Lindenberg
Since November 20, 2009 we measured at the Meteorological Observatory Lindenberg (Richard-Aßmann-Observatory) with the L52 Lightmeter (03.02 marks V05.05 S / N 908052.1382). The Lightmeter is located on the northwest side of the radiaton platform near two modified MOBOTIX - Hemispheric Q24 security cameras for sky monitoring.
Coordinates: 52°12'32" N 14°07'17" E
Height: 127 m asl (platform)
For the extension of the USB cable from the Lightmeter to the laptop (about 10m), we used the Lindy USB Extender PREMIUM.
Directory listing for DE_LINDENBERG_1
radiation platform, view to south / Strahlungsmessplattform in Lindenberg - Blick nach Süden
lightmeter L52 on the northwest side of the radiation platform in Lindenberg / Lightmeter L52 an der Nordwestseite der Strahlungsmessplattform in Lindenberg
lightmeter L52 and the MOBOTIX-camera / Lightmeter L52 und MOBOTIX-Kamera
results of the first night in Lindenberg 2009-11-20/21 / Ergebnisse der ersten Messnacht in Lindenberg 2009-11-20/21
registration of a bright fireball on May 4, 2011 23:12:35 UTC
Calibration 21 Feb 2010
X = c ( b (a exp (n/a) - 1) + n )
n ... counts (sensor output) X ... physical quantity (total radiation in [W/m²] or horizontal illumination [Lux])
a = 9.776e+04, b= 1.991e-04, c= 2.662e-09 W/m² a = 9.776e+04, b= 1.991e-04, c= 2.538e-07 Lux
Data from morning twilight and daylight, Feb. 17th 2010 2:07 - 11:00 UTC
--GuentherWuchterl 18:43, 21. Feb. 2010 (UTC)
Improved calibration 24 Feb 2010
Checks with a total radiation sensor showed up to 40% deviations near noon. In a new fit the temperature dependence is included and the total radiation model is used for nominal site parameters (dew-point temperature, surface pressure). Data are the same as above (Feb 17th morning twilight to noon).
X = c ( b (a exp (n(1+dT)/a) - 1) + n )
n ... counts (sensor output) X ... physical quantity (total radiation in [W/m²] or horizontal illumination [Lux])
a = 1.0118e+05, b = 4.9571e-04, c = 2.5688e-09, d = 2.3697e-03 [W/m²] a = 1.0118e+05, b = 4.9571e-04, c = 2.3298e-07, d = 2.3697e-03 [Lux]
Background x0=6.3 mlx
Accuracy check with independent total radiation measurement shows the calibration to be accurate to 12%. Note that the Sun used as calibrator never rises higher than 30° during the calibration period and thus accuracy of the total radiation model used for calibration is necessarily limited and the likely accuracy limiting element in the calibration.
There is indication for some cloud towards the begin of the morning twilight near the background.
--GuentherWuchterl 01:25, 24. Feb. 2010 (UTC)
Check, Feb 27th, repetition of calibration procedure:
5:03 - 11:18 UTC
a = 1.0118e5, b = 4.9571e-4, c = 2.5754e-9, d = 2.3697e-3 [W/m²] a = 1.0118e5, b = 4.9571e-4, c = 2.3298e-7, d = 2.3697e-3 [Lux]
X0 = -6.2552e-3 Lux
Conversion Lux-model to Total-radiation model
Lux = 90.465 Watt/m²
Watt/m² = 0.011054 Lux
copies from python-session
In [9]: SJD=(X.JD > mx.DateTime.DateTime(2010,2,17,5,03).jdn)
& (X.JD < mx.DateTime.DateTime(2010,2,17,11,18).jdn)
In [10]: X.fit_em1_to_natLight(JD_select=SJD,type='em1c0T')
Out[10]: (array([ 1.01179142e+05, 4.95712792e-04, 2.32981477e-07
, -6.25516123e-03, 2.36965039e-03]),
plot_date(X.JD-X.pylab_JD0
,X.Sunlight_Watt_per_square_meter_from_JD_DM(X.JD,surface_pressure=998.0,
T_dew_C=-9.0)
*0.778/X.Watt_per_square_meter_per_Lux
,'y,', label='DM model,P=998/T_d=-9/k=2.78')
--> In [44]: 0.778/X.Watt_per_square_meter_per_Lux Out[44]: 90.465116279069775
--> In [45]: 1./(0.778/X.Watt_per_square_meter_per_Lux) Out[45]: 0.011053984575835474
In [59]: plot_date(X.JD-X.pylab_JD0
,X.em1T(X.Strom,X.Temperatur
,1.01179142e+05, 4.95712792e-04, 2.57537e-09
,2.36965039e-03)
,'k,',label="a,b,c,d= 1.01e5, 4.96e-4, 2.58e-9, 2.37e-3"
Notices
For the measurement of global radiation on the observatory we use a CM22 pyranometer from Kipp & Zonen, which are used to measure the intensity of the radiation on flat surfaces.
Weblinks
- Kipp&Zonen CM22 Manual. (engl.)
22:16, 5. Mai 2011 AndreKnoefel