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Air Clear Turbulence in the Sothern Brazil: study Cases

Abstract

This analyzes the classic indexes modeled numerically to predict turbulence in the southern region of Brazil. Historical clear sky turbulence (CAT) events were reconstructed by using 25.465 AIREP messages, from 2015 to 2019, and 12.959 CAT records by aircraft from February 2018 to December 2019. The observations have shown that CAT events are proportionally distributed (in parentheses, its severity) in 94% (light), 4% (moderate), and 1% (severe). Synoptic analyses of five cases studied reveal that turbulence records occurred during clear sky conditions in the presence of a jet stream. Three joint analyses of the compositions of the variables modeled by GFS0.25 and WRF (18, 6 and 2 km grid), defined as, (1) wind profile, potential temperature (θ), turbulent kinetic energy (TKE); and (2) Richardson (Ri) and vertical speed (W), and (3) separately the CAT indicator indices called Ri, Brown, Ellrod-Endlich, and Ellrod-Knap, and Ellroad-Knox, showed that the improvement of spatial resolution data plays an important role in CAT forecasting. The response of the modeled indices is compared to their capacity to characterize the circumstances of a turbulent atmosphere in the vicinity of the VRTG records, and it was revealed that the Brown index was the most efficient for this, able to identify 100% of the five cases examined. The results of an initial attempt to adjust the CAT prediction indices (Brown, Ellrod-Endlich, and Ellrod-Knap) using modeled WRF data are reasonably promising, as the three adjusted indices detected 96%, and 99% of CAT event forecast 12 hours in advance on May 21, 2018 and March 27, 2019.

Keywords
clear air turbulence; CAT index; WRF model simulations; AIREP

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