Análisis no lineal de las series temporales de medidas de la SST del sistema ENSO

Ponencia presentada en: I Congreso de la Asociación Española de Climatología “La climatología española en los albores del siglo XXI”, celebrado en Barcelona del 1 al 3 de diciembre de 1999.[ES]En una disciplina como la Climatología nos vemos obligados a tratar con sistemas disipativos altamente no lineales. En este trabajo analizamos la dinámica del sistema ENSO (acrónimo de El Niño-Southern Oscillation) mediante técnicas no lineales. Para ello, estudiaremos las series temporales de la temperatura superficial del mar (SST).[EN]In Climatology we have to work with nonlinear systems. This paper introduces the main concepts in nonlinear dynamics. Starting with a sequence of measurements -a time series- we want to see what the actual data tells us about the system dynamics. In our work the time series is the SST of ENSO system

Induced surface fluxes: A new framework for attributing Arctic sea ice volume balance biases to specific model errors

This is the final version. Available on open access from EGU via the DOI in this recordCode availability. The code used to create the fields of induced surface flux bias is written in Python and is provided as a Supplement (directory “ISF”). The code used to create Figs. 1–9, as well as Fig. B1, is also provided (directory “Figures”). In addition, the routines used to estimate errors in the ISF analysis are provided (directory “Analysis”). Finally, the code used to create Table 1 is provided (directory “Tables”). A set of auxiliary routines used by most of the above are also provided (directory “Library”). Most routines make use of the open-source Iris library, and several make use of the open-source Cartopy library.Data availability. Monthly mean ice thickness, ice fraction, snow thickness and surface radiation, as well as daily surface temperature and surface radiation, for the historical simulations of HadGEM2-ES, are available from the CMIP5 archive at https://cmip.llnl.gov/cmip5/data_portal.html (last access: February 2018). NSIDC ice concentration and melt onset data can be downloaded at http://nsidc.org/data/NSIDC-0051 (last access: May 2017; Cavalieri et al., 1996) and http://nsidc.org/data/NSIDC-0105 (last access: March 2016; Anderson et al., 2011) respectively. PIOMAS ice thickness data can be downloaded at http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/data/ (last access: March 2016; Zhang and Rothrock, 2003). ERAI surface radiation data can be downloaded at http://apps.ecmwf.int/datasets/data/interim-full-daily/levtype=sfc/ (last access: September 2016; Dee et al., 2011). ISCCP-FD surface radiation data are available at https://isccp.giss.nasa.gov/projects/browse_fc.html (last access: October 2015; Zhang et al., 2004). CERES surface radiation data are available at https://climatedataguide.ucar.edu/climate-data/ceres-ebaf. (last access: August 2014; Loeb et al., 2009)A new framework is presented for analysing the proximate causes of model Arctic sea ice biases, demonstrated with the CMIP5 model HadGEM2-ES (Hadley Centre Global Environment Model version 2 - Earth System). In this framework the Arctic sea ice volume is treated as a consequence of the integrated surface energy balance, via the volume balance. A simple model allows the local dependence of the surface flux on specific model variables to be described as a function of time and space. When these are combined with reference datasets, it is possible to estimate the surface flux bias induced by the model bias in each variable. The method allows the role of the surface albedo and ice thickness-growth feedbacks in sea ice volume balance biases to be quantified along with the roles of model bias in variables not directly related to the sea ice volume. It shows biases in the HadGEM2-ES sea ice volume simulation to be due to a bias in spring surface melt onset date, partly countered by a bias in winter downwelling longwave radiation. The framework is applicable in principle to any model and has the potential to greatly improve understanding of the reasons for ensemble spread in the modelled sea ice state. A secondary finding is that observational uncertainty is the largest cause of uncertainty in the induced surface flux bias calculation.Joint UK BEIS/Defra Met Office Hadley Centre Climate ProgrammeEuropean Union Horizon 2020Natural Environment Research Council (NERC

Optimización de un radiómetro de banda ancha en el marco de la futura misión EarthCARE

Ponencia presentada en: III Congreso de la Asociación Española de Climatología “El agua y el clima”, celebrado en Palma de Mallorca del 16 al 19 de junio de 2002.[ES]La futura misión EarthCARE (Earth Clouds, Aerosols, and Radiation Explorer), planeada conjuntamente por las agencias espaciales europea y japonesa, tiene por objetivo la obtención de perfiles de nubes y aerosoles de modo global, con el fin de mejorar la parametrización en los modelos climáticos. Para mejorar esta parametrización es necesario que los cálculos derivados sean consistentes con el balance de radiación en el techo de la Atmósfera, medido por un radiómetro de banda ancha a bordo del satélite. Para obtener medidas precisas de este balance es necesario el uso de modelos angulares. Mostramos que estos modelos presentan un rendimiento dependiente de la geometría de observación, existiendo ciertos ángulos de observación que permiten obtener una medida más precisa del balance de radiación en el techo de la atmósfera.[EN]EarthCARE (Earth Clouds, Aerosols, and Radiation Explorer) is a future European and Japanese joint mission, with the objective of obtaining clouds and aerosols profiles at global scale in order to improve their parameterisations in climate models. To improve these parameterisations the computations have to be done in a radiatively consistent manner with the radiation budget at the top of the Atmosphere, measured by a broadband radiometer onboard the satellite. Angular models are needed so that this budget can be measured accurately. We show how the performance of these models depends on the viewing geometry, existing preferred observing angles, which allow obtaining more accurate top of Atmosphere Earth radiation budget measurements

El balance de radiación de onda corta en superficie a partir de medidas de satélite

Ponencia presentada en: II Congreso de la Asociación Española de Climatología “El tiempo del clima”, celebrado en Valencia del 7 al 9 de junio de 2001[ES]En este trabajo se presenta un cálculo del balance de radiación solar en superficie a partir de medidas realizadas con el sensor ScaRaB (Scanner for Radiation Budget) desde marzo de 1994 hasta febrero de 1995, lo que permite obtener una climatología anual desde una perspectiva global. Se muestra de esta forma la utilidad de los sensores de banda ancha a bordo de satélites para realizar un seguimiento del balance de radiación.[EN]In this paper the surface Shortwave radiation budget computed from ScaRaB (Scanner for Radiation Budget) is obtained, from March 1994 to February 1995. This allows us to obtain an annual global climatology and shows the utility of broad-band radiometers onboard satellites to monitor the earth radiation budget

Estudio de la relación entre los balances en superficie de onda larga y onda corta utilizando datos del proyecto SRB (Surface Radiation Budget)

Ponencia presentada en: III Congreso de la Asociación Española de Climatología “El agua y el clima”, celebrado en Palma de Mallorca del 16 al 19 de junio de 2002.[ES]En este trabajo se muestra la influencia de diferentes regímenes climáticos en el balance de radiación en superficie, a través de las comparaciones entre los balances de onda larga y onda corta en diferentes regiones del globo. Las regiones estudiadas son cuatro zonas desérticas o semidesérticas, seis oceánicas y dos localizadas en el Mediterráneo. Se observa una gran influencia de la cobertura nubosa en los balances de radiación de onda corta y larga, así como el efecto estacional en ambos hemisferios. Asimismo, aparecen diferencias claras si comparamos regiones del Mar Mediterráneo con regiones centrales del Océano Pacífico o el Atlántico.[EN]In this work we show the influence of different climatic regimes on the surface radiation balance through the comparisons between the long wave balance and the short wave balance over different regions in the globe. The studied regions are four deserted or semi-deserted areas, six ocean areas and two areas located in the Mediterranean basin. A large influence of cloud cover is observed in both short wave and long wave balances, as well as the seasonal effect in both hemispheres. Likewise, remarkable differences appear if we compare Mediterranean Sea regions with central regions of the Pacific or Atlantic Oceans

A Regime-Oriented Approach to Observationally Constraining Extratropical Shortwave Cloud Feedbacks

The extratropical shortwave (SW) cloud feedback is primarily due to increases in extratropical liquid cloud extent and optical depth. Here, we examine the response of extratropical (35°–75°) marine cloud liquid water path (LWP) to a uniform 4-K increase in sea surface temperature (SST) in global climate models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and variants of the HadGEM3-GC3.1 GCM. Compositing is used to partition data into periods inside and out of cyclones. The response of extratropical LWP to a uniform SST increase and associated atmospheric response varies substantially among GCMs, but the sensitivity of LWP to cloud controlling factors (CCFs) is qualitatively similar. When all other predictors are held constant, increasing moisture flux drives an increase in LWP. Increasing SST, holding all other predictors fixed, leads to a decrease in LWP. The combinations of these changes lead to LWP, and by extension reflected SW, increasing with warming in both hemispheres. Observations predict an increase in reflected SW over oceans of 0.8–1.6 W m−2 per kelvin SST increase (35°–75°N) and 1.2–1.9 W m−2 per kelvin SST increase (35°–75°S). This increase in reflected SW is mainly due to increased moisture convergence into cyclones because of increasing available moisture. The efficiency at which converging moisture is converted into precipitation determines the amount of liquid cloud. Thus, cyclone precipitation processes are critical to constraining extratropical cloud feedbacks

Large contribution of supercooled liquid clouds to the solar radiation budget of the Southern Ocean

The Southern Ocean is a critical region for global climate, yet large cloud and solar radiation biases over the Southern Ocean are a long-standing problem in climate models and are poorly understood, leading to biases in simulated sea surface temperatures. This study shows that supercooled liquid clouds are central to understanding and simulating the Southern Ocean environment. A combination of satellite observational data and detailed radiative transfer calculations is used to quantify the impact of cloud phase and cloud vertical structure on the reflected solar radiation in the Southern Hemisphere summer. It is found that clouds with supercooled liquid tops dominate the population of liquid clouds. The observations show that clouds with supercooled liquid tops contribute between 27% and 38% to the total reflected solar radiation between 40° and 70°S, and climate models are found to poorly simulate these clouds. The results quantify the importance of supercooled liquid clouds in the Southern Ocean environment and highlight the need to improve understanding of the physical processes that control these clouds in order to improve their simulation in numerical models. This is not only important for improving the simulation of present-day climate and climate variability, but also relevant for increasing confidence in climate feedback processes and future climate projections

Evaluation of a General Circulation Model by the CERES Flux-By-Cloud Type Simulator

In this work, we use the Clouds and the Earths Radiant Energy System (CERES) FluxByCloudTyp data product, which calculates TOA shortwave and longwave fluxes for cloud categories defined by cloud optical depth () and cloud top pressure (), to evaluate the HadGEM2-A model with a simulator. The CERES Flux-by-cloud type simulator is comprised of a cloud generator that produces subcolumns with profiles of binary cloud fraction, a cloud property simulator that determines the (,) cloud type for each subcolumn, and a radiative transfer model that calculates TOA fluxes. The identification of duplicate atmospheric profiles reduces the number of radiative transfer calculations required by approximately 97.6%. In the Southern Great Plains region in JFD (January, February, and December) 2008, the simulator shows that simulated cloud tops are higher in altitude than observed, but also have higher values of OLR than observed, leading to a compensating error that results in an average value of OLR that is close to observed. When the simulator is applied to the Southeast Pacific stratocumulus region in JJA 2008, the simulated cloud tops are primarily low in altitude; however, the clouds tend to be less numerous, and have higher optical depths than are observed. In addition to the increase in albedo that comes from having too many clouds with higher optical depth, the HadGEM2-A albedo is higher than observed for those cloud types that occur most frequently. The simulator is also applied to the entire 60 N 60 S region, and it is found that there are fewer clouds than observed for most cloud types, but there are also higher albedos for most cloud types, which represents a compensating error in terms of the shortwave radiative budget

An evaluation of clouds and precipitation in convection-permitting forecasts for South Africa

Since 2016, the South African Weather Service (SAWS) has been running convective-scale simulations to assist with forecast operations across southern Africa. These simulations are run with a tropical configuration of the Met Office Unified Model (UM), nested in the Met Office global model, but without data assimilation. For November 2016, convection-permitting simulations at 4.4-km and 1.5-km grid length are compared against a simulation at 10-km grid length with convection parametrization (the current UM global atmosphere configuration) to identify the benefits of increasing model resolution for forecasting convection across southern Africa. The simulations are evaluated against satellite rainfall estimates, CloudSat vertical cloud profiles, and SAWS radar data. In line with previous studies using the UM, on a monthly time scale, the diurnal cycle of convection and the distribution of rainfall rates compare better against observations when convection-permitting model configurations are used. The SAWS radar network provides a three-dimensional composite of radar reflectivity for northeast South Africa at 6-minute intervals, allowing the evaluation of the vertical development of precipitating clouds and of the timing of the onset of deep convection. Analysis of four case study days indicates that the 4.4-km simulations have a later onset of convection than the 1.5-km simulations, but there is no consistent bias of the simulations against the radar observations across the case studies

Can reducing the incoming energy flux over the Southern Ocean in a CGCM improve its simulation of tropical climate?

Atmosphere-ocean general circulation models (CGCMs) show important systematic errors. Simulated precipitation in the tropics is generally overestimated over the oceans south of the equator, and stratocumulus (SCu) clouds are underestimated above too warm sea surface temperatures (SSTs). In the extratropics, SSTs are also too warm over the Southern Ocean. We argue that ameliorating these extratropical errors in a CGCM can result in an improved model's performance in the tropics depending upon the success in simulating the sensitivity of SCu to underlying SST. Our arguments are supported by the very different response obtained with two CGCMs to an idealized reduction of solar radiation flux incident at the top of the atmosphere over the Southern Ocean. It is shown that local perturbation impacts are very similar in the two models but that SST reductions in the SCu regions of the southern subtropics are stronger in the model with the stronger SCu-SST feedbacks.NOAA's Climate Program Office, Climate Variability and Predictability Program Award. Grant Number: NA14OAR4310278. European Union Seventh Framework Programme. Grant Numbers: FP7/2007–2013, 60352Peer reviewe