Figure 4

Time series of quantities, which are derived from an assimilation, and which are described in “Observation space diagnostics”. The red circles and plusses mark the number of observations available and assimilated at each time (right axis). The black line is the root mean square error of the prior model estimates of the zonal wind (\(\text{ms}^{-1}\)) relative to the wind observed by AIRCRAFT (left axis). The green line is the total spread, described in the same section. These quantities were derived from a subdomain of the model; north of \(20^\circ \) N and from approximately 225–275 hPa high. The statistics in the header pool all of the observations in this time span, including the spinup period, so they are not representative of the statistics in the rest of the reanalysis.