Retrieval and analysis of precipitable water vapour based on GNSS, AIRS, and reanalysis models over Nigeria

摘要

Precipitable water vapour (PWV) retrieved from ground-based Global Navigation Satellite System (GNSS) stations over Nigeria from 2013 to 2014 is compared with PWV from a satellite remote-sensing technique (Atmospheric Infrared Sounder [AIRS]) and a global reanalysis model (ERA-Interim) over Nigeria. The PWV for AIRS and ERA-Interim was obtained from the respective data providers. PWV estimates from the different techniques were grouped into daily estimates and were matched and re-grouped into monthly and seasonal averages. The performance of the PWV techniques was evaluated using recommended indices by the World Meteorological Organization. All datasets gave a reasonable estimate of PWV when compared against GNSS at daily, monthly, and seasonal scales, the agreement between the various techniques was better at monthly and seasonal scales. In terms of bias, precision, accuracy, fitness, and reliability of measurement, ERA-Interim outperformed the other technique and could possibly be a complementary data source to GNSS PWV, although as a reanalysis, it cannot be used for meteorology. The AIRS night-time (or descending) retrieval was ranked next to the ERA-Interim; AIRS daytime (or ascending) retrieval agreed less with GNSS PWV when comparedwith ERA Interim and night-time AIRS. These results indicate that GNSS PWV as observed over the study area represents a remarkable dataset for further evaluation studies and serves as a useful source of humidity information to improve the water cycle in numerical weather models for varying applications in the region.