Observational analysis and large scale associated with cold events moving until the line from (to) Ecuador at the South America

LIVIANY P. VIANA; DIRCEU L. HERDIES; MÜLLER GABRIELA V.

Viena

Conferencia; European Geosciences Union General Assembly; 2017

European Geosciences Union

An observational study was carried out to quantify theevents of cold air out-break moving above the Equator from 1980 to 2013 duringthe austral winter period (May, June, July, August and September), and lateranalyzed the behavior of the circulation responsible for this displacement. Theobservational datasets from the Sector of Climatological studies of theInstitute of Airspace Control of the city of Iauaretê (0.61N, 69.0W; 120m),located at the extreme northern of the Brazilian Amazon Basin, were used forthe analyzes. The meteorological variables used were the temperatures minimum,maximum and maximum atmospheric pressure. A new methodology was used toidentify these events, calculated by the difference between the monthly averageand 2 (two) standard deviations for the extremes of the air temperature, andthe sum of 1 (one) standard deviation for the maximum atmospheric pressure. Asa result, a total of 11 cold events were recorded that reached the extremenorthern of the Brazilian Amazon Basin, with values recorded at a minimumtemperature of 17.8 de ◦ C, at the maximum temperature of 21.0 ◦ C and maximumatmospheric pressure reaching 1021.2 hPa. These reductions and augmentation areequivalent to the negative anomalies of 5.9 and 8.7 ◦ C at the minimum andmaximum temperatures, respectively, while a positive anomaly of 7.1 hPa wasobserved at the maximum pressure. In relation to the dynamic behavior oflarge-scale circulation, a Rossby wave-type configuration propagating from westto east over subtropical latitudes was observed from the European Center for Medium-RangeWeather Forecast (ECMWF) since the days before the arrival of the event in thecity of Iauaretê. This behavior was observed both in the anomalies of thegepotencial (250 hPa and 850 hPa) and in the southern component of the wind(250 hPa and 850 hPa), both presenting statistical significance of 99 % (Student?sT test). Therefore, a new criterion for the identification of ?friagens? in thetropical latitude has been able to represent the effects of colds air outbreakand the advancement of the cold air mass, which are subsidized by thelarge-scale circulation, and consequently contribute to the modifications inthe weather and the life of the population over this Equatorial region.