MODEL PREDICTION AND CLIMATOLOGY OF AEROSOL OPTICAL DEPTH (?550) AND ANGSTROM EXPONENT (?470-660) OVER THREE AEROSOL ROBOTIC NETWORK STATIONS IN SUB-SAHARAN AFRICA USING MODERATE RESOLUTION IMAGING SPECTRORADIOMETER DATA

Abstract

The spatial and temporal variations of aerosol optical depth at 550 nm (?₅₅₀) and Angstrom exponent derived from 470 and 660 nm (?_470-660) over Nairobi (NAI), Skukuza (SKU) and Ilorin (ILO) Aerosol Robotic Network (AERONET) stations in sub-Saharan Africa, as recorded by Moderate Resolution Imaging Spectroradiometer (MODIS) satellites for fifteen years (2000-2015), were examined in relation to their climatologies and prediction. The MODIS measurements of ?₅₅₀ and ?_470-660 from aqua (MYD04) and terra (MOD04) satellites were used in this study. Retrievals of ?₅₅₀ for both satellites were validated with AERONET ?₅₅₀ for the same period. The validation results showed that they compare favourably over the three stations, but MOD04 performed better than MYD04 data in NAI and ILO for ?₅₅₀. This shows that the ?₅₅₀ of NAI and ILO are best captured using the MOD04 data while that of SKU is best with MYD04. It was also discovered that MODIS underestimated AERONET ?₅₅₀ data over NAI and SKU. The most polluted station is ILO while the least polluted one is NAI. Similarly, the station with the highest concentration of absorbing aerosols is NAI and the least was observed in ILO. The aerosol climatology shows that the most polluted months in NAI, SKU and ILO are October, June and March respectively. On the other hand, February, November and March has the highest amount of scattering aerosols in the atmosphere for NAI, SKU and ILO respectively. The highest amount of absorbing aerosols was found, respectively, in the months of June, June and August. The generated time series (TS) models are all good, though a general underestimation of the parameters by the models was also observed.

http://dx.doi.org/10.4314/njt.v39i1.29