Instrument calibrations are both one of the most important, and yet sometimes one of the most neglected, areas of weather measurement. This chapter describes straightforward methods to check and adjust calibrations for the most common meteorological instruments – precipitation (rainfall), temperature, humidity and air pressure sensors. To reduce uncertainty in the measurements themselves, meteorological instruments need to be accurately calibrated, or at least regularly compared against instruments of known calibration to quantify and adjust for any differences, or error. Calibrations can and do drift over time, and therefore instrumental calibrations should be checked regularly, and adjusted if necessary.

The term ‘humidity’ refers to the amount of water vapour in the air. The physics of water vapour is one of the main components of the atmospheric heat engine which produces ‘weather’ and as a result, humidity measurements are an essential requirement for operational meteorological analysis and forecasting, for climate studies, hydrology, agriculture and many other areas of human activity and comfort. In the meteorological context, the terms relative humidity (RH) and dew point (Td) are most often used in specifying atmospheric water vapour content. This chapter sets out how humidity measurements are made, following guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation), including those from chilled mirror hygrometers, a dry and wet bulb psychrometer and electronic humidity sensors. Limitations of existing methods in some circumstances, such as air temperatures below freezing point, are covered.

In order to provide representative measurements of grass, soil or earth temperatures, thermometers must be deployed in suitable locations or sites and the sensors themselves exposed in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of grass, soil or earth temperatures, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). As a result of the UN Minamata Convention, traditional mercury-based thermometers have been progressively withdrawn from observation networks, and this chapter considers both their replacement by electronic sensors and impacts of that changeover.

Metadata is literally ‘data about data’. In the context of meteorological records, metadata covers the description of the observation site and its surroundings, the instruments in use and their units together with any significant changes over time, and any other relevant information, such as where the site’s records are archived. Its importance lies in providing essential information for any other user of the records to understand more about the location and characteristics of the data, and therefore enables more informed use of the data. Metadata are especially important for elements which are particularly sensitive to exposure, such as precipitation, wind and temperature, and for professional sites, especially so for long-period records. This chapter sets out what should be recorded, following guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation).

There are enormous differences in functionality and capability between basic and advanced weather stations. This chapter outlines typical system specifications within broad capability and budget boundaries. When used with the prioritized assessments of functionality from the previous chapter, it will provide clearer guidance regarding the main brands, products and suppliers within the automatic weather station sectors.

A modern automatic weather station (AWS) is a sophisticated collection of various components, sensors and electronics modules tied together by software, together making up a data acquisition and processing system. Many of today and tomorrow’s products follow a broadly similar set of basic processes, and this chapter sets out to explain these basic processing steps, keeping technical terminology to a minimum, and illustrating three different approaches to ‘system architecture’. The oversight provided by this chapter provides familiarity with the key concepts, system approaches and application types, and from there users can review potential products and suppliers using Internet search facilities to gather up-to-date product information.

In order to provide representative measurements of wind speed and direction, measuring devices must be deployed in suitable locations or sites and the instruments themselves exposed to the wind they are intended to measure in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of wind speed and direction, including the treatment of wind gusts and construction of the vector mean wind, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). Well-exposed sites can be difficult to find, and optimal exposure conditions for wind instruments differ considerably from most other meteorological instruments. Instruments to measure both wind speed (cup and sonic anemometers) and wind direction (wind vanes and sonic anemometers) are covered, with their limitations, together with a description of the Beaufort wind scale, which is useful if suitable instruments (or a suitable site for them) are not available.

Each of the previous chapters in this book is summarized in a ‘One minute summary’; this final chapter brings all of those ‘One minute summaries’ and the page numbers for that chapter together for ease of reference. Alongside the subject index, this arrangement permits rapid reference and recall to any of the information contained within this book.

This chapter builds upon the suggested ways of collecting and storing data outlined in the previous chapter, to show how quickly and easily presentation-quality graphics and sophisticated statistical analyses of meteorological records can be generated using everyday software, assuming a reasonable working knowledge of spreadsheets or other data processing methods. Numerous examples are presented to aid understanding and provide a starting point for those with more limited spreadsheet literacy: there are also many excellent book and video-based tutorials available for all software literacy levels. Readers are encouraged to use these ideas and concepts to develop their own projects using their own observational records. Practice quickly builds into expertise.

Every day, millions of weather measurements are made by people and automated sensors across the globe, on land, over the oceans, in the upper reaches of the atmosphere and from space, providing the raw data essential to supercomputer-based weather forecasting models that are vital to modern economies. This chapter provides an introduction to making weather observations, for all levels of ability and motivation, from weather enthusiasts to professional users. In doing so, the history of early meteorological instruments and observers is covered, together with details of many of the locations around the world where continuous weather and climate observations have been made for well over 100 years.

For weather measurements to be comparable between different locations, the time (or times) at which observations are made, and the period covered by the measurements, should be common as far as possible. By convention, operational weather measurements throughout the world are made to a common time standard, using Coordinated Universal Time (UTC). The World Meteorological Organization (WMO) provides guidance on observation times for the main international ‘synoptic’ observing networks, while ‘climatological’ observing practice tends to be defined at a country or regional level. This chapter outlines common observing routines, with examples based upon current practice given to illustrate generally applicable principles. The importance of common time standards and common time period/s for once-daily values, such as maximum temperature or total rainfall, are stated, and the meaning, relevance and importance of ‘terminal hours’ is introduced.

In order to provide representative measurements of solar radiation and sunshine duration, measuring devices must be deployed in suitable locations or sites and the instruments themselves exposed to the sky in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of solar radiation (direct, global and diffuse solar radiation) and sunshine duration, following guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). Suitably exposed sites can be difficult to find, and unlike other meteorological instruments a mast or rooftop exposure may be ideal. Various instruments have been developed to measure sunshine over the past two centuries, including a variety of recent electronic sensors, but exact agreement between different sensors with varying methods of operation has proved problematic, and the implications for long-period sunshine records are discussed.

In order to provide representative measurements of air temperature, thermometers must be deployed in suitable locations or sites and the sensors themselves exposed to the weather conditions they are intended to measure in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of air temperature, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). As a result of the UN Minamata Convention, traditional mercury-based thermometers have been progressively withdrawn from observation networks, and this chapter considers both their replacement by electronic sensors and impacts of that changeover. Alternative methods to measuring air temperature in the traditional Stevenson screen or Cotton Region Shelter, particularly aspirated temperature measurements, are also covered in detail.

In order to provide representative measurements of precipitation (rainfall, snow and hail, drizzle, sleet and so on), measuring devices must be deployed in suitable locations or sites and the instruments themselves exposed to the weather conditions they are intended to measure in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of precipitation, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). Both manual and automated (recording) raingauge measurements are covered in detail, including tipping bucket, ground flush or pit gauges and weighing gauges, together with methods to decrease losses due to wind. Snowfall measurement methods are also covered.

Weather knows no boundaries. Interest in ‘measuring the weather’ at any particular location is greatly enhanced by exchange and comparison of observations with others – locally/regionally, nationally or internationally. This chapter suggests ways to exchange information with other sites and other observers, under three main headings – online or real-time sharing using the Internet, online or offline reporting to informal or voluntary networks and co-operation with national weather services and other official bodies.

Making best use of collected weather observations is simplified where thought is given to record management and storage: gathering meteorological records is usually a means to an end, rather than an end in itself. The more effectively records are stored, the quicker and easier it becomes to analyse and use them productively – a statement which applies equally to both professional and amateur observers. This chapter provides tried and tested suggestions for collecting, storing and archiving data from both manual observations and automatic weather stations (AWSs).

Atmospheric pressure is one of the most important of all meteorological elements. Fortunately, it is also the easiest of all to measure, particularly with modern sensors, and even basic instruments such as household aneroid barometers or smartphones can provide reasonably accurate readings. To ensure consistent and reliable readings for professional applications, for instance aviation requirements, it is essential that pressure sensors are correctly exposed: World Meteorological Organization recommendations on exposure and instrument accuracy are included. Instructions are given to correct or ‘reduce’ observed atmospheric pressure readings to a standard level, usually mean sea level (MSL), and to check and adjust the calibration of pressure sensors to avoid calibration drift, which can become substantial if not corrected. Methods for doing this are explained, with examples.

There are many different varieties of automatic weather stations (AWSs) available, and a huge range of different applications for them. This chapter suggests a structured approach to specifying AWS features to meet any particular requirement, provides a short guide to AWS products and services available (from consumer brands to sophisticated professional systems capable of unattended operation in remote areas) and offers guidance in selecting one or more options from the multiplicity of product offerings on the market.

In order to provide representative measurements of meteorological conditions, instruments must be deployed in suitable locations or sites, while the instruments themselves must be exposed to the weather conditions they are intended to measure in a standardized manner. This chapter sets out what those standardised conditions of site and exposure are, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation).