Many societal problems (e.g. weather forecasting, climate changes, water management, dispersion of air pollution and seeds) require an accurate understanding of the vertical fluxes of heat, momentum and mass (water vapour carbon dioxide, dust and aerosols) over land surfaces at horizontal scales of 0.5 to 100 km. At these scales land surfaces are usually heterogeneous. In a past STW project our group showed that a large aperture scintillometer (LAS) yields the sensible heat flux on the required scales over heterogeneous terrain. This research was partly sponsored by STW and resulted in utilisation by Kipp & Zonen, Delft, Netherlands. A scintillometer measures light intensity fluctuations caused by atmospheric turbulent motions. Pilot studies with a millimetre-wave scintillometer (MWS) have been done also. This proposal is a logic extension of this work. It aims to develop two new operational scintillometer types:
- A combined LAS-MWS system, denoted as OMS (Optical-Millimetre wave system), for the fluxes of sensible heat and water vapour. A number of scientific issues has to be solved before a OMS can be used operationally;
- A short-path scintillometer (SPS) system based on LAS technology applicable in agriculture over irrigated fields under advection conditions for obtaining both actual evapotranspiration (ET) and momentum flux.
Prospects for utilisation of the proposed systems are good. Worldwide the scarcity of fresh water for agriculture, domestic and industrial is a well-recognized social-economical problem. Therefore, systems for direct observations of actual ET on field scale as well spatial scales of 10 - 100 km2 are expected to be utilized worldwide. |
