Sensitivity of the total anthropogenic aerosol effect to the treatment of rain in a global climate model

Abstract. Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

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Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-8917-2009 ◽

2009 ◽

Vol 9 (22) ◽

pp. 8917-8934 ◽

Cited By ~ 119

Author(s):

U. Lohmann ◽

C. Hoose

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Mixed Phase ◽

Anthropogenic Aerosols ◽

Anthropogenic Aerosol ◽

Activation Effect ◽

Aerosol Effect ◽

Sensitivity Studies ◽

Mixed Phase Clouds

Abstract. Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

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Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3425-2007 ◽

2007 ◽

Vol 7 (13) ◽

pp. 3425-3446 ◽

Cited By ~ 307

Author(s):

U. Lohmann ◽

P. Stier ◽

C. Hoose ◽

S. Ferrachat ◽

S. Kloster ◽

...

Keyword(s):

Indirect Effects ◽

Cloud Cover ◽

Emission Inventory ◽

Climate Model ◽

Global Climate Model ◽

Cloud Droplet ◽

Cloud Microphysics ◽

Anthropogenic Aerosol ◽

Aerosol Effect ◽

Aerosol Emission

Abstract. The double-moment cloud microphysics scheme from ECHAM4 that predicts both the mass mixing ratios and number concentrations of cloud droplets and ice crystals has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass, number concentrations and mixing state. The simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and −35° C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to −1.9 W m−2 in ECHAM5, when a relative humidity dependent cloud cover scheme and aerosol emissions representative for the years 1750 and 2000 from the AeroCom emission inventory are used. The contribution of the cloud albedo effect amounts to −0.7 W m−2. The total anthropogenic aerosol effect is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed because the cloud lifetime effect increases.

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Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter – a model study with ECHAM6-HAM

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6243-2017 ◽

2017 ◽

Vol 17 (10) ◽

pp. 6243-6255 ◽

Cited By ~ 7

Author(s):

Hanna Joos ◽

Erica Madonna ◽

Kasja Witlox ◽

Sylvaine Ferrachat ◽

Heini Wernli ◽

...

Keyword(s):

North Pacific ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Aerosol Particles ◽

Conveyor Belt ◽

Radiation Balance ◽

Anthropogenic Aerosol ◽

Conveyor Belts ◽

Warm Conveyor Belts

Abstract. While there is a clear impact of aerosol particles on the radiation balance, whether and how aerosol particles influence precipitation is controversial. Here we use the ECHAM6-HAM global climate model coupled to an aerosol module to analyse whether an impact of anthropogenic aerosol particles on the timing and amount of precipitation can be detected in North Pacific warm conveyor belts. Warm conveyor belts are the strongest precipitation-producing airstreams in extratropical cyclones and are identified here with a Lagrangian technique, i.e. by objectively identifying the most strongly ascending trajectories in North Pacific cyclones. These conveyor belts have been identified separately in 10-year ECHAM6-HAM simulations with present-day and pre-industrial aerosol conditions. Then, the evolution of aerosols and cloud properties has been analysed in detail along the identified warm conveyor belt trajectories. The results show that, under present-day conditions, some warm conveyor belt trajectories are strongly polluted (i.e. high concentrations of black carbon and sulfur dioxide) due to horizontal transport from eastern Asia to the oceanic region where warm conveyor belts start their ascent. In these polluted trajectories a weak delay and reduction of precipitation formation occurs compared to clean warm conveyor belt trajectories. However, all warm conveyor belts consist of both polluted and clean trajectories at the time they start their ascent, and the typically more abundant clean trajectories strongly reduce the aerosol impact from the polluted trajectories. The main conclusion then is that the overall amount of precipitation is comparable in pre-industrial conditions, when all warm conveyor belt trajectories are clean, and in present-day conditions, when warm conveyor belts consist of a mixture of clean and polluted trajectories.

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High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

10.2514/6.1996-1100 ◽

1996 ◽

Cited By ~ 1

Author(s):

Larry Bergman ◽

J. Gary ◽

Burt Edelson ◽

Neil Helm ◽

Judith Cohen ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Bit Rate ◽

Global Science ◽

High Bit Rate

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DEVELOPMENT OF BIAS CORRECTION METHOD FOR TROPICAL CYCLONES IN GLOBAL CLIMATE MODEL AND FUTURE CHANGE PROJECTION OF STORM SURGE USING AMR MODEL

Journal of Japan Society of Civil Engineers Ser B2 (Coastal Engineering) ◽

10.2208/kaigan.74.i_607 ◽

2018 ◽

Vol 74 (2) ◽

pp. I_607-I_612 ◽

Cited By ~ 1

Author(s):

Yosuke YAMAMOTO ◽

Nobuthito MORI ◽

Marc KJERLAND

Keyword(s):

Tropical Cyclones ◽

Storm Surge ◽

Bias Correction ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Correction Method ◽

Future Change ◽

Bias Correction Method

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A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-6527-2010 ◽

2010 ◽

Vol 10 (14) ◽

pp. 6527-6536 ◽

Cited By ~ 16

Author(s):

M. A. Brunke ◽

S. P. de Szoeke ◽

P. Zuidema ◽

X. Zeng

Keyword(s):

Diurnal Cycle ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Cloud Fraction ◽

Cloud Base ◽

Liquid Water Path ◽

Cloud Properties ◽

Southeast Pacific ◽

Cloud Thickness

Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003–2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

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