scholarly journals A Revised Cloud Overlap Scheme for Fast Microwave Radiative Transfer in Rain and Cloud

2009 ◽  
Vol 48 (11) ◽  
pp. 2257-2270 ◽  
Author(s):  
Alan J. Geer ◽  
Peter Bauer ◽  
Christopher W. O’Dell
Keyword(s):  
Radiative Transfer ◽  
Weather Forecasting ◽  
Cloud Fraction ◽  
New Approach ◽  
Microwave Frequencies ◽  
Weather Forecasts ◽  
Clear Sky ◽  
Atmospheric Profile ◽  
Microwave Imager ◽  
Weighted Combination

Abstract The assimilation of cloud- and precipitation-affected observations into weather forecasting systems requires very fast calculations of radiative transfer in the presence of multiple scattering. At the European Centre for Medium-Range Weather Forecasts (ECMWF), performance limitations mean that only a single cloudy calculation (including any precipitation) can be made, and the simulated radiance is a weighted combination of cloudy- and clear-sky radiances. Originally, the weight given to the cloudy part was the maximum cloud fraction in the atmospheric profile. However, this weighting was excessive, and because of nonlinear radiative transfer (the “beamfilling effect”) there were biases in areas of cloud and precipitation. A new approach instead uses the profile average cloud fraction, and decreases RMS errors by 40% in areas of rain or heavy clouds when “truth” comes from multiple independent column simulations. There is improvement all the way from low (e.g., 19 GHz) to high (e.g., 183 GHz) microwave frequencies. There is also improvement when truth comes from microwave imager observations. One minor problem is that biases increase slightly in mid- and upper-tropospheric sounding channels in light-cloud situations, which shows that future improvements will require the cloud fraction to vary according to the optical properties at different frequencies.

scholarly journals Multi-sensor analyses of the skin temperature for the assimilation of satellite radiances in the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS, cycle 47R1)

2021 ◽  
Author(s):  
Sebastien Massart ◽  
Niels Bormann ◽  
Massimo Bonavita ◽  
Cristina Lupu
Keyword(s):  
Skin Temperature ◽  
Control Variable ◽  
Two Dimensional ◽  
New Approach ◽  
Weather Forecasts ◽  
Observation Operator ◽  
Clear Sky ◽  
European Centre ◽  
Medium Range ◽  
Atmospheric Variables

Abstract. The assimilation of clear-sky radiance in the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric analysis relies on the clear-sky radiances observation operator. Some of these radiances have frequencies that make them sensitive to both the surface and atmosphere. Because the atmospheric and surface analyses are currently not strongly coupled, a specific treatment of the surface is required. The observation operator expects in particular, a skin temperature value at the observation location and time, together with the profiles of the atmospheric variables along the viewing path. This skin temperature is added to the control variable and optimised simultaneously with all the atmospheric variables to produce optimal simulated radiances.We present two approaches to add the skin temperature to the control variable. In the current TOVSCV approach, a series of skin temperature value per observation location is added to the control variable. Effectively, in the optimisation process, the skin temperature acts as a sink variable in observation space and is uncoupled from the skin temperature at other locations. In the novel SKTACV approach, two-dimensional skin temperature fields are added to the control variable. All clear-sky radiances then participate in the optimisation of these two-dimensional fields and the analysis produces temporally and spatially consistent skin temperature fields.We compare the two approaches over two seasons of three months each. Overall, there is a neutral impact of the new approach on the analysis and forecast. Besides, there are some evidences that the contribution of the sub-surface layers should be represented in the new approach for the skin temperature associated with the microwave instruments.

scholarly journals Multi-sensor analyses of the skin temperature for the assimilation of satellite radiances in the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS, cycle 47R1)

2021 ◽  
Vol 14 (9) ◽  
pp. 5467-5485
Author(s):  
Sebastien Massart ◽  
Niels Bormann ◽  
Massimo Bonavita ◽  
Cristina Lupu
Keyword(s):  
Skin Temperature ◽  
Control Variable ◽  
Temperature Fields ◽  
Two Dimensional ◽  
New Approach ◽  
Weather Forecasts ◽  
Observation Operator ◽  
Clear Sky ◽  
Medium Range ◽  
Atmospheric Variables

Abstract. The assimilation of clear-sky radiance in the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric analysis relies on the clear-sky radiances observation operator. Some of these radiances have frequencies that make them sensitive to both the surface and atmosphere. Because the atmospheric and surface analyses are currently not strongly coupled, a specific treatment of the surface is required. The observation operator specifically expects a skin temperature value at the observation location and time as well as the profiles of the atmospheric variables along the viewing path. This skin temperature is added to the control variable and optimised simultaneously with all of the atmospheric variables to produce optimal simulated radiances. We present two approaches to add the skin temperature to the control variable. In the current TOVS Control Variable (TOVSCV) approach, a series of skin temperature values per observation location is added to the control variable. Effectively, in the optimisation process, the skin temperature acts as a sink variable in observation space and is uncoupled from the skin temperature at other locations. In the novel SKin Temperature in the Extended Control Vector (SKTECV) approach, two-dimensional skin temperature fields are added to the control variable. All clear-sky radiances then participate in the optimisation of these two-dimensional fields, and the analysis produces temporally and spatially consistent skin temperature fields. We compare the two approaches over two seasons of 3 months each. Overall, there is a neutral impact of the new approach on the analysis and forecast. Moreover, there is some evidence that the contribution of the subsurface layers should be represented in the new approach for the skin temperature associated with the microwave instruments.

scholarly journals Three-dimensional visualization of ensemble weather forecasts – Part 2: Forecasting warm conveyor belt situations for aircraft-based field campaigns

2015 ◽  
Vol 8 (7) ◽  
pp. 2355-2377 ◽  
Author(s):  
M. Rautenhaus ◽  
C. M. Grams ◽  
A. Schäfler ◽  
R. Westermann
Keyword(s):  
System Integration ◽  
Visual Analysis ◽  
Weather Forecasting ◽  
Three Dimensional ◽  
Conveyor Belt ◽  
Ensemble Prediction ◽  
Wind Fields ◽  
Uncertainty Visualization ◽  
Ensemble Prediction System ◽  
Weather Forecasts

Abstract. We present the application of interactive three-dimensional (3-D) visualization of ensemble weather predictions to forecasting warm conveyor belt situations during aircraft-based atmospheric research campaigns. Motivated by forecast requirements of the T-NAWDEX-Falcon 2012 (THORPEX – North Atlantic Waveguide and Downstream Impact Experiment) campaign, a method to predict 3-D probabilities of the spatial occurrence of warm conveyor belts (WCBs) has been developed. Probabilities are derived from Lagrangian particle trajectories computed on the forecast wind fields of the European Centre for Medium Range Weather Forecasts (ECMWF) ensemble prediction system. Integration of the method into the 3-D ensemble visualization tool Met.3D, introduced in the first part of this study, facilitates interactive visualization of WCB features and derived probabilities in the context of the ECMWF ensemble forecast. We investigate the sensitivity of the method with respect to trajectory seeding and grid spacing of the forecast wind field. Furthermore, we propose a visual analysis method to quantitatively analyse the contribution of ensemble members to a probability region and, thus, to assist the forecaster in interpreting the obtained probabilities. A case study, revisiting a forecast case from T-NAWDEX-Falcon, illustrates the practical application of Met.3D and demonstrates the use of 3-D and uncertainty visualization for weather forecasting and for planning flight routes in the medium forecast range (3 to 7 days before take-off).

scholarly journals Aerosol direct radiative forcing during Sahara dust intrusions in the Central Mediterranean

2010 ◽  
Vol 10 (8) ◽  
pp. 20673-20727
Author(s):  
M. R. Perrone ◽  
A. Bergamo ◽  
V. Bellantone
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
Spectral Range ◽  
Mediterranean Basin ◽  
Transfer Model ◽  
Clear Sky ◽  
Fine Mode ◽  
The Mediterranean ◽  
The Mediterranean Basin ◽  
Sahara Dust

Abstract. The clear-sky, instantaneous Direct Radiative Effect (DRE) by all and anthropogenic particles is calculated during Sahara dust intrusions in the Mediterranean basin, to evaluate the role of anthropogenic particle's radiative effects and to obtain a better estimate of the DRE by desert dust. The clear-sky aerosol DRE is calculated by a two stream radiative transfer model in the solar (0.3–4 μm) and infrared (4–200 μm) spectral range, at the top of the atmosphere (ToA) and at the Earth's surface (sfc). Aerosol optical properties by AERONET sun-sky photometer measurements and aerosol vertical profiles by EARLINET lidar measurements, both performed at Lecce (40.33° N, 18.10° E) during Sahara dust intrusions occurred from 2003 to 2006 year, are used to perform radiative transfer simulations. Instantaneous values at 0.44 μm of the real (n) and imaginary (k) refractive index and of the of aerosol optical depth (AOD) vary within the 1.33–1.55, 0.0037–0.014, and 0.2–0.7 range, respectively during the analyzed dust outbreaks. Fine mode particles contribute from 34% to 85% to the AOD by all particles. The complex atmospheric chemistry of the Mediterranean basin that is also influenced by regional and long-range transported emissions from continental Europe and the dependence of dust optical properties on soil properties of source regions and transport pathways, are responsible for the high variability of n, k, and AOD values and of the fine mode particle contribution. Instantaneous all-wave (solar+infrared) DREs that are negative as a consequence of the cooling effect by aerosol particles, span the – (32–10) Wm−2 and the – (44–20) Wm−2 range at the ToA and surface, respectively. The instantaneous all-wave DRE by anthropogenic particles that is negative, varies within – (13–7) Wm−2 and – (18–11) Wm−2 at the ToA and surface, respectively. It represents from 41% up to 89% and from 32% up to 67% of the all-wave DRE by all particles at the ToA and surface, respectively during the analysed dust outbreaks. A linear relationship to calculate the DRE by natural particles in the solar and infrared spectral range is provided.

A new approach to the real-time assessment and intraday forecasting of clear-sky direct normal irradiance

Solar Energy ◽  
2018 ◽  
Vol 167 ◽  
pp. 35-51 ◽  
Author(s):  
Rémi Chauvin ◽  
Julien Nou ◽  
Julien Eynard ◽  
Stéphane Thil ◽  
Stéphane Grieu
Keyword(s):  
Real Time ◽  
New Approach ◽  
The Real ◽  
Clear Sky ◽  
Direct Normal Irradiance ◽  
Time Assessment

D Minus Months: Strategic Planning for Weather-Sensitive Decisions

2021 ◽  
Author(s):  
Eva D. Regnier ◽  
Joel W. Feldmeier
Keyword(s):  
Decision Making ◽  
Decision Analysis ◽  
Weather Forecasting ◽  
Decision Makers ◽  
Strategic Decisions ◽  
Sequential Decisions ◽  
Weather Forecasts ◽  
Current State ◽  
Set Up ◽  
Made In

General Eisenhower’s decisions to postpone and, one day later, to launch the “D-Day” invasion of Normandy are a gripping illustration of sequential decisions under uncertainty, suitable for any introductory decision analysis class. They’re also the archetypal example of weather-sensitive decision making using a forecast. This paper develops a framework for analyzing weather-sensitive decisions with a focus on the less-familiar strategic decisions that determine how forecasts are produced and what operational alternatives are available so that decision makers can extract value from forecasts. We tell the story of the decisions made in the months before D-Day regarding how to set up the forecasting process and the myriad decisions implicating nation-level resources that prepared Allied forces not just to invade, but to hold open that decision until the last possible hour so that Eisenhower and his staff could use the critical forecasts. Finally, we overview the current state of the weather-forecasting enterprise, the current challenges of interest to decision analysts, and what this means for decision analysts seeking opportunities to help the weather enterprise improve forecasts and to help operational decision makers extract more value from modern weather forecasts.

Polar  Stratospheric Clouds detection at Belgrano II Antarctic station from DOAS measurements

2021 ◽  
Author(s):  
Laura Gómez Martín ◽  
Daniel Toledo ◽  
Margarita Yela ◽  
Cristina Prados-Román ◽  
José Antonio Adame ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Color Index ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Meteorological Model ◽  
Weather Forecasts ◽  
Stratospheric Temperature ◽  
Stratospheric Clouds

<p><span>Ground-based zenith DOAS (Differential Optical Absorption Spectroscopy) measurements have been used to detect and estimate the altitude of PSCs over Belgrano II Antarctic station during the polar sunrise seasons of 2018 and 2019. The method used in this work studies the evolution of the color index (CI) during twilights. The CI has been defined here as the ratio of the recorded signal at 520 and 420 nm. In the presence of PSCs, the CI shows a maximum at a given solar zenith angle (SZA). The value of such SZA depends on the altitude of the PSC. By using a spherical Monte Carlo radiative transfer model (RTM), the method has been validated and a function relating the SZA of the CI maximum and the PSC altitude has been calculated. Model simulations also show that PSCs can be detected and their altitude can be estimated even in presence of optically thin tropospheric clouds or aerosols. Our results are in good agreement with the stratospheric temperature evolution obtained through the ERA5 data reanalysis from the global meteorological model ECMWF (European Centre for Medium Range Weather Forecasts) and the PSCs observations from CALIPSO (Cloud-Aerosol-Lidar and Infrared Pathfinder Satellite Observations).</span></p><p><span>The methodology used in this work could also be applied to foreseen and/or historical measurements obtained with ground-based spectrometers such e. g. the DOAS instruments dedicated to trace gas observation in Arctic and Antarctic sites. This would also allow to investigate the presence and long-term evolution of PSCs.</span></p><p><span><strong>Keywords: </strong>Polar stratospheric clouds; color index; radiative transfer model; visible spectroscopy.</span></p>

scholarly journals Concordance Modeling With a Gold Standard for Variables From the Three-Parameter Gamma Distribution

2020 ◽  
Vol 8 (2) ◽  
pp. 284
Author(s):  
Márcio Paulo de Oliveira ◽  
Miguel Angel Uribe-Opazo ◽  
Manuel Galea ◽  
Jerry Adriani Johann
Keyword(s):  
Gamma Distribution ◽  
Gold Standard ◽  
Weather Forecasting ◽  
Geographical Location ◽  
Random Variable ◽  
Climatic Data ◽  
Weather Forecasts ◽  
Rainfall Forecast ◽  
Environmental Prediction ◽  
Range Interval

A way to compare two or more measurements for the same random variable can be achieved by using a negligible error reference measurement, which is called the gold standard, obtained by consolidated measurement methods. This paper presents a new methodology for comparing measurements in the presence of a gold standard with random variables from the multivariate three-parameter (shape, scale, and location) gamma distribution. The errors between gold standard measures and approximate measures have a gamma difference distribution with the same three parameters of the gamma distribution. The concordance measurements were obtained by mean of a coefficient, which measures the degree of agreement as a ratio between the variances of the gold standard and the errors. The developed methodology is illustrated with climatic data which is divided into four ranges. The measurements analyzed are rainfall forecasts of the following four national centers: Canadian Meteorological Center (CMC), European Center for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and Center for Weather Forecasting and Climate Studies (CPTEC). The forecast range was 240 hours for the West mesoregion of Paraná – Brazil, and in the October 1–March 31 period of the 2010/2011 –2015/2016 harvest years. The period was selected because it is related to soybean crop development in the region and because several crop estimation models use rainfall forecast data in this period. The methodology applied spatially indicated the center to be selected in each geographical location according to each rainfall range interval. The gamma model fit well with the data and is an alternative to the normal one for modelling rainfall, in particular to estimate concordances between rainfall forecasts and the gold standard, which are used to improve the selection of rainfall forecast centers.

scholarly journals From heliophysics to space weather forecasts

2019 ◽  
Vol 60 (5) ◽  
pp. 5.26-5.30
Author(s):  
Richard Harrison ◽  
Jackie Davies ◽  
Jonny Rae
Keyword(s):  
Space Weather ◽  
Weather Forecasting ◽  
Weather Forecasts ◽  
Space Weather Forecasting ◽  
New Space ◽  
The Subject

Abstract Richard Harrison, Jackie Davies and Jonny Rae summarize progress in capitalizing on UK expertise in research and instrumentation for new space weather forecasting – the subject of an RAS Discussion Meeting in March.

scholarly journals 100 Years of Progress in Understanding the Stratosphere and Mesosphere

2019 ◽  
Vol 59 ◽  
pp. 27.1-27.62 ◽  
Author(s):  
Mark P. Baldwin ◽  
Thomas Birner ◽  
Guy Brasseur ◽  
John Burrows ◽  
Neal Butchart ◽  
...  
Keyword(s):  
General Circulation ◽  
Weather Forecasting ◽  
Ozone Layer ◽  
Quasi Biennial Oscillation ◽  
Future Evolution ◽  
Weather Forecasts ◽  
The 1960S ◽  
Weather Impacts ◽  
Atmospheric Mass

Abstract The stratosphere contains ~17% of Earth’s atmospheric mass, but its existence was unknown until 1902. In the following decades our knowledge grew gradually as more observations of the stratosphere were made. In 1913 the ozone layer, which protects life from harmful ultraviolet radiation, was discovered. From ozone and water vapor observations, a first basic idea of a stratospheric general circulation was put forward. Since the 1950s our knowledge of the stratosphere and mesosphere has expanded rapidly, and the importance of this region in the climate system has become clear. With more observations, several new stratospheric phenomena have been discovered: the quasi-biennial oscillation, sudden stratospheric warmings, the Southern Hemisphere ozone hole, and surface weather impacts of stratospheric variability. None of these phenomena were anticipated by theory. Advances in theory have more often than not been prompted by unexplained phenomena seen in new stratospheric observations. From the 1960s onward, the importance of dynamical processes and the coupled stratosphere–troposphere circulation was realized. Since approximately 2000, better representations of the stratosphere—and even the mesosphere—have been included in climate and weather forecasting models. We now know that in order to produce accurate seasonal weather forecasts, and to predict long-term changes in climate and the future evolution of the ozone layer, models with a well-resolved stratosphere with realistic dynamics and chemistry are necessary.

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