Measurement of Scattering Extinction Coefficient of Atmospheric Fine Particles; The Fine Particle Mass Loading at Nsukka; and Their Effects on Solar Radiation

This project centres on measurement of the scattering extinction
coefficient of atmospheric fine particles of diaeter 2.5~ or
0 less at Nsukka, latitude 6.8 N, longitut 7,35'fZ :vc? 488m
above sea level. A sensitive integratiag wphebcmeter model 1597
-7 -1 o?? sensitivity 10 m was used for the meas:i.:c~en.ts. The period
under review is from 13th December 1985 t.0 the end of %arch 1986.
Other parameters computed are fine particle maloaoing 2er unit
volume of air, FPM, Total Scattering Extinction Coefficient,
bscaCt'
and local visual distance,
Lvd'
We have obtained the instantaneous
values at one hour intervals as well as the average hourly values
of these parameters for each day. We have also attempted to
correlate the results of our measurements with measurements of
total and diffuse solar radiation at Nsukka within the same period,
Our measurements show that scattering extinction coefficient,
-4 -1 b has maximum value of about 10.00 x 10 m which corresponds SP -4 to fine particle mass loading, FPM of about 3.03 x 3.n j/m3 on
a typical harmattan day (20th, 21st December 192" :~.:r.h, or 18th
-4 -1 January 1986). It has a minimum value of Q 65 s 10 m
-4 3
corresponding to fine particle mass load-;) y of 1.2 x 10 g/m on
February 27 and March 2 which are outsi2e th:: 2:irmattan ?eriod.
Results got also reveal that there were r;::.,rf2 dust particles in
the atmosphere in the months of December ~nd Jkiauary and canseqliently
more scattering occurred during this period than in the months
of February and March. This confirms the j.,-.~.~-;.. !die£ that the
in~nths of December and January fall withia peak p-viod of
hsrmattan. Various correlation graphs of total ulld diffuse
solar radiation with fine particle mass lod&ny ad sca+.tering
extinction coefficient were plotted. Cloe scrutLny of tlLe
curves shows that there were virtually little or no hourly
t
correlation. The reason may be due to the short period spanned.
With extended period of two to three years one may be able to see
some correlation at ieast with regards to diffuse radiation and
scattering extinction co-efficient where theory predicts that diffuse radiation is direcby qroportional to scattering extinction
coefficient. Over and above this assertion we are tempted to
conclude that more of the patticles actually responsible for
diffuse radiation are not withm the sensitivity range of the
instrument. We hope that with inproved technolcgy sad e.xt5nded
range of the nephelometer better Crrrelation belljcen sol?:
radiction and th iastzument' s paraaters will be c:cdined.