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Retrieval of Daytime Total Column Water Vapour from OLCI Measurements over Land Surfaces. REMOTE SENSING 2021. [DOI: 10.3390/rs13050932] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A new retrieval of total column water vapour (TCWV) from daytime measurements over land of the Ocean and Land Colour Instrument (OLCI) on-board the Copernicus Sentinel-3 missions is presented. The Copernicus Sentinel-3 OLCI Water Vapour product (COWa) retrieval algorithm is based on the differential absorption technique, relating TCWV to the radiance ratio of non-absorbing band and nearby water vapour absorbing band and was previously also successfully applied to other passive imagers Medium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS). One of the main advantages of the OLCI instrument regarding improved TCWV retrievals lies in the use of more than one absorbing band. Furthermore, the COWa retrieval algorithm is based on the full Optimal Estimation (OE) method, providing pixel-based uncertainty estimates, and transferable to other Near-Infrared (NIR) based TCWV observations. Three independent global TCWV data sets, i.e., Aerosol Robotic Network (AERONET), Atmospheric Radiation Measurement (ARM) and U.S. SuomiNet, and a German Global Navigation Satellite System (GNSS) TCWV data set, all obtained from ground-based observations, serve as reference data sets for the validation. Comparisons show an overall good agreement, with absolute biases between 0.07 and 1.31 kg/m2 and root mean square errors (RMSE) between 1.35 and 3.26 kg/m2. This is a clear improvement in comparison to the operational OLCI TCWV Level 2 product, for which the bias and RMSEs range between 1.10 and 2.55 kg/m2 and 2.08 and 3.70 kg/m2, respectively. A first evaluation of pixel-based uncertainties indicates good estimated uncertainties for lower retrieval errors, while the uncertainties seem to be overestimated for higher retrieval errors.
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Water Vapor Retrievals from Spectral Direct Irradiance Measured with an EKO MS-711 Spectroradiometer—Intercomparison with Other Techniques. REMOTE SENSING 2021. [DOI: 10.3390/rs13030350] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Precipitable water vapor retrievals are of major importance for assessing and understanding atmospheric radiative balance and solar radiation resources. On that basis, this study presents the first PWV values measured with a novel EKO MS-711 grating spectroradiometer from direct normal irradiance in the spectral range between 930 and 960 nm at the Izaña Observatory (IZO, Spain) between April and December 2019. The expanded uncertainty of PWV (UPWV) was theoretically evaluated using the Monte-Carlo method, obtaining an averaged value of 0.37 ± 0.11 mm. The estimated uncertainty presents a clear dependence on PWV. For PWV ≤ 5 mm (62% of the data), the mean UPWV is 0.31 ± 0.07 mm, while for PWV > 5 mm (38% of the data) is 0.47 ± 0.08 mm. In addition, the EKO PWV retrievals were comprehensively compared against the PWV measurements from several reference techniques available at IZO, including meteorological radiosondes, Global Navigation Satellite System (GNSS), CIMEL-AERONET sun photometer and Fourier Transform Infrared spectrometry (FTIR). The EKO PWV values closely align with the above mentioned different techniques, providing a mean bias and standard deviation of −0.30 ± 0.89 mm, 0.02 ± 0.68 mm, −0.57 ± 0.68 mm, and 0.33 ± 0.59 mm, with respect to the RS92, GNSS, FTIR and CIMEL-AERONET, respectively. According to the theoretical analysis, MB decreases when comparing values for PWV > 5 mm, leading to a PWV MB between −0.45 mm (EKO vs. FTIR), and 0.11 mm (EKO vs. CIMEL-AERONET). These results confirm that the EKO MS-711 spectroradiometer is precise enough to provide reliable PWV data on a routine basis and, as a result, can complement existing ground-based PWV observations. The implementation of PWV measurements in a spectroradiometer increases the capabilities of these types of instruments to simultaneously obtain key parameters used in certain applications such as monitoring solar power plants performance.
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Column Integrated Water Vapor and Aerosol Load Characterization with the New ZEN-R52 Radiometer. REMOTE SENSING 2020. [DOI: 10.3390/rs12091424] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The study shows the first results of the column-integrated water vapor retrieved by the new ZEN-R52 radiometer. This new radiometer has been specifically designed to monitor aerosols and atmospheric water vapor with a high degree of autonomy and robustness in order to allow the expansion of the observations of these parameters to remote desert areas from ground-based platforms. The ZEN-R52 device shows substantial improvements compared to the previous ZEN-R41 prototype: a smaller field of view, an increased signal-to-noise ratio, better stray light rejection, and an additional channel (940 nm) for precipitable water vapor (PWV) retrieval. PWV is inferred from the ZEN-R52 Zenith Sky Radiance (ZSR) measurements using a lookup table (LUT) methodology. The improvement of the new ZEN-R52 in terms of ZSR was verified by means of a comparison with the ZEN-R41, and with the Aerosol Robotic Network (AERONET) Cimel CE318 (CE318-AERONET) at Izaña Observatory, a Global Atmosphere Watch (GAW) high mountain station (Tenerife, Canary Islands, Spain), over a 10-month period (August 2017 to June 2018). ZEN-R52 aerosol optical depth (AOD) was extracted by means of the ZEN–AOD–LUT method with an uncertainty of ±0.01 ± 0.13*AOD. ZEN-R52 PWV extracted using a new LUT technique was compared with quasi-simultaneous (±30 s) Fourier Transform Infrared (FTIR) spectrometer measurements as reference. A good agreement was found between the two instruments (PWV means a relative difference of 9.1% and an uncertainty of ±0.089 cm or ±0.036 + 0.061*PWV for PWV <1 cm). This comparison analysis was extended using two PWV datasets from the same CE318 reference instrument at Izaña Observatory: one obtained from AERONET (CE318-AERONET), and another one using a specific calibration of the 940-nm channel performed in this work at Izaña Atmospheric Research Center Observatory (CE318-IARC), which improves the PWV product.
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Liu YK, Li CR, Ma LL, Qian YG, Wang N, Gao CX, Tang LL. Land surface reflectance retrieval from optical hyperspectral data collected with an unmanned aerial vehicle platform. OPTICS EXPRESS 2019; 27:7174-7195. [PMID: 30876287 DOI: 10.1364/oe.27.007174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 01/12/2019] [Indexed: 06/09/2023]
Abstract
We present a physical-based atmospheric correction algorithm for land surface reflectance retrieval based on radiative transfer model MODTRAN 5, with which the aerosol optical thickness @550 nm (AOT@550nm), columnar water vapor (CWV) could also be estimated from the hyperspectral data collected over UAV platform. Then, the method was tested on both the synthetic and field campaign-collected hyperspectral data by an UAV-VNIRIS (UAV visible/near-infrared imaging hyperspectrometer) with the spectral range covering from 400 to 1000 nm. The retrieval results were validated with theoretical values from synthetic data and truth values from field campaign measurements. The results show that the averaged MAE (mean absolute error) and RMSE (root mean squared error) of measured and retrieved surface reflectance based on estimated AOT@550nm and CWV is 0.0134 and 0.0130. Meanwhile, the averaged MAE and RMSE of measured and retrieved surface reflectance based on ground measured AOT@550nm and CWV is 0.0101 and 0.0112. The results show that our introduced method has good agreement with the method based on ground-measured AOT@550nm and CWV. These encouraging results also indicate that the introduced physical-based atmospheric approach provides a quick and reliable way to acquire the land surface reflectance from UAV platform-observed hyperspectral data for further quantitative remote sensing applications.
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Falaiye OA, Abimbola OJ, Pinker RT, Pérez-Ramírez D, Willoughby AA. Multi-technique analysis of precipitable water vapor estimates in the sub-Sahel West Africa. Heliyon 2018; 4:e00765. [PMID: 30197932 PMCID: PMC6127880 DOI: 10.1016/j.heliyon.2018.e00765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/04/2018] [Accepted: 08/28/2018] [Indexed: 10/29/2022] Open
Abstract
Precipitable water vapor (PWV) is an important climate parameter indicative of available moisture in the atmosphere; it is also an important greenhouse gas. Observations of precipitable water vapor in sub-Sahel West Africa are almost non-existent. Several Aerosol Robotic Network (AERONET) sites have been established across West Africa, and observations from four of them, namely, Ilorin (4.34° E, 8.32° N), Cinzana (5.93° W, 13.28° N), Banizoumbou (2.67° E, 13.54° N) and Dakar (16.96° W, 14.39° N) are being used in this study. Data spanning the period from 2004 to 2014 have been selected; they include conventional humidity parameters, remotely sensed aerosol and precipitable water information and numerical model outputs. Since in Africa, only conventional information on humidity parameters is available, it is important to utilize the unique observations from the AERONET network to calibrate empirical formulas frequently used to estimate precipitable water vapor from humidity measurements. An empirical formula of the form PWV=aTd+b where Td is the surface dew point temperature, a and b are constants, was fitted to the data and is proposed as applicable to the climatic condition of the sub-Sahel. Moreover, we have also used the AERONET information to evaluate the capabilities of well-established numerical weather prediction (NWP) models such as ERA Interim Reanalysis, NCEP-DOE Reanalysis II and NCEP-CFSR, to estimate precipitable water vapor in the sub-Sahel West Africa; it was found that the models tend to overestimate the amount of precipitable water at the selected sites by about 25 %.
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Affiliation(s)
| | | | - Rachel T Pinker
- Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA
| | - Daniel Pérez-Ramírez
- Mesoscale Atmospheric Processes Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.,Goddard Earth Sciences Technology and Research, Universities Space Research Association (GESTAR/USRA), Columbia, MD, USA
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Improved Aerosol Optical Thickness, Columnar Water Vapor, and Surface Reflectance Retrieval from Combined CASI and SASI Airborne Hyperspectral Sensors. REMOTE SENSING 2017. [DOI: 10.3390/rs9030217] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Obregón MA, Costa MJ, Serrano A, Silva AM. Effect of water vapor in the SW and LW downward irradiance at the surface during a day with low aerosol load. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/1755-1315/28/1/012009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Muyimbwa D, Frette Ø, Stamnes JJ, Ssenyonga T, Chen YC, Hamre B. Aerosol optical properties and precipitable water vapor column in the atmosphere of Norway. APPLIED OPTICS 2015; 54:1505-1514. [PMID: 25968219 DOI: 10.1364/ao.54.001505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 01/19/2015] [Indexed: 06/04/2023]
Abstract
Between February 2012 and April 2014, we measured and analyzed direct solar radiances at a ground-based station in Bergen, Norway. We discovered that the spectral aerosol optical thickness (AOT) and precipitable water vapor column (PWVC) retrieved from these measurements have a seasonal variation with highest values in summer and lowest values in winter. The highest value of the monthly median AOT at 440 nm of about 0.16 was measured in July and the lowest of about 0.04 was measured in December. The highest value of the monthly median PWVC of about 2.0 cm was measured in July and the lowest of about 0.4 cm was measured in December. We derived Ångström exponents that were used to deduce aerosol particle size distributions. We found that coarse-mode aerosol particles dominated most of the time during the measurement period, but fine-mode aerosol particles dominated during the winter seasons. The derived Ångström exponent values suggested that aerosols containing sea salt could have been dominating at this station during the measurement period.
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Duan SB, Li ZL, Tang BH, Wu H, Ma L, Zhao E, Li C. Land surface reflectance retrieval from hyperspectral data collected by an unmanned aerial vehicle over the Baotou test site. PLoS One 2013; 8:e66972. [PMID: 23785513 PMCID: PMC3680449 DOI: 10.1371/journal.pone.0066972] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 05/13/2013] [Indexed: 11/19/2022] Open
Abstract
To evaluate the in-flight performance of a new hyperspectral sensor onboard an unmanned aerial vehicle (UAV-HYPER), a comprehensive field campaign was conducted over the Baotou test site in China on 3 September 2011. Several portable reference reflectance targets were deployed across the test site. The radiometric performance of the UAV-HYPER sensor was assessed in terms of signal-to-noise ratio (SNR) and the calibration accuracy. The SNR of the different bands of the UAV-HYPER sensor was estimated to be between approximately 5 and 120 over the homogeneous targets, and the linear response of the apparent reflectance ranged from approximately 0.05 to 0.45. The uniform and non-uniform Lambertian land surface reflectance was retrieved and validated using in situ measurements, with root mean square error (RMSE) of approximately 0.01-0.07 and relative RMSE of approximately 5%-12%. There were small discrepancies between the retrieved uniform and non-uniform Lambertian land surface reflectance over the homogeneous targets and under low aerosol optical depth (AOD) conditions (AOD = 0.18). However, these discrepancies must be taken into account when adjacent pixels had large land surface reflectance contrast and under high AOD conditions (e.g. AOD = 1.0).
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Affiliation(s)
- Si-Bo Duan
- State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- Laboratoire des sciences de l'ingenieur, de l'informatique et de l'imagerie, Université de Strasbourg, Centre National de la Recherche Scientifique, Illkirch, France
| | - Zhao-Liang Li
- Laboratoire des sciences de l'ingenieur, de l'informatique et de l'imagerie, Université de Strasbourg, Centre National de la Recherche Scientifique, Illkirch, France
- Key Laboratory of Agri-informatics,Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China
- * E-mail:
| | - Bo-Hui Tang
- State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Hua Wu
- State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Lingling Ma
- Earth Observation Technology Application Department, Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing, China
| | - Enyu Zhao
- University of Chinese Academy of Sciences, Beijing, China
- Earth Observation Technology Application Department, Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing, China
| | - Chuanrong Li
- Earth Observation Technology Application Department, Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing, China
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Pérez-Ramírez D, Navas-Guzmán F, Lyamani H, Fernández-Gálvez J, Olmo FJ, Alados-Arboledas L. Retrievals of precipitable water vapor using star photometry: Assessment with Raman lidar and link to sun photometry. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011jd016450] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Torres B, Cachorro VE, Toledano C, Ortiz de Galisteo JP, Berjón A, de Frutos AM, Bennouna Y, Laulainen N. Precipitable water vapor characterization in the Gulf of Cadiz region (southwestern Spain) based on Sun photometer, GPS, and radiosonde data. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jd012724] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Alexandrov MD, Schmid B, Turner DD, Cairns B, Oinas V, Lacis AA, Gutman SI, Westwater ER, Smirnov A, Eilers J. Columnar water vapor retrievals from multifilter rotating shadowband radiometer data. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jd010543] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hansell RA, Liou KN, Ou SC, Tsay SC, Ji Q, Reid JS. Remote sensing of mineral dust aerosol using AERI during the UAE2: A modeling and sensitivity study. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008jd010246] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Livingston J, Schmid B, Redemann J, Russell PB, Ramirez SA, Eilers J, Gore W, Howard S, Pommier J, Fetzer EJ, Seemann SW, Borbas E, Wolfe DE, Thompson AM. Comparison of water vapor measurements by airborne Sun photometer and near-coincident in situ and satellite sensors during INTEX/ITCT 2004. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd007733] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Estellés V, Martínez-Lozano JA, Utrillas MP, Campanelli M. Columnar aerosol properties in Valencia (Spain) by ground-based Sun photometry. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd008167] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ernest Raj P, Devara PCS, Maheskumar RS, Pandithurai G, Dani KK, Saha SK, Sonbawne SM, Tiwari YK. Results of Sun Photometer–Derived Precipitable Water Content over a Tropical Indian Station. ACTA ACUST UNITED AC 2004. [DOI: 10.1175/jam2149.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
A compact, hand-held multiband sun photometer (ozone monitor) has been used to measure total precipitable water content (PWC) at the low-latitude tropical station in Pune, India (18°32′N, 73°51′E). Data collected in the daytime (0730–1800 LT) during the period from May 1998 to September 2001 have been used here. The daytime average PWC value at this station is 1.13 cm, and the average for only the clear-sky days is 0.75 cm. PWC values between 0.75 and 1.0 cm have the maximum frequency of occurrence. There is a large day-to-day variability due to varied sky and meteorological conditions. Mainly two types of diurnal variations in PWC are observed. The one occurs in the premonsoon summer months of April and May and shows that forenoon values are smaller than afternoon values. The other type occurs in November and December and shows a minimum around noontime. There is a diurnal asymmetry in PWC in which, on the majority of the days, the mean afternoon value is greater than the forenoon value. This asymmetry is more pronounced in the summer and southwest monsoon months (i.e., March–June). Monthly mean PWC is highest in September and lowest in December. The increase in PWC from the winter (December–February) to summer (March–May) seasons is about 50% and from the summer to southwest monsoon seasons (June–September) is almost 98%. Sun photometer–derived PWC shows a fairly good relationship with surface relative humidity and radiosonde-derived PWC, with a correlation coefficient as high as 0.80.
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Affiliation(s)
- P. Ernest Raj
- Indian Institute of Tropical Meteorology, Pune, India
| | | | | | | | - K. K. Dani
- Indian Institute of Tropical Meteorology, Pune, India
| | - S. K. Saha
- Indian Institute of Tropical Meteorology, Pune, India
| | | | - Y. K. Tiwari
- Indian Institute of Tropical Meteorology, Pune, India
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De Tomasi F, Perrone MR. Lidar measurements of tropospheric water vapor and aerosol profiles over southeastern Italy. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jd002781] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- F. De Tomasi
- Dipartimento di Fisica; Istituto Nazionale di Fisica della Materia; Lecce Italy
| | - M. R. Perrone
- Dipartimento di Fisica; Istituto Nazionale di Fisica della Materia; Lecce Italy
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Pandithurai G, Pinker RT, Dubovik O, Holben BN, Aro TO. Remote sensing of aerosol optical characteristics in sub-Sahel, West Africa. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001jd900234] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Eck TF, Holben BN, Dubovik O, Smirnov A, Slutsker I, Lobert JM, Ramanathan V. Column-integrated aerosol optical properties over the Maldives during the northeast monsoon for 1998-2000. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001jd000786] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pinker RT, Pandithurai G, Holben BN, Dubovik O, Aro TO. A dust outbreak episode in sub-Sahel West Africa. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001jd900118] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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21
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Holben BN, Tanré D, Smirnov A, Eck TF, Slutsker I, Abuhassan N, Newcomb WW, Schafer JS, Chatenet B, Lavenu F, Kaufman YJ, Castle JV, Setzer A, Markham B, Clark D, Frouin R, Halthore R, Karneli A, O'Neill NT, Pietras C, Pinker RT, Voss K, Zibordi G. An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001jd900014] [Citation(s) in RCA: 1499] [Impact Index Per Article: 65.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Ingold T, Schmid B, Mätzler C, Demoulin P, Kämpfer N. Modeled and empirical approaches for retrieving columnar water vapor from solar transmittance measurements in the 0.72, 0.82, and 0.94 μm absorption bands. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/2000jd900392] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Watson IM, Oppenheimer C. Particle size distributions of Mount Etna's aerosol plume constrained by Sun photometry. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/2000jd900042] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Yamasoe MA, Kaufman YJ, Dubovik O, Remer LA, Holben BN, Artaxo P. Retrieval of the real part of the refractive index of smoke particles from Sun/sky measurements during SCAR-B. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98jd01211] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Cachorro VE, Utrillas P, Vergaz R, Durán P, de Frutos AM, Martinez-Lozano JA. Determination of the Atmospheric-Water-Vapor Content in the 940-nm Absorption Band by Use of Moderate Spectral-Resolution Measurements of Direct Solar Irradiance. APPLIED OPTICS 1998; 37:4678-4689. [PMID: 18285925 DOI: 10.1364/ao.37.004678] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We have analyzed three methods that can be used to determine the integrated water vapor of the atmosphere in the 940-nm band by means of modeled and measured direct solar spectral irradiance. The experimental irradiance data were obtained with a commercial LI-COR 1800 spectroradiometer, based on a monochromator system, of high to moderate spectral resolution (6 nm) in the 300-1100-nm range. The modeled data are based on monochromatic approaches to determine atmospheric transmittance constituents; for those of water vapor we used the lowtran7 model. The first method is a curve-fitting procedure that makes use of the entire shape band absorption information to retrieve a unique water-vapor value. The second method makes use of the monochromatic approach of the absorption transmittance formula to determine the amount of water vapor at each wavelength of the absorption band, and the third method is the classic differential absorption technique suitably applied to our data. Spectral analysis showed the advantages and disadvantages of each method, such as problems linked to the various spectral resolutions of the experimental and the modeled data, the width of the spectral range used to define the water-vapor absorption band, and the dependence of the retrieval on the choice of the two selected wavelengths in the last-named technique. All these problems were considered so they could be avoided or minimized and the associated errors estimated. We used the methods to determine water-vapor values for the period from March to November 1995 at a rural station in Vallodolid, Spain, allowing for the evaluation of the differences in real monitoring conditions. Finally, the contribution of continuum absorption was also evaluated, yielding lower water-vapor values between 13 and 30%. These differences were considerably greater than those that were due to the problems that we have just enumerated.
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Markham BL, Schafer JS, Holben BN, Halthore RN. Atmospheric aerosol and water vapor characteristics over north central Canada during BOREAS. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97jd00241] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Halthore RN, Eck TF, Holben BN, Markham BL. Sun photometric measurements of atmospheric water vapor column abundance in the 940-nm band. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/96jd03247] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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28
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Schmid B, Thorne KJ, Demoulin P, Peter R, Mätzler C, Sekler J. Comparison of modeled and empirical approaches for retrieving columnar water vapor from solar transmittance measurements in the 0.94-μm region. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96jd00337] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Schmid B, Wehrli C. Comparison of Sun photometer calibration by use of the Langley technique and the standard lamp. APPLIED OPTICS 1995; 34:4500-4512. [PMID: 21052283 DOI: 10.1364/ao.34.004500] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Asix-channel Sun photometer has been calibrated by means of two different methods: Langley plots and standard irradiance lamps. A 4-month calibration campaign was carried out at a high mountain site, Jungfraujoch (3580 m above sea level), in the Swiss Alps. Calibration constants V(0)(λ) determined on clear and stable days by means of a refined Langley-plot technique scatter by less than 0.25% (rms) for wavelengths outside of strong gaseous absorption bands. Inside the 0.94-µm water-vapor absorption band, the V(0)(λ) values retrieved by means of modified Langley plots scatter by 1.0% (rms). Repeated calibrations of the Sun photometer by means of irradiance standard lamps were performed at the World Radiation Center in Davos. The comparison of both methods ranges from perfect agreement to a deviation of 4.9% for the different channels. A discussion of the errors introduced by both methods shows that the Langley-plot calibration, when performed under very clear atmospheric conditions, is superior. However, by means of the standard-lamp calibrations a temporal degradation of the instrument's response up to 4.6% per year was found, implying that a single calibration campaign as done here is not sufficient. Thus we recommend the use of a combination of both methods for maintaining an accurate calibration.
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Kalluri SNV, Dubayah RO. Comparison of atmospheric correction models for thermal bands of the advanced very high resolution radiometer over FIFE. ACTA ACUST UNITED AC 1995. [DOI: 10.1029/95jd02043] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ba MB, Deschamps PY, Frouin R. Error reduction in NOAA satellite monitoring of the land surface vegetation during FIFE. ACTA ACUST UNITED AC 1995. [DOI: 10.1029/95jd01645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Michalsky JJ, Liljegren JC, Harrison LC. A comparison of Sun photometer derivations of total column water vapor and ozone to standard measures of same at the Southern Great Plains Atmospheric Radiation Measurement site. ACTA ACUST UNITED AC 1995. [DOI: 10.1029/95jd02706] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Markham BL, Halthore RN, Goetz SJ. Surface reflectance retrieval from satellite and aircraft sensors: Results of sensor and algorithm comparisons during FIFE. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92jd02077] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Halthore RN, Markham BL. Overview of atmospheric correction and radiometric calibration efforts during FIFE. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92jd02076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bruegge CJ, Halthore RN, Markham B, Spanner M, Wrlgley R. Aerosol optical depth retrievals over the Konza Prairie. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92jd01303] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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