Collaborative Research: P2C2--Expansion/Contraction of the Intertropical Convergence Zone; An Emerging Mechanism of Tropical Precipitation Changes for Reinterpreting Paleoclimate

热带降水的空间分布是由热带辐合带（ITCZ）的平均位置和季节走向决定的。ITCZ的纬向移动通常被用作解释过去水文气候变化和确定（过去和未来）气候强迫响应机制的首选理论。然而，这个项目是基于这样一个前提，即ITCZ的同时收缩和强化（CI）是响应古气候和人为强迫的热带降水变化模式（4倍），而不是更常用的ITCZ移动。该项目的总体目标是将古气候代理记录中CI模态过去变化的重建与CI模态的动力框架结合起来，以约束未来热带降水的变化和变率。这一具体目标是：i)探索CI模式的动力学，以确定导致过去和未来气候模拟中所见变化方向的机制，并评估这些过程中的不确定性；ii)利用CI模式的新知识重新解释古气候记录，以约束ITCZ相对于CI变化的过去行为。该项目将有助于加深对ITCZ的了解，并有可能提高气候模式预测局部降水规模和空间结构的大尺度未来变化（和变率）的能力。该项目还将支持两名早期职业科学家，并利用华盛顿大学和加州大学伯克利分校现有的科学公共推广项目。

The spatial distribution of tropical precipitation is determined by the average location and seasonal march of the intertropical convergence zone (ITCZ). The latitudinal shift of the ITCZ is typically employed as the go-to theory for interpreting past hydroclimate changes and defining mechanisms of the response to climate forcing (past and future). This project, however, is based on the premise that the simultaneous contraction and intensification (CI) of the ITCZ is a far more powerful mode of tropical precipitation changes (by a factor of 4) in response to both paleoclimate and anthropogenic forcing than the more commonly employed ITCZ shift.The overarching goal of the project is to couple reconstructions of past changes in the CI mode from paleoclimate proxy records with a dynamical framework of the CI mode to constrain future tropical precipitation changes and variability. This specific aims are to: i) explore the dynamics of the CI mode to identify the mechanisms that lead to the direction of changes seen in simulations of past and future climate as well as evaluate the uncertainties in these processes and ii) use the emerging knowledge of the CI mode to reinterpret the paleoclimate record to constrain the past behavior of ITCZ shifts versus CI. The project would help develop a deeper understanding of the ITCZ and potentially improve the ability of climate models to forecast broad-scale future changes (and variability) in the magnitude and spatial structure topical precipitation. The project would also support two early career scientists and leverage existing public outreach programs in science at the University of Washington and the University of California-Berkeley.