HR: 11:35h
AN: B32A-06    [Abstracts]
TI: Declining Pan Evaporation: A Closer Look at the Ecohydrological Implications and the Physics
AU: * Roderick, M L
EM: Michael.Roderick@anu.edu.au
AF: The Australian National University, CRC for Greenhouse Accounting Research School of Biological Sciences The Australian National University, Canberra, ACT 0200 Austria
AU: Farquhar, G D
EM: Graham.Farquhar@anu.edu.au
AF: The Australian National University, CRC for Greenhouse Accounting Research School of Biological Sciences The Australian National University, Canberra, ACT 0200 Austria
AB: The evaporation of water from meteorological pans has been steadily decreasing in many parts of the world over the last 50 years or so. These observations show that the "evaporative demand" of the atmosphere over land has been steadily decreasing. The trends seem counter-intuitive given the observed warming of air near the surface. However, physical principles show that "evaporative demand" is not very sensitive to changes in average air temperature near the surface. Hence, the trend does not violate any known physical principles. More importantly, the trend has profound importance for our understanding of the ecological and hydrological impacts of climate change and the greenhouse effect. To physically understand the decline requires detailed calculations of pan evaporation as a function of irradiance, vapour pressure deficit and windspeed. These calculations separate the changes into separate radiative and aerodynamic components. In this paper we first describe the ecological and hydrological implications of changing evaporative demand. After that we present some recent calculations of the radiative and aerodynamic components of pan evaporation and compare these with observations.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 1610 Atmosphere (0315, 0325)
DE: 1813 Eco-hydrology
SC: Biogeosciences [B]
MN: Fall Meeting 2005