Development of a Regression Model for Estimating Daily Radiative Forcing Due to Atmospheric Aerosols from Moderate Resolution Imaging Spectrometers (MODIS) Data in the Indo Gangetic Plain (IGP)

Abstract

The assessment of direct radiative forcing due to atmospheric aerosols (ADRF) in the Indo Gangetic Plain (IGP), which is a food basket of south Asia, is important for measuring the effect of atmospheric aerosols on the terrestrial ecosystem and for assessing the effect of aerosols on crop production in the region. Existing comprehensive analytical models to estimate ADRF require a large number of input parameters and high processing time. In this context, here, we develop a simple model to estimate daily ADRF at any location on the surface of the IGP through multiple regressions of AErosol RObotic NETwork (AERONET) aerosol optical depth (AOD) and atmospheric water vapour using data from 2002 to 2015 at 10 stations in the IGP. The goodness of fit of the model is indicated by an adjusted R2 value of 0.834. The Jackknife method of deleting one group (station data) was employed to cross validate and study the stability of the regression model. It was found to be robust with an adjusted R2 fluctuating between 0.813 and 0.842. In order to use the year-round ADRF model for locations beyond the AERONET stations in the IGP, AOD, and atmospheric water vapour products from MODIS Aqua and Terra were compared against AERONET station data and they were found to be similar. Using MODIS Aqua and Terra products as input, the year-round ADRF regression was evaluated at the IGP AERONET stations and found to perform well with Pearson correlation coefficients of 0.66 and 0.65, respectively. Using ADRF regression model with MODIS inputs allows for the estimation of ADRF across the IGP for assessing the aerosol impact on ecosystem and crop production.

Spectral and seasonal variations of aerosol radiative forcing with special reference to Kanpur, Indo-Gangetic Basin

“…The AERONET is a broad remote sensing aerosol network based on ground-based observations obtained from the device called CIMEL sun photometer. Everyday observations of the optical depth of the aerosol recorded by MODIS Terra satellite in the region of the Indo-Gangetic Basin are also in good agreement with the measurements by AERONET (18) . Regionally, there are various aerosols networks.…”

Spectral and seasonal variations of aerosol optical depth with special reference to Kanpur, Indo-Gangetic Basin

“…This site is surrounded by small to large scale industries where, industrial emission is a major source of anthropogenic aerosols (23) .The synoptic wind pattern is observed from northwest to southwest (24) . The daily AOD retrieved by the MODIS Terra at the Indo-Gangetic Basin stations is also found in good agreement with the AERONET measured AOD (25) .The continuous measurements of direct sun rays intensities arriving the surface of this region have also been done for long time.…”

“…AERONET provides worldwide observations of the optical properties of aerosols in different aerosol modes, with high temporal resolution and three levels of data quality: level 1.0 (unshielded), level 1.5 (cloud screened) and level 2.0 (cloud screened and quality assurance) (26) . Owing to its high precision (accuracy: ±0.01), long working history and global reach, the data of AERONET data has been utilized as a reference level for AOD measurement and model validation of many aerosol sensors (2,26) . The level 2.0 daily average monthly aerosol products have been used in this study.…”

“…Thus, for airmass 1<m≤ 3, the absolute uncertainty in AOD may be between ±0.02 to ±0.05. AERONET considers an absolute uncertainty in the range from 0.01-0.02 for the case of CIMEL sun photometer (26) . Ideally, the outputs taken from all the datasets are differentiated at common wavelength 0.55 µm.…”