Aerosol optical properties over Ilorin (80 19’N, 40 20’E ), Nigeria an Urban city in sub Sahel West Africa is presented in this study during the period January 2005 – December 2007. The aerosol direct radiative forcing (ADRF) at the bottom and the top of the atmosphere ΔF, and forcing efficiency ΔFeff evaluated from the Sun-photometer measurements during the harmattan period (often associated with desert dust + biomass burning) is reported for this region for the first time. Measurements show pronounced seasonal influence with maximum dust loading during harmattan seasons (November to March) of every year. Large values of aerosol optical depth (AOD), τ500nm > 1.50 combined with low values of Ångström exponent α < 0.2 were mainly observed during the dust periods. The aerosol volume size distributions show distinct fine (geometric mean radii of 0.18 ±0.13 µm) and coarse modes (geometric mean radii of 4.71±4.55 µm) with a remarkable increase in the volume concentration during the harmattan dust episodes of November-March. The aerosol forcing efficiency during the harmattan season is estimated to be -119.63±13.62 Wm -2 / τ500nm , -113.63 ±13.38 Wm -2 / τ500nm and -82.94 ±4.21 Wm -2 / τ500nm for 2005, 2006 and 2007 respectively at the bottom of the atmosphere (BOA). At the top of the atmosphere (TOA), the forcing efficiency were estimated to be -38.10 ±4.77 Wm -2 / τ500nm, -45.26 ±5.00 Wm -2 / τ500nm, and -41.26±1.49 Wm -2 / τ500nm for same years respectively
PAPER TITLE :SEASONAL VARIABILITY OF AEROSOL OPTICAL PARAMETERS AND RADIATIVE FORCING OVER SUB- SAHEL WEST AFRICA
JOURNAL Of SUSTAINABLE TECHNOLOGY | VOLUME 2 NUMBER 1 2011
Paper Details
- Author(s) : OGUNJOBI K.O
- Abstract:
