Testing of an Improved Cumulus Parameterization in the NMC Global Model

兰德尔博士开发了一种新的积云参数化方法，该方法已经在科罗拉多州立大学的一般环流模式下进行了研究。这种参数化的早期结果非常有希望。根据该合同，参数化将在使用国家气象中心（NMC）全球预报模型的操作环境中进行测试。在数值模式中适当地表示积云对改善天气预报是必不可少的。积云在释放潜热方面发挥重要作用，潜热驱动大气环流，在雷暴和热带气旋的发展和演变中也起着重要作用。新方案有许多特点，使其在实用和科学上都具有吸引力。与它的前身Arakawa-Schubert参数化不同，这个版本允许在模型的任何水平形成穿透性积云。它也允许形成浅积云对流下降气流。因此，新方案使数值模型更接近于在自然界中观察到的情况。在计算上，新方案在简单性和速度方面似乎更胜一筹。新方案的预报将与国家气象中心现有积云方案的预报进行比较。首席研究员希望证明他的参数化的鲁棒性和模型独立性。该项目由NSF-NMC数值天气预报联合项目支持。

Dr. Randall has developed a new cumulus cloud parameterization that has been run in a research mode with the general circulation model at Colorado State University. Early results with this parameterization are quite promising. Under this award, the parameterization will be tested in an operational environment using the National Meteorological Center's (NMC) global forecast model. Proper representation of cumulus clouds in numerical models is essential for improving weather prediction. Cumulus clouds are important in releasing latent heat which drives the atmospheric circulation as well as playing a major role in the development and evolution of thunderstorms and tropical cyclones. The new scheme has many features which make it attractive for both practical and scientific reasons. Unlike its predecessor, the Arakawa-Schubert parameterization, this version allows penetrative cumulus clouds to form at any level in the model. It also allows for the formation of shallow cumulus cloud convective downdrafts. The new scheme thus brings the numerical model closer to what is observed in nature. Computationally, the new scheme appears to be superior in terms of simplicity and speed. Forecasts with the new scheme will be compared with those made with NMC's current cumulus scheme. The principal investigator hopes to demonstrate the robustness and model independence of his parameterization. This project is being supported under the NSF-NMC Joint Program in Numerical Weather Prediction.