An Overview of Integrated Water Vapour Estimation for Flood Monitoring in Nigeria: The Role of NIGNET GPS CORS

Abstract

Water vapour is a very dynamic component of the atmosphere. It greatly influences the atmospheric stabilization mechanism. Hence, it is very difficult to measure or model using classical meteorological systems or models. Tropical atmosphere holds the largest amount of water vapour, thus its characterise high climate uncertainty. Interestingly Geodesists have devised methods for estimating the extent to which signals propagating from GNSS to ground‐based GNSS receivers are delayed by atmospheric water vapour. This delay is parameterized in terms of a time‐varying zenith wet delay (ZWD) which is retrieved by stochastic filtering of the GNSS data. Given surface temperature and pressure readings at the GNSS receiver, the retrieved ZWD can be transformed with very little additional uncertainty into an estimate of the integrated water vapour (IWV) overlying that receiver. Nowadays, networks of GNSS continuously operating stations (CORS) are available for a wide range of positioning capabilities and can offer the possibility of observing the horizontal distribution of IWV or, equivalently, perceptible water vapour (PWV). Thus, surface-based GNSS measurements of zenith path delay (ZPD) can be used to derive vertically integrated water vapour (IWV) of the atmosphere. Applicability of GPS for meteorology have been established in literature but much have not been done to check the impact of integrated water vapour for monitoring fload in Nigeria using Nigeria (Nignet) CORS. This paper is an overview of integrated water vapour estimation from the Nigeria Nignet GPS CORS.