Pierre Dussarrat, B. Theodore, D. Coppens, C. Standfuss, B. Tournier
Abstract. Atmospheric remote spectrometry from space has become in the last 20 years a key component of the Earth monitoring system: their large coverage and deci-kelvin stability have demonstrated their usefulness for weather prediction, atmospheric composition monitoring as well as climate monitoring. It is thus critical to investigate the possible sources of errors associated to this technique. One of them is the so-called "ringing error" that appears in Fourier transform spectrometers when the instrument transmission varies at the scale of the spectral resolution. This paper exposes the theoretical basis of this particular type of radiometric uncertainty. Its sensitivity to instrumental parameters as well as the impact on the radiometrically calibrated measurements is assessed in the context of atmospheric infrared sounding using Fourier transform spectrometers. It is shown that this error is an intrinsic feature of such instruments that could safely be ignored in early-generation instruments but will have to be taken into account in the new generation ones as it can yield a significant degradation of the radiometric error budget.
{"title":"Introduction to the ringing effect in satellite hyperspectral atmospheric spectrometry","authors":"Pierre Dussarrat, B. Theodore, D. Coppens, C. Standfuss, B. Tournier","doi":"10.5194/AMT-2021-121","DOIUrl":"https://doi.org/10.5194/AMT-2021-121","url":null,"abstract":"Abstract. Atmospheric remote spectrometry from space has become in the last 20 years a key component of the Earth monitoring system: their large coverage and deci-kelvin stability have demonstrated their usefulness for weather prediction, atmospheric composition monitoring as well as climate monitoring. It is thus critical to investigate the possible sources of errors associated to this technique. One of them is the so-called \"ringing error\" that appears in Fourier transform spectrometers when the instrument transmission varies at the scale of the spectral resolution. This paper exposes the theoretical basis of this particular type of radiometric uncertainty. Its sensitivity to instrumental parameters as well as the impact on the radiometrically calibrated measurements is assessed in the context of atmospheric infrared sounding using Fourier transform spectrometers. It is shown that this error is an intrinsic feature of such instruments that could safely be ignored in early-generation instruments but will have to be taken into account in the new generation ones as it can yield a significant degradation of the radiometric error budget.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116079637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Longjiang Li, Suqin Wu, Kefei Zhang, Xiaoming Wang, Wang Li, Zhentian Shen, Dantong Zhu, Qimin He, Moufeng Wan
Abstract. The quality of the zenith hydrostatic delay (ZHD) could significantly affect the accuracy of the zenith wet delay (ZWD) of the Global Navigation Satellite System (GNSS) signal, and from the ZWD precipitable water vapor (PWV) can be obtained. The ZHD is usually obtained from a standard model – a function of surface pressure over the GNSS station. When PWV is retrieved from the GNSS stations that are not equipped with dedicated meteorological sensors for surface pressure measurements, blind models, e.g., the Global Pressure and Temperature (GPT) models, are commonly used to determine the pressures for these GNSS stations. Due to the limited accuracies of the GPT models, the ZHD obtained from the model-derived pressure value is also of low accuracy, especially in mid- and high-latitude regions. To address this issue, a new ZHD model, named as GZHD, was investigated for real-time retrieval of PWV from GNSS in this study. The ratio of the ZHD to the zenith total delay (ZTD) was first calculated using sounding data from 505 globally distributed radiosonde stations selected from the stations that had over 5,000 samples. It was found that the temporal variation in the ratio was dominated by the annual and semiannual components, and the amplitude of the annual variation was dependent upon the geographical location of the station. Based on the relationship between the ZHD and ZTD, the new model, GZHD, was developed using the back propagation artificial neural network (BP-ANN) method which took the ZTD as an input variable. The 20-year (2000–2019) radiosonde data at 558 global stations and the 9-year (2006–2014) COSMIC-1 data, which were also globally distributed, were used as the training samples of the new model. The GZHD model was evaluated using two sets of references: the integrated ZHD obtained from sounding data over 137 radiosonde stations and ERA5 reanalysis data. The performance of the new model was also compared with GPT3. Results showed the new model outperformed GPT3, especially in mid- and high-latitude regions. When radiosonde-derived ZHD was used as the reference, the accuracy, which was measured by the root mean square error (RMSE) of the samples, of the GZHD-derived ZHD, was 22 % better than the GTP3-derived ones. When ERA5-derived ZHD was used as the reference, the accuracy of the GZHD-derived ZHD was 35 % better than GPT3-derived ZHD. In addition, the PWV derived from 93 GNSS stations resulting from GZHD-derived ZHD was also evaluated and the result indicated that the accuracy of the PWV was improved by 23 %.
{"title":"A New ZHD Model for Real-Time Retrievals of GNSS-PWV","authors":"Longjiang Li, Suqin Wu, Kefei Zhang, Xiaoming Wang, Wang Li, Zhentian Shen, Dantong Zhu, Qimin He, Moufeng Wan","doi":"10.5194/AMT-2021-113","DOIUrl":"https://doi.org/10.5194/AMT-2021-113","url":null,"abstract":"Abstract. The quality of the zenith hydrostatic delay (ZHD) could significantly affect the accuracy of the zenith wet delay (ZWD) of the Global Navigation Satellite System (GNSS) signal, and from the ZWD precipitable water vapor (PWV) can be obtained. The ZHD is usually obtained from a standard model – a function of surface pressure over the GNSS station. When PWV is retrieved from the GNSS stations that are not equipped with dedicated meteorological sensors for surface pressure measurements, blind models, e.g., the Global Pressure and Temperature (GPT) models, are commonly used to determine the pressures for these GNSS stations. Due to the limited accuracies of the GPT models, the ZHD obtained from the model-derived pressure value is also of low accuracy, especially in mid- and high-latitude regions. To address this issue, a new ZHD model, named as GZHD, was investigated for real-time retrieval of PWV from GNSS in this study. The ratio of the ZHD to the zenith total delay (ZTD) was first calculated using sounding data from 505 globally distributed radiosonde stations selected from the stations that had over 5,000 samples. It was found that the temporal variation in the ratio was dominated by the annual and semiannual components, and the amplitude of the annual variation was dependent upon the geographical location of the station. Based on the relationship between the ZHD and ZTD, the new model, GZHD, was developed using the back propagation artificial neural network (BP-ANN) method which took the ZTD as an input variable. The 20-year (2000–2019) radiosonde data at 558 global stations and the 9-year (2006–2014) COSMIC-1 data, which were also globally distributed, were used as the training samples of the new model. The GZHD model was evaluated using two sets of references: the integrated ZHD obtained from sounding data over 137 radiosonde stations and ERA5 reanalysis data. The performance of the new model was also compared with GPT3. Results showed the new model outperformed GPT3, especially in mid- and high-latitude regions. When radiosonde-derived ZHD was used as the reference, the accuracy, which was measured by the root mean square error (RMSE) of the samples, of the GZHD-derived ZHD, was 22 % better than the GTP3-derived ones. When ERA5-derived ZHD was used as the reference, the accuracy of the GZHD-derived ZHD was 35 % better than GPT3-derived ZHD. In addition, the PWV derived from 93 GNSS stations resulting from GZHD-derived ZHD was also evaluated and the result indicated that the accuracy of the PWV was improved by 23 %.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116855441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Werner, N. Livesey, M. Schwartz, W. Read, M. Santee, G. Wind
Abstract. An improved cloud detection algorithm for the Aura Microwave Limb Sounder (MLS) is presented. This new algorithm is based on a feedforward artificial neural network and uses as input, for each MLS limb scan, a vector consisting of 1,710 brightness temperatures provided by MLS observations from 15 different tangent altitudes and up to 13 spectral channels in each of 10 different MLS bands. The model has been trained on global cloud properties reported by Aqua’s Moderate Resolution Imaging Spectroradiometer (MODIS). In total, the colocated MLS-MODIS data set consists of 162,117 combined scenes sampled on 208 days over 2005–2020. We show that the algorithm can correctly classify > 96 % of cloudy and clear instances for previously unseen MLS scans. A comparison to the current MLS cloudiness flag used in “Level 2” processing reveals a huge improvement in classification performance. For all profiles in the colocated MLS-MODIS data set, the algorithm successfully detects 97.8 % of profiles affected by clouds, up from 15.8 % for the Level 2 flagging. Meanwhile, false positives reported for actually clear profiles are reduced to 1.7 %, down from 6.2 % in Level 2. The classification performance is not dependent on geolocation. The new cloudiness flag is applied to determine average global cloud cover between 2015 and 2019, successfully reproducing the spatial patterns of mid-level to high clouds reported in previous studies. It is also applied to four example cloud fields to illustrate the reliable performance for different cloud structures with varying degrees of complexity. Training a similar model on MODIS-retrieved cloud top pressure yields reliable predictions with correlation coefficients greater than 0.99. The combination of cloudiness flag and predicted cloud top pressure provides the means to identify MLS profiles in the presence of high-reaching convection.
{"title":"Improved cloud detection for the Aura Microwave Limb Sounder: Training an artificial neural network on colocated MLS and Aqua-MODIS data","authors":"F. Werner, N. Livesey, M. Schwartz, W. Read, M. Santee, G. Wind","doi":"10.5194/AMT-2021-146","DOIUrl":"https://doi.org/10.5194/AMT-2021-146","url":null,"abstract":"Abstract. An improved cloud detection algorithm for the Aura Microwave Limb Sounder (MLS) is presented. This new algorithm is based on a feedforward artificial neural network and uses as input, for each MLS limb scan, a vector consisting of 1,710 brightness temperatures provided by MLS observations from 15 different tangent altitudes and up to 13 spectral channels in each of 10 different MLS bands. The model has been trained on global cloud properties reported by Aqua’s Moderate Resolution Imaging Spectroradiometer (MODIS). In total, the colocated MLS-MODIS data set consists of 162,117 combined scenes sampled on 208 days over 2005–2020. We show that the algorithm can correctly classify > 96 % of cloudy and clear instances for previously unseen MLS scans. A comparison to the current MLS cloudiness flag used in “Level 2” processing reveals a huge improvement in classification performance. For all profiles in the colocated MLS-MODIS data set, the algorithm successfully detects 97.8 % of profiles affected by clouds, up from 15.8 % for the Level 2 flagging. Meanwhile, false positives reported for actually clear profiles are reduced to 1.7 %, down from 6.2 % in Level 2. The classification performance is not dependent on geolocation. The new cloudiness flag is applied to determine average global cloud cover between 2015 and 2019, successfully reproducing the spatial patterns of mid-level to high clouds reported in previous studies. It is also applied to four example cloud fields to illustrate the reliable performance for different cloud structures with varying degrees of complexity. Training a similar model on MODIS-retrieved cloud top pressure yields reliable predictions with correlation coefficients greater than 0.99. The combination of cloudiness flag and predicted cloud top pressure provides the means to identify MLS profiles in the presence of high-reaching convection.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"R-26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126627280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Total precipitable water (TPW) in the atmosphere is the vertically integrated amount of atmospheric water in all of its phases. TPW is a valuable predictor for weather forecasting, and it is routinely measured using radiosondes, ground-based global positioning systems (GPS), sun photometers, or microwave radiometers. The use of these sophisticated instruments limits the number of TPW measurement sites, which affects the accuracy of forecast models in regards to storm formation, strength, and the potential for precipitation. We have analyzed this relationship for the much drier climate zone found in the Desert Southwest, specifically over Socorro, New Mexico (34° N, 107° W). Daily measurements of the ground and zenith sky temperatures have been made at Socorro for two complete annual cycles using infrared thermal sensors. Radiosonde TPW measurements from National Weather Service stations located in nearby Albuquerque, and Santa Theresa, New Mexico, are input into our dataset and analysed via a newly developed computational tool. Our results show that an exponential relationship between TPW and zenith sky temperature also holds for the Desert Southwest, but with parameters that are different than those obtained for the Gulf Coast. Model simulations can accurately reproduce the observed relationship between TPW and temperature, and the results suggest that half of the signal in temperature is directly related to direct changes in opacity due to changes in TPW, while the other half is due to changes in air temperature that usually accompany changes in TPW.
{"title":"Atmospheric Precipitable Water and its Correlation with Clear Sky Infrared Temperature Observations","authors":"Vicki Kelsey, S. Riley, K. Minschwaner","doi":"10.5194/AMT-2021-130","DOIUrl":"https://doi.org/10.5194/AMT-2021-130","url":null,"abstract":"Abstract. Total precipitable water (TPW) in the atmosphere is the vertically integrated amount of atmospheric water in all of its phases. TPW is a valuable predictor for weather forecasting, and it is routinely measured using radiosondes, ground-based global positioning systems (GPS), sun photometers, or microwave radiometers. The use of these sophisticated instruments limits the number of TPW measurement sites, which affects the accuracy of forecast models in regards to storm formation, strength, and the potential for precipitation. We have analyzed this relationship for the much drier climate zone found in the Desert Southwest, specifically over Socorro, New Mexico (34° N, 107° W). Daily measurements of the ground and zenith sky temperatures have been made at Socorro for two complete annual cycles using infrared thermal sensors. Radiosonde TPW measurements from National Weather Service stations located in nearby Albuquerque, and Santa Theresa, New Mexico, are input into our dataset and analysed via a newly developed computational tool. Our results show that an exponential relationship between TPW and zenith sky temperature also holds for the Desert Southwest, but with parameters that are different than those obtained for the Gulf Coast. Model simulations can accurately reproduce the observed relationship between TPW and temperature, and the results suggest that half of the signal in temperature is directly related to direct changes in opacity due to changes in TPW, while the other half is due to changes in air temperature that usually accompany changes in TPW.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123704023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Song Liang, Hu Xiong, W. Feng, Zhaoai Yan, Qingchen Xu, Tu Cui
Abstract. The Stratospheric Environmental respoNses to Solar stORms (SENSOR) campaign investigates the influence of solar storms on the stratosphere. This campaign employs a long-duration zero-pressure balloon as a platform to carry multiple types of payloads during a series of flight experiments in the mid-latitude stratosphere from 2019 to 2022. This article describes the development and testing of an acoustic anemometer for obtaining in situ wind measurements along the balloon trajectory. Developing this anemometer was necessary, as there is no existing commercial off-the-shelf product, to the authors' knowledge, capable of obtaining in situ wind measurements on a high-altitude balloon or other similar floating platform in the stratosphere. The anemometer is also equipped with temperature, pressure, and humidity sensors from a Temperature-Pressure-Humidity measurement module, inherited from a radiosonde developed for sounding balloons. The acoustic anemometer and other sensors were used in a flight experiment of the SENSOR campaign that took place in the Da chaidan District (95.37° E, 37.74° N) on 4 September 2019. The zonal and meridional wind speed observations, which were obtained during level flight at an altitude exceeding 20 km, are presented. This is the first time that in situ wind measurements were obtained during level flight at this altitude. In addition to wind speed measurements, temperature, pressure, and relative humidity measurements during ascent are compared to observations from a nearby radiosonde launched four hours earlier. Further analysis of the wind data will presented in a subsequent publication. The problems experienced by the acoustic anemometer during the 2019 experiment show that the acoustic anemometer must be improved for future experiments in the SENSOR campaign.
{"title":"Development of an in situ Acoustic Anemometer to Measure Wind in the Stratosphere for SENSOR","authors":"Song Liang, Hu Xiong, W. Feng, Zhaoai Yan, Qingchen Xu, Tu Cui","doi":"10.5194/AMT-2021-76","DOIUrl":"https://doi.org/10.5194/AMT-2021-76","url":null,"abstract":"Abstract. The Stratospheric Environmental respoNses to Solar stORms (SENSOR) campaign investigates the influence of solar storms on the stratosphere. This campaign employs a long-duration zero-pressure balloon as a platform to carry multiple types of payloads during a series of flight experiments in the mid-latitude stratosphere from 2019 to 2022. This article describes the development and testing of an acoustic anemometer for obtaining in situ wind measurements along the balloon trajectory. Developing this anemometer was necessary, as there is no existing commercial off-the-shelf product, to the authors' knowledge, capable of obtaining in situ wind measurements on a high-altitude balloon or other similar floating platform in the stratosphere. The anemometer is also equipped with temperature, pressure, and humidity sensors from a Temperature-Pressure-Humidity measurement module, inherited from a radiosonde developed for sounding balloons. The acoustic anemometer and other sensors were used in a flight experiment of the SENSOR campaign that took place in the Da chaidan District (95.37° E, 37.74° N) on 4 September 2019. The zonal and meridional wind speed observations, which were obtained during level flight at an altitude exceeding 20 km, are presented. This is the first time that in situ wind measurements were obtained during level flight at this altitude. In addition to wind speed measurements, temperature, pressure, and relative humidity measurements during ascent are compared to observations from a nearby radiosonde launched four hours earlier. Further analysis of the wind data will presented in a subsequent publication. The problems experienced by the acoustic anemometer during the 2019 experiment show that the acoustic anemometer must be improved for future experiments in the SENSOR campaign.","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124199073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
X. Shang, T. Mielonen, A. Lipponen, E. Giannakaki, A. Leskinen, V. Buchard, A. Darmenov, Antti Kukkurainen, A. Arola, E. O'connor, A. Hirsikko, M. Komppula
Abstract. Layers of biomass burning aerosol particles were observed in the lower troposphere, at 2 to 5 km height on 4 to 6 June 2019, over Kuopio, Finland. These long-range-transported smoke particles originated from a Canadian wildfire event. The most pronounced smoke plume detected on 5 June was intensively investigated. Optical properties were retrieved from the multi-wavelength Raman polarization lidar PollyXT. Particle linear depolarization ratios of this plume were measured to be 0.08 ± 0.02 at 355 nm and 0.05 ± 0.01 at 532 nm which were slightly higher than the values given in the literature. Non-spherical shaped aged smoke particles and/or the mixing with a small amount of fine dust particles could cause the observed increase in the particle linear depolarization ratios. Lidar ratios were derived as 47 ± 5 sr at 355 nm and 71 ± 5 sr at 532 nm. A complete ceilometer data processing for a Vaisala CL51 is presented, including the water vapor correction for high latitude for the first time, from sensor provided attenuated backscatter coefficient to particle mass concentration. A combined lidar and sun-photometer approach (based on AERONET products) is applied for mass concentration estimations. Mass concentrations were estimated from both PollyXT and the ceilometer CL51 observations, which were of the order of ~ 30 µg m−3 in the morning and decreased to ~ 20 µg m−3 in the night. A difference of ~ 30% was found between PollyXT and CL51 estimated mass concentrations. The mass retrievals were discussed and compared with the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) meteorological and aerosol reanalysis. The inclusion of dust in the retrieved mass concentration slightly improved the correspondence between the observations and the MERRA-2 simulations.
摘要2019年6月4日至6日，在芬兰库奥皮奥上空对流层下层2至5公里高度观测到生物质燃烧气溶胶颗粒层。这些远距离传播的烟雾颗粒来自加拿大的一场野火。对6月5日探测到的最明显的烟羽进行了深入调查。从多波长拉曼偏振激光雷达PollyXT中获取光学特性。该羽流的粒子线退极化比在355 nm处为0.08±0.02，在532 nm处为0.05±0.01，略高于文献给出的值。非球形老化烟尘粒子和/或与少量细尘粒子混合会导致观测到的粒子线性退极化比增大。激光雷达比分别为355 nm处的47±5 sr和532 nm处的71±5 sr。本文介绍了Vaisala CL51的完整的ceilometer数据处理，包括首次对高纬度的水汽进行校正，从传感器提供的衰减后向散射系数到粒子质量浓度。采用激光雷达和太阳光度计相结合的方法(基于AERONET产品)进行质量浓度估计。通过polyxt和ceilometer CL51的观测，估计了质量浓度，早上约为~ 30µg m−3，晚上降至~ 20µg m−3。polyxt和CL51的估计质量浓度相差约30%。并与MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2)气象和气溶胶再分析进行了讨论和比较。在获取的质量浓度中包含尘埃略微改善了观测结果与MERRA-2模拟之间的对应关系。
{"title":"Canadian biomass burning aerosols observations from a multi-wavelength Raman polarization lidar and a ceilometer in Finland","authors":"X. Shang, T. Mielonen, A. Lipponen, E. Giannakaki, A. Leskinen, V. Buchard, A. Darmenov, Antti Kukkurainen, A. Arola, E. O'connor, A. Hirsikko, M. Komppula","doi":"10.5194/AMT-2021-139","DOIUrl":"https://doi.org/10.5194/AMT-2021-139","url":null,"abstract":"Abstract. Layers of biomass burning aerosol particles were observed in the lower troposphere, at 2 to 5 km height on 4 to 6 June 2019, over Kuopio, Finland. These long-range-transported smoke particles originated from a Canadian wildfire event. The most pronounced smoke plume detected on 5 June was intensively investigated. Optical properties were retrieved from the multi-wavelength Raman polarization lidar PollyXT. Particle linear depolarization ratios of this plume were measured to be 0.08 ± 0.02 at 355 nm and 0.05 ± 0.01 at 532 nm which were slightly higher than the values given in the literature. Non-spherical shaped aged smoke particles and/or the mixing with a small amount of fine dust particles could cause the observed increase in the particle linear depolarization ratios. Lidar ratios were derived as 47 ± 5 sr at 355 nm and 71 ± 5 sr at 532 nm. A complete ceilometer data processing for a Vaisala CL51 is presented, including the water vapor correction for high latitude for the first time, from sensor provided attenuated backscatter coefficient to particle mass concentration. A combined lidar and sun-photometer approach (based on AERONET products) is applied for mass concentration estimations. Mass concentrations were estimated from both PollyXT and the ceilometer CL51 observations, which were of the order of ~ 30 µg m−3 in the morning and decreased to ~ 20 µg m−3 in the night. A difference of ~ 30% was found between PollyXT and CL51 estimated mass concentrations. The mass retrievals were discussed and compared with the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) meteorological and aerosol reanalysis. The inclusion of dust in the retrieved mass concentration slightly improved the correspondence between the observations and the MERRA-2 simulations.","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134008621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
René Sedlak, P. Hannawald, C. Schmidt, S. Wüst, M. Bittner, S. Stanič
Abstract. We analysed 286 nights of data from the OH* airglow imager FAIM 3 (Fast Airglow IMager) acquired at Otlica Observatory (45.93 °N, 13.91 °E), Slovenia between 26 October 2017 and 6 June 2019. Measurements have been performed with a spatial resolution of 24 m/pixel and a temporal resolution of 2.8 s. A two-dimensional Fast Fourier transform is applied to the image data to derive horizontal wavelengths between 48 m and 4.5 km in the upper mesosphere / lower thermosphere (UMLT) region. In contrast to the statistics of larger scale gravity waves (horizontal wavelength up to ca. 50 km) we find a more isotropic distribution of directions of propagation, pointing to the presence of wave structures created above the stratospheric wind fields. A weak seasonal tendency of a majority of waves propagating eastward (westward) during winter (summer) may be due to secondary gravity waves originating from breaking primary waves in the stratosphere. We also observe an increased southward propagation during summer, which we interpret as an enhanced contribution of secondary gravity waves created as a consequence of primary wave filtering by the meridional mesospheric circulation. Furthermore, observations of turbulent vortices allowed the estimation of eddy diffusion coefficients in the UMLT from image sequences in 45 cases. Values range around 103–104 m2s-1 and mostly agree with literature. Turbulently dissipated energy is derived taking into account values of the Brunt-Väisälä frequency based on TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics, Sounding of the Atmosphere using Broadband Emission Radiometry) measurements. Energy dissipation rates range between 0.63 W/kg and 14.21 W/kg leading to an approximated maximum heating of 0.2–6.3 K per turbulence event. These are in the same range as the daily chemical heating rates, which apparently stresses the importance of dynamical energy conversion in the UMLT.
{"title":"Gravity wave instability structures and turbulence from more than one and a half years of OH* airglow imager observations in Slovenia","authors":"René Sedlak, P. Hannawald, C. Schmidt, S. Wüst, M. Bittner, S. Stanič","doi":"10.5194/AMT-2021-134","DOIUrl":"https://doi.org/10.5194/AMT-2021-134","url":null,"abstract":"Abstract. We analysed 286 nights of data from the OH* airglow imager FAIM 3 (Fast Airglow IMager) acquired at Otlica Observatory (45.93 °N, 13.91 °E), Slovenia between 26 October 2017 and 6 June 2019. Measurements have been performed with a spatial resolution of 24 m/pixel and a temporal resolution of 2.8 s. A two-dimensional Fast Fourier transform is applied to the image data to derive horizontal wavelengths between 48 m and 4.5 km in the upper mesosphere / lower thermosphere (UMLT) region. In contrast to the statistics of larger scale gravity waves (horizontal wavelength up to ca. 50 km) we find a more isotropic distribution of directions of propagation, pointing to the presence of wave structures created above the stratospheric wind fields. A weak seasonal tendency of a majority of waves propagating eastward (westward) during winter (summer) may be due to secondary gravity waves originating from breaking primary waves in the stratosphere. We also observe an increased southward propagation during summer, which we interpret as an enhanced contribution of secondary gravity waves created as a consequence of primary wave filtering by the meridional mesospheric circulation. Furthermore, observations of turbulent vortices allowed the estimation of eddy diffusion coefficients in the UMLT from image sequences in 45 cases. Values range around 103–104 m2s-1 and mostly agree with literature. Turbulently dissipated energy is derived taking into account values of the Brunt-Väisälä frequency based on TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics, Sounding of the Atmosphere using Broadband Emission Radiometry) measurements. Energy dissipation rates range between 0.63 W/kg and 14.21 W/kg leading to an approximated maximum heating of 0.2–6.3 K per turbulence event. These are in the same range as the daily chemical heating rates, which apparently stresses the importance of dynamical energy conversion in the UMLT.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"206 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115443959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Marey, J. Drummond, Dylan B. A. Jones, H. Worden, M. Deeter, J. Gille, D. Mao
Abstract. The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument has been measuring global tropospheric carbon monoxide (CO) since March 2000, providing the longest nearly continuous record of CO from space. During its long mission the data processing algorithms have been updated to improve the quality of CO retrievals and the sensitivity to the lower troposphere. Currently, MOPITT retrievals are only performed for clear-sky observations or over low clouds for ocean scenes. Compared to all observed radiances, successful retrieval rates are about 30 % and 40 % between 90° S–90° N and 60° S–60° N, respectively. Spatial seasonal variations show that while MOPITT data coverage in some places reaches 30 % in summer, this number can drop to less than 10 % in winter due to significantly increased cloud cover. Therefore, we investigate the current MOPITT cloud detection algorithm and consider approaches to increase the data coverage. The MOPITT CO total column (TC) data were modified by turning off the cloud detection scheme to allow a CO retrieval result regardless of their cloud status. Analyses of the standard CO TC product (cloud filtered) and non-standard product (non-cloud masked) were conducted for selected days. Results showed some coherent structures that were observed frequently in the non-masked CO product that were not present in the standard product and could potentially be actual CO features. A corresponding analysis of Moderate Resolution Imaging Spectroradiometer(MODIS) cloud height and cloud mask products along with MOPITT cloud flag descriptors was conducted in order to understand the cloud conditions present for these apparently physical CO features. Results show that a significant number of low cloud CO retrievals were rejected in the standard product. Those missing areas match the coherent patterns that were detected in the non-masked CO product. Many times, these structures were also seen in the Infrared Atmospheric Sounding Interferometer (IASI) CO TC product indicating actual CO plumes. Multi-angle Imaging SpectroRadiometer (MISR) data on the Terra satellite were also employed for cloud height comparison with MODIS. Comparisons of MODIS and MISR cloud height data indicate remarkable agreement which is encouraging for the possibility of incorporating MODIS cloud height in the MOPITT cloud detection scheme. Statistics of the global assessment of the potential use of MODIS cloud height shows that MOPITT data increases significantly when cloud heights less than 2 km in height are incorporated in the retrievals. However quality indices should be defined and produced to ensure sufficient retrieval quality.
摘要自2000年3月以来，对流层污染测量(MOPITT)卫星仪器一直在测量全球对流层一氧化碳(CO)，提供了从太空几乎连续的最长CO记录。在其长期任务期间，数据处理算法已得到更新，以提高CO检索的质量和对流层下层的敏感性。目前，MOPITT的检索仅用于晴空观测或低云上的海洋场景。与所有观测到的辐射相比，在90°S-90°N和60°S-60°N之间，成功的恢复率分别约为30%和40%。空间季节变化表明，一些地方的MOPITT数据覆盖率在夏季可达30%，但在冬季，由于云量的显著增加，这一数字可能下降到10%以下。因此，我们研究了现有的MOPITT云检测算法，并考虑了增加数据覆盖率的方法。通过关闭云检测方案来修改MOPITT CO总列(TC)数据，以允许CO检索结果，而不管其云状态如何。在选定的日子对标准CO TC产品(云过滤)和非标准产品(非云屏蔽)进行分析。结果表明，在非掩膜CO产品中经常观察到一些在标准产品中不存在的相干结构，这些结构可能是实际的CO特征。对中分辨率成像光谱仪(MODIS)的云高度和云掩模产品以及MOPITT云标志描述符进行了相应的分析，以了解这些明显的物理CO特征所存在的云条件。结果表明，在标准产品中有大量低云CO回收被拒绝。这些缺失的区域与在非掩膜CO产品中检测到的相干模式相匹配。在红外大气探测干涉仪(IASI) CO TC产品中也多次看到这些结构，表明实际的CO羽流。利用Terra卫星上的多角度成像光谱辐射计(MISR)数据与MODIS进行云高比较。MODIS和MISR云高数据的比较表明，两者的一致性非常显著，这对于将MODIS云高纳入MOPITT云检测方案的可能性是令人鼓舞的。对MODIS云高潜在利用的全球评估的统计表明，当在检索中纳入高度小于2公里的云高时，MOPITT数据显著增加。但是，必须定义和制定质量指标，以确保足够的检索质量。
{"title":"Enhanced MOPITT data coverage through cloud detection improvement","authors":"H. Marey, J. Drummond, Dylan B. A. Jones, H. Worden, M. Deeter, J. Gille, D. Mao","doi":"10.5194/AMT-2021-112","DOIUrl":"https://doi.org/10.5194/AMT-2021-112","url":null,"abstract":"Abstract. The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument has been measuring global tropospheric carbon monoxide (CO) since March 2000, providing the longest nearly continuous record of CO from space. During its long mission the data processing algorithms have been updated to improve the quality of CO retrievals and the sensitivity to the lower troposphere. Currently, MOPITT retrievals are only performed for clear-sky observations or over low clouds for ocean scenes. Compared to all observed radiances, successful retrieval rates are about 30 % and 40 % between 90° S–90° N and 60° S–60° N, respectively. Spatial seasonal variations show that while MOPITT data coverage in some places reaches 30 % in summer, this number can drop to less than 10 % in winter due to significantly increased cloud cover. Therefore, we investigate the current MOPITT cloud detection algorithm and consider approaches to increase the data coverage. The MOPITT CO total column (TC) data were modified by turning off the cloud detection scheme to allow a CO retrieval result regardless of their cloud status. Analyses of the standard CO TC product (cloud filtered) and non-standard product (non-cloud masked) were conducted for selected days. Results showed some coherent structures that were observed frequently in the non-masked CO product that were not present in the standard product and could potentially be actual CO features. A corresponding analysis of Moderate Resolution Imaging Spectroradiometer(MODIS) cloud height and cloud mask products along with MOPITT cloud flag descriptors was conducted in order to understand the cloud conditions present for these apparently physical CO features. Results show that a significant number of low cloud CO retrievals were rejected in the standard product. Those missing areas match the coherent patterns that were detected in the non-masked CO product. Many times, these structures were also seen in the Infrared Atmospheric Sounding Interferometer (IASI) CO TC product indicating actual CO plumes. Multi-angle Imaging SpectroRadiometer (MISR) data on the Terra satellite were also employed for cloud height comparison with MODIS. Comparisons of MODIS and MISR cloud height data indicate remarkable agreement which is encouraging for the possibility of incorporating MODIS cloud height in the MOPITT cloud detection scheme. Statistics of the global assessment of the potential use of MODIS cloud height shows that MOPITT data increases significantly when cloud heights less than 2 km in height are incorporated in the retrievals. However quality indices should be defined and produced to ensure sufficient retrieval quality.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121927270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The ability of the hyperspectral satellite based passive infrared instrument IASI to resolve Elevated Moist Layers (EMLs) within the free troposphere is investigated. EMLs are strong moisture anomalies with significant impact on the radiative heating rate profile and are thought to be coupled to freezing level detrainment of convective cells in the tropics. Based on an exemplary EML testcase and forward modelled IASI observations, it is shown that if sufficient independent humidity and temperature information is available, EMLs do not pose a blind spot for passive satellite observations, contrary to what results of Stevens et al. (2017) have indicated. To further quantify the retrieval’s ability to capture moisture anomalies, a statistical evaluation of synthetic retrievals of 1438 clear sky tropical ocean short-range forecast model atmospheres is conducted. For this purpose, a framework for the identification and characterisation of moisture anomalies, a subset of which are EMLs, is introduced. The statistical evaluation shows that retrieved moisture anomalies are on average 37 % weaker and 28 % thicker than their true counterparts, which can be attributed to the retrieval smoothing error and the fact that rather weak and narrow moisture anomalies are most frequently missed by the retrieval. Smoothing is found to also constrain the magnitude of local heating rate extremes associated with moisture anomalies, particularly for the strongest anomalies that are found in the lower to mid troposphere. In total, about 72 % of moisture anomalies in the reference dataset are found by the retrieval. Below 5 km altitude, this fraction is only on the order of 30 %, which can be attributed to the fact that lower tropospheric moisture anomalies are typically more narrow and therefore tougher to retrieve than anomalies aloft. We conclude that the retrieval of lower to mid tropospheric moisture anomalies, in particular of EMLs, is possible when the anomaly is sufficiently strong and its thickness is at least on the order of about 1.5 km. This study sets the methodological basis, from a retrieval setup and evaluation perspective, to investigate real world EMLs in IASI observations in the future.
{"title":"Are elevated moist layers a blind spot for hyperspectral infrared sounders? – A model study","authors":"M. Prange, Manfred Brath, S. Buehler","doi":"10.5194/AMT-2021-48","DOIUrl":"https://doi.org/10.5194/AMT-2021-48","url":null,"abstract":"Abstract. The ability of the hyperspectral satellite based passive infrared instrument IASI to resolve Elevated Moist Layers (EMLs) within the free troposphere is investigated. EMLs are strong moisture anomalies with significant impact on the radiative heating rate profile and are thought to be coupled to freezing level detrainment of convective cells in the tropics. Based on an exemplary EML testcase and forward modelled IASI observations, it is shown that if sufficient independent humidity and temperature information is available, EMLs do not pose a blind spot for passive satellite observations, contrary to what results of Stevens et al. (2017) have indicated. To further quantify the retrieval’s ability to capture moisture anomalies, a statistical evaluation of synthetic retrievals of 1438 clear sky tropical ocean short-range forecast model atmospheres is conducted. For this purpose, a framework for the identification and characterisation of moisture anomalies, a subset of which are EMLs, is introduced. The statistical evaluation shows that retrieved moisture anomalies are on average 37 % weaker and 28 % thicker than their true counterparts, which can be attributed to the retrieval smoothing error and the fact that rather weak and narrow moisture anomalies are most frequently missed by the retrieval. Smoothing is found to also constrain the magnitude of local heating rate extremes associated with moisture anomalies, particularly for the strongest anomalies that are found in the lower to mid troposphere. In total, about 72 % of moisture anomalies in the reference dataset are found by the retrieval. Below 5 km altitude, this fraction is only on the order of 30 %, which can be attributed to the fact that lower tropospheric moisture anomalies are typically more narrow and therefore tougher to retrieve than anomalies aloft. We conclude that the retrieval of lower to mid tropospheric moisture anomalies, in particular of EMLs, is possible when the anomaly is sufficiently strong and its thickness is at least on the order of about 1.5 km. This study sets the methodological basis, from a retrieval setup and evaluation perspective, to investigate real world EMLs in IASI observations in the future.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121084967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Minqiang Zhou, B. Langerock, C. Vigouroux, B. Dils, C. Hermans, N. Kumps, J. Metzger, E. Mahieu, Pucai C. Wang, M. D. De Mazière
Abstract. Nitric oxide (NO) is a key active trace gas in the atmosphere, which contributes to form “bad” ozone (O3) in the troposphere and to the destruction of “good” O3 in the stratosphere. In this study, we present the NO retrieval from ground-based Fourier-transform infrared (FTIR) solar absorption spectrometry measurements at a polluted site (Xianghe, China) and a background site (Maïdo, Reunion Island). The Degree Of Freedom (DOF) of the NO retrieval is 2.3 ± 0.4 (1σ) at Xianghe and 1.3 ± 0.1 at Maïdo. The high NO mole fraction near the surface at Xianghe allows us to derive tropospheric and stratospheric NO partial columns separately, albeit the tropospheric column is almost not able to be retrieved in summer (June–August) because of the high water vapor abundance. At Maïdo, the NO retrieval is only sensitive to the stratosphere. The FTIR measurements at Maïdo show that the stratospheric NO partial column increases from the early morning to about 14:00 local time and starts decreasing thereafter. The stratospheric NO partial column is large in summer as compared to winter at both sites, and the seasonal variation of the FTIR stratospheric NO partial columns is consistent with that observed by the co-located Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements. We observe a good correlation between the carbon monoxide (CO) and NO daily partial columns in the troposphere observed by the FTIR measurements at Xianghe with a correlation coefficient of 0.70, because both species have similar anthropogenic sources.
{"title":"Tropospheric and stratospheric NO retrieved from ground-based FTIR measurements","authors":"Minqiang Zhou, B. Langerock, C. Vigouroux, B. Dils, C. Hermans, N. Kumps, J. Metzger, E. Mahieu, Pucai C. Wang, M. D. De Mazière","doi":"10.5194/AMT-2021-119","DOIUrl":"https://doi.org/10.5194/AMT-2021-119","url":null,"abstract":"Abstract. Nitric oxide (NO) is a key active trace gas in the atmosphere, which contributes to form “bad” ozone (O3) in the troposphere and to the destruction of “good” O3 in the stratosphere. In this study, we present the NO retrieval from ground-based Fourier-transform infrared (FTIR) solar absorption spectrometry measurements at a polluted site (Xianghe, China) and a background site (Maïdo, Reunion Island). The Degree Of Freedom (DOF) of the NO retrieval is 2.3 ± 0.4 (1σ) at Xianghe and 1.3 ± 0.1 at Maïdo. The high NO mole fraction near the surface at Xianghe allows us to derive tropospheric and stratospheric NO partial columns separately, albeit the tropospheric column is almost not able to be retrieved in summer (June–August) because of the high water vapor abundance. At Maïdo, the NO retrieval is only sensitive to the stratosphere. The FTIR measurements at Maïdo show that the stratospheric NO partial column increases from the early morning to about 14:00 local time and starts decreasing thereafter. The stratospheric NO partial column is large in summer as compared to winter at both sites, and the seasonal variation of the FTIR stratospheric NO partial columns is consistent with that observed by the co-located Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements. We observe a good correlation between the carbon monoxide (CO) and NO daily partial columns in the troposphere observed by the FTIR measurements at Xianghe with a correlation coefficient of 0.70, because both species have similar anthropogenic sources.\u0000","PeriodicalId":441110,"journal":{"name":"Atmospheric Measurement Techniques Discussions","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124424016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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