1Izaña Atmospheric Research Center, State Meteorological Agency of Spain (AEMET), Santa Cruz de Tenerife, Spain
2Cimel Electronique, Paris, France
Received: 01 Dec 2012 – Discussion started: 22 Jan 2013
Abstract. In this paper we present the preliminary results of atmospheric column-integrated precipitable water vapor (PWV) obtained with a new Lunar Cimel photometer (LC) at the high mountain Izaña Observatory in the period July–August 2011. We have compared quasi-simultaneous nocturnal PWV from LC with PWV from a Global Positioning System (GPS) receiver and nighttime radiosondes (RS92). LC data have been calibrated using the Lunar Langley method (LLM). We complemented this comparative study using quasi-simultaneous daytime PWV from Cimel AERONET (CA), GPS and RS92. Comparison of daytime PWV from CA shows differences between GPS and RS92 up to 0.18 cm. Two different filters, with and approximate bandwidth of 10 nm and central wavelengths at 938 nm (Filter#1) and 937 nm (Filter#2), were mounted onto the LC. Filter#1 is currently used in operational AERONET sun photometers. PWV obtained with LC-Filter#1 showed an overestimation above 0.18 and 0.25 cm compared to GPS and RS92, respectively, and root-mean-square errors (RMSEs) up to 0.27 cm and 0.24 cm, respectively. Filter#2, with a reduced out-of-band radiation, showed very low differences compared with the same references (≤ 0.05 cm) and RMSE values ≤ 0.08 cm in the case of GPS precise orbits.
Revised: 17 Jul 2013 – Accepted: 20 Jul 2013 – Published: 29 Aug 2013
These results demonstrate the ability of the new lunar photometer to obtain accurate and continuous PWV measurements at night, and the remarkable influence of the filter's transmissivity response to PWV determination at nighttime. The use of enhanced bandpass filters in lunar photometry, which is affected by more important inaccuracies than sun photometry, is necessary to infer PWV with similar precision to AERONET.
Barreto, A., Cuevas, E., Damiri, B., Romero, P. M., and Almansa, F.: Column water vapor determination in night period with a lunar photometer prototype, Atmos. Meas. Tech., 6, 2159-2167, doi:10.5194/amt-6-2159-2013, 2013.