![]() Typically transmitted by the Aircraft Meteorological Data Relay (AMDAR WMO 2003), the aircraft observations provide the data assimilation (DA) systems with in situ measurements of the important dynamical variables of temperature and wind ( Daley 1991). Forecast kinetic energy spectra indicated that the reduction in error is related to analysis updates on all scales resolved by COSMO-DE.įor more than two decades, operational numerical weather prediction (NWP) has benefited from aircraft observations. With the current data assimilation setup, a saturation of the forecast error reduction was apparent when more than 50% of the Mode-S EHS data were assimilated. ![]() The amount of Mode-S EHS data was reduced by random thinning to test the effect of a varying observation density. With the high density of Mode-S EHS observations, a reduction of temperature and wind error in forecasts of 1 and 3 hours was found mainly in the flight level and less near the surface. For temperature, a larger error was diagnosed for Mode-S EHS. In the comparison of both aircraft observation systems, a similar observation error standard deviation was diagnosed for wind. The number of observing aircrafts in Mode-S EHS was about 15 times larger than in the AMDAR system. The upper-air spectra are shown for the experiments (a) Aconv, (b) MAconvTh10, (c) MAconvTh50, and (d) MAconv.Īircraft observations of wind and temperature collected by airport surveillance radars were assimilated in the Consortium for Small-Scale Modeling Kilometre-scale Ensemble Data Assimilation (COSMO-KENDA), which couples an ensemble Kalman filter to a 40-member ensemble of the convection permitting COSMO-DE model. Kinetic energy of the difference wind fields from NoDA (along latitudes between 10 and 12 km MSL), scaled by absolute kinetic energy of the NoDA wind field. The plotted circles are centered on every eighth point of the coarse analysis grid, so the overlap of the local LETKF solutions is denser than in this illustration. (c) Snapshot of the localization length scale at the surface level at 1200 UTC. (a) Adaptive covariance inflation factor, averaged over the experimental period on the pressure levels of the analysis grid. At levels where the RMS of an experiment is smaller than the RMS of NoDA, the difference is always significant and the diamonds are not plotted.Įstimated observation error STD for AMDAR and Mode-S EHS observation spaces is the initial error standard deviation value used as input for the LETKF for both AMDAR and Mode-S EHS for all experiments. A two-colored diamond on a level means that the RMSs of the left experiment are significantly smaller than that of the right experiment. 5, but for experiments NoDA, MAconvTh10, MAconvTh50, and MAconv.įorecast RMS of the Mode-S EHS thinning experiments and Aconv, evaluated for the last hour of the 3-h forecast windows from 0900 to 1200 UTC and 2100 to 0000 UTC. A two-colored diamond on a level means that the RMSs of the left experiment are significantly smaller than that of the right experiment.Īs in Fig. 3, but for experiments NoDA, MAconvTh10, MAconvTh50, and MAconv. 9, and is scaled by the respective RMS to fit into the x axes of the plots.Īs in Fig. Where data are actively assimilated, the consistency ratio CR is computed using the estimated values of Fig. STD of the ensemble and RMS of the ensemble mean for upper-air observations of (left) wind speed, (middle) wind direction, and (right) temperature throughout the 1-hourly cycling, for experiments NoDA, Aconv, Mconv, and MAconv. Mean ( ) of the ensemble members for upper-air observations of (left) wind speed, (middle) wind direction, and (right) temperature throughout the 1-hourly cycling, for experiments NoDA, Aconv, Mconv, and MAconv. ![]() Mean RMS ( ) of the ensemble members for upper-air observations of (left) wind speed, (middle) wind direction, and (right) temperature throughout the 1-hourly cycling, for experiments NoDA, Aconv, Mconv, and MAconv. Differences in the low-level distributions are due to highly frequented airports and are overly exaggerated by their color scales. (c),(d) The vertical density against longitude. The color scale in (b) is enhanced by a factor of 10 with respect to (a). (a),(b) The horizontal density of assimilated aircraft observations of AMDAR and the full Mode-S EHS set per average day. The average number of observations per day are 11 851 PROF, 5813 SYNOP, and 1571 TEMP. The areas of the circles correspond to the average daily number of single observations of the wind variable per station. The circles indicate positions of the surface-based stations. Domain extent of COSMO-DE with conventional observations.
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