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Revista Brasileira de Meteorologia

Print version ISSN 0102-7786


COSTA, Alexandre Araujo; CAMPOS FILHO, Mucio Costa; SANTOS, Antonio Carlos Santana dos  and  OLIVEIRA, José Carlos Parente de. Characteristics of ice crystals observed in a cloud system over the Amazon during the TRMM-LBA experiment. Rev. bras. meteorol. [online]. 2012, vol.27, n.2, pp.139-151. ISSN 0102-7786.

During the months of January and February 1999, the TRMM/LBA (Tropical Rainfall Measuring Mission/Large Scale Biosphere-Atmosphere Experiment in Amazonia) campaign took place, in which microphysical properties of deep convective clouds were investigated. The experiment was part of an international effort to calibrate TRMM satellite sensors for precipitation, radiation and atmospheric electricity studies. The data used in the present work were collected by instruments on board North Dakota University's Citation II aircraft, including data from a set of spectrometric probes that measured concentration and size of ice crystals, with distinction to the 2DC (Two-dimensional Cloud) probe. This instrument identifies not only number concentration and size of the cloud particles, but also their shape. The aircraft performed several flights during the TRMM/LBA experiment and data from 10 February 1999 are analyzed in this paper. Inside the cloud system, ice crystals were observed in a variety of shapes and sizes. A certain agreement was found between the crystal shape and the expected patterns of ice crystal growth as a function of temperature and humidity, but crystal habit superposition was also found, suggesting the existence of mixture between air parcels from different cloud regions and indicating that crystal sedimentation plays a significant role in the evolution of the microphysics of deep convective clouds. It was also noted that the size distribution of the ice crystals follows approximately a power law.

Keywords : TRMM-LBA; deep convection; cloud microphysics; ice crystals.

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