# Area-Averaged Surface Moisture Flux over Fragmented Sea Ice: Floe Size Distribution Effects and the Associated Convection Structure within the Atmospheric Boundary Layer

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Methods

#### 2.1. Configuration of the WRF Model

#### 2.2. Calculation of Spatial Coverage of Convective Structures

#### 2.3. Computation of Area-Averaged Surface Moisture Heat Flux

## 3. Results

#### 3.1. Horizontal and Vertical Structure of Convection

#### 3.2. Correction Coefficient for Surface Moisture Flux

## 4. Discussion

## Author Contributions

## Funding

## Conflicts of Interest

## Appendix A

Model Domain | Rectangular, periodic boundaries in both horizontal directions |

Horizontal resolution | 100 m |

Number of grid points | 200 × 200 |

Model top height | 2000 m |

Air column | 61 $\eta $-levels with exponential thickness distribution |

Physics Parametrizations | |

Microphysics | WRF Single-Moment 5-class scheme |

Longwave radiation | RRTMG Scheme |

Surface layer | Eta Similarity Scheme |

Land Layer | Noah Land Surface Model |

Large-eddy simulation | 1.5-order TKE scheme |

Sea Ice Options | |

Sea ice in a grid cell | Treats sea ice as fractional field. |

Maximum allowed snow accumulation on sea ice | 10${}^{10}$ m |

Minimum allowed accumulation of snow on sea ice | 0.001 m |

Default sea ice thickness | 1.5 m |

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**Figure 1.**An example gray scale image of upward air motion areas within the model area (

**a**) and a corresponding output from Pixie program where the upward air motion areas are marked in black (

**b**).

**Figure 2.**Wind speed (colors) and wind vectors (arrows) for simulations with $c=70\%$, ${N}_{f}=500$, with weak wind conditions (profile No. 1;

**a**) and stronger wind conditions (profile No. 3;

**b**).

**Figure 3.**Simulation with weak wind condition (zero initial wind), $c=80\%$ and ${N}_{f}=100$, crosswise transect of: vertical velocity component of the air motion (m/s;

**a**), water vapor mixing ratio (kg/kg;

**b**), and atmospheric pressure (hPa;

**c**).

**Figure 4.**Time-mean total area of convective updrafts (km${}^{2}$;

**a**), time-mean height reached by a convective plume (m;

**b**), total liquid water content (kg/kg;

**c**) and area–averaged sensible heat flux (W/m${}^{2}$,

**d**) in function of the number of floes ${N}_{f}$, in simulations with $c=90\%$, weak wind conditions (ambient wind speed 2 m/s).

**Figure 5.**Values of the $\alpha $ coefficient for every WRF model simulation with different ambient wind speed ${U}_{m}$ and median floe size r, plotted for all sea ice concentrations considered in the analysis (

**a**–

**f**).

**Figure 6.**Left (

**a**–

**c**): values of $\alpha $ computed from Equation (9) (plotted surfaces) and obtained from WRF simulations (dots) for $c=60\%$ (

**a**), 70% (

**b**) and 80% (

**c**). Right (

**d**–

**f**): the accuracy of each fit represented by the difference between the original and fitted values.

**Table 1.**Statistics describing the goodness of fit of Equation (9).

c | RMSE | CC |
---|---|---|

50% | 0.29 | 0.98 |

60% | 0.05 | 0.99 |

70% | 0.11 | 0.99 |

80% | 0.07 | 0.99 |

85% | 0.17 | 0.99 |

90% | 0.18 | 0.99 |

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**MDPI and ACS Style**

Wenta, M.; Herman, A. Area-Averaged Surface Moisture Flux over Fragmented Sea Ice: Floe Size Distribution Effects and the Associated Convection Structure within the Atmospheric Boundary Layer. *Atmosphere* **2019**, *10*, 654.
https://doi.org/10.3390/atmos10110654

**AMA Style**

Wenta M, Herman A. Area-Averaged Surface Moisture Flux over Fragmented Sea Ice: Floe Size Distribution Effects and the Associated Convection Structure within the Atmospheric Boundary Layer. *Atmosphere*. 2019; 10(11):654.
https://doi.org/10.3390/atmos10110654

**Chicago/Turabian Style**

Wenta, Marta, and Agnieszka Herman. 2019. "Area-Averaged Surface Moisture Flux over Fragmented Sea Ice: Floe Size Distribution Effects and the Associated Convection Structure within the Atmospheric Boundary Layer" *Atmosphere* 10, no. 11: 654.
https://doi.org/10.3390/atmos10110654