 |
| Titel |
Testing longwave radiation parameterizations under clear and overcast skies at Storglaciären, Sweden |
| VerfasserIn |
J. Sedlar, R. Hock |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1994-0416
|
| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 3, no. 1 ; Nr. 3, no. 1 (2009-04-27), S.75-84 |
| Datensatznummer |
250000786
|
| Publikation (Nr.) |
 copernicus.org/tc-3-75-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| Energy balance based glacier melt models require accurate estimates of
incoming longwave radiation but direct measurements are often not available.
Multi-year near-surface meteorological data from Storglaciären, Northern
Sweden, were used to evaluate commonly used longwave radiation
parameterizations in a glacier environment under clear-sky and all-sky
conditions. Parameterizations depending solely on air temperature performed
worse than those which include water vapor pressure. All models tended to
overestimate incoming longwave radiation during periods of low longwave
radiation, while incoming longwave was underestimated when radiation was
high. Under all-sky conditions root mean square error (RMSE) and mean bias
error (MBE) were 17 to 20 W m−2 and −5 to 1 W m−2,
respectively. Two attempts were made to circumvent the need of cloud cover
data. First cloud fraction was parameterized as a function of the ratio,
τ, of measured incoming shortwave radiation and calculated top of
atmosphere radiation. Second, τ was related directly to the cloud factor
(i.e. the increase in sky emissivity due to clouds). Despite large scatter
between τ and both cloud fraction and the cloud factor, resulting
calculations of hourly incoming longwave radiation for both approaches were
only slightly more variable with RMSE roughly 3 W m−2 larger compared
to using cloud observations as input. This is promising for longwave
radiation modeling in areas where shortwave radiation data are available but
cloud observations are not. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|