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					       FRUGAL CMIP summary
           – April 2007
• Spin-up of base model for 4000 years
  (completed)
• Control run of 140 years (completed)
• Transient, 1% CO2 increase (completed)
• Mixed forcing runs – both freshwater and
  radiation forcing completed
• Hosing runs – both 0.1 and 1.0 Sv
  completed
Still to do
• Conversion programme for writing meaned
  output as netcdf – Kevin Marsh at RAL
  writing code
• Analysis
            Meridional Overturning

• CONTROL




• Robust to year 100; restarts every 1000
  years
• Changes to mean and annual cycle occur
  rapidly
                       Meridional Overturning
• 12 month running mean
                  35

                  30


                  25                    Control
                                        Transient
       MOC (Sv)




                  20
                                        Crad_th2o
                                        Trad_ch2o
                  15
                                        Hosep1

                  10                    Hosec1


                  5


                  0
                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5

                       .5
                     00

                     10

                     20

                     30

                     40

                     50

                     60

                     70

                     80

                     90

                     00

                     10

                     20

                     30
                  30

                  30

                  30

                  30

                  30

                  30

                  30

                  30

                  30

                  30

                  31

                  31

                  31

                  31
                             Year
                                    Meridional Circulation
• Annual Cycle magnitude
                               10

                               9

                               8
       MOC annual range (Sv)




                               7                     Control
                               6                     Transient
                                                     Crad_th2o
                               5
                                                     Trad_ch2o
                               4                     Hosep1
                               3                     Hosec1

                               2

                               1

                               0
                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5

                                    .5
                                  00

                                  10

                                  20

                                  30

                                  40

                                  50

                                  60

                                  70

                                  80

                                  90

                                  00

                                  10

                                  20

                                  30
                               30

                               30

                               30

                               30

                               30

                               30

                               30

                               30

                               30

                               30

                               31

                               31

                               31

                               31
                                          Year




• Transient undergoes step change > 100 yrs
• Slowing MOC leads to weaker annual cycle
            52.5oN Atlantic Meridional
            Heat Flux
• Control
                                     52.5oN Atlantic Meridional
                                     Heat Flux
• 12 month running mean
                               0.5

                              0.45

                               0.4
     52.5N Atlantic HF (PW)




                              0.35                     Control
                               0.3                     Transient
                                                       Crad_th2o
                              0.25
                                                       Trad_ch2o
                               0.2                     Hosep1
                              0.15                     Hosec1

                               0.1

                              0.05

                                0
                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5

                                   .5
                                 00

                                 10

                                 20

                                 30

                                 40

                                 50

                                 60

                                 70

                                 80

                                 90

                                 00

                                 10

                                 20

                                 30
                              30

                              30

                              30

                              30

                              30

                              30

                              30

                              30

                              30

                              30

                              31

                              31

                              31

                              31            Year
                                                       52.5N Atlantic Meridional
                                                       Heat Flux
                                        0.16

                                        0.14
      Atlantic HF (annual range - PW)



                                        0.12
                                                                                                                                                                                    Control
                                         0.1                                                                                                                                        Transient
                                                                                                                                                                                    Crad_th2o
                                        0.08
                                                                                                                                                                                    Trad_ch2o
                                        0.06                                                                                                                                        Hosep1
                                                                                                                                                                                    Hosec1
                                        0.04

                                        0.02

                                          0
                                               3001
                                                      3008
                                                             3016
                                                                    3023
                                                                           3031
                                                                                  3038
                                                                                         3046
                                                                                                3053
                                                                                                       3061
                                                                                                              3068
                                                                                                                     3076
                                                                                                                            3083
                                                                                                                                   3091
                                                                                                                                          3098
                                                                                                                                                 3106
                                                                                                                                                        3113
                                                                                                                                                               3121
                                                                                                                                                                      3128
                                                                                                                                                                             3136
                                                                                                              Year




• Only mixed experiments lead to higher HF
  range
            Links between density
            & MOC
• What are the starting conditions?
    January SST         January Surface Density
          Links between density
          & MOC -SST
Control               Transient




 Hosep1               Hosec1
          Links between density &
          MOC – surface density
Control                Transient




                          Hosec1
Hosep1
           The state of play …
• All runs complete
• Meaning fields to be made accessible
• Basic FRUGAL run strong due to northern
  convection
• Transient run sees more Atlantic input to
  Arctic, increasing the density gradient off
  western Europe
• Hosing runs see lessening (hosep1) or
  removal of density gradient (hosec1)
                          The Grid
• Use curvilinear coordinates to maximise resolution in key
  area
• Standard grid translates North Pole to central Greenland
                        Resolution
• Resolution is flexible but two standard ones used
• Climate mode




                      Zonal                 Meridional
• Decadal mode
                            Numerics
• To overcome numerical stability problems
  use variable timestepping




     Shading shows size of timesteps used in different regions
           Darker shading – shorter steps (x8 longest)
• Atmosphere – Weaver energy balance model
• Moisture advection, mountains, clouds, land hydrology, river
  run-off, land-ice


• Ocean – normally has 19 levels
• Isopycnal mixing (Griffies et al., 1998)
• Sea-ice model with thermodynamics (Semtner, 1976) and
  dynamics (advection by surface current)
• free surface as Webb (1996)
• Oxygen isotopes
• tracers
• Fine resolution uses Philander & Pacanowski upper ocean
  mixing

				
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