3-D Atmospheric Moisture Retrieval using GNSS

Water vapour, one of the dominant greenhouse gases, is a highly variable constituent of the Earth's atmosphere with a high latent heat. These two factors give it a key role in the development of atmospheric dynamics. Knowledge of the behaviour and distribution of water vapour in the atmosphere is crucial for understanding and predicting weather and climate. Unfortunately, atmospheric water vapour cannot be accurately determined from surface relative humidity measurements and information at higher altitudes is obtained via atmospheric sounding (i.e. radiosondes) and microwave profilers. The cost of these instruments limits their use to sparsely deployed networks and, in the case of soundings, routine launches are usually performed only twice per day. Over the past decade, however, Global Navigation Satellite Systems (GNSS) have become optimistically regarded as powerful and novel tools to measure water vapour at a fraction of the cost of traditional methods.