Atmospheric analysis

Quality factors: Relative cosine error, Q and DCE
Relative cosine error
The quality of the diffuser is defined with the following quality factors.
The "relative cosine error" is defined by:
Q correction factor
Q is a correction factor for isotropic radiation:
This factor 'Q' is greater than 1 if the diffuser overestimates and less than 1 if the diffuser underestimates.
Diffuse Cosine Error (DCE)
The "Diffuse Cosine Error" shows the actual quality of the cosine response response.
Physical meaning of the DCE: If the diffuser has a perfect cosine response this factor will be zero.

For this experiment the diffuser is placed at a position which is 20 mm greater than the normal fibre position. In between diffuser and fibre is a teflon "light tunnel". The cosine response is shown below:
The graph shows that the cosine response does not change dramatically, altough it improves a little.
This suggest that the diffusers do not necessarily have to be used in combination with a fibre.

Drawing with dimensions of diffuser BAT 5
The diffuser’s distance to fibre distance is matched to the fibre’s N.A. There is a slight slope in the diffuser’s surface to drain the water through a drainage hole. An 'o'-ring gives additional protection against rain.
The diffuser can be made in almost any size.

DCE,Q?

Previous meaurements show indications that the transmission of teflon might change after cleaning the diffuser with alcohol. The next graph shows the signal before and after cleaning the diffuser with alcohol.
This graph shows that there are no significant changes in signal after cleaning with alcohol.

The position of the diffuser's entrance aperture needs to be known for accurate calibration. Because the diffuser has a hemispherical shape the effective entrance aperture is not exactly located at the front surface.
Experiments with the lamp at 1.5 m and 0.5 m show that according to the inverse square law the location of the effective entrance aperture is 1.4 mm (±1mm) behind the front surface of the diffuser.
Info, questions and remarks, contact:
Richard McKenzie [ [email protected] ]

While in use it is best to clean the diffuser on a daily base with a piece of dry cotton. This to wipe of any dirt, dust, snow etc. If the diffuser for some reason gets really dirty it is recommendable to clean it with water and soap or alcohol. Dust inside the diffuser can be removed with a cotton bud.
Info, questions and remarks, contact:
Richard McKenzie [ [email protected] ]

There is a wide range of instruments at Lauder, which are listed on this page.

DCE,Q?

NIWA uses Trimble RTK GPS surveying equipment to undertake precise topographic and bathymetric surveys. These surveys are used to measure beach stability, river bed erosion and deposition, and to make digital terrain models of rivers for 2-dimensional hydrodynamic modelling. 

Mass of Seawater = w(sw) [kg]
Volume of Manometer = Vman [cm3]
Manometer Temperature = T [°C]
Manometer Pressure = Pfinal [Pa]
Pressure transducer zero = Po [Pa]
Universal Gas Constant = R = 8.314 J K-1 mol-1
Virial Co-efficient B(CO2) [cm3 mol-1] B = 1636.75+(12.0408*(T+273.16))-(0.0327957*(T+273.16)2)+(0.0000316528*(T+273.16)3)
Vm(CO2 at manometer T and P) [m3] – calculate iteratively, initial Vm = 0.22264 =R*(T+273.16)/((Pfinal - Po))*(1+(B*0.000001/Vm))
CT

Alice is an instrument package for measuring bottom-boundary-layer processes in estuaries and the ocean. It consists of a self-ballasted tripod upon which is mounted a "core" sensor package for measuring boundary-layer currents, turbulence and waves. Alice is principally rigged for sediment-transport studies (with optical and acoustic backscatter sensors, sediment traps and a pump sampler) but has also been used extensively in studies of boundary-layer mechanics, animal–flow–sediment interactions, wave dynamics and nutrient/gas fluxes.