Pub Date : 2023-10-25DOI: 10.1175/jamc-d-22-0154.1
Troy J. Zaremba, Robert M. Rauber, Larry Di Girolamo, Jesse R. Loveridge, Greg M. McFarquhar
Abstract Recent studies from the Seeded and Natural Orographic Wintertime Clouds: the Idaho Experiment (SNOWIE) demonstrated definitive radar evidence of seeding signatures in winter orographic clouds during three intensive operation periods (IOPs) where the background signal from natural precipitation was weak and a radar signal attributable to seeding could be identified as traceable seeding lines. Except for the three IOPs where seeding was detected, background natural snowfall was present during seeding operations and no clear seeding signatures were detected. This paper provides a quantitative analysis to assess if orographic cloud seeding effects are detectable using radar when background precipitation is present. We show that a 5 dB change in equivalent reflectivity factor ( Z e ) is required to stand out against background natural Z e variability. This analysis considers four radar wavelengths, a range of background ice water contents (IWC) from 0.012 g m −3 to 1.214 g m −3 , and additional IWC introduced by seeding ranging from 0.012 g m −3 to 0.486 g m −3 . The upper limit values of seeded IWC are based on measurements of IWC from the Nevzorov probe employed on the University of Wyoming King Air aircraft during SNOWIE. This analysis implies that seeding effects will be undetectable using radar within background snowfall unless the background IWC is small, and the seeding effects are large. It therefore remains uncertain whether seeding had no effect on cloud microstructure, and therefore produced no signature on radar, or whether seeding did have an effect, but that effect was undetectable against the background reflectivity associated with naturally-produced precipitation.
来自人工播种和自然地形冬季云:爱达荷实验(SNOWIE)的最新研究表明，在自然降水背景信号较弱的三个集约运行期(IOPs)，冬季地形云中存在播种信号的确凿雷达证据，而由播种引起的雷达信号可以被识别为可追踪的播种线。除了3个观测到播种的IOPs外，在播种过程中存在背景自然降雪，没有观测到明显的播种特征。本文提供了一个定量分析来评估当背景降水存在时，雷达是否可以探测到地形云的播撒效应。我们表明，需要等效反射率因子(ze)的5 dB变化来突出背景自然ze变率。该分析考虑了四种雷达波长，背景冰水含量(IWC)范围从0.012 g m−3到1.214 g m−3，以及通过播种引入的额外IWC范围从0.012 g m−3到0.486 g m−3。种子IWC的上限值是基于在snowwie期间怀俄明大学国王航空飞机上使用的涅佐夫探测器对IWC的测量。这一分析表明，除非背景IWC很小，而播种效应很大，否则在背景降雪中雷达无法探测到播种效应。因此，仍然不确定是否人工播种对云的微观结构没有影响，因此在雷达上没有产生信号，或者是否人工播种确实有影响，但这种影响在与自然产生的降水相关的背景反射率下无法检测到。
{"title":"On the radar detection of cloud seeding effects in wintertime orographic cloud systems","authors":"Troy J. Zaremba, Robert M. Rauber, Larry Di Girolamo, Jesse R. Loveridge, Greg M. McFarquhar","doi":"10.1175/jamc-d-22-0154.1","DOIUrl":"https://doi.org/10.1175/jamc-d-22-0154.1","url":null,"abstract":"Abstract Recent studies from the Seeded and Natural Orographic Wintertime Clouds: the Idaho Experiment (SNOWIE) demonstrated definitive radar evidence of seeding signatures in winter orographic clouds during three intensive operation periods (IOPs) where the background signal from natural precipitation was weak and a radar signal attributable to seeding could be identified as traceable seeding lines. Except for the three IOPs where seeding was detected, background natural snowfall was present during seeding operations and no clear seeding signatures were detected. This paper provides a quantitative analysis to assess if orographic cloud seeding effects are detectable using radar when background precipitation is present. We show that a 5 dB change in equivalent reflectivity factor ( Z e ) is required to stand out against background natural Z e variability. This analysis considers four radar wavelengths, a range of background ice water contents (IWC) from 0.012 g m −3 to 1.214 g m −3 , and additional IWC introduced by seeding ranging from 0.012 g m −3 to 0.486 g m −3 . The upper limit values of seeded IWC are based on measurements of IWC from the Nevzorov probe employed on the University of Wyoming King Air aircraft during SNOWIE. This analysis implies that seeding effects will be undetectable using radar within background snowfall unless the background IWC is small, and the seeding effects are large. It therefore remains uncertain whether seeding had no effect on cloud microstructure, and therefore produced no signature on radar, or whether seeding did have an effect, but that effect was undetectable against the background reflectivity associated with naturally-produced precipitation.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"68 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135113188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-23DOI: 10.1175/jamc-d-23-0071.1
Megan S. Mallard, Kevin D. Talgo, Tanya L. Spero, Jared H. Bowden, Christopher G. Nolte
Abstract Phenological indicators (PI) are used to study changes to animal and plant behavior in response to seasonal cycles, and they can be useful to quantify the potential impacts of climate change on ecosystems. Here, multiple global climate models and emission scenarios are used to drive dynamically downscaled simulations using the WRF model over the CONUS. The wintertime dormancy of plants (chilling units or “CU”), timing of spring onset (Extended Spring Indices or “SI”), and frequency of proceeding false springs are calculated from regional climate simulations covering historical (1995–2005) and future periods (2025–2100). Southern parts of the CONUS show projected CU decreases (inhibiting some plants from flowering or fruiting), while the northern CONUS experiences an increase (possibly causing plants to break dormancy too early, becoming vulnerable to disease or freezing). Spring advancement (earlier SI dates) is projected, with decadal trends ranging from approximately 1 to 4 days per decade over the CONUS, comparable to or exceeding those found in observational studies. Projected changes in risk of false spring (hard freezes following spring onset) vary across members of the ensemble and regions of the CONUS, but generally western parts of the CONUS are projected to experience increased risk of false springs. These projected changes to PI connote significant effects on cycles of plants, animals, and ecosystems, highlighting the importance of examining temperature changes during transitional seasons.
{"title":"Dynamically Downscaled Projections of Phenological Changes across the Contiguous United States","authors":"Megan S. Mallard, Kevin D. Talgo, Tanya L. Spero, Jared H. Bowden, Christopher G. Nolte","doi":"10.1175/jamc-d-23-0071.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0071.1","url":null,"abstract":"Abstract Phenological indicators (PI) are used to study changes to animal and plant behavior in response to seasonal cycles, and they can be useful to quantify the potential impacts of climate change on ecosystems. Here, multiple global climate models and emission scenarios are used to drive dynamically downscaled simulations using the WRF model over the CONUS. The wintertime dormancy of plants (chilling units or “CU”), timing of spring onset (Extended Spring Indices or “SI”), and frequency of proceeding false springs are calculated from regional climate simulations covering historical (1995–2005) and future periods (2025–2100). Southern parts of the CONUS show projected CU decreases (inhibiting some plants from flowering or fruiting), while the northern CONUS experiences an increase (possibly causing plants to break dormancy too early, becoming vulnerable to disease or freezing). Spring advancement (earlier SI dates) is projected, with decadal trends ranging from approximately 1 to 4 days per decade over the CONUS, comparable to or exceeding those found in observational studies. Projected changes in risk of false spring (hard freezes following spring onset) vary across members of the ensemble and regions of the CONUS, but generally western parts of the CONUS are projected to experience increased risk of false springs. These projected changes to PI connote significant effects on cycles of plants, animals, and ecosystems, highlighting the importance of examining temperature changes during transitional seasons.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"20 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135413079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-20DOI: 10.1175/jamc-d-22-0205.1
S. Jamaer, D. Allaerts, J. Meyers, N. P. M. van Lipzig
Abstract Vertical temperature profiles influence the wind power generation of large offshore wind farms through stability-dependent effects such as blockage and gravity waves. However, numerical tools that are used to model these effects are often computationally too expensive to cover the large variety of atmospheric states occurring over time. Generally, an informed decision about which representative non-idealized situations to simulate is missing because of the lack of easily available information on representative vertical profiles, taking into account their spatio-temporal variability. Therefore, we present a novel framework that allows a smart selection of vertical temperature profiles. The framework consists of an improved analytical temperature model for the atmospheric boundary layer and lower troposphere, a subsequent clustering of these profiles to identify representatives, and lastly, a determination of areas with similar spatio-temporal characteristics of vertical profiles. When applying this framework on European ERA5 data, physically realistic representatives were identified for Europe, excluding the Mediterranean. Two or three profiles were found to be dominant for the open ocean, whereas more profiles prevail for land. Over the open ocean, weak temperature gradients in the boundary layer and a clear capping inversions are widespread, and stable profiles are absent except in the region of the East Icelandic current. Interestingly, according to the ERA5 data, at its resolution, coastal areas and seas surrounded by land behave more similar to the land areas than to the open ocean, implying that a larger set of model integrations are needed for these areas to obtain representative results for offshore wind power assessments compared to the open ocean.
{"title":"A Novel Framework for Spatio-Temporal Analysis of Temperature Profiles Applied to Europe","authors":"S. Jamaer, D. Allaerts, J. Meyers, N. P. M. van Lipzig","doi":"10.1175/jamc-d-22-0205.1","DOIUrl":"https://doi.org/10.1175/jamc-d-22-0205.1","url":null,"abstract":"Abstract Vertical temperature profiles influence the wind power generation of large offshore wind farms through stability-dependent effects such as blockage and gravity waves. However, numerical tools that are used to model these effects are often computationally too expensive to cover the large variety of atmospheric states occurring over time. Generally, an informed decision about which representative non-idealized situations to simulate is missing because of the lack of easily available information on representative vertical profiles, taking into account their spatio-temporal variability. Therefore, we present a novel framework that allows a smart selection of vertical temperature profiles. The framework consists of an improved analytical temperature model for the atmospheric boundary layer and lower troposphere, a subsequent clustering of these profiles to identify representatives, and lastly, a determination of areas with similar spatio-temporal characteristics of vertical profiles. When applying this framework on European ERA5 data, physically realistic representatives were identified for Europe, excluding the Mediterranean. Two or three profiles were found to be dominant for the open ocean, whereas more profiles prevail for land. Over the open ocean, weak temperature gradients in the boundary layer and a clear capping inversions are widespread, and stable profiles are absent except in the region of the East Icelandic current. Interestingly, according to the ERA5 data, at its resolution, coastal areas and seas surrounded by land behave more similar to the land areas than to the open ocean, implying that a larger set of model integrations are needed for these areas to obtain representative results for offshore wind power assessments compared to the open ocean.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135616726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.1175/jamc-d-23-0081.1
Trent W. Ford, Jason A. Otkin, Steven M. Quiring, Joel Lisonbee, Molly Woloszyn, Junming Wang, Yafang Zhong
Abstract Increased flash drought awareness in recent years has motivated the development of numerous indicators for monitoring, early warning, and assessment. The flash drought indicators can act as a complementary set of tools by which to inform flash drought response and management. However, the limitations of each indicator much be measured and communicated between research and practitioners to ensure effectiveness. The limitations of any flash drought indicator are better understood and overcome through assessment of indicator sensitivity and consistency; however, such assessment cannot assume any single indicator properly represents the flash drought “truth”. To better understand the current state of flash drought monitoring, this study presents an inter-comparison of nine, widely used flash drought indicators. The indicators represent perspectives and processes that are known to drive flash drought, including evapotranspiration and evaporative demand, precipitation, and soil moisture. We find no single flash drought indicator consistently outperforms all others across the contiguous United States. We do find the evaporative demand- and evapotranspiration- driven indicators tend to lead precipitation- and soil moisture-based indicators in flash drought onset, but also tend to produce more flash drought events collectively. Overall, the regional and definition-specific variability in results supports the argument for a multi-indicator approach for flash drought monitoring, as advocated by recent studies. Furthermore, flash drought research – especially evaluation of historical and potential future changes in flash drought characteristics – should test multiple indicators, datasets, and methods for representing flash drought, and ideally employ a multi-indicator analysis frameworks over use of a single indicator from which to infer all flash drought information.
{"title":"Flash Drought Indicator Inter-Comparison in the United States","authors":"Trent W. Ford, Jason A. Otkin, Steven M. Quiring, Joel Lisonbee, Molly Woloszyn, Junming Wang, Yafang Zhong","doi":"10.1175/jamc-d-23-0081.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0081.1","url":null,"abstract":"Abstract Increased flash drought awareness in recent years has motivated the development of numerous indicators for monitoring, early warning, and assessment. The flash drought indicators can act as a complementary set of tools by which to inform flash drought response and management. However, the limitations of each indicator much be measured and communicated between research and practitioners to ensure effectiveness. The limitations of any flash drought indicator are better understood and overcome through assessment of indicator sensitivity and consistency; however, such assessment cannot assume any single indicator properly represents the flash drought “truth”. To better understand the current state of flash drought monitoring, this study presents an inter-comparison of nine, widely used flash drought indicators. The indicators represent perspectives and processes that are known to drive flash drought, including evapotranspiration and evaporative demand, precipitation, and soil moisture. We find no single flash drought indicator consistently outperforms all others across the contiguous United States. We do find the evaporative demand- and evapotranspiration- driven indicators tend to lead precipitation- and soil moisture-based indicators in flash drought onset, but also tend to produce more flash drought events collectively. Overall, the regional and definition-specific variability in results supports the argument for a multi-indicator approach for flash drought monitoring, as advocated by recent studies. Furthermore, flash drought research – especially evaluation of historical and potential future changes in flash drought characteristics – should test multiple indicators, datasets, and methods for representing flash drought, and ideally employ a multi-indicator analysis frameworks over use of a single indicator from which to infer all flash drought information.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"256 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135918217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-11DOI: 10.1175/jamc-d-23-0013.1
Martin Ridal, Jana Sanchez-Arriola, Mats Dahlbom
Abstract The use of radial velocity information from the European weather radar network is a challenging task, due to a rather heterogeneous radar network and the different ways of providing the Doppler velocity information. A preprocessing is therefore needed to harmonize the data. Radar observations consist of a very high resolution dataset which means that it is both demanding to process as well as that the inherent resolution is much higher than the model resolution. One way of reducing the amount of data is to create super observations (SO) by averaging observations in a predefined area. This paper describes the preprocessing necessary to use radar radial velocities in the data assimilation where the SO construction is included. The main focus is to optimize the use of radial velocities in the HARMONIE-AROME numerical weather model. Several experiments were run to find the best settings for first-guess check limits as well as a tuning of the observation error value. The optimal size of the SO and the corresponding thinning distance for radar radial velocities was also studied. It was found that the radial velocity information and the reflectivity from weather radars can be treated differently when it comes to the size of the SO and the thinning. A positive impact was found when adding the velocities together with the reflectivity using the same SO size and thinning distance, but the best results were found when the SO and thinning distance for the radial velocities are smaller compared to the corresponding values for reflectivity.
{"title":"Optimal use of radar radial winds in the HARMONIE numerical weather prediction system","authors":"Martin Ridal, Jana Sanchez-Arriola, Mats Dahlbom","doi":"10.1175/jamc-d-23-0013.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0013.1","url":null,"abstract":"Abstract The use of radial velocity information from the European weather radar network is a challenging task, due to a rather heterogeneous radar network and the different ways of providing the Doppler velocity information. A preprocessing is therefore needed to harmonize the data. Radar observations consist of a very high resolution dataset which means that it is both demanding to process as well as that the inherent resolution is much higher than the model resolution. One way of reducing the amount of data is to create super observations (SO) by averaging observations in a predefined area. This paper describes the preprocessing necessary to use radar radial velocities in the data assimilation where the SO construction is included. The main focus is to optimize the use of radial velocities in the HARMONIE-AROME numerical weather model. Several experiments were run to find the best settings for first-guess check limits as well as a tuning of the observation error value. The optimal size of the SO and the corresponding thinning distance for radar radial velocities was also studied. It was found that the radial velocity information and the reflectivity from weather radars can be treated differently when it comes to the size of the SO and the thinning. A positive impact was found when adding the velocities together with the reflectivity using the same SO size and thinning distance, but the best results were found when the SO and thinning distance for the radial velocities are smaller compared to the corresponding values for reflectivity.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136097501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.1175/jamc-d-23-0053.1
Takuto Sato, Hiroyuki Kusaka
This study focuses on the application of two standard inflow turbulence generation methods for growing convective boundary layer (CBL) simulations: the recycle-rescale method (R-R method) and the digital filter-based (DF) methods, which are used in computational fluid dynamics. The primary objective of this study is to expand the applicability of the R-R method to simulations of thermally driven CBLs. This method is called the extended R-R method. However, in previous studies, the DF method has been extended to generate potential temperature perturbations. This study investigated whether the extended DF method can be applied to simulations of growing thermally driven CBLs. In this study, idealized simulations of growing thermally driven CBLs using the extended R-R and DF methods were performed. The results showed that both extended methods could capture the characteristics of thermally driven CBLs. The extended R-R method reproduced turbulence in thermally driven CBLs better than the extended DF method in spectrum and histogram of vertical wind speed. However, the height of the thermally driven CBL was underestimated in about 100m compared with the extended DF method. Sensitivity experiments were conducted on the parameters used in the extended DF and R-R methods. The results showed that underestimation of the length scale in the extended DF method causes a shortage of large-scale turbulence components. The other point suggested by the results of the sensitivity experiments is that the length of the driver region in the extended R-R method should be sufficient to reproduce the spanwise movement of the roll vortices.
{"title":"Applicability of methods for inflow turbulence generation developed in a CFD field to the thermally driven convective boundary layer simulations","authors":"Takuto Sato, Hiroyuki Kusaka","doi":"10.1175/jamc-d-23-0053.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0053.1","url":null,"abstract":"This study focuses on the application of two standard inflow turbulence generation methods for growing convective boundary layer (CBL) simulations: the recycle-rescale method (R-R method) and the digital filter-based (DF) methods, which are used in computational fluid dynamics. The primary objective of this study is to expand the applicability of the R-R method to simulations of thermally driven CBLs. This method is called the extended R-R method. However, in previous studies, the DF method has been extended to generate potential temperature perturbations. This study investigated whether the extended DF method can be applied to simulations of growing thermally driven CBLs. In this study, idealized simulations of growing thermally driven CBLs using the extended R-R and DF methods were performed. The results showed that both extended methods could capture the characteristics of thermally driven CBLs. The extended R-R method reproduced turbulence in thermally driven CBLs better than the extended DF method in spectrum and histogram of vertical wind speed. However, the height of the thermally driven CBL was underestimated in about 100m compared with the extended DF method. Sensitivity experiments were conducted on the parameters used in the extended DF and R-R methods. The results showed that underestimation of the length scale in the extended DF method causes a shortage of large-scale turbulence components. The other point suggested by the results of the sensitivity experiments is that the length of the driver region in the extended R-R method should be sufficient to reproduce the spanwise movement of the roll vortices.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135352384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-03DOI: 10.1175/jamc-d-23-0030.1
Andrew J. Heymsfield, Micael A. Cecchini, Andrew Detwiler, Ryan Honeyager, Paul Field
Abstract Measurements from the South Dakota School of Mines and Technology T-28 hail-penetrating aircraft are analyzed using recently developed data processing techniques with the goals of identifying where the large hail is found relative to vertical motion and improving the detection of hail microphysical properties from radar. Hail particle size distributions (PSD) and environmental conditions (temperature, relative humidity, liquid water content, air vertical velocity) were digitally collected by the T28 between 1995 and 2003 and synthesized by Detwiler et al. (2012). The PSD were forward-modeled by Cecchini et al. (2022) to simulate the radar reflectivity of the PSD at multiple radar wavelengths. The T-28 penetrated temperatures primarily between 0 and −10 °C. The largest hailstones were sampled near the updraft/downdraft interface. Liquid water contents were highest in the updraft cores, whereas total (liquid + frozen) water contents were highest near the updraft/downdraft interface. The fitted properties of the PSD, intercept and slope, are directly related to each other, but do not show any dependence on the region of the hailstorm where sampled. The PSD measurements and the radar reflectivity calculations at multiple radar wavelengths facilitated the development of relationships between the PSD bulk properties—hail kinetic energy and kinetic energy flux—and the radar reflectivity. Rather than using the oft-assumed sphericity and solid ice physical properties, actual measurements of hail properties are used in the analysis. Results from the maximum estimated size of hail (MESH) and vertical integrated liquid water (VIL) algorithms are evaluated based on this analysis.
{"title":"Exploring the Composited T-28 Hailstorm Penetration Dataset to Characterize Hail Properties within the Updraft and Downdraft Regions","authors":"Andrew J. Heymsfield, Micael A. Cecchini, Andrew Detwiler, Ryan Honeyager, Paul Field","doi":"10.1175/jamc-d-23-0030.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0030.1","url":null,"abstract":"Abstract Measurements from the South Dakota School of Mines and Technology T-28 hail-penetrating aircraft are analyzed using recently developed data processing techniques with the goals of identifying where the large hail is found relative to vertical motion and improving the detection of hail microphysical properties from radar. Hail particle size distributions (PSD) and environmental conditions (temperature, relative humidity, liquid water content, air vertical velocity) were digitally collected by the T28 between 1995 and 2003 and synthesized by Detwiler et al. (2012). The PSD were forward-modeled by Cecchini et al. (2022) to simulate the radar reflectivity of the PSD at multiple radar wavelengths. The T-28 penetrated temperatures primarily between 0 and −10 °C. The largest hailstones were sampled near the updraft/downdraft interface. Liquid water contents were highest in the updraft cores, whereas total (liquid + frozen) water contents were highest near the updraft/downdraft interface. The fitted properties of the PSD, intercept and slope, are directly related to each other, but do not show any dependence on the region of the hailstorm where sampled. The PSD measurements and the radar reflectivity calculations at multiple radar wavelengths facilitated the development of relationships between the PSD bulk properties—hail kinetic energy and kinetic energy flux—and the radar reflectivity. Rather than using the oft-assumed sphericity and solid ice physical properties, actual measurements of hail properties are used in the analysis. Results from the maximum estimated size of hail (MESH) and vertical integrated liquid water (VIL) algorithms are evaluated based on this analysis.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135739357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-19DOI: 10.1175/jamc-d-22-0187.1
Linye Song, Lu Yang, Conglan Cheng, Aru Hasi, Mingxuan Chen
Abstract This study investigates the impacts of grid spacing and station network on surface analyses and forecasts including temperature, humidity and winds in Beijing Winter Olympic complex terrain. The high-resolution analyses are generated by a rapid-refresh integrated system that includes a topographic downscaling procedure. Results show that surface analyses are more accurate with a higher targeted grid spacing. Particularly, the average analysis errors of surface temperature, humidity, and winds are all significantly reduced when the grid size is increased. This improvement is mainly attributed to a more realistic simulation of the topographic effects in the integrated system because the topographic downscaling at higher grid spacing can add more details in complex mountain region. From 1km to 100m, 1-12h forecasts of temperature and humidity are also largely improved, while the wind only show slight improvement for 1-6h forecasts. The influence of station network on the surface analyses is further examined. Results show that the spatial distributions of temperature and humidity at hundred-meter space scale are more realistic and accurate when adding an intensive automatic weather station network, as more observational information can be absorbed. The adding of station network can also reduce the forecast errors, which can last for about 6 hours. However, although surface winds display better analysis skill when adding more stations, the wind at the mountain top region sometimes encounter a marginally worse effect for both analysis and forecast. The results are helpful to improve the analysis and forecast products in complex terrain, and have some implications for downscaling from coarse grid size to a finer grid.
{"title":"The impacts of grid spacing and station network on surface analyses and forecasts in Beijing Winter Olympic complex terrain","authors":"Linye Song, Lu Yang, Conglan Cheng, Aru Hasi, Mingxuan Chen","doi":"10.1175/jamc-d-22-0187.1","DOIUrl":"https://doi.org/10.1175/jamc-d-22-0187.1","url":null,"abstract":"Abstract This study investigates the impacts of grid spacing and station network on surface analyses and forecasts including temperature, humidity and winds in Beijing Winter Olympic complex terrain. The high-resolution analyses are generated by a rapid-refresh integrated system that includes a topographic downscaling procedure. Results show that surface analyses are more accurate with a higher targeted grid spacing. Particularly, the average analysis errors of surface temperature, humidity, and winds are all significantly reduced when the grid size is increased. This improvement is mainly attributed to a more realistic simulation of the topographic effects in the integrated system because the topographic downscaling at higher grid spacing can add more details in complex mountain region. From 1km to 100m, 1-12h forecasts of temperature and humidity are also largely improved, while the wind only show slight improvement for 1-6h forecasts. The influence of station network on the surface analyses is further examined. Results show that the spatial distributions of temperature and humidity at hundred-meter space scale are more realistic and accurate when adding an intensive automatic weather station network, as more observational information can be absorbed. The adding of station network can also reduce the forecast errors, which can last for about 6 hours. However, although surface winds display better analysis skill when adding more stations, the wind at the mountain top region sometimes encounter a marginally worse effect for both analysis and forecast. The results are helpful to improve the analysis and forecast products in complex terrain, and have some implications for downscaling from coarse grid size to a finer grid.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135060803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-08DOI: 10.1175/jamc-d-23-0092.1
Temple R. Lee, Sandip Pal, Praveena Krishnan, Brian Hirth, M. Heuer, Tilden P. Meyers, Rick D. Saylor, John Schroeder
Surface-layer parameterizations for heat, mass, momentum, and turbulence exchange are a critical component of the land surface models (LSMs) used in weather prediction and climate models. Although formulations derived from Monin-Obukhov Similarity Theory (MOST) have long been used, bulk Richardson (Rib) parameterizations have recently been suggested as a MOST alternative but have been evaluated over a limited number of land cover and climate types. Examining the parameterizations’ applicability over other regions, particularly drylands that cover approximately 41% of terrestrial land surfaces, is a critical step toward implementing the parameterizations into LSMs. One year (1 January through 31 December 2018) of eddy covariance measurements from a 10-m tower in southeastern Arizona and a 200-m tower in western Texas were used to determine how well the Rib parameterizations for friction velocity (u*), sensible heat flux (H), and turbulent kinetic energy (TKE) compare against MOST-derived parameterizations of these quantities. Independent of stability, wind speed regime, and season, the Rib u* and TKE parameterizations performed better than the MOST parameterizations, whereas MOST better represented H. Observations from the 200-m tower indicated that the parameterizations’ performance degraded as a function of height above ground. Overall, the Rib parameterizations revealed promising results, confirming better performance than traditional MOST relationships for kinematic (i.e., u*) and turbulence (i.e., TKE) quantities, although caution is needed when applying the H Rib parameterizations to drylands. These findings represent an important milestone for the use of Rib parameterizations, given the large fraction of Earth’s surface covered by drylands.
{"title":"On the efficacy of Monin-Obukhov and bulk Richardson surface-layer parameterizations over drylands","authors":"Temple R. Lee, Sandip Pal, Praveena Krishnan, Brian Hirth, M. Heuer, Tilden P. Meyers, Rick D. Saylor, John Schroeder","doi":"10.1175/jamc-d-23-0092.1","DOIUrl":"https://doi.org/10.1175/jamc-d-23-0092.1","url":null,"abstract":"\u0000Surface-layer parameterizations for heat, mass, momentum, and turbulence exchange are a critical component of the land surface models (LSMs) used in weather prediction and climate models. Although formulations derived from Monin-Obukhov Similarity Theory (MOST) have long been used, bulk Richardson (Rib) parameterizations have recently been suggested as a MOST alternative but have been evaluated over a limited number of land cover and climate types. Examining the parameterizations’ applicability over other regions, particularly drylands that cover approximately 41% of terrestrial land surfaces, is a critical step toward implementing the parameterizations into LSMs. One year (1 January through 31 December 2018) of eddy covariance measurements from a 10-m tower in southeastern Arizona and a 200-m tower in western Texas were used to determine how well the Rib parameterizations for friction velocity (u*), sensible heat flux (H), and turbulent kinetic energy (TKE) compare against MOST-derived parameterizations of these quantities. Independent of stability, wind speed regime, and season, the Rib u* and TKE parameterizations performed better than the MOST parameterizations, whereas MOST better represented H. Observations from the 200-m tower indicated that the parameterizations’ performance degraded as a function of height above ground. Overall, the Rib parameterizations revealed promising results, confirming better performance than traditional MOST relationships for kinematic (i.e., u*) and turbulence (i.e., TKE) quantities, although caution is needed when applying the H Rib parameterizations to drylands. These findings represent an important milestone for the use of Rib parameterizations, given the large fraction of Earth’s surface covered by drylands.","PeriodicalId":15027,"journal":{"name":"Journal of Applied Meteorology and Climatology","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41761858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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