20th century reanalysis is basically a stats project, not observed data
they take sparse SLP observations (there were like 1.5 ship tracks in the 1900s) and estimate large scale circulation in the troposphere.
from the abstract: http://onlinelibrary.wiley.com/doi/10.1002/qj.776/abstract : .. It uses an Ensemble Kalman Filter data assimilation method with background ‘first guess’ fields supplied by an ensemble of forecasts from a global numerical weather prediction model. This directly yields a global analysis every 6 hours as the most likely state of the atmosphere, and also an uncertainty estimate of that analysis.
no subject
they take sparse SLP observations (there were like 1.5 ship tracks in the 1900s) and estimate large scale circulation in the troposphere.
from the abstract: http://onlinelibrary.wiley.com/doi/10.1002/qj.776/abstract :
.. It uses an Ensemble Kalman Filter data assimilation method with background ‘first guess’ fields supplied by an ensemble of forecasts from a global numerical weather prediction model. This directly yields a global analysis every 6 hours as the most likely state of the atmosphere, and also an uncertainty estimate of that analysis.