Ceilometer Observation of Seasonal and Diurnal Variation in Cloud Cover Fraction, Cloud Base Height, and Visual Range in the Eastern Amazon Region
Matthew
J.
Czikowsky, University at Albany, State University of New York, matt@asrc.cestm.albany.edu
(Presenting)
David
Roy
Fitzjarrald, University at Albany, State University of New York, fitz@asrc.cestm.albany.edu
Ricardo
K
Sakai, University at Albany, State University of New York, sakai@asrc.cestm.albany.edu
Osvaldo
Luiz Leal de
Moraes, Universidade Federal de Santa Maria, moraes@mail1.ufsm.br
Otávio
C.
Acevedo, Universidade Federal de Santa Maria, otavioa@yahoo.com
Rodrigo
da
Silva, Universidade Federal de Santa Maria, rodrigo@asrc.cestm.albany.edu
At an old growth forest site of LBA-ECO (KM67), located in the Tapajos National Forest off Kilometer 67 of BR-163 south of Santarém, a Vaisala CT-25K ceilometer was installed in May, 2001 and was operational into 2003. The ceilometer provides 15-second measurements of cloud base (three levels up to 7500 m), echo intensity, and a 30-m resolution backscatter profile.
The ceilometer was operational for a sufficient amount of time to examine wet-to-dry season variations in cloud cover fraction, cloud base height, and visual range. Preliminary analysis of the lowest cloud base measurements shows the average lowest cloud base varies from near 1000m during wet season (February through June) afternoons to around 1500m in afternoons during the dry season (September through December).
We relate diurnal variations in the lowest cloud base height to the lifting condensation level (LCL). The LCL at a nearby cleared site (KM77) corresponds very well with the lowest cloud base detected by the KM67 ceilometer, whereas the LCL at the forested KM67 site is lower. Two other cloud layers are also sometimes dectected. Wet and dry season properties of deeper clouds will be discussed.
Submetido por Matthew John Czikowsky em 15-MAR-2004