Abstract
Precipitable water vapor (PWV) content detection is vital to heavy rain prediction; up to now, lots of different measuring methods and devices are developed to observe PWV. In general, these methods can be divided into two categories, ground-based or space-based. In this study, we analyze the advantages and disadvantages of these technologies, compare retrieved atmosphere parameters by different RO (radio occultation) observations, like FORMOSAT-3/COSMIC (Formosa Satellite-3 and Constellation Observing System for Meteorology, Ionosphere, and Climate) and FY3C (China Feng Yun 3C), and assess retrieved PWV precision with a radiosonde. Besides, we interpolate PWV from NWP (numerical weather prediction) reanalysis data for more comparison and analysis with RO. Specifically, ground-based GNSS is of high precision and continuous availability to monitor PWV distribution; in our paper, we show cases to validate and compare GNSS retrieving PWV with a radiosonde. Except GNSS PWV, we give two different radio occultation sounding results, COSMIC and FY3C, to validate the precision to monitor PWV from space in a global area. FY3C results containing Beidou (China Beidou Global Satellite Navigation System) radio occultation events need to be emphasized. So, in our study, we get the retrieved atmospheric profiles from GPS and Beidou radio occultation observations and derive atmosphere PWV by a variational retrieval method based on these data over a global area. Besides, other space-based methods, such as microwave satellite, are also useful in detecting PWV distribution situations in a global area from space; in this study, we present a case of retrieved PWV using microwave satellite observation. NWP reanalysis data ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim and the new-generation reanalysis data ERA5 provide global grid atmosphere parameters, like surface temperature, different-level pressures, and precipitable water. We show cases of retrieved PWV and validate the precision with radiosonde results and compare new reanalysis dataset ERA5 with ERA-Interim, finding that ERA5 can get higher precision-retrieved atmosphere parameters and PWV. In the end, from our comparison, we find that the retrieved PWV from RO (FY3C and COSMIC) and ECMWF reanalysis data (ERA-Interim and ERA5) have a high positive correlation and that almost all R2 values exceed 0.9, compare retrieved PWV with a radiosonde, and find that whether it is RO and ECMWF reanalysis data, ground-based GNSS, or microwave satellite, they all show small biases.
Highlights
Precipitable water vapor content change plays an important role in atmospheric water transport, energy conversion, and climate change, so it is meaningful to monitor and understand its change situation and mechanism [1, 2]
We present some comparison and analysis work between these observations and reference results obtained from the radiosonde; besides, we derive Precipitable water vapor (PWV) from the International Geodetic Service (IGS) GNSS station’s observations and present PWV of ATVOS measurements; what is more, we retrieve PWV from ERAInterim and ERA5 reanalysis datasets and perform a global comparison of PWV from the collocated COSMIC and FY3C radio occultation profiles
We use COSMIC and FY3C radio occultation observations to retrieve PWV, so here we introduce more about COSMIC and FY3C constellations; the COSMIC radio occultation mission had been successfully launched on April 14, 2006
Summary
Precipitable water vapor content change plays an important role in atmospheric water transport, energy conversion, and climate change, so it is meaningful to monitor and understand its change situation and mechanism [1, 2]. We present some comparison and analysis work between these observations and reference results obtained from the radiosonde; besides, we derive PWV from the IGS GNSS station’s observations and present PWV of ATVOS measurements; what is more, we retrieve PWV from ERAInterim and ERA5 reanalysis datasets and perform a global comparison of PWV from the collocated COSMIC and FY3C radio occultation profiles. We compare these results with the radiosonde to check their applicability and precision.
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