to ESSD as Dhomse and Chipperfield, 2026. Reference Publications This methodology, incorporating only ACE-FTS data and various minor algorithmic developments, is based on the following publication: Dhomse, S. S. and Chipperfield, M. P.: Using machine learning to construct TOMCAT model and occultation measurement-based stratospheric methane (TCOM-CH4) and nitrous oxide (TCOM-N2O) profile data sets, Earth Syst. Sci. Data, 15, 5105–5120, https://doi.org/10.5194/essd-15-5105-2023, 2023 Dhomse, S. S. and Chipperfield, M. P.: TCOM-CFC11 and TCOM-CFC12: A Gap-Free, Observationally Constrained Global Dataset of Stratospheric CFC11 and CFC12 Profiles (V2)., submitted to Earth Syst. Sci. Data, 2026TCOM-COF2：基于TOMCAT化学传输模式（CTM）与掩星观测的平流层COF2廓线数据集 Sandip S. Dhomse 英国利兹大学地球与环境学院 英国利兹大学国家地球观测中心 邮箱：[e-mail] 本研究采用T64L32分辨率开展TOMCAT模拟，与Dhomse及Chipperfield（2023）的既往研究保持一致，模拟时段为2000年至2024年，所用驱动数据为ERA-5再分析资料。 ## COF2廓线处理与偏差校正 匹配得到的COF2廓线被划分为5个独立的纬度区间： - 北半球极地：90°N ~ 50°N - 北半球中纬度：20°N ~ 70°N - 热带区域：40°S ~ 40°N - 南半球中纬度：70°S ~ 20°S - 南半球极地：90°S ~ 50°S 首先，将TOMCAT示踪物插值至ACE傅里叶变换光谱仪（ACE FTS）的高度坐标系（1km至50km）。若某一高度/纬度区间内的观测样本量超过2000条，则针对该区间训练独立的极限梯度提升（XGBoost）回归模型，以预测ACE FTS观测值。随后利用该XGBoost模型估算所有TOMCAT网格点上的COF2体积混合比。将高度解析的数据进一步插值至22个气压层。对于存在重叠的纬度区间，先取均值，再计算逐日纬向平均结果。更多细节详见附件汇报材料。 本数据集包含两个文件，分别存储高度坐标系（1~50km）与气压坐标系（300~1 hPa，共22层）下的逐日纬向平均COF2廓线，数据集总规模为9132天/64个纬度。文件中同时包含通过分位数回归估算的不确定性值：若不确定性为NaN，则表示该数据来自TOMCAT CTM，其科学应用的有效高度范围为10~35km。 - "zmcof2_tcom_hlev_2000-2024_V2.0.nc"：高度层数据（1~50km） - "zmcof2_tcom_plev_2000-2024_V2.0.nc"：气压层数据（300~1 hPa） 高度与气压坐标系下的逐日三维廓线可根据需求提供。可借助Xarrays库的"resample"方法计算月均数据。 附件PDF文件提供更多细节。本数据集相较于Dhomse与Chipperfield（2023，ESSD）的既往方法进行了优化，相关更新说明手稿已提交至《地球系统科学数据》（ESSD），作者为Dhomse和Chipperfield，2026年。 ## 参考文献 本数据集所用方法仅采用ACE-FTS观测数据并进行了若干算法改进，相关方法源自以下文献： 1. Dhomse S S, Chipperfield M P. 利用机器学习构建基于TOMCAT模式与掩星观测的平流层甲烷（TCOM-CH4）与一氧化二氮（TCOM-N2O）廓线数据集[J]. Earth Syst. Sci. Data, 2023, 15: 5105-5120. https://doi.org/10.5194/essd-15-5105-2023 2. Dhomse S S, Chipperfield M P. TCOM-CFC11与TCOM-CFC12：一套无间隙、受观测约束的平流层CFC11和CFC12廓线全球数据集（V2.0）[J]. 已提交至Earth Syst. Sci. Data, 2026