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Chapter I: Introduction

Table of Contents


Water vapour is one of the most influential constituents of the atmosphere. It's the Earth's primary greenhouse gas, more effective than carbon dioxide. Water vapour is responsible for more than 50% of the energy transport from low to high latitudes. Vertical water vapour transport establishes a thermal equilibrium between the warmer Earth surface and the higher atmosphere by latent heat fluxes and vaporisation.

More than 99% of the atmospheric water is in the form of water vapour, most of it concentrated in the lower layers of the troposphere. The amount of water vapour in the atmosphere is responsible for determining the amount of precipitation a region can receive.

In this module, we will introduce the concept of "Total Precipitable Water" (TPW) and show how satellite-based products help in estimating the amount of water vapour in the atmosphere. The module starts with an overview on measuring principles and algorithms on how to retrieve the water vapour content of the atmosphere. In the second chapter, you will learn more about the different TPW products from geostationary and polar orbiting satellites. Finally you will see some practical applications of TPW products in nowcasting precipitation events.

Figure 1: Condensed water vapour over the Champagne Pool of the Waiotapu geothermal area in New Zealand's North Island. The hot spring was formed 900 years ago by a hydrothermal eruption.


This product tutorial has benefited from many advices and suggestions provided by Sheldon Kusselson (NOAA/NESDIS) who gave valuable input on recent developments of TWP products in the United States.


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