The Distance Effect Annual Cycle in Earth's Climate

该项目旨在研究地球轨道几何形状对气候的两个方面的影响。热带太平洋的西太平洋暖池保留了地球上最大和最温暖的海洋表面水体，而赤道东太平洋的特点是寒冷、营养丰富的深水强烈上涌，被称为太平洋冷舌。了解太平洋暖池和冷舌的演变具有重要意义，因为它们控制着环太平洋气候，并通过厄尔尼诺-南方涛动（ENSO）遥相关影响全球。先前的研究表明，太平洋冷舌有两个年度周期，由地球轨道的不同特征驱动。其中一个周期是由热带辐合带（ITCZ）的季节性迁移驱动的，并最终与由于地轴倾斜（即“倾斜”效应）引起的太阳日照的季节性和纬度分布有关。虽然这种“倾斜”效应已被广泛研究，但另一种“距离”效应则较少。有人认为，“距离”效应是由沃克环流强度的季节变化引起的，并且是由地球轨道的离心率引起的日地距离的年演变所强迫的。本研究项目将探讨距离效应对地球气候的影响，特别是：1)大气环流的距离效应季节性；2)区域气候的季节性，选择距离效应相对于倾斜度有不成比例大影响的区域，包括南太平洋的西风带；3)热带太平洋平均状态和厄尔尼诺-南方涛动（ENSO）。潜在的更广泛影响（bi）包括对研究生和本科生的支持，公众宣传，以及对具有重要社会影响的气候的更全面的了解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to investigate the impact of two aspects of Earth’s orbital geometry on its climate. The Western Pacific Warm Pool of the tropical Pacific Ocean retains the largest and warmest sea surface water body on Earth while the eastern equatorial Pacific is characterized by strong upwelling of cold, nutrient-rich deep waters, termed the Pacific cold tongue. Understanding the evolution of the Pacific warm pool and cold tongue are important because they control the circum-Pacific climate and impact the globe via El Nino-Southern Oscillation (ENSO) teleconnections.Previous research indicates that the Pacific cold tongue has two annual cycles driven by distinct features of the Earth’s orbit. One of these cycles is driven by the seasonal migration of the InterTropical Convergence Zone (ITCZ) and is ultimately linked to the seasonal and latitudinal distribution of solar insolation due to the tilt of the Earth’s axis – the “tilt” effect. While this “tilt” effect annual cycle has been extensively studied, the other “distance” effect is less so. It is argued that the “distance” effect arises from seasonal variations in the strength of the Walker circulation and is forced by the annual evolution of the Earth-Sun distance due to the eccentricity of Earth’s orbit.This research project will investigate how the distance effect imprints its climate influence on Earth, specifically on the: 1) distance-effect seasonality of the atmospheric general circulation; 2) seasonality of regional climates, choosing regions where the distance effect has a disproportionately large impact relative to tilt, including the westerlies over the South Pacific; and 3) tropical Pacific mean state and El Nino-Southern Oscillation (ENSO).The potential Broader Impacts (B.I.) include support for graduate and undergraduate students, public outreach, and a more comprehensive understanding of climate with important societal impacts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.