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

该奖项支持为期两年的博士后研究奖学金，在该奖学金中，PI将研究日周期对马登-朱利安振荡(MJO)的影响。MJO是在印度洋上空形成的一大片对流和降雨区域，向东缓慢传播到赤道中部太平洋。MJO影响世界各地的天气和气候，影响墨西哥湾飓风的形成，影响美国西海岸产生洪水和山体滑坡的大气河流，以及厄尔尼诺事件的爆发等影响。尽管MJO很重要，经过几十年的共同努力，但MJO还没有得到充分的解释，天气和气候模型很难模拟和预测它。该奖项的研究涉及日循环的两个方面，第一个方面是海表面温度(SST)日循环对增湿上层大气的影响。当MJO处于“抑制”阶段，在没有有组织的对流和降雨的情况下，晴朗的天气占主导地位时，SST有一个相对明显的日循环。SST的日循环预计将导致更大的表面蒸发和整个低层大气中水汽的更强烈的垂直混合，总体增湿有助于促进MJO的“活跃”阶段的开始。利用一套计算机模拟来确定SSTs的日循环对于增湿大气和促进MJO的重要性，进一步的研究考虑了MJO的抑制和活跃阶段之间的云的日循环的变化。抑制相的小而不发达的云优先出现在下午，而活动相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构成正反馈的大气的太阳加热有影响，在活动阶段增强对流，在抑制阶段抑制对流。最后，PI将使用全球高分辨率非静力模式(ICON模式)对在发电机现场活动期间观察到的MJO事件(见AGS-1022899)进行模拟。模拟的结果将被用来进一步检验假设的日循环对MJO的影响。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，这项工作还支持PI在其职业生涯的早期阶段，从而促进未来在研究领域的劳动力。此外，这项工作是在德国汉堡的马克斯·普朗克气象研究所(MPI-M)进行的，由Cathy Hohenegger博士监督。主办机构是世界顶尖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有望使美国研究界受益。该奖项得到了国际科学与工程办公室以及气候和大型动力学计划的资助。

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.