Water vapour retrieval using the Precision Solar Spectroradiometer

Abstract

Abstract. The Precision Solar Spectroradiometer (PSR) is a new spectroradiometer developed at PhysikalischMeteorologisches Observatorium Davos -World Radiation Center (PMOD-WRC), Davos, measuring direct solar irradiance at the surface, in the 300-1020 nm spectral range and at high temporal resolution. The purpose of this work is to investigate the instrument's potential to retrieve integrated water vapour (IWV) using its spectral measurements. Two different approaches were developed in order to retrieve IWV: the first one uses single-channel and wavelength measurements, following a theoretical water vapour high absorption wavelength, and the second one uses direct sun irradiance integrated at a certain spectral region. IWV results have been validated using a 2-year data set, consisting of an AERONET sun-photometer Cimel CE318, a Global Positioning System (GPS), a microwave radiometer profiler (MWP) and radiosonde retrievals recorded at Meteorological Observatorium Lindenberg, Germany. For the monochromatic approach, better agreement with retrievals from other methods and instruments was achieved using the 946 nm channel, while for the spectral approach the 934-948 nm window was used. Compared to other instruments' retrievals, the monochromatic approach leads to mean relative differences up to 3.3 % with the coefficient of determination (R 2 ) being in the region of 0.87-0.95, while for the spectral approach mean relative differences up to 0.7 % were recorded with R 2 in the region of 0.96-0.98. Uncertainties related to IWV retrieval methods were investigated and found to be less than 0.28 cm for both methods. Absolute IWV deviations of differences between PSR and other instruments were determined the range of 0.08-0.30 cm and only in extreme cases would reach up to 15 %.

Aerosol retrievals from the EKO MS-711 spectral direct irradiance measurements and corrections of the circumsolar radiation

“…where u H 2 O is the column water vapour content (precipitable water) taken from a global navigation satellite system (GNSS) receiver that considers satellite precise orbits at IZO (Romero Campos et al, 2009); A H 2 O is the spectral absorption coefficient (Rothman et al, 2013); and the b H 2 O exponent depends on the central wavelength position, instrument filter function, as well as the atmosphere pressure and temperature (Halthore et al, 1997). We have determined τ H 2 O (λ) from the transmittance for different water vapour and solar zenith angle (SZA) values from the MODerate resolution atmospheric TRANsmission (MODTRAN) model (Raptis et al, 2018).…”

“…Cachorro et al (2009) compared the AOD retrievals from LI-COR and a sun photometer and found AOD differences within 0.02 in the range of 440-1200 nm. Kazadzis et al (2018a) presented the results from the fourth WMO filter radiometer comparison for AOD measurements and found an excellent agreement at 500 and 865 nm between the Precision Solar Spectroradiometer (PSR; Raptis et al, 2018), Precision Filter Radiometer (PFR; Wehrli, 2008), and overestimation from 0.01 to 0.03 respectively. López-Solano et al (2018) compared AOD retrievals from Brewer spectrophotometers, AERONET-Cimel, and UV-PFR in the range of 300-320 nm at the Izaña Atmospheric Observatory, with uncertainties lower than 0.05.…”

“…However, spectroradiometers offer the possibility of providing other atmospheric components (e.g. O 3 , NO 2 , SO 2 , CH 4 , and H 2 O; Michalsky et al, 1995;Cachorro et al, 1996;Schmid et al, 2001; Barreto et al, 2014;Raptis et al, 2018).…”

Characterization of an EKO MS-711 spectroradiometer: aerosol retrieval from spectral direct irradiance measurements and corrections of the circumsolar radiation

“…receiver considering satellite precise orbits at IZO (Romero Campos et al, 2009), A H 2 O the spectral absorption coefficient Rothman et al (2013), and the b exponent depends on the central wavelength position, instrument filter function, as well as the atmosphere pressure and temperature (Halthore et al, 1997). We have determined τ H 2O (λ) from the transmittance for different water vapour and solar zenith angle (SZA) values from the MODTRAN model (Raptis et al, 2018).…”

Assessment of the total precipitable water from a sun-photometer, microwave radiometer and radiosondes at a continental site in southeastern Europe

“…From the ground the most common ones include the GPS system (Mears et al, 2015), microwave radiometers (Westwater and Guiraud, 1980), Cimel sunphotometers (Halthore et al, 1997;Holben et al, 1998), FTIR (Sussmann et al, 2009) and Raman lidars (Ferrare et al, 1995;Filioglou et al, 2017). Recently, techniques have been developed for the retrieval of TPW from measurements of the precision solar spectroradiometer at World Radiation Center (WRC) Davos (Raptis et al, 2018), the PESR/PREDE-POM sun-sky radiometers (Campanelli et al, 2018) and from Max-DOAS observations (Wagner et al, 2013).…”