The Polar Multi-Sensor Aerosol product (PMAp) is based on the synergistic use of three instruments from the Metop platform, GOME-2, AVHRR, and IASI. The retrieval algorithm includes three major ...steps: a pre-identification of the aerosol class, a selection of the aerosol model, and a calculation of the Aerosol Optical Depth (AOD). This paper provides a detailed description of the PMAp retrieval, which combines information provided by the three instruments. The retrieved AOD is qualitatively evaluated, and a good temporal as well as spatial performance is observed, including for the transition between ocean and land. More quantitatively, the performance is evaluated by comparison to AERONET in situ measurements. Very good consistency is also observed when compared to other space-based data such as MODIS or VIIRS. The paper demonstrates the ability of this first generation of synergistic products to derive reliable AOD, opening the door for the development of synergistic products from the instruments to be embarked on the coming Metop Second Generation platform. PMAp has been operationally distributed in near-real-time since 2014 over ocean, and 2016 over land.
The EUMETSAT Polar System Klaes, K. Dieter; Ackermann, Jörg; Anderson, Craig ...
Bulletin of the American Meteorological Society,
06/2021, Letnik:
102, Številka:
6
Journal Article
Recenzirano
Odprti dostop
After successful launch in November 2018 and successful commissioning of Metop-C, all three satellites of the EUMETSAT Polar System (EPS) are in orbit together and operational. EPS is part of the ...Initial Joint Polar System (IJPS) with the United States (NOAA) and provides the service in the midmorning orbit. The Metop satellites carry a mission payload of sounding and imaging instruments, which allow provision of support to operational meteorology and climate monitoring, which are the main mission objectives for EPS. Applications include numerical weather prediction, atmospheric composition monitoring, and marine meteorology. Climate monitoring is supported through the generation of long time series through the program duration of 20+ years. The payload was developed and contributed by partners, including NOAA, CNES, and ESA. EUMETSAT and ESA developed the space segment in cooperation. The system has proven its value since the first satellite Metop-A, with enhanced products at high reliability for atmospheric sounding, delivered a very strong positive impact on NWP and results beyond expectations for atmospheric composition and chemistry applications. Having multiple satellites in orbit—now three—has enabled enhanced and additional products with increased impact, like atmospheric motion vector products at latitudes not accessible to geostationary observations or increased probability of radio occultations and hence atmospheric soundings with the Global Navigation Satellite System (GNSS) Radio-Occultation Atmospheric Sounder (GRAS) instruments. The paper gives an overview of the system and the embarked payload and discusses the benefits of generated products for applications and services. The conclusions point to the follow-on system, currently under development and assuring continuity for another 20+ years.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Solar-induced fluorescence (SIF) data from satellites are increasingly used as a proxy for photosynthetic activity by vegetation, and as a constraint on gross primary production. Here we report on ...improvements in the algorithm to retrieve mid-morning (09:30 hrs local time) SIF estimates on the global scale from GOME-2 sensor on the Metop-A satellite (GOME-2A) for the period 2007-2019. Our new SIFTER (Sun-Induced Fluorescence of Terrestrial Ecosystems Retrieval) v2 algorithm improves over a previous version by using a narrower spectral window that avoids strong oxygen absorption and is less sensitive to water vapour absorption, by constructing stable reference spectra from a 6-year period (2007-2012) of atmospheric spectra over the Sahara, and by applying a latitude-dependent zero-level adjustment that accounts for biases in the data product. We generated stable, good-quality SIF retrievals between January 2007 and June 2013, when GOME-2A degradation in the near infrared was still limited. After the narrowing of the GOME-2A swath in July 2013, we characterized the throughput degradation of the level-1 data in order to derive reflectance corrections and apply these for the SIF retrievals between July 2013 and December 2018. SIFTER v2 data compares well with the independent NASA v2.8 data product. Especially in the evergreen tropics, SIFTER v2 no longer shows the underestimates against other satellite products that were seen in SIFTER v1. The new data product includes uncertainty estimates for individual observations, and is best used for mostly clear-sky scenes, and when spectral residuals remain below a certain spectral autocorrelation threshold. Our results support the use of SIFTER v2 data to be used as an independent constraint on photosynthetic activity on regional to global scales.
Growing attention has been paid over recent years to the possibility of monitoring surface particulate matter (PM) concentrations through the use of satellite observations. Satellite remote sensing ...of both aerosol and trace gas constituents can be usefully employed in air quality monitoring (AQ). The MODIS (Terra-Aqua/NASA platforms) aerosol optical properties were used here in a semi-empirical approach to estimate PM 2.5 content at ground level. PM 2.5 samplings were employed to convert aerosol optical depth AOD into PM estimates, considering meteorological fields simulated by MM5. Thus, daily maps of satellite-based PM 2.5 concentrations over Northern Italy were derived. Comparison with daily PM 2.5 , sampled on the ground during the QUITSAT project over six validation sites of the Po valley, showed good agreement (R 2 ¿ 0.68 and R 2 ¿ 0.59 for MODIS/Terra and MODIS/Aqua, respectively), with the satellite-based concentrations tending to underestimate the values by at most ~20%. Monthly averaged values were also compared providing good agreement, with R 2 ¿ 0.7 for each platform.
A set of 1330 radiosoundings was performed at the Italian station of Terra Nova Bay in Antarctica during 12 measurement campaigns from 1987 to 1998. These measurements were separately analyzed for ...the various 10-day periods from mid-October to mid-February, to determine the mean vertical profiles of air pressure and temperature in the troposphere and lower stratosphere, and those of moisture parameters in the troposphere. The temperature data were corrected for the errors due to radiation and heat exchange processes and for the lag errors of the sensor. Due to temperature dependence and other dry bias effects, the humidity errors were also taken into account. The tropospheric temperature was found to present average values of its vertical gradient varying between −5.4 and −6.3 K/km, while its minimum height associated with the tropopause gradually lowered from 13.7 to 7.9 km. Total water vapor content increased correspondingly from 0.12 to 0.36 g cm
−2 during the first two months and decreased to 0.26 g cm
−2 in the following period. Stratospheric temperature was observed to increase during the first 2 months by about 15 K in the region below the 24-km height and to appreciably decrease at upper levels, maintaining almost stable features during the subsequent months.
Simultaneous measurements of downwelling short-wave solar irradiance and incoming total radiation flux were performed at the Reeves Nevè glacier station (1200 m MSL) in Antarctica on 41 days from ...late November 1994 to early January 1995, employing the upward sensors of an albedometer and a pyrradiometer. The downwelling short-wave radiation measurements were analysed following the Duchon and O'Malley J. Appl. Meteorol. 38 (1999) 132 procedure for classifying clouds, using the 50-min running mean values of standard deviation and the ratio of scaled observed to scaled clear-sky irradiance. Comparing these measurements with the Duchon and O'Malley rectangular boundaries and the local human observations of clouds collected on 17 days of the campaign, we found that the Duchon and O'Malley classification method obtained a success rate of 93% for cirrus and only 25% for cumulus. New decision criteria were established for some polar cloud classes providing success rates of 94% for cirrus, 67% for cirrostratus and altostratus, and 33% for cumulus and altocumulus.
The ratios of the downwelling short-wave irradiance measured for cloudy-sky conditions to that calculated for clear-sky conditions were analysed in terms of the Kasten and Czeplak Sol. Energy 24 (1980) 177 formula together with simultaneous human observations of cloudiness, to determine the empirical relationship curves providing reliable estimates of cloudiness for each of the three above-mentioned cloud classes. Using these cloudiness estimates, the downwelling long-wave radiation measurements (obtained as differences between the downward fluxes of total and short-wave radiation) were examined to evaluate the downwelling long-wave radiation flux normalised to totally overcast sky conditions. Calculations of the long-wave radiation flux were performed with the MODTRAN 3.7 code Kneizys, F.X., Abreu, L.W., Anderson, G.P., Chetwynd, J.H., Shettle, E.P., Berk, A., Bernstein, L.S., Robertson, D.C., Acharya, P., Rothman, L.S., Selby, J.E.A., Gallery, W.O., Clough, S.A., 1996. In: Abreu, L.W., Anderson, G.P. (Eds.), The MODTRAN 2/3 Report and LOWTRAN 7 MODEL. Contract F19628-91-C.0132, Phillips Laboratory, Geophysics Directorate, PL/GPOS, Hanscom AFB, MA, 261 pp. for both clear-sky and cloudy-sky conditions, considering various cloud types characterised by different cloud base altitudes and vertical thicknesses. From these evaluations, best-fit curves of the downwelling long-wave radiation flux were defined as a function of the cloud base height for the three polar cloud classes. Using these relationship curves, average estimates of the cloud base height were obtained from the three corresponding sub-sets of long-wave radiation measurements. The relative frequency histograms of the cloud base height defined by examining these three sub-sets were found to present median values of 4.7, 1.7 and 3.6 km for cirrus, cirrostratus/altostratus and cumulus/altocumulus, respectively, while median values of 6.5, 1.8 and 2.9 km were correspondingly determined by analysing only the measurements taken together with simultaneous cloud observations.
Spectral measurements of direct solar irradiance were taken within 13 narrow-band channels in the 401–3676
nm wavelength range, using the IR–RAD sun-radiometer at the Sagres station in southern ...Portugal during the CLEARCOLUMN (ACE 2) experiment, from June 16 to 25 July 1997. The measurements performed on 21 clear-sky days were examined in terms of the Bouguer–Lambert–Beer law, following realistic correction procedures for Rayleigh scattering and absorption by minor atmospheric gases, to determine more than 2100 spectral series of aerosol optical depth. All these spectral series were examined with the King inversion method to retrieve the columnar aerosol particle size distributions over the 0.07–10
μm radius range, for values of the real part of the particulate refractive index ranging between 1.43 and 1.50 and values of the imaginary part between 0.003 and 0.010. Using the well-known 6S computer code for all the columnar aerosol size-distribution curves determined on ten “golden days” and both refractive index parts varying with wavelength, evaluations of the change Δ
F↑ caused by aerosol particles in the outgoing solar radiation flux were made at solar zenith angles
θ ranging between 15 and 76° and for spectral albedo features of both clear water and green vegetation surfaces. The results show that the radiative forcing Δ
F↑ assumes positive values (associated with cooling effects) for the clear water surface on all the measurement days and at all the solar zenith angles, and mostly negative values (warming effects) for the green vegetation surface in the range
θ<60°. The present evaluations also give clear evidence of the close dependence of Δ
F↑ not only on the surface albedo, solar zenith angle and aerosol optical depth but also on the mean single scattering albedo of the columnar aerosols.
During the CLEARCOLUMN campaign which took place at Sagres (Portugal) from 16 June to 25 July 1997, more than 2000 spectral measurements of direct solar irradiance were performed at thirteen ...window‐wavelengths in the 0.4–3.7 μm range, on 27 days. The measurements were performed using the IR‐RAD sun‐radiometer designed and manufactured at the Institute ISAO (FISBAT), Bologna (Italy), and carefully calibrated by applying the Langley plot method to the measurements performed on 24 October 1996, at the Schneefernerhaus Observatory on the Zugspitze (Germany). From these measurements, the values of the total atmospheric optical depth were obtained at the various wavelengths, from which the corresponding spectral values of aerosol optical depth were determined through accurate corrections for Rayleigh scattering and gaseous absorption. Such values were found to be mostly smaller than 0.1 during June and early July, presenting almost neutral spectral dependence characteristics, closely related to the prevailing oceanic origins of particulate matter. Higher values of aerosol optical thickness, mainly ranging between 0.1 and 0.5 at visible wavelengths and sharply decreasing with wavelength, were found during the rest of July in the presence of predominant contents of continental and anthropogenic aerosol particles arriving from polluted European regions. The King inversion method was applied to the spectral series of aerosol optical depth to determine the particle size‐distribution curves in the 0.2–20 μm diameter range. For 2 of these cases (one chosen for a low atmospheric loading of marine aerosols and the other for a mean content of continental/anthropogenic aerosols), the changes in the outgoing solar radiation flux produced by aerosol particles were calculated, considering different surface albedo conditions. The results obtained in the second case show that changes of opposite sign can be caused by the same atmospheric aerosol loading when passing from oceanic to continental areas.
Measurements of direct solar irradiance were taken employing 4 different sun‐photometers at near infrared wavelengths, suitable for use in atmospheric hygrometry. This technique utilising a set of ...spectral ratios, in and out of selected water vapour absorption bands, was applied to the measurements to obtain accurate evaluations of precipitable water. For all the hygrometric ratios given by the 4 sun‐photometers used at the 3 stations of Sagres, Monchique and Mt. Foia, during the CLEARCOLUMN experiment, we determined the calibration curves by correcting them for the Rayleigh scattering effects and, then, plotting the natural logarithms of such corrected ratios versus the square root of the water vapour mass present along the atmospheric slant path. The regression lines drawn for the various scatter diagrams were estimated to give evaluations of precipitable water with an uncertainty of less than 5%, 3% and 10% at the 3 stations, respectively. The calibration curves of the sun‐photometer located at the Sagres station were determined using the precipitable water evaluations obtained from the local radiosounding measurements taken on 5 clear‐sky days. Those of the sun‐photometers used at the Monchique and Mt. Foia stations were instead determined through intercomparison between subsets of measurements simultaneously taken with various instruments at Sagres and Mt. Foia. Using these calibration curves, we examined all the field measurements determining the time‐patterns of precipitable water at the 3 stations. During the period from 16 June to 25 July 1997, precipitable water was found to vary between 1.1 and 3.7 g cm−2 at the Sagres station (with an accuracy within ±13%), between 1.0 and 2.8 g cm−2 at Monchique (±11%) and between 0.8 and 3.0 g cm−2 at the top of Mt. Foia (±26%).
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