Solar Influences on Tropical Deep Convection and the Madden-Julian Oscillation (MJO): Observational Analyses and Tests of a Proposed Mechanism

该项目的目的是应用现有观测资料来评估短期太阳紫外线变率（主要发生在太阳自转约27天的时间尺度上）是否能在数周至数月的时间尺度上影响热带气候变率。它将具体探讨以前报告的关于热带太平洋部门这种影响的证据是否确实有力。统计分析将采用在太阳活动极大期（27天的变化特别大）下总共20年的太阳紫外线辐射测量数据。将分析对流层附近的温度和风等同步气象场，以确定短期太阳紫外线强迫是否能显著扰乱热带对流层上层的分层，从而改变深层对流的环境条件。将研究对天气和大尺度环流的相关影响。PI还将探索这种对27天太阳活动的响应是否取决于季节或El-Niño/南方涛动的阶段以及平流层准两年一次的振荡。任何检测到的反应的统计显著性将使用标准方法进行评估。确认太阳对热带对流和短期气候变率有显著的短期影响将(a)为检验包括太阳强迫在内的气候模式提供新的观测资料；(b)改善范围更广的天气预报；(c)提高我们对短期气候变率的理解。该项目将资助一名研究生和一名本科生。

The objective of this project is to apply available observations to evaluate whether short-term solar ultraviolet variability (occurring mainly on the ~ 27-day solar rotation time scale) can influence tropical climate variability on time scales from weeks to months. It will specifically explore whether previously reported evidence for such an influence in the tropical Pacific sector is indeed robust. Statistical analyses will employ a total of 20 years of solar ultraviolet radiation measurements under solar maximum conditions when 27-day variations are especially large. Coincident meteorological fields such as temperature and wind near the troposphere will be analyzed to determine whether short-term solar ultraviolet forcing can significantly perturb the stratification of the tropical upper troposphere and thereby modify the environment condition for deep convections. Associated effects on synoptic and large-scale circulations will be investigated. The PI will also explore whether such responses to the 27-day solar depend on season or on the phases of the El-Niño/Southern Oscillation as well as the stratospheric quasi-biennial oscillation. The statistical significance of any detected responses will be assessed using standard methods. Confirmation of a significant short-term solar impact on tropical convection and short-time climate variability would (a) provide a new observation for testing climate models that include solar forcing; (b) lead to improvements in extended-range weather forecasting; and (c) improve our understanding of short-time climate variability. The project will support one graduate student and one undergraduate student.