Proyecto de Investigación: HALOGENOS EN LA ATMOSFERA ANTARTICA Y SU IMPLICACION EN LA DISTRIBUCION DE OZONO
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CTM2013-41311-P
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Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign
(European Geoscience Union (EGU), 2021-01-04) Tirpitz, J. L.; Frieb, U.; Hendrick, F.; Alberti, C.; Allaart, M.; Apituley, A.; Bais, A.; Beirle, S.; Berkhout, S.; Bognar, K.; Bösch, T.; Bruchkouski, I.; Cede, A.; Lok Chan, K.; Den Hoed, M.; Donner, S.; Drosoglou, T.; Fayt, C.; Friedrich, M. M.; Frumau, A.; Gast, L.; Gielen, C.; Gómez Martín, L.; Hao, N.; Hensen, A.; Henzing, B.; Hermans, C.; Jin, J.; Kreher, K.; Kuhn, J.; Lampel, J.; Li, A.; Liu, C.; Liu, H.; Ma, J.; Merlaud, A.; Peters, E.; Pinardi, G.; Piters, Ankie.; Platt, U.; Puentedura, O.; Richter, A.; Schmitt, S.; Spinei, E.; Stein Zweers, D.; Strong, K.; Swart, D.; Tack, F.; Tiefengraber, M.; Van der Hoff, R.; Van Roozendael, M.; Vlemmix, T.; Vonk, J.; Wagner, T.; Wang, Y.; Wang, Z.; Wenig, M.; Wiegner, M.; Wittrock, F.; Xie, P.; Xing, C.; Xu, J.; Yela González, M.; Zhang, C.; Zhao, X.; European Space Agency (ESA); European Commission (EC); Canadian Space Agency; National Natural Science Foundation of China (NSFC); Natural Sciences and Engineering Research Council of Canada; Deutsche Forschungsgemeinschaft (DFG); European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Frieß, U. [0000-0001-7176-7936]; Alberti, C. [0000-0002-1574-5393]; Apituley, A. [0000-0001-8821-6348]; Bais, A. [0000-0003-3899-2001]; Beirle, S. [0000-0002-7196-0901]; Berkhout, S. [0000-0001-5447-8868]; Bognar, K. [0000-0003-4619-2020]; Bösch, T. [0000-0003-4230-8129]; Donner, S. [0000-0001-8868-167X]; Frumau, A. [0000-0001-5940-0285]; Gómez Martín, L. [0000-0002-6655-7659]; Henzing, B. [0000-0001-6456-8189]; Lampel, J. [0000-0001-7370-9342]; Liu, C. [0000-0002-3759-9219]; Ma, J. [0000-0002-9510-5432]; Peters, E. [0000-0002-8380-3137]; Pinardi, G. [0000-0001-5428-916X]; Puentedura, O. [0000-0002-4286-1867]; Richter, A. [0000-0003-3339-212X]; Stein Zweers, D. [0000-0002-1180-5790]; Strong, K. [0000-0001-9947-1053]; Swart, D. [0000-0002-6128-337X]; Vlemmix, T. [0000-0003-2584-3402]; Wang, Y. [0000-0002-9828-9871]; Zhang, C. [0000-0003-2092-9135]
The second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2) took place in Cabauw (the Netherlands) in September 2016 with the aim of assessing the consistency of multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of tropospheric species (NO2, HCHO, O3, HONO, CHOCHO and O4). This was achieved through the coordinated operation of 36 spectrometers operated by 24 groups from all over the world, together with a wide range of supporting reference observations (in situ analysers, balloon sondes, lidars, long-path DOAS, direct-sun DOAS, Sun photometer and meteorological instruments).
In the presented study, the retrieved CINDI-2 MAX-DOAS trace gas (NO2, HCHO) and aerosol vertical profiles of 15 participating groups using different inversion algorithms are compared and validated against the colocated supporting observations, with the focus on aerosol optical thicknesses (AOTs), trace gas vertical column densities (VCDs) and trace gas surface concentrations. The algorithms are based on three different techniques: six use the optimal estimation method, two use a parameterized approach and one algorithm relies on simplified radiative transport assumptions and analytical calculations. To assess the agreement among the inversion algorithms independent of inconsistencies in the trace gas slant column density acquisition, participants applied their inversion to a common set of slant columns. Further, important settings like the retrieval grid, profiles of O3, temperature and pressure as well as aerosol optical properties and a priori assumptions (for optimal estimation algorithms) have been prescribed to reduce possible sources of discrepancies.
The profiling results were found to be in good qualitative agreement: most participants obtained the same features in the retrieved vertical trace gas and aerosol distributions; however, these are sometimes at different altitudes and of different magnitudes. Under clear-sky conditions, the root-mean-square differences (RMSDs) among the results of individual participants are in the range of 0.01–0.1 for AOTs, (1.5–15) ×1014molec.cm−2 for trace gas (NO2, HCHO) VCDs and (0.3–8)×1010molec.cm−3 for trace gas surface concentrations. These values compare to approximate average optical thicknesses of 0.3, trace gas vertical columns of 90×1014molec.cm−2 and trace gas surface concentrations of 11×1010molec.cm−3 observed over the campaign period. The discrepancies originate from differences in the applied techniques, the exact implementation of the algorithms and the user-defined settings that were not prescribed.
For the comparison against supporting observations, the RMSDs increase to a range of 0.02–0.2 against AOTs from the Sun photometer, (11–55)×1014molec.cm−2 against trace gas VCDs from direct-sun DOAS observations and (0.8–9)×1010molec.cm−3 against surface concentrations from the long-path DOAS instrument. This increase in RMSDs is most likely caused by uncertainties in the supporting data, spatiotemporal mismatch among the observations and simplified assumptions particularly on aerosol optical properties made for the MAX-DOAS retrieval.
As a side investigation, the comparison was repeated with the participants retrieving profiles from their own differential slant column densities (dSCDs) acquired during the campaign. In this case, the consistency among the participants degrades by about 30 % for AOTs, by 180 % (40 %) for HCHO (NO2) VCDs and by 90 % (20 %) for HCHO (NO2) surface concentrations.
In former publications and also during this comparison study, it was found that MAX-DOAS vertically integrated aerosol extinction coefficient profiles systematically underestimate the AOT observed by the Sun photometer. For the first time, it is quantitatively shown that for optimal estimation algorithms this can be largely explained and compensated by considering biases arising from the reduced sensitivity of MAX-DOAS observations to higher altitudes and associated a priori assumptions.
Cirrus-induced shortwave radiative effects depending on their optical and physical properties: Case studies using simulations and measurements
(Elsevier BV, 2020-12-01) Córdoba Jabonero, C.; Gómez Martín, L.; Del Águila, A.; Vilaplana, J. M.; López Cayuela, M. A.; Zorzano, María Paz; Agencia Estatal de Investigación (AEI); European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); 000-0002-6655-7659; 0000-0002-4492-9650; 0000-0002-8825-830X; 0000-0003-4859-471X; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Cirrus (Ci) clouds play an important role in the atmospheric radiative balance, and hence in Climate Change. In this work, a polarized Micro-Pulse Lidar (P-MPL), standard NASA/Micro Pulse NETwork (MPLNET) system, deployed at the INTA/El Arenosillo station in Huelva (SW Iberian Peninsula) is used for Ci detection and characterization for the first time at this site. Three days were selected on the basis of the predominantly detected Ci clouds in dependence on their cloud optical depth (COD). Hence, three Ci cloud categories were examined at day-times for comparison with solar radiation issues: 19 cases of sub-visuals (svCi, COD: 0.01-0.03) on 1 October 2016, 7 cases of semitransparents (stCi, COD: 0.03-0.30) on 8 May 2017, and 17 cases of opaques (opCi, COD: 0.3-3.0) on 28 October 2016. Their radiative-relevant optical, macro- and micro-physical properties were retrieved. The mean COD for the svCi, stCi and opCi groups was 0.02 +/- 0.01, 0.22 +/- 0.08 and 0.93 +/- 0.40, respectively; in overall, their lidar ratio ranged between 25 and 35 sr. Ci clouds were detected at 11-13 km height (top boundaries) with geometrical thicknesses of 1.7-2.0 km. Temperatures reported at those altitudes corresponded to lower values than the thermal threshold for homogenous ice formation. Volume linear depolarization ratios of 0.3-0.4 (and normalized backscattering ratios higher than 0.9) also confirmed Ci clouds purely composed of ice particles. Their effective radius was within the interval of 9-15 mu m size, and the ice water path ranged from 0.02 (svCi) to 9.9 (opCi) g m(-2). The Cirrus Cloud Radiative Effect (CCRE) was estimated using a Radiative Transfer (RT) model for Ci-free conditions and Ci-mode (Ci presence) scenarios. RT simulations were performed for deriving the CCRE at the top-of-atmosphere (TOA) and on surface (SRF), and also the atmospheric CCRE, for the overall shortwave (SW) range and their spectral sub-intervals (UV, VIS and NIR). A good agreement was first obtained for the RT simulations as validated against solar radiation measurements under clean conditions for solar zenith angles less than 75 degrees (differences were mainly within +/- 20 W m(-2) and correlation coefficients close to 1). By considering all the Ci clouds, independently on their COD, the mean SW CCRE values at TOA and SRF were, respectively, -30 +/- 26 and -24 +/- 19 W m(-2), being the mean atmospheric CCRE of -7 +/- 7 W m(-2); these values are in good agreement with global annual estimates found for Ci clouds. By using linear regression analysis, a Ci-induced enhancing cooling radiative effect was observed as COD increased for all the spectral ranges, with high correlations. In particular, the SW CCRE at TOA and SRF, and the atmospheric CCRE, presented COD-dependent rates of -74 +/- 4, -55 +/- 5, -19 +/- 2 W m(-2) tau(-1), respectively. Additionally, increasing negative rates are found from UV to NIR for each Ci category, reflecting a higher cooling NIR contribution w.r.t. UV and VIS ranges to the SW CCRE, and being also more pronounced at the TOA w.r.t. on SRF, as expected. The contribution of the SW CCRE to the net (SW + LW) radiative balance can be also potentially relevant. These results are especially significant for space-borne photometric/radiometric instrumentation and can contribute to validation purposes of the next ESA's EarthCARE mission, whose principal scientific goal is focused on radiation-aerosol-cloud interaction research.
