The Midlatitude Continental Convective Clouds Experiment (MC3E) sounding network: operations, processing and analysis

The Midlatitude Continental Convective Clouds Experiment (MC3E) took place during the spring of 2011 centered in north-central Oklahoma, USA. The main goal of this field campaign was to capture the dynamical and microphysical characteristics of precipitating convective systems in the US Central Plains. A major component of the campaign was a six-site radiosonde array designed to capture the large-scale variability of the atmospheric state with the intent of deriving model forcing data sets. Over the course of the 46-day MC3E campaign, a total of 1362 radiosondes were launched from the enhanced sonde network. This manuscript provides details on the instrumentation used as part of the sounding array, the data processing activities including quality checks and humidity bias corrections and an analysis of the impacts of bias correction and algorithm assumptions on the determination of convective levels and indices. It is found that corrections for known radiosonde humidity biases and assumptions regarding the characteristics of the surface convective parcel result in significant differences in the derived values of convective levels and indices in many soundings. In addition, the impact of including the humidity corrections and quality controls on the thermodynamic profiles that are used in the derivation of a large-scale model forcing data set are investigated. The results show a significant impact on the derived large-scale vertical velocity field illustrating the importance of addressing these humidity biases

Long‐Term Trends for Marine Sulfur Aerosol in the Alaskan Arctic and Relationships With Temperature

Marine aerosol plays a vital role in cloud‐aerosol interactions during summer in the Arctic. The recent rise in temperature and decrease in sea ice extent have the potential to impact marine biogenic sources. Compounds like methanesulfonic acid (MSA) and non‐sea‐salt sulfate (nss‐SO42−), oxidation products of dimethyl sulfide (DMS) emitted by marine primary producers, are likely to increase in concentration. Long‐term studies are vital to understand these changes in marine sulfur aerosol and potential interactions with Arctic climate. Samples were collected over three summers at two coastal sites on the North Slope of Alaska (Utqiaġvik and Oliktok Point). MSA concentrations followed previously reported seasonal trends, with evidence of high marine primary productivity influencing both sites. When added to an additional data set collected at Utqiaġvik, an increase in MSA concentration of  + 2.5% per year and an increase in nss‐SO42− of  + 2.1% per year are observed for the summer season over the 20‐year record (1998–2017). This study identifies ambient air temperature as a strong factor for MSA, likely related to a combination of interrelated factors including warmer sea surface temperature, reduced sea ice, and temperature‐dependent chemical reactions. Analysis of individual particles at Oliktok Point, within the North Slope of Alaska oil fields, showed evidence of condensation of MSA onto anthropogenic particles, highlighting the connection between marine and oil field emissions and secondary organic aerosol. This study shows the continued importance of understanding MSA in the Arctic while highlighting the need for further research into its seasonal relationship with organic carbon.Plain Language SummaryParticles in the Earth’s atmosphere play an important role in affecting the planet’s climate. Understanding the compounds that make up these aerosol particles is especially important in the Arctic where dramatic changes in temperature and sea ice extent are being observed. Aerosol resulting from biological activity in marine regions is expected to increase in concentration and therefore have greater effects on climate. Methanesulfonic acid is one such compound that can be utilized to understand the impact of marine aerosol sources. Aerosol samples were collected over three summers at two sites on the North Slope of Alaska: Utqiaġvik and Oliktok Point. The samples were analyzed for a wide range of compounds including methanesulfonic acid. The results were combined with 16 years of data from the National Oceanic and Atmospheric Administration. Concentrations of methanesulfonic acid are increasing at a rate of 2.5% per year. Methanesulfonic acid was strongly related to temperature at Oliktok Point, where most marine aerosol is from the Beaufort Sea. At Utqiaġvik, strong relationships were found between methanesulfonic acid and temperature during years when intense Arctic cyclones occurred.Key PointsArctic MSA and non‐sea‐salt sulfate concentrations show increasing summer trends over the past two decades (2.5% and 2.1%) at Utqiaġvik, AKConcentrations of MSA at Oliktok Point are highly correlated to temperature as air masses are consistently from the Beaufort SeaSummers with Arctic cyclones have better correlation of MSA with ambient temperaturePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163570/2/jgrd56582.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163570/1/jgrd56582_am.pd