Radar and Satellite Meteorology II

Prof. Leonard K. Amekudzi

Meteorology and Climate Science Unit,

Department of Physics
Kwame Nkrumah University of Science and Technology, Kumasi Cell Phone number:
0201842237
leonard.amekudzi@gmail.com

June 21, 2021

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Outline :

Seasonal changes in :
The ozone layer
Tropospheric trace species
Precipitation
Observations of temperature
Advection of air mass

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Processes in the troposphere and the stratosphere

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Trace Gas : Measuring Trace Gas Properties

There are several trace gases that are relevant for air quality, some are
O3 , HCHO, NO2 , SO2 , and CO
Measuring Trace Gases from Space
Satellites detect backscattered UV, visible, and/or emitted thermal
radiation.
Trace gad have distinct absorption spectrum, it is identified by its
“spectral fingerprint”.
Optical Depth
Optical Depth = (Cross Section × Trace Gas Abundance)
Optical depth or thickness (tλ ) is a measure of the extinction of the solar
beam by trace gases. In other words, trace gases in the atmosphere can
block sunlight by absorbing or by scattering light

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 t λ = (ωλ ×µv )
where µv is the trace gas abundance over the atmospheric path length,
such as a vertical column

Vertical Distribution
Very little information can be obtained on the vertical distribution of trace
gases in the troposphere from a nadir view. For some trace gases, like
ozone, measurement techniques using different wavelengths (e.g.,
combining UV, visible, and IR measurements) can provide some vertical
information – The penetration depth of photons increases with increasing
wavelengths.
Some information on vertical distribution can be inferred by taking the
altitude of the trace gas source and its lifetime into account. Trace gas
profiles are the number density divided by the tropospheric column (units
= 1/km)

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Some information on vertical distribution can be inferred by taking the
altitude of the trace gas source and its lifetime into account Examples:
NO2 is short-lived and primarily emitted from fossil fuel combustion (e.g.,
cars, power plants), so most NO2 is found near the surface
SO2 is similar to NO2 for man-made sources (e.g., power plants), but it
can be high in the atmosphere when volcanoes are the source.

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Total Ozone :

Total ozone for October from Faraday [65S] and Halley Bay [75S]. Data is
obtained. (Update from Farman et al. [1985])
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TOMS: Observation of the Ozone Hole :
Ozone is formed in the
Antarctic winter / spring
The formation of Polar
Stratospheric Clouds
PSC in the extremely
cold vortex
rapid ozone destruction
by ClO and BrOas the
sun rises
end of ozone destruction
after warming when
chlorine is transformed
back to its reservoirs
HCland ClONO2 and
vortex air mixes with
ozone rich air.
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Total ozone values measured by GOME for 15 September 2002 and 22
September 2002. Increase in total ozone value at mid-high latitude on 22
September 2002 is clearly visible. This effect was attributed to Solar
proton effect.
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Tropical temperature anomalies

Tropical temperature anomalies from HadAT2, NCEP, and ECMWF data

set for the period 1965-1995. Anomalies from HadAT2 are shown in thick
gray line, NCEP and ECMWF are squares and filled circles, respectively.
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Observation for pollution and biomass burning

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NO2 Concentration

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ClO and OClO concentrations

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Cycle of Trace Gases

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