Mechanisms for the Northward Displacement of the Pacific Intertropical Convergence Zone (ITCZ)

该项目将调查热带间辐合带(ITCZ)赤道外位置的原因。东北和东南信风的汇合产生了水汽通量辐合，为热带深层对流提供了条件。对流在卫星图像中显示为一条明亮的云带，有助于识别ITCZ。尽管太阳强迫在年平均上几乎是对称的，但中/东太平洋的ITCZ在一年中的大部分时间里都保持在赤道以北。最近的研究揭示了赤道和沿海地区的海洋-大气相互作用以及大陆(例如美洲)的地理不对称性在形成国际热带气旋管制区北半球位置方面的作用，但许多关键问题仍未得到解答。不足为奇的是，在当前的气候模型中，ITCZ仍然是一个模拟得很差的特征。谢尚平博士和李添博士将利用一对耦合的气候模式，通过模拟分析确定控制ITCZ位置的关键气候相互作用。PIS将把美洲的地理不对称性分解成几个元素，并在ITCZ的子午线位置范围内调查它们的“对称破坏”潜力。他们还将调查东太平洋ITCZ和北美季风的相互作用。这项研究将促进对海洋、陆地和大气如何相互作用以塑造东太平洋气候的理解。通过这样做，它将为NSF的东太平洋气候调查(EPIC)现场计划提供大规模的解释框架，并为美国CLIVAR计划的泛美/太平洋研究目标做出贡献。

The project will investigate the causes for the off-equatorial location of the Inter-Tropical Convergence Zone (ITCZ). The confluence of northeast and southeast trade winds generates the moisture flux convergence that feeds deep tropical convection. The convection shows up as a bright cloud band in satellite pictures, and helps identify the ITCZ. Although solar forcing is nearly symmetric in the annual-mean, the ITCZ in the central/eastern Pacific remains northward of the equator throughout much of the year. Recent studies have revealed the role of ocean-atmosphere interactions in equatorial and coastal zones, and of geographical asymmetries of continents (e.g., the Americas) in producing the Northern hemisphere location of the ITCZ, but many key questions remain unanswered. Not surprisingly, the ITCZ remains a poorly simulated feature in current climate models. Drs. Shang-Ping Xie and Tim Li will identify the key climate interactions that control ITCZ location from modeling analysis, using a pair of coupled climate models. The PIs will decompose the geographical asymmetries of the Americas into several elements and investigate their "symmetry-breaking" potential in context of ITCZ's meridional position. They will also investigate the interaction of the eastern Pacific ITCZ and the North American monsoon. This research will advance the understanding of how ocean, land, and the atmosphere interact to shape the eastern Pacific climate. In so doing, it will provide the large-scale interpretive framework for NSF's Eastern Pacific Investigation of Climate (EPIC) field program, and also contribute to the Pan American/Pacific research goals of the U.S. CLIVAR program.