TAMDAR observations (Tropospheric Airborne Meteorological Data Reporting) are becoming a major source of input data in data assimilation system with the advantage of high spatiotemporal resolution and humidity measurements. Other than scattered radiosonde (RAOB), there are no other in situ observations that can provide humidity information routinely collected in the continental United States and Alaska. It delivers thousands of daily observations from locations and at times not available from any other observing system. So, it is important to further understand the impact of TAMDAR data on regional forecast error reduction, especially the humidity data impact.

       WRFDA-FSO is used to evaluate the impact of TAMDAR data on the forecast error reduction. WRFDA-FSO is conducted using the WRFPLUS (WRF non-linear model, tangient linear and adjoint mode) and WRFDA data assimilation system. This package is designed to compute the Forecast Sensitivity to Observations (FSO) or in other words the impact of observations on the forecast error reduction. The TAMDAR impact on the 24-h forecast error reduction will be evaluated respectively for both winter (January) and summer (June) on Airdat Operational CONUS domain. Both the impact of total TAMDAR data and each variable (T, Q, U, V) will be presented according to data location and vertical level.