BAMED - Balloons over the Mediterranean sea

An experimental campaign part of the HYMEX program

BAMED Balloon Technology


BAMED Boundary Layer Pressurized Balloons
Developed at CNES under the supervision of Nicolas Verdier

Contact:  nicolas.verdier@cnes.fr



Boundary Layer Pressurized Balloons (BLPB) keep a constant volume and thus fly at a nearly constant density level, acting at Lagrangian tracers of air particles and meteorological platforms. Their envelopes are manufactured by ZODIAC Int. under CNES supervision; with a 2.5 m diameter, they are made of three-laminated polyethylene of 120 microns thickness. Balloons are inflated with Helium at a nominal surpressure of 120 hPa at flight level. The balloon flight can be stopped either automatically if the balloon approaches a specific zone or by a remote command.



With a 9 Kg total mass a BLPB can fly between the surface and 830 hPa, depending of its ballast. As long as the surpressure is maintained the volume remains constant; except for small thermal fluctuations, mainly due the diurnal cycle, inducing small altitude oscillations. The most serious problem encountered by BLPB's is due to the water loading under heavy rain or when the envelope temperature is below the dew point temperature, specially by radiative cooling during night; to prevent this the BLPB envelope is treated with a hydrophobic coating.

Scientific instrumentation onboard includes pressure, humidity and temperature sensors and a 3D GPS from witch the balloon velocity can be deduced. Helium pressure and temperature are also monitored.
Meteorological data are recorded on board every 10 seconds then averaged on a time interval between 10 seconds and a few minutes; this time interval can be fixed either by remote command or automatically as a function of the vertical velocity. Data are transmitted periodically (at flight level every 20 mn) by means of the Iridium communication system.

BLBP history shared by CNES and LMD

In 1972, following the success of the EOLE experiment, during which 480 pressurized balloons were deployed at 200 hPa in the southern hemisphere, Daniel Cadet and Henri Ovarlez from the Dynamic Meteorology Lab. (LMD, Paris, France) started to study the use of pressurized balloons to analyze the atmospheric boundary layer, that is to define Boundary Layer Pressurized Balloons (BLPB).



Rangiroa balloon (1973)

Two preliminary experiments, 22 balloons launched from Rangiroa island in the southern Pacific during 1973 and 10 balloons launched from Ascencion island in the southern Atlantic during 1974, allowed to surround the difficulties of such flights (Cadet & al. 1975, J. Appl. Met, 14, pp. 1478-1484). These difficulties are linked, on a one hand to the vertical excursions due to radiative heating or cooling of the envelope, but mostly to the impact of tropical rains that may throw the balloon down to the surface. For a 2m-diameter balloon they then estimated a 500 g supplementary weight due to water loading under a shower and a dynamic pressure due to raindrops of the order of 1000 g.

The aerostat design, derived from the EOLE one, with a flight chain hung below the balloon, could not allow resisting to such events, the scientific instrumentation being destroyed when arriving at the sea surface (Rangiroa experiment). This is why it has been imagined to enclose the scientific and control gondolas inside the balloon envelope, in order that the balloon may land without damage on the ocean.

This design has been tested during the flights in Ascencion and then used for the following experiments:


Summer Monsoon experiment 1975

45 balloons launched from the Seychelles Island during 1975

ref: D. Cadet et H. Ovarlez, Quart. J. R. Met Soc, 1976, 102, pp 805-815




BALSAMINE experiment 1979

60 balloons launched from the Seychelles Island and 28 balloons from Diego-Suarez during 1979

ref: D. Cadet & al., Bull. Am. Meteor. Soc, 1981, 62, pp. 381-388

  

INDOEX experiment 1999

17 balloons launched from Goa, India during 1999

 ref: Ethe et al., J. of Geophys. Res., 107D19, 2002, INX2-22-1:19


BOA experiment 2000

8 balloons launched from Ushuaia, Argentina, during 2000

ref: Ethe, PhD Thesis, Paris 2001

VASCO experiment 2005 - 2007

VASCO 2005 (5 balloons), VASCO 2006 (4 balloons), VASCO 2007 (10 balloons) launched from the Seychelles Island

ref: http://www.lmd.ens.fr/tromeur/VASCO
Vialard et al. 2009: Cirene: Air—Sea Interactions in the Seychelles—Chagos Thermocline Ridge Region. Bull. Amer. Meteor. Soc., 90, 45–61.



AMMA experiment 2006

15 balloons launched from Cotonou, Benin, over the western Africa

ref:  http://www.lmd.ens.fr/ammabp/index.html

BLPB were designed and built entirely by the Dynamic Meteorology Lab. (LMD/Paris) up to BOA experiment.
Since VASCO they are developed by CNES, envelopes being manufactured by ZODIAC INTERNATIONAL.

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