Joint estimation of sea ice and atmospheric state from microwave imagers in operational weather forecasting

Author(s):
Geer, A.J.
Publication title: Quarterly Journal of the Royal Meteorological Society
2024
 | Volume: 150 | Issue: 763
2024
DOI: 10.1002/qj.4797
Abstract:
Satellite-observed microwave radiances provide information on both surface and atmosphere. For operational weather forecasting, information on atmosph… Satellite-observed microwave radiances provide information on both surface and atmosphere. For operational weather forecasting, information on atmospheric temperature, humidity, cloud, and precipitation is inferred directly using all-sky radiance data assimilation. In contrast, information on the surface state, such as sea-surface temperature (SST) and sea-ice concentration (SIC), is typically provided through third-party retrieval products. Scientifically, this is a sub-optimal use of the observations, and practically it has disadvantages such as time delays of more than 48 h. A better solution is to estimate the surface and atmospheric state jointly from the radiance observations. This has not been possible until now, due to incomplete knowledge of the surface state and the radiative transfer that links this to the observed radiances. A new approach based on an empirical state and an empirical sea-ice surface emissivity model is used here to add sea-ice state estimation, including SIC, to the European Centre for Medium-range Weather Forecasts atmospheric data assimilation system. The sea-ice state is estimated using augmented control variables at the observation locations. The resulting SIC estimates are of good quality and they highlight apparent defects in the existing OCEAN5 sea-ice analysis. The SIC estimates can also be used to track giant icebergs, which may provide a novel maritime application for passive microwave radiances. Further, the SIC estimates should be suitable for onward use in coupled ocean–atmosphere data assimilation. There is also increased coverage of microwave observations in the proximity of sea ice, leading to improved atmospheric forecasts out to day 4 in the Southern Ocean. © 2024 ECMWF. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. more
Atmosphere Climate Data Records Cryosphere NWP-SAF OSI-SAF Software for CDR development

Land Surface Albedo Derived on a Ten Daily Basis from Meteosat Second Generation Observations: The NRT and Climate Data Record Collections from the EUMETSAT LSA SAF

Author(s):
Carrer, Dominique; Moparthy, Suman; Lellouch, Gabriel; Ceamanos, Xavier; Pinault, Florian; Freitas, Sandra; Trigo, Isabel
Publication title: Remote Sensing
2018
 | Volume: 10 | Issue: 8
2018
DOI: 10.3390/rs10081262
Abstract:
Land surface albedo determines the splitting of downwelling solar radiation into components which are either reflected back to the atmosphere or absor… Land surface albedo determines the splitting of downwelling solar radiation into components which are either reflected back to the atmosphere or absorbed by the surface. Land surface albedo is an important variable for the climate community, and therefore was defined by the Global Climate Observing System (GCOS) as an Essential Climate Variable (ECV). Within the scope of the Satellite Application Facility for Land Surface Analysis (LSA SAF) of EUMETSAT (European Organization for the Exploitation of Meteorological Satellites), a near-real time (NRT) daily albedo product was developed in the last decade from observations provided by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument on board the geostationary satellites of the Meteosat Second Generation (MSG) series. In this study we present a new collection of albedo satellite products based on the same satellite data. The MSG Ten-day Albedo (MTAL) product incorporates MSG observations over 31 days with a frequency of NRT production of 10 days. The MTAL collection is more dedicated to climate analysis studies compared to the daily albedo that was initially designed for the weather prediction community. For this reason, a homogeneous reprocessing of MTAL was done in 2018 to generate a climate data record (CDR). The resulting product is called MTAL-R and has been made available to the community in addition to the NRT version of the MTAL product which has been available for several years. The retrieval algorithm behind the MTAL products comprises three distinct modules: One for atmospheric correction, one for daily inversion of a semi-empirical model of the bidirectional reflectance distribution function, and one for monthly composition, that also determines surface albedo values. In this study the MTAL-R CDR is compared to ground surface measurements and concomitant albedo products collected by sensors on-board polar-orbiting satellites (SPOT-VGT and MODIS). We show that MTAL-R meets the quality requirements if MODIS or SPOT-VGT are considered as reference. This work leads to 14 years of production of geostationary land surface albedo products with a guaranteed continuity in the LSA SAF for the future years with the forthcoming third generation of European geostationary satellites. more
Application Climate Data Records LSA-SAF Land Validation

Lessons Learned from the Updated GEWEX Cloud Assessment Database

Author(s):
Stubenrauch, C.J.; Kinne, S.; Mandorli, G.; Rossow, W.B.; Winker, D.M.; Ackerman, S.A.; Chepfer, H.; Di Girolamo, L.; Garnier, A.; Heidinger, A.; Karlsson, K.-G.; Meyer, K.; Minnis, P.; Platnick, S.; Stengel, M.; Sun-Mack, S.; Veglio, P.; Walther, A.; Cai, X.; Young, A.H.; Zhao, G.
Publication title: Surveys in Geophysics
2024
 | Volume: 45 | Issue: 6
2024
DOI: 10.1007/s10712-024-09824-0
Abstract:
Since the first Global Energy and Water Exchanges cloud assessment a decade ago, existing cloud property retrievals have been revised and new retrieva… Since the first Global Energy and Water Exchanges cloud assessment a decade ago, existing cloud property retrievals have been revised and new retrievals have been developed. The new global long-term cloud datasets show, in general, similar results to those of the previous assessment. A notable exception is the reduced cloud amount provided by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Science Team, resulting from an improved aerosol–cloud distinction. Height, opacity and thermodynamic phase determine the radiative effect of clouds. Their distributions as well as relative occurrences of cloud types distinguished by height and optical depth are discussed. The similar results of the two assessments indicate that further improvement, in particular on vertical cloud layering, can only be achieved by combining complementary information. We suggest such combination methods to estimate the amount of all clouds within the atmospheric column, including those hidden by clouds aloft. The results compare well with those from CloudSat-CALIPSO radar–lidar geometrical profiles as well as with results from the International Satellite Cloud Climatology Project (ISCCP) corrected by the cloud vertical layer model, which is used for the computation of the ISCCP-derived radiative fluxes. Furthermore, we highlight studies on cloud monitoring using the information from the histograms of the database and give guidelines for: (1) the use of satellite-retrieved cloud properties in climate studies and climate model evaluation and (2) improved retrieval strategies. © The Author(s) 2024. more
Atmosphere CM-SAF Climate Data Records Validation

Life Cycle of Shallow Marine Cumulus Clouds From Geostationary Satellite Observations

Author(s):
Seelig, Torsten; Deneke, Hartwig; Quaas, Johannes; Tesche, Matthias
Publication title: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
2021
 | Volume: 126 | Issue: 22
2021
DOI: 10.1029/2021JD035577
Abstract:
An analysis of the life cycle of shallow marine cumulus clouds is presented based on geostationary observations by the Spinning Enhanced Visible and I… An analysis of the life cycle of shallow marine cumulus clouds is presented based on geostationary observations by the Spinning Enhanced Visible and InfraRed Imager aboard Meteosat Second Generation (MSG-SEVIRI). Trajectories of about 250,000 individual shallow marine cumulus clouds have been derived by applying Particle Image Velocimetry to the Satellite Application Facility on Climate Monitoring CLoud property dAtAset using SEVIRI for a region in the trade wind zone centered around the Canary Islands in August 2015. The temporal evolution of the physical properties of these clouds allows to characterize cloud development and to infer the distribution of cloud life time and cloud extent. In the derived data set, the life time distribution follows a double power law with most clouds existing on a time scale of tens of minutes. The cloud physical properties, available during daytime, are analyzed along the cloud tracks. Relative time series of cloud extent, cloud water path, cloud droplet effective radius at cloud top, cloud optical thickness, and cloud droplet number concentration for clouds in two temporal ranges reveal conditions that can be attributed to long-lasting clouds. Clouds of a certain horizontal extent and cloud top height as well as cloud droplet radius show longer life times if they are optically more dense, i.e., have a higher droplet number concentration. Furthermore, the investigation of the content of liquid cloud water regarding cloud life time and cloud extent shows that small short-living clouds significantly contribute to cloud radiative effects. more
Application Atmosphere CM-SAF Climate Data Records

Limited Benefits of Increased Spatial Resolution for Sea Ice in HighResMIP Simulations

Author(s):
Selivanova, J.; Iovino, D.; Vichi, M.
Publication title: Geophysical Research Letters
2024
 | Volume: 51 | Issue: 14
2024
DOI: 10.1029/2023GL107969
Abstract:
State-of-the-art coupled climate models struggle to accurately simulate historical variability and trends of Antarctic sea ice, impacting their reliab… State-of-the-art coupled climate models struggle to accurately simulate historical variability and trends of Antarctic sea ice, impacting their reliability for future projections. Increasing horizontal resolution is expected to improve the representation of coupled atmosphere-ice-ocean processes at high latitudes. Here, we examine the historical changes in the Antarctic sea ice area and volume in High Resolution Model Intercomparison Project simulations against satellite data sets and ocean reanalyzes to assess the benefits of increased spatial resolution. Our results do not show considerable benefits when horizontal resolutions up to 0.25° in the ocean and 25 km in the atmosphere. Limited improvements are reported in the simulated historical sea ice trends, which are nevertheless model-dependent, and associated with the use of model components with more complex sea-ice parameterizations. Given the high computational cost of climate-scale simulations at high spatial resolution, we advocate prioritizing enhancements in sea-ice physics and the interactions among model components in coupled climate simulations. © 2024. The Author(s). more
Application Climate Data Records Cryosphere OSI-SAF Validation

Linking scales of sea ice surface topography: evaluation of ICESat-2 measurements with coincident helicopter laser scanning during MOSAiC

Author(s):
Ricker, R; Fons, S; Jutila, A; Hutter, N; Duncan, K; Farrell, SL; Kurtz, NT; Hansen, RMF
Publication title: CRYOSPHERE
2023
 | Volume: 17 | Issue: 3
2023
DOI: 10.5194/tc-17-1411-2023
Abstract:
Information about sea ice surface topography and related deformation is crucial for studies of sea ice mass balance, sea ice modeling, and ship naviga… Information about sea ice surface topography and related deformation is crucial for studies of sea ice mass balance, sea ice modeling, and ship navigation through the ice pack. The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2), part of the National Aeronautics and Space Administration (NASA) Earth Observing System, has been on orbit for over 4 years, sensing the sea ice surface topography with six laser beams capable of capturing individual features such as pressure ridges. To assess the capabilities and uncertainties of ICESat-2 products, coincident high-resolution measurements of sea ice surface topography are required. During the yearlong Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the Arctic Ocean, we successfully carried out a coincident underflight of ICESat-2 with a helicopter-based airborne laser scanner (ALS), achieving an overlap of more than 100 km. Despite the comparably short data set, the high-resolution centimeter-scale measurements of the ALS can be used to evaluate the performance of ICESat-2 products. Our goal is to investigate how the sea ice surface roughness and topography are represented in different ICESat-2 products as well as how sensitive ICESat-2 products are to leads and small cracks in the ice cover. Here, we compare the ALS measurements with ICESat-2's primary sea ice height product, ATL07, and the high-fidelity surface elevation product developed by the University of Maryland (UMD). By applying a ridge-detection algorithm, we find that 16 % (4 %) of the number of obstacles in the ALS data set are found using the strong (weak) center beam in ATL07. Significantly higher detection rates of 42 % (30 %) are achieved when using the UMD product. While only one lead is indicated in ATL07 for the underflight, the ALS reveals many small, narrow, and only partly open cracks that appear to be overlooked by ATL07. more
Application Climate Data Records Cryosphere OSI-SAF Ocean

Long-Term Variations and Its Driving Factors of the TOA Albedo over the Loess Plateau

Author(s):
Wang, Qianru; Zhang, Shuhua
2024
2024
DOI: 10.1175/JCLI-D-23-0380.1
Abstract:
Solar radiation balances significantly affect Earth’s surface energy balance and climate change. Studying top-of-the-atmosphere (TOA) albedo changes i… Solar radiation balances significantly affect Earth’s surface energy balance and climate change. Studying top-of-the-atmosphere (TOA) albedo changes is of great significance for understanding Earth’s energy budget and atmospheric circulation. The Loess Plateau (LP), located in the middle reaches of the Yellow River in China, is one of the most severely eroded areas in the world. In this paper, long-term remote sensing data were used to analyze the changes in the TOA albedo in the LP from 1982 to 2016. The results showed that the TOA albedo, its atmospheric contribution (AC), and surface contribution (SC) exhibited decreasing trends: −0.0012, −0.0010, and −0.0003 a−1. The spatial pattern of the TOA albedo was similar to AC, which indicates that AC dominates the change in the TOA albedo. We detected driving factors for AC and SC and found that the cloud fraction (CF) was the main driving factor of the AC, whereas the soil moisture (SM) dominated the SC. The driving factors of two typical regions with a significantly decreasing trend in the TOA albedo were also detected. The Mu Us Desert, where vegetation improved significantly, showed a decreasing trend in the TOA albedo, and we found that NDVI was the main driving factor for the change in the SC of the TOA albedo. However, the Eastern Qilian Mountains, where snow cover decreased in recent years, also showed a significant decreasing trend in the TOA albedo; the SC here was mainly driven by the changes in snow cover days (SCD). These results indicate that changes in the surface environment alter the radiation balance. Significance Statement The Loess Plateau in China is one of the most severe cases of soil erosion in the world, and ecological restoration projects have been carried out to recover the fragile ecological environment. Our study was designed to explore changes in the top-of-the-atmosphere (TOA) albedo of the Loess Plateau between 1982 and 2016 using a long time series of multisource satellite products, and driving factors in the atmosphere and at the surface were analyzed. We concluded that the TOA albedo of the Loess Plateau decreased over 35 years, and its atmospheric contribution dominated the change in the TOA albedo. However, the significant ecological improvement in the Loess Plateau, especially in the central vegetation recovery region, such as the Mu Us Desert, was also strongly related to the regional changes in the surface contribution of the TOA albedo. The climate changes had a considerable impact on the eastern branch of the Qilian Mountains in the Qinghai region, where the decline in snow cover days affected the local Alpine meadow ecosystems; therefore, snow cover days also played a decisive role in the local variation of the surface contribution of the TOA albedo. more
Application Atmosphere CM-SAF Climate Data Records Terrestrial

Local analytical optimal nudging for assimilating AMSR2 sea ice concentration in a high-resolution pan-Arctic coupled ocean (HYCOM 2.2.98) and sea ice (CICE 5.1.2) model

Author(s):
Wang, K.; Ali, A.; Wang, C.
Publication title: Cryosphere
2023
 | Volume: 17 | Issue: 10
2023
DOI: 10.5194/tc-17-4487-2023
Abstract:
Local analytical optimal nudging (LAON) is introduced and thoroughly evaluated for assimilating the Advanced Microwave Scanning Radiometer 2 (AMSR2) s… Local analytical optimal nudging (LAON) is introduced and thoroughly evaluated for assimilating the Advanced Microwave Scanning Radiometer 2 (AMSR2) sea ice concentration (SIC) in the Norwegian High-resolution pan-Arctic ocean and sea ice Prediction System (NorHAPS). NorHAPS is a developing high-resolution (3-5 km) pan-Arctic coupled ocean and sea ice modeling and prediction system based on the HYbrid Coordinate Ocean Model (HYCOM version 2.2.98) and the Los Alamos multi-category sea ice model (CICE version 5.1.2), with the LAON for data assimilation. In this study, our focus is on the LAON assimilation of AMSR2 SIC, which is designed to update the model SIC in every time step such that the analysis will eventually reach the optimal estimate. The SIC innovation (observation minus model) is designed to be proportionally distributed to the multiple sea ice categories. A hindcast experiment is performed with and without the LAON assimilation for the period 1 January 2021 to 30 April 2022, in which the extra computational cost for the LAON assimilation is about 5 % of the free run without assimilation. The results show that the LAON assimilation greatly improves the simulated sea ice concentration, extent, area, thickness, and volume, as well as the sea surface temperature (SST). It also produces significantly more accurate sea ice edge and marginal zone (MIZ) than the observed AMSR2 SIC that is assimilated when evaluated against the Norwegian Ice Service (NIS) ice chart. The results are also compared with the Copernicus Marine Environment Monitoring Service (CMEMS) operational SIC analyses from NEMO, TOPAZ4, and neXtSIM, which use ensemble Kalman filters and direct insertion for data assimilation. It is shown that the LAON assimilation produces significantly lower integrated ice edge error (IIEE) and integrated MIZ error (IME) than the CMEMS SIC analyses when evaluated against the NIS ice chart. LAON also produces a continuous and smooth evolution of sub-daily SIC, which avoids abrupt jumps often seen in other assimilated products. This efficient and accurate method is promising for data assimilation in global and high-resolution models. © 2023 Keguang Wang et al. more
Application Climate Data Records Cryosphere OSI-SAF Ocean

Long-Term Scatterometer Wind Climate Data Records

Author(s):
Verhoef, Anton; Vogelzang, Jur; Verspeek, Jeroen; Stoffelen, Ad
Publication title: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
2017
 | Volume: 10 | Issue: 5
2017
DOI: 10.1109/JSTARS.2016.2615873
Abstract:
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Ocean and Sea Ice Satellite Application Facility (OSI SAF) prod… The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Ocean and Sea Ice Satellite Application Facility (OSI SAF) produces near-real-time scatterometer ocean vector winds since almost 20 years already. Data from the European remote sensing satellites (ERS-1 and ERS-2 scatterometer), QuikSCAT (SeaWinds), Metop (ASCAT), Oceansat 2 (OSCAT), and RapidScat on the International Space Station have been, or are being, produced. The OSI SAF scatterometer products, produced at the Royal Netherlands Meteorological Institute, provide superior comparison to both buoy and numerical weather prediction (NWP) datasets. Moreover, the wind processing software is publicly available through the EUMETSAT NWP SAF. An increasing amount of users employs scatterometer wind data for climate studies. However, the wind retrieval algorithms have been continuously improved over the years and the currently existing archives of near-real-time data are not always suitable to fulfill the need for homogeneous datasets spanning a longer period of time. Currently, only few validated vector wind climate datasets are available. Therefore, the OSI SAF is reprocessing several offline datasets. This paper is focusing on two climate data records from SeaWinds and ASCAT winds, which together span the period from 1999 to 2014. The data are compared to the NWP model and buoy winds. The stability of the wind characteristics is assessed and an attempt is made to attribute temporal changes to climatological and NWP model changes over time. more
Atmosphere Climate Data Records OSI-SAF Validation
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