• University of California-San Diego
  • 9500 Gilman Drive
  • La Jolla CA 92093-0532 USA
  • Tel: 1-858-534-0000
  • Fax: 1-858-534-0000

EaSM Project: Aerosol-Cloud-Earth Feedbacks


Principal Investigator
Lynn Russell has conducted measurement and modeling experiments of aerosol indirect effects since 1994 [9, 10]. Her recent work includes using a counter-flow inlet to measure organic and elemental composition of un-activated and activated aerosol particles in cloud. The analyses have characterized many of the key microphysical features of stratocumulus clouds, showing a strong relationship between “accumulation mode” particle number and droplet number, resulting in contributions to three peer-reviewed publications [12, 13, 14]. This work set the stage for showing that these aerosol particles in the eastern Pacific were internally mixed, so that chemical composition played a much more subtle role than particle size in providing cloud condensation nuclei that activated at measured supersaturations [11]. This work led to further studies of aerosols in stratocumulus-topped boundary layers as part of VOCALS-REx [15].

UCSD Investigators
Guang Zhang has been working on convection parameterization and global climate simulation for 20 years. He developed the Zhang-McFarlane convection scheme, which has been used in all versions of the NCAR GCMs since 1995. His recent work uses the NCAR CAM3 and CCSM3 to understand how an improved convection parameterization scheme he developed impacts the simulation of tropical climate and its variability. The project has resulted in 10 peer reviewed journal publications [21-30]. The findings from the project include: 1) Modifications to the Zhang-McFarlane scheme lead to significantly enhanced MJO and improved MJO structures. The interaction between convection, moisture and convergence in the lower troposphere is found to be responsible for the MJO development over the Indian Ocean and the western Pacific in both observations and simulations. 2) The improved Zhang-McFarlane convection scheme is able to eliminate the double ITCZ in boreal summer. The analysis of CCSM3 simulations shows that the when the improved convection scheme is used, the coupled feedbacks among atmospheric convection, large-scale circulation and ocean dynamic heat transport are responsible for the reduction of SST and precipitation biases in the southern ITCZ region.

Art Miller has four recent related to decadal variability: (1) Analysis of Decadal Variability in the North Pacific: Miller and Schneider explored Pacific decadal variability in observations, theoretical models, ocean hindcasts and coupled models. (2) Dynamics of Ocean Climate Changes in the Gulf of Alaska: Miller worked with Di Lorenzo, Capotondi and Alexander on modeling the observed seasonal cycle, transient spin-up and decadal mesoscale eddy and larger-scale variations of the Gulf of Alaska. (3) Decadal coupled ocean-atmosphere interactions in the North Pacific: Miller is working with Schneider to downscale large-scale observed decadal ocean-atmosphere variability over the North Pacific using SCOAR to isolate the portion of the atmospheric response that is due to oceanic feedbacks. (4) VOCALS: Mesoscale Ocean Dynamical Analysis with Synoptic Data Assimilation and Coupled Ocean– Atmosphere Modeling: Ocean data assimilation of the VOCALS cruises is currently being executed along with regional coupled-ocean modeling experiments exploring the sensitivity of atmospheric flows to oceanic SST in the VOCALS domain.

Dan Cayan has directed the NOAA California-Nevada Regional Integrated Sciences and Assessments Center, “The California Applications Program,” from 1999 through present http:// This multi-investigator, multi-institutional center has provided research and decision support to stakeholders in the region through a wide range of peer-reviewed publications [44-50]. Thrusts of this applied research have included impacts of climate variability and climate change on water resources, wildfire, human health and agriculture. A particular emphasis that was developed involves assisting the State of California in its effort to assess its vulnerability and plan to adapt to climate change, in the midst of other stresses including population growth and land use change.

Richard Somerville has been a team member of CMMAP, the Center for Multiscale Modeling of Atmospheric Processes, an NSF Science and Technology Center, since this center was established in 2006. Somerville served as one of the lead authors for the Working Group 1 report of IPCC in 2007 [16]. Research carried out by Somerville and his graduate student Michael Pritchard with CMMAP support has been reported at many meetings and in two recent papers [17, 18]. In addition, Somerville is an editor of a multi-authored book prepared under CMMAP, The Development of Atmospheric General Circulation Models, now in press at Cambridge University Press [19]. Somerville has also authored and revised a book on the atmosphere for general audiences [20].

David Pierce has extensive experience analyzing model simulations of climate variability, particularly in the North Pacific and western U.S., on timescales associated with ENSO, decadal variability, and secular anthropogenic changes. Pierce and colleagues examined the quality of regional climate model simulations on the western U.S. and other selected locations around the globe, and how to best combine multi-model information into an ensemble simulation [51, 52]. Pierce also was part of a team that examined 50 years of snowpack, temperature, and streamflow records across the western U.S. to quantify the relative effects of anthropogenic climate change and natural climate variability over that period [52-56]. Pierce and colleagues examined various aspects of model validation and low-frequency climate variability over the North Pacific, including the role of sea surface temperatures in the interaction between ENSO and the Pacific Decadal Oscillation, the physical mechanisms of low-frequency climate variability in the North Pacific, and how anthropogenic forcing of the North Pacific might affect the biology there [8, 57-61]. Pierce wrote and operationally maintains the Scripps ENSO forecast system [62].

UCM Investigator
Tony Westerling has carried out research on the analysis and modeling of climate-vegetation- wildfire relationships on seasonal to decadal and longer time scales, including the effects of wildfire on particulate emissions and on ozone production. A particular interest has been to assess the effects of climate variability and change on emissions due to wildfires. His work on wildfire histories and climate in the western U.S. established that forest wildfire activity has increased dramatically in the western US in recent decades, driven by warming and earlier springs.

PNNL Investigators
Steve Ghan has been working on the aerosol indirect effects problem since 1990. He produced the first physically-based parameterization of aerosol activation [1] and was the first to introduce prognostic droplet number in a global model [2]. He also led the development of the modal aerosol lifecycle scheme [31] that will be released with his aerosol activation scheme [5] in CAM5 and CESM1 in June 2010. He used an earlier version of the scheme to estimate direct and indirect effects of anthropogenic aerosol in a global model [32]. He has also recently led the development of the first MMF with cloud-aerosol interactions [7].

Xiaohong Liu developed one of the first ice nucleation parameterizations for GCMs [33] which considers both the homogeneous and heterogeneous nucleation and transition between the two mechanisms. The parameterization was implemented in the NCAR CAM [34] to investigate the impacts of anthropogenic aerosol on ice clouds and climate [35] and on stratospheric water vapor [36]. This ice nucleation parameterization has been adopted in the CAM5 [37] in the NOAA GFDL AM3 [38] and in the NASA GEOS-5 model [39].

Mikhail Ovchinnikov has been engaged in developing, evaluating, and applying models to study microphysics, radiative and aerosol effects in clouds for 20 years. His work includes improvements in model’s physics [40] and numerics [41]. He applied cloud-resolving models to benchmark GCM parameterizations and conducted the first evaluation of MMF using ground- based DOE ARM observations [42]. Recently, he led the project in which a high-resolution cloud model with size-resolved microphysics was applied to study ice formation in Arctic clouds [43] and to investigate aerosol effects on deep convection [43].

NCAR Investigator
Sungsu Park was appointed as a Scientist I at NCAR on 1 January 2009. Sungsu has been working on developing and implementing moist turbulence [6], shallow convection [3] and cloud macrophysics [4] parameterizations for CAM5. He has been doing extensive test and tuning simulations using the suite of new parameterizations.


1. Abdul-Razzak, H. and S. Ghan, A parameterization of aerosol activation: 2. Multiple aerosol types. J. Geophys. Res, 2000. 105(D5): p. 6837-6844.
2. Ghan, S., et al., Prediction of cloud droplet number in a general circulation model. Journal of Geophysical Research, 1997. 102(D18): p. 21777.
3. Park, S. and C.S. Bretherton, The University of Washington Shallow Convection and Moist Turbulence Schemes and Their Impact on Climate Simulations with the Community Atmosphere Model. Journal of Climate, 2009. 22(12): p. 3449-3469.
4. Park, S., C. Bretheron, and P.J. Rasch, The revised cloud macrophysics and its impact on climate simulations with the community atmopshere model. 2010, in preparation.
5. Gettelman, A., H. Morrison, and S. Ghan, A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part II: Single-Column and Global Results. Journal of Climate, 2008. 21(15): p. 3660-3679.
6. Bretherton, C.S. and S. Park, A New Moist Turbulence Parameterization in the Community Atmosphere Model. Journal of Climate, 2009. 22(12): p. 3422-3448.
7. Gustafson Jr, W., et al., The Explicit-Cloud Pparameterized-Pollutant hybrid approach for aerosolĖcloud interactions in multiscale modeling framework models: tracer transport results. Environmental Research Letters, 2008. 3: p. 025005.
8. Schneider, N., A. Miller, and D. Pierce, Anatomy of North Pacific decadal variability. Journal of Climate, 2002. 15(6).
9. Pandis, S., L. Russell, and J. Seinfeld, The relationship between DMS flux and CCN concentration in remote marine regions. Journal of Geophysical Research, 1994. 99(D8): p. 16945.
10. Russell, L., S. Pandis, and J. Seinfeld, Aerosol production and growth in the marine boundary layer. J. Geophys. Res., 1994. 99: p. 20,989-21,003.
11. Hawkins, L., et al., Uniform particle-droplet partitioning of 18 organic and elemental components measured in and below DYCOMS-II stratocumulus clouds. Journal of Geophysical Research, 2008. 113(D14): p. D14201.
12. Stevens, B., et al., Dynamics and chemistry of marine stratocumulus - Dycoms-II. Bulletin of the American Meteorological Society, 2003. 84(5): p. 579-+.
13. Twohy, C.H., et al., Evaluation of the aerosol indirect effect in marine stratocumulus clouds: Droplet number, size, liquid water path, and radiative impact. Journal of Geophysical Research-Atmospheres, 2005. 110(D8).
14. Petters, M., et al., Accumulation mode aerosol, pockets of open cells, and particle nucleation in the remote subtropical Pacific marine boundary layer. Journal of Geophysical Research-Atmospheres, 2006. 111(D2): p. D02206.
15. Hawkins et al., L., Carboxylic Acids, Sulfates, and Organosulfates in Processeed Continental Aerosol over the South East Pacific Ocean during VOCALS-REx 2008. Journal of Geophysical Research, 2010 in press.
16. Solomon, S., et al., IPCC, 2007: Summary for Policymakers. Climate Change, 2007.
17. Pritchard, M. and R. Somerville, Assessing the Diurnal Cycle of Precipitation in a Multi-Scale Climate Model. Journal of Advances in Modeling Earth Systems, 2009. 1(12).
18. Pritchard, M. and R. Somerville, Empirical orthogonal function analysis of the diurnal cycle of precipitation in a multi-scale climate model. Geophysical Research Letters, 2009. 36(5): p. L05812.
19. Randall, D., The Development of Atmospheric General Circulation Models. 2010: Cambridge University Press
20. Somerville, R., The Forgiving Air: Understanding Environmental Change 2nd EDITION. 2008: University of California Press.
21. Collier, J. and G. Zhang, Aerosol direct forcing of the summer Indian monsoon as simulated by the NCAR CAM3. Climate Dynamics, 2009. 32(2): p. 313-332.
22. Li, G. and G. Zhang, Understanding biases in shortwave cloud radiative forcing in the National Center for Atmospheric Research Community Atmosphere Model (CAM3) during El Nino. Journal of Geophysical Research, 2008. 113(D2): p. D02103.
23. Mu, M. and G. Zhang, Energetics of Madden-Julian oscillations in the National Center for Atmospheric Research Community Atmosphere Model version 3 (NCAR CAM3). Journal of Geophysical Research, 2006. 111(D24): p. D24112.
24. Mu, M. and G. Zhang, Energetics of Madden Julian Oscillations in the NCAR CAM3: A composite view. Journal of Geophysical Research-Atmospheres, 2008. 113(D5): p. D05108.
25. Song, X., D. Lubin, and G. Zhang, Increased greenhouse gases enhance regional climate response to a Maunder Minimum. Geophysical Research Letters, 2009. 37(1): p. L01703.
26. Song, X., et al., Understanding the Effects of Convective Momentum Transport on Climate Simulations: The Role of Convective Heating. Journal of Climate, 2008. 21(19): p. 5034-5047.
27. Song, X. and G. Zhang, Convection Parameterization, Tropical Pacific Double ITCZ, and Upper-Ocean Biases in the NCAR CCSM3. Part I: Climatology and Atmospheric Feedback. Journal of Climate, 2009. 22: p. 16.
28. Zhang, G., Effects of entrainment on convective available potential energy and closure assumptions in convection parameterization. J. Geophys. Res, 2009. 114.
29. Zhang, G. and X. Song, Convection Parameterization, Tropical Pacific Double ITCZ, and Upper Ocean Biases in the NCAR CCSM3, Part II: Coupled Feedback and the Role of Ocean Heat Transport. Journal of Climate, 2009. 23: p. 800.
30. Zhang, G. and X. Song, Interaction of deep and shallow convection is key to Madden-Julian Oscillation simulation. Geophysical Research Letters, 2009. 36: p. L09708.
31. Easter, R., et al., MIRAGE: Model description and evaluation of aerosols and trace gases. J. Geophys. Res, 2004. 109: p. D20210.
32. Ghan, S., et al., A physically based estimate of radiative forcing by anthropogenic sulfate aerosol. Journal of Geophysical Research, 2001. 106(D6): p. 5279-5293.
33. Liu, X. and J. Penner, Ice nucleation parameterization for global models. Meteorologische Zeitschrift, 2005. 14(4): p. 499-514.
34. Liu, X., et al., Inclusion of Ice Microphysics in the NCAR Community Atmospheric Model Version 3 (CAM3). Journal of Climate, 2007. 20: p. 18.
35. Liu, X., J. Penner, and M. Wang, Influence of anthropogenic sulfate and black carbon on upper tropospheric clouds in the NCAR CAM3 model coupled to the IMPACT global aerosol model. Journal of Geophysical Research-Atmospheres, 2009. 114(D3): p. D03204.
36. Su, H., et al., Enhanced water vaport transport to the stratosphere by pollutants in Asia. 2010, in revision.
37. Gettelman, A., et al., Global simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the community atmospheric model. Journal of Geophysical Research, 2010, in press.
38. Salzmann, M., et al., Two-moment bulk stratiform cloud microphysics in the GFDL AM3 GCM: description, evaluation, and sensitivity tests. Atmos. Chem. Phys. Discuss, 2010. 10: p. 6375-6446.
39. Sud, Y., et al., Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions Part 1: Africa and India. Ann. Geophys, 2009. 27: p. 3989-4007.
40. Ovtchinnikov, M. and Y. Kogan, An investigation of ice production mechanisms in small cumuliform clouds using a 3D model with explicit microphysics. Part I: Model description. Journal of the Atmospheric Sciences, 2000. 57(18): p. 2989-3003.
41. Ovtchinnikov, M. and R. Easter, Nonlinear Advection Algorithms Applied to Interrelated Tracers: Errors and Implications for Modeling Aerosol-Cloud Interactions. Monthly Weather Review, 2009. 137(2): p. 632-644.
42. Ovtchinnikov, M., et al., Evaluation of the multiscale modeling framework using data from the atmospheric radiation measurement program. Journal of Climate, 2006. 19(9): p. 1716-1729.
43. Fan, J., et al., Ice formation in Arctic mixed-phase clouds: Insights from a 3-D cloud-resolving model with size-resolved aerosol and cloud microphysics. Journal of Geophysical Research-Atmospheres, 2009. 114(D4): p. D04205.
44. Cayan, D., et al., Climate change projections of sea level extremes along the California coast. Climatic Change, 2008. 87: p. 57-73.
45. Cayan, D., et al., Climate change scenarios and sea level rise estimates for the California 2008 Climate Change Scenarios Assessment. California Climate Change Center CEC-500-2009-014-D, 2009.
46. Gershunov, A., D. Cayan, and S. Iacobellis, The Great 2006 heat wave over California and Nevada: Signal of an Increasing Trend. Journal of Climate, 2009. 22: p. 6181.
47. Reisen, W., et al., Impact of climate variation on mosquito abundance in California. Ecology, 2008. 33(1): p. 89-98.
48. Stewart, I., D. Cayan, and M. Dettinger, Changes toward earlier streamflow timing across western North America. Journal of Climate, 2005. 18(8): p. 1136-1155.
49. Westerling, A., et al., Warming and earlier spring increase western US forest wildfire activity. Science, 2006. 313(5789): p. 940.
50. Westerling, A.L., et al., Warming and earlier spring increase western US forest wildfire activity. Science, 2006. 313(5789): p. 940-943.
51. Santer, B., et al., Incorporating model quality information in climate change detection and attribution studies. Proceedings of the National Academy of Sciences, 2009. 106(35): p. 14778.
52. Pierce, D., et al., Selecting global climate models for regional climate change studies. Proceedings of the National Academy of Sciences, 2009. 106(21): p. 8441.
53. Barnett, T., et al., Human-induced changes in the hydrology of the western United States. Science, 2008. 319(5866): p. 1080.
54. Bonfils, C., et al., Detection and Attribution of Temperature Changes in the Mountainous Western United States. Journal of Climate, 2008. 21: p. 23.
55. Pierce, D., et al., Attribution of Declining Western US Snowpack to Human Effects. Journal of Climate, 2008. 21(23): p. 6425-6444.
56. Hidalgo, H.G., et al., Detection and Attribution of Streamflow Timing Changes to Climate Change in the Western United States. Journal of Climate, 2009. 22(13): p. 3838-3855.
57. Pierce, D., Future changes in biological activity in the North Pacific due to anthropogenic forcing of the physical environment. Climatic Change, 2004. 62(1): p. 389-418.
58. Pierce, D., Beyond the Means: Validating Climate Models with Higher-Order Statistics}. Computing in Science and Engineering}. 6: p. 22-29.
59. Pierce, D.W., The Role of Sea Surface Temperatures in Interactions between ENSO and the North Pacific Oscillation. Journal of Climate, 2002. 15(11): p. 1295-1308.
60. Pierce, D., Distinguishing coupled oceanĖatmosphere interactions from background noise in the North Pacific. Progress in Oceanography, 2001. 49(1-4): p. 331-352.
61. Pierce, D., T. Barnett, and M. Latif, Connections between the Pacific Ocean Tropics and midlatitudes on decadal timescales. Journal of Climate, 2000. 13(6).
62. Pierce, D., The hybrid coupled model, version 3: technical notes. Scripps Institution of Oceanography Ref. Series, 1996: p. 66.