A Process Toward Recovering Greater Assimilation of ADS-C ABO Data

Automatic Dependent Surveillance - Contract (ADS-C) data provide aircraft-based observations (ABOs) from participating commercial aircraft completing long hauls over remote parts of the world where traditional AMDAR data cannot be readily transmitted or when the AMDAR transmission capability is otherwise not available. ADS-C data relayed from U.S.-registered air carriers, and provided by Collins Aerospace (formerly Rockwell Collins), were introduced as a source of meteorological ABOs to be assimilated into NCEP numerical weather prediction (NWP) systems beginning in FY2015. Additional ADS-C data originating from international air carriers are planned to be introduced into NCEP operations during FY2020.

Standard quality reviews of ADS-C data initially revealed systematic, low-grade anomalies of wind vector RMSE among a subset of aircraft. Additional investigation of the data concluded that the sign of the v-component of the wind vector was erroneously represented by the ADS-C system aboard Boeing 787 model aircraft under certain circumstances. A comparison of independent AMDAR reports available from affected aircraft further revealed that the ADS-C data anomalies occur as an aircraft traverses a predominantly meridional wind regime, specifically featuring a v-component magnitude equaling or exceeding the value of 0.75 × u. In light of these findings, all ADS-C wind data transmitted by the affected aircraft are presently blocked from assimilation into NCEP NWP systems.

Given that no analogous anomalies were found to occur with ADS-C temperature data, and in lieu of a correction being applied to avionics systems across many affected aircraft operated by many carriers, there exists a need to develop a solution toward recovering greater utility of this unique ABO source.

In further collaboration with Collins Aerospace, a processing technique is being developed at EMC that utilizes available aircraft motion vector data - relative to the air and to the ground - to generate alternative ADS-C wind vector data for some of the affected aircraft. Application of the processing technique will effectively generate corrected wind vector data that more accurately represent atmospheric conditions observed by the hundreds of B787 aircraft transmitting ADS-C information worldwide. The processing technique for correction may be additionally applicable to other, more random instances of wind vector error.