Abstract

The Urban Heat Island (UHI) effect occurs when the temperature in an urban area is higher than the temperature in a rural area. UHIs are generally monitored using remote sensing techniques such as satellite imagery or using temperature sensors deployed in a metropolitan area. In this chapter, a newly proposed methodology to monitor the UHI intensity from Global Navigation Satellite Systems (GNSS) data is described. As the GNSS signal travels from the satellite to the receiver it propagates through the troposphere the travelling signal is delayed by the troposphere. The tropospheric delay is proportional to environmental variables. The tropospheric delay in zenith direction (ZTD) is estimated as part of the Precise Point Positioning (PPP) technique. Therefore, this chapter shows how to process GNSS data to obtain ZTD and how to obtain temperature at an urban and a rural site simultaneously from the ZTD. The advantages of using GNSS data is its availability and many GNSS networks have been deployed in different cities so no need to deploy sensor networks. Furthermore, GNSS signal is less affected by bad weather conditions than satellite imagery.

Highlights

  • The Urban Heat Island (UHI) effect occurs when the temperature in an urban area is higher than the temperature at a rural area

  • 1.2 Relative humidity (RH) in the troposphere: Humidity is defined as the amount of water vapour in the air

  • Global Navigation Satellite Systems (GNSS) signals are susceptible to experiencing delays during their transmission from the satellite to the receiver

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Summary

The troposphere

The atmosphere is divided into several layers, including the ionosphere and the troposphere. The ionosphere is the ionized part of earth’s upper atmosphere and is found from 60–1000 km above earth’s surface. The troposphere is the layer closest to the earth’s surface and is where all weather phenomena are located. The troposphere contains approximately 75% of Earth’s total atmospheric mass and 99% of its total water vapour [1]. Apart from water vapour, the troposphere comprises nitrogen (78%), and oxygen (20%) with the remaining 2% made up of other gases [1,2]. The composition of gases within the troposphere is essentially homogenous, except for water vapour which shows high temporal and spatial variability. The environmental variables present in the troposphere are: pressure, water vapor and temperature

Pressure in the troposphere
Relative humidity (RH) in the troposphere
Temperature in the troposphere
Profile of P, T and RH vs Height
Effect of the Troposphere to GNSS signals
Profile of the Refractivity vs Altitude
Tropospheric delay
Estimation of ZTD
Urban heat island monitoring using GNSS data
Classification of the type of environment around the station
Algorithm to calculate temperature from GNSS data
Calculation of Universal parameters
Calculation of local parameters
Findings
Calculation of temperature

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