Characteristics of the Precipitating Systems during the 2002 Dry-to-Wet RACCI Field Campaign in the Amazon Region

This paper will present the main characteristics of the raining systems observed during the 2002 Dry-to-Wet RACCI field campaign in the Amazon region. This experiment was set during the 2002 pre-wet season (September-November) in Amazon region to understand the impact of the aerosols produced by forest burning in the development of clouds. A weather radar, rain gauges, and lightning measurements are used to depict the main precipitation characteristics observed during this field campaign. In this work, we have applied a cloud tracking algorithm, denoted FORTRACC, adjusted to the radar reflectivity CAPPI fields, to track the entire life cycle of the storm. By combining with the lightning measurements, we were able to analyze the storms with and without lightning. Preliminary results of these analyses have shown that: a) thunderstorms are 20-30% larger (12-25 km in radius) than non-lightning storms (9 – 15 km in radius); b) The 35 dBZ height for thunderstorms are above 6.5 km while for the non-lightning storms are below 4 km; c) The lightning frequency cycle is better defined for thunderstorms with lifecycle above 30 min), with maximum frequency occurrence between 1.5 flashes/normalized time step for less 2h and 2.5 flashes/normalized time step for above 2h; d) the systems lasting more than 2 hours present several lightning frequency oscillations that might be associated to the establishment of updrafts/downdrafts and the rainfall; e) and finally the thunderstorms show the presence of radar reflectivity of 35-40 dBZ between the 3-6 km during their entire lifecycle, while the ordinary storms present only 30-35 dBZ at the same level.