Atmospheric and Climate Sciences, 2012, 2, 518-524
http://dx.doi.org/10.4236/acs.2012.24046 Published Online October 2012 (http://www.SciRP.org/journal/acs)
Interannual Variability of Energy Flux in Atmospheric
Instability Conditions at Pantanal of Mato Grosso-Brazil
Leone Francisco Amorim Curado, José de Souza Nogueira, Luciana Sanches,
Marcelo Sacardis Biudes, Thiago Rangel Rodrigues
Programa de Pós-Graduação em Física Ambiental-UFMT, Brazil
Received July 25, 2012; revised August 27, 2012; accepted September 7, 2012
ABSTRACT
The energy balance partitions in wetlands have gained notoriety due to the dynamics and importance of these areas for
regional and local climate. Thus, the study was conducted about seasonal and interannual behavior energy fluxes, as
well as the influences of the conditions of atmospheric stability and instability. The results showed highest fluxes
happened in instability atmospheric conditions. The fluxes of latent and sensible heat showed seasonal variation,
indicating that the water availability in the atmosphere has influence on the site energy partition, but the interannual
patterns remained similar during the two years of study.
Keywords: Latent Heat; Sensible Heat; Energy Partition; Wetlands
1. Introduction
The flood pulse is considered the driving force of the
Pantanal and the intensification of the season of dry and
wet seasons are the result of multi-annual fluctuations in
water level that influence the limnological seasonal char-
acteristics, ecological and biological [1]. October months
are the rains begin and it finish between February and
May, July and August are characterized as dry months in
this region, often causing hidric stress to the plants [2].
Vochysiadivergens is considered an invasive species
in Pantanal having a good adapting in flood area. This
species incursion in the Pantanal happened in the early
70 s, after the end of an intense and multi-annual period
of dry [3]. In not flooded areas the presence of Vochy-
siadivergens is rare or absent, but present a better devel-
opment in newly sedimented areas along rivers [4]. In
wetlands, there is no problem with this species, but when
it reaches the highest parts of Pantanal and advancing
toward fields forming forests, it becomes a problem, be-
cause it occupies Pasture areas [5].
The apparent cause of the spread of the species in the
region may be related to the alternation of major floods
and droughts that occur in the Pantanal and also by de-
forestation caused by livestock farmers in the region,
increasing the area available for the plant to establish.
These factors can cause shrinkage of native vegetation
and increases in populations of this species, giving the
vegetation an irregular character in time and space than
may lead to short and medium term changes in Pantanal
region climate [3].
The flux of latent and sensible heat can be obtained by
micrometeorological methods, direct and indirect (esti-
mated), the last one having the advantage of not altering
the environment. For direct measurement methods has
the eddy covariance system, which takes into considera-
tion the fluctuation of the concentration of water vapor,
temperature and fluctuation of wind speed to calculate-
ing the flux and latent heat sensitive respectively [6,7].
The advantage of using direct measures is that small fluc-
tuations in very low intervals of time are obtained, the
disadvantage is the value for the acquisition of the equip-
ment.
The LE and H quantification by Bowen ratio method
have been widely used in the last decade, for determining
the energy balance in many studies about the energy dy-
namics of forest and the management availability of wa-
ter for certain crops by evapo transpiration estimated by
the latent heat flux [8-12].
The atmospheric stability can be defined as a condition
in which atmospheric air upward movements are absent
or permanently inhibited, whereas the condition of insta-
bility is defined as the atmospheric state in which prevail
the vertical movements. The characterization of these
atmospheric conditions is realized according to the tem-
perature distribution of air, i.e., an air layer is considered
stable or unstable depending on the value of vertical
temperature gradient observed in the layer. It should also
consider the situation in which the vertical temperature
C
opyright © 2012 SciRes. ACS

L. F. A. CURADO ET AL. 519
gradient in the atmospheric layer coincides with the rate
dry adiabatic. In such condition, the air parcel to ascend
or descend will always have the same temperature of the
medium that it surrounds, without resistance nor further-
ing of the vertical movement of the air layer, featuring
neutral atmospheric condition [13].
The objective of this work was to study the seasonal
behavior of the energy fluxes for stability and instability
atmospheric conditions in an area of Vochysiadivergens
at Pantanal of Mato Grosso-Brazil.
2. Materials and Methods
2.1. Study Area
The study was conducted in an area located in the Private
Reserve of Natural Heritage—PRNH SESC—Pantanal,
in Barão de Melgaço city—MT, distant 160 km from
Cuiabá—MT where a micrometeorological tower was
installed at 32 m in height (16˚39′50″S, 56˚47′50″W)
and120m level. This area has a mono-dominate vegeta-
tion of Cambará (Vochysiadivergens, Phol), Known lo-
cally as cambarazal, with canopy heights ranging from
28 to 30 m (Figure 1).
2.2. Measurements
The net radiation was measured for one net radiometer
(Kipp&Zonen Delft, Inc., Holland), and the heat flux in
soil was measured by two fluxímeters (HFT-3.1, REBS,
Inc., Seattle, Washington) installed at 0.05 m e 0.25 m
depth. The gradients of temperature and humidity were
estimated by two thermohygrometer (HMP 45 C, Vaisala,
Inc., Helsinki, Finland) installed at 33.7 m e 37.7 m
height in micrometeorological tower.
2.3. Methods
Atmospheric stability (ξ) was calculated using two meth-
ods (Equations (1) and (2)).
*3
0,4
pk
g
zH
cTu
  (1)
where, g is the gravitational acceleration (9.8 ms–1), Tk is
the air temperature (K), u* is the velocity of air friction
(ms–1), ρ is the air density (1.292 kg·m–3), cp is the
specific heat of the humid air (1013Jkg–1·C–1), H is the
sensible heat flux where z is the height was measured
wind speed.
Figure 1. Localization of the micrometeorological tower in the RPPN-SESC Pantanal in MatoGrosso-Brazil.

L. F. A. CURADO ET AL.
520
The sensible (H) and latent (LE) heat fluxes were
calculated according to Equations (2) and (3), respec-
tively.

1
n
H
RG






v 
(2)

1
n
RG
LE

 




(3)
Where Rn is net radiation, G is the soil heat flux and β
is the Bowen ratio, given by:
T
e




(4)
where Δt is difference temperature between two levels
3. Results and Discussion
ondition and ux
Tab ric
as noted that the highest
va
es of seasonal latent heat in the
rai
energy into latent and sen-
si
ric conditions
sh
Table 1. showsthe daily average values of atmospheric cond-
(˚C), the difference Δe pressure of water vapor between
two levels (kPa) and the constant γ psychometric (0.0626
kPaC–1).
3.1. Seasonality of Weather C
Patterns of Latent and Sensible Heat Fl
le 1 shows the daily average values of atmosphe
conditions (stability and instability) and the latent heat
and sensible in the study area.
According to Table 1, it w
lues of the latent heat and sensible occur with atmo-
spheric in stability, which is because in unstable cond-
itions conducive to turbulence that is the most favorable
condition for energy transferring and matter between
surface and atmosphere.
The daily average valu
ny season were higher than in the dry, which also
resulted in an increase in the sensible heat flux during the
dry period, indicating that the water content due to the
precipitation region is a factor determining the amount of
energy from the sun which is used to evaporate the water
and increased temperature.
This conversion of solar
ble heat is critical for the regulation of ecosystems.
According to [14], temperature and humidity conditions
within and above a forest are the result of transmission
and absorption of solar energy on the surface of the
canopy, its conversion into sensible and latent heat and
the allocation of light and heat in a forest.
The average daily values of atmosphe
owed that both stability and instability remained
approximately the same values in both periods (rainy and
dry) during the two years studied (2007 and 2008), which
indicates a weather regulation in the region of the study.
itions (stabilityand instability) and the latent heat and
sensible in the study area.
2007 2008
Wetseason Instability maximum −0.11 −0.22
Staity
mi
LE—U stable
mi −
LE—able
mi
H—Utable
mi
H—able
mi
Dryseason Instability
mi
Staity
mi
LE—U stable
mi −
LE—able
mi
H—Utable
mi −
H—able
mi
minimum −0.61 −0.60
mean −0.40 −0.39
bilmaximum 0.16 0.09
nimum −0.01 −0.01
mean 0.05 0.03
nmaximum 547.04 454.49
nimum 51.02 41.08
mean 306.42 280.57
Stmaximum 94.74 109.05
nimum −34.82 −21.6
mean 0.3 15.94
nsmaximum 111.54 107.94
nimum 9.72 −6.82
mean 59.73 61.48
Stmaximum 18.54 22.31
nimum −7.47 −3.36
mean 0.76 3.96
maximum −0.18 0.15
nimum −0.57 −0.62
mean −0.37 −0.36
bilmaximum 0.09 0.11
nimum −0,02 −0.01
mean 0.01 0.02
nmaximum 348.47 352.96
nimum −7.4 46.01
mean 234.02 216.03
Stmaximum 60.42 77.23
nimum −39.93 −37.91
mean 0.57 4.9
nsmaximum 118.83 149.26
nimum −1.41 7.76
mean 58.57 66.02
Stmaximum 15.68 23.06
nimum −15 −14.91
mean 0.33 0.7
3.2. Inter-Annual Variabil Wea
Conditions and Patterns of Latent and
The t the
eneron average
ity ofther
Sensible Heat in the Rainy Season
values in Table 1an d Figure 2 indicate tha
gy converted into latent heat flux was
higher than the energy converted into heat sensitive
within two years of study during the rainy season, except
on condition of stability of the year 2007, which indicates
that the amount of water present in the atmosphere is a

L. F. A. CURADO ET AL. 521
regulating agent of the ecosystem in question, this result
was found by [2].
Another important factor is that in analyzing inter-an-
nual patterns in atmospheric conditions (stability and
in
her
Conditions and Patterns of Latent and
Acco y
perioy most of the
stability) were between one year and one which also
occurred with the latent heat and sensible, who have
followed these conditions, with higher instability values
than the stability in the two years of study, thus
indicating that during the wet season of 2007 and 2008
standards in these variables kept the same.
3.3. Inter-Annual Variability of Weat
Sensible Heat in the Dry Season
rding to Figure 3, it was noted that as in the rain
d between the study period, in the dr
available energy to the ecosystem was converted into
latent heat, showing that even in periods with little or no
precipitation the evaporative requirement is relatively
high compared with the sensible heat flux, demonstrating
that the latent heat flux is the main component of the
energy balance in this region.
The same to the rainy season, the highest values of
latent heat flux and sensible culminated with the
conditions of atmospheric instability, which as already
mentioned in Section 3.1, this condition favors the turbu-
lence that promotes the energy transfer between the
surface and atmosphere through the fluxes of latent and
sensible.
Another important factor is the greater variability of
the data sensible and latent heat flux in the dry season
than in rainy season in both years studied, this is caused
Wet season - 2008
Wet season-2007
Atmosph erics conditions
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8 Unstability
Stability
Latent heat flux (W .m
-2
)
LE - Unstable
LE - Stable
-100
0
100
200
300
400
500
600
Days
0 102030405060708090
Sensible heat flux (W.m
-2
)
-20
0
20
40
60
80
100
120
140 H - Unstable
H - Stable
0 102030405060708090
Days
Figure 2. Daily average values of conditions atmospheric stability, atmospheric instability and flux of latent and sensible heat
during the wet season in the years 2007 and 2008.

L. F. A. CURADO ET AL.
522
Dry season- 2007Dry season - 2008
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
Unstability
Stability
Atmospherics conditions
Latent heat flux (W.m
-2
)
LE - Unstable
LE -Stable
-100
0
100
200
300
400
Days
0 102030405060708090
Days
0 102030405060708090
Sensible heat flux (W .m
-2
)
H - Unstable
-50
0
50
100
150 H - Stable
Figure 3. Daily average values of conditions atmospheric stability, atmospheric instability and flux of latent and sensible heat
during the dry season in the years 2007 and 2008.
mosphere
, drier air and lower radiation
[17].
reported in the Cerrado and Amazon transition forest-
hest values of energy flow by favoring the
between the surface and atmosphere
by the fact that there is greater variation in temperature in
e region due to low water content in the at
Lower values of LE, during the dry period, were also
th
and also for this period include the winter season than in
the southern hemisphere occurs between June and Sep-
tember, which causes abrupt changes in temperature, thus
causing a greater variability in the energy flux data. This
greater variability in temperature data during the dry
period is described in [15].
Lower values of LE during the dry period can be expl-
ained by lower temperatures
(winter solstice), and is a limiting feature of this water at
this station canopy. During the dry season, there is a
decline in water content in soil and can limit evaporation
and water availability for plant root surface [16]. How-
ever, higher values of evapotranspiration in the wet season
were related to increased rainfall and flood water depth
savanna in the Midwest, while in tropical rain forests
located in Manaus, Santarem and Rondonia citywere
reported lower values of evapotranspiration during the
wet season [18,19].
Thus, the partition of energy in the Pantanal regions is
strongly influenced by water availability in soil and
atmosphere and the conditions of instability and stability
atmospheric.
4. Conclusions
Latent and sensible heat flux was influenced by weather
conditions in the region, and the condition of instability
caused the hig
transport of energy
through turbulence.

L. F. A. CURADO ET AL. 523
The most of available energy were converted into
latent heat in the two years of study, showing that the
water content is a regulatory agency in the region.
The variables studied (instability, stability, latent heat
and sensible heat) showed similar patterns for the same
pe
ntífico e Tecnológico (CNPq)
Amparo a Pesquisa do
MAT) through the Support
anadian Special Publication of Fisheries and Aquatic
Sciences, Otta
riod, the interannual analysis.
Water availability and season influenced the parti-
tioning of energy of site.
5. Acknowledgements
The authors thank Coordenação de Aperfeiçoamen to de
Pessoal do Ensino Superior(CAPES), Conselho Nacional
de Desenvolvimento Cie
for Scholarship and Fundo de
tado de Mato Grosso (FAPE
Es-
Program for Centers of Excellence (PRONEX) for finan-
cial support to the research project process No. 823971/
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