February 15, 2019 Journal article Open Access

Ove Hermansen; C. A. Pedersen; Masataka Shiobara; Angelo Lupi; Vito Vitale; Jinro Ukita; Johan Ström; Peter Tunved; Christoph Ritter; Darrel Baumgardner; Makoto Koike; K. Yamada

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{
  "DOI": "10.1029/2018jd029802", 
  "abstract": "AbstractTwo years of continuous in situ measurements of Arctic low\u2010level clouds have been made at the Mount Zeppelin Observatory (78\u00b056\u2032N, 11\u00b053\u2032E), in Ny\u2010\u00c5lesund, Spitsbergen. The monthly median value of the cloud particle number concentration (Nc) showed a clear seasonal variation: Its maximum appeared in May\u2013July (65\u00a0\u00b1\u00a08\u00a0cm\u22123), and it remained low between October and March (8\u00a0\u00b1\u00a07\u00a0cm\u22123). At temperatures warmer than 0\u00a0\u00b0C, a clear correlation was found between the hourly Nc values and the number concentrations of aerosols with dry diameters larger than 70\u00a0nm (N70), which are proxies for cloud condensation nuclei (CCN). When clouds were detected at temperatures colder than 0\u00a0\u00b0C, some of the data followed the summertime Nc to N70 relationship, while other data showed systematically lower Nc values. The lidar\u2010derived depolarization ratios suggested that the former (CCN\u2010controlled) and latter (CCN\u2010uncontrolled) data generally corresponded to clouds consisting of supercooled water droplets and those containing ice particles, respectively. The CCN\u2010controlled data persistently appeared throughout the year at Zeppelin. The aerosol\u2010cloud interaction index (ACI\u00a0=\u00a0dlnNc/(3dlnN70)) for the CCN\u2010controlled data showed high sensitivities to aerosols both in the summer (clean air) and winter\u2013spring (Arctic haze) seasons (0.22\u00a0\u00b1\u00a00.03 and 0.25\u00a0\u00b1\u00a00.02, respectively). The air parcel model calculations generally reproduced these values. The threshold diameters of aerosol activation (Dact), which account for the Nc of the CCN\u2010controlled data, were as low as 30\u201350\u00a0nm when N70 was less than 30\u00a0cm\u22123, suggesting that new particle formation can affect Arctic cloud microphysics.", 
  "author": [
    {
      "family": "Ove Hermansen"
    }, 
    {
      "family": "C. A. Pedersen"
    }, 
    {
      "family": "Masataka Shiobara"
    }, 
    {
      "family": "Angelo Lupi"
    }, 
    {
      "family": "Vito Vitale"
    }, 
    {
      "family": "Jinro Ukita"
    }, 
    {
      "family": "Johan Str\u00f6m"
    }, 
    {
      "family": "Peter Tunved"
    }, 
    {
      "family": "Christoph Ritter"
    }, 
    {
      "family": "Darrel Baumgardner"
    }, 
    {
      "family": "Makoto Koike"
    }, 
    {
      "family": "K. Yamada"
    }
  ], 
  "id": "91947", 
  "issued": {
    "date-parts": [
      [
        2019, 
        2, 
        15
      ]
    ]
  }, 
  "language": "eng", 
  "note": "", 
  "title": "Year\u2010Round In Situ Measurements of Arctic Low\u2010Level Clouds: Microphysical Properties and Their Relationships With Aerosols", 
  "type": "article-journal"
}