====== Solar radiation measurements ======

Solar radiation measurements are established at the BCO since March 2015.
The typical setup for a measurement station consist of a sun tracker with 3 sensors installed on a table (one shaded pyranometer for diffuse radiation, one not-shaded pyranometer for global radiation and a shaded pyrgeometer for longwave radiation). Aside mounted a heliometer is pointing directly into the sun. 
The date is recorded with a resolution of 1 sec.

{{:observations:bco:radiation.jpg?800|}}

Two sets of sensors are used and exchanged approx. every two years.
  * Set 1: CMP21 #140337, CMP21 #140356, CGR4 #140034, CHP1 #140059 
  * Set 2: CMP21 #160654, CMP21 #160653, CGR4 #150139, CHP1 #160388

Exchange dates are:
  * 16.04.2017
  * 12.01.2020

Calibration of our sensors is done by the DWD in Lindenberg.

==== DATA ACCESS ====
The data is available at
  /pool/OBS/BARBADOS_CLOUD_OBSERVATORY/Level_1/K_Radiation/
and
  /pool/data/OBS/BARBADOS_CLOUD_OBSERVATORY/Level_1/K_Radiation/
on ''levante.dkrz.de''.

The measurements are available since 2015 and a detailed overview about the data availability is given here:
[[http://bcoweb.mpimet.mpg.de/systems/data_availability/DeviceAvailability.html]]


=== EXAMPLE ===
<code python>
import os
import matplotlib.pyplot as plt
import pandas as pd
import xarray as xr

fileformat = '/pool/OBS/BARBADOS_CLOUD_OBSERVATORY/Level_1/K_Radiation/%Y%m/Radiation__Deebles_Point__DownwellingRadiation__1s__%Y%m%d.nc'
dates = pd.date_range('2020-02-01','2020-02-04')

def create_filelist(dates, fileformat):
    """
    Create list of files
    
    Returns list of existing files for
    the given dates and fileformat
    
    Input
    -----
    dates : datetime-like
        List of dates that are of interest
    fileformat : str
        Fileformat of files incl. full path
    
    Returns
    -------
    files : list
        List of files that could be found
    """
    files = []
    for date in dates:
        fn = date.strftime(fileformat)
        if os.path.exists(fn):
            files.append(fn)
    return files


files_available = create_filelist(dates, fileformat)
ds_radiation = xr.open_mfdataset(files_available)
ds_radiation.SWdown_diffuse.plot();
</code>

{{:observations:bco:swradiation_example_timeseries.png?400|}}