Introducing New Metrics for the Atmospheric Pressure Adjustment to Thermal Structures at the Ocean Surface

Author(s):
Meroni, Agostino N.; Desbiolles, Fabien; Pasquero, Claudia
Publication title: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
2022
 | Volume: 127 | Issue: 16
2022
DOI: 10.1029/2021JD035968
Abstract:
Thermal structures at the sea surface are known to affect the overlying atmospheric dynamics over various spatio-temporal scales, from hourly and sub-… Thermal structures at the sea surface are known to affect the overlying atmospheric dynamics over various spatio-temporal scales, from hourly and sub-kilometric to annual and O(1,000 km). The relevant mechanisms at play are generally identified by means of correlation coefficients (in space or time) or by linear regression analysis using appropriate couples of variables. For fine spatial scales, where sea surface temperature (SST) gradients get stronger, the advection might disrupt these correlations and, thus, mask the action of such mechanisms, just because of the chosen metrics. For example, at the oceanic sub-mesoscale, around 1-10 km and hourly time scales, the standard metrics used to identify the pressure adjustment mechanism (that involves the Laplacian of sea surface temperature, SST, and the wind divergence) may suffer from this issue, even for weak wind conditions. By exploiting high-resolution realistic numerical simulations with ad hoc SST forcing fields, we introduce some new metrics to evaluate the action of the pressure adjustment atmospheric response to the surface oceanic thermal structures. It is found that the most skillful metrics is based on the wind divergence and the SST second spatial derivative evaluated in the across direction of a locally defined background wind field. more
Application Atmosphere Climate Data Records OSI-SAF Ocean

Land Surface Albedo from Geostationary Satelites: A Multiagency Collaboration within SCOPE-CM

Author(s):
Lattanzio, Alessio; Schulz, Jörg; Matthews, Jessica; Okuyama, Arata; Theodore, Bertrand; Bates, John J.; Knapp, Kenneth R.; Kosaka, Yuki; Schüller, Lothar
Publication title: Bulletin of the American Meteorological Society
2013
 | Volume: 94 | Issue: 2
2013
DOI: 10.1175/BAMS-D-11-00230.1
Abstract:
Climate has been recognized to have direct and indirect impact on society and economy, both in the long term and daily life. The challenge of understa… Climate has been recognized to have direct and indirect impact on society and economy, both in the long term and daily life. The challenge of understanding the climate system, with its variability and changes, is enormous and requires a joint long-term international commitment from research and governmental institutions. An important international body to coordinate worldwide climate monitoring efforts is the World Meteorological Organization (WMO). The Global Climate Observing System (GCOS) has the mission to provide coordination and the requirements for global observations and essential climate variables (ECVs) to monitor climate changes. The WMO-led activity on Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) is responding to these requirements by ensuring a continuous and sustained generation of climate data records (CDRs) from satellite data in compliance with the principles and guidelines of GCOS. SCOPE-CM represents a new partnership between operational space agencies to coordinate the generation of CDRs. To this end, pilot projects for different ECVs, such as surface albedo, cloud properties, water vapor, atmospheric motion winds, and upper-tropospheric humidity, have been initiated. The coordinated activity on land surface albedo involves the operational meteorological satellite agencies in Europe [European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT)], in Japan [the Japan Meteorological Agency (JMA)], and in the United States [National Oceanic and Atmospheric Administration (NOAA)]. This paper presents the first results toward the generation of a unique land surface albedo CDR, involving five different geostationary satellite positions and approximately three decades of data starting in the 1980s, and combining close to 30 different satellite instruments. more
Climate Data Records EUM-Secr Land Validation

Investigating the sensitivity to resolving aerosol interactions in downscaling regional model experiments with WRFv3.8.1 over Europe

Author(s):
Pavlidis, V.; Katragkou, E.; Prein, A.; Georgoulias, A.K.; Kartsios, S.; Zanis, P.; Karacostas, T.
Publication title: Geoscientific Model Development
2020
 | Volume: 13 | Issue: 6
2020
DOI: 10.5194/gmd-13-2511-2020
Abstract:
In this work we present downscaling experiments with the Weather Research and Forecasting model (WRF) to test the sensitivity to resolving aerosol-rad… In this work we present downscaling experiments with the Weather Research and Forecasting model (WRF) to test the sensitivity to resolving aerosol-radiation and aerosol-cloud interactions on simulated regional climate for the EURO-CORDEX domain. The sensitivities mainly focus on the aerosol-radiation interactions (direct and semi-direct effects) with four different aerosol optical depth datasets (Tegen, MAC-v1, MACC, GOCART) being used and changes to the aerosol absorptivity (single scattering albedo) being examined. Moreover, part of the sensitivities also investigates aerosol-cloud interactions (indirect effect). Simulations have a resolution of 0.44 and are forced by the ERA-Interim reanalysis. A basic evaluation is performed in the context of seasonal-mean comparisons to ground-based (E-OBS) and satellite-based (CM SAF SARAH, CLARA) benchmark observational datasets. The impact of aerosols is calculated by comparing it against a simulation that has no aerosol effects. The implementation of aerosol-radiation interactions reduces the direct component of the incoming surface solar radiation by 20 %-30% in all seasons, due to enhanced aerosol scattering and absorption. Moreover the aerosol-radiation interactions increase the diffuse component of surface solar radiation in both summer (30 %-40 %) and winter (5 %-8 %), whereas the overall downward solar radiation at the surface is attenuated by 3 %-8 %. The resulting aerosol radiative effect is negative and is comprised of the net effect from the combination of the highly negative direct aerosol effect (-17 to-5Wm-2) and the small positive changes in the cloud radiative effect (C5Wm-2), attributed to the semi-direct effect. The aerosol radiative effect is also stronger in summer (-12Wm-2) than in winter (-2Wm-2).We also show that modelling aerosol-radiation and aerosol-cloud interactions can lead to small changes in cloudiness, mainly regarding low-level clouds, and circulation anomalies in the lower and mid-troposphere, which in some cases, mainly close to the Black Sea in autumn, can be of statistical significance. Precipitation is not affected in a consistent pattern throughout the year by the aerosol implementation, and changes do not exceed-5% except for the case of unrealistically absorbing aerosol. Temperature, on the other hand, systematically decreases by-0.1 to-0.5 °C due to aerosol-radiation interactions with regional changes that can be up to-1.5 °C. © 2020 Authors. more
Application Atmosphere CM-SAF Climate Data Records

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
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