Does the Madden‐Julian Oscillation influence aerosol variability?

Abstract

[1] We investigate the modulation of aerosols by the Madden-Julian Oscillation (MJO) using multiple, global satellite aerosol products: aerosol index (AI) from the Total Ozone Mapping Spectrometer (TOMS) on Nimbus-7, and aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Advanced Very High Resolution Radiometer (AVHRR) on NOAA satellites. A composite MJO analysis indicates that large variations in the TOMS AI and MODIS/AVHRR AOT are found over the equatorial Indian and western Pacific Oceans where MJO convection is active, as well as the tropical Africa and Atlantic Ocean where MJO convection is weak but the background aerosol level is high. A strong inverse linear relationship between the TOMS AI and rainfall anomalies, but a weaker, less coherent positive correlation between the MODIS/AVHRR AOT and rainfall anomalies, were found. The MODIS/AVHRR pattern is consistent with ground-based Aerosol Robotic Network data. These results indicate that the MJO and its associated cloudiness, rainfall, and circulation variability systematically influence the variability in remote sensing aerosol retrieval results. Several physical and retrieval algorithmic factors that may contribute to the observed aerosol-rainfall relationships are discussed. Preliminary analysis indicates that cloud contamination in the aerosol retrievals is likely to be a major contributor to the observed relationships, although we cannot exclude possible contributions from other physical mechanisms. Future research is needed to fully understand these complex aerosol-rainfall relationships.

Observing and understanding the Southeast Asian aerosol system by remote sensing: An initial review and analysis for the Seven Southeast Asian Studies (7SEAS) program

“…14(a) and (b). For example, the direct application of OMI retrievals to SEA has met with significant difficulty (Tian et al, 2008). Average seasonal optical depths (Fig.…”

“…Subsidence, and consequently negative precipitation anomalies, leads and lags this convective region, with the more dominant subsidence being observed on the eastern side when the convective region is in the Indian Ocean, and on the western side when the convective region is in the Pacific. Thus, from an aerosol point of view, the wet and dry phases of the MJO largely dictate the timing of significant smoke events in the MC (Reid et al, 2012), and the MJO was hypothesized to influence overall AOD (Tian et al, 2008). The amplitude of the MJO is the strongest in boreal winter and early boreal spring with a secondary maximum in boreal summer (Zhang and Dong, 2004).…”

“…This is particularly true in SEA with its very high cloud cover and ubiquitous thin cirrus. Indeed, Tian et al (2008) had great difficulty separating aerosol signals from cloud contamination in the MC. Sub-visual TTL cirrus contamination may even be uncorrectable or even detectable except at the broadest scales.…”

Observations of the temporal variability in aerosol properties and their relationships to meteorology in the summer monsoonal South China Sea/East Sea: the scale-dependent role of monsoonal flows, the Madden–Julian Oscillation, tropical cyclones, squall lines and cold pools

“…From an aerosol point of view, while ENSO is an excellent large-scale indicator of seasonal burning, the wet and dry phases of the MJO strongly influence the intraseasonal timing of significant smoke events in the MC (Reid et al, 2012). While the MJO was hypothesized to influence overall AOT (Tian et al, 2008), no satellite-based AOT verification of this has yet been established due to the difficulty in performing aerosol remote sensing in the region (Reid et al, 2013). However, fire observations are strongly enhanced in dry phases (Reid et al, 2012) and mechanistically a relationship between dry MJO phase, fire emissions, and high AOT seems certain.…”

Satellite perspective of aerosol intercontinental transport: From qualitative tracking to quantitative characterization

“…An analysis of aerosol observations from TOMS, AVHRR, and MODIS looked for intra-seasonal variations in AOD over the tropical Pacific and Indian oceans, with inconclusive results due to difficulties in interpreting the satellite products in these regions, namely possible cloud contamination or other ambiguities contributing to the observed patterns (Tian et al, 2008). However, a follow-up study applied the same technique over the tropical Atlantic, and showed that about 25% of the total variance of MODIS AOD can be accounted for by the intra-seasonal variability related to the Madden-Julian Oscillation (MJO) (Tian et al, 2011).…”