WCRP and WWRP THORPEX YOTC (Year of Tropical Convection) Project, Single Parameter 6-Hourly Surface Analysis and Surface Forecast Time Series, Transformed to a Regular 1600 by 800 (N400) Gaussian Grid

The realistic representation of tropical convection in our global atmospheric models is a long-standing grand challenge for numerical weather forecasts and global climate predictions. Our lack of fundamental knowledge and practical capabilities in this area leaves us disadvantaged in modeling and predicting prominent phenomena of the tropical atmosphere such as the ITCZ, ENSO, TBO, monsoons and their active or break periods, the MJO, subtropical stratus decks, near-surface ocean properties, easterly waves, tropical cyclones, bulk budgets of cloud microphysical quantities, and even the diurnal cycle. Furthermore, tropical weather and climate disturbances strongly influence stratospheric-tropospheric exchange as well as the extratropics, with the later mediated via poleward migration of synoptic systems or through initiating Rossby wave trains that can involve a range of processes and time scales.To address the challenge of tropical convection, WCRP and WWRP/THORPEX propose a Year of coordinated observing, modeling and forecasting of organized tropical convection and its influences on predictability as a contribution to the United Nations Year of Planet Earth to complement the International Polar Year (IPY). This effort is intended to exploit the vast amounts of existing and emerging observations, the expanding computational resources and the development of new, high-resolution modeling frameworks, with the objective of advancing the characterization, diagnosis, modeling, parameterization and prediction of multiscale convective and dynamic interactions, including the two-way interaction between tropical and extra-tropical weather or climate. This activity and its ultimate success will be based on the coordination of a wide range of ongoing and planned international programmatic activities (e.g., GEWEX/CEOP/GCSS, AMY, EOS, GOOS), strong collaboration among the operational prediction, research laboratory and academic communities, and the construction of a comprehensive data base consisting of satellite data, in-situ data sets and global, high-resolution forecast and simulation model outputs relevant to tropical convection. The proposed timing, focus year approach and integrated framework of this effort is intended to leverage the most benefit from recent investments in Earth Science infrastructure as well as entrain a new generation of young scientists into tackling the outstanding problems in the field of weather and climate prediction.It is recommended that potential users of YOTC peruse the Related RDA Datasets ds629.1-ds629.6 (please see below) which represent transformed versions of the raw ECMWF YOTC archive (ds629.0) by the Data Support Section. The transformed versions are archived on an N400 1600 by 800 regular Gaussian grid, starting from high resolution reduced Gaussian grids and spectral coefficients. In addition, horizontal winds have been added and computed from spectral vorticity and divergence.

在全球大气模式中对热带对流进行真实刻画，是数值天气预报和全球气候预测领域长期面临的重大挑战。我们在该领域缺乏基础认知与实践能力，导致在模拟和预测热带大气关键现象时处于不利地位，这些现象包括热带辐合带（Intertropical Convergence Zone，ITCZ）、厄尔尼诺-南方涛动（El Niño-Southern Oscillation，ENSO）、热带准两年振荡（Tropical Biennial Oscillation，TBO）、季风及其活跃或中断期、Madden-Julian振荡（Madden-Julian Oscillation，MJO）、副热带层积云、近海面海洋特性、东风波、热带气旋、云微物理量的总体收支，甚至日变化周期。此外，热带天气与气候扰动对平流层-对流层交换及温带地区均具有强烈影响，后者通过天气系统向极迁移或激发Rossby波列实现，而Rossby波列涉及多种过程和时间尺度。

为应对热带对流研究的这一挑战，世界气候研究计划（World Climate Research Programme，WCRP）与世界天气研究计划/全球观测系统研究与可预报性试验（World Weather Research Programme/The Observing System Research and Predictability Experiment，WWRP/THORPEX）联合提出了“有组织热带对流及其对可预报性影响的协调观测、模拟与预报年”（Year of Tropical Convection，YOTC），作为对联合国地球年（United Nations Year of Planet Earth）的贡献，并补充国际极地年（International Polar Year，IPY）的研究。该计划旨在利用海量现有及新兴观测数据、不断拓展的计算资源以及新型高分辨率模式框架的发展成果，目标是推动多尺度对流与动力相互作用（包括热带与温带天气或气候之间的双向相互作用）的刻画、诊断、模拟、参数化及预测研究。

该活动及其最终成功将依赖于协调各类正在开展及规划中的国际计划活动（如全球能量与水循环试验/协调增强观测期/全球云系统研究与气候模拟计划（Global Energy and Water Cycle Experiment/Coordinated Enhanced Observing Period/Global Cloud System Study，GEWEX/CEOP/GCSS）、大气观测任务（Atmospheric Measurement Campaign，AMY）、地球观测系统（Earth Observing System，EOS）、全球海洋观测系统（Global Ocean Observing System，GOOS））、业务预报机构、研究实验室与学术界之间的紧密协作，以及构建包含卫星数据、现场数据集和与热带对流相关的全球高分辨率预报及模拟模式输出的综合数据库。该计划所提出的时间安排、聚焦年模式及综合框架，旨在最大限度利用近期地球科学基础设施的投资成果，并吸引新一代青年科学家投身于天气与气候预测领域尚未解决的问题研究。

建议YOTC的潜在用户查阅相关的研究数据档案数据集（Research Data Archive Datasets，RDA Datasets）ds629.1至ds629.6（详见下文），这些数据集是数据支持部门对欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts，ECMWF）YOTC原始存档（ds629.0）进行转换后的版本。转换后的数据集基于高分辨率缩并高斯网格和谱系数生成，存档于N400规则高斯网格（1600×800）上。此外，数据集还新增了水平风场，该风场由谱涡度和散度计算得到。