SEVERE STORM DURING THE CAMPAIGN OF PROJECT CHUVA IN THE CITY OF BELÉM. Graduated in Meteorology at UFPA - Belém - Pará -

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1 SEVERE STORM DURING THE CAMPAIGN OF PROJECT CHUVA IN THE CITY OF BELÉM Ivan B. FIUZA de MELLO 1, Júlia C. PAIVA COHEN 2 1 Graduated in Meteorology at UFPA - Belém - Pará - imello11@hotmail.com 2 Meteorology Faculty UFPA - Belém - Pará - jcpcohen@ufpa.br ABSTRACT:This paper analyzes the development of a severe storm formed during the afternoon of June 7, 2011 in the northwestern state of Maranhão that propagated toward the city of Belém, when the Project Chuva campaign was being held in this city. During the passage of this storm in Belém it was observed intense rain, strong winds and heavy thunderstorms that caused material losses in the city. During the life cycle of this storm there was a center of maximum velocity of wind-driven in the direction of propagation of this storm. It was observed a reduction in temperature and humidity during the passage of this storm in the experimental area of the Project Rain. It was also carried out numerical simulation of this storm and the results were purchasable those found in the observed data. 1 - INTRODUCTION The constant atmospheric instability in Amazon Basin due to the wide availability of heat, moisture and energy, creates ideal weather conditions for the formation of severe storms in different scales, such as mesoscale convective systems (YOSHIDA, 2002). Mesoscale convective systems (MCS) are classified into three subscales: meso-α ( km), meso-β ( km) and meso-γ (2-20 km) (ORLANSKI, 1975). To study and understand the dynamics of mesoscale convective systems in the Amazon region, the first experimental mesoscale campaigns were performed in the 1980s, such as the ABLE-2b, which, in addition to the network data collection on the scale of the Amazon basin also included the installation of a mesoscale network in the Manaus region (HARISS, 1988). With the arrival of the LBA, mesoscale campaigns were conducted in various regions of the Amazon Basin (SILVA DIAS, 2002, 2004; FITAZJARRALD, et. al. 2008), providing the elucidation of various aspects of mesoscale phenomena. However, there is still much to advance the understanding of the physics of an internal storm, and Project Chuva ( allows that questions that are still in hold about the subject, in Brazil, may be better understood. During the days of May 30 th to July 2 th 2011, a Project Chuva campaign was carried out in Belém do Pará, where several convective systems were observed, as well as squall lines, isolated convection and severe storms, such as supercells. Supercells are deep convective systems, formed from the difference of temperature and pressure between two air masses. The period of formation of these cells occurs at the end of the afternoon, a time when the atmosphere is most unstable, with

2 atmospheric turbulence and the presence of clouds with great vertical development (CB). The supercells presents a characteristic of been isolated clouds from other cloud systems, whose base extends nearby the proximities of the surface, the presence of gust fronts and mamattus clouds, intense areas of rain and a change in flow direction of the prevailing wind in the region where the system is acting. Analyzes and studies suggest that these systems may be classified as MCS, by having physical and visual characteristics of a mesocyclone at low levels. (DAVIES, 1986). Thus, the main objective of this work is to analyze the formation and propagation of a mesoscale convective system that formed in the northwestern state of Maranhão and spread westward, entering the state of Pará, with maximum activity recorded on the town Belém, for subsequent dissipation in Marajó Island. 2 METHODOLOGY Figure 1 shows the location of the instruments installed by Project Chuva in Belém area. In the experimental site of Outeiro, located inside Belém area, temperature, humidity and wind data were collected such as data from rain gauges and disdrometers in order to analyze the impact of the passage of this storm. At Belém airport, on that occasion, radiosondes were launched four times at 00, 06, 12, and 18 UTC, throughout the campaign period. The radiosonde launched at 18 UTC on 7 th June is the atmospheric condition before the arrival of the storm in Belém, while the one launched at 00 UTC of June 8 th, shows the environment after the storm. Images from GOES-12 satellite were used to analyze the life cycle of the storm since its formation in northwest Maranhão until the moment it hit the city of Belém. When this system reached Belém area, it was used dual polarization X-band data from the radar installed in UFPA, which allowed a more detailed analysis of the storm, both horizontally and vertically. The NCEP reanalysis also were used to investigate the large-scale environment where they developed this convective system.

3 Figure 1 - Location of meteorological instruments used during the Project Rain in the Belém region. The Brazilian version of the Regional Atmospheric Modeling System (BRAMS) (PIELKE, 1992 and COTTON, 2003) was used to verify mainly the structure of the storm that reached the Project Chuva area in Belém when the collected data by Project Chuva was available which allowed to calibrate the results acquired by the numerical simulations. The BRAMS is a three-dimensional model consisting of a set of equations prognostic, including dynamic and thermodynamic microphysics hydrometeors, which are numerically solved using finite difference scheme. This model contains interactions with several submodels that simulate the exchange of heat and water interfaces in soilvegetation-atmosphere (WALKO, 2000); turbulent processes in the surface layer (LOUIS, 1979), processes in turbulent boundary layer (MELLOR; YAMADA, 1982); transfer of solar and thermal radiation and its interaction with hydrometeors (HARRINGTON, 1997), and cloud and precipitation microphysics (WALKO, 2000). The simulation of this storm has been developed using a grid whose horizontal resolution was 9 km, with an array of 135x99x40 points. 27 were considered in the vertical levels of the atmosphere, the first being equal to 50 meters and the next increased by a factor of 1.1, when compared to the previous level until 1000 and then remains constant up to the top of the model. The NCEP reanalysis, vegetation data from INPE, the global topography data from the United States Geological Survey (USGS) data and sea surface temperature (SST) from NOAA were used as initial and boundary condition of the model. The model integration was 18 hours, from 12 UTC on 7 th June 2011 until 06 UTC on June 8 th, 2011, which covers the period of training, development and dissipation of convective cell. 3 - RESULTS AND DISCUSSION 3.1 LIFE CYCLE OF THE STORM Figure 2 shows the life cycle of the storm from its formation until its dissipation. This convective system formed in the west coast state of Maranhão at 14 UTC on 7 th June 2011 (not showed), two hours later there is an intensification of this convection that spread westward along the coast, reaching Belém area around 20 UTC of the same day (Figure 2c). The arrival of this convective cell in Belém area caused heavy rain with flooding, felling billboards and trees, among other disorders. This storm continued its spread reaching Marajó Island at 23:30 UTC, occurred where its dissipation (Fig. 2e). Figure 3 below shows the reflectivity in dbz radar dual polarization X-band when the convective system was in the region of Belém, at 20:14 UTC on June 7 th, Figure 4 shows the vertical profile of the storm at 20:30 UTC on June 7 th, 2011, the city of Belém. Note that the top of the storm reached a vertical development of up to 13 km altitude. The regions of higher reflectivity were inside the storm between the surface and the first 5 km altitude, near 40 dbz, indicating the regions of more intense activity of the system.

4 a) 16 UTC June 7 th 2011 b) 18 UTC June 7 th 2011

5 c) 20 UTC June 7 th 2011 d) 22 UTC June 7 th 2011

Maranhão, until its dissipation in the region of

6 e) 23:30 UTC June 7 th 2011 Figure 2 - Life cycle of convective cell since its formation in the state of Maranhão, until its dissipation in the region of Marajó. Figure 3 - Image of the X band radar 20:14 UTC.

7 Figure 4 - Range Height Indicator of the convective cell approaching the radar in UFPA on June 7 th, 2011, at 20:30 UTC. 3.2 LARGE SCALE ENVIRONMENT The Figure 5 shows the flow of the wind at the level of 925 hpa, obtained from the NCEP reanalysis, from 12 UTC on 7 th June 2011 to the 00 UTC on June 8 th, Note a center of maximum wind speed, whose orientation was east-west along the coast. At the time of 18 UTC, when the storm was at one of its peaks of activity, there is a greater intensity in the flow of the wind compared to the time before and after the training period during which the storm was dissipating. It is possible that this flow southeast has promoted the spread of this storm from Maranhão to Belém area.

8 (a) Before - 12 UTC June 7 th 2011 (b) During - 18 UTC June 7 th 2011

9 (c) After - 00 UTC June 8 th 2011 Figure 5 - Flow of wind at 925 hpa and isotacas (lines) at different stages of the convective cell: (a) Before (12 UTC June 7 th, 2011), (b) During (18 UTC June 7 th, 2011) (c) After (00 UTC June 8 th, 2011). Figure 6a shows the zonal wind changes before and after the passage of the storm over the region of Belém, when two east jets are observed, with the first one at 500 meters and the second at 7 km in height. In both jets, there is an intensification of the same after the storm, leaving emphasize that this difference is relatively small for the jet located at 7 km. The meridional wind at low levels showed up before moving south of Belém by the storm, and moving to the northeast after exceeding the capital of Pará (Figure 6b). The air temperature cooling air shows with the storm, particularly close to the surface. The profile of relative humidity shows at low levels an increase of moisture with the passage of this storm.

10 a - Zonal wind b Meridional wind

11 c - Air temperature d Relative humidity Figure 6 Profile of (a) zonal wind component, (b) meridional wind component, (c) air temperature, (d) relative humidity before (June 7 th, 2011 at 18 UTC) and after (June 8 th, 2011 at 00UTC) of the passage of the storm in Belém.

12 3.3 IMPACT OF THE STORM IN BELÉM METROPOLITAN REGION The precipitation rate estimated by disdrometers Parsivel and Joss was up to 100mm/h and 60 mm/h, respectively, characterizing the arrival of the storm in the region of Belém around 20:30 UTC (Figure 7). On this day, the rain gauges installed in Outeiro did not record the data. The passage of this convective system over Outeiro caused a drop in temperature of around 4 C and air humidity of approximately 5%, indicating that the arrival of this storm on the site caused the cooling and increased humidity air close to the surface (Figure 8a). The distribution of wind speed shows a gust front that preceded the arrival of the storm and whose origin is associated with downdrafts that bring the cooler and drier air levels above. (Figure 8b). The passage of this storm also promoted a shift in wind direction that prior to the passage, had a predominant component of north becoming south after passing the region of Outeiro. Figure 7 Precipitation rate estimated by disdrometers parsivel, joss and rain gauges installed at the site of Outeiro during the passage of the convective cell. (a) (b) Fonte: Boletim Meteorológico Fonte: INPE/CPTEC (2013) Figure 8 - (a) Temperature and relative humidity changes and (b) the wind during the passage of convection in Outeiro.

13 Figure 8 - (a) Temperature and relative humidity changes and (b) the wind during the passage of convection in Outeiro. 3.4 NUMERICAL SIMULATION Horizontal Structure Figure 9 shows the rate of precipitation and wind at the level of 76.8 meters, when the system was getting in the region of Belém, at 23:30 UTC. It is observed that the simulations captured the storm's development since its formation in Maranhao, until its dissipation in the state of Pará, and his arrival in the Belém area was three hours late in relation to the observed. The wind was predominantly from the northeast along the coast of Pará, entering into the river through the east side of the island Marajó. It points out the generated precipitation rate when the convection was in the region of Belém, of the order of 100 mm / h, i.e. comparable to that found by disdrometer Parsivel (Figure 7). (a) June 7 th 2011 at 18 UTC (b) June7 th 2011 at 23:30 UTC

14 Figure 9 - Horizontal Wind (m/s) at the level of 24.4 meters and rain rate obtained through the cloud microphysics (mm/ h): (a) at the beginning of the formation of convective cell (June 7 th, 2011 the 18 UTC). (b) Development of convective cell over the region of Belém (June 7 th, :30 UTC) Vertical Structure Figure 10 shows the vertical profile of the condensate and of the zonal wind, with the vertical wind found through BRAMS. Here, we can observe the structure of the storm similar to that observed in the radar (Figure 4). The top of the storm reached 10 km, whereas the observed was 13 km. Moreover, it is observed that the most active region of this system was located until the level of 5 km, as observed on the radar data (Figure 6). Figure 10 - Vertical profile of horizontal wind (m/s) and vertical multiplied by 10 (vector) and cloud mixing ratio (g/kg) in latitude o S on June 7th, 2011, at 23:30 UTC.

15 4 - CONCLUSIONS The main objective of this work was to study the development of a storm that originated in the northwest of the state of Maranhão and spread west to reach the city of Belém do Pará. This study was based on data collected during the Project Chuva campaing in Belém, and the results of a simulation with BRAMS, with the following main conclusions: The large scale flow showed a center of maximum wind speed on the northeast of Brazil, whose direction was east-northeast, coincident with the direction of propagation of the convective cell formed in Maranhão, which hit the region of Belém as a severe storm, causing significant material damage to the population of the state capital. The passage of this storm in the experimental area of Project Chuva showed a drop in temperature and an increase in the humidity, the one associated with the current vertical descent which is responsible of bringing cooler and dry air to average levels. The numerical simulation of this storm was compatible with the observed results, highlighting intense rain rate, maximum storm intensity localized to the level of 5 km, drop in temperature and increase in humidity with the storm in Belém. Therefore, even if the horizontal resolution of this simulation was 9 km, it was possible to follow the development of the convective cell, the same as the rate of rainfall generated by the model was similar to that reported by the disdrometers. It was found that studied the storm proved a supercell, since their physical and dynamical characteristics met the main requirements typical of this classification: isolated storm, presence of mamattus clouds, strong gust fronts, areas of intense precipitation and change in direction of the prevailing wind. 5 - REFERENCES DAVIES, J. Tornado dynamics. Thurderstorm morphology and dynamics. 2a ed, Ed.E.Kessler, University of Oklahoma Press, p FITZJARRALD, D. R.; R. K. SAKAI.; O. L. L. MORAES.; R. C. de OLIVEIRA.; O. C. ACEVEDO.; M, J. CZIKOWSKY.;T. BELDINI. Spatial and temporal rainfall variability near the Amazon-Tapajós confluence. Journal of Geophysical Research G: Biogeosciences, v.114, p HARRISS, R. C., S. C., WOFSY, M. GARSTANG, E. V. BROWELL, C. B. MOLION, R. J. MCNEAL, J. M. HOELL, R. J. BENDURA, S. M. BECK, R. L. NAVARRO, J. T. RILEY, E R. L. SNELL: The Amazon Boundary Layer Experiment (ABLE 2A): Dryseason J. Geophys. Res., 93, p

16 INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS (INPE/CPTEC). Boletim Meteorológico. Disponível em: Acesso em INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS (INPE/CPTEC). Comportamento da temperatura. Disponível em: Acesso em ORLANSKI, I.A Rational subdivision of scales for atmospheric processes.bulletin of the American Meteorological Society, v.56, n. 5, p SILVA DIAS, M. A. F.A Case study of Convective Organization into Precipitating Lines on Southwest Amazon during the WETAMC and TRMM-LBA.Journal of Geophysical Research, v.107, p YOSHIDA, M. C. Estudo de células convectivas em Rondônia durante o experimento WETAMC-LBA/TRMM Dissertação (Mestrado do Curso de Pós-Graduação em Meteorologia) -INPE TDI/1554, SP

Micro Squall Line in Belem region. Tarcísio Miranda do Amaral Neto (1) Júlia Clarinda Paiva Cohen (1) Luiz Augusto Toledo Machado (2)

1 Micro Squall Line in Belem region Tarcísio Miranda do Amaral Neto (1) Júlia Clarinda Paiva Cohen (1) Luiz Augusto Toledo Machado (2) (1) Universidade Federal do Para, Belém, Brasil. (2) Centro de Previsão