The need for measurements

Whether it be for meteorological, hydrological, oceanographic or climatological studies or for any other activity relating to the natural environment, measurements are vital. A knowledge of what has happened in the past and of the present situation, and an understanding of the processes involved, can only be arrived at if measurements are made. Such knowledge is also a prerequisite of any attempt to predict what might happen in the future and subsequently to check whether the predictions are correct. Without data, none of these activities is possible. Measurements are the cornerstone of them all. This book is an investigation into how the natural world is measured.

The things that need to be measured are best described as variables. Sometimes the word ‘parameters’ is used but ‘variables’ describes them more succinctly. The most commonly measured variables of the natural environment include the following: solar and terrestrial radiation, air and ground temperature, humidity, evaporation and transpiration, wind speed and direction, rainfall, snowfall, and snow depth, barometric pressure, soil moisture and soil tension, groundwater, river level and flow, water quality (pH, conductivity, turbidity, dissolved oxygen, biochemical oxygen demand, the concentration of specific ions such as nitrates and metals), sea level, sea-surface temperature, ocean currents and waves and the ice of polar regions.