Definitions for Dobson Unit
dob·son unit

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1. Dobson unit

   The Dobson unit (DU) is a unit of measurement of the amount of a trace gas in a vertical column through the Earth's atmosphere. It originated, and continues to be primarily used in respect to, atmospheric ozone, whose total column amount, usually termed "total ozone", and sometimes "column abundance", is dominated by the high concentrations of ozone in the stratospheric ozone layer. The Dobson unit is defined as the thickness (in units of 10 μm) of that layer of pure gas which would be formed by the total column amount at standard conditions for temperature and pressure (STP). This is sometimes referred to as a 'milli-atmo-centimeter.' A typical column amount of 300 DU of atmospheric ozone therefore would form a 3 mm layer of pure gas at the surface of the Earth if its temperature and pressure conformed to STP. The Dobson unit is named after Gordon Dobson, a researcher at the University of Oxford who in the 1920s built the first instrument to measure total ozone from the ground, making use of a double prism monochromator to measure the differential absorption of different bands of solar ultraviolet radiation by the ozone layer. This instrument, called the Dobson ozone spectrophotometer, has formed the backbone of the global network for monitoring atmospheric ozone and was the source of the discovery in 1984 of the Antarctic ozone hole.

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1. Dobson unit

   The Dobson unit is a unit of measurement of the columnar density of a trace gas in the Earth's atmosphere. It originated, and continues to be widely used, as a measure of total-column ozone, which is dominated by ozone in the stratospheric ozone layer. One Dobson unit refers to a layer of gas that would be 10 µm thick under standard temperature and pressure, sometimes referred to as a 'milli-atmo-centimeter.' For example, 300 DU of ozone brought down to the surface of the Earth at 0 °C would occupy a layer only 3 mm thick. One DU is 2.69×10^16 ozone molecules per square centimetre, or 2.69×10^20 per square metre. This is 0.4462 millimoles of ozone per square metre. A baseline value of 220 DU is chosen as the starting point for an ozone hole since total ozone values of less than 220 Dobson Units were not found in the historic observations over Antarctica prior to 1979. Also, from direct measurements over Antarctica, a column ozone level of less than 220 Dobson Units is a result of the ozone loss from chlorine and bromine compounds. In addition, Dobson Units are often used to describe total column densities of Sulfur Dioxide, which occurs in the atmosphere in small amounts due to the combustion of fossil fules, from biological processes releasing dimethyl sulfide, or by natural combustion such as forest fires. Large amounts of sulfur dioxide may be released into the atmosphere as well by volcanic eruptions. The Dobson Unit is used to describe total column amounts of sulfur dioxide due to the fact that it appeared in the early days of ozone remote sensing on ultraviolet satellite instruments.

How to pronounce Dobson Unit?

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Numerology

1. Chaldean Numerology

   The numerical value of Dobson Unit in Chaldean Numerology is: 8

2. Pythagorean Numerology

   The numerical value of Dobson Unit in Pythagorean Numerology is: 7

References

1. ^ Wikipedia
   https://en.wikipedia.org/wiki/Dobson_Unit
2. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=Dobson Unit