L. Gonzalez

Bio: L. Gonzalez is an academic researcher from Royal Meteorological Institute. The author has contributed to research in topics: Geostationary Earth Radiation Budget & Geostationary orbit. The author has an hindex of 8, co-authored 21 publications receiving 444 citations.

The Geostationary Earth Radiation Budget Project

Abstract: This paper reports on a new satellite sensor, the Geostationary Earth Radiation Budget (GERB) experiment. GERB is designed to make the first measurements of the Earth's radiation budget from geostationary orbit. Measurements at high absolute accuracy of the reflected sunlight from the Earth, and the thermal radiation emitted by the Earth are made every 15 min, with a spatial resolution at the subsatellite point of 44.6 km (north–south) by 39.3 km (east–west). With knowledge of the incoming solar constant, this gives the primary forcing and response components of the top-of-atmosphere radiation. The first GERB instrument is an instrument of opportunity on Meteosat-8, a new spin-stabilized spacecraft platform also carrying the Spinning Enhanced Visible and Infrared (SEVIRI) sensor, which is currently positioned over the equator at 3.5°W. This overview of the project includes a description of the instrument design and its preflight and in-flight calibration. An evaluation of the instrument performan...

Pixel‐scale composite top‐of‐the‐atmosphere clear‐sky reflectances for Meteosat‐7 visible data

Abstract: [1] A new method to estimate composite top of the atmosphere (TOA) visible clear-sky reflectances for wide narrow band geostationary satellites such as the Meteosat constellation is presented. This method relies on some a priori knowledge of angular variations of TOA broadband reflectances associated with clear-sky conditions above mean surface types through the use of the clear-sky Cloud and the Earth's Radiant Energy System (CERES) shortwave broadband angular dependency models (ADMs). Each pixel (or Earth location) viewed from such geostationary imager at a given daytime is associated with a reflectance time series made up of its chronological daily measurements. This time series can be seen as a clear-sky visible narrow band reflectance curve of the associated pixel surface plus an additive random noise modeling cloudy conditions above it. On the basis of this assumption, TOA clear-sky broadband reflectances extracted from the CERES ADMs are used to compute curve-driven fifth percentiles on these time series in order to estimate the TOA clear-sky visible narrow band reflectance curves for all pixels, while the percentile approach exhibits only a reduced sensitivity to cloud shadows. Benefits of our method are discussed with respect to its application to 7 months of Meteosat-7 daytime visible narrow band measurements. Finally, the performance of our algorithm is assessed through comparisons with its predicted and associated International Cloud Climatology Project DX clear-sky values with respect to a visually generated clear-sky pixels database.

Global dimming and brightening: A review

Abstract: [1] There is increasing evidence that the amount of solar radiation incident at the Earth's surface is not stable over the years but undergoes significant decadal variations. Here I review the evidence for these changes, their magnitude, their possible causes, their representation in climate models, and their potential implications for climate change. The various studies analyzing long-term records of surface radiation measurements suggest a widespread decrease in surface solar radiation between the 1950s and 1980s (“global dimming”), with a partial recovery more recently at many locations (“brightening”). There are also some indications for an “early brightening” in the first part of the 20th century. These variations are in line with independent long-term observations of sunshine duration, diurnal temperature range, pan evaporation, and, more recently, satellite-derived estimates, which add credibility to the existence of these changes and their larger-scale significance. Current climate models, in general, tend to simulate these decadal variations to a much lesser degree. The origins of these variations are internal to the Earth's atmosphere and not externally forced by the Sun. Variations are not only found under cloudy but also under cloud-free atmospheres, indicative of an anthropogenic contribution through changes in aerosol emissions governed by economic developments and air pollution regulations. The relative importance of aerosols, clouds, and aerosol-cloud interactions may differ depending on region and pollution level. Highlighted are further potential implications of dimming and brightening for climate change, which may affect global warming, the components and intensity of the hydrological cycle, the carbon cycle, and the cryosphere among other climate elements.

Toward Optimal Closure of the Earth's Top-of-Atmosphere Radiation Budget

Abstract: Despite recent improvements in satellite instrument calibration and the algorithms used to determine reflected solar (SW) and emitted thermal (LW) top-of-atmosphere (TOA) radiative fluxes, a sizeable imbalance persists in the average global net radiation at the TOA from satellite observations. This imbalance is problematic in applications that use earth radiation budget (ERB) data for climate model evaluation, estimate the earth’s annual global mean energy budget, and in studies that infer meridional heat transports. This study provides a detailed error analysis of TOA fluxes based on the latest generation of Clouds and the Earth’s Radiant Energy System (CERES) gridded monthly mean data products [the monthly TOA/surface averages geostationary (SRBAVG-GEO)] and uses an objective constrainment algorithm to adjust SW and LW TOA fluxes within their range of uncertainty to remove the inconsistency between average global net TOA flux and heat storage in the earth–atmosphere system. The 5-yr global mean...

The EarthCARE Satellite: The Next Step Forward in Global Measurements of Clouds, Aerosols, Precipitation, and Radiation

Abstract: The collective representation within global models of aerosol, cloud, precipitation, and their radiative properties remains unsatisfactory. They constitute the largest source of uncertainty in predictions of climatic change and hamper the ability of numerical weather prediction models to forecast high-impact weather events. The joint ESA-JAXA EarthCARE satellite mission, scheduled for launch in 2017, will help to resolve these weaknesses by providing global profiles of cloud, aerosol, precipitation, and associated radiative properties inferred from a combination of measurements made by its collocated active and passive sensors. EarthCARE will improve our understanding of cloud and aerosol processes by extending the invaluable dataset acquired by the A-Train satellites CloudSat, CALIPSO, and Aqua. Specifically, EarthCARE's Cloud Profling Radar, with 7 dB more sensitivity than CloudSat, will detect more thin clouds and its Doppler capability will provide novel information on convection, precipitating ice particle and raindrop fall speeds. EarthCARE's 355-nm High Spectral Resolution Lidar will measure directly and accurately cloud and aerosol extinction and optical depth. Combining this with backscatter and polarization information should lead to an unprecedented ability to identify aerosol type. The Multi-Spectral Imager will provide a context for, and the ability to construct the cloud and aerosol distribution in 3D domains around the narrow 2D retrieved cross-section. The consistency of the retrievals will be assessed to within a target of ±10 W m−2 on the (10 km2) scale by comparing the multi-view Broad-Band Radiometer observations to the top-of-atmosphere fluxes estimated by 3D radiative transfer models acting on retrieved 3D domains.

Geostationary Enhanced Temporal Interpolation for CERES Flux Products

Abstract: The Clouds and the Earth's Radiant Energy System (CERES) instruments on board the Terra and Aqua spacecraft continue to provide an unprecedented global climate record of the earth's top-of-atmosphere (TOA) energy budget since March 2000. A critical step in determining accurate daily averaged flux involves estimating the flux between CERES Terra or Aqua overpass times. CERES employs the CERES-only (CO) and the CERES geostationary (CG) temporal interpolation methods. The CO method assumes that the cloud properties at the time of the CERES observation remain constant and that it only accounts for changes in albedo with solar zenith angle and diurnal land heating, by assuming a shape for unresolved changes in the diurnal cycle. The CG method enhances the CERES data by explicitly accounting for changes in cloud and radiation between CERES observation times using 3-hourly imager data from five geostationary (GEO) satellites. To maintain calibration traceability, GEO radiances are calibrated against Moderate Resolution Imaging Spectroradiometer (MODIS) and the derived GEO fluxes are normalized to the CERES measurements. While the regional (1 deg latitude x 1 deg longitude) monthly-mean difference between the CG and CO methods can exceed 25 W m(sub -2) over marine stratus and land convection, these regional biases nearly cancel in the global mean. The regional monthly CG shortwave (SW) and longwave (LW) flux uncertainty is reduced by 20%, whereas the daily uncertainty is reduced by 50% and 20%, respectively, over the CO method, based on comparisons with 15-min Geostationary Earth Radiation Budget (GERB) data.