Study of cirrus clouds physical properties using the Lidar-DUSTER system and radiosounding data at Natal/RN- Brazil

Abstract

Cirrus clouds are classified as the highest clouds in the atmosphere occurring generally from 7 to 18 km, depending on the global region of appearance, and have necessarily ice crystals in their composition. They still have an uncertain influence role in climate, therefore are seen as important atmospheric elements to be studied. Lidar systems (LIght Detecting and Ranging) have shown efficiency in the collection of cirrus characteristics which can help in its better parameterization in climatic and atmospheric models. In this work a collection of physical characteristics of cirrus was carried out, for January and February of 2017 and 2018, at Natal’s atmosphere using Lidar DUSTER’s data (5.84 S 35.20 W), a partnership UFRN/IPEN-SP. Morphological patterns of that clouds have been observed according to its heights as well as variations. Clouds with thinner depths and tenuous are observed at the top regions of troposphere, around 16.0 km. Otherwise, clouds with bigger vertical extensions are found around 12.0 km. The height of occurrence of cirrus in Natal, for the considered period vary from a minimum height of 7.0 km to a maximum of 16.0 km. Cirrus clouds most frequently occurred at a medium height of 12.0 km, considering both years. Those clouds had a considerable representativeness over the city atmosphere corresponding to 67% of total Lidar measured days. Besides the Lidar system was also used data from radiosounding technique. The behavior of the meteorological variables such as relative humidity was analyzed for the regions in which were found cirrus by the Lidar DUSTER. Within the region limits was verified a significant increase of relative humidity values. This behavior is not observed in lower regions where there is not any clouds presence as well in a day without cirrus appearance. In addition, future analyzes of the potential equivalent temperature profile will be studied in order to verify the effect of the cirrus clouds occurring in the temperature and humidity profile in a combined manner. Also, is expected to evaluate the possible impacts of cold air intrusion of the stratosphere in layers of cirrus clouds. In conclusion, Lidar DUSTER data demonstrates to be efficient in the identification of cirrus clouds over Natal’s atmosphere contributing to a better comprehension of its behavior and role in the region of study.