 |
| Titel |
Cirrus crystal fall velocity estimates using the Match method with ground-based lidars: first investigation through a case study |
| VerfasserIn |
D. Dionisi, P. Keckhut, C. Hoareau, N. Montoux, F. Congeduti |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-22), S.457-470 |
| Datensatznummer |
250017810
|
| Publikation (Nr.) |
 copernicus.org/amt-6-457-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
Cirrus ice particle sedimentation velocity (vs) is one of the critical
variables for the parameterization of cirrus properties in a global climate
model (GCM). In this study a methodology to estimate cirrus properties, such
as crystal mean fall speed, through successive lidar measurements is
evaluated. This "Match" technique has been applied on cirrus cloud
observations and then tested with measurements from two ground-based lidars
located in the Mediterranean area. These systems, with similar instrumental
characteristics, are installed at the Observatory of Haute
Provence (OHP, 43.9° N, 5.7° E) in France and at Rome
Tor Vergata (RTV, 41.8° N, 12.6° E) in Italy. At a
distance of approximately 600 km, the two lidar stations have provided systematic
measurements for several years and are along a typical direction of an air
path. A test case of an upper tropospheric cirrus, observed over both sites
during the night between 13 and 14 March 2008, has been selected and the
feasibility of the Match-cirrus approach investigated through this case. The
analysis through lidar principal parameters (vertical location, geometrical
thickness and optical depth) reveals a case of a thin sub-visible cirrus
(SVC) located around the tropopause. A first range of values for vs
(1.4–1.9 cm s−1, consistent with simple-shaped small crystals) has been
retrieved with a simplified approach (adiabatic transport and "frozen"
microphysical conditions inside the cirrus). The backward trajectory
analysis suggests a type of cirrus formed by large-scale transport processes
(adiabatic cooling of moist air masses coming from the subtropical area
around Mexico gulf), which is characterized by a long atmospheric lifetime
and horizontal extension of several hundred km. The analysis of this
case study reveals that many uncertainties reduce the confidence of the
retrieved estimates of the crystal fall velocity. However, this paper allows
for assessing the technique feasibility by identifying the main critical issues
for future similar investigations.
This study shows that such approach is feasible; however, the methodology
should be improved and some directions have been suggested for future
campaigns. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|