Abstract
Cirrus clouds are product of weather processes, and then their occurrence and macrophysical/optical properties can vary significantly over different regions of the world. Lidars can provide height-resolved measurements with a relatively good both vertical and temporal resolutions, making them the most suitable instrumentation for high-cloud observations. The aim of this work is to show the potential of lidar observations on Cirrus clouds detection in combination with a recently proposed methodology to retrieve the Cirrus clouds macrophysical and optical features. In this sense, a few case studies of cirrus clouds observed at both subtropical and polar latitudes are examined and compared to CALIPSO/CALIOP observations. Lidar measurements are carried out in two stations: the Metropolitan city of Sao Paulo (MSP, Brazil, 23.3°S 46.4°W), located at subtropical latitudes, and the Belgrano II base (BEL, Argentina, 78oS 35oW) in the Antarctic continent. Optical (COD-cloud optical depth and LR-Lidar Ratio) and macrophysical (top/base heights and thickness) properties of both the subtropical and polar cirrus clouds are reported. In general, subtropical Cirrus clouds present lower LR values and are found at higher altitudes than those detected at polar latitudes. In general, Cirrus clouds are detected at similar altitudes by CALIOP. However, a poor agreement is achieved in the LR retrieved between ground-based lidars and space-borne CALIOP measurements, likely due to the use of a fixed (or low-variable) LR value in CALIOP inversion procedures.
Highlights
The influence of Cirrus clouds on weather and climate is an evident fact
Both stCi and opCi occurrence is found between 8 and 11 km height, at similar altitudes as those found for CALIOP detected Cirrus clouds
Tropopause: 10.5 km Cirrus clouds have been analyzed in terms of their macrophysical and optical properties as retrieved by a recently developed methodology applied to lidar measurements
Summary
The influence of Cirrus clouds on weather and climate is an evident fact. They can act as modulators in the radiation balance of the Earth-atmosphere system, and their heating or cooling effects can be observed at both regional and global scales [1]. The sensitivity of Cirrus clouds to factors associated with humaninduced climate changes, i.e. greenhouse effect [2] and contamination of the upper troposphere from increasing aircraft traffic [3], is still poorly investigated. The predominance of infrared greenhouse warming versus solar albedo cooling depends sensitively on both the altitudes and microphysical compositions of the Cirrus clouds [4]. Since Cirrus clouds usually are located from 7 km height up to the tropopause, active remote sensing techniques, as lidars, are usually used for detection of Cirrus clouds from ground-based [5] and space [6] observations
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