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Aerosols, Clouds, Atmospheres > Aerosol Microphysics 2 > Flashcards

Aerosol Microphysics 2 Flashcards

1
Q

what is the sectional approach in GCMs?

A

-the size distribution is descretised into sections and the particles properties are assumed to be constant over particle size sections

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2
Q

what is the modal approach in GCMs?

A

the size distribution is approximated by several log-normal modes and particle properties are assumed to be uniform in each mode

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3
Q

what is more costly and complex? Sectional or modal?

A

sectional is most costly and complex

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4
Q

what is the GDE?

A

mathematical formulation of all the processes which act to change the atmospheric particle size distribution

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5
Q

is there a general solution to the GDE?

A

no it must be solved numerically

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6
Q

how does nucleation affect particle number, particle mass, and particle SA

A

increases particle number, increases particle mass, increases particle SA

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7
Q

how does coagulation affect particle number and particle mass and particle SA

A

decreases particle number, no effect on particle mass, decrease in particle SA

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8
Q

how does condensation affect particle number and particle mass and particle SA

A

no effect on particle number, increase in particle SA, increase in particle mass

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9
Q

how does deposition affect particle number and particle mass and particle SA

A

decreases particle number, SA, and mass

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10
Q

what is time splitting and operator splitting?

A

-they’re discretisation techniques
-assume independence of the evolutions of the different processes during a time delta t
-they consecutively apply suitable methods to each physical processing during each time delta t

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11
Q

what do bulk aerosol models measure/track?

A

-only track total mass of aerosol components
-assume typical size distributions

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12
Q

what are some benefits of bulk aerosol models?

A

-computationally most efficient
-ok to use for air quality models that only require PM10 or PM25

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13
Q

what are some drawbacks for bulk aerosol models?

A

-cant be used if they require aerosol number concs e.g. climate studies
-cant be used for modelling that requires accurate size dependent aerosol processes e.g. growth

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14
Q

In sectional models, for m chemical compounds, how many equations must be solved?

A

n x m

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15
Q

what does the accuracy of sectional models depend on?

A

the number of sections

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16
Q

what can we assume about the particle size distribution within a size bin?

A

particle size distribution is continuous and monodisperse

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17
Q

name 4 sectional model algorithms

A

-fixed size sections
-modified fixed method: hybrid approach
-moving size sections
-moving centre method

18
Q

what are 4 transformation processes?

A

-nucleation
-coagulation
-condensation
-deposition

19
Q

what do sectional schemes represent well?

A

complex aerosol dynamics

20
Q

what is the most commonly used approach in GCMs?

A

modal aerosol microphyics schemes

21
Q

what are some disadvantages of modal schemes?

A

-cannot capture all the potential detail in the distribution
-simplifications can cause biases in simulated growth rates

22
Q

what is GLOMAP?

A

a sectional aerosol microphysics model

23
Q

why was GLOMAP developed?

A

-it is able to calculate the details of the aerosol size distribution on a global scale

24
Q

when can sectional models only be used in GCMs?

A

-when the bin resolution is reduced significantly

25
Q

why might data sets from observations not be continuous?

A

instrument malfunction, maintenance etc

26
Q

why don’t most GCMs not use regular lat-lon grids?

A

to overcome difficulties with the grid spacing at poles

27
Q

describe what GCM grids are like vertically

A

-terrain following
-based on pressure as verticle coordinate system

28
Q

do GCM grids follow orography?

A

-not really, the grid box-resolution is too low to resolve all features

29
Q

what is the CIS schematic?

A

collocation of gridded data onto an ungridded sampling where the altitude component of the data if defined on a hybrid height grid

30
Q

what is nudging?

A

additional terms are introduced to equations that govern the evolution of temp and winds and nudges them towards observed values from reanalysis data

31
Q

what is lagrangian measurements?

A

takes measurements with balloon moving with flow

32
Q

what is eularian measurements?

A

takes measurements at surface as flow passes by

33
Q

how might we identify underlying weaknesses driving descrepencies between simulated and observed data

A

-improve understanding of the underlying physical processes in the real world
-use more advanced methodologies to model aerosol microphysics
-identify GCM structural and parametric uncertainties

34
Q

how do single particle back-trajectory models work?

A

-3 individual trajectories calculated
-initiated 1 hr apart
-each trajectory steps backwards in time through the wind field in hourly steps

35
Q

what is back-trajectory analysis good for?

A

the quantification of the source influence distribution on receptor station

36
Q

why was HYSPLIT developed?

A

during the arms race we needed to determine where nuclear tests were conducted using global measurements of nuclear fallout

37
Q

what does cluster analysis allow?

A

large quantities of data to be divided into distinct aerosol size distributions

38
Q

what is good about eularian GCMs?

A

-easy interpretation
-evaluation of model aerosol climatology
-hilights regions of major discrepancy for model improvement
-efficient to produce

39
Q

what is bad about eularian GCMs?

A

does not tell us what model or process is causing the observed difference compared to measurements from the arctic

40
Q

what does potential source regions mean in practice?

A

-strong sources may be masked by strong sinks during transport
-less than average sink strength during transport may result in opposite relation

41
Q

why is antarctica good for studying pre-industrial atmosphere?

A

-antarctica is cleanest part of earths troposphere

42
Q

what are some benefits to langrangian data?

A

-allows us to understand where model underperform and why

Aerosols, Clouds, Atmospheres (12 decks)

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