Mike Pritchard.

Cloud Super-Parameterization Research.


Ph.D. Candidate
Scripps Institution of Oceanography
University of California San Diego
9500 Gilman Drive, La Jolla CA, 92093-0224
Phone: 858-534-6589
Email: mikepritchard (at) ucsd.edu


Graduation date: August, 2011.
Next steps: NOAA postdoc with Chris Bretherton and Tom Ackerman, at UW, starting in October.
Curriculum Vitae


Current Research

My research is being done at the Scripps Institution of Oceanography under the supervision of Richard Somerville in affiliation with a new NSF Science and Technology Center, The Center for Multiscale Modeling of Atmospheric Processes.

I'm exploring a candidate next generation climate projection technique for better representing cloud processes in climate models, called "super-parameterization". See CMMAP's web-page above for more details on this technqiue.

I've become intrigued by prototype super-parameterized climate models, a.k.a. multi-scale modeling frameworks (MMFs), since appreciating that they produce improved representations of several convectively influenced atmospheric modes of variability, which are distorted in ordinary climate models. Improvements have recently been documented on a range of timescales, from interannual (ENSO), intraseasonal (the Madden Julian Oscillation), and the diurnal cycle of rainfall. This suggests something deeply physical is improved using the MMF approach. But there are unphysical aspects as well- MMFs are in their infancy and there are some philosophical problems with their design and in their simulated mean state cloudiness and rainfall (e.g. these models exhibit a ``supermonsoon'', have too thick high clouds, and a giant blob of rain in the tropical western Pacific that shouldn't be there). Although it is currently unknown if such problems can be remedied, it is possible that with additional research and tuning, this prototype class of model may one day be applied to improve the scientific understanding of how feedbacks between cloud processes and broader climate evolution might operate in nature.

Recently, I discovered a surprisingly robust signal of propagating nocturnal warm season convection over North America in CMMAP's prototype super-parameterized GCM. I've been trying to understand this result, in collaboration with Mitch Moncrieff, an expert on this organized convective phenomenon at the National Center for Atmospheric Research. The result was a surprise because the physics governing this nocturnal rainfall signal in nature are notoriously difficult to simulate in a coarse resolution global model, and prior to our finding it there were good reasons to think that the trade-offs in the MMF approach ought not to admit it. A JAS paper is in press about this topic now, linked below.

In 2009, I published a couple of papers evaluating the diurnal, or daily, cycle of rainfall as simulated by a prototype MMF being developed by the Center for Multiscale Modeling of Atmpsheric Processses (CMMAP), based at Colorado State University. In general, the space-time variability of the daily cycle of surface rainfall in the MMF looks much closer to reality (as measured from spaceborne geosynchronous radiometers and orbiting radar/lidar), but understanding why is difficult. For my PhD dissertation, I'm trying to unravel the physical mechanisms that result in improved multi-scale convective diurnal dynamics in MMFs across coastlines.


Annotated Bibliography

Check out my annotated bibliography: I maintain this personal research collection containing evolving summaries, notes, and questions on some of the memorable papers I've read during my PhD. Fair warning - the content reflects a grad student's evolving perspective over five years, so don't trust a lot of the speculation that you read here!

Full Bibliography
Things I've Read
Things I Haven't Read


Publications

Pritchard, M. S., M. W. Moncrieff and R. C. J. Somerville (2011).
Orogenic propagating precipitation systems over the US in a global climate model with embedded explicit convection
In Press, Journal of the Atmospheric Sciences

Pritchard, M. S. and R. C. J. Somerville (2009).
Assessing the diurnal cycle of precipitation in a multi-scale climate model.
Journal of Advances in Modeling Earth Systems, 1, Art. No. 12.

Pritchard, M. S. and R. C. J. Somerville (2009).
Empirical orthogonal function analysis of the diurnal cycle of precipitation in a multi-scale climate model.
Geophysical Research Letters 36(5), L05812.

Pritchard, M. S., A. B. G. Bush and S. J. Marshall (2008).
Interannual atmospheric variability affects continental ice sheet simulations on millennial time scales.
Journal of Climate 21 (22), 5976-5992.

Pendlebury, D., T. G. Shepherd, M. S. Pritchard, and C. McLandress (2008).
Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere.
Atmospheric Chemistry and Physics Discussion 8 (7), 1925-1935

Pritchard, M. S., A. B. G. Bush and S. J. Marshall (2008).
Neglecting ice-atmosphere interactions underestimates ice sheet melt in millennial-scale deglaciation simulations.
Geophysical Research Letters 35 (1), L01503.


Select Posters

Dynamical aspects of convectively coupled diurnal rainfall systems in the lee of the Rockies in the Super-Parameterized Community Atmosphere Model v. 3.5, CMMAP Team Meeting, Ft. Collins, August 2010.

Aspects of orogenic mesoscale convective organization admitted by a global multi-scale climate modeling framework, AGU Fall Meeting, San Francisco, December 2009.

Towards understanding why super-parameterization improves the simulated composite daily rainfall cycle in multi-scale climate modeling frameworks, CMMAP Team Meeting, Ft. Collins, July 2009.

Assessing the diurnal cycle of precipitation in a multi-scale climate model, CMMAP Team Meeting, Ft. Collins, July 2008.

Sensitivity of a Numerical Ice Sheet Model to Interannual Climate Forcing and Interactive Atmosphere-Ice Sheet Coupling, AGU Fall Meeting, San Francisco, December 2008.

Assessing the diurnal cycle of precipitation in a multi-scale climate model, CMMAP Team Meeting, Ft. Collins, July 2008.



Course Notes

One of the great things (besides surfing) about being a grad student at Scripps, is that we grad students often band together to run our own courses on topics of interest. Here are some links to courses that I've helped organize:

Clouds and Convection
Regional Climate Change Impacts

MSc Research

Over the course of my MSc research under Andrew Bush at the University of Alberta, I studied ice sheet-atmosphere interactions on paleoclimate timescales. During this time, I developed a coupling infrastructure to exchange state information between a dynamic ice sheet model developed by Shawn Marshall at the University of Calgary and the Community Atmosphere Model. For my MSc thesis, I explored several early phase atmosphere-ice sheet coupling issues using this new tool. I remain interested in low-frequency atmosphere-ice sheet interactions on millennial timescales, but for the time being am exploring faster dynamics that are better observed in nature.

I have packaged my atmosphere-ice sheet coupling script infrastructure for distribution to potential research collaborators; contact me if you are interested in it.

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