Aerosol Microphysics 2

Question 1

what is the sectional approach in GCMs?

Answer 1

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

Question 2

what is the modal approach in GCMs?

Answer 2

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

Question 3

what is more costly and complex? Sectional or modal?

Answer 3

sectional is most costly and complex

Question 4

what is the GDE?

Answer 4

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

Question 5

is there a general solution to the GDE?

Answer 5

no it must be solved numerically

Question 6

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

Answer 6

increases particle number, increases particle mass, increases particle SA

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

decreases particle number, SA, and mass

Question 10

what is time splitting and operator splitting?

Answer 10

-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

Question 11

what do bulk aerosol models measure/track?

Answer 11

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

Question 12

what are some benefits of bulk aerosol models?

Answer 12

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

Question 13

what are some drawbacks for bulk aerosol models?

Answer 13

-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

Question 14

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

Answer 14

n x m

Question 15

what does the accuracy of sectional models depend on?

Answer 15

the number of sections

Question 16

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

Answer 16

particle size distribution is continuous and monodisperse

Question 17

name 4 sectional model algorithms

Answer 17

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

Question 18

what are 4 transformation processes?

Answer 18

-nucleation
-coagulation
-condensation
-deposition

Question 19

what do sectional schemes represent well?

Answer 19

complex aerosol dynamics

Question 20

what is the most commonly used approach in GCMs?

Answer 20

modal aerosol microphyics schemes

Question 21

what are some disadvantages of modal schemes?

Answer 21

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

Question 22

what is GLOMAP?

Answer 22

a sectional aerosol microphysics model

Question 23

why was GLOMAP developed?

Answer 23

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

Question 24

when can sectional models only be used in GCMs?

Answer 24

-when the bin resolution is reduced significantly

Question 25

why might data sets from observations not be continuous?

Answer 25

instrument malfunction, maintenance etc

Question 26

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

Answer 26

to overcome difficulties with the grid spacing at poles

Question 27

describe what GCM grids are like vertically

Answer 27

-terrain following -based on pressure as verticle coordinate system

Question 28

do GCM grids follow orography?

Answer 28

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

Question 29

what is the CIS schematic?

Answer 29

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

Question 30

what is nudging?

Answer 30

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

Question 31

what is lagrangian measurements?

Answer 31

takes measurements with balloon moving with flow

Question 32

what is eularian measurements?

Answer 32

takes measurements at surface as flow passes by

Question 33

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

Answer 33

-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

Question 34

how do single particle back-trajectory models work?

Answer 34

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

Question 35

what is back-trajectory analysis good for?

Answer 35

the quantification of the source influence distribution on receptor station

Question 36

why was HYSPLIT developed?

Answer 36

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

Question 37

what does cluster analysis allow?

Answer 37

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

Question 38

what is good about eularian GCMs?

Answer 38

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

Question 39

what is bad about eularian GCMs?

Answer 39

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

Question 40

what does potential source regions mean in practice?

Answer 40

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

Question 41

why is antarctica good for studying pre-industrial atmosphere?

Answer 41

-antarctica is cleanest part of earths troposphere

Question 42

what are some benefits to langrangian data?

Answer 42

-allows us to understand where model underperform and why