Aerosol ­Cloud ­Precipitation Interactions

METEO 597.2: 

Aerosol-Cloud-Precipitation Interactions
Spring 2018 

Instructors: Matthew R. Kumjian & Jerry Y. Harrington

Offices: 513 & 517 Walker Building

Phone: (814)-863-1581 & (814)-863-1584

Email:  &

Class Meetings: Monday, 3:35 pm - 5:30 pm, Walker Building Room 105.

Office Hours: Wednesday, 4:30 - 6:00 pm (MK); TBD (JH).

Class Structure: Two-credit seminar course.

This seminar course is designed for graduate students with an active interest in the evolution of cloud systems. This semester, we will focus on the following:

Aerosol particles control most of the nucleation of the liquid and ice phase in cloud systems. We may therefore expect that changes in aerosol populations through natural and anthropogenic processes could have important impacts on the microphysics, absorbed and scattered radiation, and the dynamics of shallow and deep convective cloud systems. However, the strength of the response of a given cloud system to perturbations in aerosol concentrations depends on many factors, including radiative responses, thermal responses, and conditioning of the cloud system by the larger environment. During the semester, we will attempt to unravel the known physical, dynamical, and larger scale factors that govern the interactions of aerosols with clouds. We will focus primarily on shallow layered clouds and deep convective clouds because most of the research done on this topic has been focused on these two cloud types. We will discuss and expose some of the controversies associated with the possible impacts of aerosol on invigorating deep convection, and what the results may mean for measuring aerosol responses in the atmospheric system. 

Structure and Expectations:

The course will consist of lectures followed by student presentations. The lectures will provide a basic overview of the topic. Following the one or two weeks of lectures, students will present a topic to the class. The topic will most often be covered in a key paper along with one or two other satellite papers. The student presentations will be between 15 minutes and 20 minutes in length, and will be a well-prepared Powerpoint (or other appropriate software) talk. Immediately following the talk, we will discuss the finer details of the topic and relate the ideas to prior class materials including lectures and papers.


Grades in this course will be based on:

  • 50%: The quality of the presentation and the quality of the discussions instigated and maintained by the student.
  • 50%: The final synthesis/summary paper, due the last day of class. 

Final Paper:

The final paper should be a synthesis or summary, in your view, of the issues and concepts discussed throughout the semester. The focus may be on the entirety of aerosol-cloud-precipitation interactions, or some component of it that we covered. It should incorporate papers discussed in class, and any additional sources relevant to your summary. It should be no 5-10 pages in length (double spaced, 12-point font, not including references or figures), and free from grammatical or typographical errors.


  • Week 1: Overview of aerosol and their importance to cloud phase nucleation, latent heating and basic cloud dynamics (background: chapters).
  • Week 2: Overview of deep convective dynamics and microphysics and where aerosol processes may have important impacts on these larger cloud systems (heating; anvils; updraft dynamics; precipitation production; RKW; etc.)
  • Week 3: Twomey's hypothesis on cloud albedo effect, bistability of CCN (Twomey 1974, 1977; Twomey et al. 1984; Baker and Charlson 1990; Ackerman et al. 1994).
  • Week 4: Drizzle impacts on aerosol perturbations (cloud lifetime effect) (Albrecht 1989; Xue and Feingold 2006)
  • Week 5: Solar absorption by droplets/aerosol (semi-direct effect) (Ackerman et al. 2000; Feingold et al. 2005; Sandu et al. 2008)
  • Week 6: Cloud depth effects/entrainment feedbacks (Pincus and Baker 1994; Wood 2007; Savic-Jovic and Stevens 2008)
  • Week 7: Glaciation indirect effect (mixed-phase clouds) (Jiang et al. 2000; Lohmann et al. 2002)
  • Week 8: Buffering of cloud systems (Stevens and Feingold 2009; Morrison et al. 2011)
  • Week 9: Convective Invigoration (via freezing: Rosenfeld et al. 2008; via condensation: Sheffield et al. 2015). Supp: Koren et al. 2008.
  • Week 10: Convective Invigoration…in context (Lebo et al. 2018)
  • Week 11: Anvil/Radiative effects (Morrison and Grabowski 2011; Fan et al. 2013)
  • Week 12: Precipitation Production – cold pools/RKW/squall lines (Fan et al. 2009; Lebo and Morrison 2014); Supp: Khain et al. 2009; Clavner et al. 2018.
  • Week 13: Precipitation Production – hailstorms (Khain et al. 2011; Loftus and Cotton 2014); Supp: Noppel et al. 2010; Carrio et al. 2014.
  • Week 14: Extraordinary Claims – is there extraordinary evidence? (Li et al. 2011; Fan et al. 2015).
  • Week 15: Extraordinary Claims – is there extraordinary evidence? (Rosenfeld and Bell 2011 and Comment/Reply; Saide et al. 2015) 


Students who do not meet the prerequisites after being informed in writing by the in- structor may be dis-enrolled during the first 10-day free add-drop period (Error! Hyperlink reference not valid.). If you have not completed the listed prerequisites, then promptly consult with the instructor if you have not done so already. Students who re-enroll after being dis-enrolled according to this policy are in violation of item 15 on the Student Code of Conduct (

Academic Integrity

Students are expected to complete the required work for this class on their own or in designated lab groups (when permitted), including quizzes, draft report sections, and the final snowfall measurement report.  Students who present other people’s work as their own will receive at least a 0 on the assignment and may well receive an F or XF in the course.  For information about the Earth and Mineral Sciences Academic Integrity Policy, which this course adopts, please see  To learn more, see Penn State’s Plagiarism Tutorial for Students.  

Course Copyright

All course materials students receive or to which students have online access are protected by copyright laws. Students may use course materials and make copies for their own use as needed, but unauthorized distribution and/or uploading of materials without the instructor’s express permission is strictly prohibited. University Policy AD 40, the University Policy Recording of Classroom Activities and Note Taking Services addresses this issue. Students who engage in the unauthorized distribution of copyrighted materials may be held in violation of the University’s Code of Conduct, and/or liable under Federal and State laws.  For example, uploading completed labs, homework, or other assignments to any study site constitutes a violation of this policy. 

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Disclaimer Statement

Please note that the specifics of this Course Syllabus can be changed at any time, and you will be responsible for abiding by any such changes. Changes to the syllabus shall also be given to the student in written (paper or electronic) form. 

Additionally, Matt Kumjian is "Safe Zone" trained and welcome students who need a safe space to contact me at any time.