Search results for "Shortwave"

Prototyping Sentinel-2 green LAI and brown LAI products for cropland monitoring.

2022

Abstract For agricultural applications, identification of non-photosynthetic above-ground vegetation is of great interest as it contributes to assess harvest practices, detecting crop residues or drought events, as well as to better predict the carbon, water and nutrients uptake. While the mapping of green Leaf Area Index (LAI) is well established, current operational retrieval models are not calibrated for LAI estimation over senescent, brown vegetation. This not only leads to an underestimation of LAI when crops are ripening, but is also a missed monitoring opportunity. The high spatial and temporal resolution of Sentinel-2 (S2) satellites constellation offers the possibility to estimate …

Errors and uncertainties introduced by a regional climate model in climate impact assessments: example of crop yield simulations in West Africa

2015

16 pages; International audience; The challenge of estimating the potential impacts of climate change has led to an increasing use of dynamical downscaling to produce fine spatial-scale climate projections for impact assessments. In this work, we analyze if and to what extent the bias in the simulated crop yield can be reduced by using the Weather Research and Forecasting (WRF) regional climate model to downscale ERA-Interim (European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis) rainfall and radiation data. Then, we evaluate the uncertainties resulting from both the choice of the physical parameterizations of the WRF model and its internal variability. Impact assessments w…

Air traffic and contrail changes during COVID-19 over Europe: A model study

2021

The strong reduction of air traffic during the COVID-19 pandemic provides a test case for the relation between air traffic density, contrails, and their radiative forcing of climate change. Air traffic and contrail cirrus changes are quantified for a European domain for March to August 2020 and compared to the same period in 2019. Traffic data show a 72 % reduction in flight distance compared with 2019. This paper investigates the induced contrail changes in a model study. The contrail model results depend on various methodological details tested in parameter studies. In the reference case, the reduced traffic caused an even stronger reduction in contrail length, partly because the w…

Comparison of top of the atmosphere GERB measured radiances with independent radiative transfer simulations obtained at the Valencia Anchor Station a…

2005

The purpose of this work is to compare top of the atmosphere (TOA) radiances as measured by the Geostationary Earth Radiation Budget (GERB) instrument on board the METEOSAT-8 (METEOSAT Second Generation) satellite to equivalent independent radiances obtained from radiative transfer simulations performed using surface and atmospheric measured parameters gathered during the GERB Surface Ground Validation Campaign at the Valencia Anchor Station (VAS) reference area in February 2004. In this paper we try to extend the methodology previously developed and tested for the NASA Clouds and the Earth's Radiant Energy System (CERES) instrument in the framework of the SEVIRI and GERB Cal/val Area for L…

2021

Abstract. The strong reduction of air traffic during the COVID-19 pandemic provides a unique test case for the relationship between air traffic density, contrails, and their radiative forcing of climate change. Here, air traffic and contrail cirrus changes are quantified for a European domain for March to August 2020 and compared to the same period in 2019. Traffic data show a 72 % reduction in flight distance compared with 2019. This paper investigates the induced contrail changes in a model study. The contrail model results depend on various methodological details as discussed in parameter studies. In the reference case, the reduced traffic caused a reduction in contrail length. The reduc…

Heating rate profiles and radiative forcing due to a dust storm in the Western Mediterranean using satellite observations

2017

Abstract We analyze the vertically-resolved radiative impact due to a dust storm in the Western Mediterranean. The dust plume travels around 3–5 km altitude and the aerosol optical depth derived by MODIS at 550 nm ranges from 0.33 to 0.52 at the overpass time (13:05 UT). The aerosol radiative forcing (ARF), forcing efficiency (FE) and heating rate profile (AHR) are determined throughout the dust trajectory in shortwave (SW) and longwave (LW) ranges. To do this, we integrate different satellite observations (CALIPSO and MODIS) and detailed radiative transfer modeling. The combined (SW + LW) effect of the dust event induces a net cooling in the studied region. On average, the FE at 22.4° sola…

Aviation Contrail Cirrus and Radiative Forcing Over Europe During 6 Months of COVID‐19

2021

Abstract The COVID‐19 pandemic led to a 72% reduction of air traffic over Europe in March–August 2020 compared to 2019. Modeled contrail cover declined similarly, and computed mean instantaneous radiative contrail forcing dropped regionally by up to 0.7 W m−2. Here, model predictions of cirrus optical thickness and the top‐of‐atmosphere outgoing longwave and reflected shortwave irradiances are tested by comparison to Meteosat‐SEVIRI‐derived data. The agreement between observations and modeled data is slightly better when modeled contrail cirrus contributions are included. The spatial distributions and diurnal cycles of the differences in these data between 2019 and 2020 are partially caused…

Influence of the Laurentian Great Lakes on Regional Climate*

2013

Abstract The influence of the Laurentian Great Lakes on climate is assessed by comparing two decade-long simulations, with the lakes either included or excluded, using the Abdus Salam International Centre for Theoretical Physics Regional Climate Model, version 4. The Great Lakes dampen the variability in near-surface air temperature across the surrounding region while reducing the amplitude of the diurnal cycle and annual cycle of air temperature. The impacts of the Great Lakes on the regional surface energy budget include an increase (decrease) in turbulent fluxes during the cold (warm) season and an increase in surface downward shortwave radiation flux during summer due to diminished atmo…

Spatiotemporal modeling and prediction of solar radiation

2003

[1] The radiation budget in the Earth-atmosphere system is what drives Earth's climate, and thus measurements of this balance are needed to improve our knowledge of Earth's climate and climate change. In the present paper we focus on the analysis of the surface shortwave radiation budget (SSRB), which is the amount of energy in the solar region of the electromagnetic spectrum (0.2–4.0 μm) absorbed at the surface. The SSRB has to be modeled from the surface to the top of the atmosphere, jointly with information about the state of the atmosphere and the surface. These data come from satellites orbiting the Earth and are often missing or disturbed. Its interest is not only at global scales; ra…

The surface shortwave net flux from the scanner for radiation budget (SCARAB)

2002

Abstract Shortwave surface net radiation is usually determined by combining the measurement of insolation with an independent estimate of surface albedo. However, uncertainties associated with each of these quantities may lead to large errors in the value of net surface solar radiation. An alternative approach is to deduce the net solar flux (the term flux is used here as the radiometric quantity flux density) at the surface directly from the budget at the top of the atmosphere, without explicit knowledge of surface albedo. The Satellite Application Facility on Climate Monitoring is a joint project of the German Meteorological Service and other European Meteorological Services dedicated to …