CAREER: Understanding the Coupling between Clouds and Midlatitude Dynamics at Synoptic and Global Scales

点击翻译按钮获取中文摘要

The typical pattern of clouds around a mid-latitude cyclone features high clouds east of the center and along the trailing cold front, and low clouds in the cold sector to the west. This general pattern has been known since the 1920s but the role of the clouds in cyclone evolution, and the effects of the cloud pattern on atmospheric circulation and climate, are still under study. The topic is of practical as well as scientific interest as clouds can only be represented in approximate form in current weather and climate models, and cloud errors limit the quality of simulations and forecasts. Results of the work have direct bearing on the quality of weather forecasts and climate projections used to provide guidance to decision makers and the public. In addition, the educational activities supported under this CAREER award advance science teaching at the high school, college, and graduate levels.The research focuses specifically on cloud radiative effects (CREs), meaning the cooling caused by clouds as they reflect shortwave solar radiation back to space and the warming effect when they intercept outgoing longwave radiation emitted by the earth. In the deep clouds found in the eastern sector the longwave and shortwave effects show large cancellation, while shortwave cooling dominates in the low clouds on the western side. Preliminary work by the PI shows that, at least in the Southern Hemisphere, CRE evolves over the lifecycle of the cyclone, forming a north-south dipole during the decay phase with warming on the equatorward side. The north-south CRE dipole in the decaying stage could affect the meridional temperature gradient along the SH storm track, possibly helping to reestablish the meridional temperature contrast after cyclone passage and thus promoting further cyclone activity or influencing the latitude of the upper-level jet stream. The radiative effect of clouds around cyclones could also influence the behavior of low-frequency climate variability and secular climate change, both of which involve latitudinal shifts of jet streams and storm tracks. The work considers the dynamic and thermodynamic controls on the clouds as well as the influence of clouds on the midlatitude circulation. It is conducted through a combination of observational analysis and model simulation.The educational component of the project includes efforts at the high school, college, and graduate level. At the high school level, the PI works with education experts at the Center for Teaching Excellence on the UVA campus, the Environmental Studies Academy (ESA) at Western Albermarle High School, and the University Corporation for Atmospheric Research (UCAR). The goal is to develop a teaching module to introduce high school students to the role of clouds in the climate system. The module will be disseminated nationally through the web portal at UCAR. Undergraduate education is promoted through the development of a course on climate modeling and analysis. One issue addressed by the course is the lack of computer skills commonly found among undergraduates, which limits their ability to engage in scientific research. The course involves training in the use of data analysis software and hands-on projects conducted by groups of two to three students. Students from the class are recruited to conduct research in the summers, with emphasis on the recruitment and retention of underrepresented minorities. On the graduate level, the project supports two students who, in addition to their research and classwork, serve as mentors for undergraduate students.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.