Abstract Interannual variations in spectral aerosol optical depths (AOD) were examined using the data obtained from a chain of ground-based multiwavelength solar radiometers from various locations of the Indian peninsula during the dry winter season (January–March) of 1996–2001. All of the stations revealed significant interannual variations, even though the spatial pattern of the variations differed over the years. These interannual variations were found to be significantly influenced by the extent of the southward excursion of the intertropical convergence zone (ITCZ). The years in which the southward excursion of the ITCZ was less (i.e., the years when the wintertime ITCZ was closer to the equator) showed higher AODs than the years in which the ITCZ moved far southward. The spatial variation was found to be influenced by large-scale vertical descent of an air mass over peninsular India, the Arabian Sea, the Indian Ocean, and the Bay of Bengal.
{"title":"Interannual variations of aerosol optical depth over coastal India : Relation to synoptic meteorology","authors":"A. Saha, K. Moorthy, K. Niranjan","doi":"10.1175/JAM2256.1","DOIUrl":"https://doi.org/10.1175/JAM2256.1","url":null,"abstract":"Abstract Interannual variations in spectral aerosol optical depths (AOD) were examined using the data obtained from a chain of ground-based multiwavelength solar radiometers from various locations of the Indian peninsula during the dry winter season (January–March) of 1996–2001. All of the stations revealed significant interannual variations, even though the spatial pattern of the variations differed over the years. These interannual variations were found to be significantly influenced by the extent of the southward excursion of the intertropical convergence zone (ITCZ). The years in which the southward excursion of the ITCZ was less (i.e., the years when the wintertime ITCZ was closer to the equator) showed higher AODs than the years in which the ITCZ moved far southward. The spatial variation was found to be influenced by large-scale vertical descent of an air mass over peninsular India, the Arabian Sea, the Indian Ocean, and the Bay of Bengal.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"45 1","pages":"1066-1077"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79049903","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 dispersion and concentration of particles (fluid elements) that are continuously released into a neutral planetary boundary layer is presented. The velocity fluctuations of the particles are generated using a Markov chain–Monte Carlo (MCMC) process at random time intervals with a one-step memory. The local mean concentration of the particles is calculated by using a fully Lagrangian method, which performs an efficient near-neighbor search and employs a smoothing kernel for eliminating the statistical noise. The predicted vertical and transversal root-mean-square of the particles’ deviation from their mean position [()1/2 and ()1/2] for an elevated continuous release source in a neutral atmosphere are compared with empirical parameters like the Pasquill–Gifford σz and σy. The numerical predictions of the particle concentration are compared with a Gaussian model and field measurement data on the ground concentration obtained during the Green Glow Program. The comparison between the numerical pr...
{"title":"Dispersion of Particles Released into a Neutral Planetary Boundary Layer Using a Markov Chain–Monte Carlo Model","authors":"R. Avila, S. Raza","doi":"10.1175/JAM2249.1","DOIUrl":"https://doi.org/10.1175/JAM2249.1","url":null,"abstract":"Abstract The dispersion and concentration of particles (fluid elements) that are continuously released into a neutral planetary boundary layer is presented. The velocity fluctuations of the particles are generated using a Markov chain–Monte Carlo (MCMC) process at random time intervals with a one-step memory. The local mean concentration of the particles is calculated by using a fully Lagrangian method, which performs an efficient near-neighbor search and employs a smoothing kernel for eliminating the statistical noise. The predicted vertical and transversal root-mean-square of the particles’ deviation from their mean position [()1/2 and ()1/2] for an elevated continuous release source in a neutral atmosphere are compared with empirical parameters like the Pasquill–Gifford σz and σy. The numerical predictions of the particle concentration are compared with a Gaussian model and field measurement data on the ground concentration obtained during the Green Glow Program. The comparison between the numerical pr...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"1 1","pages":"1106-1115"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78356461","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 This paper presents two multispectral enhancement techniques for distinguishing between regions of cloud and snow cover using optical spectrum passive radiometer satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Fundamental to the techniques are the 1.6- and 2.2-μm shortwave infrared bands that are useful in distinguishing between absorbing snow cover (having low reflectance) and less absorbing liquid-phase clouds (higher reflectance). The 1.38-μm band helps to overcome ambiguities that arise in the case of optically thin cirrus. Designed to provide straightforward, stand-alone environmental characterization for operational forecasters (e.g., military weather forecasters in the context of mission planning), these products portray the information that is contained within complex scenes as value-added, readily interpretable imagery at the highest available spatial resolution. Their utility in scene characterization and quality control of digital snow maps is dem...
{"title":"Satellite-Based Imagery Techniques for Daytime Cloud/Snow Delineation from MODIS.","authors":"S. Miller, Thomas F. Lee, R. Fennimore","doi":"10.1175/JAM2252.1","DOIUrl":"https://doi.org/10.1175/JAM2252.1","url":null,"abstract":"Abstract This paper presents two multispectral enhancement techniques for distinguishing between regions of cloud and snow cover using optical spectrum passive radiometer satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Fundamental to the techniques are the 1.6- and 2.2-μm shortwave infrared bands that are useful in distinguishing between absorbing snow cover (having low reflectance) and less absorbing liquid-phase clouds (higher reflectance). The 1.38-μm band helps to overcome ambiguities that arise in the case of optically thin cirrus. Designed to provide straightforward, stand-alone environmental characterization for operational forecasters (e.g., military weather forecasters in the context of mission planning), these products portray the information that is contained within complex scenes as value-added, readily interpretable imagery at the highest available spatial resolution. Their utility in scene characterization and quality control of digital snow maps is dem...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"27 1","pages":"987-997"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74521622","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}
Yansen Wang, C. Williamson, D. Garvey, Sam S. Chang, J. Cogan
Abstract A multigrid numerical method has been applied to a three-dimensional, high-resolution diagnostic model for flow over complex terrain using a mass-consistent approach. The theoretical background for the model is based on a variational analysis using mass conservation as a constraint. The model was designed for diagnostic wind simulation at the microscale in complex terrain and in urban areas. The numerical implementation takes advantage of a multigrid method that greatly improves the computation speed. Three preliminary test cases for the model’s numerical efficiency and its accuracy are given. The model results are compared with an analytical solution for flow over a hemisphere. Flow over a bell-shaped hill is computed to demonstrate that the numerical method is applicable in the case of parameterized lee vortices. A simulation of the mean wind field in an urban domain has also been carried out and compared with observational data. The comparison indicated that the multigrid method takes only 3%–...
{"title":"Application of a Multigrid Method to a Mass-Consistent Diagnostic Wind Model","authors":"Yansen Wang, C. Williamson, D. Garvey, Sam S. Chang, J. Cogan","doi":"10.1175/JAM2262.1","DOIUrl":"https://doi.org/10.1175/JAM2262.1","url":null,"abstract":"Abstract A multigrid numerical method has been applied to a three-dimensional, high-resolution diagnostic model for flow over complex terrain using a mass-consistent approach. The theoretical background for the model is based on a variational analysis using mass conservation as a constraint. The model was designed for diagnostic wind simulation at the microscale in complex terrain and in urban areas. The numerical implementation takes advantage of a multigrid method that greatly improves the computation speed. Three preliminary test cases for the model’s numerical efficiency and its accuracy are given. The model results are compared with an analytical solution for flow over a hemisphere. Flow over a bell-shaped hill is computed to demonstrate that the numerical method is applicable in the case of parameterized lee vortices. A simulation of the mean wind field in an urban domain has also been carried out and compared with observational data. The comparison indicated that the multigrid method takes only 3%–...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"65 1","pages":"1078-1089"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80731604","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}
B. Bernstein, F. Mcdonough, M. Politovich, B. Brown, T. Ratvasky, Dean R. Miller, C. Wolff, G. Cunning
Abstract The “current icing potential” (CIP) algorithm combines satellite, radar, surface, lightning, and pilot-report observations with model output to create a detailed three-dimensional hourly diagnosis of the potential for the existence of icing and supercooled large droplets. It uses a physically based situational approach that is derived from basic and applied cloud physics, combined with forecaster and onboard flight experience from field programs. Both fuzzy logic and decision-tree logic are applied in this context. CIP determines the locations of clouds and precipitation and then estimates the potential for the presence of supercooled liquid water and supercooled large droplets within a given airspace. First developed in the winter of 1997/98, CIP became an operational National Weather Service and Federal Aviation Administration product in 2002, providing real-time diagnoses that allow users to make route-specific decisions to avoid potentially hazardous icing. The CIP algorithm, its individual c...
{"title":"Current Icing Potential: Algorithm Description and Comparison with Aircraft Observations","authors":"B. Bernstein, F. Mcdonough, M. Politovich, B. Brown, T. Ratvasky, Dean R. Miller, C. Wolff, G. Cunning","doi":"10.1175/JAM2246.1","DOIUrl":"https://doi.org/10.1175/JAM2246.1","url":null,"abstract":"Abstract The “current icing potential” (CIP) algorithm combines satellite, radar, surface, lightning, and pilot-report observations with model output to create a detailed three-dimensional hourly diagnosis of the potential for the existence of icing and supercooled large droplets. It uses a physically based situational approach that is derived from basic and applied cloud physics, combined with forecaster and onboard flight experience from field programs. Both fuzzy logic and decision-tree logic are applied in this context. CIP determines the locations of clouds and precipitation and then estimates the potential for the presence of supercooled liquid water and supercooled large droplets within a given airspace. First developed in the winter of 1997/98, CIP became an operational National Weather Service and Federal Aviation Administration product in 2002, providing real-time diagnoses that allow users to make route-specific decisions to avoid potentially hazardous icing. The CIP algorithm, its individual c...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"11 1","pages":"969-986"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82950056","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 Errors in surface rainfall estimates that are caused by ignoring the vertical profile of reflectivity (VPR) and range effects have been assessed by simulating how fine-resolution 3D reflectivity measurements at close ranges are sampled by the radar at various ranges and heights. Uncorrected and corrected accumulations from 33 events of mainly stratiform precipitation, with a recognizable melting layer for over 250 h, have been generated using two basic procedures: (a) the “near range” or “inner” VPR and (b) the intensity-dependent “climatological” VPR. The root-mean-square (rms) error structure has been derived as a function of height and range, for accumulations ranging from 5 min to 2 h, for various brightband heights and verification areas. However, it is the errors along the lowest default height that are most relevant. The stratification of the results by the height of the bright band is essential to understand the influence of the bright band with range. The largest errors (>100% at near ra...
{"title":"Error Statistics of VPR Corrections in Stratiform Precipitation","authors":"A. Bellon, Gyuwon Lee, I. Zawadzki","doi":"10.1175/JAM2253.1","DOIUrl":"https://doi.org/10.1175/JAM2253.1","url":null,"abstract":"Abstract Errors in surface rainfall estimates that are caused by ignoring the vertical profile of reflectivity (VPR) and range effects have been assessed by simulating how fine-resolution 3D reflectivity measurements at close ranges are sampled by the radar at various ranges and heights. Uncorrected and corrected accumulations from 33 events of mainly stratiform precipitation, with a recognizable melting layer for over 250 h, have been generated using two basic procedures: (a) the “near range” or “inner” VPR and (b) the intensity-dependent “climatological” VPR. The root-mean-square (rms) error structure has been derived as a function of height and range, for accumulations ranging from 5 min to 2 h, for various brightband heights and verification areas. However, it is the errors along the lowest default height that are most relevant. The stratification of the results by the height of the bright band is essential to understand the influence of the bright band with range. The largest errors (>100% at near ra...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"45 1","pages":"998-1015"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90743820","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 Soil water contents, calculated with seven soil hydraulic parameterizations, that is, soil hydraulic functions together with the corresponding parameter sets, are compared with observational data. The parameterizations include the Campbell/Clapp–Hornberger parameterization that is often used by meteorologists and the van Genuchten/Rawls–Brakensiek parameterization that is widespread among hydrologists. The observations include soil water contents at several soil depths and atmospheric surface data; they were obtained within the Regio Klima Projekt (REKLIP) at three sites in the Rhine Valley in southern Germany and cover up to 3 yr with 10-min temporal resolution. Simulations of 48-h episodes, as well as series of daily simulations initialized anew every 24 h and covering several years, were performed with the “VEG3D” soil–vegetation model in stand-alone mode; furthermore, 48-h episodes were simulated with the model coupled to a one-dimensional atmospheric model. For the cases and soil types consi...
{"title":"Comparison of Soil Hydraulic Parameterizations for Mesoscale Meteorological Models","authors":"F. Braun, G. Schädler","doi":"10.1175/JAM2259.1","DOIUrl":"https://doi.org/10.1175/JAM2259.1","url":null,"abstract":"Abstract Soil water contents, calculated with seven soil hydraulic parameterizations, that is, soil hydraulic functions together with the corresponding parameter sets, are compared with observational data. The parameterizations include the Campbell/Clapp–Hornberger parameterization that is often used by meteorologists and the van Genuchten/Rawls–Brakensiek parameterization that is widespread among hydrologists. The observations include soil water contents at several soil depths and atmospheric surface data; they were obtained within the Regio Klima Projekt (REKLIP) at three sites in the Rhine Valley in southern Germany and cover up to 3 yr with 10-min temporal resolution. Simulations of 48-h episodes, as well as series of daily simulations initialized anew every 24 h and covering several years, were performed with the “VEG3D” soil–vegetation model in stand-alone mode; furthermore, 48-h episodes were simulated with the model coupled to a one-dimensional atmospheric model. For the cases and soil types consi...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"56 1","pages":"1116-1132"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89480029","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 relation between the slope and shape parameters of the raindrop size distribution parameterized by a gamma distribution is examined. The comparison of results of a simple rain shaft model with an empirical relation based on disdrometer measurements at the surface shows very good agreement, but a more detailed discussion reveals some difficulties—for example, deviations from the gamma shape and the overestimation of collisional breakup.
{"title":"On the shape-slope relation of drop size distributions in convective rain","authors":"A. Seifert","doi":"10.1175/JAM2254.1","DOIUrl":"https://doi.org/10.1175/JAM2254.1","url":null,"abstract":"Abstract The relation between the slope and shape parameters of the raindrop size distribution parameterized by a gamma distribution is examined. The comparison of results of a simple rain shaft model with an empirical relation based on disdrometer measurements at the surface shows very good agreement, but a more detailed discussion reveals some difficulties—for example, deviations from the gamma shape and the overestimation of collisional breakup.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"338 1","pages":"1146-1151"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76383536","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}
J. Badosa, Josep‐Abel González, J. Calbó, M. Weele, R. McKenzie
To perform a climatic analysis of the annual UV index (UVI) variations in Catalonia, Spain (northeast of the Iberian Peninsula), a new simple parameterization scheme is presented based on a multilayer radiative transfer model. The parameterization performs fast UVI calculations for a wide range of cloudless and snow-free situations and can be applied anywhere. The following parameters are considered: solar zenith angle, total ozone column, altitude, aerosol optical depth, and single-scattering albedo. A sensitivity analysis is presented to justify this choice with special attention to aerosol information. Comparisons with the base model show good agreement, most of all for the most common cases, giving an absolute error within 0.2 in the UVI for a wide range of cases considered. Two tests are done to show the performance of the parameterization against UVI measurements. One uses data from a high-quality spectroradiometer from Lauder, New Zealand [45.04°S, 169.684°E, 370 m above mean sea level (MSL)], where there is a low presence of aerosols. The other uses data from a Robertson–Berger-type meter from Girona, Spain (41.97°N, 2.82°E, 100 m MSL), where there is more aerosol load and where it has been possible to study the effect of aerosol information on the model versus measurement comparison. The parameterization is applied to a climatic analysis of the annual UVI variation in Catalonia, showing the contributions of solar zenith angle, ozone, and aerosols. High-resolution seasonal maps of typical UV index values in Catalonia are presented.
为了对西班牙加泰罗尼亚地区(伊比利亚半岛东北部)的年UV指数(UVI)变化进行气候分析，提出了一种基于多层辐射传输模式的简单参数化方案。参数化执行快速UVI计算范围广泛的无云和无雪的情况下，可以应用于任何地方。考虑了下列参数:太阳天顶角、总臭氧柱、高度、气溶胶光学深度和单散射反照率。提出了一个敏感性分析来证明这种选择的合理性，并特别注意气溶胶信息。与基本模型的比较显示出良好的一致性，大多数情况下都是如此，在考虑的广泛情况下，UVI的绝对误差在0.2以内。进行了两个测试，以显示参数化对UVI测量的性能。一种是使用来自新西兰Lauder的高质量光谱仪的数据[45.04°S, 169.684°E，平均海平面(MSL)以上370米]，该地区气溶胶含量较低。另一个使用来自西班牙赫罗纳(41.97°N, 2.82°E, 100 m MSL)的robertson - berger型仪表的数据，那里有更多的气溶胶负荷，并且有可能研究气溶胶信息对模型的影响与测量比较。将参数化方法应用于加泰罗尼亚地区UVI年变化的气候分析，显示了太阳天顶角、臭氧和气溶胶的贡献。介绍了加泰罗尼亚典型紫外线指数的高分辨率季节性地图。
{"title":"Using a Parameterization of a Radiative Transfer Model to Build High-Resolution Maps of Typical Clear-Sky UV Index in Catalonia, Spain","authors":"J. Badosa, Josep‐Abel González, J. Calbó, M. Weele, R. McKenzie","doi":"10.1175/JAM2237.1","DOIUrl":"https://doi.org/10.1175/JAM2237.1","url":null,"abstract":"To perform a climatic analysis of the annual UV index (UVI) variations in Catalonia, Spain (northeast of the Iberian Peninsula), a new simple parameterization scheme is presented based on a multilayer radiative transfer model. The parameterization performs fast UVI calculations for a wide range of cloudless and snow-free situations and can be applied anywhere. The following parameters are considered: solar zenith angle, total ozone column, altitude, aerosol optical depth, and single-scattering albedo. A sensitivity analysis is presented to justify this choice with special attention to aerosol information. Comparisons with the base model show good agreement, most of all for the most common cases, giving an absolute error within 0.2 in the UVI for a wide range of cases considered. Two tests are done to show the performance of the parameterization against UVI measurements. One uses data from a high-quality spectroradiometer from Lauder, New Zealand [45.04°S, 169.684°E, 370 m above mean sea level (MSL)], where there is a low presence of aerosols. The other uses data from a Robertson–Berger-type meter from Girona, Spain (41.97°N, 2.82°E, 100 m MSL), where there is more aerosol load and where it has been possible to study the effect of aerosol information on the model versus measurement comparison. The parameterization is applied to a climatic analysis of the annual UVI variation in Catalonia, showing the contributions of solar zenith angle, ozone, and aerosols. High-resolution seasonal maps of typical UV index values in Catalonia are presented.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"23 1","pages":"789-803"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80661649","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 NOAA Advanced Very High Resolution Radiometer (AVHRR) images revealed conspicuous tracks of glaciated cloud in thick supercooled layer clouds over central China. These tracks were identified as being artificially produced by cloud-seeding operations at the −10°C isotherm, less than 1 km below cloud tops, aimed at precipitation enhancement, by means of AgI acetone generators. The cloud composition was deduced by retrieving the cloud-top effective radius (re) and analyzing its spatial relations with cloud-top temperatures and with the visible reflectance. Cloud-top temperature varied between −13° and −17°C. The glaciation became apparent at cloud tops about 22 min after seeding. The glaciated tops sank and formed a channel in the supercooled layer cloud. The rate of sinking of about 40 cm s−1 is compatible with the fall velocity of ice crystals that are likely to form at these conditions. A thin line of new water clouds formed in the middle of the channel of the seeded track between 38 and 63 min a...
美国国家海洋和大气管理局(NOAA)先进甚高分辨率辐射计(AVHRR)图像揭示了中国中部厚过冷层云中明显的冰川云轨迹。这些轨迹被认为是在- 10°C等温线上，在云顶以下不到1公里处，利用AgI丙酮发生器进行人工降雨作业而产生的，目的是增强降水。通过检索云顶有效半径(re)，分析其与云顶温度和可见光反射率的空间关系，推导出云的组成。云顶温度在- 13°和- 17°C之间变化。在播种后约22分钟，云顶的冰川作用开始明显。冰川覆盖的顶部下沉并在过冷层云中形成通道。大约40 cm s−1的下沉速率与在这种条件下可能形成的冰晶的下落速度是相容的。在每小时38到63分钟之间，一条细细的新水云线在种子轨道的通道中央形成。
{"title":"Satellite-Retrieved Microstructure of AgI Seeding Tracks in Supercooled Layer Clouds","authors":"D. Rosenfeld, Xing Yu, J. Dai","doi":"10.1175/JAM2225.1","DOIUrl":"https://doi.org/10.1175/JAM2225.1","url":null,"abstract":"Abstract NOAA Advanced Very High Resolution Radiometer (AVHRR) images revealed conspicuous tracks of glaciated cloud in thick supercooled layer clouds over central China. These tracks were identified as being artificially produced by cloud-seeding operations at the −10°C isotherm, less than 1 km below cloud tops, aimed at precipitation enhancement, by means of AgI acetone generators. The cloud composition was deduced by retrieving the cloud-top effective radius (re) and analyzing its spatial relations with cloud-top temperatures and with the visible reflectance. Cloud-top temperature varied between −13° and −17°C. The glaciation became apparent at cloud tops about 22 min after seeding. The glaciated tops sank and formed a channel in the supercooled layer cloud. The rate of sinking of about 40 cm s−1 is compatible with the fall velocity of ice crystals that are likely to form at these conditions. A thin line of new water clouds formed in the middle of the channel of the seeded track between 38 and 63 min a...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"86 1","pages":"760-767"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78221011","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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