Table of Contents
Chapter 5: Element Field and Element Code Descriptions
The following table converts other common units to the measurement units specified by
the SERI Stan dard Broadband Format. Both energy-flux units and power-flux units are
given for solar radiation measurements, thereby allowing conversion between types of
units. For example, an average power density of 1.0 W/m^2 over 1 min is equal to 0.
06 kJ/m of energy density.
Common solar radiation measurement units are langleys, Btus per square foot, kilojoules per square meter, and watts per square meter. In order to adhere to standard international (SI) units, only kilojoules per square meter and watts per square meter were considered for SBF. The energy-flux unit, kilojoules per square meter, causes scaling problems that are typically resolved by altering the magnitude of the unit. Thus, l-min and hourly data can be recorded compactly as kilojoules per square meter, but daily data would be recorded in megajoules per square meter and yearly data in gigajoules per square meter. This situation creates an unwanted ambiguity. In addition, recording in kilojoules per square meter causes an additional problem. The units of energy, as integrals, do not lend themselves to comparisons between measurement time intervals. For example, it is not immediately obvious that a l-min radiation measurement of 48 kJ/m^2 is equivalent to a 15-min radiation measurement of 720 kJ/m^2.
Recording with the power-flux unit, watts per square meter, removes both the ambiguity and comparison problems. It is no longer necessary for the user to maintain multiple units for various measurement time intervals. All radiation values can be expressed in the same range (0-2000 W/m^2). Also, comparison is simplified because the user is not comparing apples and oranges. With the example given for kilojoules, it is readily apparent to the user that a l-min radiation measurement is equivalent to a 15-min measurement when the values are given in watts per square meter (in this case, both equal 800 W/m). A daily, value in SBF can be converted from an average daily value (watts per square meter) to an integrated daily value (watts per square meter) by multiplying by 24 (hours).
_______________________________________________________________ To Convert From To Multiply By _______________________________________________________________ W/m^2 kJ/m^2 0.06 W/m^2 langley/min 0.001433 w/m^2 cal/cm^2 min 0.001433 w/m^2 Btu/ft^2 min 0.005285 kJ/m^2 W/m^2 16.66667 langley/min W/m^2 697.3 cal/cm^2 min W/m^2 697.3 Btu/ft^2 min w/m 189.1
_______________________________________________________________ To Convert From To Multiply By _______________________________________________________________ W/m^2 kJ/m^2 3.6 W/m^2 langley/hour 0.0858 W/m^2 cal/cm^2 hour 0.0858 W/m^2 Btu/ft^2 hour 0.317 W/m^2 kWh/m^2 0.024 kJ/m^2 W/m^2 0.27 langley/hour W/m^2 11.622 cal/cm^2 hour W/m^2 11.622 Btu/ft^2 hour W/m^2 3.152 kWh/m^2 W/m^2 41.66
_____________________________________________________________ To Convert From To Multiply By _____________________________________________________________ kPa millibars 10. millibar kPa 0.1
_____________________________________________________________ To Convert From To Multiply By _____________________________________________________________ m/s mph 2.2369 mph m/s 0.44704 knot m/s 51.44
_____________________________________________________________ To Convert From To Multiply By _____________________________________________________________ mm in. 0.03937 in. mm 25.4
_____________________________________________________________
To Convert From To Multiply By
_____________________________________________________________
Celsius Fahrenheit multiply by 1.8
and add 32
Fahrenheit Celsius subtract 32 and
multiply by 0.555
Appendix C: Cloud Layer Observations
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