




































 
 
 

Asian Review of Environmental and Earth Sciences 
Vol. 4, No. 1, 7-11, 2017 

ISSN(E) 2313-8173 / ISSN(P) 2518-0134 
DOI: 10.20448/journal.506.2017.41.7.11 

 
 
 
 
 

 

7 
 

Dynamics in Times of Ionizing Radiation and Rainfalls in Tropical Region of Brazil 

 
Inacio M. Martin1


      

Douglas C. Vilela2     

Marcelo P. Gomes3      

 

 
( Corresponding Author) 

 
1,2,3Technological Institute of Aeronautics, ITA, SP, Brazil 

 
Abstract 

Low energy gamma rays and rainfalls were monitored each minute in the region around São José 
dos Campos, (230:10`S, 450:53`W) in Brazil, from March 7th to June 28th in 2017. In this period, it 
was possible to see the dynamic process that occurs between the presence of ionizing radiation 
(gamma rays) of low energy and the variation of rain intensity in (mm) / min in the same region. 
During this period, 12 major peaks of radiation intensity corresponding to 12 rains of high and 
low intensities were observed. This positive rainfall / radiation correlation is very noticeable in 
the tropical region of Brazil, which is certainly due to the presence of the decay of 238U uranium 

into radium 226Ra and arriving at the 222Rn radon with α emission particles and low energy 
gamma radiation. Therefore, the rain interferes in the presence of the local exhalation of the radon 
gas, causing the washing of this gas in the low atmosphere, increasing the intensity of radiation 
measured momentarily in that location. This work shows this dynamic measured in this interval 
in the year 2017, where there was rainy and dry weather in the place. 

 
Keywords: Gamma Ray, Ionizing radiation, Rainfall analysis, tropical regions 

 
Citation | Inacio M. Martin; Douglas C. Vilela; Marcelo P. Gomes 
(2017). Dynamics in Times of Ionizing Radiation and Rainfalls in 
Tropical Region of Brazil. Asian Review of Environmental and 
Earth Sciences, 4(1): 7-11. 
History:  
Received: 29 June 2017 
Revised: 18 July 2017 
Accepted: 21 July 2017 
Published: 26 July 2017 
Licensed: This work is licensed under a Creative Commons 

Attribution 3.0 License  
Publisher: Asian Online Journal Publishing Group 
 

Contribution/Acknowledgement: All authors contributed to the conception 
and design of the study. 
Funding: Thanks CNPq (National Counsel of Technological and Scientific 
Development) and CAPES (Coordination for the Improvement of Higher 
Education Personnel) by the fellowships grants support to the group's 
researchers. The ITA Division of Fundamental Sciences for supporting this 
research. 
Competing Interests: The authors declare that they have no conflict of 
interests. 
Transparency: The authors confirm that the manuscript is an honest, 
accurate, and transparent account of the study was reported; that no vital 
features of the study have been omitted; and that any discrepancies from the 
study as planned have been explained. 
Ethical: This study follows all ethical practices during writing.   

 

 

Contents 
1. Introduction ......................................................................................................................................................................................... 8 
2. Materials and Methods ...................................................................................................................................................................... 8 
3. Results and Discussions ..................................................................................................................................................................... 8 
4. Conclusion ......................................................................................................................................................................................... 10 
References .............................................................................................................................................................................................. 10 
 

 

 

 

 

 

 

 

http://creativecommons.org/licenses/by/3.0/
http://creativecommons.org/licenses/by/3.0/
https://orcid.org/orcid-search/quick-search?searchQuery=Inacio M. Martin
https://orcid.org/orcid-search/quick-search?searchQuery=Douglas C. Vilela
https://orcid.org/orcid-search/quick-search?searchQuery=Marcelo P. Gomes
https://orcid.org/orcid-search/quick-search?searchQuery=Inacio M. Martin
https://orcid.org/orcid-search/quick-search?searchQuery=Douglas C. Vilela
https://orcid.org/orcid-search/quick-search?searchQuery=Marcelo P. Gomes
https://orcid.org/orcid-search/quick-search?searchQuery=Inacio M. Martin
https://orcid.org/orcid-search/quick-search?searchQuery=Douglas C. Vilela
https://orcid.org/orcid-search/quick-search?searchQuery=Marcelo P. Gomes
https://orcid.org/orcid-search/quick-search?searchQuery=Inacio M. Martin
https://orcid.org/orcid-search/quick-search?searchQuery=Douglas C. Vilela
https://orcid.org/orcid-search/quick-search?searchQuery=Marcelo P. Gomes


Asian Review of Environmental and Earth Sciences, 2017, 4(1): 7-11 

8 
 

 

1. Introduction 
In the ground level interface of the Earth's surface, ionizing radiation is mainly comprised of radon gas, the 

telluric radiation from the ground and the primary and secondary cosmic ray radiation. However, it is difficult to 
separate over time the intensity of ionizing radiation emanating from each component as the energies overlap. The 
telluric radiation is composed of 238U, 235U, 40K, 232Th chains and is constant for each region [1]. Radon gas comes 
from the 238U decay of the Earth's crust [2] to Ra-226 and Rn-222 arriving in isotopes 214Pb, 214Po and 214Bi giving 

α and gamma radiation. The primary cosmic radiation mainly consists of galactic and extragalactic protons from 
the Sun with very high energy, which interact on the Earth's atmosphere producing the EAS (Extensive Air 
Showers) [3]. The efficiency of this interaction is maximal when it occurs at altitudes between 15 and 17 km in the 
tropics, forming secondary cosmic rays with muonic, mesonic, and neutronic components that propagate to the 
Earth's surface in the region [4]. These radiations cause health problems for the crew and passengers of civil 
aviation and are present at the beginning of the stratosphere called maximum Pfotzer. However, this component 
contributes less to radiation concentration on the Earth's surface. Another possible existing ionizing radiation 
source in the lower atmosphere of the Earth is produced by electrical discharges between clouds-earth-ground and 
clouds-clouds. X-rays, gamma rays, neutrons and beta particles are formed all the way of the lightning cone [5]. 
Other ionizing radiation sources are those produced in medical, dental clinics and hospitals, but these radiations are 
mostly controlled in small areas.  
 

2. Materials and Methods 
The gamma ray detector for the energy interval of 200 keV to 10.0 MeV consists of a scintillating crystal of 

sodium iodide 3 inches high by 3 inches in diameter (3” x 3”), doped with thallium. This crystal is coupled directly 
to a photomultiplier (PM), which registers the pulses coming from the scintillator and with amplification and an 
analog-to-digital converter that is registered by a computer [6]. This experimental set is seen in Figure 1 located 
in a room inside a tower 25 meters high in relation to the ground. In that tower and with all radiation detectors 
and meteorological apparatus is running the project Atmosrad – Ionizing radiation in low atmosphere – since 2009. 
This project have grants each year from ITA and National Brazilian Research Council (CNPq). 
 

 
Figure-1. View of the gamma scintillator with associated electronics and computer 

                             Source: Project Atmosrad 2017 

 
The scintillator coupled with a photomultiplier is wrapped in a thin layer of aluminum to make it portable. The 

set (scintillator + associated electronics + data acquisition) depends only on a laptop with fully charged battery to 
measure radiation up to 10 hours straight. However, for series of longer measurements, electrical grid or 
photovoltaic energy is used. The scintillator and associated electronics were calibrated in terms of energy and 
intensity of counts per minute at the ITA experimental physics teaching laboratory using radioactive sources and a 
spectrum analyzer of counts versus energy in the interval of 0,2 to 10 MeV (Millions of eléctron Volts) [7, 8]. 
 

3. Results and Discussions 
Measurements were performed between March 7th, 2017 to June 28th, 2017 at the same location shown in 

Figure 1, at the 25-meters high IAE tower [7]. The interval between each measurement was set at 1 minute. 
Therefore, it was possible to verify periods of rain and the dynamic of ionizing radiation in the region. Figure 2 
shows, during this period, 12 rains shown by the peaks of radiation increase, caused by these rains. 
  

 
Figure-2. Measurements of gamma radiation in the interval of 0.2 to 10.0 MeV (Millions of electron Volts), each 
minute between March 7th and June 28th of 2017. 
Source: Project Atmosrad 2017 



Asian Review of Environmental and Earth Sciences, 2017, 4(1): 7-11 

9 
 

 

 Examining Figure 2, there is moderate rainfall between 43 to 43.5 x 103 minutes from the beginning of the 
monitoring of the radiation series. The expansion of the graph in this region shows the detail of the occurrence of 
rainfall via measurement of ionizing radiation (gamma rays) in this range, as shown by Figure 3. 
 

 
Figure-3. Monitoring of rainfall through gamma radiation in the interval between 43 to 43.5 x 103 minutes after the start of the 
measurements. 
Source: Project Atmosrad 2017 
 

Note this monitoring of radiation in Figure 4 shows a zoom close to the interval of 72000 minutes after the 
start of the measurements, where a cold front passes through the region culminating in an intense rain caused by 
this cold front. During five days, there was a small increase of local gamma radiation, leading to an intense rain at 
the end of these five days. This established meteorological dynamic is widely observed in the region in this period 
of time between five and seven days provoking rains and cloud coverings less or more intense. The transformation 
between dose of radiation µSv/h is related to Bq/m3 of the radon gas through the gamma formula [8]: 

( / ) 0.3857 0.000866 ( / ³)Gy h Radon Bq m   , so if it is measured a dose in time the amount of radon gas in Bq/m3 

can be estimated. 
  

 
Figure-4. Interval of radiation monitoring in which there was rain between 72.0 to 72.5 x 103 minutes. 

Source: Project Atmosrad 2017 
 

During the period of 129.5 to 130.5 x 103 minutes, there were intermittent rains varying in intensity, see 
Figure 5. 
 

 

Figure-5. Intermittent rains varying in intensity, between 129.5 to 130.5 x 103 minutes. 
Source: Project Atmosrad 2017 
 



Asian Review of Environmental and Earth Sciences, 2017, 4(1): 7-11 

10 
 

 

Another moderate rainfall that altered the intensity of measured gamma radiation can be observed at ~ 141 x 
103 minutes after the start of monitoring, as shown in Figure 6. Before this rain, the local temperature rose to 300 

degrees Celsius in the day before the rain due to the arrival of a cold front coming from Southern Brazil. 
 

 
Figure-6. Moderate rainfall in the time of ~ 141,000 minutes of monitoring. 

Source: Project Atmosrad 2017 
 

Analyzing the dynamics of gamma radiation, measured from minute to minute as a function of time, at a fixed 
location, one can also observe the dynamics of the variation of rainfall occurring in the same place. Figure 7 shows 
the rainfall spectrum as a function of time measured in the same period and in the same place always with a one-
minute interval between each measurement performed. 
 

 
Figure-7. Spectrum as a function of time of rains occurred every minute between March 7th and June 28th of 2017. 

Source: Project Atmosrad 2017 

 
It is noted that the time around 43 x 103 minutes in Figure 7 corresponds to a moderate rain, observed in 

Figure 3, of radiation. Between 72 to 73 x 103 minutes, there is an intense rain, shown in Figure 7, corresponding 
to the increase of radiation seen in Figure 4. Figure 7 (intensity of rainfall in the period) can be carefully correlated 
with Figure 2 (intensity of gamma radiation in the period). Therefore, in the tropical region of Brazil due to the 
exhalation of radon gas it is possible to correlate intensity of radiation measured with local rainfall intensity 
presence. 
 

4. Conclusion 
In this work, using a simple gamma ray detector in the energy interval of 0.2 to 10.0 MeV, it was possible to 

correlate radiation measurements with rainfall measurements of the region carried out in the period of March 7th 
to June 28th of 2017. 

This positive rainfall / radiation correlation is very noticeable in the tropical region of Brazil which is certainly 
due to the presence of the decay of the Uranium 238U into Radium 226Ra and decaying into Radon gas 222Rn with 

the emission of α particles and low energy gamma radiation. Having calibrated between water intensity and the 
intensity of gamma radiation at this location, it is possible to measure the intensity of rainfall by monitoring the 
gamma radiation in the region. Another work is being done in order to show this calibration with tests carried out 
in the ITA laboratory [9]. 
 

References 
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Cultura. Suplemento, vol. 40, pp. 407, 1988. View at Google Scholar   
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nuclear-electromagnetic cascade, NASA astrophysics data system (ADS)." Retrieved from 
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gamma radiation associated with lightning and rain precipitation," presented at the 29th I, Cosmic Ray Conference, 2005. 

[6] R. Ravisankar, K. Vanasundari, A. Chandrasekaran, A. Rajalakshmi, M. Suganya, P. Vijayagopal, and V. Meenakshisundaram, 
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https://scholar.google.com/scholar?hl=en&q=Measurement%20of%20natural%20radioactivity%20in%20building%20materials%20of%20Namakkal,%20Tamil%20Nadu,%20India%20using%20gamma-ray%20spectrometry
http://dx.doi.org/10.1016/j.apradiso.2011.12.001
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http://iopscience.iop.org/journal/0031-9120

