Comparison of monthly piche readings with the penman aerodynamic term in the New Zealand climate network

On the proper employment of Piche evaporimeters in estimating evapotranspiration

“…This has also been concluded for Penman evaporation estimates, from either the findings of Heine (1981), or from the analysis of monthly data in Athens (Papaioannou et al, 1996). Contrary to this, Fitzpatrick and Stern (1966) stated that a single generalized relationship for an entire year should be justified for obtaining Penman evaporation estimates.…”

“…The gradients obtained from the regression lines (h ranging from 0.23 to 0.31) are in accordance with the values referred to in the international literature, mainly when Equation (3) is employed with zero intercept (Table I) and this is in agreement with the very small intercepts (b ranging from 0.02 to 0.12 mm/day) which have been evaluated. When Equation (3) is employed with an intercept and daily values of the parameters are used, larger gradients (0.4, 0.6 and 4) are reported by Thom et al (1981) for France, Fitzpatrick and Stern (1966) for Western Australia and by Heine (1981) for New Zealand, respectively. The larger values of h (in temperate conditions) found by Thom et al (1981), are most probably attributable to the worse ventilation of the small meteorological screen used.…”

“…Part of the very high pooled mean gradient obtained for New Zealand can be accounted for by the height of the anemometer, which was considered 6 m. A smaller regression gradient (0.14) was obtained by Stanhill (1962), for weekly measurements of the parameters in Israel. It must be also mentioned that both studies of Stanhill (1962) and Fitzpatrick and Stern (1966) were conducted under irrigated conditions and they were referred to locations (Gilat at Israel or Kunamura at Western Australia, respectively), neither of which is similar to the climate in Athens (Gilat, has a hot steppe climate and Kunamura has a tropical rainy climate, (Heine, 1981)). …”

“…Independently, both Stanhill (1962) and Bouchet (1963) were the first to point out that its exposure within a meteorological screen responds primarily to wet bulb depression and to wind speed, the essential variables in the second term of Penman's equation (Penman, 1948(Penman, , 1963, and their idea was worked out further by Brochet and Gerbier (1972). Statistical relationships of the Piche measurements to the Penman aerodynamic term have been presented either for monthly values of the parameters (Brochet and Gerbier, 1977;Papaioannou et al, 1996), or for daily values of the parameters (Fitzpatrick and Stern, 1966;Thom et al, 1981;Heine, 1981). The obtained results are apparent in Table I.…”

Evaporative demand across a range of microsites in partial-cut boreal forests

“…Atmometers have been used for over two centuries (Livingston, 1935); US Class A pans and Piché evaporimeters are still used in meteorological stations around the world and a commercially available Bellani plate atmometer, made by ETgage † (ETgage Company, Loveland, CO, USA) has been tested for irrigation scheduling (Magliulo et al, 2003;Irmak et al, 2005). Atmometers are considered most sensitive to the aerodynamic component of PET (Stanhill, 1962;Heine, 1981); sensitivity of atmometers to wind speed is appropriate for placement in understoreys because there is a strong increase in wind speed following partial harvest (Bladon et al, 2006), but wind is difficult to measure without expensive instrumentation. Direct measures of evaporation from simple instruments would allow for spatial replication across a range of conditions and at a smaller scale than is currently feasible with micrometeorological instrumentation (Kettridge & Baird, 2006).…”