Collaborative Research: Westerly Wind Burst Modulation by the Sea-Surface Temperature (SST): from Understanding to El Nino-Southern Oscillation (ENSO) Prediction

西风爆发(WWB)与重大厄尔尼诺事件的发生有关。在重大厄尔尼诺事件之前和期间，它们比非厄尔尼诺条件下更频繁和更强烈地发生，并向东延伸得更远。虽然这些风事件最初被认为是完全随机的，但最近的分析表明，它们的发生和特征至少部分受到大尺度海表面温度(SST)的调制。模型研究表明，与纯随机WWB的情况相比，这种调制影响了厄尔尼诺现象的特征。NCAR CCSM3.0(国家大气研究中心社区气候系统模式3.0)海气耦合模式将采用一个基于观测激励的经验半随机WWB模式，该模式将被用作ENSO预报模式。研究WWB模式和耦合ENSO模式之间的相互影响，以及WWB对ENSO模拟的影响、对ENSO预报能力的影响以及预报在模式中的传播。第二部分是对WWB的基本机制及其对大尺度海温场的依赖动力学的研究。一个能够产生WWB的云解析大气模式将使用非绝热加速和重新定标(DARE)方法在近全球配置中运行。DARE模型将补充对观测到的风和出射长波辐射的分析，以及几个简单的模型。两名研究生将接受培训：一名在哈佛，一名在迈阿密。

Westerly wind bursts (WWBs) are associated with the onset of major El Nino events. They occur more frequently and energetically and extend farther eastward prior to and during significant El Nino events than in non-El Nino conditions. While these wind events were initially thought to be completely stochastic, more recent analyses indicate that their occurrence and characteristics are at least partially modulated by the large-scale sea-surface temperature (SST). Model studies show that this modulation affects the characteristics of El Ninos as compared to the case of purely stochastic WWBs.This project is divided into two parts. The first, more applied, component is the implementation of an empirical WWB parameterization into a state-of-the-art El Nino-Southern Oscillation (ENSO) prediction model, in an effort to improve the skill of ENSO prediction and to assess the impact of parameterized WWBs on predictability. A previously developed empirical semi-stochastic observationally-motivated WWB model will be applied in the NCAR CCSM3.0 (National Center for Atmospheric Research Community Climate System Model 3.0) coupled ocean-atmosphere model, and this model will be used as an ENSO prediction model. The mutual effects of the WWB model and the coupled ENSO model on each other will be studied, along with the effects of the WWBs on the ENSO simulation, on the predictability of ENSO, and on the spread of predictions in the model. The second part is an effort to understand the basic mechanisms of WWBs and the dynamics of their dependence on the large-scale SST field. A cloud-resolving atmospheric model capable of producing WWBs will be run in a near-global configuration using the diabatic acceleration and rescaling (DARE) approach. The DARE model will be supplemented with analyses of observed wind and outgoing longwave radiation and with several simple models. It is intended that this strategy will result in an understanding of how the SST controls WWBs and will expose the mechanisms for the initiation and termination of the convective activity that creates WWBs.The broader impacts of this project are in contributing to improved skill in predicting ENSO, with the resulting social and economic benefits. Two graduate students will be trained: one at Harvard and one at Miami.