A comparison of humidity measurements from ACARS-equipped aircraft and rawinsondes

Observations of temperature and winds from commercial aircraft have increased significantly in the last few years over the United States, and to a lesser extent, worldwide. The dataset has been critical in allowing the development and operation of high-frequency data assimilation systems covering the United States. Aircraft observations relayed through the system known as the Aircraft Communications, Addressing, and Reporting System (ACARS) are used to improve the initialization of operational numerical weather prediction models, which in turn, improve the accuracy of the numerical forecasts.

The rawinsonde has been the mainstay of moisture measurements since its introduction in the 1930s. Although new observing platforms introduced in the 1990s (such as satellites and ground based GPS systems) provide integrated moisture measurements, none of them provide a detailed vertical moisture profile essential for numerical weather prediction models. The development of a humidity sensor for use on commercial aircraft is an important and exciting prospect for the meteorological community. It has the potential to provide frequent detailed observations of moisture from aircraft that already report temperature and wind measurements on ascent and descent into and out of busy airports.

This paper provides a comparison of an experimental set of humidity observations taken from aircraft outfitted with the new moisture sensor and rawinsonde observations. The results of this comparison should provide benchmark information as to the accuracy of this new instrument.