The Complex World of Humidity and Temperature

During sunlight hours (minimal cloud) the water vapour in the air will absorb long wave IR (Green House Effect) from the sun and from the ground.
This will be radiated back in all directions.
The solar radiation will therefore be modified such that the wavelengths absorbed by the water vapour will be reduced depending on the effectiveness of the green house effect.
 However the same wavelengths radiated upwards will be more effectively "reflected" back down.

At night the solar input stops and the only radiation hitting the earth is that from GHGs So more water vapour = better "reflector"

Is this visible in the data previously used below.
Firstly data is limited and to get sensible results each point needs significantly more than one result to be significant.

Night time readings cannot include cloud coverage as this is not measured when dark
The former plots used either average or min/max values. The min max tend to plot one off anomalies. In the plots below 1st and 3rd quartile results have been used to improve this.

First a whole year all possible times with up to 9% opaque cloud cover

http://www.nrel.gov/midc/srrl_bms/

not sure why humidity so high!

Now in sequence 2 months at a time a couple of hours and up to 9% opaque cloud cover

Now for some night responses 2 months at a time

Conclusion?

• Well minimum temperature shows a increase with increasing water vapour (positive slope) over coldest period but turns to negative slope during warmer months
• The max temp during the night shows little change with water vapour.

More on IR water penetration depth

Using a similar setup to the previous  posting different filtering methods have been used to see if pentration depth can be tested.

In test 1 a heat sink was placed in the tube preventing any visible light entering the water. The stable temperature of the heatsink was 100C The tube was ventilated from just above the transparent seal above the water to just below the heatsink. at the top of the tube. The bulk of radiation entering the water would be radiated from the bottom of the heatsink

In test 2 the heat sik was replaced with a 1cm deep tray of water. This should effectively remove any LW IR leaving only visible light. The tube was again ventilated.

The temperature plots with depth are shown together with the rate of change of temperature with depth.

Not very conclusive although it appears that 100C blackbody is significantly attenuated below 6mm of depth. (the final 2 thermocouples showing the leakage of the thermos heating the water (possibly)

The visible light seems to be adding significantly to the water at a depth of 55mm.

Note that there seems to be no explanation for the dips in reading of temperature. The apparatus was not disturbed and no light change occurred. (one of the dips - at 24mins was caused by the filter water being replaced with cool water)



 

 

2012-08-12

http://lasp.colorado.edu/sorce/images/instruments/sim/fig01.gif

 

How far does IR penetrate Water? (failed?)

An attempted experiment to measure how far IR penetrates (tap) water (UK variety)

Problem points:

• The wide necked Vacuum flask turns out to be a wide necked flask!
• The high frequency cut off of the IR pass filter is not known (this was purchased from Edmund Optical)
• The High intensity Low votage Halogen lamp is not the sun and has a peak output at the red end of solar spectrum (3500K cf 5000K)

Test setup

Thermocouples are placed away from the light input at distances below the water surface of

• 1mm
• 3mm
• 11.2mm
• 18.5mm
• 39.5mm

Tube and filter 50mm diameter

2 runs made with and without the IR pass (visible stop) filter:
These produce 2 outputs:

The Filter
Using a camera as a lightmeter and looking at the halogen source the filter reduces the exposure (mainly visible) by a factor of 110.
The light source.
20 watts = perhaps 10 watts into tube and 1 watt (unfiltered) into water


What they show
The spectrum of the bulb is not generated from a hot enough filament. The heating effect of filtered and unfiltered light is very similar.
Unfiltered heating does not predominate at greater depths (it is virtually the same as IR "only")
At a 39mm depth heating effect has little effect over the leakage throught the faulty vacuum flask.

What I would have thought.
Despite the limitations I would have expected significantly greater heat imput (faster temp rise ) at depth with unfiltered light.

Suggestions?