The Vertical Structure of Climate

Question 1

For which depths of the ocean is it relevant for short-term climate change and its specific heat capacity.

Answer 1

The top 50-100m

Question 2

In which section of the atmosphere doe we witness weather phenomena?

Answer 2

The troposphere

Question 3

Which layer of the atmosphere is stable?

Answer 3

The stratosphere (it has a positive temperature gradient with height) therefore it is in radiative equilibrium.

Question 4

What does radiative equilibirum mean for the stratosohere?

Answer 4

The only motion is generated from absrption/emission of radiation, there is no atmospheric convection. The energy is balanced by SW absorption by ozone and LW emission by CO2 (There is no water vapour present in the stratosphere)

Question 5

What is the scale height?

Answer 5

RT_0/g - a distance over which a physical quantity like pressure, density or radiation decreases by a factor of e.

Question 6

How do we define the heating rate?

Answer 6

rho . Q where Q(z, lambda) is the specific heating rate per kilogram per unit wavelength.

Question 7

What does the Chapman Layer refer to?

Answer 7

Following increasing optical depth downwards, the exponent shows heating initially increasing as we encounter more absorber, before decreasing again as the amount of radiation left in the beam available to absorb is reduced.

Question 8

What assumption can we make about LW and SW heating/cooling in the stratosphere when deriving the heating rate?

Answer 8

Neglect LW heating in the Schwarzchild Equations.

Question 9

Summarise the vertical structure of the troposphere.

Answer 9

It is unstable as the source of heating is due to radiation from the surface, inducing a strong convection current.

Question 10

What assumption do we make for a parcel away from clouds and the surface in the troposphere? (When considering radiative-convective based arguments)

Answer 10

Away from the surface and outside of clouds, heat gain or loss by a parcel
of air is typically determined by radiation alone and has a slow timescale. We can assume it is adiabatic (delta Q = 0)

Question 11

What does adiabatic mean?

Answer 11

A process or condition in which heat does not enter or leave the system concerned.

Question 12

How do we derive the dry adiabatic lapse rate?

Answer 12

Assume adiabatic condition, hence delta Q = 0. Substitute this into hydrostatic pressure and determine dT/dz.

Question 13

What does it mean when the rate of change of the environmental temp with height is LESS THAN the dry adiabatic lapse rate?

Answer 13

dT_E/dz < - Gamma_d
The environmental lapse decreases more rapidly than the dry adiabatic lapse rate. For a parcel displaced upwards, the temp decreases as -Gamma_d, hence the parcel is warmer, and continues to rise as it is less dense (by the ideal gas law).

Question 14

What does it mean when the rate of change of the environmental temp with height is MORE THAN the dry adiabatic lapse rate?

Answer 14

dT_E/dz > - Gamma_d .
The environmental lapse rate is less steep than the dry adiabatic lapse rate. For a parcel displaced upwards is cooler (less dense) than surroundings and so settles back down again.

Question 15

What can be deduced about the environmental lapse rate in the troposphere and a displaced parcel?

Answer 15

Heating by subsequent convection (from an unstable rising parcel) drags the environmental profile back to equal the dry adiabatic lapse rate.

Question 16

What can be deduced about the environmental lapse rate in the stratosphere and a displaced parcel?

Answer 16

The stratosphere’s stability cuts off convection due to the positive temperature gradient.

Question 17

What effect does the presence of water vapour have on Gamma_d.

Answer 17

The adiabatic lapse rate is shallower in reality as there is added latent heat of condensation when a parcel of air has moisture, causing the parcel to cool more slowly.

Question 18

What is the equation for saturation vapour pressure?

Answer 18

de_s/dT = L e_s/(R_w T^2)

Question 19

What can we say about the equilibirum state of the troposphere?

Answer 19

It is in radiative-convective equilibrium.

Question 20

What can we say about the equilibirum state of the stratosphere?

Answer 20

It is in radiative equilibrium.

Question 21

Outline the vertical structure of the ocean.

Answer 21

There is no instability-driven convection as the warmer water lays on top.

Question 22

If T_s increases, what effect does that have on the rate at which the atmospheric temperature increases in the troposphere?

Answer 22

It will increase at approximately the same rate due to opacity and optical depth.

Question 23

What effect does increasing CO2 concentration have in the stratosphere?

Answer 23

Increases a_LW (absorption and therefore optical depth) hence reducing the stratosphere temp as there is an increase in longwave emission whilst SW absorption remains the same as there is no impact on ozone.