 |
| Titel |
Technical Note: The horizontal scale dependence of the cloud overlap parameter α |
| VerfasserIn |
I. Astin, L. Girolamo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-19), S.9917-9922 |
| Datensatznummer |
250119048
|
| Publikation (Nr.) |
 copernicus.org/acp-14-9917-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| The cloud overlap parameter α relates the combined cloud fraction between
two altitude levels in a grid box to the cloud fraction as derived under the
maximum and random overlap assumptions. In a number of published studies in
this and other journals, it is found that α tends to increase with an
increasing scale. In this Technical Note, we investigate this analytically by
considering what happens to α when two grid boxes are merged to give a
grid box with twice the area. Assuming that α depends only on scale, then
between any two fixed altitudes, there will be a linear relationship between
the values of α on the two scales. We illustrate this by finding the
relationship when cloud cover fractions are assumed to be uniformly
distributed, but with varying degrees of horizontal and vertical correlation.
Based on this, we conclude that α increases with scale if its value is
less than the vertical correlation coefficient in cloud fraction between the
two altitude levels. This occurs when the clouds are deeper than would be
expected at random (i.e. for exponentially distributed cloud depths). |
| |
|
| Teil von |
|
|
|
|
|
|
|
|