Collaborative Research: Self-Aggregation of Moist Convection, Radiative-Convective Instability, and the Regulation of Tropical Climate

热带阵雨和雷暴在调节地球气候方面起着重要作用。 关于热带对流的一个理论是，随着海面温度升高，更多的云形成，大气变得干燥。 虽然云层减少了使地表变暖的太阳辐射，但这种影响被更干燥的大气层所抵消，允许更多的辐射通过。 这可能表明热带气候具有一定程度的自我调节能力。 为了研究这一想法，参与该项目的研究人员创建了一个理想化的计算机模型，以解决他们所谓的对流“自聚集”问题。 这是云和雷暴一起移动成簇的趋势。 该奖项将提供资金，以增强模型，使其具有更真实的风和海面温度。 这项研究的影响将是通过改进天气和气候模式中热带对流的代表性。 该项目还将通过让多名研究生参与研究来帮助培养下一代科学家。该项目的总体目标是了解在更真实地代表热带的环境中对流的聚集如何有助于调节热带气候。 相关的假设是，聚集提供了一个强大的负水汽反馈，是高度依赖于温度，从而降低了热带气候的敏感性。 研究人员将在他们的模拟中引入日周期和风切变，以减少或消除他们在先前工作中发现的强聚集状态锁定。 海洋表面温度也可以变化，这将使研究人员能够测试以下假设，即聚集的存在可能会推动系统的气候接近聚集的临界海洋表面温度。 下一步将使用理论模型，通过改变太阳常数和CO2来探索系统的气候敏感性。 最后，研究人员将测试一个假设，即Madden-Julian振荡（MJO）是由对流的自聚集引起的，与较大的大气波无关。

Tropical showers and thunderstorms play an important role in the regulation of Earth's climate. One theory regarding tropical convection is that as sea surface temperatures warm, more clouds form and the atmosphere becomes drier. While the clouds reduce solar radiation from warming the surface, that effect is more than counteracted by a drier atmosphere allowing more outgoing radiation to pass. This could suggest that the tropical climate has a level of self-regulation. To study this idea, the researchers involved in this project have created an idealized computer model to address what they call the "self-aggregation" of convection. This is the tendency for clouds and thunderstorms to move together into clusters. This award will provide funding to enhance the model with more realistic wind and sea surface temperatures. The impact of this research would be through improvements in the representation of tropical convection in weather and climate models. The project would also help to train the next generation of scientists by involving multiple graduate students in the research.The overarching goal of the project is to understand how aggregation of convection in an environment more realistically representative of the tropics may help regulate tropical climate. The related hypothesis is that aggregation reduces tropical climate sensitivity by providing a powerful negative water vapor feedback that is highly temperature dependent. The researchers will introduce a diurnal cycle and wind shear to their simulations in order to decrease or eliminate the strong aggregation state lock that they found in their prior work. Sea surface temperatures would also be allowed to vary, which will let the researchers test the hypothesis that the existence of aggregation may drive the system's climate toward the critical sea surface temperature for aggregation. The next step will be to use the theoretical model to explore the climate sensitivity of the system by varying the solar constant and CO2. Finally, the researchers will test the hypothesis that the Madden-Julian Oscillation (MJO) results from self-aggregation of convection independent of larger atmospheric waves.