Post on 21-Dec-2015
Motivation• Sensitivity of Precipitation to Aerosol
Concentration. (Based partly on 2 d results).• Theory: Precipitation occurring in a “maritime”
airmass should develop sooner and precipitate on the upwind slope. Precipitation in continental aerosols should be displaced downwind (if it develops at all).
• Cloud tops in continental runs should be cooler, as slower diffusional growth is favored over growth processes occurring through collisions.
Set-Up
• First set of simulations was done with liquid only microphysical processes.
• Grid spacing was 3 km.
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Figure 1
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Figure 2
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Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7
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Figure 8
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Figure 9
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Figure 10
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Figure 11
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Figure 12
Perhaps
• We need a source of aerosols to replace those scavenged.
• Simulation redone with constant (source of), continental aerosols.
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Scavenging of aerosols leads to lower clouds with warmer cloud top temperatures (but dynamics more important).
Figure 13
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Figure 14
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Figure 15
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Figure 16
Model Restarted
• Simulations with maritime and continental aerosols, starting from the same initial conditions at 16 GMT
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Ice processes
Figure 17
Some enhancement of precip.
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Summary Part II:
• Initially, deep clouds over a mountainous terrain in a maritime environment produce more rain than clouds in a continental environment.
• Over time, the clouds in a continental environment produce more rain.
Explanation?
• Scavenging of large aerosols allows continental air mass to evolve towards a maritime condition.
• Differences in cloud height support this. • Yet, even with constant aerosols in a
continental environment, precipitation from clouds in this environment is more than in the maritime/continental simulation
Shallow clouds (should) conform to theory?
• Differences in precipitation from shallow clouds developed much the same way as deep clouds (but effect was proportionally more important).
• Cloud top heights were cooler in maritime simulation than in continental simulation?
• Including ice processes does not change the result.
• “Real world” is more complex than prevailing theory and results from 2d simulations.
Ongoing and Future Work
• Coupling of SBM in WRF (NSF SGER)
• Further investigation of aerosol effects on precipitation (PIER, Israeli Science Foundation, ANTISTORM)
• Development of hybrid SBM bulk microphysical model (?)