Estimates of the Seasonal and Inter-annual Radiosonde Temperature Biases in the Lower Stratosphere using COSMIC, CHAMP, and GRACE from 2006 to 2013

Radiosonde is the only operational instrument that provides in situ atmospheric measurements of pressure, temperature, and humidity from near the surface to an altitude of about 25 to 30 km for the past a few decades. However, because the quality of radiosonde temperature measurements varies with temperature sensor types and height, it is very difficult to use radiosonde temperature data for climate monitoring. Recently, He et al., [2009] and Sun et al. [2011, 2013] used the stable Global Positioning System (GPS) radio occultation (RO) data to quantify the radiosonde sensor type dependent temperature biases. These Sonde-RO comparisons are constructed from a relatively limited period of time. The variations of the biases in a longer time period (~a decade) for different temperature sensor types are still unavailable. In this study, consistently processed GPS RO data from multiple RO missions (i.e., Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), Gravity Recovery And Climate Experiment (GRACE), and CHAllenging Minisatellite Payload (CHAMP)) are co-located with radiosonde data to assess the radiosonde temperature biases in the lower stratosphere for different radiosodne types. The global comparisons of sonde-RO pairs for different temperature sensor types are documented. The global solar zenith angle (SZA) dependent temperature biases for various sensor types are also compared. To further quantify whether the quality of these radiosonde temperature sensors are consistent at different seasons, the inter-seasonal variation of sonde-RO temperature biases are also examined. Time dependent temperature biases for different radiosonde sensor types are presented.