# Study of the Diurnal Cycle of the Atmospheric Boundary Layer 

# over Salar de Uyuni.

# 

JOSE M. GALVEZ

University of Oklahoma

# 

# ABSTRACT

> The Salar de Uyuni is the largest dry salt lake in the world with a
> surface area of 3515 km^2^. It is located in the South American
> Altiplano at 3653 m MSL and centered at 20.5°S and 67.7°W. It is
> believed that the impact of Altiplano lakes and dry salt lakes
> (salars) on the weather and climate of their surrounding areas has
> been and is very large. The aim of this study is to use 5-day hourly
> pilot balloon observations at 5 sites along the salar to describe the
> characteristics of the diurnal cycle of the circulations, and to set
> hypothesis about the mechanisms involved on the behavior of the
> patterns observed.
>
> The results showed low level confluent flow over the salar during
> nighttime and low level diffluent flow during the rest of the day.
> This pattern was consistent with the theory of heat driven
> circulations induced by cool bodies during daytime, as the salar's
> surface remains cool due to its high albedo. The salar breeze
> mechanism was also captured by the observations showing late morning
> and afternoon onshore flows with depths between 600 and 1000 meters
> and return flows with depths of about 2000 meters. Offshore flows were
> also observed on late night and early morning soundings. Other
> features captured by the observations suggest that other mechanisms
> involved on the circulation may be local katabatic winds during
> nighttime, afternoon intrusions of strong winds from the western
> slopes of the Andes, the effects of boundary layer turbulent friction
> on the decrease of low level wind velocities during daytime and
> isolated effects of afternoon convection produced over higher
> surrounding the salar.

## 1. Introduction

The South American Altiplano has a large number of lakes and dry salt
lakes (salars), some of them large enough as to affect the regional
atmospheric circulation. It is known that large lakes generate various
types of mesoscale disturbances, which are driven primarily by the
surface temperature contrast (Estoque, 1980). It is also believed that
the impact of large features as Lake Titicaca or the Salar de Uyuni on
the regional circulation and rainfall patterns may be large.

The Salar de Uyuni, located in the southernmost part of the Altiplano
basin, is the largest dry salt lake in the world with a surface area of
3515 km^2^. It is centered at approximately 20.5°S and 67.7°W and at a
mean altitude of 3653 m ASL.

The salar consists on a flat highly reflective salty surface, which
results in low incoming solar radiation absorption rates, especially as
compared to the surrounding terrain. A higher thermal conductivity and
diffusivity beneath the salt surface may also interact with the high
albedo to generate low amounts of energy available for the partition of
sensible and latent heat (Physick and Tapper, 1990). These mechanisms
produce diurnal surface temperature contrasts between the salar and the
surrounding terrain, which results in the production of salar breezes
during the day, and terrain breezes during the night.

The aim of this study is to describe the characteristics of the diurnal
cycle of the atmospheric circulations over the Salar de Uyuni and to set
hypothesis about the mechanisms involved in the behavior of the observed
patterns. Specifically we want to describe the strength, vertical
extension, and diurnal cycle of the breezes, as well as other mechanisms
involved in the regional circulation patterns. It is also intention of
this study to infer the role of the salar in the spatial distribution of
rainfall in the surrounding areas.

Due to the limitations of observational data and time, this
investigation was able to describe only the time and vertical variations
of the winds at 5 sites located among the salar. This paper poses many
research questions that may be partly explained in a more complete
study.

## 2. Dataset and methodology

The data used in this study was gathered during the South American Low
Level Jet Experiment (SALLJEX). The Salar de Uyuni Experiment formed
part of SALLJEX with the goal to investigate the role of Altiplano lakes
and dry salt lakes in the amount and distribution of rainfall on the
surrounding areas. The intensive observations period (IOP) started in 25
November 2002 and ended in 30 November 2002.

Hourly wind profiles made over a five-day period were used for the
analysis. These profiles were obtained by pilot balloon soundings at
five sites located along the salar. Four of the sites were located near
the edges and one near the center. The main observational network
deployed is shown in Fig. 1.

The methodology utilized on this study was focused on the depiction of
the diurnal cycle. All the data was first edited to correct errors in
the raw observations. Five-day hourly averages of the wind profiles were
then performed for each site. Anomalies of these profiles were also
utilized. They were achieved by subtracting the total averaged wind
profile for all sites to each hourly average, which removed the mean
flow. This technique improved the local circulation analyses.

The data set showed many problems still due to the lack of observations
at specific times for specific sites, which resulted in a source of
errors when calculating the means. Other problems resulted from
measurement errors, which were sometimes hard correct. The east site
showed the most contaminated data of all sites, resulting in unreliable
profiles. The data set still needs to be corrected and the averages
recalculated in order to achieve a more reliable study.

## 3. Synoptic conditions

## 

We will briefly describe the large-scale flow pattern in order to
provide some background for interpreting the results.

Easterly and northeasterly 500 mb flow (Fig. 2) was observed at the
beginning of the observation period. This type of circulation aloft
generates downward momentum flux into the convective boundary layer and
tends to accelerate the upslope flow over the eastern slopes of the
Andes, which in turn increases the low-level moisture transport from the
lowlands into the Altiplano (Garreaud, 2000). This pattern was favorable
for the development of isolated deep convection during the first two
days of the observing period.

![](media/image1.jpeg){width="3.66875in" height="2.9097222222222223in"}

> Fig. 1. Satellite image of Salar de Uyuni showing the distribution of
> the station network and some important features to take into account.

The upper level circulation changed towards the end of the experiment
resulting in westerly winds over most of the Altiplano (Fig. 3) due to
an approaching trough. This type of upper level flow resulted in drier
conditions as moisture transport from the east was constrained to the
eastern slope and the Altiplano was flooded by dry air originated on the
western foothills of the Andes (Garreaud, 2000).

![](media/image2.jpeg){width="2.595833333333333in"
height="2.4583333333333335in"}

Fig. 2. 1100 UTC 26 November 2002 Streamline analysis performed using
SALLJEX Pilot Balloon Data.

![](media/image3.jpeg){width="2.595138888888889in"
height="2.4493055555555556in"}

Fig. 3. 1100 UTC 29 November 2002 Streamline analysis performed using
SALLJEX Pilot Balloon Data.

## 

## 4. Description of the wind field

Five-day averaged wind data were utilized to prepare 200 m AGL
streamline analyses (Fig. 4). They showed the presence of confluence
over the salar at midnight meanwhile diffluent flow was present during
the day.

The same data suggested the presence of onshore circulations during late
morning and afternoon extending between 500 and 1300 m in the vertical.
Weaker offshore circulations were also observed during late night,
however, they were not well described due to the lack of observations
during nighttime. These breezes apparently extended as far in the
vertical as the diurnal onshore breezes. Strong westerly winds were
observed in the afternoon, especially on the West and COPS sites.
Hypothesis about the origin of these winds will be described later.
Storm outflow winds were also observed on the 26^th^, however, this data
was extracted for the calculation of the mean as these winds had
relative speeds of the order of 10 m/s but the event was very isolated
in time and space.

The upper level flow was consistent with the SALLJEX Network soundings
showing weak easterly, northerly and northwesterly winds at the
beginning of the period changing to stronger westerly winds towards the
end of the period at 500 mb. The flow above 350 mb was from the
northwest during the entire period with a stronger westerly component
towards the end of the experiment.

Lower level winds showed some sensitivity to the upper level pattern.
During periods of weak 500 mb winds the presence of the breezes was very
clear, whereas during days of stronger 500 mb winds the flow at lower
levels was mainly from the west. A considerable increase in velocity of
the low level afternoon westerly winds was also observed towards the end
of the period. All these observations suggest the presence of downward
transport of momentum, which intensified as the upper level wind
velocities increased.

> ![](media/image4.jpeg){width="3.0027777777777778in"
> height="2.7493055555555554in"}
>
> ![](media/image5.jpeg){width="3.0027777777777778in"
> height="2.7666666666666666in"}
>
> ![](media/image6.jpeg){width="3.0027777777777778in"
> height="2.772222222222222in"}
>
> ![](media/image7.jpeg){width="3.0027777777777778in"
> height="2.7493055555555554in"}
>
> Fig. 4. Five-day averaged wind field at 0000 LST (a), 0600 LST (b),
> 1200 LST (c) and 1800 LST (d).

**5. Discussion**

The persistence of low-level diffluent flow as compared to confluent
flow over the salar may have to do with the fact that the salar remains
cooler than the surrounding terrain for a larger percentage of the day.
GOES-8 Infrared images (Fig. 5) could be used to support this
hypothesis, as surface temperature measurements were not performed other
than in the salar. The fact that late November sunrises occur at 0545
LST may also promote the nocturnal land breeze mechanism to start
breaking down before 0600 LST, favoring an early setup of the low level
diffluent flow, however, we cannot pose a hypothesis until the
calculation of divergence is performed.

Fig. 6 illustrates the theoretical relationship between the breezes and
the boundary layer, where the boundary layer top should correspond to
the highest crossing between the late night wind profile and afternoon
one. The average depth of the observed mixed layer, however, was not
easy to identify using the wind profiles. An analysis of the
five-day-averaged wind anomaly profiles showed that the secondary
crossing of the morning profile with the afternoon profile occurred at
about 3000 m AGL. Considering that this altitude corresponds to a
pressure surface of approximately 420 mb, we would agree with the
results of Garreaud (2000) who documented that the average depth of the
Altiplano mixed layer reaches 450 mb in average. It is important to
consider that late November solar radiation is above the average due to
the position of the sun. The solar zenith angle reaches values close to
0° around November the 20^th^ over the salar. This may explain why the
observations showed slightly deeper hypothetical boundary layers.

![](media/image8.jpeg){width="3.1180555555555554in" height="1.775in"}

Fig. 5. 30 November 2002 GOES-8 IR4 Satellite images centered over the
Salar de Uyuni.

After removing the large scale flow, our results showed circulation
patterns that could be related to six hypothetical mechanisms: Salar
breezes, anabatic/katabatic winds, upslope winds from the Pacific basin,
diurnal boundary layer turbulent friction effects, downward transport of
momentum from the upper troposphere, and isolated convection effects.

![](media/image9.jpeg){width="3.122916666666667in"
height="1.6395833333333334in"}

Fig. 6. Scheme showing the salar-terrain breeze mechanism induced by the
Salar de Uyuni, and a theoretical relationship with the boundary layer
and a profile of wind anomalies.

a.  *Salar breezes*

The salar-breeze mechanism was hard to depict in some sites partly due
to errors in the data, and partly due to the presence of other
mechanisms not well understood yet. Most of the locations showed a clear
signal, however, especially the South, West and COPS sites. These
results will be discussed, and the information obtained in the central
site will be compared with the one obtained in the sites located near
the edges of the salar.

Fig. 7 is an excellent example of the salar breeze mechanism. It shows
the anomalies of the five-day-averaged meridional wind profiles at 3
different times of the day for the South site. A strong onshore breeze
can be observed by early afternoon reaching northerly wind anomalies of
almost 10 m/s at about 100 m over the surface. The vertical extension of
this breeze is 1000 m AGL, which is confirmed by the late afternoon
profile, even though by this time the breeze has weakened significantly.

![](media/image10.jpeg){width="2.9993055555555554in"
height="2.8152777777777778in"}

Fig. 7. Anomalies of the 5-day-averaged meridional wind (m s^-1^)
observed at the South site. The thin line with asterisks indicates the
early morning wind anomalies, the thick dark line indicates the early
afternoon wind anomalies and the dashed line indicates the late
afternoon wind anomalies.

The return flow associated to the breezes is also apparent in this plot,
occurring between 1000 and 3000 m AGL. It corresponds to a broader and
weaker layer of winds.

It is important to notice that the mean flow anomaly is in average from
the north along the lowest 3000 m suggesting again the presence of a
prevailing diffluent flow at lower levels. The anomaly becomes from the
south over this level suggesting possible presence of salar-induced
circulation at larger spatial scales.

The diurnal cycle of the breezes observed in the South site can be best
described using Fig. 8. The onshore flow appears after 0900 LST at lower
levels and quickly expands in the vertical reaching depths above 1 km at
1100 LST. The depth of the flow starts to decrease after 1400 LST
merging with the strong westerly flow observed at all sites during late
afternoon. In this case this flow is weaker in comparison with the West
and COPS site, and decays around 2000 LST. Even though the number of
nighttime observations was very reduced, low level offshore flow was
also observed at 0200 LST.

![](media/image11.jpeg){width="2.714583333333333in" height="2.21875in"}

> Fig. 8. Anomalies of the 5-day-averaged wind (m s^-1^) observed at the
> South site. The data has been plotted utilizing wind barbs and in an
> hourly fashion. The hypothetical regions of breezes have been shaded
> for the salar-type breeze (A), land breeze (B), and strong afternoon
> westerlies (C).

For an analysis of the breezes observed at the West site, Fig. 9 shows
the anomalies of the five-day-averaged zonal flow. The depth of the
breezes is similar to the depth observed at the South site, with a
higher standard deviation. The point of inflexion of the wind profiles,
however, is not as obvious as compared to the South site results. It can
be anywhere in between 700 and 1600 m. The area of return flow is not
clear as well.

It is also important to notice a tendency of the mean flow anomaly to be
onshore between 500 and 3000 m, which would again suggest the presence
of larger spatial scale circulations induced by the salar with an
inflexion point near 3 km. This observation is a result of subtracting
the mean calculated with data from all the stations instead of using a
mean calculated with data of each station. The observation of this large
3000 m AGL deep circulation induced by the salar is consistent with the
South site observations.

The late afternoon wind profile, however, differs from the tendencies
noticed on the other ones. A sudden increase on the wind velocities in a
700 m layer close to the surface modifies the rest of the profile,
apparently due to conservation of momentum. Notice that the areas held
by each curve on both the positive and negative regions of the plot
appear to be similar. This change in the profile may be attributed to
the incursion of upslope winds from the Pacific Basin located to the
west, hypothetical mechanism that will be described later.

![](media/image12.jpeg){width="2.935416666666667in"
height="2.7805555555555554in"}

> Fig. 9. Anomalies of the 5-day-averaged zonal wind (m s^-1^) observed
> at the West site. The thin line with asterisks indicates the early
> morning wind anomalies, the thick dark line indicates the early
> afternoon wind anomalies and the dashed line indicates the late
> afternoon wind anomalies.

The diurnal cycle of the breezes observed at the West site is described
in Fig. 10. The onshore breeze mechanism develops after 0900 LST rapidly
reaching depths of the order of 1200 m AGL. This mechanism persists
until late afternoon. After 1500 LST a strong westerly flow incursion of
a depth of 700 m reaches the location, becoming persistent even after
sunset. The lack of nighttime pilot balloon observations resulted on a
gap between 2000 LST and 0500 LST when strong and very shallow westerly
winds were observed. This strong late night-early morning flow was not
observed at the other sites. A very large temperature gradient between
the salar and the terrain to the west of it could explain a terrain
breeze characterized by +8 m/s anomalies. The late night temperature
gradients between the terrain and the salar, however, seemed to be
larger at the eastern edge of the salar in comparison with the western
edge, as suggested by the GOES-8 IR4 Satellite image of 0445 LST, 30
November 2002 (Fig. 6). Assuming that the satellite image is accurate
enough in depicting surface temperature gradients, there should be
another mechanism involved on the generation of such strong winds.
Katabatic winds could be playing an important role, as sloping terrain
can be found very close to the West site. These winds, however, could be
originated at the cold tops of the western ridge located at 30 km to the
west of the salar.

> ![](media/image13.jpeg){width="2.745138888888889in"
> height="2.2333333333333334in"}
>
> Fig. 10. Anomalies of the 5-day-averaged wind (m s^-1^) observed at
> the South site. The data has been plotted utilizing wind barbs and in
> an hourly fashion. The hypothetical regions of breezes have been
> shaded for the salar-type breeze (A), land breeze (B), the strong
> afternoon westerlies (C), and the probable katabatic wind contribution
> (D).

A breeze analysis was also performed for the COPS site. Even though this
site was located close to the center of the salar, it also showed a
breeze signal. Fig. 11 shows the anomalies of the early morning zonal
wind versus the early afternoon and late afternoon zonal wind at this
location. A comparison between the first two curves reveals the presence
of an easterly breeze with a shallow depth of about 400 m AGL and a
broad return flow of an approximate depth of 2100 m. These results
suggest that this site was located to the west of the breeze source
region. This may be consistent with the fact that the widest portion of
the salar is closer to the eastern side than to the western one.

![](media/image14.jpeg){width="3.084722222222222in"
height="2.838888888888889in"}

> Fig. 11. Anomalies of the 5-day-averaged zonal wind (m s^-1^) observed
> at the COPS site. The thin line with asterisks indicates the early
> morning wind anomalies, the thick dark line indicates the early
> afternoon wind anomalies and the dashed line indicates the late
> afternoon wind anomalies.

The diurnal cycle of the COPS site profiles is shown in Fig. 12. The
salar breeze develops around 0900 LST, immediately reaching the maximum
depth around 600 m. This breeze remains almost steady in depth and
intensity until the strong westerly flow arrives after 1500 LST. This
flow reaches its maximum intensity at 1900 LST, just after sunset. The
flow persists during the evening and after midnight merges with the
terrain breeze (C/B), making it hard to distinguish between these two. A
period of transition occurs between 0600 LST and 0800 LST when solar
radiation starts to heat the surrounding terrain inverting the sensible
heat gradients.

It should also be noticed that the breezes observed at the COPS site are
shallower than the ones observed on the sites located near the edges of
the salar.

b.  *Anabatic / katabatic winds*

Although there were no strong arguments yet to explain the presence of
these winds, theoretical studies complemented with results observed on
the west site suggest their contribution to the regional circulation.

# ![](media/image15.jpeg){width="2.692361111111111in" height="2.1902777777777778in"}

> Fig. 12. Anomalies of the 5-day-averaged wind (m s^-1^) observed at
> the COPS site. The data has been plotted utilizing wind barbs and in
> an hourly fashion. The hypothetical regions of breezes have been
> shaded for the salar-type breeze (A), land breeze (B), strong
> afternoon westerlies, (C) and an unclear interphase between C and B
> (C/B).

The anabatic / katabatic wind mechanism is also known as the valley /
mountain breeze mechanism. It has the same physical initiation as a lake
or salar breeze : A horizontal variation in the sensible heat flux near
the ground. It produces downslope winds during the night and upslope
winds during the day. The requirement for this type of breeze to occur
is the presence of gradients in the topography.

Overall, the west site had the closest location to a mountain chain
(Fig. 1), which is the western ridge of the Andes. This feature is
located at 30 km to the west of the site and showed a significant
surface cooling during nighttime (Fig. 5). The presence of valleys
connecting the ridge with the West site region could help to transport
the katabatic winds into the salar. Fig. 9 shows +8 m/s zonal flow
anomalies during early morning hours. This is also reflected on the 0600
LST streamline analysis in Fig. 4b. These results may suggest the
presence of a strong decaying terrain breeze, as the surface sensible
heat gradient should be changing sign due to solar radiation.

There could also be a mountain channeling effect on the flow, which
would induce an acceleration. This could also explain the strong early
morning winds observed on the West site.

c.  *Upslope winds from the Pacific Basin.*

Unexpected and long lasting shallow strong westerly winds were observed
every late afternoon and evening over the five sites, being particularly
strong at the central and western site. Wind velocities generated were
of the order of 15 to 20 m/s at 200 m AGL. These winds had a depth of
about 700 m when entering the basin and near 1000 m when flowing over
the central site. The signal of these winds was less evident on the rest
of the sites, but still present.

A hypothesis was posed about the possible origin of these winds being
the upslope flow along the western slope of the Andes. Ye, Segal and
Pielke (1987) found that the intensity of the upslope flow increases
linearly with the amount of heat energy injected at the surface into the
PBL, and also increases linearly with respect to the sine of the slope.
Strong solar radiation and very dry soil conditions on the area may
enlarge the sensible heat flux differences within the western slopes
region boundary layer. In addition, the topographic transition between
the Atacama Desert and the Altiplano is very sharp, with terrain changes
sometimes larger than of 3km on the vertical versus 30 km on the
horizontal. Finally, the presence of a strong diurnal contrast between
the cold Pacific Ocean and the dry soil of the Atacama Desert could
generate strong sea breezes, which could feed the upslope wind,
enhancing even more the wind speeds. The combination of the mentioned
factors could produce very strong upslope winds, which would reach their
maximum speeds near the upper edge of the slope (Ye, Segal and Pielke,
1987). After reaching this edge, the winds would encounter a flatter
terrain and propagate through the valleys onto Salar the Uyuni. When
reaching the salar, small roughness lengths would help the flow to
conserve its momentum and easily propagate in straight line over larger
distances.

d.  *Surface and boundary layer turbulent friction*

Boundary layer friction during daytime might be responsible for the
decrease of the wind velocity within the boundary layer. During
nighttime, however, the lower atmosphere tends to be stably stratified
and less friction is applied to the flow. This promotes an acceleration
of the flow as compared to daytime observations, which was observed at
COPS site in particular.

Surface friction is also an important factor on the wind velocity. The
surface of the salar is so smooth that creates a smooth wall flow. This
allows the flow to propagate rapidlly and to conserve its
characteristics over large distances. This may also explain that the
strong westerly flow with a zonal anomaly of 8 m/s conserved its
momentum reaching the central site with a zonal anomaly of 6 m/s.

e.  *Downward transport of momentum*

The upper level flow over the Altiplano has an important role on the
circulation near the surface. Large-scale upper level easterly flow
produces a turbulent entrainment of easterly momentum over the Andean
ridge, thereby accelerating eastward upslope flow and moisture transport
(Vuille, 1999; Garreaud, 1999).

It was found by the observations that during the last days of the
experiment the magnitude of the afternoon westerly flow increased
significantly in contrast with the first days. This may be related to an
acceleration of the upslope flow due to entrainment of westerly momentum
over the ridge, posing an analogy to the argument suggested by Garreaud
(1999) and Vuille (1999).

f.  *Isolated effects of convection*

Western Altiplano convective events occur only during periods of daily
moisture influx from the eastern interior of the continent (Garreaud,
1999; Garreaud, 2000; Vuille, 1999), which are less common than periods
of dry air intrusion from the west. Being consistent with these
observations, convection was present only during the first two days of
observations, when the main zonal component of the 500 mb winds was
easterly. The rest of the period was characterized by westerly flow and
very dry conditions.

A convective storm that developed on November the 26^th^ over Tunupa
Volcano, about 10 km to the north of the north site, generated an
outflow boundary which propagated towards the south along the salar.
This flow was first captured by the north station producing a change on
the meridional wind of -7.5 m/s in one hour, from 0.7 m/s southerly
winds at 1700 LST to 6.8 m/s northerly winds at 1800 LST.

The winds associated to the storm on the 26th were removed for the
calculation of the five-day means, as previously mentioned, due to the
isolated characteristic of this event.

**6. Concluding remarks**

The prevailing flow over Salar the Uyuni was diffluent during the day
and confluent near midnight. Divergence calculations are recommended in
order to depict the effects of the salar in vertical circulations, as
this study performed a two-dimensional analysis solely.

The results indicated the presence of onshore breezes with a depth
between 700 and 1500 m AGL on the stations located near the edges of the
salar, and a slightly shallower breeze with a vertical extension between
500 and 1000 m ACL near the center of the salar. These circulations may
suggest the presence of subsiding flow over the salar, which would be
responsible for the shallower breezes observed in the central site.

Offshore breezes with a similar depth than the onshore ones were also
depicted. These breezes, however, appeared to be deeper at the central
station as compared to the surrounding stations. This could also suggest
the presence of a deeper nocturnal boundary layer that could be
associated to rising motions over the salar. This needs to be
complemented with divergence calculations though, besides that the lack
of nighttime observations becomes a limitation on the interpretation of
these results.

Six mechanisms involved on the circulation patterns observed over Salar
de Uyuni may be the salar-breeze mechanism, the anabatic-katabatic wind
mechanism, the afternoon incursion of strong westerly shallow winds
originated in the western slopes of the Andes, the effects of boundary
layer friction on the diurnal flow, downward transport of momentum from
the upper troposphere, and isolated effects of convection in the form of
local outflow boundaries.

REFERENCES

**Estoque M. A. and J. Gross, 1978** : Diurnal Wind and Temperature
Variations over Lake Ontario. *Mon. Wea. Rev*., 104, 1742-1747.

**Estoque, M. A. and J. Gross, 1980**: Further Studies of a Lake Breeze
Part I: Observational Study. *Mon. Wea. Rev*., 109, 611-618.

**Garreaud, R. D., 1999** : Multi-scale analysis of the summertime
precipitation over the Central Andes'. *Mon. Wea. Rev*., 127, 901-921.

**Garreaud, R, 2000** : Intraseasonal Variability of Moisture and
Rainfall over the South American Altiplano. *Mon. Wea. Rev*, 128,
3337-3346.

**Physick, W. L. and N. J. Tapper, 1990**: A Numerical Study of
Circulations Induced by a Dry Salt Lake. *Mon. Wea. Rev*., 118,
1029-1041.

**Vernekar, K. G., B. Mohan, S. Saxena and M. N. Patil, 1993** :
Characteristics of the Atmospheric Boundary Layer over a Tropical
Station as Evidenced by Tethered Balloon Observations. *Journal of
Applied Meteorology*, 32, 1426-1432.

**Vuille, M., 1999**: Atmospheric Circulation Over the Bolivian
Altiplano During Dry and Wet Periods and Extreme Phases of the Southern
Oscillation. *International Journal of Climatology*., 19, 1579-1600.

**Ye, Z. J., M. Segal, and R. A. Pielke, 1987**: Effects of the
Atmospheric Thermal Stability and Slope Steepness on the Development of
Daytime Thermally Induced Upslope Flow. *Journal of the Atmospheric
Sciences*., Vol. 44, N°22, 3341-3354.

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