scholarly journals The performance of Aeolus in heterogeneous atmospheric conditions using high-resolution radiosonde data

2014 ◽  
Vol 7 (2) ◽  
pp. 1393-1455
Author(s):  
X. J. Sun ◽  
R. W. Zhang ◽  
G. J. Marseille ◽  
A. Stoffelen ◽  
D. Donovan ◽  
...  
Keyword(s):  
Optical Properties ◽  
High Resolution ◽  
Relative Humidity ◽  
Weather Prediction ◽  
Error Variance ◽  
Radiosonde Data ◽  
Atmospheric Conditions ◽  
Wind Profiles ◽  
Height Assignment ◽  
Aerosol Backscatter

Abstract. The ESA Aeolus mission aims to measure wind profiles from space. In preparation for launch we aim to assess the expected bias in retrieved winds from the Mie and Rayleigh channel signals induced by atmospheric heterogeneity. Observation biases are known to be detrimental when gone undetected in Numerical Weather Prediction (NWP). Aeolus processing equipment should therefore be prepared to detect heterogeneous atmospheric scenes and take measures, e.g., reject or reduce the weight of observations when used in NWP. Radiosondes provide the wind vector at about 10 m resolution. We present a method to simulate co-located cloud and aerosol optical properties from radiosonde observations. We show that cloud layers can be detected along the radiosonde path from radiosonde measured relative humidity and temperature. A parameterization for aerosol backscatter and extinction along the radiosonde path is presented based on a climatological aerosol backscatter profile and radiosonde relative humidity. The resulting high-resolution database of atmospheric wind and optical properties serves as input for Aeolus wind simulations. It is shown that Aeolus wind error variance grows quadratically with bin size and the wind-shear over the bin. Strong scattering aerosol or cloud layers may cause biases exceeding 1ms−1 for typical tropospheric conditions and 1 km Mie channel bin size, i.e., substantially larger than the mission bias requirement of 0.4 ms−1. Advanced level-2 processing of Aeolus winds including estimation of atmosphere optical properties is needed to detect regions with large heterogeneity, potentially yielding biased winds. Besides applicable for Aeolus the radiosonde database of co-located high-resolution wind and cloud information can be used for the validation of atmospheric motion wind vectors (AMV) or to correct their height assignment errors.

scholarly journals The performance of Aeolus in heterogeneous atmospheric conditions using high-resolution radiosonde data

2014 ◽  
Vol 7 (8) ◽  
pp. 2695-2717 ◽  
Author(s):  
X. J. Sun ◽  
R. W. Zhang ◽  
G. J. Marseille ◽  
A. Stoffelen ◽  
D. Donovan ◽  
...  
Keyword(s):  
Optical Properties ◽  
High Resolution ◽  
Weather Prediction ◽  
European Space Agency ◽  
Radiosonde Data ◽  
Atmospheric Conditions ◽  
High Resolution Data ◽  
Rayleigh Channel ◽  
Space Agency ◽  
Height Assignment

Abstract. The European Space Agency Aeolus mission aims to measure wind profiles from space. A major challenge is to retrieve high quality winds in heterogeneous atmospheric conditions, i.e. where both the atmospheric dynamics and optical properties vary strongly within the sampling volume. In preparation for launch we aim to quantify the expected error of retrieved winds from atmospheric heterogeneity, particularly in the vertical, and develop algorithms for wind error correction, as part of the level-2B processor (L2Bp). We demonstrate that high-resolution data from radiosondes provide valuable input to establish a database of collocated wind and atmospheric optics at 10 m vertical resolution to simulate atmospheric conditions along Aeolus' lines of sight. The database is used to simulate errors of Aeolus winds retrieved from the Mie and Rayleigh channel signals. The non-uniform distribution of molecules in the measurement bin introduces height assignment errors in Rayleigh channel winds up to 2.5% of the measurement bin size in the stratosphere which translates to 0.5 m s−1 bias for typical atmospheric conditions, if not corrected. The presence of cloud or aerosol layers in the measurement bin yields biases in Mie channel winds which cannot be easily corrected and mostly exceed the mission requirement of 0.4 m s−1. The collocated Rayleigh channel wind solution is generally preferred because of smaller biases, in particular for transparent cloud and aerosol layers with one-way transmission above 0.8. The results show that Aeolus L2Bp, under development, can be improved by the estimation of atmosphere optical properties to correct for height assignment errors and to identify wind solutions potentially detrimental when used in Numerical Weather Prediction.

Aeolus Rayleigh-channel winds in cloudy conditions

2021 ◽  
Author(s):  
Gert-Jan Marseille
Keyword(s):  
Rayleigh Scattering ◽  
Scattered Light ◽  
Weather Prediction ◽  
Ultra Violet ◽  
Mie Scattering ◽  
Atmospheric Conditions ◽  
Atmospheric Flow ◽  
Rayleigh Channel ◽  
Wind Profiles ◽  
Height Assignment

<p>Aeolus was launched in August 2018 and is expected to be operational until 2022. Aeolus is the first Doppler wind lidar in space to measure wind profiles through Rayleigh scattering of an ultra-violet laser beam and the determination of the Doppler shift of the scattered light by molecules along the Line-Of-Sight (LOS). In addition, Mie scattering provides winds on aerosol and cloud particles. The atmosphere return signal is a small bandwidth peak (from Mie scattering) on top of a broadband spectrum (from Rayleigh scattering). The tails and central part of the spectrum are being processed separately to yield so-called Rayleigh channel and Mie channel winds respectively.</p><p>Signals in both channels are being accumulated onboard the satellite to segments of 2.85 km length along the satellite track, denoted measurements. Rayleigh winds are obtained by on-ground processing through accumulating typically 30 measurements to yield a single Rayleigh wind observation of sufficient quality for use in Numerical Weather Prediction (NWP). The vertical resolution of the horizontally projected LOS wind profiles is typically 500 m in the boundary layer, 1 km in the free-troposphere and 1.5-2 km in the stratosphere, but this can and has been changed in a flexible way during the mission.</p><p>In case of clouds and/or aerosols presence within the sensing atmospheric volume, signal from Mie scattering leaks into the Rayleigh channel signal. Since the Rayleigh-channel signal processing assumes a pure molecular signal this so-called Mie contamination causes biases in retrieved winds. This is solved through classifying measurements as either ‘clear’ or ‘cloudy’ before accumulation to observation level. Clear measurements (out of a total of 30) are accumulated to yield a Rayleigh-clear wind. This procedure has proven successful and Aeolus Rayleigh-clear winds are used operationally today by a number of meteorological centers around the world.</p><p>A similar procedure for cloudy measurements is less trivial and requires correction for Mie contamination. So far, implemented corrections were not successful in producing Rayleigh-cloudy winds of sufficient quality for use in NWP. A new correction scheme has been introduced and tested recently and proved successful to produce bias-free winds and a random error slightly larger as compared to Rayleigh-clear winds. The latter is explained by increased heterogeneous atmospheric conditions in which Rayleigh-cloudy winds are obtained. Interestingly, Rayleigh-cloudy and Mie-cloudy winds are obtained for identical atmospheric conditions and as such provide independent information on the atmospheric flow, which allows to characterize the error sources of the different types of wind observations, including instrumental/calibration errors, but also errors due to incorrect height assignment and representativity.</p><p>This paper describes the new scheme to correct Rayleigh winds for Mie contamination and its application to Aeolus data. The results show that resulting Rayleigh-cloudy winds are of good quality to be considered for operational use in NWP.</p>

scholarly journals Validation of Dual-Doppler Wind Profiles with in situ Anemometry

2015 ◽  
Vol 32 (5) ◽  
pp. 943-960 ◽  
Author(s):  
W. Scott Gunter ◽  
John L. Schroeder ◽  
Brian D. Hirth
Keyword(s):  
High Resolution ◽  
Wind Speed ◽  
Doppler Radar ◽  
Heavy Precipitation ◽  
Atmospheric Conditions ◽  
Wind Speeds ◽  
Time Histories ◽  
Mean Wind Speed ◽  
Wind Profiles

AbstractTypical methods used to acquire wind profiles from Doppler radar measurements rely on plan position indicator (PPI) scans being performed at multiple elevation angles to utilize the velocity–azimuth display technique or to construct dual-Doppler synthesis. These techniques, as well as those employed by wind profilers, often produce wind profiles that lack the spatial or temporal resolution to resolve finescale features. If two radars perform range–height indicator (RHI) scans (constant azimuth, multiple elevations) along azimuths separated by approximately 90°, then the intersection of the coordinated RHI planes represents a vertical set of points where dual-Doppler wind syntheses are possible and wind speed and direction profiles can be retrieved. This method also allows for the generation of high-resolution wind time histories that can be compared to anemometer time histories. This study focuses on the use of the coordinated RHI scanning strategy by two high-resolution mobile Doppler radars in close proximity to a 200-m instrumented tower. In one of the first high-resolution, long-duration comparisons of dual-Doppler wind synthesis with in situ anemometry, the mean and turbulence states of the wind measured by each platform were compared in varying atmospheric conditions. Examination of mean wind speed and direction profiles in both clear-air (nonprecipitating) and precipitating environments revealed excellent agreement above approximately 50 m. Below this level, dual-Doppler wind speeds were still good but slightly overestimated as compared to the anemometer-measured wind speeds in heavy precipitation. Bulk turbulence parameters were also slightly underestimated by the dual-Doppler syntheses.

scholarly journals Humidity sensor failure: a problem that should not be neglected by the numerical weather prediction community

2014 ◽  
Vol 7 (7) ◽  
pp. 6625-6649
Author(s):  
Y. Liu ◽  
N. Tang
Keyword(s):  
Relative Humidity ◽  
Numerical Weather Prediction ◽  
Humidity Sensor ◽  
Weather Prediction ◽  
Radiosonde Data ◽  
Control Procedure ◽  
Sensor Failure ◽  
Satellite Mission ◽  
Numerical Weather ◽  
Weather And Climate

Abstract. In this paper, a new issue that very low relative humidity observations exist in a deeper atmosphere layer in the low- and mid-troposphere is studied on the basis of the global radiosonde observations from December 2008 to November 2009, and the humidity retrieval productions from Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC, referred to as COSMIC hereafter) in the same period. Results show that these extremely dry relative humidity observations are considerable universal in the worldwide operational radiosonde data. Globally, the annual average occurrence probability of the extremely dry relative humidity is of 4.2%. These measurements usually occur between 20° and 40° latitudes in both Northern and Southern Hemispheres, and in the height from 700 to 450 hPa in the low- and mid-troposphere. Winter and spring are the favoured seasons for these extremely dry humidity observations, with the maximum ratio of 9.53% in the Northern Hemisphere and 16.82% in the Southern Hemisphere. The phenomenon is mainly related to the performance of the radiosonde humidity sensor and the cloud types traversed by the radiosonde balloon. These extremely low relative humidity observations are erroneous, which cannot represent the real atmospheric status, and are likely caused by the failure of humidity sensor. However, these observations have been archived as the formal data. It will affect the reliability of numerical weather prediction, the analysis of weather and climate, if the quality control procedure is not applied.

scholarly journals Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

2015 ◽  
Vol 8 (10) ◽  
pp. 3105-3117 ◽  
Author(s):  
J. K. Hughes ◽  
A. N. Ross ◽  
S. B. Vosper ◽  
A. P. Lock ◽  
B. C. Jemmett-Smith
Keyword(s):  
High Resolution ◽  
Relative Humidity ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Wave Radiation ◽  
Cold Pool ◽  
Cold Air ◽  
Numerical Weather ◽  
Pool Formation ◽  
Very High

Abstract. The formation of cold air pools in valleys under stable conditions represents an important challenge for numerical weather prediction (NWP). The challenge is increased when the valleys that dominate cold pool formation are on scales unresolved by NWP models, which can lead to substantial local errors in temperature forecasts. In this study a 2-month simulation is presented using a nested model configuration with a finest horizontal grid spacing of 100 m. The simulation is compared with observations from the recent COLd air Pooling Experiment (COLPEX) project and the model's ability to represent cold pool formation, and the surface energy balance is assessed. The results reveal a bias in the model long-wave radiation that results from the assumptions made about the sub-grid variability in humidity in the cloud parametrization scheme. The cloud scheme assumes relative humidity thresholds below 100 % to diagnose partial cloudiness, an approach common to schemes used in many other models. The biases in radiation, and resulting biases in screen temperature and cold pool properties are shown to be sensitive to the choice of critical relative humidity, suggesting that this is a key area that should be improved for very high-resolution modeling.

scholarly journals ESA’s spaceborne lidar mission ADM-Aeolus; project status and preparations for launch

2018 ◽  
Vol 176 ◽  
pp. 04007 ◽  
Author(s):  
Anne Grete Straume ◽  
Anders Elfving ◽  
Denny Wernham ◽  
Frank de Bruin ◽  
Thomas Kanitz ◽  
...  
Keyword(s):  
Optical Properties ◽  
Weather Prediction ◽  
Atmospheric Dynamics ◽  
The Novel ◽  
Aerosol Optical Properties ◽  
Climate Research ◽  
Wind Lidar ◽  
Core Mission ◽  
Wind Profiles ◽  
Doppler Wind Lidar

ESA’s Doppler Wind lidar mission, the Atmospheric Dynamics Mission (ADM-Aeolus, hereafter abbreviated to Aeolus), was chosen as an Earth Explorer Core mission within the Living Planet Programme in 1999. It shall demonstrate the potential of space-based Doppler Wind lidars for operational measurements of wind profiles and their use in Numerical Weather Prediction (NWP) and climate research. Spin-off products are profiles of cloud and aerosol optical properties. Aeolus carries the novel Doppler Wind lidar instrument ALADIN. The mission prime is Airbus Defence & Space UK (ADS-UK), and the instrument prime is Airbus Defence & Space France (ADS-F).

scholarly journals Radiation fog formation alerts using attenuated backscatter power from automatic Lidars and ceilometers

2016 ◽  
Author(s):  
Martial Haeffelin ◽  
Quentin Laffineur ◽  
Juan-Antonio Bravo-Aranda ◽  
Marc-Antoine Drouin ◽  
Juan-Andrés Casquero-Vera ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Temporal Evolution ◽  
Weather Prediction ◽  
Atmospheric Conditions ◽  
Hygroscopic Growth ◽  
Radiation Fog ◽  
Low Visibility ◽  
Humidity Measurements ◽  
Ground Current ◽  
Growth Laws

Abstract. Radiation fog occurs over many locations around the world in stable atmospheric conditions. Air traffic at busy airports can be significantly disrupted because low visibility at the ground makes it unsafe to take off, land and taxi on the ground. Current numerical weather prediction forecasts are able to predict general conditions favorable for fog formation, but not the exact time or location of fog occurrence. A selected set of observations available in near realtime at strategic locations could also be useful to track the evolution of key processes and key parameters that drive fog formation. Such observations could complement the information predicted by NWP models that is made available to airport forecasters in support of their fog forecast. This paper presents an experimental setup based on collocated automatic lidar and ceilometer measurements, relative humidity measurements and horizontal visibility measurements to study hygroscopic growth of fog condensation nuclei. This process can take several minutes to hours and can be tracked using lidar or ceilometer attenuated backscatter profiles. Based on hygroscopic growth laws we derive a set of parameters that can be used to provide alerts minutes to hours prior to formation of radiation fog. We present an algorithm that uses the temporal evolution of attenuated backscatter measurements to derive pre-fog formation alerts. The performance of the algorithm is tested on 45 independent pre-fog situations at two locations (near Paris, France and Brussels, Belgium). We find that pre-fog alerts occur predominantly 10–50 min prior to fog formation at an altitude ranging 0 to 100 m above ground. In a few cases, alerts can occur up to 100 min prior to fog formation. Alert durations are found to be sensitive to relative humidity conditions found a few hours prior to the fog.

scholarly journals Derivation of Clear-Air Turbulence Parameters from High-Resolution Radiosonde Data

2017 ◽  
Vol 34 (2) ◽  
pp. 277-293 ◽  
Author(s):  
E. Martini ◽  
A. Freni ◽  
F. Cuccoli ◽  
L. Facheris
Keyword(s):  
Refractive Index ◽  
High Resolution ◽  
Potential Temperature ◽  
Structure Constant ◽  
Thin Layers ◽  
Index Structure ◽  
Radiosonde Data ◽  
Atmospheric Conditions ◽  
Air Turbulence ◽  
The Impact

AbstractThe knowledge of atmospheric refractive index structure constant () profiles is fundamental to determine the intensity of turbulence, and hence the impact of the scintillation impairment on the signals propagating in the troposphere. However, their relation with atmospheric variables is not straightforward, and profiles based on statistical considerations are normally employed. This can be a shortcoming when performing simulations for which scintillation disturbances need to be consistent with the assumed atmospheric conditions. To overcome this limitation, this work describes a procedure to obtain an estimate of the refractive index structure constant profile of clear-air turbulence under given atmospheric conditions. The procedure is based on the application of the vertical gradient approach to high-resolution radiosonde data. Since turbulence is known to be confined to vertically thin layers, a preliminary identification of turbulent layers is required. This is accomplished by analyzing the profiles of the Richardson number. The value of the outer scale length is estimated using the Thorpe length calculated from the potential temperature profile. The procedure is applied to high-resolution radiosonde data that have been acquired from the Stratosphere–Troposphere Processes and their Role in Climate (SPARC) Data Center, and the obtained results are consistent with measured profiles previously published in the literature.

Boundary Layer and Surface Verification of the High-Resolution Rapid Refresh, Version 3

2020 ◽  
Vol 35 (6) ◽  
pp. 2255-2278
Author(s):  
Robert G. Fovell ◽  
Alex Gallagher
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Wind Speed ◽  
Prediction Models ◽  
Weather Prediction ◽  
Potential Temperature ◽  
Ground Level ◽  
Systematic Errors ◽  
Radiosonde Data ◽  
Near Surface

AbstractWhile numerical weather prediction models have made considerable progress regarding forecast skill, less attention has been paid to the planetary boundary layer. This study leverages High-Resolution Rapid Refresh (HRRR) forecasts on native levels, 1-s radiosonde data, and (primarily airport) surface observations across the conterminous United States. We construct temporally and spatially averaged composites of wind speed and potential temperature in the lowest 1 km for selected months to identify systematic errors in both forecasts and observations in this critical layer. We find near-surface temperature and wind speed predictions to be skillful, although wind biases were negatively correlated with observed speed and temperature biases revealed a robust relationship with station elevation. Above ≈250 m above ground level, below which radiosonde wind data were apparently contaminated by processing, biases were small for wind speed and potential temperature at the analysis time (which incorporates sonde data) but became substantial by the 24-h forecast. Wind biases were positive through the layer for both 0000 and 1200 UTC, and morning potential temperature profiles were marked by excessively steep lapse rates that persisted across seasons and (again) exaggerated at higher elevation sites. While the source or cause of these systematic errors are not fully understood, this analysis highlights areas for potential model improvement and the need for a continued and accessible archive of the data that make analyses like this possible.

scholarly journals Effects of SO<sub>2</sub> on optical properties of secondary organic aerosol generated from photooxidation of toluene under different relative humidity

2019 ◽  
Author(s):  
Wenyu Zhang ◽  
Weigang Wang ◽  
Junling Li ◽  
Chao Peng ◽  
Kun Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Optical Properties ◽  
Relative Humidity ◽  
Secondary Organic Aerosol ◽  
Complex Refractive Index ◽  
Organic Aerosol ◽  
Conjugated Oligomers ◽  
Atmospheric Conditions ◽  
Multiphase Reaction ◽  
532 Nm

Abstract. Secondary organic aerosol (SOA) have great impacts on air quality, climate change and human health. The composition and physicochemical properties of SOA differ a lot for they originated under different atmospheric conditions and from various precursors and oxidations. In this work, photooxidation experiments of toluene were performed under four conditions (dry, dry with SO2, wet, and wet with SO2) to investigate the effect of SO2 under different relative humidity on the composition and optical properties of SOA at the wavelength of 375 nm and 532 nm. According to our results, the increase of humidity enhances not only light absorption, but also scattering property of SOA. Highly conjugated oligomers formed through multiphase reaction might be the reasons of this phenomenon. Adding SO2 slightly lower the real part of complex refractive index (n) of SOA: ndry, SO2 

Sign in / Sign up

Export Citation Format

Share Document