Part I - Introduction

Area and Time Frame

The 2011 BLLAST field campaign is planned in early summer, from 14 June to 8 July 2011 in France, near the Pyrénées Mountains. The site is called "Plateau de Lannemezan", a plateau of about 200 km2 area, nearby the Pyrénées foothills, at equal distance from the Mediterranean sea and from the Atlantic ocean (about 200 km), and aligned with a main S-N oriented valley which starts to the south ("Vallée d'Aure"). The surface is covered by heterogeneous vegetation: grasslands, meadows, crops, forest.

The most favourable situations for the experiment correspond to either anticyclonic conditions, or dry post-frontal conditions. In the first case, the low troposphere is governed by the mountain-plain circulation, with a north-easterly flow over the Plateau. The CBL is either clear, or with a few rare cumulus clouds. Post-frontal conditions correspond to north-westerly winds (wind direction ranges from W to N, depending on the importance of the valley-wind relatively to the meteorological wind). They are associated with more cumulus clouds, from nicely paved (cloud streets) sky to more active post-frontal situations (with more and/or deeper clouds). Fair weather can also be encountered in foehn situation (south-westerly flow over the Pyrénées mountains), but this situation is more complex and less favourable than the two other typical situations.

Figure 1: Relief of the experimental area, with Piémont mountains to the south, and the Plateau de Lannemezan in the north (blue circled area). Super-sites 1 and 2 are indicated, as well as the flying area probed by the manned airplanes and unmanned aerial vehicles.

Figure 2: Land use (according to Corine classification) around the supersites.

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