I love questions!!! One of the main reasons for doing this post is to answer questions and perhaps help someone along the way. Worst case I have some pretty pictures to look at.
To your questions:
The data was a screenshot from some campbell scientific software that is collecting the data. It is part of the system that I am using to calibrate my Pyro. I will be using excel to produce some better graphs so I can get the true correction factor.
Ah references... I think I have used the entire internet for this project!!! For me I started by seeing what the RPi could and couldn't do. Here is what the RPI has that is useful for building a weather station:
8 unused GPIO ports: These are digital ports so you can use them for all things digital. For building a weather station these are handy to drive LED lights and count pulses. For me I will use six of them, one for counting precip bucket tips, one for counting pulses from the wind speed sensor, one as an IRQ for the lightning sensor, one for monitoring the FARS fan's RPM, and two for LED lights (status light and lightning activity light)
2 SPI ports: SPI is just a communcation protocal. Some meterological sensors can use SPI but I would avoid it. The RPi only has two ports and doesn't support slave devices. For me I use one port for my MCP3208 (analog to digital converter, 8 ports) and the other is free.
Analog ports: The RPi has no analog ports! So you need to add some. You can get a board that has this kind of stuff or you can just get yourself a MCP3208 IC and add it to a break out board (BOB). The MCP3208 adds 8 ports. I use one for wind direction, one for the pyro (
I also amp the signel with a INA122), and two to monitor the 12v(for the FARS fan only) and 5v(RPi) rails. Also I went with the MCP3208 because it is a 12bit ADC. This means it will convert voltages into values from 0 (0volts) to 4095 (3.3volts) giving it a resolution of 0.8mv. If I picked a 10bit ADC the resolution would have been 6mv. The pyro needs the resolution of the 12bit ADC hence why i picked it. The wind direction would have been fine with 10bit.
I2C: Second to analog ports (which the RPi has none hence the MCP3208) this is the most useful ports. I2C allows numerous sensors to be attached to a single set of wires (SDA, SCL) where each device has a unique address. I have the lightning sensor, temperature, humdity and pressure all using this port.
Power: The RPi has 5v and 3v3 (also known as 3.3volts). You can only drive like 50ma off the 3v3 rail but the 5v has well over 150ma. Most of my sensors use 5v (lightning, temperature/humidity, wind sensors). The only sensors using 3v3 is the pressure sensor because the BOB (break out board) was designed that way.
Network: If you get the version B you get additional Memory (RAM), an additional usb port, and a ethernet jack. For me, I use the network jack for debuging and wifi (dongle on the usb port) for production. You could use version A but will have to deal with only have one usb port and no ethernet jack.
Storage: only storage is via an SD memory chip. You will need an 8Gb chip to get the OS loaded. A very good idea to image the memory chips incase you have problems. then you could just buy another chip restore the image and you are back in business.
Programming languange: Since the OS is linux you can program in any language that works well in linux (all but VB perhaps??). RPi developers usally use python2, python3 or c++. I stuck with Python2/3 and it seems to be working well. The main issue with Python is it is slower than C++ (for various reasons). For me I am running a python script that samples all my sensors once a second and still have about 8/10 of a second left for the cpu to just sit idle.
WEEWX: This is the software that actually displays the weather data to a web page and also sends it off to Wunderground, NWS, etc... The only rub is that for a custom station you need to build a custom driver to interface it to your data. There are plenty of examples on how to do this. I picked this software as it runs on the RPi with no issues.
References:
http://www.raspberrypi.org/ For all your general questions about RPi.
https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code Here are some good code examples for a few sensors. I "stole" a lot of good ideas from there.
http://www.weewx.com/ all things related to WEEWX.
https://www.sparkfun.com/ Various BOB of sensors can be found here. Also plenty of other BOB for other common IC. I picked up the BMP180 BOB from them.