A New MODIS C6 Dark Target and Deep Blue Merged Aerosol Product on a 3 km Spatial Grid

Muhammad Bilal,James Campbell,Xiaojing Shen,Zhongfeng Qiu,Majid Nazeer,Scott Spak

doi:10.3390/rs10030463

Abstract

In Moderate Resolution Imaging Spectroradiometer (MODIS) Collection (C6) aerosol products, the Dark Target (DT) and Deep Blue (DB) algorithms provide aerosol optical depth (AOD) observations at 3 km (DT3K) and 10 km (DT10K), and at 10 km resolution (DB10K), respectively. In this study, the DB10K is resampled to 3 km grid (DB3K) using the nearest neighbor interpolation technique and merged with DT3K to generate a new DT and DB merged aerosol product (DTB3K) on a 3 km grid using Simplified Merge Scheme (SMS). The goal is to supplement DB10K with high-resolution information over dense vegetation regions where DT3K is susceptible to error. SMS is defined as “an average of the DT3K and DB3K AOD retrievals or the available one with the highest quality flag”. The DT3K and DTB3K AOD retrievals are validated from 2008 to 2012 against cloud-screened and quality-assured AOD from 19 AERONET sites located in Europe. Results show that the percentage of DTB3K retrievals within the expected error (EE = ± (0.05 + 20%)) and data counts are increased by 40% and 11%, respectively, and the root mean square error and the mean bias are decreased by 26% and 54%, respectively, compared to the DT3K retrievals. These results suggest that the DTB3K product is a robust improvement over DT3K alone, and can be used operationally for air quality and climate-related studies as a high-resolution supplement to the current MODIS product suite.

Highlights

Atmospheric aerosols, small tiny particles suspended in the atmosphere, are emitted from multiple sources by anthropogenic and natural activities, including smoke, volcanic ash, dust particles, biomass burning, and particular matters
In the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5.1 (C5.1) level-2 operational aerosol product, daily aerosol optical depth (AOD) observations at 10 km resolution are available over dark surfaces from the Dark Target (DT10K) land algorithm [13,27,28], over ocean surfaces from the DT ocean algorithm [13,29], and over bright surfaces from the Deep Blue (DB10K) algorithm [16,30,31]
The main objective of this study is to describe and evaluate a new DT and DB-merged (DTB3K) AOD product on a 3 km grid to improve the quality of AOD retrievals and spatial coverage over vegetated and non-vegetated land surfaces

Summary

Introduction

Atmospheric aerosols, small tiny particles suspended in the atmosphere, are emitted from multiple sources by anthropogenic and natural activities, including smoke, volcanic ash, dust particles, biomass burning, and particular matters. In the MODIS Collection 5.1 (C5.1) level-2 operational aerosol product, daily AOD observations at 10 km resolution are available over dark surfaces from the Dark Target (DT10K) land algorithm [13,27,28], over ocean surfaces from the DT ocean algorithm [13,29], and over bright surfaces from the Deep Blue (DB10K) algorithm [16,30,31]. These AOD observations are unable to resolve many local-level aerosol features due to their inherently coarse resolution. DT3K is generated using the same inversion method as used in DT10K, the only difference being in the selection of the dark target pixels [32]

Objectives

Methods

Results