Questions From Formatives

Question 1

Why is water vapour not included in the IPCC?

Answer 1

Assumed that the amount of water vapour is negligible compared to natural sources

Question 2

What does the claussius-claperyon equation show about the water vapour?

Answer 2

The amount of water vapour that can be held in he atmosphere is determined by the temp of the atmosphere
CC equation shows water vapour amount is exponentially dependent on temperature

Question 3

What criteria are NPF events defined as? (4)

Answer 3

1. A distinct new mode of particles appears in the particle number size distribution
2. This mode is located initially below 25 nm of the particle diameter
3. The mode prevails for more than an hour
4. The mode shows signs of growth

Question 4

Why is spring/summer the season with the highest NPF rate?

Answer 4

-higher incident solar radiation
-horizontal pressure gradient is flatter in summer- air speed is lower so local sources have a larger influence so more time for gas-to-particle conversion
-air masses with high conc of Aitken and accumulation mode particles present a high condensation/coagulation sink, decreasing lifetime or newly formed vapours participating in NPF and removing newly formed ultra fine particles

Question 5

What controls nocturnal NPF?

Answer 5

-not well understood
-highly oxygenated multifunctional compounds (HOMs) can participate in the initial steps of NPF by stabilising sulphuric acid
-low condensation sinks is a key factor

Question 6

Is dry deposition an important removal process for NPF? Why?

Answer 6

No
Loss by dry deposition slower than coagulation with larger particles so process is not fast enough to be important

Question 7

Which is faster dry deposition or coagulation?

Answer 7

Coagulation

Question 8

When might the surface deposition of nuclei be important in NPF?

Answer 8

-very extreme conditions
-low mixed layer height combined with relatively clean air and large mean size of Nucleation mode

Question 9

Does regional NPF increase or decrease the albedo of clouds in the vicinity of the event?

Answer 9

-Conflicting studies on this
-likely NPF increases CCN at high supersaturations but can reduce CCN at lower supersaturations
-low understanding of NPF and their interactions contributes to this uncertainty

Question 10

What wind speed does generation of aerosols from sea spray become efficient?

Answer 10

6 ms-1

Question 11

Why is aerosol turnover so high in the Arctic?

Answer 11

-shallow boundary layer so even small dry deposition velocities can result in fast turnover times
-in situ production of particles and surface sources important for replenishing aerosol conce

Question 12

What are some challenges in developing accurate cloud droplet parameterisation in GCMs/ESMs?

Answer 12

Processes are sub grid compared to GCM grids
Difficult to retrieve aerosol/cloud properties at the grid scale of GCMs
Online evaluation is often needed as the inputs are parameterised

Question 13

When analysing aerosol perturbation why is it important to compare the cloud properties at event to average cloud properties

Answer 13

To separate impact of aerosol perturbations from natura meteorology

Question 14

What type of clouds have the strongest net cloud radiative forcing?

Answer 14

Marine stratocumulus clouds