Meteorological Measurements and Instrumentation

Giles Harrison is Professor of Atmospheric Physics at the Department of Meteorology at the University of Reading, UK. His research focusses on one of the oldest experimental topics in meteorology, atmospheric electricity, and the development of new surface and balloon-carried instruments for environmental measurements.

This book describes the fundamental scientific principles underlying high quality instrumentation used for environmental measurements. It discusses a wide range of in situ sensors employed in practical environmental monitoring and, in particular, those used in surface based measurement systems. It also considers the use of weather balloons to provide a wealth of upper atmosphere data. To illustrate the technologies in use it includes many examples of real atmospheric measurements in typical and unusual circumstances, with a discussion of the electronic signal conditioning, data acquisition considerations and data processing principles necessary for reliable measurements. This also allows the long history of atmospheric measurements to be placed in the context of the requirements of modern climate science, by building the physical science appreciation of the instrumental record and looking forward to new and emerging sensor and recording technologies.

This book describes the fundamental scientific principles underlying high quality instrumentation used for environmental measurements. It discusses a wide range of in situ sensors employed in practical environmental monitoring and, in particular, those used in surface based measurement systems.

Series Foreword xi
 
Preface xiii
 
Acknowledgements xv
 
Disclaimer xvii
 
1 Introduction 1
 
1.1 The instrumental age 2
 
1.2 Measurements and the climate record 2
 
1.3 Clouds and rainfall 3
 
1.4 Standardisation of air temperature measurements 4
 
1.5 Upper air measurements 5
 
1.5.1 Manned balloon ascents 6
 
1.5.2 Self-reporting upper air instruments 7
 
1.6 Scope and structure 8
 
2 Principles of Measurement and Instrumentation 9
 
2.1 Instruments and measurement systems 9
 
2.1.1 Instrument response characterisation 10
 
2.1.2 Measurement quality 12
 
2.2 Instrument response time 14
 
2.2.1 Response to a step-change 14
 
2.2.2 Response to an oscillation 15
 
2.3 Deriving the standard error 18
 
2.3.1 Sample mean 18
 
2.3.2 Standard error 20
 
2.3.3 Quoting results 20
 
2.4 Calculations combining uncertainties 21
 
2.4.1 Sums and differences 21
 
2.4.2 Products and quotients 22
 
2.4.3 Uncertainties from functions 23
 
2.5 Calibration experiments 23
 
3 Electronics and Analogue Signal Processing 27
 
3.1 Voltage measurements 28
 
3.2 Signal conditioning 28
 
3.2.1 Operational amplifiers 29
 
3.2.2 Operational amplifier fundamentals 30
 
3.2.3 Signal amplification 31
 
3.2.4 Buffer amplifiers 33
 
3.2.5 Inverting amplifier 33
 
3.2.6 Line driving 35
 
3.2.7 Power supplies 36
 
3.3 Voltage signals 38
 
3.3.1 Electrometers 38
 
3.3.2 Microvolt amplifier 40
 
3.4 Current measurement 41
 
3.4.1 Current to voltage conversion 42
 
3.4.2 Photocurrent amplifier 43
 
3.4.3 Logarithmic measurements 44
 
3.4.4 Calibration currents 45
 
3.5 Resistance measurement 46
 
3.5.1 Thermistor resistance measurement 46
 
3.5.2 Resistance bridge methods 47
 
3.6 Oscillatory signals 50
 
3.6.1 Oscillators 50
 
3.6.2 Phase-locked loops 53
 
3.6.3 Frequency to voltage conversion 54
 
3.7 Physical implementation 54
 
4 Data Acquisition Systems and Initial Data Analysis 57
 
4.1 Data acquisition 57
 
4.1.1 Count data 59
 
4.1.2 Frequency data 60
 
4.1.3 Interval data 60
 
4.1.4 Voltage data 61
 
4.1.5 Sampling 63
 
4.1.6 Time synchronisation 66
 
4.2 Custom data logging systems 66
 
4.2.1 Data acquisition cards 67
 
4.2.2 Microcontroller systems 67
 
4.2.3 Automatic Weather Stations 68
 
4.3 Management of data files 69
 
4.3.1 Data logger programming 69
 
4.3.2 Data transfer 70
 
4.3.3 Data file considerations 71
 
4.4 Preliminary data examination 72
 
4.4.1 In situ calibration 72
 
4.4.2 Time series 73
 
4.4.3 Irregular and intermittent time series 75
 
4.4.4 Further data analysis 75
 
5 Temperature 77
 
5.1 The Celsius temperature scale 77
 
5.2 Liquid in glass thermometry 78
 
5.2.1 Fixed interval temperature scales 78
 
5.2.2 Liquid-in-glass thermometers 79
 
5.3 Electrical temperature sensors 80
 
5.3.1 Thermocouple 81
 
5.3.2 Semiconductor 81
 
5.3.3 Thermistor 82
 
5.3.4 Metal resistance thermometry 83
 
5.4 Resistance thermometry considerations 86
 
5.4.1 Thermistor measurement 87
 
5.4.2 Platinum resistance measurement 89
 
5.5 Thermometer exposure 90
 
5.5.1 Radiatio