An optimal estimation algorithm for the retrieval of fog and low cloud thermodynamic and micro-physical properties

Author(s):
Bell, Alistair; Martinet, Pauline; Caumont, Olivier; Burnet, Frederic; Delanoe, Julien; Jorquera, Susana; Seity, Yann; Unger, Vinciane
Publication title: ATMOSPHERIC MEASUREMENT TECHNIQUES
2022
 | Volume: 15 | Issue: 18
2022
DOI: 10.5194/amt-15-5415-2022
Abstract:
A new generation of cloud radars, with the ability to make observations close to the surface, presents the possibility of observing fog properties wit… A new generation of cloud radars, with the ability to make observations close to the surface, presents the possibility of observing fog properties with better insight than was previously possible. The use of these instruments as part of an operational observation network could improve the prediction of fog events, something which is still a problem for even high-resolution numerical weather prediction models. However, the retrieval of liquid water content (LWC) profiles from radar reflectivity alone is an under-determined problem, something which ground-based microwave radiometer observations can help to constrain. In fact, microwave radiometers are not only sensitive to temperature and humidity profiles but are also known to be instruments of reference for the liquid water path. By providing the thermodynamic state of the atmosphere, to which the formation and evolution of fog events are highly sensitive, in addition to accurate liquid water path, which can be used to constrain the LWC retrieval from the cloud radar alone, combining microwave radiometers with cloud radars seems a natural next step to better understand and forecast fog events. To that end, a newly developed one-dimensional variational (1D-Var) algorithm designed for the retrieval of temperature, specific humidity and liquid water content profiles with both cloud radar and microwave radiometer (MWR) observations is presented in this study. The algorithm was developed to evaluate the capability of cloud radar and MWR to provide accurate LWC profiles in addition to temperature and humidity in view of assimilating the retrieved profiles into a 3D- and 4D-Var operational assimilation system. The algorithm is firstly tested on a synthetic dataset, which allows the evaluation of the developed algorithm in idealised conditions. This dataset was constructed by perturbing a high-resolution forecast dataset of fog and low-cloud cases by its expected errors. The algorithm is then tested with real data from the recent field campaign SOFOG-3D, carried out with the use of LWC measurements made from a tethered balloon platform. As expected, results from the synthetic dataset study were found to contain lower errors than those found from the retrievals on the dataset of real observations. It was found that LWC can be retrieved in idealised conditions with an uncertainty of less than 0.04 g m(-3). With real data, as expected, retrievals with a good correlation (0.7) to in situ measurements were found but with a higher uncertainty than the synthetic dataset of around 0.06 g m(-3) (41 %). This was reduced to 0.05 g m(-3) (35 %) when an accurate droplet number concentration could be prescribed to the algorithm. A sensitivity study was conducted to discuss the impact of different settings used in the 1D-Var algorithm and the forward operator. Additionally, retrievals of LWC from a real fog event observed during the SOFOG-3D field campaign were found to significantly improve the operational background profiles of the AROME (Application of Research to Operations at MEsoscale) model, showing encouraging results for future improvement of the AROME model initial state during fog conditions. more
Application Atmosphere NWP-SAF Software for CDR development

An Investigation on Causes of the Detected Surface Solar Radiation Brightening in Europe Using Satellite Data

Author(s):
Schilliger, L.; Tetzlaff, A.; Bourgeois, Q.; Correa, L.F.; Wild, M.
Publication title: Journal of Geophysical Research: Atmospheres
2024
 | Volume: 129 | Issue: 15
2024
DOI: 10.1029/2024JD041101
Abstract:
Surface solar radiation is fundamental for terrestrial life. It provides warmth to make our planet habitable, drives atmospheric circulation, the hydr… Surface solar radiation is fundamental for terrestrial life. It provides warmth to make our planet habitable, drives atmospheric circulation, the hydrological cycle and photosynthesis. Europe has experienced an increase in surface solar radiation, termed “brightening,” since the 1980s. This study investigates the causative factors behind this brightening. A novel algorithm from the EUMETSAT satellite application facility on climate monitoring (CM SAF) provides the unique opportunity to simulate surface solar radiation under various atmospheric conditions for clouds (clear-sky or all-sky), aerosol optical depth (time-varying or climatological averages) and water vapor content (with or without its direct influence on surface solar radiation). Through a multiple linear regression approach, the study attributes brightening trends to changes in these atmospheric parameters. Analyzing 61 locations distributed across Europe from 1983 to 2020, aerosols emerge as key driver during 1983–2002, with Southern Europe and high elevations showing subdued effects (0%/decade–1%/decade) versus more pronounced impacts in Northern and Eastern Europe (2%/decade–6%/decade). Cloud effects exhibit spatial variability, inducing a negative effect on surface solar radiation (−3%/decade–−2%/decade) at most investigated locations in the same period. In the period 2001–2020, aerosol effects are much smaller, while cloud effects dominate the observed brightening (2%/decade–5%/decade). This study therefore finds a substantial decrease in the cloud radiative effect over Europe in the first two decades of the 21st century. Water vapor exerts negligible influence in both sub-periods. © 2024. The Author(s). more
Application Atmosphere CM-SAF Climate Data Records

An Overview of European Efforts in Generating Climate Data Records

Author(s):
Su, Z.; Timmermans, W.; Zeng, Y.; Schulz, J.; John, V. O.; Roebeling, R. A.; Poli, P.; Tan, D.; Kaspar, F.; Kaiser-Weiss, A. K.; Swinnen, E.; Toté, C.; Gregow, H.; Manninen, T.; Riihelä, A.; Calvet, J.-C.; Ma, Y.; Wen, J.
Publication title: Bulletin of the American Meteorological Society
2018
 | Volume: 99 | Issue: 2
2018
DOI: 10.1175/BAMS-D-16-0074.1
Abstract:
Abstract The Coordinating Earth Observation Data Validation for Reanalysis for Climate Services project (CORE-CLIMAX) aimed to substantiate how Copern… Abstract The Coordinating Earth Observation Data Validation for Reanalysis for Climate Services project (CORE-CLIMAX) aimed to substantiate how Copernicus observations and products can contribute to climate change analyses. CORE-CLIMAX assessed the European capability to provide climate data records (CDRs) of essential climate variables (ECVs), prepared a structured process to derive CDRs, developed a harmonized approach for validating essential climate variable CDRs, identified the integration of CDRs into the reanalysis chain, and formulated a process to compare the results of different reanalysis techniques. With respect to the Copernicus Climate Change Service (C3S), the systematic application and further development of the CORE-CLIMAX system maturity matrix (SMM) and the spinoff application performance metric (APM) were strongly endorsed to be involved in future implementations of C3S. We concluded that many of the current CDRs are not yet sufficiently mature to be used in reanalysis or applied in climate studies. Thus, the production of consistent high-resolution data records remains a challenge that needs more research urgently. Extending ECVs to close climate cycle budgets (e.g., essential water variables) is a next step linking CDRs to sectoral applications. more
Application EUM-Secr International cooperation Validation

An overview of the enhanced cloud and water vapour products from EUMETSAT new generation imagers

Author(s):
Spezzi, L.; Bozzo, A.; Jackson, J.; Lutz, H.J.; do Couto, A.B.; Watts, P.; August, T.; Fougnie, B.; Bojkov, B.
2023
 | Volume: 12730
2023
DOI: 10.1117/12.2679703
Abstract:
The EUMETSAT Central Facility retrieves and disseminates several near-real time geophysical products from both geostationary and polar VIS/IR imagers.… The EUMETSAT Central Facility retrieves and disseminates several near-real time geophysical products from both geostationary and polar VIS/IR imagers. The primary scope of these missions is to serve numerical weather prediction (NWP), nowcasting and climate monitoring. In this contribution, we focus on the cloud and water vapour (WV) imaging products from the new generation EUMETSAT imagers i.e., the Flexible Combined Imager (FCI) on board of Meteosat Third Generation (MTG-I, launched in Dec 2022) and METimage on board EUMETSAT Polar System Second Generation (EPS-SG, expected 2024+). These instruments provide unprecedented spatial resolution (down to 500m at Nadir), temporal sampling (10min for the geostationary FCI), and wider spectral range (approximately 0.4-13µm) including WV (~0.9µm, 1.38µm, ~6.7µm, ~7.3µm), O2 A-band (0.762µm), and CO2 (~13.3µm) absorption channels. We present the retrieval and validation approach chosen for these products and the challenges presented by the near-real time operational processing. We explore, in particular, the expected improvements based on the enhanced instrument’s capabilities (i.e., more accurate cloud detection, layering, altitude and spatial inhomogeneity), while maintaining continuity with the legacy products from their predecessor satellites. In particular, the new ~0.9µm channel allows improved daytime estimates of WV amount near the surface. We show preliminary cloud and WV products retrieved from early FCI measurements, including their validation strategy against independent cloud observations from the ground-based ACTRIS network and humidly measurements from IGRA radiosondes. © 2023 SPIE. more
Atmosphere Climate Data Records EUM-Secr Method NWP-SAF

An Uncertainty Quantified Fundamental Climate Data Record for Microwave Humidity Sounders

Author(s):
Hans, Imke; Burgdorf, Martin; Buehler, Stefan; Prange, Marc; Lang, Theresa; John, Viju
Publication title: Remote Sensing
2019
 | Volume: 11 | Issue: 5
2019
DOI: 10.3390/rs11050548
Abstract:
To date, there is no long-term, stable, and uncertainty-quantified dataset of upper tropospheric humidity (UTH) that can be used for climate research.… To date, there is no long-term, stable, and uncertainty-quantified dataset of upper tropospheric humidity (UTH) that can be used for climate research. As intermediate step towards the overall goal of constructing such a climate data record (CDR) of UTH, we produced a new fundamental climate data record (FCDR) on the level of brightness temperature for microwave humidity sounders that will serve as basis for the CDR of UTH. Based on metrological principles, we constructed and implemented the measurement equation and the uncertainty propagation in the processing chain for the microwave humidity sounders. We reprocessed the level 1b data to obtain newly calibrated uncertainty quantified level 1c data in brightness temperature. Three aspects set apart this FCDR from previous attempts: (1) the data come in a ready-to-use NetCDF format; (2) the dataset provides extensive uncertainty information taking into account the different correlation behaviour of the underlying errors; and (3) inter-satellite biases have been understood and reduced by an improved calibration. Providing a detailed uncertainty budget on these data, this new FCDR provides valuable information for a climate scientist and also for the construction of the CDR. more
Application Climate Data Records EUM-Secr Method

Analysis of Daytime Cloud Fraction Spatiotemporal Variation over the Arctic from 2000 to 2019 from Multiple Satellite Products

Author(s):
Liu, Xinyan; He, Tao; Sun, Lin; Xiao, Xiongxin; Liang, Shunlin; Li, Siwei
Publication title: Journal of Climate
2022
 | Volume: 35 | Issue: 23
2022
DOI: 10.1175/JCLI-D-22-0007.1
Abstract:
Abstract Insufficient understanding of complex Arctic cloud properties introduced large errors in estimating radiant energy balance parameters at the … Abstract Insufficient understanding of complex Arctic cloud properties introduced large errors in estimating radiant energy balance parameters at the regional and global scales. Comprehensive and reliable cloud information is necessary for improving the accuracy of flux inversion. This study evaluated daytime cloud fraction (CF) uncertainties from 16 available satellite products and estimated the spatiotemporal distributions of Arctic daytime CF during 2000–19. Our results show that the differences among multiple products had significant temporal and spatial heterogeneities. Temporally, the maximum and minimum interproduct discrepancies occurred in April and the summer months, respectively. Spatially, the largest uncertainties were seen over Greenland. Substantial inconsistency also occurred on the central and Pacific sides of the Arctic Ocean. The active satellite product tended to capture more clouds in these two regions. We found that the inconsistencies caused by sensor differences were smaller than those caused by algorithm differences; that is, for MODIS based CF products, the inconsistencies caused by different sensors and different algorithms are ±2% and ±5%, while for AVHRR-based products, these inconsistencies are ±6% and ±15%, respectively. The annual average daytime CF in sunlit months was 70.9% ± 2.93% and increased over the Arctic during study periods. These upward trends might cool the Arctic by approximately 0.05–0.5 W m−2 decade−1. In terms of the spatiotemporal distributions, the CF over the ocean is higher than that over the land, and the former increased significantly while the latter decreased; the CF trends of most products are positive in June and July but are opposite in other months. From this study, the findings based on multiple products would be more robust than that based on a single or few datasets. Significance Statement This study aimed to comprehensively understand and obtain more robust general characteristics of the temporal and spatial distributions of Arctic daytime cloud fraction by comparing and analyzing the consistencies and discrepancies of multisource satellite products. It is important because the cloud fraction is a nonnegligible modulator of Earth’s energy budget and climate change. Although the Arctic is the most climate-sensitive region, existing studies lack a comprehensive assessment of the cloud fraction over the entire Arctic. We analyzed 16 different cloud products and found that although the inconsistencies were inevitable, most products showed similar spatiotemporal distribution and trend distribution of daytime CF. This study provided a new idea for Arctic CF research under the existing conditions. more
Atmosphere CM-SAF Climate Data Records Validation

Analysis of Mineral Aerosol in the Surface Layer over the Caspian Lowland Desert by the Data of 12 Summer Field Campaigns in 2002-2020

Author(s):
Chkhetiani, Otto G.; Vazaeva, Natalia V.; Chernokulsky, Alexander, V; Shukurov, Karim A.; Gubanova, Dina P.; Artamonova, Maria S.; Maksimenkov, Leonid O.; Kozlov, Fedor A.; Kuderina, Tatyana M.
Publication title: ATMOSPHERE
2021
 | Volume: 12 | Issue: 8
2021
DOI: 10.3390/atmos12080985
Abstract:
In-situ knowledge on characteristics of mineral aerosols is important for weather and climate prediction models, particularly for modeling such proces… In-situ knowledge on characteristics of mineral aerosols is important for weather and climate prediction models, particularly for modeling such processes as the entrainment, transport and deposition of aerosols. However, field measurements of the dust emission flux, dust size distribution and its chemical composition under realistic wind conditions remain rare. In this study, we present experimental data over annual expeditions in the arid and semi-arid zones of the Caspian Lowland Desert (Kalmykia, south of Russia); we evaluate characteristics of mineral aerosol concentration and fluxes, estimate its chemical composition and calculate its long-distance transport characteristics. The mass concentration in different years ranges from several tens to several hundred of mu g m(-3). The significant influence of wind velocity on the value of mass and counting concentration and on the proposed entrainment mechanisms is confirmed. An increased content of anthropogenic elements (S, Sn, Pb, Bi, Mo, Ag, Cd, Hg, etc.), which is characteristic for all observation points in the south of the European Russia, is found. The trajectory analysis show that long-range air particles transport from the Caspian Lowland Desert to the central regions of European Russia tends to increase in the recent decades. more
Application Atmosphere CM-SAF Climate Data Records

Analysis of current validation practices in Europe for space-based climate data records of essential climate variables

Author(s):
Zeng, Y.; Su, Z.; Calvet, J.-C.; Manninen, T.; Swinnen, E.; Schulz, J.; Roebeling, R.; Poli, P.; Tan, D.; Riihelä, A.; Tanis, C.-M.; Arslan, A.-N.; Obregon, A.; Kaiser-Weiss, A.; John, V.O.; Timmermans, W.; Timmermans, J.; Kaspar, F.; Gregow, H.; Barbu, A.-L.; Fairbairn, D.; Gelati, E.; Meurey, C.
Publication title: International Journal of Applied Earth Observation and Geoinformation
2015
 | Volume: 42
2015
DOI: 10.1016/j.jag.2015.06.006
Abstract:
The Climate Data Records (CDRs) of Essential Climate Variables (ECVs) that are based on satellite observations need to be precisely described. In part… The Climate Data Records (CDRs) of Essential Climate Variables (ECVs) that are based on satellite observations need to be precisely described. In particular, when these products are delivered to end-users, the error characteristics information and how this information is obtained (e.g., through a validation process) need to be documented. Such validation information is intended to help end-users understanding to what extent the product is suitable for their specific applications. Based on how different European initiatives approached the validation of CDR and ECV products, we reviewed several aspects of the current validation practices. Based on the analysis of current practices, essentials of validation are discussed. A generic validation process is subsequently proposed, together with a quality indicator. more
EUM-Secr International cooperation Validation

Analysis of Spanish Radiometric Networks with the Novel Bias-Based Quality Control (BQC) Method

Author(s):
Urraca, Ruben; Antonanzas, Javier; Sanz-Garcia, Andres; Martinez-de-Pison, Francisco Javier
Publication title: Sensors
2019
 | Volume: 19 | Issue: 11
2019
DOI: 10.3390/s19112483
Abstract:
Different types of measuring errors can increase the uncertainty of solar radiation measurements, but most common quality control (QC) methods do not … Different types of measuring errors can increase the uncertainty of solar radiation measurements, but most common quality control (QC) methods do not detect frequent defects such as shading or calibration errors due to their low magnitude. We recently presented a new procedure, the Bias-based Quality Control (BQC), that detects low-magnitude defects by analyzing the stability of the deviations between several independent radiation databases and measurements. In this study, we extend the validation of the BQC by analyzing the quality of all publicly available Spanish radiometric networks measuring global horizontal irradiance (9 networks, 732 stations). Similarly to our previous validation, the BQC found many defects such as shading, soiling, or calibration issues not detected by classical QC methods. The results questioned the quality of SIAR, Euskalmet, MeteoGalica, and SOS Rioja, as all of them presented defects in more than 40% of their stations. Those studies based on these networks should be interpreted cautiously. In contrast, the number of defects was below a 5% in BSRN, AEMET, MeteoNavarra, Meteocat, and SIAR Rioja, though the presence of defects in networks such as AEMET highlights the importance of QC even when using a priori reliable stations. more
Application Atmosphere CM-SAF Climate Data Records
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