AGS-PRF: The Diurnal Cycle, Cloud-Radiative Feedbacks, and Large-scale Tropical Dynamics

AGS-PRF：昼夜循环、云辐射反馈和大尺度热带动力学

• 批准号: 1524844
• 负责人: James Ruppert
• 金额: $ 9.6万
• 依托单位: Ruppert James H
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524844&HistoricalAwards=false
• 关键词: AGS; PRF; Diurnal; Cycle; Cloud

This award supports a 2-year Postdoctoral Research Fellowship in which the PI will study the influence of the diurnal cycle on the Madden-Julian Oscillation (MJO). The MJO is a large region of convection and rainfall that forms over the Indian Ocean and propagates slowly eastward into the central equatorial Pacific. The MJO influences weather and climate worldwide, affecting the formation of hurricanes in the Gulf of Mexico, atmospheric rivers that produce floods and landslides on the US west coast, and the onset of El Nino events, among other impacts. Despite its importance and concerted efforts over several decades, the MJO has not yet been adequately explained, and weather and climate models have difficulty simulating and predicting it.Research under this award addresses two aspects of the diurnal cycle, the first of which is the influence of the diurnal cycle of sea surface temperature (SST) in moistening the overlying atmosphere. When the MJO is in its "suppressed" phase, in which fair weather prevails in the absence of organized convection and rainfall, SST has a relatively pronounced diurnal cycle. The diurnal cycle of SST is expected to result in greater surface evaporation and more vigorous vertical mixing of moisture throughout the lower atmosphere, with the overall moistening serving to promote the onset of the "active" phase of the MJO. A suite of computer simulations is used to determine the importance of the diurnal cycle of SSTs for moistening the atmosphere and promoting MJO onset.Further research considers the change in the diurnal cycle of cloudiness that occurs between the suppressed and active phases of the MJO. The smaller and less developed clouds of the suppressed phase occur preferentially in the afternoon, while the deep convective clouds of the active phase are most prominent at night. The PI hypothesizes that this shift in the time of maximum cloudiness has implications for the solar heating of the atmosphere that constitute a positive feedback, enhancing convection during the active phase and inhibiting it in the suppressed phase. Further computer simulations will be performed to test this hypothesis.Finally, the PI will perform a simulation of an MJO event observed during the DYNAMO field campaign (see AGS-1022899) using a global high-resolution nonhydrostatic model (the ICON model). The results of the simulation will be used to further test the hypothesized effects of the diurnal cycle on the MJO. As noted above, the work has societal broader impacts due to the worldwide weather and climate impacts of the MJO and the potential of this research to improve MJO forecasts. In addition, the work supports the PI at an early stage of his career, thereby promoting the future workforce in the research area. Also, the work is conducted at the Max Planck Institute of Meteorology (MPI-M) in Hamburg, Germany, under the supervision of Dr. Cathy Hohenegger. The host institution is among the world's top climate modeling centers, and scientific collaboration between a US PI and MPI-M scientists is expected to be beneficial to the US research community.This award was supported with funding from the Office of International Science & Engineering as well as the Climate and Large-scale Dynamics Program.

该奖项支持为期 2 年的博士后研究奖学金，其中 PI 将研究昼夜周期对马登-朱利安振荡 (MJO) 的影响。 MJO 是印度洋上空形成的一大片对流和降雨区域，缓慢向东传播到赤道中太平洋。 MJO 影响全世界的天气和气候，影响墨西哥湾飓风的形成、美国西海岸引发洪水和山体滑坡的大气河流以及厄尔尼诺事件的发生等。尽管它很重要并且经过了几十年的共同努力，但 MJO 尚未得到充分解释，天气和气候模型也很难对其进行模拟和预测。该奖项的研究涉及昼夜周期的两个方面，第一个是影响海洋表面温度（SST）的昼夜循环对上覆大气的湿润作用。 当MJO处于“抑制”阶段时，天气晴朗，但没有有组织的对流和降雨，海表温度具有相对明显的昼夜周期。 海表温度的昼夜循环预计将导致整个低层大气中更大的表面蒸发和更剧烈的水分垂直混合，整体湿润有助于促进 MJO“活跃”阶段的开始。 使用一套计算机模拟来确定海表温度的昼夜循环对于湿润大气和促进 MJO 爆发的重要性。进一步的研究考虑了 MJO 抑制阶段和活跃阶段之间发生的云量昼夜循环的变化。 抑制阶段较小且较不发达的云优先出现在下午，而活动阶段的深对流云在夜间最为突出。 PI 假设最大云量时间的这种变化对大气的太阳加热产生影响，从而构成正反馈，在活动阶段增强对流并在抑制阶段抑制对流。 将进行进一步的计算机模拟来检验这一假设。最后，PI 将使用全局高分辨率非静水力模型（ICON 模型）对 DYNAMO 现场活动期间观察到的 MJO 事件（参见 AGS-1022899）进行模拟。 模拟结果将用于进一步测试昼夜周期对 MJO 的假设影响。如上所述，由于 MJO 对全球天气和气候的影响以及这项研究改善 MJO 预报的潜力，这项工作具有更广泛的社会影响。 此外，这项工作还为 PI 职业生涯的早期阶段提供支持，从而促进研究领域的未来劳动力。 此外，这项工作是在德国汉堡马克斯·普朗克气象研究所 (MPI-M) 的 Cathy Hohenegger 博士的监督下进行的。 主办机构是世界顶级的气候模拟中心之一，美国 PI 和 MPI-M 科学家之间的科学合作预计将有利于美国研究界。该奖项得到了国际科学与工程办公室的资助，以及气候和大尺度动力学计划。

项目成果

Diurnal Cycle of the ITCZ in DYNAMO

DYNAMO 中 ITCZ 的昼夜周期

• DOI: 10.1175/jcli-d-17-0670.1
• 发表时间: 2018
• 期刊: Journal of Climate
• 影响因子: 4.9
• 作者: Ciesielski, Paul E.;Johnson, Richard H.;Schubert, Wayne H.;Ruppert, James H.
• 通讯作者: Ruppert, James H.

Diurnal Cloud and Circulation Changes in Simulated Tropical Cyclones

• DOI: 10.1029/2018gl081302
• 发表时间: 2019-01
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: J. Ruppert;Morgan E. O'Neill

The Two Diurnal Modes of Tropical Upward Motion

• DOI: 10.1029/2018gl081806
• 发表时间: 2019-03
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: J. Ruppert;D. Klocke

Diurnal Circulation Adjustment and Organized Deep Convection

• DOI: 10.1175/jcli-d-17-0693.1
• 发表时间: 2018-04
• 期刊: Journal of Climate
• 影响因子: 4.9
• 作者: J. Ruppert;C. Hohenegger