Mark,
concerning your query about getting geothermal information out of
Landsat TM or AVHRR, I've been looking at geothermal sources in thermal infrared images and modelling the heat flow as, basically, my PhD project for the last
three years, so I imagine that i can be of assistance to you :-)
In general:
Atmospheric Thermal Noise dominates the signal. The TIR is highly controlled
by solar radiance, sensible heat transfer and all manner of tedious meteorology.A geothermal source needs to be pretty ho battle through all that noise. My
most useful case study has been looking at TIM images of a lava tube, where a
1400K lava tube 2-3 metres down managed to elevate surface temperatures by 10-15 degrees. Basically, it must be bloody hot, big and shallow to show up. There
are some reports of other shallow intrusions being spotted on Landsat TM, but
they are equivicol.
The other problem is resolution, a source must be big enough to make
a difference on a big Landsat TM or enormous AVHRR pixel. People can monitor
surface lavas alright with the big pixels, because they are so hot.
In arid regions it is easier, as there is less surface clutter, but,
to the best of my knowledge, no-one has done much with it, except for larger,
more obvious sources, i.e. hot spring complexes, which are, in any event, more
visible in other bands. One could probably use the TIR to quantify the heat
budget of these things though.
There is one paper by a russian Dude Tronin, in International Journal
of Remote Sensing, in which he describes stacking 10,000 (!) AVHRR images of
central asia and says he detected regional warming precorsury to earthquake
activity. Sounds good, but (shrug) I've never seen it cited anywhere, and
only found it by accident, so perhaps not.
Anyhow, if you wish to email me off list I can certainly help you
with any other queries. I am presently finishing up and hunting for case studies,
so would be delighted to help. If you send me a surface mail address I can send
you a copy of my bibliography and a paper or two.
I look forward to hearing from you,
Rob Cosgrave
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