Dust accumulation biases in PIRATA shortwave radiation records

TitleDust accumulation biases in PIRATA shortwave radiation records
Publication TypeJournal Article
Year of Publication2013
AuthorsFoltz G.R, Evan AT, Freitag H.P, Brown S., McPhaden MJ
JournalJournal of Atmospheric and Oceanic Technology
Date Published2013/07
Type of ArticleArticle
ISBN Number0739-0572
Accession NumberWOS:000322126100011
Keywordsaerosols; algorithm; atlantic-ocean; Buoy observations; Climate records; data; distributions; fluxes; In situ atmospheric observations; north-atlantic; products; quality control; Shortwave radiation; subduction experiment; surface; transfer model

Long-term and direct measurements of surface shortwave radiation (SWR) have been recorded by the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) since 1997. Previous studies have shown that African dust, transported westward from the Sahara and Sahel regions, can accumulate on mooring SWR sensors in the high-dust region of the North Atlantic (8 degrees-25 degrees N, 20 degrees-50 degrees W), potentially leading to significant negative SWR biases. Here dust-accumulation biases are quantified for each PIRATA mooring using direct measurements from the moorings, combined with satellite and reanalysis datasets and statistical models. The SWR records from five locations in the high-dust region (8 degrees, 12 degrees, and 15 degrees N along 38 degrees W; 12 degrees and 21 degrees N along 23 degrees W) are found to contain monthly-mean accumulation biases as large as -200 W m(-2) and record-length mean biases on the order of -10 W m(-2). The other 12 moorings, located mainly between 10 degrees S and 4 degrees N, are in regions of lower atmospheric dust concentration and do not show statistically significant biases. Seasonal-to-interannual variability of the accumulation bias is found at all locations in the high-dust region. The moorings along 38 degrees W also show decreasing trends in the bias magnitude since 1998 that are possibly related to a corresponding negative trend in atmospheric dust concentration. The dust-accumulation biases described here will be useful for interpreting SWR data from PIRATA moorings in the high-dust region. The biases are also potentially useful for quantifying dust deposition rates in the tropical North Atlantic, which at present are poorly constrained by satellite data and numerical models.

Short TitleJ. Atmos. Ocean. Technol.