Commit 60a0f5620e5d1815e5d287350d29fc7930508077

Authored by Arthanor
1 parent 4c9a79ea
Exists in icenotes

Ice Modeling notes after break

Showing 1 changed file with 79 additions and 4 deletions   Show diff stats
README.md
... ... @@ -71,16 +71,91 @@ but Ungermann 2017 have better results using Hibler....
71 71 Redistribution to prevent concentrations to go >1 by advection.
72 72  
73 73 ##### Calculation of vertical growth/melt
74   -- Melt on top depending on radiation + air heat flux
  74 +- Melt on top depending on radiation + air heat flux. If calculated T_s > 0, keep it at 0 and use the heat to melt ice.
75 75 - Growth or melt at the bottom depending on heat flux differences and ice heat capacity.
76 76  
  77 +Solve the vertical heat diffusion equation to get temperatures. Need conductivity
  78 +
  79 +Snow and ice are very good insulator. 30cm snow is enough to slow ice growth to thick (~2m) ice rates for thin ice.
  80 +
  81 +Most of the salt is rejected during ice formation. -> Drive convective mixing
  82 +Rest of it is in brine pockets, which affects heat properties so it should be represented, but it is usually prescribed instead.
  83 +
77 84 ### Numerical implementations
78 85  
  86 +Ice velocity and thickness are coupled nonlinear equations
  87 +
  88 +Use discretized equations to solve it. Ex.: CICE (B-Grid), LIM and MITGCM (C-Grid)
  89 +
  90 +Explicit: Solve for new velocity field using known values: \Delta t \leq \frac{m \Delta x^2}{2 \zeta}
  91 +--> time step of 0.01s for 10km resolution. Useless
  92 +
  93 +Implicit: Solve for new velocity field using unknown, new values. Solve big matrix-vectors system.
  94 +OR
  95 +Use EVP to add fake elastic waves and damp them out every time step. Can be noisy if residual elastic waves persist.
  96 +
  97 +#### Advection and the CFL condition
  98 +~1m/s velocity with 10km resolution: 167 min time step
  99 +BUT there can be a plastic wave propagating through solid ice at 25m/s which needs smaller time step to resolve, otherwise it blows up.
  100 +
  101 +Splitting in time by solving momentum and then advecting ice parameters. Would need to do both together.
  102 +IMEX approach to do both
  103 +
79 104 ### Recent model developments
80 105  
  106 +#### Drag representation
  107 +Replace skin drag with increased roughness with form drag and proper current drag for the thickness of ocean cells. (F. Roy 2015)
  108 +
  109 +#### Simulations of landfast ice
  110 +Pressure ridge grounding holds ice on the coast.
  111 +(See: Mahoney et al. 2007, Lemieux et al, 2015)
  112 +Landfast ice off Laptev sea from grounding of sea ice ridges
  113 +Landfast ice off ?? sea from tensile strength
  114 +Landfast ice off Greenland from grounding of icebergs
  115 +
  116 +#### Wave-ice interactions
  117 +(See Dumon et al., JGR, 2011)
  118 +g(h) thickness distribution says nothing about floes
  119 +j(h,D) is the distribution of thickness and "diameter of floes"
  120 +
  121 +#### Salt in ice
  122 +(See Vancopenolle et al, 2009)
  123 +
  124 +#### Albedo of ice and melt ponds
  125 +(See Flocco et al, 2010 and Hunke et al, 2013)
  126 +
81 127 ### Sea ice models in short-term and subseasonal forecasting
  128 +Important for:
  129 +- Navigation:
  130 + - ice conditions
  131 + - ice pressure
  132 +- Emergency response:
  133 + - SAR
  134 + - Oil spills
  135 +- Planning of human activities
  136 +- Weather forecasting:
  137 + - Traditionally use a static ice cover
  138 + - Coupled forecasting: Atm-Ocn, Ice-Ocn, soon global Atm-Ice-Ocn, already have GSL
  139 +
  140 +#### EC3:
  141 +- GIOPS (Global Ice Ocean Prediction System): ~15km resolution in the Arctic
  142 +- RIOPS (Regional Ice Ocean Prediction System): ~2-8km resolution in the Arctic
  143 +- ENGIOPS (ENsemble GIOPS): 21 models
  144 +Only have a concentration analysis, no thickness but working on it.
82 145  
83 146 ### Verification methods
84   -- Short term forecast, you can assess shortly, not wait
85   -
86   -Hunke et al., 2010 for a good review of sea ice modeling
87 147 \ No newline at end of file
  148 +- Short term forecast, you can assess shortly, no wait
  149 +- Forecast vs Persistence
  150 +Challenging in the melting season because initialization has difficulty distinguishing melt ponds and open water.
  151 +Point by point metrics are often unreliable
  152 +- overly penalize high resolution
  153 +- sensitive to double penalty
  154 +
  155 +### Modeling challenges for sea ice
  156 +- Ice parameterizations: ridging scheme, ice strength, rheology
  157 +- Better representation of MIZ processes
  158 +- Is the problem well formulated as resolution increases?
  159 +- Numerical issues and coupled framework
  160 +
  161 +Hunke et al., 2010 for a good review of sea ice modeling
  162 +NSIDC data for comparison
88 163 \ No newline at end of file
... ...