Dear Jim,
My experience with Bellani type instruments  (Which was in the 1960's and
1970's) are that they are very finicky and they require individual
calibration. As far as net radiometers go, I concur with Gerrit Hoogeboom's
experience, but if you have these at your experimental site and have daily
supervision, they are fine.
Louis du Pisani
-----Original Message-----
From: James Hansen <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, September 12, 2000 8:35 PM
Subject: solar radiation data conversion


>Dear Colleagues,
>
>I need some help or literature on solar radiation instrumentation.  In
>particular, I need to convert daily irradiance measurements from a
>spherical (Bellani) net radiometer to global irradiance normal to a
>horizontal surface for crop simulation applications in Southern India.
>Intuitively, the response to diurnal and seasonal changes in solar
>angles will clearly be different between a spherical and a flat sensor.
>I assume that someone has worked out and validated an algorithm for
>converting between the two sensor shapes.  I will be grateful for your
>help.
>
>Regards,
>--
>Dr. James W. Hansen
>Associate Research Scientist - Agricultural Systems
>International Research Institute for Climate Prediction
>P.O. Box 1000
>Palisades, NY 10964-8000
>USA
>
>845-680-4410 (voice)
>845-680-4864 (fax)
>
>Please note that the IRI area code 914 is changing to 845. If you
>experience difficulty with 845, 914 will work through 31 December 2000.
>