A global database of sea surface dimethylsulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month

47 pages, 13 figures, 7 tablesA database of 15,617 point measurements of dimethylsulfide (DMS) in surface waters along with lesser amounts of data for aqueous and particulate dimethylsulfoniopropionate concentration, chlorophyll concentration, sea surface salinity and temperature, and wind speed has been assembled. The database was processed to create a series of climatological annual and monthly 1°x1°latitude-longitude squares of data. The results were compared to published fields of geophysical and biological parameters. No significant correlation was found between DMS and these parameters, and no simple algorithm could be found to create monthly fields of sea surface DMS concentration based on these parameters. Instead, an annual map of sea surface DMS was produced using an algorithm similar to that employed by Conkright et al. [1994]. In this approach, a first-guess field of DMS sea surface concentration measurements is created and then a correction to this field is generated based on actual measurements. Monthly sea surface grids of DMS were obtained using a similar scheme, but the sparsity of DMS measurements made the method difficult to implement. A scheme was used which projected actual data into months of the year where no data were otherwise presen

Measurements of Carbonyl Sulfide (COS) in Surface Seawater and Marine Air, and Estimates of the Air-Sea Flux from Observations During two Atlantic Cruises

Messungen des Carbonylsulfid-(COS)-Gehaltes im Oberflächenwasser und in angrenzender Luftschicht des Meeres wurden auf zwei Fahrten mit dem Forschungsschiff RV Polarstern zwischen Bremerhaven, Deutschland und Kapstadt, Südafrika im Herbst 1997 und im Sommer 1998 vorgenommen. Sowohl die COS-Konzentrationen als auch das Sättigungsverhältnis zeigen einen deutlichen Tagesgang, jahreszeitliche Variation und Abhängigkeit von der geografischen Breite. Im Mittel betrugen die Konzentrationen des gelösten COS 14.7 pmol/L im Herbst und 18.1 pmol/L im Sommer. An den meisten Tagen war das Seewasser mit COS während der Nacht bis in die frühen Morgenstunden untersättigt und während der übrigen Tageszeit übersättigt, sodaß der Ozean im Tagesverlauf sowohl als Quelle als auch als Senke des COS wirken kann. Der COS Gehalt im Seewasser korrelierte signifikant mit der Globalstrahlung, der CH3SH-Konzentration und der Seewassertemperatur. Die Abschätzung des COS-Flusses vom Meer in die Atmosphäre mit Hilfe von Austauschkoeffizienten, die aus dem stabilitätsabhängigen Modell von Erickson für den Meer-Luft-Gasaustausch berechnet wurden, ergaben, daß der größte COS Fluß in die Atmosphäre in den Gebieten mit COS-Produktion (Benguela-Strom, Westafrikanisches Aufquellgebiet und Nordöstlicher Atlantik) während der wärmeren Jahreszeiten auftrat. Eine geringe Nettoaufnahme von COS durch den Ozean wurde im Bereich des Benguela-Stroms während des Winters auf der Südhalbkugel gefunden. Die durchschnittliche COS-Flußdichte des offenen Ozeans betrug jeweils 13.5 nmol COS/(m^2 d) und 28.6 nmol COS/(m^2 d) auf den beiden Fahrten. Aus den gemessenen Daten kann eine Quellstärke des offenen Ozeans von 0.10 Tg COS/Jahr extrapoliert werden. Das durchschnittliche atmosphärische Mischungsverhältnis betrug 474+/-33 pptv während der Herbstfahrt und 502+/-38 pptv während der Sommerfahrt und wies keinen signifikanten interhemisphärischen Gradienten auf

Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 1: Immersion freezing

Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies over several decades. Recently some feldspar species were identified to be ice active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase. For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands, and the Sinai Peninsula). Additionally, 11 dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore, we investigated how representative surface-collected dust is for the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC setup to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233 and 250K. Dust particles were collected in parallel on filters for offline cold-stage ice nucleation experiments at 253–263K. To help the interpretation of the ice nucleation experiments the mineralogical composition of the dusts was investigated. We find that a higher ice nucleation activity in a given sample at 253K can be attributed to the K-feldspar content present in this sample, whereas at temperatures between 238 and 245K it is attributed to the sum of feldspar and quartz content present. A high clay content, in contrast, is associated with lower ice nucleation activity. This confirms the importance of feldspar above 250K and the role of quartz and feldspars determining the ice nucleation activities at lower temperatures as found by earlier studies for monomineral dusts. The airborne samples show on average a lower ice nucleation activity than the surface-collected ones. Furthermore, we find that under certain conditions milling can lead to a decrease in the ice nucleation ability of polymineral samples due to the different hardness and cleavage of individual mineral phases causing an increase of minerals with low ice nucleation ability in the atmospherically relevant size fraction. Comparison of our data set to an existing desert dust parameterization confirms its applicability for climate models. Our results suggest that for an improved prediction of the ice nucleation ability of desert dust in the atmosphere, the modeling of emission and atmospheric transport of the feldspar and quartz mineral phases would be key, while other minerals are only of minor importance.ISSN:1680-7375ISSN:1680-736

Long-term ice nucleating particle concentrations by offline vacuum diffusion chamber measurements from the Amazon, the Caribbean, Central Europe, and the Norwegian Arctic, data for figures 1-10

The data set reports on long-term measurements of ice nucleating particles (INPs) from four observational sites: 1. Amazon Tall Tower Observatory (ATTO, 2.144° S, 59.000° W, 130 m AMSL, Brazil), 2. Volcanological and Seismological Observatory of Martinique (OVSM, 14.735° N, 61.147° W, 487 m AMSL, Martinique, Caribbean), 3. Taunus Observatory (TO, 50.221° N, 8.446° E, 825 m AMSL, Germany) and 4. Zeppelin Observatory (ZO, 78.908° N, 11.881° E, 474 m AMSL, Ny-Alesund, Svalbard, Arctic). The presented data covers data from May 2015 to January 2017. Samples were usually collected every day or every two days at local noon for 50 minutes at 2 L min-1, resulting in 100 L of air volume. After transport samples were analyzed in our laboratory in Frankfurt using the vacuum diffusion chamber FRIDGE. Each sample was analyzed at multiple combinations of temperature ( 20 °C, -25 °C, and -30 °C) and relative humidity (95%, 97%, 99%, 101% w.r.t. water). INP concentrations per liter are reported for each condition (the paper focuses on the highest humidity). This data supplement is related to a scientific publication (doi:10.5194/acp-2020-667)

Long-term ice nucleating particle concentrations by offline vacuum diffusion chamber measurements from the Amazon, the Caribbean, Central Europe, and the Norwegian Arctic

The data set reports on long-term measurements of ice nucleating particles (INPs) from four observational sites: 1. Amazon Tall Tower Observatory (ATTO, 2.144° S, 59.000° W, 130 m AMSL, Brazil), 2. Volcanological and Seismological Observatory of Martinique (OVSM, 14.735° N, 61.147° W, 487 m AMSL, Martinique, Caribbean), 3. Taunus Observatory (TO, 50.221° N, 8.446° E, 825 m AMSL, Germany) and 4. Zeppelin Observatory (ZO, 78.908° N, 11.881° E, 474 m AMSL, Ny-Alesund, Svalbard, Arctic). The presented data covers data from May 2015 to January 2017. Samples were usually collected every day or every two days at local noon for 50 minutes at 2 L min-1, resulting in 100 L of air volume. After transport samples were analyzed in our laboratory in Frankfurt using the vacuum diffusion chamber FRIDGE. Each sample was analyzed at multiple combinations of temperature ( 20 °C, -25 °C, and -30 °C) and relative humidity (95%, 97%, 99%, 101% w.r.t. water). INP concentrations per liter are reported for each condition (the paper focuses on the highest humidity). This data supplement is related to a scientific publication (doi:10.5194/acp-2020-667)

Ice nucleating particle concentrations by droplet freezing assay measurements from the B17 ice core, Greenland, dating from 1370 to 1990

The data set reports on measurements of ice nucleating particles (INPs) from an ice core in Greenland (B17, 72.25, -37.25, 2820 m AMSL) that dates back to about 1370. INP measurements were performed using the FRIDGE INP counter as a droplet freezing assay for N = 135 meltwater samples from the core. From each sample 3 x 65 droplets of melt water (2.5 µL) were pipetted onto a sample substrate. The experimental nucleation temperature T was decreased at 1 °C/min until every droplet was frozen. The frozen fraction (FF) as a function of T is used to calculate the INP abundance per mL of melt water. A conversion factor is used to estimate atmospheric INP concentrations. The typical time coverage of a sampe is in the order of a couple of months. Samples were selected in regular time intervals of 10 years, plus a number of additional samples. This data supplement is related to a scientific publication (doi:10.5194/acp-2020-556)