Finding the right Mathematical Model for Atmospheric Convection

地球上一些最极端的天气与深对流风暴有关，这些风暴是由水蒸气变成液态云水或冰时释放的热量驱动的。这些风暴开始时是小的湍流漩涡，然后发展成猛烈的雷暴。风暴可以组织成更大的结构，如飑线和热带气旋。然而，这种规模越来越大的组织仍然部分地受到最小湍流尺度上发生的过程的控制。在用于预测天气的模型中，最小尺度不能准确地表示，这损害了天气预报的准确性。本专题旨在评估最小尺度表示的新方法。学生将评估两种平均方法的适用性，以推导代表与对流相关的次网格尺度变化的方程。条件平均假设每个网格框有两个动量、温度和密度值，以代表大气中对流活跃（多云）和稳定（晴朗天空）区域的条件。成交量平均包括预测均值、标准差和变量之间的相关性。该项目将首先评估哪种平均技术最能代表低分辨率下的高分辨率数据。然而，数据的表示仅仅是开始。最大的挑战在于使用体积或条件平均方程建立预测模型，以及预测小尺度湍流运动和深对流之间的过渡。学生将使用平均技术开发现有的模型，并提出和测试预测大气对流稳定和对流活跃区域之间过渡的新想法。结果将与高分辨率的对流模式进行比较。参数化硬灰区对流“在阅读，这是NERC/气象局计划”理解和代表跨尺度大气对流“的一部分。因此，学生将成为全国网络的一部分。这是一个为直接用于天气和气候预报的模型开发做出贡献的机会。

Some of the most extreme weather on the planet is associated with deep convective storms driven by the heat released when water vapour turns into liquid cloud water or ice. These storms start out as small turbulent eddies which grow into violent thunderstorms. Storms can organise into much larger structures such as squall lines and tropical cyclones. This ever-larger scale organisation nevertheless remains, in part, controlled by processes occurring at the smallest turbulent scales. The smallest scales are not represented accurately in models used to predict the weather, which compromises the accuracy of weather forecasts. This project is aimed at evaluating new approaches to the representation of the smallest scales.The student will assess the suitability of two types of averaging for deriving equations that represent the sub-grid scale variability associated with convection. Conditional averaging assumes two values of momentum, temperature and density per grid box in order to represent the conditions in both the convectively active (cloudy) and stable (clear sky) regions of the atmosphere. Volume averaging involves predicting means, standard deviations and correlations between variables. The project will start by assessing which averaging technique can best represent high resolution data at low resolution. However the representation of the data is just the start. The big challenge lies in creating prediction models using volume or conditionally averaged equations and in predicting the transition between small scale, turbulent motion and deep convection. The student will develop existing models using both averaging techniques and will propose and test new ideas for predicting the transition between convectively stable and convectively active regions of the atmosphere. The results will be compared with high resolution models of convection.This project is part of ``Project Circle-A. Parametrizing Convection in the Hard Grey Zone'' at Reading which is part of the NERC/Met Office programme ``Understanding and Representing Atmospheric Convection across Scales''. The student will therefore be part of a national network. This is an opportunity to contribute to model development that will directly feed in to weather and climate forecasting.