UNCLASSIFIED
UNCLASSIFIED
Data Inconsistencies
Sea Level Pressure
•Variation due to uneven terrain features
•Variable pressures due to Convection
•Instrument errors in underdeveloped countries where calibration is infrequent •Inaccuracies in sea level conversions for stations above 1700 feet MSL
Over land areas we see a lot of variation.  The biggest cause of this is the varying terrain.  We have to be aware of the stations we are using.  Two stations can be five miles separated and have 5000 foot differences in elevation.  And both be within five miles of the ocean.

Varying pressure are observed again due to the conversions to sea level.  Some stations are not converting there pressure reliably (or correctly). And some convert in inches, some millibars.

In underdeveloped countries, instrument calibration is inconsistent at best.  In some cases, calibration is either not done or not possible.

In stations above 1700 feet MSL, sea level conversions are less accurate and this must be taken into account.