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（WWBs）与重大厄尔尼诺事件的发生有关。它们发生得更频繁，更活跃，在重大厄尔尼诺事件之前和期间比在非厄尔尼诺条件下向东延伸得更远。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地受到大尺度海面温度（SST）的调制。模式研究表明，与纯粹随机的WWB情况相比，这种调制会影响厄尔尼诺的特征。第一个较实用的组成部分是将经验性的WWB参数化纳入最先进的厄尔尼诺-南方涛动预测模式，以提高厄尔尼诺-南方涛动预测技能，并评估参数化WWB对可预测性的影响。一个基于观测的经验半随机WWB模式将应用于NCAR CCSM3.0（National Center for Atmospheric Research Community Climate System Model 3.0）海气耦合模式中，并作为ENSO预报模式。将研究WWB模式和耦合的ENSO模式之间的相互影响，沿着WWB对ENSO模拟、对ENSO的可预报性和对模式预测范围的影响。第二部分是试图了解WWB的基本机制及其对大尺度SST场的依赖动力学。一个能够产生WWB的云解析大气模型将使用非绝热加速和重新缩放（DARE）方法在近全球配置中运行。DARE模式将以观测到的风和向外长波辐射的分析以及几个简单的模式作为补充。这一战略的目的是了解SST如何控制WWBs，并揭示产生WWBs的对流活动的启动和终止机制。这一项目的更广泛影响是有助于提高预测ENSO的技能，从而产生社会和经济效益。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.