Statistical Analysis of Aerosols Characteristics from Satellite Measurements over East Africa Using Autoregressive Moving Average (ARIMA)

Abstract

Aerosols have become a major subject of concern at global, regional and local scales. They influence Earth’s radiation budget by scattering and absorbing solar energy resulting in atmospheric cooling and warming respectively. However, immense efforts have been devoted to monitoring atmospheric aerosols using various techniques ranging from in-situ, ground and satellite-based remote sensing and modeling techniques. Thus, time series analysis and forecasting have gained momentum over recent decades. The current study performed a time series analysis using Box-Jenkins procedure-based ARIMA (Autoregressive Integrated Moving Average) model for aerosol properties (Total Aerosol Optical Depth, TAOD; Absorption Aerosol Optical Depth, AAOD; Scattering Aerosol Optical Depth, SAOD and Direct Aerosol Radiative Forcing, DARF) over EA derived from satellite platforms. The formulation process in MATLAB followed by the current study has been outlined with a view to generating the best fitting seasonal ARIMA (p, q , d ) × (P Q D ) model. The finding for the forementioned characteristics reveals clear seasonal variation, hence, differencing was done. The Autocorrelation Function (ACF) and Partial Autocorrelation Function (PACF) of differenced series are estimated and the significant lags are used to find out the order of the model. The statistical parameters (RMSE, MAE, MAPE, MASE and normalized BIC) were estimated for testing the validity of ARIMA models so formulated. The current study found that ARIMA (1, 0, 0) × (2, 1, 2)12 model is adequate for forecasting and was therefore used to forecast aerosol characteristics for the year 2022-2025 over EA domain. ARIMA model ascertained can be applied to other fields of study such as climatology, and climate change among other areas to predict future values so that timely control measures can effectively be planned.