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					       Using the surface energy balance to
       understand the Antarctic stable boundary
       layer.
       Michael S. Town1, Von P. Walden2, and Stephen G. Warren1

       1University   of Washington, Seattle, WA USA
       2University   of Idaho, Moscow, ID USA




Session 5. Science using ground-based and satellite measurements
                                                                   1
AMOMWF 2007, Rome, Italy.
2
2m air temperature




                     3
                                                        energy transfer over South Pole

                      net radiation               latent heat



                  G = RN + HS + HL
                                                                  positive fluxes are
                                                                  directed downward
subsurface heat                  sensible heat




        pyranometer                                              u10, TS, T2, T2f
        pyrgeometer       RN                     HS, HL          Andreas (2002)




      G = S + S + L + L + HS + HL                                    pyrgeometer --> Tsfc
                                      G                             finite-volumes
                                                                    numerical heat transfer model
                                                                    Patankar (1982)
                                                                                               4
     monthly means:                      energy transfer over South Pole
     prior work




RN                                                                             HS


                  Large discrepancies in literature




G                                                                              HL

                                                                           5
                              energy transfer over South Pole
monthly means:                         G = RN + HS + HL
energy balance?



                  HS




                        Gfv




                   RN                    HL




                                                                6
                                        energy transfer over South Pole
monthly means:                                   G = RN + HS + HL
energy balance? no.                              G - RN = HS + HL


                            residual HS+HL (i.e. G-RN)
                      HS




                                  Gfv




                       RN                          HL




                                                                          7
                                        energy transfer over South Pole
monthly means:                                   G = RN + HS + HL
energy balance? no.                              G - RN = HS + HL


                            residual HS+HL (i.e. G-RN)
                      HS




                                  Gfv




                       RN                          HL




     HS magnitude is underestimated by MO theory                          8
     over South Pole, probably.
                                           energy transfer over South Pole
monthly means:                                      G = RN + HS + HL
energy balance? no.                                 G - RN = HS + HL


                               residual HS+HL (i.e. G-RN)
                        HS




                                     Gfv




                         RN                           HL




     HS is sensitive to skin-surface temperature                             9
     derivation (from LUF).
                           energy transfer over South Pole
stable boundary layer:               G = RN + HS + HL
solution?                            G - RN = HS + HL


                                         heating snow




            cooling snow

                  lapse             inversion




            heating snow




            cooling snow


                                                             10
                           energy transfer over South Pole
stable boundary layer:                G = RN + HS + HL
solution?                             G - RN = HS + HL


                                           heating snow




            cooling snow

                  lapse              inversion

                               from thermistors during 2001 (not LUF)

            heating snow




            cooling snow


                                                                        11
                                                energy transfer over South Pole
stable boundary layer:                                       G = RN + HS + HL
solution? maybe.                                             G - RN = HS + HL
       find emperical relationship between G-RN, Tinv, ws, ...

                                                                 heating snow




           cooling snow

                lapse                                       inversion




          heating snow




          cooling snow


                                                                                  12
short time scales:
subsurface temperatures       heat transfer in snow pack




                          model upper boundary condition




                                                           13
short time scales:
subsurface temperatures                     heat transfer in snow pack

        high variability in subsurface temperatures during winter




                                                                         14
short time scales:
subsurface heating rates                    heat transfer in snow pack

January Monthly MEAN G = 1 W m-2       large G on short time scales




                       large heating rates on short time scales




                                                                         15
       short time scales:
       subsurface heating rates               heat transfer in snow pack

                        larger heat fluxes during winter
Monthly                                                                    Monthly
MEAN                                                                        Mean
1 W m-2                                                                    -3 W m-2




Monthly                                                                    Monthly
 MEAN                                                                      MEAN
-1 W m-2                                                                   4 W m-2




                                                                             16
short time scales:
subsurface vapor pressures               heat transfer in snow pack

        subsurface vapor pressures higher during summer




                                                                      17
                                        energy transfer over South Pole
conclusions:                                         G = RN + HS + HL

No energy balance. HS is probably larger in the monthly
mean (by 10 W m-2) than predicted by MO theory.

May be possible to develop emperical relationship
for HS+HL.

No significant frost deposition at the South Pole.

Snow surface temperatures at the South Pole result
in interface heat fluxes of up to 20 W m-2 on daily
time scales.

Episodic sustained heating rates of greater than 10 K day-1
occur in the near-surface snow at South Pole.

Snow temperature gradients and heat fluxes important
for depth hoar formation and 18O (or D) fractionation.


                                                                          18
acknowledgements:
Ed Waddington of UW for help with the finite-volume
model.

Ells Dutton and Tom Mefford of NOAA-GMD, and the BSRN
for data and advice.

Shelley Knuth and Matt Lazzara at the AMRC for data.

Kathie Hill at Raytheon Polar Services for data.

NSF Office of Polar Programs for general support
and travel funds.




                                                        19
                                        energy transfer over South Pole
conclusions:                                         G = RN + HS + HL

No energy balance. HS is probably larger in the monthly
mean (by 10 W m-2) than predicted by MO theory.

No significant frost deposition at the South Pole.

Snow surface temperatures at the South Pole result
in interface heat fluxes of up to 20 W m-2 on daily
time scales.

Episodic sustained heating rates of up to 3 K day-1 occur
in the near-surface snow at South Pole.

Heat plumes puncture deeper into the snow during
winter than summer.

Snow temperature gradients and heat fluxes important
for depth hoar formation and 18O2 fractionation.


                                                                          20
                                   energy transfer over South Pole
monthly means:                              G = RN + HS + HL
prior work on RN (net radiation)




                                                                     21
                                    energy transfer over South Pole
monthly means:                               G = RN + HS + HL
RN (net radiation)




                     RN 1994-1999




                                                                      22
                                         energy transfer over South Pole
monthly means:                                     G = RN + HS + HL
RN (net radiation)




                        RN 1994-1999




        More interannual variability during Summer                         23
        likely due to effect of clouds on solar radiation.
                           energy transfer over South Pole
monthly means:                      G = RN + HS + HL
G (subsurface heat flux)




                                                             24
                                  energy transfer over South Pole
monthly means:                             G = RN + HS + HL
G (subsurface heat flux)




                  Gfv 1994-1997




                                                                    25
                                        energy transfer over South Pole
monthly means:                                   G = RN + HS + HL
prior work on HS (sensible heat flux)




                                                                          26
                                         energy transfer over South Pole
monthly means:                                    G = RN + HS + HL
HS (sensible heat flux)




                          HS 1995-1999




                                                                           27
                                         energy transfer over South Pole
monthly means:                                    G = RN + HS + HL
HS (sensible heat flux)




                          HS 1995-1999




   monthly mean HS from MO theory is almost always                         28
   directed toward surface
                                energy transfer over South Pole
monthly means:                           G = RN + HS + HL
HL (latent heat flux)




                 HL 1995-2003




                                                                  29
                                               heat transfer in snow pack
         heat transfer model:
                                                                 1 cm
         finite volumes (Patankar 1982)
         variable levels                                         2 cm
         no accumulation (no advection)
         no sources (solar, wind pumping, …)                     5 cm



         boundary conditions:
          top: variable surface T (1-3 min)                      10 cm
          bottom: seasonal T gradient
                                                         6.5 m




                                                                 50 cm
T (oC)




                                                                            30
G Model properties:
Dalrymple et al. (1966)




                          31
         G Model validation:
         Carslaw and Jaeger (1959)
surface set
at –30oC




snow pack
set at –40oC




bottom set
to seasonal heat
flux at South Pole

                                     32
G Model validation:
Carslaw and Jaeger (1959)




                            33
Effect of clouds on RN:




                          34

				
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