Estimation and inter-comparison of dust aerosols based on MODIS, MISR and AERONET retrievals over Asian desert regions

Abstract

This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth (AOD) and Angstrom component over Asian desert regions using thirteen years data (i.e., 2001-2013) retrieved from Aerosol Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR). These regions include Solar Village, Dunhuang and Dalangzadgad and are considered as origin of desert aerosols in Asia. Mann Kendall trend test was used to show the trend of AOD. The relationship of AOD with weather parameters and general AOD trend over different wavelengths has also been shown. AOD's trend has been observed significant throughout the year in Solar Village, while in Dunhuang and Dalanzadgad the significant trend has been found only in peak period (March-June). Analysis show high values of AOD and low values of angstrom in Solar Village during peak period. In Chinese desert regions high values of AOD have been found during peak period and low values in pre peak period. Significant relationship has been observed between AOD and average temperature in Solar Village and Dalanzadgad whereas rainfall and wind speed showed no significant impact on AOD in all desert regions.

Aerosol Optical Thickness over Large Urban Environments of the Arabian Peninsula—Speciation, Variability, and Distributions

“…The exception to this decreasing trend was in 2012 when high AOT was observed [3,6]. From 2015, there is an increasing trend in dust emissions due to shift back to La Nina, associated with a drier period in the Arabian Peninsula (Figures 6 and 7).…”

“…In 2009-2010, the onset of the El Nino along with the shift in the PDO from negative to positive phase led to a decrease in dust generation which continued until 2015 [2]. The exception to this decreasing trend was in 2012 when high AOT was observed [3,6]. From 2015, there is an increasing trend in dust emissions due to shift back to La Nina, associated with a drier period in the Arabian Peninsula (Figures 6 and 7).…”

“…The aerosol robotic network (AERONET) includes a series of ground-based sky radiometers and sun photometers that measure aerosol optical properties [6]. It started in 1993 and has quickly grown to include over 300 sites around the world [32].…”

“…The AERONET sun photometers utilize 340-1020 nm and 440-1020 nm spectral ranges for direct sun and diffuse sky radiances, respectively. The AOT values from AERONET are with ±0.01 uncertainty for wavelength >440 nm and ±0.02 for shorter wavelengths [6]. AERONET algorithms have recently been upgraded to Version 3, with real-time quality screening for clouds, and a quicker processing of AOT data [34].…”

“…To maximize the observation coverage, AOT retrievals over land and sea are derived from the dark target algorithm [36] and the deep blue algorithm (measurements over bright surfaces such as deserts and urban areas), respectively. Over land, the MODIS uncertainty in AOT is 0.05 ± 0.15 [6].…”