Meteorological conditions at a coastal fog collection site in Peru

Abstract

Meteorological measurements were made from July through November 1990, at a field site 35 km north of the center of Lima, Peru, during a study designed to assess the quantity of fog water that could be collected The site was at an altitude of 430 m, on the summit of a low, flat topped, mountain 3.5 km from the coast The mean monthly wind speed at the site varied from 4.1 m s^-1 in July to 5.4 m s^-1 in October. The highest hourly and peak instantaneous wind speeds were 15.2 m s^-1 and 16.6 m s^-1, respectively and they occurred in October. The monthly average wind directions was almost constant at 197ºT. The mean monthly temperature increased from 13.1ºC in july to 15.5ºC in November and, when compared to the climatological values from the Lima airport (altitude 11 m), implied a lapse rate of 0.5ºC/100 m in the lower 400 m of the atmosphere. The mean relative humidity was near saturation from July through October and only dropped slightly in November with the coming of drier conditions in late spring. Measured precipitation was a minimal 10.5 mm yet this represented an increase over the climatological value of 5.9 mm for the same months at the Lima airport. These data provide the first comprehensive description of the meteorological conditions on a loma (hill with seasonal vegetation) on the coast of Peru. They further our understanding of how atmospheric water is made available to the plants and will be of great assistance in the designing and locating of large fog collectors, which can produce water for the afforestation and reforestation of the desert hills.