Assimilation of High Resolution Mode-S Wind and Temperature Observations in a Limited Area NWP-model

In this report we present the positive impact of high resolution (in space and time) of wind
and temperature observation from aircraft on short-range numerical weather forecasting. The
observations are retrieved using the Tracking and Ranging radar from Air-traffic Control at
Schiphol Airport, the Netherlands. This enhanced surveillance radar tracks all aircraft in sight
every four seconds generating one million wind and temperature observations per day around
the Netherlands.
When assimilated into a numerical model with a hourly update cycle, the three dimensional
wind field is better for now-casting purposes than the operational forecast which is available
every three hours. The positive impact on wind in the first hours of the forecast gradually turns
into a neutral impact, when compared to other wind and temperature observations. The gain
for now-casting comes from the short latency of the forecasts combined with the high resolution
of the observations.
All in all, assimilation of high resolution wind (and temperature) observations is therefore
benificial for now-casting and short-range forecasts up to two to three hours.