Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean
This study uses large eddy simulations to test the sensitivity of single-layer mixed-phase stratocumulus to primary ice number concentrations in the European Arctic. Observations from the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are considered for comparison w...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/4209/2017/acp-17-4209-2017.pdf |
| _version_ | 1819211454230822912 |
|---|---|
| author | G. Young P. J. Connolly H. M. Jones T. W. Choularton |
| author_facet | G. Young P. J. Connolly H. M. Jones T. W. Choularton |
| author_sort | G. Young |
| collection | DOAJ |
| description | This study uses large eddy simulations to test the sensitivity of
single-layer mixed-phase stratocumulus to primary ice number concentrations
in the European Arctic. Observations from the Aerosol-Cloud Coupling and
Climate Interactions in the Arctic (ACCACIA) campaign are considered for
comparison with cloud microphysics modelled using the Large Eddy Model (LEM,
UK Met. Office). We find that cloud structure is very sensitive to ice number
concentrations, <i>N</i><sub>ice</sub>, and small increases can cause persisting
mixed-phase clouds to glaciate and break up.<br><br>Three key dependencies on <i>N</i><sub>ice</sub> are identified from sensitivity
simulations and comparisons with observations made over the sea ice pack,
marginal ice zone (MIZ), and ocean. Over sea ice, we find
deposition–condensation ice formation rates are overestimated, leading to
cloud glaciation. When ice formation is limited to water-saturated
conditions, we find microphysics comparable to aircraft observations over all
surfaces considered. We show that warm supercooled (−13 °C)
mixed-phase clouds over the MIZ are simulated to reasonable accuracy when
using both the DeMott et al.(2010) and Cooper(1986) primary
ice nucleation parameterisations. Over the ocean, we find a strong
sensitivity of Arctic stratus to <i>N</i><sub>ice</sub>. The
Cooper(1986) parameterisation performs poorly at the lower
ambient temperatures, leading to a comparatively higher <i>N</i><sub>ice</sub>
(2.43 L<sup>−1</sup> at the cloud-top temperature, approximately −20 °C)
and cloud glaciation. A small decrease in the predicted <i>N</i><sub>ice</sub>
(2.07 L<sup>−1</sup> at −20 °C), using the DeMott et al.(2010)
parameterisation, causes mixed-phase conditions to persist for 24 h over the
ocean. However, this representation leads to the formation of convective
structures which reduce the cloud liquid water through snow precipitation,
promoting cloud break-up through a depleted liquid phase. Decreasing the
<i>N</i><sub>ice</sub> further (0.54 L<sup>−1</sup>, using a relationship derived from
ACCACIA observations) allows mixed-phase conditions to be maintained for at
least 24 h with more stability in the liquid and ice water paths.
Sensitivity to <i>N</i><sub>ice</sub> is also evident at low number
concentrations, where 0.1 × <i>N</i><sub>ice</sub> predicted by the
DeMott et al.(2010) parameterisation results in the formation of rainbands
within the model; rainbands which also act to deplete the liquid water in the
cloud and promote break-up. |
| first_indexed | 2024-12-23T06:27:19Z |
| format | Article |
| id | doaj.art-0ed32faf77ae4687be15aba7e8e5c911 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-23T06:27:19Z |
| publishDate | 2017-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-0ed32faf77ae4687be15aba7e8e5c9112022-12-21T17:57:01ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-03-011764209422710.5194/acp-17-4209-2017Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and oceanG. Young0P. J. Connolly1H. M. Jones2T. W. Choularton3Centre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, UKCentre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, UKCentre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, UKCentre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, UKThis study uses large eddy simulations to test the sensitivity of single-layer mixed-phase stratocumulus to primary ice number concentrations in the European Arctic. Observations from the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are considered for comparison with cloud microphysics modelled using the Large Eddy Model (LEM, UK Met. Office). We find that cloud structure is very sensitive to ice number concentrations, <i>N</i><sub>ice</sub>, and small increases can cause persisting mixed-phase clouds to glaciate and break up.<br><br>Three key dependencies on <i>N</i><sub>ice</sub> are identified from sensitivity simulations and comparisons with observations made over the sea ice pack, marginal ice zone (MIZ), and ocean. Over sea ice, we find deposition–condensation ice formation rates are overestimated, leading to cloud glaciation. When ice formation is limited to water-saturated conditions, we find microphysics comparable to aircraft observations over all surfaces considered. We show that warm supercooled (−13 °C) mixed-phase clouds over the MIZ are simulated to reasonable accuracy when using both the DeMott et al.(2010) and Cooper(1986) primary ice nucleation parameterisations. Over the ocean, we find a strong sensitivity of Arctic stratus to <i>N</i><sub>ice</sub>. The Cooper(1986) parameterisation performs poorly at the lower ambient temperatures, leading to a comparatively higher <i>N</i><sub>ice</sub> (2.43 L<sup>−1</sup> at the cloud-top temperature, approximately −20 °C) and cloud glaciation. A small decrease in the predicted <i>N</i><sub>ice</sub> (2.07 L<sup>−1</sup> at −20 °C), using the DeMott et al.(2010) parameterisation, causes mixed-phase conditions to persist for 24 h over the ocean. However, this representation leads to the formation of convective structures which reduce the cloud liquid water through snow precipitation, promoting cloud break-up through a depleted liquid phase. Decreasing the <i>N</i><sub>ice</sub> further (0.54 L<sup>−1</sup>, using a relationship derived from ACCACIA observations) allows mixed-phase conditions to be maintained for at least 24 h with more stability in the liquid and ice water paths. Sensitivity to <i>N</i><sub>ice</sub> is also evident at low number concentrations, where 0.1 × <i>N</i><sub>ice</sub> predicted by the DeMott et al.(2010) parameterisation results in the formation of rainbands within the model; rainbands which also act to deplete the liquid water in the cloud and promote break-up.http://www.atmos-chem-phys.net/17/4209/2017/acp-17-4209-2017.pdf |
| spellingShingle | G. Young P. J. Connolly H. M. Jones T. W. Choularton Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean Atmospheric Chemistry and Physics |
| title | Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean |
| title_full | Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean |
| title_fullStr | Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean |
| title_full_unstemmed | Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean |
| title_short | Microphysical sensitivity of coupled springtime Arctic stratocumulus to modelled primary ice over the ice pack, marginal ice, and ocean |
| title_sort | microphysical sensitivity of coupled springtime arctic stratocumulus to modelled primary ice over the ice pack marginal ice and ocean |
| url | http://www.atmos-chem-phys.net/17/4209/2017/acp-17-4209-2017.pdf |
| work_keys_str_mv | AT gyoung microphysicalsensitivityofcoupledspringtimearcticstratocumulustomodelledprimaryiceovertheicepackmarginaliceandocean AT pjconnolly microphysicalsensitivityofcoupledspringtimearcticstratocumulustomodelledprimaryiceovertheicepackmarginaliceandocean AT hmjones microphysicalsensitivityofcoupledspringtimearcticstratocumulustomodelledprimaryiceovertheicepackmarginaliceandocean AT twchoularton microphysicalsensitivityofcoupledspringtimearcticstratocumulustomodelledprimaryiceovertheicepackmarginaliceandocean |