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I I I I I I I I I I I I I I I I I I I 8 prevailed, the sounding \"as obtained on the approach to landing at ^lamosa. 3. Research area Fig. 2.2 is a map of the research area. The three airports at Alamosa (ALS), Farmington CHlN), and Durango (DRO) are sho\.Jl1. The primary target area was upwind of Wolf Creek Pass. Other locations mentioned in the text are shown on the map. 4. Typical f~ht plan A typical flight plan contained an upHind and a dm.Jl1wind flight over Holf Creek Pass from Del Norte to Wolf Creek Pass to Pagosa to Navajo Reser- voir. The upHind flight was directed along this path and at cloud top level or near 500 mb if the tops of the clouds over the mountain were above 500 mb. The up\dnd flight \vas flm.Jl1 at these high levels because if lee waves or dmmdrafts are present, the altitude of the aircraft \vill be out of phase \vith the lee \.;raves. The dm.ffi\vind flight \.;ras made at the minimum enroute altitude (4.7 km) over \.Jolf Creek Pass. The dmm\vind flight path \Vas usually a zig-zag pattern in order to increase the in-cloud sampling time and to determine \Vhether there was confluence and/or difluence in the \Vind pattern. If there were no 10\V or middle level clouds present, the upw~nd sounding to the surface was made over Pagosa and flight segments at various altitudes \vere floHn bet\'leen Pagosa and the San Juans. If middle level clouds \.;rere present, an instrument descent \Vas made over Navajo Reservoir. If at 3.0 km the pilot \Vas able to see the ground, then he descended to the surface. All descents were made in an elongated race track pattern in order that the hori- zontal wind data would be reliable during constant heading segments. If the cloud bases \,;ere 2.4 to 2.7 km, a flight up one river canyon to Pagosa \"38 made and the return flight b:1ck to Navajo Reservoir \.Jas made dO\vn a different