 |
| Titel |
Using digital image processing to characterize the Campbell–Stokes sunshine recorder and to derive high-temporal resolution direct solar irradiance |
| VerfasserIn |
A. Sanchez-Romero, J. A. González, J. Calbó, A. Sanchez-Lorenzo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 1 ; Nr. 8, no. 1 (2015-01-12), S.183-194 |
| Datensatznummer |
250116046
|
| Publikation (Nr.) |
 copernicus.org/amt-8-183-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Campbell–Stokes sunshine recorder (CSSR) has been one of the most
commonly used instruments for measuring sunshine duration (SD) through the
burn length of a given CSSR card. Many authors have used SD to obtain
information about cloudiness and solar radiation (by using
Ångström–Prescott type formulas), but the burn width has not been
used systematically. In principle, the burn width increases for increasing
direct beam irradiance. The aim of this research is to show the relationship
between burn width and direct solar irradiance (DSI) and to prove whether
this relationship depends on the type of CSSR and burning card. A method of
analysis based on image processing of digital scanned images of burned cards
is used. With this method, the temporal evolution of the burn width with
1 min resolution can be obtained. From this, SD is easily calculated and
compared with the traditional (i.e., visual) determination. The method tends
to slightly overestimate SD, but the thresholds that are used in the image
processing could be adjusted to obtain an improved estimation. Regarding the
burn width, experimental results show that there is a high correlation
between two different models of CSSRs, as well as a strong relationship
between burn widths and DSI at a high-temporal resolution. Thus, for example,
hourly DSI may be estimated from the burn width with higher accuracy than
based on burn length (for one of the CSSR, relative root mean squared error
is 24 and 30%, respectively; mean bias error is −0.6 and
−30.0 W m−2, respectively). The method offers a practical way to
exploit long-term sets of CSSR cards to create long time series of DSI. Since
DSI is affected by atmospheric aerosol content, CSSR records may also become
a proxy measurement for turbidity and atmospheric aerosol loading. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|