SPN1

Marine ARM GPCI Investigations of Clouds (MAGIC): Sunshine Pyranometer (SPN1)

1 August 2012 - 30 September 2013

Lead Scientist: R. Reynolds

Observatory: OSC, MAG

From the SPN1 manual, the SPN1 Sunshine Pyranometer is one sensor with three output channels: (1) Total (global) solar radiation, (2) Diffuse radiation, and (3) sunshine status. The SPN1 measures short wave radiation between 400nm and 2700nm in W.m-2. The Direct beam component of solar radiation can be calculated from the Total minus the Diffuse component. The Sunshine status output indicates whether the energy in the direct beam exceeds the WMO standard threshold value of 120 W.m-2, using an algorithm based on the Total radiation, and the ratio of Total to Diffuse radiation. The radiation outputs have a cosine-corrected response.

A photograph of the Portable Radiation Package with the SPN1 on the right side of the radiometer plate.

The advantages of the SPN1 are (1) It matches the WMO ‘Good Quality’ pyranometer classification. (2) It requires no shadow band or solar tracker. (3) There are no moving parts. (4) It does not need to be adjusted or repositioned to track the sun – a distinct advantage over shade rings or mechanical trackers. (5) It does not need to be oriented towards North. It will work accurately in any orientation as long as it is mounted horizontally. (6) It does not require knowledge of the Latitude or Longitude, and can be used at any Latitude or Longitude. (7) It measures sunshine hours as well as Total and Diffuse radiation. and (8) The built-in heater allows use in wet or icy conditions. Dr. C. Long has been looking into the SPN1 as an instrument that could be of use for the AMF2 system, especially during at-sea times. There are two different outputs from the sensors; an analog output with three different voltages for the three measured channels and a digital output of the same quantities. The SPN1 integration collects both the analog and the digital outputs.