Meteorological Instrument Performance Characteristics

Introduction

Users of instruments need information about the performance characteristics of instruments and how these characteristics are determined and documented if they are to make reliable measurements and report measurement characteristics. Users of measurements need this knowledge if they are to reach valid conclusions based on those measurements.

The lesson begins by exploring static performance characteristics, which leads naturally to a discussion of calibration as the means of determining the values of the performance parameters of a sensor or instrument. This is followed by a thorough description of dynamic performance characteristics and responses to first and second order inputs using three classic examples: step or impulse, ramp or time varying, and oscillatory inputs.

The instruments used by atmospheric scientists sample the characteristics of a medium that is constantly changing and is subject to modification by upstream influences as well as the local setting. These attributes are discussed in a section on the general characteristics of measurements, focusing on representativeness and homogeneity of the region affecting the measurement.

The last section is devoted to the quantitative estimate of uncertainty, adhering to the standard evaluation methodologies and expressions employed by the National Institute of Standards and Technology (NIST).

photo of instrumentation set up for observing variations in the atmospheric boundary layer

An array of 3D sonic anemometers is deployed for a surface-layer turbulence study. Image from NCAR/EOL.