Upper Air Indices - Differences

AB5R · Post by **AB5R** » Fri May 16, 2008 3:10 pm

Can anyone explain why Upper Air Plots from Unisys, SPC and Digital Atmosphere will have different numbers for various indices? Would RAOB be any more credible?

Thanks

Greg Higgins · Post by **Greg Higgins** » Sat May 17, 2008 2:26 pm

Part of it depends on what parcel is being lifted (i.e., MU-most unstable, surface based, etc.), what time was the sounding obtained (not all are 00z and 12z) and if they are based on a model (for 2-3 days out). RAOB is an excellent program and allows many functions to be determined by the user.

Greg Higgins

Post by **Tim Vasquez** » Sat May 17, 2008 2:49 pm

If you're talking about upper air plots (i.e. a horizontal map), the final output is very sensitive to the conditions of the original analysis.

First there are two ways of doing this.

The easiest way is to take the LI at each individual station and then just analyze it horizontally across the map domain. Some sources may do that.

Other sources (including Digital Atmosphere) will analyze the temperature and moisture at different levels, in this case the lowest levels of the atmosphere and 500 mb, and then generate LI across those fields using a grid. That too will generate different results from different sources because no particular analysis field is dead-on, and the differences can magnify when you are computing across multiple fields.

Tim

AB5R · Post by **AB5R** » Sat May 17, 2008 3:01 pm

Thanks to each of you for answers. I simply downloaded the same upper air report from each source and ran one with Digital Atmosphere too. Some numbers agreed and others did not. I was just wondering why. I assume that all were Mixed Layer outputs. (I could be wrong here.)

Obviously, I am a newbie trying to learn, The Upper Air skew-T charts are my focus right now. I have bought the RAOB software and waiting for the Manual. Can anyone suggest a tutorial book specifically on this subject??

Thanks again,
Jerry