weight three cup anemometers (Section 2.1.1) or propeller anemometers
(Section 2.1.2) should be used for
measuring wind speed. Sensors with high accuracy at low wind speeds and a
low starting threshold should be used (see Section 5). Light weight, low
friction systems which meet the performance specifications given in Section
5.0 should be used. Heaters should be employed to protect against icing in
cold climates. Sonic anenometers and hot wire panenometers
may be used with the approval of the reviewing authority. These instruments
are especially suited for use in direct measurements of turbulence.
direction should be measured directly using a wind vane (Section 2.2.1) or
may be derived from measurements of wind speed components (Section 2.2.2).
Light weight, low friction systems which meet the performance specifications
given in Section 5.0 should be used. Heaters should be employed to protect
against icing in cold climates. Bivanes are regarded as research grade
instruments and are not generally suited for routine monitoring. Data from
bivanes may be used on a case by case basis with the approval of the
and temperature difference should be measured using resistance temperature
devices which meet the performance specifications of Section 5.0.
Thermoelectric sensors (thermocouples) are not recommended because of their
limited accuracy and complex circuitry.
should be measured using a dew point, lithium chloride, or thin-film
capacitorhygrometer. The hygrometer should meets the performance
specifications in Section 5.0.
should be measured with a weighing or tipping bucket rain gauge. In cold
climates, the gauge should be equipped with a heater and a wind shield.
pressure should be measured with an aneroid barometer which meets the
performance specifications given in Section 5.0
class or second class pyranometers should normally be used for measuring
global solar radiation, depending on the application. If the solar radiation
data are to be used in procedures for estimating stability (Section 6.4)
then second class (photovoltaic) pyranometers are acceptable. For most other
applications, first class or secondary standard pyranometers should be used.
Applications requiring ultraviolet (UV) radiation data should not employ
photovoltaic measurements as these instruments are not sensitive to UV
2. PRIMARY METEOROLOGICAL VARIABLES
2.1 Wind Speed
2.1.1 Cup Anemometers
2.1.2 Vane-oriented and Fixed-mount Propeller Anemometers
2.1.3 Wind Speed Transducers
2.2 Wind Direction
2.2.1 Wind Vanes
2.2.2 U-V and UVW Systems
2.2.3 Wind Direction Transducers
2.2.4 Standard Deviation and Turbulence
2.3 Temperature and Temperature Difference
2.3.1 Classes of Temperature Sensors
2.3.2 Response Characteristics
2.3.3 Temperature Difference
2.3.4 Sources of Error
2.4.1 Humidity Variables
2.4.2 Types of Instrumentation
performance specifications for the primary meteorological variables are
provided in Table 5-1