Homework Problem Set 3 Distribution 23 November 2006, Hand-In 30 November 2006

Homework Problem Set 3

Distribution 23 November 2006, Hand-In 30 November 2006

Problem 1: Farman et al. and the further development

(a) Why is total ozone during Oct-Nov rising at Halley Bay and Argentine Island, and why is it slowly dropping again thereafter? See attached Figure from Farman et al. (1985). The answer is related to atmospheric dynamics and it might help to study Section 3.6.2 in Brasseur and Solomon.

(2) (b) Why were the October values of total ozone dropping more quickly at Halley

Bay than at Argentine Island?

(1) (c) Plot a third curve into the panel for Halley Bay showing today’s ozone sea-

sonal cycle.

(2)

Problem 2: Ozone Hole Chemistry

(a) Which two fundamental roles do PSCs play in ozone hole chemistry?

(2) (b) Nitrogen oxides may catalytically destroy ozone. Farman thought that they

are the main cause of the ozone hole. Would you say that in reality they are an ozone protector under Antarctic winter conditions? Justify your answer.

(1) (c) Given the relative rate with which HNO

and Cl

dissociate, do surface reac-

tions on PSC surfaces shift the balance more in favor of NO

- or ClO

-induced ozone destruction?

(1) (d) Speculate which of the two roles in (a) is more important under Antarctic con-

ditions, which under Arctic conditions! Give arguments supporting your specu- lation.

(2)

Problem 3: Methane in the stratosphere

Methane destruction is slow in the stratosphere. Calculate its lifetime with respect to the three major oxidants which attack methane. Assume oxidant number densities at 25 km and 40 km altitude (tables). At what altitude is methane destroyed more effi- ciently? Why are methane concentrations decreasing even in the polar winter strato- sphere?

(3)