Answers for Ozone Quizzes

Quiz: Ozone Introduction

  1. Why is stratospheric ozone important for life on Earth?

    Stratospheric ozone builds the shield that protects life from harmful UV radiation, especially UV-B.

  2. How much ozone is present in the Earth’s atmosphere?

    There is an average total column ozone content of about 300 DU in the Earth’s atmosphere

  3. What happened in the seventies that was discovered in the early eighties?

    ODSs started to destroy the stratospheric ozone layer which was seen in measurements starting in the early 1980s and manifested itself as an ozone hole in Antarctica.

  4. What was done to reduce the destruction of ozone?

    Because of the high risks for life in an ozone depleted atmosphere a treaty, the Montreal protocol, was negotiated and signed on 16 September 1987 to be effective on 1 January 1989. The nations agreed to reduce ozone depleting substances from the Earth’s atmosphere. The Montreal protocol was ratified by all 197 United Nations members and is considered one of the most successful UN treaties. There are 9 updates so far (2021) to the Montreal Protocol increasing the number of forbidden ozone depleting substances more and more.

  5. What is done to publicize the state of ozone every four years?

    The United Nations Environment Programme and the World Meteorological Organization organize since 1981 assessment reports for the state of ozone in the Earth’s atmosphere. The state of the atmosphere is monitored using satellite imagery and climate model preditions. The reports appear regularly, now every four years (e.g. 2018, 2022).

Quiz: Total Column Ozone

  1. What is the difference between a total column and a partial column of ozone?

    Columns are calculated by integrating or summing up the chemical species for which the column has to be calculated from one level in the atmosphere to another level. The total column is calculated from the Earth’s surface to the top of the atmosphere, partial columns are yielded by integrations over only parts of the atmosphere (e.g. over the troposphere for tropospheric columns).

  2. What is a Dobson Unit?

    The Dobson Unit is a unit of measurement for ozone columns. One Dobson Unit is 0.4462 mmol/m2 (or 1 mmol/m2 is approximately 2.241 DU. Expressed in molecules 1 DU is 2.687×1020 molecules/m2.

  3. How do you get from a data field of volume mixing ratios (latitude, longitude, height) into a total column? What steps are necessary?

    In order to calculate the total column we need the ozone number density, NO3 which can be calculated from volume mixing ratio, vmrO3, the temperature, T in Kelvin and the pressure in hPa using the formula

    NO3 = vmrO3 × pressure / (1.38 × 10-19 × temperature)

    Then summing the ozone number densities over altitude in m we get the number of molecules/m2. This value can be converted into a Dobson Unit knowing that 1 DU is 2.687×1020 molecules/m2.

  4. What is a zonal mean?

    In Earth sciences zonal and meridional are used speaking about directions on the globe. Zonal is in the direction of a latitude line (east-west direction) and meridional in the direction of the longitude line (north-south direction). A zonal mean then is a mean of a quantity along latitude for all its longitudes, i.e a value z(lat,lon) becomes z_zonal(lat).

  5. Why would one use a multi model mean?

    Climate projections show a variability for their projections. In order to get a more robust climate projection it is therefore useful to take a mean of the different climate projection in order to get the most likely outcome. The multi-model mean uses results from different models which use same scenarios for climate prejections with differnt outcomes. Multi-model means allow therefore to reduce the effect of individual models in the projection.

  6. What is ozone return?

    Ozone depletion has been slowing down and the ozone abundance is growing again in the stratosphere. It can be seen in model projections that ozone values can grow to pre-depletion values. The time when this happens is called ozone return date or ozone recovery date. The time for pre-depletion values vary. Often 1980 is used because of available ozone measurements from satellites.

  7. How can models be compared that have totally different values (offsets) from each other?

    The easiest method is to normalize the models to a measurement point at a certain year.