Bibliography - Yi Ming

1. Bollasina, M, and Yi Ming, in press: The general circulation model precipitation bias over the southwestern equatorial Indian Ocean and its implications for simulating the South Asian monsoon. Climate Dynamics. DOI:10.1007/s00382-012-1347-7. 5/12.
   [ Abstract ]

   Most of current general circulation models (GCMs) show a remarkable positive precipitation bias over the southwestern equatorial Indian Ocean (SWEIO), which can be thought of as a westward expansion of the simulated IO convergence zone toward the coast of Africa. The bias is common to both coupled and uncoupled models, suggesting that its origin does not stem from the way boundary conditions are specified. The spatio-temporal evolution of the precipitation and associated three-dimensional atmospheric circulation biases is comprehensively characterized by comparing the GFDL AM3 atmospheric model to observations. It is shown that the oceanic bias, which develops in spring and reduces during the monsoon season, is associated to a consistent precipitation and circulation anomalous pattern over the whole Indian region. In the vertical, the areas are linked by an anomalous Hadley-type meridional circulation, whose northern branch subsides over northeastern India significantly affecting the monsoon evolution (e.g., delaying its onset). This study makes the case that the precipitation bias over the SWEIO is forced by the model excess response to the local meridional sea surface temperature (SST) gradient through enhanced nearsurface meridional wind convergence. This is suggested by observational evidence and supported by AM3 sensitivity experiments. The latter show that relaxing the magnitude of the meridional SST gradient in the SWEIO can lead to a significant reduction of both local and large-scale precipitation and circulation biases. The ability of local anomalies over the SWEIO to force a large-scale remote response to the north is further supported by numerical experiments with the GFDL spectral dry dynamical core model. By imposing a realistic anomalous heating source over the SWEIO the model is able to reproduce the main dynamical features of the AM3 bias. These results indicate that improved GCM simulations of the South Asian summer monsoon could be achieved by reducing the springtime model bias over the SWEIO. Deficiencies in the atmospheric model, and in particular in the convective parameterization, are suggested to play a key role. Finally, the important mechanism controlling the simulated precipitation distribution over South Asia found here should be considered in the interpretation and attribution

2. Hill, S A., and Yi Ming, August 2012: Nonlinear climate response to regional brightening of tropical marine stratocumulus. Geophysical Research Letters, 39, L15707, DOI:10.1029/2012GL052064.
   [ Abstract ]

   To counteract global warming, there have been suggestions to increase the albedo of low-level marine clouds through the aerosol indirect effects by injecting them with sea salt. However, the full climate response to this geoengineering scheme is currently poorly understood. We simulate cloud seeding in a coupled mixed-layer ocean-atmosphere general circulation model in order to identify the specific physical mechanisms through which seeding could perturb the climate system's radiative balance, and cause temperature and precipitation changes. Seeding stratocumulus decks over three tropical maritime regions in the North Pacific, South Pacific and South Atlantic produces strong local reductions in solar absorption. Over half of the radiative cooling is due to direct scattering of solar radiation by the added sea salt aerosols, while the rest comes from enhancement of the local cloud albedo. The oceanic cooling due to the seeding over the southeastern equatorial Pacific induces a La Ni\~na-like response, with tropical precipitation changes resembling La Ni\~na anomalies and teleconnections occurring in the mid-latitude North Pacific and North America. Additionally, model runs in which only one of the three regions is seeded indicate nonlinearity in the climate response. We identify dynamical and thermodynamical constraints respectively on the temperature and hydrological cycle responses to cloud seeding, but the full response to such geoengineering remains poorly constrained.

3. Huang, X, H-W Chuang, A Dessler, X Chen, K Minschwaner, Yi Ming, and V Ramaswamy, in press: A radiative-convective equilibrium perspective of the weakening of tropical Walker circulation in response to global warming. Journal of Climate. DOI:10.1175/JCLI-D-12-00288.1. 9/12.
   [ Abstract ]

   Both observational analysis and GCM model simulations indicate that the tropical Walker circulation is becoming weaker and may continue to weaken as a consequence of climate change. Here we use a conceptual radiative-convective-equilibrium (RCE) framework to interpret the weakening of the Walker circulation as simulated by the GFDL coupled-GCM. Based on the modeled lapse rate and clear-sky cooling rate profiles, the RCE framework can directly compute the change of vertical velocity in the descending branch of the Walker circulation, which agrees with the counterpart simulated by the GFDL model. Our results show that the vertical structure of clear-sky radiative cooling rate (QR) will change in response to the increased water vapor as the globe warms. We explain why the change of QR is positive in the upper most part of the troposphere (<300 hPa) and is negative for the rest part of the troposphere. As a result, both the change of clear-sky cooling rate and the change of tropospheric lapse rate contribute to the weakening of circulation. The vertical velocity changes due to the two factors are comparable to each other from the top of planetary boundary layer to 600hPa. From 600hPa to 300hPa, lapse rate changes are the dominant cause of the weakening circulation. Above 300hPa, the change due to QR is opposite to the change due to lapse rate, which forces a slight increase in vertical velocity that is seen in the model simulation.

4. Ocko, I B., V Ramaswamy, Paul Ginoux, Yi Ming, and Larry W Horowitz, in press: Sensitivity of scattering and absorbing aerosol direct radiative forcing to physical climate factors. Journal of Geophysical Research. DOI:10.1029/2012JD018019. 9/12.
   [ Abstract ]

   The direct radiative forcing of the climate system includes effects due to scattering and absorbing aerosols. This study explores how important physical climate characteristics contribute to the magnitudes of the direct radiative forcings (DRF) from anthropogenic sulfate, black carbon, and organic carbon. For this purpose, we employ the GFDL CM2.1 global climate model, which has reasonable aerosol concentrations and reconstruction of 20th Century climate change. Sulfate and carbonaceous aerosols constitute the most important anthropogenic aerosol perturbations to the climate system, and provide striking contrasts between primarily scattering (sulfate and organic carbon) and primarily absorbing (black carbon) species. The quantitative roles of cloud coverage, surface albedo, and relative humidity in governing the sign and magnitude of all-sky top-of-atmosphere forcings are examined. Clouds reduce the global-mean sulfate TOA DRF by almost 50%, reduce the global-mean organic carbon TOA DRF by more than 30%, and increase the global-mean black carbon TOA DRF by almost 80%. Sulfate forcing is increased by over 50% as a result of hygroscopic growth, while high-albedo surfaces are found to have only a minor (less than 10%) impact on all global-mean forcings. Although the radiative forcing magnitudes are subject to uncertainties in the state of mixing of the aerosol species, it is clear that fundamental physical climate characteristics play a large role in governing aerosol direct radiative forcing magnitudes.

5. Persad, Geeta, Yi Ming, and V Ramaswamy, April 2012: Tropical tropospheric-only responses to absorbing aerosols. Journal of Climate, 25(7), DOI:10.1175/JCLI-D-11-00122.1.
   [ Abstract ]

   Absorbing aerosols affect the Earth's climate through direct radiative heating of the troposphere. We analyze the tropical tropospheric-only response to a globally uniform increase in black carbon, simulated with an atmospheric general circulation model, in order to gain insight into the interactions that determine the radiative flux perturbation. Over the convective regions, heating in the free troposphere hinders the vertical development of deep cumulus clouds, resulting in the detrainment of more cloudy air into the large-scale environment and stronger cloud reflection. A different mechanism operates over the subsidence regions, where heating near the boundary layer top causes a substantial reduction in low cloud amount thermodynamically by decreasing relative humidity and dynamically by lowering cloud top. These findings, which align well with previous general circulation model and large eddy simulation calculations for black carbon, provide physically based explanations for the main characteristics of the tropical tropospheric adjustment. The implications for quantifying the climate perturbation posed by absorbing aerosols are discussed.

6. Bollasina, M, Yi Ming, and V Ramaswamy, October 2011: Anthropogenic aerosols and the weakening of the South Asian summer monsoon. Science, 334(6055), DOI:10.1126/science.1204994.
   [ Abstract ]

   Observations show that South Asia underwent a widespread summertime drying during the second half of the 20th century, but it is unclear whether this trend was due to natural variations or human activities. We used a series of climate model experiments to investigate the South Asian monsoon response to natural and anthropogenic forcings. We find that the observed precipitation decrease can be attributed mainly to human-influenced aerosol emissions. The drying is a robust outcome of a slowdown of the tropical meridional overturning circulation, which compensates for the aerosol-induced energy imbalance between the Northern and Southern Hemispheres. These results provide compelling evidence of the prominent role of aerosols in shaping regional climate change over South Asia.

7. Chen, G, Yi Ming, N D Singer, and Jian Lu, February 2011: Testing the Clausius-Clapeyron constraint on the aerosol-induced changes in mean and extreme precipitation. Geophysical Research Letters, 38, L04807, DOI:10.1029/2010GL046435.
   [ Abstract ]

   The impacts of aerosol and greenhouse gas forcing of the 20th century on the climatological mean and extremes of precipitation are compared in an atmospheric GCM with improved parameterizations of aerosol direct and indirect effects. In spite of different forcing patterns, the thermodynamic effects of aerosol cooling and greenhouse gas warming on the zonally averaged precipitation have similar latitudinal patterns but opposite signs, plausibly due to the effects of temperature on atmospheric water vapor content and moisture flux. The fractional thermodynamic change, for both the moisture convergence in mid- and high latitudes and precipitation extremes at all latitudes, scales linearly with the abundance of atmospheric moisture at a rate of ∼5%/K, somewhat less than the expectation from the Clausius-Clapeyron relation.

8. Donner, Leo J., Bruce Wyman, Richard S Hemler, Larry W Horowitz, Yi Ming, Ming Zhao, J-C Golaz, Paul Ginoux, Shian-Jiann Lin, M Daniel Schwarzkopf, John Austin, G Alaka, W F Cooke, Thomas L Delworth, Stuart Freidenreich, C Tony Gordon, Stephen M Griffies, Isaac M Held, William J Hurlin, Stephen A Klein, Thomas R Knutson, Amy R Langenhorst, H C Lee, Yanluan Lin, B I Magi, Sergey Malyshev, P C D Milly, Vaishali Naik, Mary Jo Nath, R Pincus, Jeff J Ploshay, V Ramaswamy, Charles J Seman, Elena Shevliakova, Joseph J Sirutis, William F Stern, Ronald J Stouffer, R John Wilson, Michael Winton, Andrew T Wittenberg, and Fanrong Zeng, July 2011: The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component AM3 of the GFDL Global Coupled Model CM3. Journal of Climate, 24(13), DOI:10.1175/2011JCLI3955.1.
   [ Abstract ]

   The Geophysical Fluid Dynamics Laboratory (GFDL) has developed a coupled general circulation model (CM3) for atmosphere, oceans, land, and sea ice. The goal of CM3 is to address emerging issues in climate change, including aerosol-cloud interactions, chemistry-climate interactions, and coupling between the troposphere and stratosphere. The model is also designed to serve as the physical-system component of earth-system models and models for decadal prediction in the near-term future, for example, through improved simulations in tropical land precipitation relative to earlier-generation GFDL models. This paper describes the dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component (AM3) of this model. Relative to GFDL AM2, AM3 includes new treatments of deep and shallow cumulus convection, cloud-droplet activation by aerosols, sub-grid variability of stratiform vertical velocities for droplet activation, and atmospheric chemistry driven by emissions with advective, convective, and turbulent transport. AM3 employs a cubed-sphere implementation of a finite-volume dynamical core and is coupled to LM3, a new land model with eco-system dynamics and hydrology. Most basic circulation features in AM3 are simulated as realistically, or more so, than in AM2. In particular, dry biases have been reduced over South America. In coupled mode, the simulation of Arctic sea ice concentration has improved. AM3 aerosol optical depths, scattering properties, and surface clear-sky downward shortwave radiation are more realistic than in AM2. The simulation of marine stratocumulus decks and the intensity distributions of precipitation remain problematic, as in AM2. The last two decades of the 20th century warm in CM3 by .32°C relative to 1881-1920. The Climate Research Unit (CRU) and Goddard Institute for Space Studies analyses of observations show warming of .56°C and .52°C, respectively, over this period. CM3 includes anthropogenic cooling by aerosol cloud interactions, and its warming by late 20th century is somewhat less realistic than in CM2.1, which warmed .66°C but did not include aerosol cloud interactions. The improved simulation of the direct aerosol effect (apparent in surface clear-sky downward radiation) in CM3 evidently acts in concert with its simulation of cloud-aerosol interactions to limit greenhouse gas warming in a way that is consistent with observed global temperature changes.

9. Ghan, S, and Yi Ming, et al., October 2011: Droplet nucleation: Physically-based parameterizations and comparative evaluation. Journal of Advances in Modeling Earth Systems, 3, M10001, DOI:10.1029/2011MS000074.
   [ Abstract ]

   One of the greatest sources of uncertainty in simulations of climate and climate change is the influence of aerosols on the optical properties of clouds. The root of this influence is the droplet nucleation process, which involves the spontaneous growth of aerosol into cloud droplets at cloud edges, during the early stages of cloud formation, and in some cases within the interior of mature clouds. Numerical models of droplet nucleation represent much of the complexity of the process, but at a computational cost that limits their application to simulations of hours or days. Physically-based parameterizations of droplet nucleation are designed to quickly estimate the number nucleated as a function of the primary controlling parameters: the aerosol number size distribution, hygroscopicity and cooling rate. Here we compare and contrast the key assumptions used in developing each of the most popular parameterizations and compare their performances under a variety of conditions. We find that the more complex parameterizations perform well under a wider variety of nucleation conditions, but all parameterizations perform well under the most common conditions. We then discuss the various applications of the parameterizations to cloud-resolving, regional and global models to study aerosol effects on clouds at a wide range of spatial and temporal scales. We compare estimates of anthropogenic aerosol indirect effects using two different parameterizations applied to the same global climate model, and find that the estimates of indirect effects differ by only 10%. We conclude with a summary of the outstanding challenges remaining for further development and application.

10. Golaz, J-C, M Salzmann, Leo J Donner, Larry W Horowitz, Yi Ming, and Ming Zhao, July 2011: Sensitivity of the aerosol indirect effect to subgrid variability in the cloud parameterization of the GFDL Atmosphere General Circulation Model AM3. Journal of Climate, 24(13), DOI:10.1175/2010JCLI3945.1.
    [ Abstract ]

    The recently developed GFDL Atmospheric Model version 3 (AM3), an atmospheric general circulation model (GCM), incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. Since cloud drop activation depends on cloud-scale vertical velocities, which are not reproduced in present-day GCMs, additional assumptions on the subgrid variability are required to implement a local activation parameterization into a GCM. This paper describes the subgrid activation assumptions in AM3 and explores sensitivities by constructing alternate configurations. These alternate model configurations exhibit only small differences in their present-day climatology. However, the total anthropogenic radiative flux perturbation (RFP) between present-day and preindustrial conditions varies by ±50% from the reference, because of a large difference in the magnitude of the aerosol indirect effect. The spread in RFP does not originate directly from the subgrid assumptions but indirectly through the cloud retuning necessary to maintain a realistic radiation balance. In particular, the paper shows a linear correlation between the choice of autoconversion threshold radius and the RFP. Climate sensitivity changes only minimally between the reference and alternate configurations. If implemented in a fully coupled model, these alternate configurations would therefore likely produce substantially different warming from preindustrial to present day.

11. Ming, Yi, and V Ramaswamy, October 2011: A model investigation of aerosol-induced changes in tropical circulation. Journal of Climate, 24(19), DOI:10.1175/2011JCLI4108.1.
    [ Abstract ]

    We study how anthropogenic aerosols, alone or in conjunction with radiatively active gases, affect the tropical circulation with an atmosphere/mixed layer ocean general circulation model. Aerosol-induced cooling gives rise to a substantial increase in the overall strength of the tropical circulation, a robust outcome consistent with a thermodynamical scaling argument. Owing to the interhemispheric asymmetry in aerosol forcing, the zonal-mean and zonally asymmetrical components of the tropical circulation respond differently. The Hadley circulation weakens in the Northern Hemisphere, but strengthens in the Southern Hemisphere. The resulting northward cross-equatorial moist static energy flux compensates partly for the aerosol radiative cooling in the Northern Hemisphere. In contrast, the less restricted zonally asymmetrical circulation does not show sensitivity to the spatial structure of aerosols, and strengthens in both hemispheres. Our results also point to the possible role of aerosols in driving the observed reduction in the equatorial sea level pressure gradient. These circulation changes have profound implications for the hydrological cycle. We find that aerosols alone make the subtropical dry zones in both hemispheres wetter, as the local hydrological response is controlled thermodynamically by atmospheric moisture content. The deep tropical rainfall undergoes a dynamically induced southward shift, a robust pattern consistent with the adjustments in the zonal-mean circulation and in the meridional moist static energy transport. Less certain is the magnitude of the shift. The nonlinearity exhibited by the combined hydrological response to aerosols and radiatively active gases is dynamical in nature.

12. Ming, Yi, V Ramaswamy, and G Chen, December 2011: A model investigation of aerosol-induced changes in boreal winter extratropical circulation. Journal of Climate, 24(23), DOI:10.1175/2011JCLI4111.1.
    [ Abstract ]

    We examine the key characteristics of the boreal winter extratropical circulation changes in response to anthropogenic aerosols, simulated with a coupled atmosphere-slab ocean general circulation model. The zonal-mean response features a pronounced equatorward shift of the Northern Hemisphere subtropical jet owing to the mid-latitude aerosol cooling. The circulation changes also show strong zonal asymmetry. In particular, the cooling is more concentrated over the North Pacific than over the North Atlantic despite similar regional forcings. With the help of an idealized model, we demonstrate that the zonally asymmetrical response is linked tightly to the stationary Rossby waves excited by the anomalous diabatic heating over the tropical East Pacific. The altered wave pattern leads to a southeastward shift of the Aleutian low (and associated changes in winds and precipitation), while leaving the North Atlantic circulation relatively unchanged. Despite the rich circulation changes, the variations in the extratropical meridional latent heat transport are controlled strongly by the dependence of atmospheric moisture content on temperature. This suggests that one can project reliably the changes in extratropical zonal-mean precipitation solely from the global-mean temperature change, even without a good knowledge of the detailed circulation changes caused by aerosols. On the other hand, such knowledge is indispensable for understanding zonally asymmetrical (regional) precipitation changes.

13. Ming, Yi, March 2011: Aerosols In Encyclopedia of Climate and Weather, second edition, Oxford University Press, 34-38.
14. Ming, Yi, V Ramaswamy, and Geeta Persad, July 2010: Two opposing effects of absorbing aerosols on global-mean precipitation. Journal of Geophysical Research, 37, L13701, DOI:10.1029/2010GL042895.
    [ Abstract ]

    Absorbing aerosols affect global-mean precipitation primarily in two ways. They give rise to stronger shortwave atmospheric heating, which acts to suppress precipitation. Depending on the top-of-the-atmosphere radiative flux change, they can also warm up the surface with a tendency to increase precipitation. Here, we present a theoretical framework that takes into account both effects, and apply it to analyze the hydrological responses to increased black carbon burden simulated with a general circulation model. It is found that the damping effect of atmospheric heating can outweigh the enhancing effect of surface warming, resulting in a net decrease in precipitation. The implications for moist convection and general circulation are discussed.

15. Salzmann, M, Yi Ming, J-C Golaz, Paul Ginoux, H Morrison, A Gettelman, M Krämer, and Leo J Donner, August 2010: Two-moment bulk stratiform cloud microphysics in the GFDL AM3 GCM: description, evaluation, and sensitivity tests. Atmospheric Chemistry and Physics, 10(16), DOI:10.5194/acp-10-8037-2010.
    [ Abstract ]

    A new stratiform cloud scheme including a two-moment bulk microphysics module, a cloud cover parameterization allowing ice supersaturation, and an ice nucleation parameterization has been implemented into the recently developed GFDL AM3 general circulation model (GCM) as part of an effort to treat aerosol-cloud-radiation interactions more realistically. Unlike the original scheme, the new scheme facilitates the study of cloud-ice-aerosol interactions via influences of dust and sulfate on ice nucleation. While liquid and cloud ice water path associated with stratiform clouds are similar for the new and the original scheme, column integrated droplet numbers and global frequency distributions (PDFs) of droplet effective radii differ significantly. This difference is in part due to a difference in the implementation of the Wegener-Bergeron-Findeisen (WBF) mechanism, which leads to a larger contribution from super-cooled droplets in the original scheme. Clouds are more likely to be either completely glaciated or liquid due to the WBF mechanism in the new scheme. Super-saturations over ice simulated with the new scheme are in qualitative agreement with observations, and PDFs of ice numbers and effective radii appear reasonable in the light of observations. Especially, the temperature dependence of ice numbers qualitatively agrees with in-situ observations. The global average long-wave cloud forcing decreases in comparison to the original scheme as expected when super-saturation over ice is allowed. Anthropogenic aerosols lead to a larger decrease in short-wave absorption (SWABS) in the new model setup, but outgoing long-wave radiation (OLR) decreases as well, so that the net effect of including anthropogenic aerosols on the net radiation at the top of the atmosphere (netradTOA = SWABS-OLR) is of similar magnitude for the new and the original scheme.

16. Shindell, D, M Schulz, Yi Ming, T Takemura, G Faluvegi, and V Ramaswamy, October 2010: Spatial scales of climate response to inhomogeneous radiative forcing. Journal of Geophysical Research, 115, D19110, DOI:10.1029/2010JD014108.
    [ Abstract ]

    The distances over which localized radiative forcing influences surface temperature have not been well characterized. We present a general methodology to analyze the spatial scales of the forcing/response relationship, and apply it to simulations of historical aerosol forcing and response in four climate models. We find that the surface temperature response is not strongly sensitive to the longitude of forcing, but is fairly sensitive to latitude. Surface temperature responses in the Arctic and the Southern Hemisphere extratropics, where forcing was small, show little relationship to local forcing. Restricting the analysis to 30S-60N, where nearly all the forcing was applied, shows that forcing strongly influences response out to ~4500 km away examining all directions. The meridional length of influence is somewhat shorter (~3500 km or 30 degrees), while it extends out to at least 12,000 km in the zonal direction. Substantial divergences between the models are seen over the oceans, whose physical representations differ greatly among the models. Length scales are quite consistent over 30S-60N land areas, however, despite differences in both the forcing applied and the physics of the models themselves. The results suggest that better understanding of regionally inhomogeneous radiative forcing would lead to improved projections of regional climate change over land areas. They also provide quantitative estimates of the spatial extent of the climate impacts of pollutants, which can extend thousands of kilometers beyond polluted areas, especially in the zonal direction.

17. Magi, B I., Paul Ginoux, Yi Ming, and V Ramaswamy, July 2009: Evaluation of tropical and extratropical Southern Hemisphere African aerosol properties simulated by a climate model. Journal of Geophysical Research, D14204, DOI:10.1029/2008JD011128.
    [ Abstract ]

    We compare aerosol optical depth (AOD) and single scattering albedo (SSA) simulated by updated configurations of a version of the atmospheric model (AM2) component of the NOAA Geophysical Fluid Dynamics Laboratory general circulation model over Southern Hemisphere Africa with AOD and SSA derived from research aircraft measurements and NASA Aerosol Robotic Network (AERONET) stations and with regional AOD from the NASA Moderate Resolution Imaging Spectroradiometer satellite. The results of the comparisons suggest that AM2 AOD is biased low by 30–40% in the tropics and 0–20% in the extratropics, while AM2 SSA is biased high by 4–8%. The AM2 SSA bias is higher during the biomass burning season, and the monthly variations in AM2 SSA are poorly correlated with AERONET. On the basis of a comparison of aerosol mass in the models with measurements from southern Africa, and a detailed analysis of aerosol treatment in AM2, we suggest that the low bias in AOD and high bias in SSA are related to an underestimate of carbonaceous aerosol emissions in the biomass burning inventories used by AM2. Increases in organic matter and black carbon emissions by factors of 1.6 and 3.8 over southern Africa improve the biases in AOD and especially SSA. We estimate that the AM2 biases in AOD and SSA imply that the magnitude of annual top of the atmosphere radiative forcing in clear-sky conditions over southern Africa is overestimated (too negative) by ∼8% while surface radiative forcing is underestimated (not negative enough) by ∼20%.

18. Ming, Yi, and V Ramaswamy, March 2009: Nonlinear climate and hydrological responses to aerosol effects. Journal of Climate, 22(6), DOI:10.1175/2008JCLI2362.1.
    [ Abstract ]

    The equilibrium temperature and hydrological responses to the total aerosol effects (i.e., direct, semidirect, and indirect effects) are studied using a modified version of the Geophysical Fluid Dynamics Laboratory atmosphere general circulation model (AM2.1) coupled to a mixed layer ocean model. The treatment of aerosol–liquid cloud interactions and associated indirect effects is based upon a prognostic scheme of cloud droplet number concentration, with an explicit representation of cloud condensation nuclei activation involving sulfate, organic carbon, and sea salt aerosols. Increasing aerosols from preindustrial (1860) to presentday (1990) levels leads to a decrease of 1.9 K in the global annual mean surface temperature. The cooling is relatively strong over the Northern Hemisphere midlatitude land owing to the high aerosol burden there, while being amplified at high latitudes. When being subject to aerosols and radiatively active gases (i.e., wellmixed greenhouse gases and ozone) simultaneously, the model climate behaves nonlinearly; the simulated increase in surface temperature (0.55 K) is considerably less than the arithmetic sum of separate aerosol and gas effects (0.86 K). The thermal responses are accompanied by the nonlinear changes in cloud fields, which are amplified owing to the surface albedo feedback at high latitudes. The two effects completely offset each other in the Northern Hemisphere, while gas effect is dominant in the Southern Hemisphere. Both factors are crucial in shaping the regional responses. Interhemispheric asymmetry in aerosol-induced cooling yields a southward shift of the intertropical convergence zone, thus giving rise to a significant reduction in precipitation north of the equator, and an increase to the south. The simulations show that the change of precipitation in response to the simultaneous increases in aerosols and gases not only largely follows the same pattern as that for aerosols alone, but that it is also substantially strengthened in terms of magnitude south of 10°N. This is quite different from the damping expected from adding up individual responses, and further indicates the nonlinearity in the model's hydrological response.

19. Quaas, J, Yi Ming, Leo J Donner, and Paul Ginoux, et al., November 2009: Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data. Atmospheric Chemistry and Physics, 9(22), DOI:10.5194/acp-9-8697-2009.
    [ Abstract ]

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τ_a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (N_d) compares relatively well to the satellite data at least over the ocean. The relationship between τ_a and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f_cld) and τ_a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong f_cld–τ_a relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τ_a and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR–τ_a relationship show a strong positive correlation between τ_a and f_cld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τ_a, and parameterisation assumptions such as a lower bound on N_d. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm⁻². In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τ_a and satellite-retrieved Nd–τ_a regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2 Wm⁻² and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm⁻², with a total estimate of −1.2±0.4 Wm⁻².

20. Lee, S S., Leo J Donner, V T J Phillips, and Yi Ming, 2008: The dependence of aerosol effects on clouds and precipitation on cloud-system organization, shear and stability. Journal of Geophysical Research, 113, D16202, DOI:10.1029/2007JD009224.
    [ Abstract ]

    Precipitation suppression due to an increase of aerosol number concentration in stratiform cloud is well-known. It is not certain whether the suppression applies for deep convection. Recent studies have suggested increasing precipitation from deep convection with increasing aerosols under some, but not all, conditions. Increasing precipitation with increasing aerosols can result from strong interactions in deep convection between dynamics and microphysics. High cloud liquid, due to delayed autoconversion, provides more evaporation, leading to more active downdrafts, convergence fields, condensation, collection of cloud liquid by precipitable hydrometeors, and precipitation. Evaporation of cloud liquid is a primary determinant of the intensity of the interactions. It is partly controlled by wind shear modulating the entrainment of dry air into clouds and transport of cloud liquid into unsaturated areas. Downdraft-induced convergence, crucial to the interaction, is weak for shallow clouds, generally associated with low convective available potential energy (CAPE). Aerosol effects on cloud and precipitation can vary with CAPE and wind shear. Pairs of idealized numerical experiments for high and low aerosol cases were run for five different environmental conditions to investigate the dependence of aerosol effect on stability and wind shear. In the environment of high CAPE and strong wind shear, cumulonimbus- and cumulus-type clouds were dominant. Transport of cloud liquid to unsaturated areas was larger at high aerosol, leading to stronger downdrafts. Because of the large vertical extent of those clouds, strong downdrafts and convergence developed for strong interactions between dynamics and microphysics. These led to larger precipitation at high aerosol. Detrainment of cloud liquid and associated evaporation were less with lower CAPE and wind shear, where dynamically weaker clouds dominated. Transport of cloud liquid to unsaturated areas was not as active as in the environment of high CAPE and strong shear. Also, evaporatively driven differences in downdrafts at their level of initial descent were not magnified in clouds with shallow depth as much as in deep convective clouds as they accelerated to the surface over shorter distances. Hence the interaction between dynamics and microphysics was reduced, leading to precipitation suppression at high aerosol. These results demonstrate that increasing aerosol can either decrease or increase precipitation for an imposed large-scale environment supporting cloud development. The implications for larger-scale aspects of the hydrological cycle will require further study with larger-domain models and cumulus parameterizations with advanced microphysics.

21. Lee, S S., Leo J Donner, V T J Phillips, and Yi Ming, 2008: Examination of aerosol effects on precipitation in deep convective clouds during the 1997 ARM summer experiment. Quarterly Journal of the Royal Meteorological Society, 134(634), DOI:10.1002/qj.287.
    [ Abstract ]

    It has been generally accepted that increasing aerosols suppress precipitation. The aerosol-induced precipitation suppression was suggested by the study of shallow stratiform clouds. Recent studies of convective clouds showed increasing aerosols could increase precipitation. Those studies showed that intense feedbacks between aerosols and cloud dynamics led to increased precipitation in some cases of convective clouds. This study expanded those studies by analyzing detailed microphysical and dynamical modifications by aerosols leading to increased precipitation. This study focused on three observed cases of mesoscale cloud ensemble (MCE) driven by deep convective clouds, since MCE accounts for a large proportion of the Earth's precipitation and the study of aerosol effects on MCE is at its incipient stage. Those MCEs were observed during the 1997 Atmospheric Radiation Measurement (ARM) summer experiment. Two numerical experiments were performed for each of the MCEs to simulate aerosol effects on deep convection. The first was with high aerosol number concentration, and the second was with low concentration. The results showed an increased precipitation at high aerosol, due to stronger, more numerous updraughts, initiated by stronger convergence lines at the surface in convective regions of the MCE. The stronger convergence lines were triggered by increased evaporation of cloud liquid in the high-aerosol case, made possible by higher values of cloud liquid necessary for autoconversion. The generality of these results requires further investigation. However, they demonstrate that the response of precipitation to increased aerosols in deep convection can be different from that in shallow cloud systems, at least for the cases studied here.

22. Ming, Yi, V Ramaswamy, Leo J Donner, V T J Phillips, Stephen A Klein, Paul Ginoux, and Larry W Horowitz, February 2007: Modeling the interactions between aerosols and liquid water clouds with a self-consistent cloud scheme in a general circulation model. Journal of the Atmospheric Sciences, 64(4), DOI:10.1175/JAS3874.1.
    [ Abstract ]

    To model aerosol-cloud interactions in general circulation models (GCMs), a prognostic cloud scheme of cloud liquid water and amount is expanded to include droplet number concentration (N_d) in a way that allows them to be calculated using the same large-scale and convective updraft velocity field. In the scheme, the evolution of droplets fully interacts with the model meteorology. An explicit treatment of cloud condensation nuclei (CCN) activation enables the scheme to take into account the contributions to N_d of multiple aerosol species (i.e., sulfate, organic, and sea-salt aerosols) and to consider kinetic limitations of the activation process. An implementation of the prognostic scheme in the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 GCM yields a vertical distribution of N_d with a characteristic maximum in the lower troposphere; this feature differs from the profile that would be obtained if N_dis diagnosed from the sulfate mass concentration based on an often-used empirical relationship. Prognosticated N_d exhibits large variations with respect to the sulfate mass concentration. The mean values are generally consistent with the empirical relationship over ocean, but show negative biases over the Northern Hemisphere midlatitude land, perhaps owing to the neglect of subgrid variations of large-scale ascents and inadequate convective sources. The prognostic scheme leads to a substantial improvement in the agreement of model-predicted present-day liquid water path (LWP) and cloud forcing with satellite measurements compared to using the empirical relationship. The simulations with preindustrial and present-day aerosols show that the combined first and second indirect effects of anthropogenic sulfate and organic aerosols give rise to a steady-state global annual mean flux change of -1.8 W m^-2, consisting of -2.0 W m^-2 in shortwave and 0.2 W m^-2 in longwave. The ratios of the flux changes in the Northern Hemisphere (NH) to that in Southern Hemisphere (SH) and of the flux changes over ocean to that over land are 2.9 and 0.73, respectively. These estimates are consistent with the averages of values from previous studies stated in a recent review. The model response to higher Nd alters the cloud field; LWP and total cloud amount increase by 19% and 0.6%, respectively. Largely owing to high sulfate concentrations from fossil fuel burning, the NH midlatitude land and oceans experience strong radiative cooling. So does the tropical land, which is dominated by biomass burning-derived organic aerosol. The computed annual, zonal-mean flux changes are determined to be statistically significant, exceeding the model's natural variations in the NH low and midlatitudes and in the SH low latitudes. This study reaffirms the major role of sulfate in providing CCN for cloud formation.

23. Ming, Yi, V Ramaswamy, Leo J Donner, and V T J Phillips, 2006: A new parameterization of cloud droplet activation applicable to general circulation models. Journal of the Atmospheric Sciences, 63(4), DOI:10.1175/JAS3686.1.
    [ Abstract ]

    A new parameterization is proposed to link the droplet number concentration to the size distribution and chemical composition of aerosol and updraft velocity. Except for an empirical assumption of droplet growth, the parameterization is formulated almost entirely on first principles to allow for satisfactory performance under a variety of conditions. For a series of updraft velocity ranging from 0.03 to 10.0 m s−1, the droplet number concentrations predicted with the parameterization are in good agreement with the detailed parcel model simulations with an average error of −4 ± 26% (one standard deviation). The accuracy is comparable to or better than some existing parameterizations. The parameterization is able to account for the effects of droplet surface tension and mass accommodation coefficient on activation without adjusting the empirical parameter. These desirable attributes make the parameterization suitable for being used in the prognostic determination of the cloud droplet number concentration in general circulation models (GCMs).

24. Ming, Yi, V Ramaswamy, Paul Ginoux, and Larry W Horowitz, 2005: Direct radiative forcing of anthropogenic organic aerosol. Journal of Geophysical Research, 110, D20208, DOI:10.1029/2004JD005573.
    [ Abstract ]

    This study simulates the direct radiative forcing of organic aerosol using the GFDL AM2 GCM. The aerosol climatology is provided by the MOZART chemical transport model (CTM). The approach to calculating aerosol optical properties explicitly considers relative humidity–dependent hygroscopic growth by employing a functional group–based thermodynamic model, and makes use of the size distribution derived from AERONET measurements. The preindustrial (PI) and present-day (PD) global burdens of organic carbon are 0.17 and 1.36 Tg OC, respectively. The annual global mean total-sky and clear-sky top-of-the atmosphere (TOA) forcings (PI to PD) are estimated as −0.34 and −0.71 W m⁻², respectively. Geographically the radiative cooling largely lies over the source regions, namely part of South America, Central Africa, Europe and South and East Asia. The annual global mean total-sky and clear-sky surface forcings are −0.63 and −0.98 W m⁻², respectively. A series of sensitivity analyses shows that the treatments of hygroscopic growth and optical properties of organic aerosol are intertwined in the determination of the global organic aerosol forcing. For example, complete deprivation of water uptake by hydrophilic organic particles reduces the standard (total-sky) and clear-sky TOA forcing estimates by 18% and 20%, respectively, while the uptake by a highly soluble organic compound (malonic acid) enhances them by 18% and 32%, respectively. Treating particles as non-absorbing enhances aerosol reflection and increases the total-sky and clear-sky TOA forcing by 47% and 18%, respectively, while neglecting the scattering brought about by the water associated with particles reduces them by 24% and 7%, respectively.

25. Ming, Yi, V Ramaswamy, Paul Ginoux, Larry W Horowitz, and L M Russell, 2005: Geophysical Fluid Dynamics Laboratory general circulation model investigation of the indirect radiative effects of anthropogenic sulfate aerosol. Journal of Geophysical Research, 110, D22206, DOI:10.1029/2005JD006161.
    [ Abstract ]

    The Geophysical Fluid Dynamics Laboratory (GFDL) atmosphere general circulation model, with its new cloud scheme, is employed to study the indirect radiative effect of anthropogenic sulfate aerosol during the industrial period. The preindustrial and present-day monthly mean aerosol climatologies are generated from running the Model for Ozone And Related chemical Tracers (MOZART) chemistry-transport model. The respective global annual mean sulfate burdens are 0.22 and 0.81 Tg S. Cloud droplet number concentrations are related to sulfate mass concentrations using an empirical relationship (Boucher and Lohmann, 1995). A distinction is made between "forcing" and flux change at the top of the atmosphere in this study. The simulations, performed with prescribed sea surface temperature, show that the first indirect "forcing" ("Twomey" effect) amounts to an annual mean of -1.5 W m^-2, concentrated largely over the oceans in the Northern Hemisphere (NH). The annual mean flux change owing to the response of the model to the first indirect effect is -1.4 W m^-2, similar to the annual mean forcing. However, the model's response causes a rearrangement of cloud distribution as well as changes in longwave flux (smaller than solar flux changes). There is thus a differing geographical nature of the radiation field than for the forcing even though the global means are similar. The second indirect effect, which is necessarily an estimate made in terms of the model's response, amounts to -0.9 W m^-2, but the statistical significance of the simulated geographical distribution of this effect is relatively low owing to the model's natural variability. Both the first and second effects are approximately linearly additive, giving rise to a combined annual mean flux change of -2.3 W m^-2, with the NH responsible for 77% of the total flux change. Statistically significant model responses are obtained for the zonal mean total indirect effect in the entire NH and in the Southern Hemisphere low latitudes and midlatitudes (north of 45°S). The area of significance extends more than for the first and second effects considered separately. A comparison with a number of previous studies based on the same sulfate-droplet relationship shows that, after distinguishing between forcing and flux change, the global mean change in watts per square meter for the total effect computed in this study is comparable to existing studies in spite of the differences in cloud schemes.

26. Ming, Yi, L M Russell, and D F Bradford, 2005: Health and climate policy impacts on sulfur emission control. Reviews of Geophysics, 43, RG4001, DOI:10.1029/2004RG000167.
    [ Abstract ]

    Sulfate aerosol from burning fossil fuels not only has strong cooling effects on the Earth's climate but also imposes substantial costs on human health. To assess the impact of addressing air pollution on climate policy, we incorporate both the climate and health effects of sulfate aerosol into an integrated-assessment model of fossil fuel emission control. Our simulations show that a policy that adjusts fossil fuel and sulfur emissions to address both warming and health simultaneously will support more stringent fossil fuel and sulfur controls. The combination of both climate and health objectives leads to an acceleration of global warming in the 21st century as a result of the short-term climate response to the decreased cooling from the immediate removal of short-lived sulfate aerosol. In the long term (more than 100 years), reducing sulfate aerosol emissions requires that we decrease fossil fuel combustion in general, thereby removing some of the coemitted carbon emissions and leading to a reduction in global warming.

27. Ming, Yi, and L M Russell, 2004: Organic aerosol effects on fog droplet spectra. Journal of Geophysical Research, 109, D10206, DOI:10.1029/2003JD004427.
    [ Abstract ]

    Organic aerosol alters cloud and fog properties through surface tension and solubility effects. This study characterizes the role of organic compounds in affecting fog droplet number concentration by initializing and comparing detailed particle microphysical simulations with two field campaigns in the Po Valley. The size distribution and chemical composition of aerosol were based on the measurements made in the Po Valley Fog Experiments in 1989 and 1998–1999. Two types of aerosol with different hygroscopicity were considered: the less hygroscopic particles, composed mainly of organic compounds, and the more hygroscopic particles, composed mainly of inorganic salts. The organic fraction of aerosol mass was explicitly modeled as a mixture of seven soluble compounds [Fuzzi et al., 2001] by employing a functional group-based thermodynamic model [Ming and Russell, 2002]. Condensable gases in the vapor phase included nitric acid, sulfuric acid, and ammonia. The maximum supersaturation in the simulation is 0.030% and is comparable to the calculation by Noone et al. [1992] inferred from measured residual particle fractions. The minimum activation diameters of the less and more hygroscopic particles are 0.49 μm and 0.40 μm, respectively. The predicted residual particle fractions are in agreement with measurements. The organic components of aerosol account for 34% of the droplet residual particle mass and change the average droplet number concentration by −10–6%, depending on the lowering of droplet surface tension and the interactions among dissolving ions. The hygroscopic growth of particles due to the presence of water-soluble organic compounds enhances the condensation of nitric acid and ammonia due to the increased surface area, resulting in a 9% increase in the average droplet number concentration. Assuming ideal behavior of aqueous solutions of water-soluble organic compounds overestimates the hygroscopic growth of particles and increases droplet numbers by 6%. The results are sensitive to microphysical processes such as condensation of soluble gases, which increases the average droplet number concentration by 26%. Wet deposition plays an important role in controlling liquid water content in this shallow fog.

28. Ming, Yi, et al., 2004: Free energy perturbation study of water dimer dissociation kinetics. Journal of Chemical Physics, 121, 773-777.
29. Ming, Yi, and L M Russell, 2002: Thermodynamic equilibrium of aqueous solutions of organic-electrolyte mixtures in aerosol particles. AIChE Journal, 48, 1331.
30. Russell, L M., and Yi Ming, 2002: Deliquescence of small particles. Journal of Chemical Physics, 116, 311-321.
31. Ming, Yi, and L M Russell, 2001: Predicted hygroscopic growth of sea salt aerosol. Journal of Geophysical Research, 106(D22), 28,259-28,274.
    [ Abstract ]

    Organic species in sea salt particles can significantly reduce hygroscopic growth in subsaturated conditions, an important uncertainty in the radiative effect of aerosol particles on the atmosphere. This hygroscopic behavior is predicted with a numerical model of the the organic‐water, electrolyte‐water, and organicelectrolyte interactions in complex mixtures of organic species and inorganic ions. The results show a 15% decrease in hygroscopic growth above 75% relative humidity for particles that include as little as 30% organic mass. Organic compositions of 50% organic mass reduce hygroscopic growth by 25%. This prediction relies on particle chemical composition estimated from measurements of insoluble organic species in marine‐derived particles and of soluble organic species measured in seawater. Twenty insoluble and four soluble organic species are used to represent the behavior of sea salt organic composition. The hygroscopic growth is strongly sensitive to the organic fraction that is soluble or slightly soluble, although variations among different soluble or insoluble species are small above the sodium chloride deliquescence point. Interactions between organic and electrolyte species depend primarily on the “salting out” behavior of NaCl with alkanes, carboxylic acids, and alcohols, although interactions with other inorganic ions in sea salt were estimated to cause small changes in the hygroscopic growth. The predicted growth factors for sea salt with < 30% organic species are consistent with growth factors measured for ambient marine‐derived particles by another group [Berg et al., 1998; Swietlicki et al, 2000; Zhou et al, 2001]. This coincidence suggests that the less‐hygroscopic particles could indicate the presence of marine organic compounds, although multiple combinations of inorganic and anthropogenic organic species would also satisfy the measured behavior.

32. Prenni, A J., P J Demott, S M Kreidenweiss, D E Sherman, L M Russell, and Yi Ming, 2001: The effects of low molecular weight dicarboxylic acids on cloud formation. Journal of Physical Chemistry A, 105, 11240-11248.

Direct link to page: http://www.gfdl.noaa.gov/bibliography/results.php?author=1217