Object-Based Metrics for Forecast Verification of Convective Development with Geostationary Satellite Data

Object-based metrics are adapted and applied to geostationary satellite observations with the evaluation of cloud forecasts in convective situations as the goal. Forecasts of the convection-permitting German-focused Consortium for Small-Scale Modeling (COSMO-DE) numerical model are transformed into synthetic observations using the RTTOV radiative transfer model, and contrasted with the corresponding real observations. Threshold-based segmentation techniques are applied to the fields for object identification. The statistical properties of the traditional measures cold cloud cover and average brightness temperature amplitude are contrasted to object-based metrics of spatial aggregation and object structure. Based on 59 case days from the summer half-years between 2012 and 2014, a variance decomposition technique is applied to the time series of the metrics to identify deficits in day-to-day, diurnal, and weather-regime-related variability of cold cloud characteristics in the forecasts. Furthermore, sensitivities of the considered metrics are discussed, which result from uncertainties in the satellite forward operator and from the choice of parameters in the object identification techniques.

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Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-6-527-2013 ◽

2013 ◽

Vol 6 (3) ◽

pp. 527-537 ◽

Cited By ~ 9

Author(s):

E. Jäkel ◽

M. Wendisch ◽

B. Mayer

Keyword(s):

Optical Depth ◽

Surface Albedo ◽

Radiative Transfer Model ◽

Small Scale ◽

Mean Deviation ◽

Transfer Model ◽

Horizontal Distance ◽

Local Surface ◽

Atmospheric Scattering ◽

The Mean

Abstract. Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensional (3-D) Monte Carlo radiative transfer model to simulate 3-D irradiance fields. The calculated up- and downward irradiances in altitudes between 0.1 and 5 km are used to derive the area-averaged surface albedo using an iterative retrieval method that removes the effects due to atmospheric scattering and absorption within the layer beneath the considered level. For the case of adjacent land and sea surfaces, parametrizations are presented which quantify the horizontal distance from the coastline that is required to reduce surface heterogeneity effects on the area-averaged surface albedo to a given limit. The parametrization which is a function of altitude, aerosol optical depth, single scattering albedo, and the ratio of local land and sea albedo was applied for airborne spectral measurements. In addition, the deviation between area-averaged and local surface albedo is determined for more complex surface albedo maps. For moderate aerosol conditions (optical depth less than 0.4) and a wavelength range between 400 and 1000 nm, the altitude and the heterogeneity of the surface albedo are the dominant factors determining the mean deviation between local and area-averaged surface albedo. A parametrization of the mean deviation is applied to an albedo map that was derived from a Landsat image of an area in East Anglia (UK). Parametrization and direct comparison of local and area-averaged surface albedo show similar mean deviations (20% vs. 25%) over land.

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Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-7457-2012 ◽

2012 ◽

Vol 5 (5) ◽

pp. 7457-7487

Author(s):

E. Jäkel ◽

M. Wendisch ◽

B. Mayer

Keyword(s):

Optical Depth ◽

Surface Albedo ◽

Radiative Transfer Model ◽

Small Scale ◽

Mean Deviation ◽

Transfer Model ◽

Horizontal Distance ◽

Local Surface ◽

Atmospheric Scattering ◽

The Mean

Abstract. Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensional (3-D) Monte Carlo radiative transfer model to simulate 3-D irradiance fields. The calculated up- and downward irradiances in altitudes between 0.1 km and 5 km are used to derive the area-averaged surface albedo using an iterative retrieval method that removes the effects due to atmospheric scattering and absorption within the layer beneath the considered level. For the case of adjacent land and sea surfaces a parametrization is presented which quantifies the horizontal distance to the coastline that is required to reduce surface heterogeneity effects on the area-averaged surface albedo to a given limit. The parametrization which is a function of altitude, aerosol optical depth, and the ratio of local land and sea albedo was applied for airborne spectral measurements. In addition, the deviation between area-averaged and local surface albedo is determined for more complex surface albedo maps. For moderate aerosol conditions (optical depth less than 0.4) and the visible wavelength range, the altitude and the heterogeneity of the surface albedo are the dominant factors determining the mean deviation between local and area-averaged surface albedo. A parametrization of the mean deviation is applied to an albedo map that was derived from a Landsat image of an area in East Anglia (UK). Parametrization and direct comparison of local and area-averaged surface albedo show similar mean deviations (20% vs. 25%) over land.

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Restoring the night sky darkness at Observatorio del Teide: First application of the model Illumina version 2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2113 ◽

2020 ◽

Vol 497 (3) ◽

pp. 2501-2516 ◽

Cited By ~ 1

Author(s):

Martin Aubé ◽

Alexandre Simoneau ◽

Casiana Muñoz-Tuñón ◽

Javier Díaz-Castro ◽

Miquel Serra-Ricart

Keyword(s):

Radiative Transfer Model ◽

Small Scale ◽

Transfer Model ◽

Light Emitting ◽

The Past ◽

V Band ◽

Tenerife Island ◽

Sky Brightness ◽

Night Sky ◽

Sky Radiance

ABSTRACT The propagation of artificial light into real environments is complex. To perform its numerical modelling with accuracy, one must consider hyperspectral properties of the lighting devices and their geographic positions, the hyperspectral properties of the ground reflectance, the size and distribution of small-scale obstacles, the blocking effect of topography, the lamps angular photometry and the atmospheric transfer function (aerosols and molecules). A detailed radiative transfer model can be used to evaluate how a particular change in the lighting infrastructure may affect the sky radiance. In this paper, we use the new version (v2) of the Illumina model to evaluate a night sky restoration plan for the Teide Observatory located on the island of Tenerife, Spain. In the past decades, the sky darkness was severely degraded by growing light pollution on the Tenerife Island. In this work, we use the contribution maps giving the effect of each pixel of the territory to the artificial sky radiance. We exploit the hyperspectral capabilities of Illumina v2 and show how the contribution maps can be integrated over regions or municipalities according to the Johnson–Cousins photometric bands spectral sensitivities. The sky brightness reductions per municipality after a complete shutdown and a conversion to light-emitting diodes are calculated in the Johnson–Cousins B, V, R bands. We found that the conversion of the lighting infrastructure of Tenerife with LED (1800 and 2700 K), according to the conversion strategy in force, would result in a zenith V-band sky brightness reduction of ≈0.3 mag arcsec−2.

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Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3957-2007 ◽

2007 ◽

Vol 7 (14) ◽

pp. 3957-3968 ◽

Cited By ~ 33

Author(s):

H. Herbin ◽

D. Hurtmans ◽

S. Turquety ◽

C. Wespes ◽

B. Barret ◽

...

Keyword(s):

Water Vapour ◽

Experimental Studies ◽

Estimation Method ◽

Optimal Estimation ◽

Temporal Variations ◽

Global Scale ◽

Radiative Transfer Model ◽

Small Scale ◽

Transfer Model ◽

Water Isotopologues

Abstract. The isotopologic composition of water vapour in the atmosphere provides valuable information on many climate, chemical and dynamical processes. The accurate measurements of the water isotopologues by remote-sensing techniques remains a challenge, due to the large spatial and temporal variations. Simultaneous profile retrievals of the main water isotopologues (i.e. H216O, H218O and HDO) and their ratios are presented here for the first time, along their retrieved global distributions. The results are obtained by exploiting the high resolution infrared spectra recorded by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated in the nadir geometry onboard the ADEOS satellite between 1996 and 1997. The retrievals are performed on cloud-free radiances, measured during ten days of April 1997, considering two atmospheric windows (1205–1228 cm−1; 2004–2032 cm−1) and using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). Characterizations in terms of vertical sensitivity and error budget are provided. We show that a relatively high vertical resolution is achieved for H216O (~4–5 km), and that the retrieved profiles are in fair agreement with local sonde measurements, at different latitudes. The retrieved global distributions of H216O, H218O, HDO and their ratios are presented and found to be consistent with previous experimental studies and models. The Ocean-Continent difference, the latitudinal and vertical dependence of the water vapour amount and the isotopologic depletion are notably well reproduced. Others trends, possibly related to small-scale variations in the vertical profiles are also discussed. Despite the difficulties encountered for computing accurately the isotopologic ratios, our results demonstrate the ability of infrared nadir sounding for monitoring atmospheric isotopologic water vapour distributions on a global scale.

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Sensitivity of formaldehyde (HCHO) column measurements from a geostationary satellite to aerosol temporal variation in East Asia

10.5194/acp-2016-712 ◽

2016 ◽

Author(s):

Hyeong-Ahn Kwon ◽

Rokjin J. Park ◽

Jaein I. Jeong ◽

Seungun Lee ◽

Gonzalo González Abad ◽

...

Keyword(s):

East Asia ◽

Temporal Variation ◽

Geostationary Satellite ◽

Dust Storms ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Observation System ◽

Transfer Model ◽

True Value ◽

The Impact

Abstract. We examine upcoming geostationary satellite observations of formaldehyde (HCHO) columns in East Asia and the retrieval sensitivity to the temporal variation of air mass factor (AMF) considering the presence of aerosols. Observation system simulation experiments (OSSE) were conducted using a combination of a global 3-D chemical transport model (GEOS-Chem), a radiative transfer model (VLIDORT), and a HCHO retrieval algorithm developed for Geostationary Environment Monitoring Spectrometer (GEMS), which will be launched in 2019. Application of the retrieval algorithm to simulated hourly radiances yields the retrieved HCHO column concentrations, which are then compared with the GEOS-Chem HCHO columns as a true value for the evaluation of the retrieval algorithm. In order to examine the retrieval sensitivity to the temporal variation of AMF, we compare the retrieved HCHO columns using monthly versus hourly AMF values and find that the HCHO vertical columns with hourly AMF are in better agreement with the true values, relative to those with monthly AMF. The differences between hourly and monthly AMF range from −0.70 to 0.73 in absolute value and are mainly caused by temporal changes of aerosol chemical composition: scattering aerosol enhances AMF, whereas absorbing aerosol reduces it. The temporal variations of AMF caused by aerosols increase and decrease HCHO VCDs by 84 % and 34 %, respectively, compared to HCHO VCDs using monthly AMF. We apply our calculated AMF with the aerosol effects to OMI HCHO products in March, 2006 when Asian dust storms occurred and find −18 %–33 % changes in the retrieved HCHO columns in East Asia. The impact of aerosols cannot be neglected for future geostationary observations.

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Measuring Stratospheric H2O with an Airborne Spectrometer

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-13-00191.1 ◽

2014 ◽

Vol 31 (7) ◽

pp. 1502-1515 ◽

Cited By ~ 5

Author(s):

Maziar Bani Shahabadi ◽

Yi Huang

Keyword(s):

Water Vapor ◽

Radiative Transfer ◽

Spectral Resolution ◽

High Sensitivity ◽

Far Infrared ◽

High Spectral Resolution ◽

Radiative Transfer Model ◽

Small Scale ◽

Transfer Model ◽

Infrared Spectral

Abstract This study examines the ability of an infrared spectral sensor flying at the tropopause level for retrieving stratospheric H2O. Synthetic downwelling radiance spectra simulated by the line-by-line radiative transfer model are used for this examination. The potential of high-sensitivity water vapor retrieval is demonstrated by an ideal sensor with low detector noise, high spectral resolution, and full infrared coverage. A suite of hypothetical sensors with varying specifications is then examined to determine the technological requirements for a satisfactory retrieval. This study finds that including far infrared in the sensor’s spectral coverage is essential for achieving accurate H2O retrieval with an accuracy of 0.4 ppmv (1-sigma). The uncertainties in other gas species such as CH4, N2O, O3, and CO2 do not significantly affect the H2O retrieval. Such a hyperspectral instrument may afford an advantageous tool, especially for detecting small-scale lower-stratospheric moistening events.

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Assimilation of Satellite Microwave Observations over the Rainbands of Tropical Cyclones

Monthly Weather Review ◽

10.1175/mwr-d-19-0341.1 ◽

2020 ◽

Vol 148 (12) ◽

pp. 4729-4745

Author(s):

Isaac Moradi ◽

K. Franklin Evans ◽

Will McCarty ◽

Marangelly Cordero-Fuentes ◽

Ronald Gelaro ◽

...

Keyword(s):

Tropical Cyclones ◽

Microwave Radiometer ◽

Monte Carlo Integration ◽

Advanced Technology ◽

Radiative Transfer Model ◽

Small Scale ◽

Transfer Model ◽

Uncertainty Estimates ◽

Satellite Microwave ◽

The Impact

AbstractA novel Bayesian Monte Carlo integration (BMCI) technique was developed to retrieve geophysical variables from satellite microwave radiometer data in the presence of tropical cyclones. The BMCI technique includes three steps: generating a stochastic database, simulating satellite brightness temperatures using a radiative transfer model, and retrieving geophysical variables such as profiles of temperature, relative humidity, and cloud liquid and ice water content from real observations. The technique also provides uncertainty estimates for each retrieval and can output the error covariance matrix of selected parameters. The measurements from the Advanced Technology Microwave Sounder (ATMS) on board Suomi National Polar-Orbiting Partnership (Suomi NPP) and the Global Precipitation Measurement (GPM) Microwave Imager (GMI) were used as input. A new technique was developed to correct the ATMS and GMI observations for the beam-filling effect, which is due to small-scale variability of precipitation and clouds when compared with the instrument footprint and also the nonlinear relation between the brightness temperature and precipitation. In addition, the assimilation of the BMCI retrievals into the NASA GEOS model is discussed for Hurricane Maria. The results show that assimilating the BMCI retrievals can influence the dynamical features of the cyclone, including a stronger warm core, a symmetric eye, and vertically aligned wind columns. Two possible factors that may limit the impact of the BMCI retrievals include 1) the resolution of the model (about 25 km), which was too coarse to show the potential of the BMCI data in improving the representation of tropical storms in the model forecast, and 2) the data assimilation system not being able to consider vertically correlated observation errors.

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