scholarly journals Study of the seasonal variation in Aeolus wind product performance over China using ERA5 and radiosonde data

2021 ◽  
Vol 21 (15) ◽  
pp. 11489-11504
Author(s):  
Siying Chen ◽  
Rongzheng Cao ◽  
Yixuan Xie ◽  
Yinchao Zhang ◽  
Wangshu Tan ◽  
...  
Keyword(s):  
Relative Error ◽  
Wind Direction ◽  
Signal To Noise Ratio ◽  
Product Performance ◽  
Radiosonde Data ◽  
Horizontal Wind ◽  
Horizontal Line ◽  
The Mean ◽  
L Band ◽  
Relative Errors

Abstract. Aeolus wind products became available to the public on 12 May 2020. In this study, Aeolus wind observations, L-band radiosonde (RS) data, and the European Centre for Medium-Range Weather Forecasts fifth-generation atmospheric reanalysis (ERA5) data were used to analyze the seasonality of Aeolus wind product performance over China. Based on the Rayleigh-clear and Mie-cloudy data, the data quality of the Aeolus effective detection data was verified, and the results showed that the Aeolus data were in good agreement with the L-band RS and ERA5 data. The Aeolus data relative errors in the four regions (Chifeng, Baoshan, Shapingba, and Qingyuan) in China were calculated based on different months (July to December 2019 and May to October 2020). The relative error in the Rayleigh-clear data in summer was significantly higher than that in winter, with the mean relative error parameter in July 174 % higher than that in December. The mean random error increased by 0.97 m s−1 in July compared with December, which also supported this conclusion. In addition, the distribution of the wind direction and high-altitude clouds in different months (July and December) was analyzed. The results showed that the distribution of the angle between the horizontal wind direction of the atmosphere and the horizontal line of sight had a greater proportion in the high error interval (70–110∘) in summer, and this proportion was 8.14 % higher in July than in December. The cloud top height in summer was approximately 3–5 km higher than that in winter, which might decrease the signal-to-noise ratio of Aeolus. Therefore, the wind product performance of Aeolus was affected by seasonal factors, which might be caused by seasonal changes in wind direction and cloud distribution.

scholarly journals Study on the seasonal variation of Aeolus detection performance over China using ERA5 and radiosonde data

2021 ◽  
Author(s):  
Siying Chen ◽  
Rongzheng Cao ◽  
Yixuan Xie ◽  
Yinchao Zhang ◽  
Wangshu Tan ◽  
...  
Keyword(s):  
Relative Error ◽  
Wind Direction ◽  
Signal To Noise Ratio ◽  
Detection Performance ◽  
Radiosonde Data ◽  
Horizontal Wind ◽  
Horizontal Line ◽  
Weather Forecasts ◽  
L Band ◽  
Relative Errors

Abstract. Aeolus wind products have been available to ordinary users on May 12, 2020. In this paper, the Aeolus wind observations, L-band radiosonde (L-band RS) data and the European Centre for Medium-Range Weather Forecasts (ECMWF) fifth generation atmospheric reanalyses (ERA5) are used to analyse the seasonality of Aeolus detection performance over China. Based on the Rayleigh-clear data and Mie-cloudy data, the data quality of the Aeolus effective detection data is verified, and the results show that the Aeolus data is in good agreement with the L-band RS data and the ERA5 data. The relative errors of Aeolus data in the four regions (Chifeng, Baoshan, Shapingba and Qingyuan) in China were calculated according to different months (July to December 2019, May to October 2020). The relative error of the Rayleigh-clear data in summer is significantly higher than that in winter, as the mean relative error parameter in July is 174 % higher than that in December. Besides, the distribution about the wind direction and the high-altitude clouds in different months (July and December) are analysed. The results show that the distribution of angle, between the horizontal wind direction of the atmosphere and the horizontal line of sight (HLOS), has a greater proportion in the high error interval (70°–110°) in summer, and this proportion is 8.14 % higher in July than in December. In addition, the cloud top height in summer is about 3–5 km higher than in winter, which may reduce the signal-to-noise ratio (SNR) of Aeolus. The results show that the detection performance of Aeolus is affected by seasonal factors, which may be caused by seasonal changes in wind direction and cloud distribution.

scholarly journals Vertical wavenumber spectra of three-dimensional winds revealed by radiosonde observations at midlatitude

2017 ◽  
Vol 35 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Shao Dong Zhang ◽  
Chun Ming Huang ◽  
Kai Ming Huang ◽  
Ye Hui Zhang ◽  
Yun Gong ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Three Dimensional ◽  
Theoretical Models ◽  
Meridional Wind ◽  
Vertical Wind ◽  
Radiosonde Data ◽  
Horizontal Wind ◽  
Spectral Structure ◽  
Wind Fluctuation ◽  
The Mean

Abstract. By applying 12-year (1998–2009) radiosonde data over a midlatitude station, we studied the vertical wavenumber spectra of three-dimensional wind fluctuations. The horizontal wind spectra in the lower stratosphere coincide well with the well-known universal spectra, with mean spectral slopes of −2.91 ± 0.09 and −2.99 ± 0.09 for the zonal and meridional wind spectra, respectively, while the mean slopes in the troposphere are −2.64 ± 0.07 and −2.70  ±  0.06, respectively, which are systematically less negative than the canonical slope of −3. In both the troposphere and lower stratosphere, the spectral amplitudes (slopes) of the horizontal wind spectra are larger (less negative) in winter, and they are larger (less negative) in the troposphere than in the lower stratosphere. Moreover, we present the first statistical results of vertical wind fluctuation spectra, which revealed a very shallow spectral structure, with mean slopes of −0.58 ± 0.06 and −0.23 ± 0.05 in the troposphere and lower stratosphere, respectively. Such a shallow vertical wind fluctuation spectrum is considerably robust. Different from the horizontal wind spectrum, the slopes of the vertical wind spectra in both the troposphere and lower stratosphere are less negative in summer. The height variation of vertical wind spectrum amplitude is also different from that of the horizontal wind spectrum, with a larger amplitude in the lower stratosphere. These evident differences between the horizontal and vertical wind spectra strongly suggest they should obey different spectral laws. Quantitative comparisons with various theoretical models show that no existing spectral theories can comprehensively explain the observed three-dimensional wind spectra, indicating that the spectral features of atmospheric fluctuations are far from fully understood.

scholarly journals Assessment of COSMIC radio occultation retrieval product using global radiosonde data

2013 ◽  
Vol 6 (4) ◽  
pp. 1073-1083 ◽  
Author(s):  
B.-R. Wang ◽  
X.-Y. Liu ◽  
J.-K. Wang
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Relative Error ◽  
Radio Occultation ◽  
Water Vapor Pressure ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Cosmic Radio ◽  
The Mean ◽  
Matching Criteria

Abstract. The radio occultation retrieval product of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation sounding system was verified using the global radiosonde data from 2007 to 2010. Samples of 4 yr were used to collect quantities of data using much stricter matching criteria than previous studies to obtain more accurate results. The horizontal distance between the radiosonde station and the occultation event is within 100 km, and the time window is 1 h. The comparison was performed from 925 hPa to 10 hPa. The results indicated that the COSMIC's temperature data agreed well with the radiosonde data. The global mean temperature bias was −0.09 K, with a standard deviation (SD) of 1.72 K. According to the data filtration used in this paper, the mean specific humidity bias of 925–200 hPa is −0.012 g kg−1, with a SD of 0.666 g kg−1, and the mean relative error of water vapor pressure is about 33.3%, with a SD of 107.5%. The COSMIC quality control process failed to detect some of the abnormal extremely small humidity data which occurred frequently in subtropical zone. Despite the large relative error of water vapor pressure, the relative error of refractivity is small. This paper also provides a comparison of eight radiosonde types with COSMIC product. Because the retrieval product is affected by the background error which differed between different regions, the COSMIC retrieval product could be used as a benchmark if the precision requirement is not strict.

scholarly journals A two-year intercomparison of CW focusing wind lidar and tall mast wind measurements at Cabauw

2020 ◽  
Author(s):  
Steven Knoop ◽  
Fred C. Bosveld ◽  
Marijn J. de Haij ◽  
Arnoud Apituley
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Continuous Wave ◽  
Data Availability ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Low Clouds ◽  
Wind Measurements ◽  
Wind Lidar ◽  
The Mean

Abstract. A two-year measurement campaign of the ZephIR 300 vertical profiling continuous-wave (CW) focusing wind lidar has been carried out by the Royal Netherlands Meteorological Institute (KNMI) at the Cabauw site. We focus on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213-m tall meteorological mast. We find an overall availability of quality controlled wind lidar data of 97 % to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm/h or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m/s with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. The mean bias in the wind direction is within 2°, which is on the same order as the combined uncertainty in the alignment of the wind lidars and the mast wind vanes. The well-known 180° error in the wind direction output for this type of instrument occurs about 9 % of the time. A correction scheme based on data of an auxiliary wind vane at a height of 10 m is applied, leading to a reduction of the 180° error below 2 %. This scheme can be applied in real-time applications in case a nearby, freely exposed, mast with wind direction measurements at a single height is available.

scholarly journals A 2-year intercomparison of continuous-wave focusing wind lidar and tall mast wind measurements at Cabauw

2021 ◽  
Vol 14 (3) ◽  
pp. 2219-2235
Author(s):  
Steven Knoop ◽  
Fred C. Bosveld ◽  
Marijn J. de Haij ◽  
Arnoud Apituley
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Continuous Wave ◽  
Data Availability ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Low Clouds ◽  
Wind Measurements ◽  
Wind Lidar ◽  
The Mean

Abstract. A 2-year measurement campaign of the ZephIR 300 vertical profiling continuous-wave (CW) focusing wind lidar has been carried out by the Royal Netherlands Meteorological Institute (KNMI) at the Cabauw site. We focus on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213 m tall meteorological mast. We find an overall availability of quality-controlled wind lidar data of 97 % to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm h−1 or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m s−1 with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. The mean bias in the wind direction is within 2∘, which is of the same order as the combined uncertainty in the alignment of the wind lidars and the mast wind vanes. The well-known 180∘ error in the wind direction output for this type of instrument occurs about 9 % of the time. A correction scheme based on data of an auxiliary wind vane at a height of 10 m is applied, leading to a reduction of the 180∘ error below 2 %. This scheme can be applied in real-time applications in the situation that a nearby freely exposed mast with wind direction measurements at a single height is available.

scholarly journals Observations of water vapor mixing ratio and flux in Tibetan Plateau

2015 ◽  
Vol 8 (11) ◽  
pp. 11925-11952
Author(s):  
S. Wu ◽  
G. Dai ◽  
X. Song ◽  
B. Liu ◽  
L. Liu
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
High Elevation ◽  
Radiosonde Data ◽  
The Tibetan Plateau ◽  
Mixing Ratio ◽  
Vapor Cloud ◽  
The Mean ◽  
Relative Errors ◽  
Water Vapor Mixing Ratio

Abstract. The water vapor expedition experiment campaign was operated in the Tibetan Plateau during July and August 2014, by utilizing the Water vapor, Cloud and Aerosol Lidar (WACAL). The observation was carried out in Nagqu area (31.5° N, 92.05° E), which is 4508 m above the mean sea level. During the observation, the water vapor mixing ratio at high elevation was obtained. In this paper, the methodology of the WACAL and the retrieval method are presented in particular. The validation of water vapor mixing ratio measured during the field campaigns is completed by comparing the Lidar measurements to the radiosonde data. WACAL observations from July to August illustrate the diurnal variation of water vapor mixing ratio in the planetary boundary layer in this high elevation area. The mean water vapor mixing ratio in Nagqu in July and August is about 9.4 g kg−1 and the values vary from 6.0 to 11.7 g kg−1 near ground. The SNRs and relative errors of the data are analyzed and discussed as well in this paper. Finally, combining the vertical wind speed profiles measured by the coherent wind lidar, the vertical flux of water vapor is calculated and the upwelling and deposition of the water vapor are monitored. It is the first application, to our knowledge, to operate continuously atmospheric observation by utilizing multi-disciplinary lidar at altitude higher than 4000 m which is significant for research on the boundary dynamics and meteorology of Tibetan Plateau.

Application of pyrometer and standard sample to determine surface temperature of studied materials

2019 ◽  
pp. 9-13
Author(s):  
V.Ya. Mendeleyev ◽  
V.A. Petrov ◽  
A.V. Yashin ◽  
A.I. Vangonen ◽  
O.K. Taganov
Keyword(s):  
Composite Material ◽  
Surface Temperature ◽  
Relative Error ◽  
Wavelength Range ◽  
Standard Sample ◽  
A Priori ◽  
Temperature Changes ◽  
Surface Temperatures ◽  
Relative Errors ◽  
Normal Emissivity

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

scholarly journals Optimization of SPECT/CT imaging protocols for quantitative and qualitative 99mTc SPECT

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Dennis Kupitz ◽  
Heiko Wissel ◽  
Jan Wuestemann ◽  
Stephanie Bluemel ◽  
Maciej Pech ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Quantitative Imaging ◽  
Scatter Correction ◽  
Reconstruction Algorithm ◽  
Weighting Factor ◽  
Quantitative Spect ◽  
Pet Ct ◽  
Spect Acquisition ◽  
The Mean ◽  
A Minor

Abstract Background The introduction of hybrid SPECT/CT devices enables quantitative imaging in SPECT, providing a methodological setup for quantitation using SPECT tracers comparable to PET/CT. We evaluated a specific quantitative reconstruction algorithm for SPECT data using a 99mTc-filled NEMA phantom. Quantitative and qualitative image parameters were evaluated for different parametrizations of the acquisition and reconstruction protocol to identify an optimized quantitative protocol. Results The reconstructed activity concentration (ACrec) and the signal-to-noise ratio (SNR) of all examined protocols (n = 16) were significantly affected by the parametrization of the weighting factor k used in scatter correction, the total number of iterations and the sphere volume (all, p < 0.0001). The two examined SPECT acquisition protocols (with 60 or 120 projections) had a minor impact on the ACrec and no significant impact on the SNR. In comparison to the known AC, the use of default scatter correction (k = 0.47) or object-specific scatter correction (k = 0.18) resulted in an underestimation of ACrec in the largest sphere volume (26.5 ml) by − 13.9 kBq/ml (− 16.3%) and − 7.1 kBq/ml (− 8.4%), respectively. An increase in total iterations leads to an increase in estimated AC and a decrease in SNR. The mean difference between ACrec and known AC decreased with an increasing number of total iterations (e.g., for 20 iterations (2 iterations/10 subsets) = − 14.6 kBq/ml (− 17.1%), 240 iterations (24i/10s) = − 8.0 kBq/ml (− 9.4%), p < 0.0001). In parallel, the mean SNR decreased significantly from 2i/10s to 24i/10s by 76% (p < 0.0001). Conclusion Quantitative SPECT imaging is feasible with the used reconstruction algorithm and hybrid SPECT/CT, and its consistent implementation in diagnostics may provide perspectives for quantification in routine clinical practice (e.g., assessment of bone metabolism). When combining quantitative analysis and diagnostic imaging, we recommend using two different reconstruction protocols with task-specific optimized setups (quantitative vs. qualitative reconstruction). Furthermore, individual scatter correction significantly improves both quantitative and qualitative results.

scholarly journals On strongly nonlinear gravity waves in a vertically sheared atmosphere

2020 ◽  
Vol 6 (1) ◽  
pp. 63-74
Author(s):  
Mark Schlutow ◽  
Georg S. Voelker
Keyword(s):  
Gravity Waves ◽  
Lower Layer ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Necessary Condition ◽  
Mean Flow ◽  
Individual Layer ◽  
Strongly Nonlinear ◽  
The Mean ◽  
The Stability

Abstract We investigate strongly nonlinear stationary gravity waves which experience refraction due to a thin vertical shear layer of horizontal background wind. The velocity amplitude of the waves is of the same order of magnitude as the background flow and hence the self-induced mean flow alters the modulation properties to leading order. In this theoretical study, we show that the stability of such a refracted wave depends on the classical modulation stability criterion for each individual layer, above and below the shearing. Additionally, the stability is conditioned by novel instability criteria providing bounds on the mean-flow horizontal wind and the amplitude of the wave. A necessary condition for instability is that the mean-flow horizontal wind in the upper layer is stronger than the wind in the lower layer.

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