 |
| Titel |
The surface energy budget and behavior of the stable boundary layer over the South Pole |
| VerfasserIn |
M. S. Town, V. P. Walden |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029825
|
|
|
|
|
|
| Zusammenfassung |
| Routine radiation and meteorological data at South Pole Station are used to investigate
historical discrepancies of up to 50 W m-2Â in the monthly mean surface energy balance, and
to investigate the behavior of turbulent heat fluxes under stable atmospheric temperature
conditions. The seasonal cycles of monthly mean net radiation and turbulent heat fluxes are
approximately equal, with a difference of 40 W m-2Â between summer and winter, while the
seasonal cycles of subsurface heat fluxes are only a few W m-2. For an 8-month period (the
winter of 2001), we have two estimates of turbulent heat fluxes, one from Monin-Obukhov
(MO) similarity theory and one as the residual of the surface energy budget (i.e.,
subsurface heat fluxes minus net radiation, where all fluxes toward the snow surface
are positive). The turbulent fluxes from MO theory agree well with the residual of
the energy budget under lapse conditions. However, under stable conditions MO
theory underestimates turbulent fluxes by approximately 40-60%. We also examine
the relationship between turbulent heat fluxes as a residual of the energy budget,
temperature inversion strength, and wind shear as a function of the bulk Richardson
number (Rib) under stable conditions (i.e. positive Rib). Our Rib is calculated
from 10-m wind speeds and 0- to 2-m temperature inversion strength. We find no
critical Rib above which turbulent heat fluxes drop to zero. However, we do find a
threshold (Rib = 0.05) below which 70% of the turbulent energy fluxes can be
explained by only the temperature inversion strength. For Rib > 0.05, the relationship
between turbulent heat fluxes and temperature inversion strength decreases, while the
importance of wind shear to turbulent heat transfer grows. Above Rib = 0.05, a
growing linear correlation also exists between atmospheric temperature inversion
strength and wind shear. Thus, for extremely stable conditions, inversion strength
and wind shear are not independent predictors of turbulent heat flux. The exact
values of the correlation coefficients and Rib threshold are likely specific to the
experimental conditions; however, their implications are probably valid for all stable flows.
Knowledge of the time-varying surface characteristics would help to generalize these
parameters. |
|
|
|
|
|
|