Airborne Measurements for Environmental Research -- 1 Introduction to Airborne Measurements of the Earth Atmosphere and Surface -- 2 Measurement of Aircraft State and Thermodynamic and Dynamic Variables -- 2.1 Introduction -- 2.2 Historical -- 2.3 Aircraft State Variables -- 2.3.1 Barometric Measurement of Aircraft Height -- 2.3.2 Inertial Attitude, Velocity, and Position -- 2.3.2.1 System Concepts -- 2.3.2.2 Attitude Angle Definitions -- 2.3.2.3 Gyroscopes and Accelerometers -- 2.3.2.4 Inertial-Barometric Corrections -- 2.3.3 Satellite Navigation by Global Navigation Satellite Systems -- 2.3.3.1 GNSS Signals -- 2.3.3.2 Differential GNSS -- 2.3.3.3 Position Errors and Accuracy of Satellite Navigation -- 2.3.4 Integrated IMU/GNSS Systems for Position and Attitude Determination -- 2.3.5 Summary, Gaps, Emerging Technologies -- 2.4 Static Air Pressure -- 2.4.1 Position Error -- 2.4.1.1 Tower Flyby -- 2.4.1.2 Trailing Sonde -- 2.4.2 Summary -- 2.5 Static Air Temperature -- 2.5.1 Aeronautic Definitions of Temperatures -- 2.5.2 Challenges of Airborne Temperature Measurements -- 2.5.3 Immersion Probe -- 2.5.4 Reverse-Flow Sensor -- 2.5.5 Radiative Probe -- 2.5.6 Ultrasonic Probe -- 2.5.7 Error Sources -- 2.5.7.1 Sensor -- 2.5.7.2 Dynamic Error Sources -- 2.5.7.3 In-Cloud Measurements -- 2.5.8 Calibration of Temperature Sensors -- 2.5.9 Summary, Gaps, Emerging Technologies -- 2.6 Water Vapor Measurements -- 2.6.1 Importance of Atmospheric Water Vapor -- 2.6.2 Humidity Variables -- 2.6.3 Dew or Frost Point Hygrometer -- 2.6.4 Lyman-α Absorption Hygrometer -- 2.6.5 Lyman-α Fluorescence Hygrometer -- 2.6.6 Infrared Absorption Hygrometer -- 2.6.7 Tunable Laser Absorption Spectroscopy Hygrometer -- 2.6.8 Thin Film Capacitance Hygrometer -- 2.6.9 Total Water Vapor and Isotopic Abundances of 18O and 2H -- 2.6.10 Factors Influencing In-Flight Performance.

2.6.10.1 Sticking of Water Vapor at Surfaces -- 2.6.10.2 Sampling Systems -- 2.6.11 Humidity Measurements with Dropsondes -- 2.6.12 Calibration and In-Flight Validation -- 2.6.13 Summary and Emerging Technologies -- 2.7 Three-Dimensional Wind Vector -- 2.7.1 Airborne Wind Measurement Using Gust Probes -- 2.7.1.1 True Airspeed (TAS) and Aircraft Attitude -- 2.7.1.2 Wind Vector Determination -- 2.7.1.3 Baseline Instrumentation -- 2.7.1.4 Angles of Attack and Sideslip -- 2.7.2 Errors and Flow Distortion -- 2.7.2.1 Parameterization Errors -- 2.7.2.2 Measurement Errors -- 2.7.2.3 Timing Errors -- 2.7.2.4 Errors due to Incorrect Sensor Configuration -- 2.7.3 In-Flight Calibration -- 2.8 Small-Scale Turbulence -- 2.8.1 Hot-Wire/Hot-Film Probes for High-Resolution Flow Measurements -- 2.8.2 Laser Doppler Anemometers -- 2.8.3 Ultrasonic Anemometers/Thermometers -- 2.8.4 Measurements of Atmospheric Temperature Fluctuations with Resistance Wires -- 2.8.5 Calibration of Fast-Response Sensors -- 2.8.6 Summary, Gaps, and Emerging Technologies -- 2.9 Flux Measurements -- 2.9.1 Basics -- 2.9.2 Measurement Errors -- 2.9.3 Flux Sampling Errors -- 2.9.3.1 Systematic Flux Error -- 2.9.3.2 Random Flux Error -- 2.9.4 Area-Averaged Turbulent Flux -- 2.9.5 Preparation for Airborne Flux Measurement -- 3 In Situ Trace Gas Measurements -- 3.1 Introduction -- 3.2 Historical and Rationale -- 3.3 Aircraft Inlets for Trace Gases -- 3.4 Examples of Recent Airborne Missions -- 3.5 Optical In Situ Techniques -- 3.5.1 UV Photometry -- 3.5.2 Differential Optical Absorption Spectroscopy -- 3.5.2.1 Measurement Principle -- 3.5.2.2 Examples of Measurement -- 3.5.3 Cavity Ring-Down Spectroscopy -- 3.5.3.1 Measurement Principle -- 3.5.3.2 Aircraft Implementation -- 3.5.3.3 Calibration and Uncertainty -- 3.5.3.4 Broadband Cavity Spectroscopic Methods.

3.5.4 Gas Filter Correlation Spectroscopy -- 3.5.5 Tunable Laser Absorption Spectroscopy -- 3.5.5.1 Tunable Diode Versus QCLs -- 3.5.5.2 Further Progress -- 3.5.6 Fluorescence Techniques -- 3.5.6.1 Resonance Fluorescence -- 3.5.6.2 LIF Techniques -- 3.5.6.3 Chemical Conversion Resonance Fluorescence Technique -- 3.6 Chemical Ionization Mass Spectrometry -- 3.6.1 Negative-Ion CIMS -- 3.6.1.1 Measurement Principle and Aircraft Implementation -- 3.6.1.2 Calibration and Uncertainties -- 3.6.1.3 Measurement Example -- 3.6.2 The Proton Transfer Reaction Mass Spectrometer -- 3.6.3 Summary and Future Perspectives -- 3.7 Chemical Conversion Techniques -- 3.7.1 Peroxy Radical Chemical Amplification -- 3.7.1.1 Measurement Principles -- 3.7.1.2 Airborne Measurements -- 3.7.1.3 Calibration and Uncertainties -- 3.7.2 Chemiluminescence Techniques -- 3.7.2.1 Measurement Principle -- 3.7.2.2 Measurement of Ozone Using Chemiluminescence -- 3.7.2.3 NOy and NO2 Conversion -- 3.7.2.4 Calibration and Uncertainties -- 3.7.2.5 Measurement Examples -- 3.7.2.6 Summary -- 3.7.3 Liquid Conversion Techniques -- 3.7.3.1 Measurement Principles -- 3.7.3.2 Aircraft Implementation -- 3.7.3.3 Data Processing -- 3.7.3.4 Limitations, Uncertainties, and Error Propagation -- 3.7.3.5 Calibration and Maintenance -- 3.7.3.6 Measurement Examples -- 3.7.3.7 Summary and Emerging Technologies -- 3.8 Whole Air Sampler and Chromatographic Techniques -- 3.8.1 Rationale -- 3.8.2 Whole Air Sampling Systems -- 3.8.2.1 Design of Air Samplers -- 3.8.2.2 The M55-Geophysica Whole Air Sampler -- 3.8.3 Water Vapor Sampling for Isotope Analysis -- 3.8.4 Measurement Examples -- 3.8.5 Off-Line Analysis of VOCs -- 3.8.5.1 Air Mass Ageing -- 3.8.5.2 Using VOC Observations to Probe Radical Chemistry -- 4 In Situ Measurements of Aerosol Particles -- 4.1 Introduction -- 4.1.1 Historical Overview.

4.1.2 Typical Mode Structure of Aerosol Particle Size Distribution -- 4.1.3 Quantitative Description of Aerosol Particles -- 4.1.4 Chapter Structure -- 4.2 Aerosol Particle Number Concentration -- 4.2.1 Condensation Particle Counters -- 4.2.2 Calibration of Cut-Off and Low-Pressure Detection Efficiency -- 4.3 Aerosol Particle Size Distribution -- 4.3.1 Single-Particle Optical Spectrometers -- 4.3.1.1 Measurement Principles and Implementation -- 4.3.1.2 Measurement Issues -- 4.3.2 Aerodynamic Separators -- 4.3.3 Electrical Mobility Measurements of Particle Size Distributions -- 4.3.4 Inversion Methods -- 4.4 Chemical Composition of Aerosol Particles -- 4.4.1 Direct Offline Methods -- 4.4.2 Direct Online Methods (Aerosol Mass Spectrometer, Single Particle Mass Spectrometer, and Particle-Into-Liquid Sampler) -- 4.4.2.1 Bulk Aerosol Collection and Analysis -- 4.4.2.2 Mass Spectrometric Methods -- 4.4.2.3 Incandescence Methods -- 4.4.3 Indirect Methods -- 4.5 Aerosol Optical Properties -- 4.5.1 Scattering Due to Aerosol Particles -- 4.5.2 Absorption of Solar Radiation Due to Aerosol Particles -- 4.5.2.1 Filter-Based Methods -- 4.5.2.2 In Situ Methods -- 4.5.2.3 Airborne Application -- 4.5.3 Extinction Due to Aerosol Particles -- 4.5.4 Inversion Methods -- 4.6 CCN and IN -- 4.6.1 CCN Measurements Methods -- 4.6.2 IN Measurement Methods -- 4.6.3 Calibration -- 4.6.3.1 CCN Instrument Calibration -- 4.6.3.2 IN Instrument Calibration -- 4.7 Challenges and Emerging Techniques -- 4.7.1 Particle Number -- 4.7.2 Particle Size -- 4.7.3 Aerosol Optical Properties -- 4.7.4 Chemical Composition of Aerosol Particles -- 4.7.5 CCN Measurements -- 4.7.6 IN Measurements -- 5 In Situ Measurements of Cloud and Precipitation Particles -- 5.1 Introduction -- 5.1.1 Rationale -- 5.1.2 Characterization of Cloud Microphysical Properties -- 5.1.3 Chapter Outline.

5.1.4 Statistical Limitations of Airborne Cloud Microphysical Measurements -- 5.2 Impaction and Replication -- 5.2.1 Historical -- 5.2.2 Measurement Principles and Implementation -- 5.2.3 Measurement Issues -- 5.3 Single-Particle Size and Morphology Measurements -- 5.3.1 Retrieval of the PSD -- 5.3.1.1 Correction of Coincidence Effects -- 5.3.1.2 Optimal Estimation of the Particle Concentration -- 5.3.2 Single-Particle Light Scattering -- 5.3.2.1 Measurement Principles and Implementation -- 5.3.2.2 Measurement Issues -- 5.3.2.3 Summary -- 5.3.3 Single-Particle Imaging -- 5.3.3.1 Measurement Principles and Implementation -- 5.3.3.2 Measurement Issues -- 5.3.3.3 Summary -- 5.3.4 Imaging of Particle Ensembles - Holography -- 5.4 Integral Properties of an Ensemble of Particles -- 5.4.1 Thermal Techniques for Cloud LWC and IWC -- 5.4.1.1 Hot-Wire Techniques -- 5.4.1.2 Mass-Sensitive Devices -- 5.4.1.3 Measurement Issues -- 5.4.2 Optical Techniques for the Measurement of Cloud Water -- 5.4.2.1 The PVM -- 5.4.2.2 Angular Optical Cloud Properties -- 5.4.2.3 The PN -- 5.4.2.4 The CIN -- 5.4.2.5 The CEP -- 5.4.2.6 Measurement Issues -- 5.5 Data Analysis -- 5.5.1.1 Adjustment to Adiabaticity -- 5.5.1.2 Instrument Intercalibration -- 5.5.1.3 Instrument Spatial Resolution -- 5.5.1.4 Integrating Measurements from Scattering and Imaging Probes -- 5.5.1.5 Integrating Cloud Microphysical and Optical Properties -- 5.5.1.6 Evaluation of OAP Images -- 5.6 Emerging Technologies -- 5.6.1 Interferometric Laser Imaging for Droplet Sizing -- 5.6.2 The Backscatter Cloud Probe -- 5.6.3 The Cloud Particle Spectrometer with Depolarization -- 5.6.4 Hawkeye Composite Cloud Particle Probe -- Acknowledgments -- 6 Aerosol and Cloud Particle Sampling -- 6.1 Introduction -- 6.2 Aircraft Influence -- 6.2.1 Flow Perturbation -- 6.2.2 Particle Trajectories -- 6.2.3 Measurement Artifacts.

6.3 Aerosol Particle Sampling.