Pub Date : 2024-02-27DOI: 10.1175/jtech-d-22-0113.1
Aiswarya Lakshmi K.K., Swaroop Sahoo, S. Biswas, V. Chandrasekar
Weather radars with dual-polarization capabilities enable the study of various characteristics of hydrometeors, including their size, shape, and orientation. Radar polarimetric measurements, coupled with Doppler information, allow for analysis in the spectral domain. This analysis can be leveraged to reveal valuable insight into the microphysics and kinematics of hydrometeors in precipitation systems. This paper uses spectral polarimetry to investigate precipitation microphysics and kinematics in storm environments observed during the RELAMPAGO field experiment in Argentina. This study uses range height indicator (RHI) scan measurements from a C-Band polarimetric Doppler weather radar deployed during the field campaign. In this work, the impact of storm dynamics on hydrometeors is studied, including the size sorting of hydrometeors due to vertical wind shear. In addition, particle microphysical processes because of aggregation and growth of ice crystals in anvil clouds, as well as graupel formation resulting from the riming of ice crystals and dendrites are also analyzed here. The presence of different particle size distributions because of the mixing of hydrometeors in a sheared environment and resulting size sorting has been reported using spectral differential reflectivity (sZdr) slope. Spectral reflectivity (sZh) and sZdr have also been used to understand the signature of ice crystal aggregation in an anvil cloud. The regions of pristine ice crystals are identified from vertical profiles of spectral polarimetric variables in anvil cloud because of sZh < 0 dB and sZdr values around 2 dB. It is also found that the growth process of these ice crystals causes a skewed bimodal sZh spectrum due to the presence of both pristine ice crystals and dry snow. Next, graupel formation due to riming has been studied and it is found that the riming process produces sZh values of about 10 dB and corresponding sZdr values of 1 dB. This positive sZdr indicates the presence of needle/columnar secondary ice particles formed by ice multiplication processes in the riming zones. Lastly, the temporal evolution of a storm is investigated by analyzing changes in hydrometeor types with time and their influence on the spectral polarimetric variables.
具有双极化功能的天气雷达可以研究水文流体的各种特征，包括它们的大小、形状和方向。雷达极化测量与多普勒信息相结合，可以进行光谱分析。利用这种分析方法，可以对降水系统中水文流体的微观物理和运动学进行深入研究。本文利用光谱极坐标法研究了在阿根廷 RELAMPAGO 实地实验中观测到的风暴环境中的降水微物理和运动学。这项研究使用了在实地活动期间部署的 C 波段偏振多普勒天气雷达的测距高度指示器（RHI）扫描测量数据。在这项工作中，研究了风暴动力学对水文介质的影响，包括垂直风切变对水文介质的大小分选。此外，本文还分析了由于砧云中冰晶的聚集和生长而导致的颗粒微物理过程，以及冰晶和树枝状物的边缘化导致的粒状凝胶的形成。有报告称，由于水介质在剪切环境中的混合以及由此产生的粒度分选，出现了不同的粒度分布，使用的是光谱微分反射率（sZdr）斜率。光谱反射率（sZh）和 sZdr 也被用来了解砧云中冰晶聚集的特征。由于 sZh < 0 dB 和 sZdr 值在 2 dB 左右，因此可以从铁砧云中的光谱偏振变量垂直剖面上识别出原始冰晶区域。研究还发现，由于原始冰晶和干雪的存在，这些冰晶的生长过程会导致偏斜的双峰 sZh 光谱。接下来，我们研究了因边缘化而形成的石榴石，发现边缘化过程产生的 sZh 值约为 10 dB，相应的 sZdr 值为 1 dB。这种正的 sZdr 值表明在边缘区存在着由冰增殖过程形成的针状/柱状次生冰粒。最后，通过分析水文流星类型随时间的变化及其对光谱极化变量的影响，研究了风暴的时间演变。
{"title":"Study of Microphysical Signatures based on Spectral Polarimetry during the RELAMPAGO Field Experiment in Argentina","authors":"Aiswarya Lakshmi K.K., Swaroop Sahoo, S. Biswas, V. Chandrasekar","doi":"10.1175/jtech-d-22-0113.1","DOIUrl":"https://doi.org/10.1175/jtech-d-22-0113.1","url":null,"abstract":"\u0000Weather radars with dual-polarization capabilities enable the study of various characteristics of hydrometeors, including their size, shape, and orientation. Radar polarimetric measurements, coupled with Doppler information, allow for analysis in the spectral domain. This analysis can be leveraged to reveal valuable insight into the microphysics and kinematics of hydrometeors in precipitation systems. This paper uses spectral polarimetry to investigate precipitation microphysics and kinematics in storm environments observed during the RELAMPAGO field experiment in Argentina. This study uses range height indicator (RHI) scan measurements from a C-Band polarimetric Doppler weather radar deployed during the field campaign. In this work, the impact of storm dynamics on hydrometeors is studied, including the size sorting of hydrometeors due to vertical wind shear. In addition, particle microphysical processes because of aggregation and growth of ice crystals in anvil clouds, as well as graupel formation resulting from the riming of ice crystals and dendrites are also analyzed here. The presence of different particle size distributions because of the mixing of hydrometeors in a sheared environment and resulting size sorting has been reported using spectral differential reflectivity (sZdr) slope. Spectral reflectivity (sZh) and sZdr have also been used to understand the signature of ice crystal aggregation in an anvil cloud. The regions of pristine ice crystals are identified from vertical profiles of spectral polarimetric variables in anvil cloud because of sZh < 0 dB and sZdr values around 2 dB. It is also found that the growth process of these ice crystals causes a skewed bimodal sZh spectrum due to the presence of both pristine ice crystals and dry snow. Next, graupel formation due to riming has been studied and it is found that the riming process produces sZh values of about 10 dB and corresponding sZdr values of 1 dB. This positive sZdr indicates the presence of needle/columnar secondary ice particles formed by ice multiplication processes in the riming zones. Lastly, the temporal evolution of a storm is investigated by analyzing changes in hydrometeor types with time and their influence on the spectral polarimetric variables.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140424328","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}
Pub Date : 2024-02-26DOI: 10.1175/jtech-d-23-0060.1
Yoshiro Yamada, Subrena Harris, Werenfrid Wimmer, Raymond Holmes, Tim Nightingale, Arrow Lee, Nis Jepsen, Nicole Morgan, F. Göttsche, R. Niclós, Martín Perelló, V. García-Santos, Craig Donlon, Nigel Fox
An international comparison of field-deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted during two weeks in June 2022. The comparison comprised a laboratory comparison and a field comparison. The field comparison of the radiometers took place on the second week at a seaside pier on the south coast of England. Six thermal infrared radiometers were compared against each other while continuously viewing the closely adjacent surface of the sea from the end of the pier. This paper reports the results of this field comparison. All participants’ radiometers agreed with the reference value, evaluated as the simple mean of the participant reported values, within the claimed uncertainties. The SSTskin variation during the five-day period was within 3 °C around 18.3 °C, which is two times larger in range than in the previous comparison in 2016, while the mean of the difference from the reference value over the period evaluated for each participant, was found to be within 0.07 °C, which is a two-times improvement on the previous results. During the comparison an insignificant but noticeable abrupt shift in measured value occurred in one of the radiometers, which could not have been detected without comparison with other instruments. This demonstrated the effectiveness of having long term stable internal reference sources in the instrument, a feature this particular radiometer did not have. The combined results from the laboratory comparison and the field comparison contribute to improve confidence in the retrieved SSTskin.
{"title":"2022 CEOS International Thermal Infrared Radiometer Comparison: Part II: Field Comparison of Radiometers","authors":"Yoshiro Yamada, Subrena Harris, Werenfrid Wimmer, Raymond Holmes, Tim Nightingale, Arrow Lee, Nis Jepsen, Nicole Morgan, F. Göttsche, R. Niclós, Martín Perelló, V. García-Santos, Craig Donlon, Nigel Fox","doi":"10.1175/jtech-d-23-0060.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0060.1","url":null,"abstract":"\u0000An international comparison of field-deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted during two weeks in June 2022. The comparison comprised a laboratory comparison and a field comparison. The field comparison of the radiometers took place on the second week at a seaside pier on the south coast of England. Six thermal infrared radiometers were compared against each other while continuously viewing the closely adjacent surface of the sea from the end of the pier. This paper reports the results of this field comparison.\u0000All participants’ radiometers agreed with the reference value, evaluated as the simple mean of the participant reported values, within the claimed uncertainties. The SSTskin variation during the five-day period was within 3 °C around 18.3 °C, which is two times larger in range than in the previous comparison in 2016, while the mean of the difference from the reference value over the period evaluated for each participant, was found to be within 0.07 °C, which is a two-times improvement on the previous results.\u0000During the comparison an insignificant but noticeable abrupt shift in measured value occurred in one of the radiometers, which could not have been detected without comparison with other instruments. This demonstrated the effectiveness of having long term stable internal reference sources in the instrument, a feature this particular radiometer did not have.\u0000The combined results from the laboratory comparison and the field comparison contribute to improve confidence in the retrieved SSTskin.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140429713","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}
Pub Date : 2024-02-26DOI: 10.1175/jtech-d-23-0059.1
Yoshiro Yamada, Subrena Harris, Michael Hayes, Rob Simpson, Werenfrid Wimmer, Raymond Holmes, Tim Nightingale, Arrow Lee, Nis Jepsen, Nicole Morgan, F. Göttsche, R. Niclós, Martín Perelló, Craig Donlon, Nigel Fox
An international comparison of field deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted in June 2022. The campaign comprised a laboratory and a field comparison. In the laboratory part the radiometers were compared against reference standard blackbodies, while the same was done with the blackbodies used for the calibration of the radiometers against a transfer standard radiometer. Reference values were provided by the National Physical Laboratory (NPL), traceable to the primary standard on the International Temperature Scale of 1990. This was followed by the field comparison at a seaside pier on the south coast of England, where the radiometers were compared against each other while viewing the closely adjacent surface of the sea. This paper reports the results of the laboratory comparison of radiometers and blackbodies. For the blackbody comparison, the brightness temperature of the blackbody reported by the participants agreed with the reference value measured by the NPL transfer standard radiometer within the uncertainties for all temperatures and for all blackbodies. For the radiometer comparison, the temperature range of most interest from the SSTskin retrieval point of view is 10 °C to 30 °C, and in this temperature range, and up to the maximum comparison temperature of 50 °C, all participants’ reported results were in agreement with the reference. On the other hand, below 0 °C the reported values showed divergence from the reference and the differences exceeded the uncertainties. The divergence shows there is room for improvement in uncertainty estimation at lower temperatures, although it will have limited implication in the SSTskin retrieval.
{"title":"2022 CEOS International Thermal Infrared Radiometer Comparison: Part I: Laboratory Comparison of Radiometers and Blackbodies","authors":"Yoshiro Yamada, Subrena Harris, Michael Hayes, Rob Simpson, Werenfrid Wimmer, Raymond Holmes, Tim Nightingale, Arrow Lee, Nis Jepsen, Nicole Morgan, F. Göttsche, R. Niclós, Martín Perelló, Craig Donlon, Nigel Fox","doi":"10.1175/jtech-d-23-0059.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0059.1","url":null,"abstract":"\u0000An international comparison of field deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted in June 2022. The campaign comprised a laboratory and a field comparison. In the laboratory part the radiometers were compared against reference standard blackbodies, while the same was done with the blackbodies used for the calibration of the radiometers against a transfer standard radiometer. Reference values were provided by the National Physical Laboratory (NPL), traceable to the primary standard on the International Temperature Scale of 1990. This was followed by the field comparison at a seaside pier on the south coast of England, where the radiometers were compared against each other while viewing the closely adjacent surface of the sea. This paper reports the results of the laboratory comparison of radiometers and blackbodies.\u0000For the blackbody comparison, the brightness temperature of the blackbody reported by the participants agreed with the reference value measured by the NPL transfer standard radiometer within the uncertainties for all temperatures and for all blackbodies. For the radiometer comparison, the temperature range of most interest from the SSTskin retrieval point of view is 10 °C to 30 °C, and in this temperature range, and up to the maximum comparison temperature of 50 °C, all participants’ reported results were in agreement with the reference. On the other hand, below 0 °C the reported values showed divergence from the reference and the differences exceeded the uncertainties. The divergence shows there is room for improvement in uncertainty estimation at lower temperatures, although it will have limited implication in the SSTskin retrieval.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140430916","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}
Pub Date : 2024-02-23DOI: 10.1175/jtech-d-23-0090.1
K. Virts, Timothy J. Lang, D. Buechler, P. Bitzer
Identical Lightning Imaging Sensors aboard the Tropical Rainfall Measuring Mission satellite (TRMM LIS, 1998–2015) and International Space Station (ISS LIS, 2017–present) have provided over two decades of lightning observations over the global tropics, with ISS LIS extending coverage into the mid-latitudes. Quantifying the detection performance of both LIS sensors is a necessary step toward generating a combined LIS climatological record and accurately combining LIS data with lightning detections from other sensors and networks. We compare lightning observations from both LIS sensors with reference sources including the Geostationary Lightning Mapper (GLM) and ground-based Earth Networks Total Lightning Network (ENTLN), Earth Networks Global Lightning Network (ENGLN), National Lightning Detection Network (NLDN), and Global Lightning Dataset (GLD360). Instead of a relative detection efficiency (DE) approach that assumes perfect performance of the reference sensor, we employ a Bayesian approach to estimate the upper limit of the absolute DE (ADE) of each system being analyzed. The results of this analysis illustrate the geographical pattern of ADE as well as its diurnal cycle and yearly evolution. Reference network ADE increased by ~15–30% during the TRMM era, leading to a decline in TRMM LIS ADE. ISS LIS flash ADE has been relatively consistent at 61–65%, about 4–5% lower than TRMM LIS at the end of its lifetime.
{"title":"Bayesian analysis of the detection performance of the Lightning Imaging Sensors","authors":"K. Virts, Timothy J. Lang, D. Buechler, P. Bitzer","doi":"10.1175/jtech-d-23-0090.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0090.1","url":null,"abstract":"\u0000Identical Lightning Imaging Sensors aboard the Tropical Rainfall Measuring Mission satellite (TRMM LIS, 1998–2015) and International Space Station (ISS LIS, 2017–present) have provided over two decades of lightning observations over the global tropics, with ISS LIS extending coverage into the mid-latitudes. Quantifying the detection performance of both LIS sensors is a necessary step toward generating a combined LIS climatological record and accurately combining LIS data with lightning detections from other sensors and networks. We compare lightning observations from both LIS sensors with reference sources including the Geostationary Lightning Mapper (GLM) and ground-based Earth Networks Total Lightning Network (ENTLN), Earth Networks Global Lightning Network (ENGLN), National Lightning Detection Network (NLDN), and Global Lightning Dataset (GLD360). Instead of a relative detection efficiency (DE) approach that assumes perfect performance of the reference sensor, we employ a Bayesian approach to estimate the upper limit of the absolute DE (ADE) of each system being analyzed. The results of this analysis illustrate the geographical pattern of ADE as well as its diurnal cycle and yearly evolution. Reference network ADE increased by ~15–30% during the TRMM era, leading to a decline in TRMM LIS ADE. ISS LIS flash ADE has been relatively consistent at 61–65%, about 4–5% lower than TRMM LIS at the end of its lifetime.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140435586","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}
Pub Date : 2024-02-22DOI: 10.1175/jtech-d-23-0141.1
E. McGrath‐Spangler, N. Privé, Bryan M. Karpowicz, Isaac Moradi, Andrew K. Heidinger
The Geostationary eXtended Observations (GeoXO) program plans to include a hyperspectral infrared (IR) sounder on its central satellite, expected to launch in the mid-2030s. As part of the follow-on to the GOES program, the NOAA/NASA GeoXO Sounder (GXS) instrument will join several international counterparts in a geostationary orbit. In preparation, the NASA Global Modeling and Assimilation Office (GMAO) assessed the potential effectiveness of GXS both as a single GEO IR sounder and as part of a global ring that includes international partners. Using a global observing system simulation experiment (OSSE) framework, GXS was assessed from a numerical weather prediction (NWP) perspective. Evaluation of the ability of GXS, both alone and as part of a global ring ofGEOsounders, to improveweather prediction of thermodynamic variables was performed globally and regionally. GXS dominated regional analysis and forecast improvements, and contributed significantly to global increases in forecast skill relative to a Control. However, more sustained global improvements, on the order of 4 days, relied on international partnerships. Additionally, GXS showed the capability to improve hurricane forecast track errors on the timescales necessary for evacuation warnings. The FSOI metric over CONUS showed that the GXS observations provided the largest radiance impact on the moist energy error norm reduction. The high temporal resolution atmospheric profile information over much of the western hemisphere from GXS provides an opportunity to improve the representation of weather systems and their forecasts.
{"title":"Using OSSEs to Evaluate GXS Impact in the Context of International Coordination","authors":"E. McGrath‐Spangler, N. Privé, Bryan M. Karpowicz, Isaac Moradi, Andrew K. Heidinger","doi":"10.1175/jtech-d-23-0141.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0141.1","url":null,"abstract":"\u0000The Geostationary eXtended Observations (GeoXO) program plans to include a hyperspectral infrared (IR) sounder on its central satellite, expected to launch in the mid-2030s. As part of the follow-on to the GOES program, the NOAA/NASA GeoXO Sounder (GXS) instrument will join several international counterparts in a geostationary orbit. In preparation, the NASA Global Modeling and Assimilation Office (GMAO) assessed the potential effectiveness of GXS both as a single GEO IR sounder and as part of a global ring that includes international partners. Using a global observing system simulation experiment (OSSE) framework, GXS was assessed from a numerical weather prediction (NWP) perspective. Evaluation of the ability of GXS, both alone and as part of a global ring ofGEOsounders, to improveweather prediction of thermodynamic variables was performed globally and regionally. GXS dominated regional analysis and forecast improvements, and contributed significantly to global increases in forecast skill relative to a Control. However, more sustained global improvements, on the order of 4 days, relied on international partnerships. Additionally, GXS showed the capability to improve hurricane forecast track errors on the timescales necessary for evacuation warnings. The FSOI metric over CONUS showed that the GXS observations provided the largest radiance impact on the moist energy error norm reduction. The high temporal resolution atmospheric profile information over much of the western hemisphere from GXS provides an opportunity to improve the representation of weather systems and their forecasts.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140439333","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}
Pub Date : 2024-02-22DOI: 10.1175/jtech-d-23-0076.1
Scott D. Miller, Marc Emond, Doug Vandemark, S. Shellito, Jason Covert, I. Bogoev, Edward Swiatek
Eddy covariance (EC) air-sea CO2 flux measurements have been developed for large research vessels, but have yet to be demonstrated for smaller platforms. Our goal was to design and build a complete EC CO2 flux package suitable for unattended operation on a buoy. Published state-of-the-art techniques that have proven effective on research vessels, such as air stream drying and liquid water rejection, were adapted for a 2-m discus buoy with limited power. Fast-response atmospheric CO2 concentration was measured using both an off-the-shelf (“stock”) gas analyzer (EC155, Campbell Scientific, Inc.) and a prototype gas analyzer (“proto”) with reduced motion-induced error that was designed and built in collaboration with an instrument manufacturer. The system was tested on the University of New Hampshire (UNH) air-sea interaction buoy for 18 days in the Gulf of Maine in October 2020. The data demonstrate the overall robustness of the system. Empirical post-processing techniques previously used on ship-based measurements to address motion sensitivity of CO2 analyzers were generally not effective for the stock sensor. The proto analyzer markedly outperformed the stock unit and did not require ad hoc motion corrections, yet revealed some remaining artifacts to be addressed in future designs. Additional system refinements to further reduce power demands and increase unattended deployment duration are described.
{"title":"Field evaluation of an autonomous, low-power eddy covariance CO2 flux system for the marine environment","authors":"Scott D. Miller, Marc Emond, Doug Vandemark, S. Shellito, Jason Covert, I. Bogoev, Edward Swiatek","doi":"10.1175/jtech-d-23-0076.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0076.1","url":null,"abstract":"\u0000Eddy covariance (EC) air-sea CO2 flux measurements have been developed for large research vessels, but have yet to be demonstrated for smaller platforms. Our goal was to design and build a complete EC CO2 flux package suitable for unattended operation on a buoy. Published state-of-the-art techniques that have proven effective on research vessels, such as air stream drying and liquid water rejection, were adapted for a 2-m discus buoy with limited power. Fast-response atmospheric CO2 concentration was measured using both an off-the-shelf (“stock”) gas analyzer (EC155, Campbell Scientific, Inc.) and a prototype gas analyzer (“proto”) with reduced motion-induced error that was designed and built in collaboration with an instrument manufacturer. The system was tested on the University of New Hampshire (UNH) air-sea interaction buoy for 18 days in the Gulf of Maine in October 2020. The data demonstrate the overall robustness of the system. Empirical post-processing techniques previously used on ship-based measurements to address motion sensitivity of CO2 analyzers were generally not effective for the stock sensor. The proto analyzer markedly outperformed the stock unit and did not require ad hoc motion corrections, yet revealed some remaining artifacts to be addressed in future designs. Additional system refinements to further reduce power demands and increase unattended deployment duration are described.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140439380","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}
Pub Date : 2024-02-22DOI: 10.1175/jtech-d-23-0096.1
L. O'Neill, D. Chelton, Ernesto Rodríguez, R. Samelson, A. Wineteer
We propose a method to reconstruct sea surface height anomalies (SSHA) from vector surface currents and winds. This analysis is motivated by the proposed satellite ODYSEA, which is a Doppler scatterometer that measures coincident surface vector winds and currents. If it is feasible to estimate SSHA from these measurements, thenODYSEA could provide collocated fields of SSHA, currents, and winds over a projected wide swath of ∼1700 km. The reconstruction also yields estimates of the low-frequency surface geostrophic, Ekman, irrotational and non-divergent current components and a framework for separation of balanced and unbalanced motions. The reconstruction is based on a steady-state surface momentum budget including the Ekman drift, Coriolis acceleration, and horizontal advection. The horizontal SSHA gradient is obtained as a residual of these terms, and the unknown SSHA is solved for using a Helmholtz-Hodge Decomposition given an imposed SSHA boundary condition. We develop the reconstruction using surface currents, winds, and SSHA off the U.S. west coast from a 43-day coupled ROMS/WRF simulation. We also consider how simulated ODYSEA measurement and sampling errors and boundary condition uncertainties impact reconstruction accuracy. We find that temporal smoothing of the currents for periods of 150 hours is necessary to mitigate large reconstruction errors associated with unbalanced near-inertial motions. For the most realistic case of projected ODYSEA measurement noise and temporal sampling, the reconstructed SSHA fields have an RMS error of 2.1 cm and a model skill (squared correlation) of 0.958 with 150-hour resolution. We conclude that an accurate SSHA reconstruction is feasible using information measured by ODYSEA and external SSHA boundary conditions.
{"title":"Feasibility of estimating sea surface height anomalies from surface ocean currents and winds","authors":"L. O'Neill, D. Chelton, Ernesto Rodríguez, R. Samelson, A. Wineteer","doi":"10.1175/jtech-d-23-0096.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0096.1","url":null,"abstract":"\u0000We propose a method to reconstruct sea surface height anomalies (SSHA) from vector surface currents and winds. This analysis is motivated by the proposed satellite ODYSEA, which is a Doppler scatterometer that measures coincident surface vector winds and currents. If it is feasible to estimate SSHA from these measurements, thenODYSEA could provide collocated fields of SSHA, currents, and winds over a projected wide swath of ∼1700 km. The reconstruction also yields estimates of the low-frequency surface geostrophic, Ekman, irrotational and non-divergent current components and a framework for separation of balanced and unbalanced motions. The reconstruction is based on a steady-state surface momentum budget including the Ekman drift, Coriolis acceleration, and horizontal advection. The horizontal SSHA gradient is obtained as a residual of these terms, and the unknown SSHA is solved for using a Helmholtz-Hodge Decomposition given an imposed SSHA boundary condition. We develop the reconstruction using surface currents, winds, and SSHA off the U.S. west coast from a 43-day coupled ROMS/WRF simulation. We also consider how simulated ODYSEA measurement and sampling errors and boundary condition uncertainties impact reconstruction accuracy. We find that temporal smoothing of the currents for periods of 150 hours is necessary to mitigate large reconstruction errors associated with unbalanced near-inertial motions. For the most realistic case of projected ODYSEA measurement noise and temporal sampling, the reconstructed SSHA fields have an RMS error of 2.1 cm and a model skill (squared correlation) of 0.958 with 150-hour resolution. We conclude that an accurate SSHA reconstruction is feasible using information measured by ODYSEA and external SSHA boundary conditions.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140439616","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}
Pub Date : 2024-02-21DOI: 10.1175/jtech-d-23-0099.1
Susan L. Belak, R. Tanamachi, Matthew L. Asel, Grant Dennany, Abhiram Gnanasambandam, S. Frasier, Francesc Rocadenbosch
This study describes a novel combination of methods to remove spurious spectral peaks, or “spurs,” from Doppler spectra produced by a vertically pointing, S-band radar. The University of Massachusetts S-band frequency-modulated, continuous-wave radar (UMass FMCW) was deployed to monitor the growth of the CBL over northern Alabama during the VORTEX–Southeast field campaign in 2016. The Doppler spectra contained spurs caused by high-voltage switching power supplies in the traveling wave tube amplifier. In the original data processing scheme for this radar, a median filtering method was used to eliminate most of the spurs, but the largest ones persisted, which significantly degraded the quality of derived radar moments (e.g., reflectivity, Doppler velocity, and spectrum width) and hindered further analysis of these data (e.g., hydrometeor classification and boundary layer height tracking). Our technique for removing the spurs consists of three steps: (i) a Laplacian filter identifies and masks peaks in the spectra that are characteristic of the spurs in shape and amplitude, (ii) an in-painting method then fills in the masked area based on surrounding data, and (iii) the moments data (e.g., reflectivity, Doppler velocity, and spectrum width) are then recomputed using a coherent power technique. This combination of techniques was more effective than the median filter at removing the largest spurs from the Doppler spectra, and preserved more of the underlying Doppler spectral structure of the scatterers. Performance of both the median-filter and the in-painting methods are assessed through statistical analysis of the spectral power differences. Downstream products, such as boundary layer height detection, are more easily derived from the recomputed moments.
本研究介绍了一种新颖的方法组合，用于消除垂直指向 S 波段雷达产生的多普勒频谱中的杂散频谱峰或 "尖峰"。马萨诸塞大学 S 波段频率调制连续波雷达（UMass FMCW）被部署在 2016 年 VORTEX-Southeast 野外作业期间，以监测阿拉巴马州北部上空 CBL 的增长情况。多普勒频谱包含由行波管放大器中的高压开关电源引起的尖峰。在该雷达最初的数据处理方案中，使用了中值滤波方法来消除大部分的尖峰，但最大的尖峰仍然存在，这大大降低了得出的雷达时刻（如反射率、多普勒速度和频谱宽度）的质量，并阻碍了对这些数据的进一步分析（如水文气象分类和边界层高度跟踪）。我们的去刺技术包括三个步骤：(i)拉普拉斯滤波器识别并屏蔽频谱中的峰值，这些峰值在形状和振幅上都是尖峰的特征；(ii)然后根据周围的数据，用内绘法填充屏蔽区域；(iii)然后使用相干功率技术重新计算时刻数据（如反射率、多普勒速度和频谱宽度）。与中值滤波器相比，这种技术组合能更有效地去除多普勒频谱中最大的尖峰，并保留更多散射体的基本多普勒频谱结构。通过对频谱功率差异的统计分析，评估了中值滤波法和内绘法的性能。下游产品，如边界层高度检测，更容易从重新计算的矩中得出。
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Pub Date : 2024-02-13DOI: 10.1175/jtech-d-23-0072.1
Gilles Reverdin, L. Olivier, Cécile Cabanes, Jacqueline Boutin, C. Thouvenin-Masson, J. Vergely, N. Kolodziejczyk, Virginie Thierry, Dmitry Khvorostyanov, Julien Jouanno
In the western tropical Atlantic close to the Amazon plume, a large loss rate of Argo floats profiles took place, that is instances of profiles which should have happened, but were not transmitted. We find that Apex and Solo floats were not ascending to the surface in the presence of low surface practical salinity, typically on the order of 32.5 or less, due to limitations on the surface buoyancy range for those floats. This results in an overall loss of profiles from these floats on the order of 6% averaged over the year, with a peak of 12% in July. We also find aborted descents/incorrect grounding detections for Arvor/Provor floats when surface salinity is low and the descending float reaches a strong halocline (2.6% of all the profiles in the June to August season). Altogether, the whole Argo set includes a maximum loss rate of roughly 6% in July. We find a pattern of loss which fits the surface salinity seasonal cycle and the occurrence of low surface salinity investigated from a high-resolution daily satellite salinity product in 2010-2021. The agreement is even better when considering surface density instead of surface salinity, the temperature contribution to density inducing a shift in the maximum occurrence of these events by one month compared to the cycle of very low salinity events. Because of changes in the float technology, the loss rate which targets the lowest surface salinities was very large until 2010, with an overall decrease afterwards.
{"title":"Missing Argo float profiles in highly stratified waters of the Amazon river plume","authors":"Gilles Reverdin, L. Olivier, Cécile Cabanes, Jacqueline Boutin, C. Thouvenin-Masson, J. Vergely, N. Kolodziejczyk, Virginie Thierry, Dmitry Khvorostyanov, Julien Jouanno","doi":"10.1175/jtech-d-23-0072.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0072.1","url":null,"abstract":"\u0000In the western tropical Atlantic close to the Amazon plume, a large loss rate of Argo floats profiles took place, that is instances of profiles which should have happened, but were not transmitted. We find that Apex and Solo floats were not ascending to the surface in the presence of low surface practical salinity, typically on the order of 32.5 or less, due to limitations on the surface buoyancy range for those floats. This results in an overall loss of profiles from these floats on the order of 6% averaged over the year, with a peak of 12% in July. We also find aborted descents/incorrect grounding detections for Arvor/Provor floats when surface salinity is low and the descending float reaches a strong halocline (2.6% of all the profiles in the June to August season). Altogether, the whole Argo set includes a maximum loss rate of roughly 6% in July. We find a pattern of loss which fits the surface salinity seasonal cycle and the occurrence of low surface salinity investigated from a high-resolution daily satellite salinity product in 2010-2021. The agreement is even better when considering surface density instead of surface salinity, the temperature contribution to density inducing a shift in the maximum occurrence of these events by one month compared to the cycle of very low salinity events. Because of changes in the float technology, the loss rate which targets the lowest surface salinities was very large until 2010, with an overall decrease afterwards.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139840857","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}
Pub Date : 2024-02-13DOI: 10.1175/jtech-d-23-0072.1
Gilles Reverdin, L. Olivier, Cécile Cabanes, Jacqueline Boutin, C. Thouvenin-Masson, J. Vergely, N. Kolodziejczyk, Virginie Thierry, Dmitry Khvorostyanov, Julien Jouanno
In the western tropical Atlantic close to the Amazon plume, a large loss rate of Argo floats profiles took place, that is instances of profiles which should have happened, but were not transmitted. We find that Apex and Solo floats were not ascending to the surface in the presence of low surface practical salinity, typically on the order of 32.5 or less, due to limitations on the surface buoyancy range for those floats. This results in an overall loss of profiles from these floats on the order of 6% averaged over the year, with a peak of 12% in July. We also find aborted descents/incorrect grounding detections for Arvor/Provor floats when surface salinity is low and the descending float reaches a strong halocline (2.6% of all the profiles in the June to August season). Altogether, the whole Argo set includes a maximum loss rate of roughly 6% in July. We find a pattern of loss which fits the surface salinity seasonal cycle and the occurrence of low surface salinity investigated from a high-resolution daily satellite salinity product in 2010-2021. The agreement is even better when considering surface density instead of surface salinity, the temperature contribution to density inducing a shift in the maximum occurrence of these events by one month compared to the cycle of very low salinity events. Because of changes in the float technology, the loss rate which targets the lowest surface salinities was very large until 2010, with an overall decrease afterwards.
{"title":"Missing Argo float profiles in highly stratified waters of the Amazon river plume","authors":"Gilles Reverdin, L. Olivier, Cécile Cabanes, Jacqueline Boutin, C. Thouvenin-Masson, J. Vergely, N. Kolodziejczyk, Virginie Thierry, Dmitry Khvorostyanov, Julien Jouanno","doi":"10.1175/jtech-d-23-0072.1","DOIUrl":"https://doi.org/10.1175/jtech-d-23-0072.1","url":null,"abstract":"\u0000In the western tropical Atlantic close to the Amazon plume, a large loss rate of Argo floats profiles took place, that is instances of profiles which should have happened, but were not transmitted. We find that Apex and Solo floats were not ascending to the surface in the presence of low surface practical salinity, typically on the order of 32.5 or less, due to limitations on the surface buoyancy range for those floats. This results in an overall loss of profiles from these floats on the order of 6% averaged over the year, with a peak of 12% in July. We also find aborted descents/incorrect grounding detections for Arvor/Provor floats when surface salinity is low and the descending float reaches a strong halocline (2.6% of all the profiles in the June to August season). Altogether, the whole Argo set includes a maximum loss rate of roughly 6% in July. We find a pattern of loss which fits the surface salinity seasonal cycle and the occurrence of low surface salinity investigated from a high-resolution daily satellite salinity product in 2010-2021. The agreement is even better when considering surface density instead of surface salinity, the temperature contribution to density inducing a shift in the maximum occurrence of these events by one month compared to the cycle of very low salinity events. Because of changes in the float technology, the loss rate which targets the lowest surface salinities was very large until 2010, with an overall decrease afterwards.","PeriodicalId":507668,"journal":{"name":"Journal of Atmospheric and Oceanic Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139780829","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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