Figure 1
Isopleths map of current NBR 6123 [11 Associação Brasileira de Normas Técnicas, Forças devidas ao vento em edificações, NBR-6123, 1988.]. V0 values in m/s shown at tips of isocurves; numbers associated to dots identify the weather stations.
Figure 2
Schematic illustration of a convective-scale downward current (or downdraft), from which originates a type of intense non-synoptic winds, and photos of the leading edge of a microburst-producing supercell storm over the city of Porto Alegre, RS on 29th of January, 2016 [1919 Loredo-Souza, A.M., Lima, E.G., Vallis, M.B., Rocha, M.M., Wittwer, A.R., and M.G.K. Oliveira, "Downburst related damages in Brazilian buildings: are they avoidable," J. Wind Eng. Ind. Aerodyn., vol. 185, pp. 33–40, 2019.].
Figure 3
Mean wind profile corresponding to V0 equal to 40 m/s for atmospheric boundary layer winds (full line) and downburst-like winds (dashed line, with maximum at height of 40 m) during its horizontal divergence at low-levels, based on Vicroy model [2020 D. D. Vicroy, "Assessment of microburst models for downdraft estimation," J. Aircr., vol. 29, no. 6, pp. 1043–1048, 1992.].
Figure 4
Schematic vertical cross-sections displaying the time evolution of the atmospheric flow across a stationary downburst (left column), and a typical moving or non-stationary downburst (right column) (based on Fujita [1717 T. T. Fujita, "Tornadoes and downbursts in the context of generalized planetary scales," J. Atmos. Sci., vol. 38, pp. 1511–1534, 1981.]).
Figure 5
Schematic charts for the Northern Hemisphere displaying close up views of horizontal flow patterns originating from the combination of synoptic and non-synoptic winds forced by atmospheric processes belonging to different scales of motion. From (a) to (d), panels depict flow patterns at ever shorter horizontal scales (based on [1717 T. T. Fujita, "Tornadoes and downbursts in the context of generalized planetary scales," J. Atmos. Sci., vol. 38, pp. 1511–1534, 1981.]).
Figure 6
Schematic illustration of the passage of a non-stationary downburst by a building (based on Chay et al.
[24]24 M. T. Chay, F. Albermani, and R. Wilson, "Numerical and analytical simulation of downburst wind loads," Eng. Struct., vol. 28, no. 2, pp. 240–254, Jan 2006, http://dx.doi.org/10.1016/j.engstruct.2005.07.007.
http://dx.doi.org/10.1016/j.engstruct.20...
).
Figure 7
Annual frequency, in terms of the mean number of hours per year (see color convention), of atmospheric conditions that are favorable to the occurrence of (a) convective storms in general, and (b) severe convective storms, in South America. The climatology refers to the 1979 to 2019 period and is based on the 5
th Generation of the European Center for Medium-Range Weather Forecasting reanalysis (ERA5) dataset. (Adapted from Taszarek et al. [
2525 M. Taszarek, J. T. Allen, M. Marchio, and H. E. Brooks, "Global climatology and trends in convective environments from ERA5 and rawinsonde data," npj Clim Atmos Sci., vol. 4, pp. 35, 2021, https://doi.org/10.1038/s41612-021-00190-x.
https://doi.org/10.1038/s41612-021-00190...
]).
Figure 8
Distribution of large forest clearings due to natural causes in the Amazon region (adapted from [2626 M. Garstang, S. White, H. H. Shugart, and J. Halverson, "Convective clouds downdrafts as the cause of large blowdowns in the Amazon Rainforest," Meteorol. Atmos. Phys., vol. 67, pp. 199–212, 1998.]).
Figure 9
Climatology of wind gusts generated by severe storms in southern Brazil, based on measurements from the national network of INMET automated surface weather stations between 2005 and 2015. Diameters of the black circles are proportional to the number of occurrences of convectively-induced wind gusts equal to or greater than 25 m/s; see convention in ref. [2929 V. Ferreira, "Um estudo observacional de rajadas de vento geradas por tempestades severas no sul do Brasil," M.S. thesis, Univ. Fed. Sta. Maria, Santa Maria, RS, Brasil, 2017.].
Figure 10
Mean annual density of surface cyclogenesis per km
2 (see color convention) detected between 1979 and 2015 based on the ERA-Interim reanalysis and the Climate Forecast System reanalysis. The three regions with more frequent cyclogenesis frequency are indicated as ‘RG’ (based on [
3030 E. de Jesus, R. Rocha, N. Machado Crespo, M. Reboita, and L. Gozzo, "Multi-model climate projections of the main cyclogenesis hot-spots and associated winds over the eastern coast of South America," Clim. Dyn., 2021, http://dx.doi.org/10.1007/s00382-020-05490-1.
http://dx.doi.org/10.1007/s00382-020-054...
]).
Figure 11
Geographical delineation of regions that share similar regimes of atmospheric phenomena that generate intense surface winds in Brazil.
Figure 12
Network of meteorological weather stations with wind speed data processed by Vallis [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 13
Distribution fit and data for maximum annual wind speeds at station A86 in Florianópolis, SC [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 14
Distribution fit and data for maximum annual wind speeds at station SBBE in Belém, PA [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 15
Zone map for non-synoptic winds proposed by Vallis [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 16
Basic wind speed map proposed by Vallis [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 17
Overview of selected weather stations and corresponding V0 values (m/s) processed by Vallis [77 M. B. Vallis, "Brazilian extreme wind climate," Ph.D. dissertation, Esc. Eng., Univ. Fed. Rio Grd. Sul, Porto Alegre, RS, 2019.].
Figure 18
Amazon climate region and proposed isopleths, V0 in m/s.
Figure 19
South region: a) climatic regions; b) proposed isopleths (V0 in m/s).
Figure 20
Northeast region: a) climatic regions; b) proposed isopleths (V0 in m/s).
Figure 21
Center and southeast region: a) climatic regions; b) proposed isopleths (V0 in m/s).
Figure 22
Final basic wind speed map proposed for NBR 6123 (isopleths with V0 in m/s).
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