Winter Orographic Clouds Research Articles

Unraveling ice multiplication in winter orographic clouds via in-situ observations, remote sensing and modeling

Recent years have shown that secondary ice production (SIP) is ubiquitous, affecting all clouds from polar to tropical regions. SIP is not described well in models and may explain biases in warm mixed-phase cloud ice content and structure. Through modeling constrained by in-situ observations and its synergy with radar we show that SIP in orographic clouds exert a profound impact on the vertical distribution of hydrometeors and precipitation, especially in seeder-feeder cloud configurations. The mesoscale model simulations coupled with a radar simulator strongly support that enhanced aggregation and SIP through ice-ice collisions contribute to observed spectral bimodalities, skewing the Doppler spectra toward the slower-falling side at temperatures within the dendritic growth layer, ranging from −20 °C to −10 °C. This unique signature provides an opportunity to infer long-term SIP occurrences from the global cloud radar data archive, particularly for this underexplored temperature regime.

Characteristics of Generating Cells in Wintertime Orographic Clouds

Abstract During the Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE) field campaign, cloud-top generating cells were frequently observed in the very high-resolution W-band airborne cloud radar data. This study examines multiple flight segments from three SNOWIE cases that exhibited cloud-top generating cells structures, focusing on the in situ measurements inside and outside these cells to characterize the microphysics of these cells. The observed generating cells in these three cases occurred in cloud tops of −15° to −30°C, with and without overlying cloud layers, but always with shallow layers of atmospheric instability observed at cloud top. The results also indicate that liquid water content, vertical velocity, and drizzle and ice crystal concentrations are greater inside the generating cells compared to the adjacent portions of the cloud. The generating cells were predominantly <500 m in horizontal width and frequently exhibited drizzle drops coexisting with ice. The particle imagery indicates that ice particle habits included plates, columns, and rimed and irregular crystals, likely formed via primary ice nucleation mechanisms. Understanding the sources of natural ice formation is important to understanding precipitation formation in winter orographic clouds, and is especially relevant for clouds that may be targeted for glaciogenic cloud seeding as well as to improve model representation of these clouds. Significance Statement This study presents the characteristics of cloud-top generating cells in winter orographic clouds, and documents that fine-scale generating cells are ubiquitous in clouds over complex terrain in addition to having been observed in other types of clouds. The generating cells exhibited enhanced concentrations of larger drizzle and ice particles, which suggests the environments of these fine-scale features promote ice formation and growth. The source of ice formation in winter clouds is critical to understanding and modeling the precipitation formation process. Given the ubiquity of cloud-top generating cells in many types of clouds around the world, this study further motivates the need to investigate methods for representing subgrid-scale environments to improve ice formation in numerical models.

On the Radar Detection of Cloud Seeding Effects in Wintertime Orographic Cloud Systems

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 Ze is required to stand out against background natural Ze variability. This analysis considers four radar wavelengths, a range of background ice water contents (IWC) from 0.012 to 1.214 g m−3, and additional IWC introduced by seeding ranging from 0.012 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. Significance Statement Operational glaciogenic seeding programs targeting wintertime orographic clouds are funded by a range of stakeholders to increase snowpack. Glaciogenic seeding signatures have been observed by radar when natural background snowfall is weak but never when heavy background precipitation was present. This analysis quantitatively shows that seeding effects will be undetectable using radar reflectivity under conditions of background snowfall unless the background snowfall is weak, 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. Alternative assessment methods such as trace element analysis in snow, aircraft measurements, precipitation measurements, and modeling should be used to determine the efficacy of orographic cloud seeding when heavy background precipitation is present.

Evaluation of Orographic Cloud Seeding Using a Bin Microphysics Scheme: Three-Dimensional Simulation of Real Cases

AbstractThe University of Pécs and NCAR Bin (UPNB) microphysical scheme was implemented into the mesoscale Weather Research and Forecast (WRF) Model that was used to study the impact of silver iodide (AgI) seeding on precipitation formation in winter orographic clouds. Four different experimental units were chosen from the Wyoming Weather Modification Pilot Project to simulate the seeding effect. The results of the numerical experiments show the following: (i) Comparisons with the soundings, snow gauges, and microwave radiometer data indicate that the three-dimensional simulations with detailed microphysics reasonably represent both the dynamics and the microphysics of real clouds. (ii) The dispersion of the AgI particles from the simulated ground-based seeding was effective because of turbulent mixing. (iii) In the investigated cases (surface temperature is less than 0°C), surface precipitation and precipitation efficiency show low susceptibility to the concentrations of cloud condensation nuclei and natural ice nucleating particles. (iv) If the available liquid water content promotes the enhancement of the number of snowflakes by diffusional growth, the surface precipitation can be increased by more than 5%. A novel parameter relevant to orographic clouds, horizontally integrated liquid water path (LWP), was evaluated to find the relation between seeding efficiency and liquid water content. The impact of seeding is negligible if the horizontal LWP is less than 0.1 mm and is apparent if the horizontal LWP is larger than 1 mm, as based on the cases investigated in this study.

Review of Advances in Precipitation Enhancement Research

AbstractThis paper provides a summary of the assessment report of the World Meteorological Organization (WMO) Expert Team on Weather Modification that discusses recent progress on precipitation enhancement research. The progress has been underpinned by advances in our understanding of cloud processes and interactions between clouds and their environment, which, in turn, have been enabled by substantial developments in technical capabilities to both observe and simulate clouds from the microphysical to the mesoscale. We focus on the two cloud types most commonly seeded in the past: winter orographic cloud systems and convective cloud systems. A key issue for cloud seeding is the extension from cloud-scale research to water catchment–scale impacts on precipitation on the ground. Consequently, the requirements for the design, implementation, and evaluation of a catchment-scale precipitation enhancement campaign are discussed. The paper concludes by indicating the most important gaps in our knowledge. Some recommendations regarding the most urgent research topics are given to stimulate further research.

A Transformational Approach to Winter Orographic Weather Modification Research: The SNOWIE Project

AbstractThe Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) project aims to study the impacts of cloud seeding on winter orographic clouds. The field campaign took place in Idaho between 7 January and 17 March 2017 and employed a comprehensive suite of instrumentation, including ground-based radars and airborne sensors, to collect in situ and remotely sensed data in and around clouds containing supercooled liquid water before and after seeding with silver iodide aerosol particles. The seeding material was released primarily by an aircraft. It was hypothesized that the dispersal of the seeding material from aircraft would produce zigzag lines of silver iodide as it dispersed downwind. In several cases, unambiguous zigzag lines of reflectivity were detected by radar, and in situ measurements within these lines have been examined to determine the microphysical response of the cloud to seeding. The measurements from SNOWIE aim to address long-standing questions about the efficacy of cloud seeding, starting with documenting the physical chain of events following seeding. The data will also be used to evaluate and improve computer modeling parameterizations, including a new cloud-seeding parameterization designed to further evaluate and quantify the impacts of cloud seeding.

Further analysis of a snowfall enhancement project in the Snowy Mountains of Australia

The first phase of the Snowy Precipitation Enhancement Research Project (SPERP-1) was a confirmatory experiment on winter orographic cloud seeding (Manton et al., 2011). Analysis of the data (Manton and Warren, 2011) found that a statistically significant impact of seeding could be obtained by removing any 5-hour experimental units (EUs) for which the amount of released seeding material was below a specified minimum. Analysis of the SPERP-1 data is extended in the present work by first considering the uncertainties in the measurement of precipitation and in the methodology. It is found that the estimation of the natural precipitation in the target area, based solely on the precipitation in the designated control area, is a significant source of uncertainty. A systematic search for optimal predictors shows that both the Froude number of the low-level flow across the mountains and the control precipitation should be used to estimate the natural precipitation. Applying the optimal predictors for the natural precipitation, statistically significant impacts are found using all EUs. This approach also supports a novel analysis of the sensitivity of seeding impacts to environmental variables, such as wind speed and cloud top temperature. The spatial distribution of seeding impact across the target is investigated. Building on the results of SPERP-1, phase 2 of the experiment (SPERP-2) ran from 2010 to 2013 with the target area extended to the north along the mountain ridges. Using the revised methodology, the seeding impacts in SPERP-2 are found to be consistent with those in SPERP-1, provided that the natural precipitation is estimated accurately.

A multi-sensor study of the impact of ground-based glaciogenic seeding on clouds and precipitation over mountains in Wyoming. Part II: Seeding impact analysis

The AgI Seeding Cloud Impact Investigation (ASCII) campaign, conducted in early 2012 and 2013 over two mountain ranges in southern Wyoming, was designed to examine the impact of ground-based glaciogenic seeding on snow growth in winter orographic clouds. Part I of this study (Pokharel and Geerts, 2016) describes the project design, instrumentation, as well as the ambient atmospheric conditions and macrophysical and microphysical properties of the clouds sampled in ASCII. This paper (Part II) explores how the silver iodide (AgI) seeding affects snow growth in these orographic clouds in up to 27 intensive operation periods (IOPs), depending on the instrument used.In most cases, 2h without seeding (NOSEED) were followed by 2h of seeding (SEED). In situ data at flight level (2D-probes) indicate higher concentrations of small snow particles during SEED in convective clouds. The double difference of radar reflectivity Z (SEED−NOSEED in the target region, compared to the same trend in the control region) indicates an increase in Z for the composite of ASCII cases, over either mountain range, and for any of the three radar systems (WCR, MRR, and DOW), each with their own control and target regions, and for an array of snow gauges. But this double difference varies significantly from case to case, which is attributed to uncertainties related to sampling representativeness and to differences in natural trends between control and target regions. We conclude that a sample much larger than ASCII's sample is needed for clear observational evidence regarding the sensitivity of seeding efficacy to atmospheric and cloud conditions.

A multi-sensor study of the impact of ground-based glaciogenic seeding on clouds and precipitation over mountains in Wyoming. Part I: Project description

The AgI Seeding Cloud Impact Investigation (ASCII) campaign was conducted in early 2012 and 2013 over two mountain ranges in southern Wyoming to examine the impact of ground-based glaciogenic seeding on snow growth in winter orographic clouds. The campaign was supported by a network of ground-based instruments, including microwave radiometers, two profiling Ka-band Micro-Rain Radars (MRRs), a Doppler on Wheels (DOW) X-band radar, and a Parsivel disdrometer. The University of Wyoming King Air operated the profiling Wyoming Cloud Radar, the Wyoming Cloud Lidar, and in situ cloud and precipitation particle probes. The characteristics of the orographic clouds, flow field, and upstream stability profiles in 27 intensive observation periods (IOPs) are described here. A composite analysis of the impact of seeding on snow growth is presented in Part II of this study (Pokharel et al., 2017).Clouds were stratiform in most IOPs, but in 10 IOPs convective clouds were present. Most clouds were shallow (~2km deep), all had some liquid water but generally with a liquid water path <0.3mm, and all were naturally precipitating but generally at a rate <1mmh−1.

The Future of Winter Orographic Cloud Seeding: A View from Scientists and Stakeholders

The Future of Winter Orographic Cloud Seeding: A View from Scientists and Stakeholders

Dual-Polarization Radar Data Analysis of the Impact of Ground-Based Glaciogenic Seeding on Winter Orographic Clouds. Part II: Convective Clouds

AbstractThis second paper of a two-part series aims to explore the ground-based glaciogenic seeding impact on wintertime orographic clouds using an X-band dual-polarization radar. It focuses on three cases with shallow to moderately deep orographic convection that were observed in January–February of 2012 as part of the AgI Seeding Cloud Impact Investigation (ASCII) project over the Sierra Madre in Wyoming. In each of the storms the bulk upstream Froude number exceeded 1, suggesting unblocked flow. Low-level potential instability was present, explaining orographic convection. The clouds contained little supercooled liquid water on account of the low cloud-base temperature. Ice-crystal photography shows that snow mainly grew by diffusion and aggregation. To examine the seeding effect of silver iodide (AgI), five study areas are defined: two target areas and three control areas. Comparisons are made between the control and target areas as well as between a treated, or seeded, period and an untreated period. Low-level reflectivity tends to increase in the target areas relative to the control. This increase is larger in the lee target area than in the upwind target area, suggesting that precipitation enhancement is delayed in the presence of convection. The echo tops of the convective cells are not higher during seeding, relative to simultaneous changes in the control regions. This result suggests that the dynamic-seeding mechanism does not apply for the cold-base convective clouds that are studied here. An analysis of differential reflectivity and snow photography suggests that static seeding is the more likely snow-enhancement mechanism in these clouds.

Dual-Polarization Radar Data Analysis of the Impact of Ground-Based Glaciogenic Seeding on Winter Orographic Clouds. Part I: Mostly Stratiform Clouds

AbstractThe impact of ground-based glaciogenic seeding on wintertime orographic, mostly stratiform clouds is analyzed by means of data from an X-band dual-polarization radar, the Doppler-on-Wheels (DOW) radar, positioned on a mountain pass. This study focuses on six intensive observation periods (IOPs) during the 2012 AgI Seeding Cloud Impact Investigation (ASCII) project in Wyoming. In all six storms, the bulk upstream Froude number below mountaintop exceeded 1 (suggesting unblocked flow), the clouds were relatively shallow (with bases below freezing), some liquid water was present, and orographic flow conditions were mostly steady. To examine the silver iodide (AgI) seeding effect, three study areas are defined (a control area, a target area upwind of the crest, and a lee target area), and comparisons are made between measurements from a treated period and those from an untreated period. Changes in reflectivity and differential reflectivity observed by the DOW at low levels during seeding are consistent with enhanced snow growth, by vapor diffusion and/or aggregation, for a case study and for the composite analysis of all six IOPs, especially at close range upwind of the mountain crest. These low-level changes may have been affected by natural changes aloft, however, as evident from differences in the evolution of the echo-top height in the control and target areas. Even though precipitation in the target region is strongly correlated with that in the control region, the authors cannot definitively attribute the change to seeding because there is a lack of knowledge about natural variability, nor can the outcome be generalized, because the sample size is small.

A numerical study of winter orographic seeding experiments in Korea using the Weather Research and Forecasting model

Ice nucleation processes by silver iodide were parameterized and implemented into the Weather Research and Forecasting model to perform winter orographic cloud seeding experiment in an eastern mountainous region of the Korean Peninsula. Cloud seeding at a mountain site resulted in production of ice crystals, mostly by deposition and condensation freezing nucleation of seeding material and depletion of water drops by ice crystals themselves and by snow and graupel particles grown from these ice crystals but importantly precipitation increased over the target area to the west of the seeding site. Sensitivity test showed that increasing the release rate of seeding material led to enhanced precipitation. Interestingly, dominant ice crystal nucleation mode was different for different aerosol concentrations: deposition and condensation freezing nucleation were dominantly responsible for ice crystal formation for maritime aerosol type (i.e., low concentration) while the dominant mode was contact freezing nucleation for continental aerosol type (i.e., high concentration). When seeding material was released at a low-altitude site (i.e., upslope of mountain), it was not successfully transported upward to the target area but instead dispersed along the direction of the mountain ridges by the barrier jets.

A Case Study on the Impact of Ground-based Glaciogenic Seeding on Winter Orographic Clouds at Daegwallyeong

The purpose of this study was to investigate the impact of ground-based glaciogenic seeding on orographic clouds in the Daegwallyeong area on 13 March, 2013. The experiments was conducted by releasing silver iodide (AgI) under following conditions: surface temperature below , wind direction between 45 and , and wind speed less than . Two seeding rates, (SR1) and (SR2), were tested to obtain an appropriate AgI ratio for snowfall enhancement in the Daegwallyeong area. Numerical simulations were carried out by using the WRF (Weather Research and Forecast) model with AgI point-source module which predicted dispersion fields of AgI particles. The results indicated that the target orographic clouds contained adequate amount of supercooled liquid water and that the dispersion of AgI particles tended to move along the prevailing wind direction. To validate the seeding effects, the observation data from FM-120 and MPS as well as PARSIVEL disdrometer were analyzed. In this case study, glaciogenic seeding significantly increased the concentration of small ice particles below 1 mm in diameter. The observation results suggest that SR1 seeding be reasonable to use the ground-based seeding in the Daegwallyeong area.

Estimating the Fraction of Winter Orographic Precipitation Produced under Conditions Meeting the Seeding Criteria for the Wyoming Weather Modification Pilot Project

AbstractAnnual precipitation increases of 10% or more are often quoted for the impact of winter orographic cloud seeding; however, establishing the basis for such values is problematic for two reasons. First, the impact of glaciogenic seeding of candidate orographic storms has not been firmly established. Second, not all winter precipitation is produced by candidate “seedable” storms. Addressing the first question motivated the Wyoming state legislature to fund a multiyear, crossover, randomized cloud-seeding experiment in southeastern Wyoming to quantify the impact of glaciogenic seeding of wintertime orographic clouds. The crossover design requires two barriers, one randomly selected for seeding, for comparisons of seeded and nonseeded precipitation under relatively homogeneous atmospheric conditions. Addressing the second question motivated the work here. The seeding criteria—700-hPa temperatures ≤−8°C, 700-hPa winds between 210° and 315°, and the presence of supercooled liquid water—were applied to eight winters to determine the percent of winter precipitation that may fall under the seeding criteria. Since no observational datasets provide precipitation and all of the atmospheric variables required for this study, a regional climate model dynamical downscaling of historical data over 8 years was used. The accuracy of the model was tested against several measurements, and the small model biases were removed. On average, ~26% of the time between 15 November and 15 April atmospheric conditions were seedable over the barriers in southeastern Wyoming. These seedable conditions were accompanied by precipitation ~12%–14% of the time, indicating that ~27%–30% of the winter precipitation resulted from seedable clouds.

The Impact of Glaciogenic Seeding on Snowfall from Shallow Orographic Clouds over the Medicine Bow Mountains in Wyoming

The 2013 AgI Seeding Cloud Impact Investigation (ASCII-13) campaign was conducted over the Medicine Bow range in Wyoming to examine the impact of ground-based glaciogenic seeding on winter orographic clouds and precipitation. The campaign was supported by a network of ground-based instruments, included a microwave radiometer, two profiling Ka-band radars, rawinsonde launches, and a disdrometer. The University of Wyoming King Air with profiling Wyoming Cloud Radar (WCR) conducted eight successful flights in ASCII-13. WCR profiles from these flights are combined with those from seven other flights, which followed the same geographically-fixed pattern in 2008-09.A case study shows that a clear seeding signature is not apparent in individual WCR reflectivity transects downwind of the silver iodide (AgI) generators, and that natural trends in precipitation over short timescales can easily overwhelm any seeding impact. Therefore the ASCII experimental design included control regions, both upwind of the AgI generators and to the side of the estimated AgI nuclei plumes. Frequency-by-altitude displays show slightly higher reflectivity values during seeding near the ground, at least when compared to the control regions. The near-surface precipitation rate trend from the untreated to the treated period in the target region, compared to that in the control region, varies significantly from flight to flight, according to the WCR reflectivity data within the boundary layer. Most of this variation relates to non-homogenous natural trends across the mountain range, and/or to sample unrepresentativeness, esp. for the control region. While WCR reflectivity profiles from flights over the Medicine Bow range do not show a significant increase in near-surface precipitation during seeding (in comparison with upstream trends), similar data from nine separate flights in 2012 over an adjacent range, the Sierra Madre, do.

A Brief History of Evaluations Performed on the Operational Kings River Winter Orographic Cloud Seeding Program

Abstract: An operational winter orographic cloud seeding program has been conducted in the Kings River Drainage located in the southern Sierra Nevada Mountains of California most winter seasons since water year 1955. Both ground based and airborne seeding modes have been used to disperse silver iodide into naturally occurring winter storms. Several evaluations have been performed to estimate the effectiveness of this seeding program. These evaluations have considered different seeded time periods dependent upon when the evaluation work was published. Since the program has not been randomized, these evaluations have all been based upon the historical target/control technique. Most of these evaluations have used annual streamflow as the response variable. One recent analysis was based upon April 1st snow water content. Control sites were selected from the Yosemite National Park region, an unseeded area, and southern Sierra Nevada sites located south of the Kings River Drainage. Linear regression equations were developed relating the control and target areas annual streamflow values during historical periods without any seeding. High correlations were obtained with r2 values ranging from 0.90 to 0.98. Both linear and multi-linear equations were developed for April 1st snow water contents. High correlations were obtained with r2 values ranging from 0.91 to 0.93. When these equations were used to predict the amount of natural streamflow or snow water contents during seeded years and then compared to the observed values during the seeded years, the average estimated increases in annual streamflow ranged from +3.3 to +6.1%. Similarly, the estimated increases in April 1st snow water content ranged from +4.9% (linear regression) to +5.7% (multi-linear regression).

Evaluating Winter Orographic Cloud Seeding: Design of the Wyoming Weather Modification Pilot Project (WWMPP)

AbstractAn overview of the Wyoming Weather Modification Pilot Project (WWMPP) is presented. This project, funded by the State of Wyoming, is designed to evaluate the effectiveness of cloud seeding with silver iodide in the Medicine Bow and Sierra Madre Ranges of south-central Wyoming. The statistical evaluation is based on a randomized crossover design for the two barriers. The description of the experimental design includes the rationale behind the design choice, the criteria for case selection, facilities for operations and evaluation, and the statistical analysis approach. Initial estimates of the number of cases needed for statistical significance used historical Snow Telemetry (SNOTEL) data (1987–2006), prior to the beginning of the randomized seeding experiment. Refined estimates were calculated using high-resolution precipitation data collected during the initial seasons of the project (2007–10). Comparing the sample size estimates from these two data sources, the initial estimates are reduced to 236 (110) for detecting a 10% (15%) change. The sample size estimates are highly dependent on the assumed effect of seeding, on the correlations between the two target barriers and between the target and control sites, and on the variance of the response variable, namely precipitation. In addition to the statistical experiment, a wide range of physical studies and ancillary analyses are being planned and conducted.

On the buffering of CCN impacts on wintertime orographic clouds: An idealized examination

This study examines the role that cloud base height (or cloud base temperature) plays in the response of orographic precipitation to enhanced potential cloud condensation nuclei (CCN). A series of 2-D simulations along a transect of the Sierra Nevada was run at cloud-resolving scale to adequately represent the microphysical processes that lead to orographic precipitation, varying CCN concentrations for different cloud base temperature regimes. Cloud-base heights were systematically varied by modifying low-level moisture. Sensitivity runs indicate that for lower cloud base heights, the potential for drizzle (warm rain) formation increases such that at some point increased CCN concentrations can suppress drizzle formation leading to greater amounts of supercooled liquid water contents and then riming is enhanced with increased CCN concentrations. As a result ice-phase precipitation can be enhanced for low cloud base height clouds. This suggests that the conclusion from previous studies that enhanced CCN reduce precipitation cannot be generalized to warmer-based winter orographic clouds.

Supercooled Liquid Water Concentrations in Winter Orographic Clouds from Ground-base Ice Accretion Measurements

An icing rate detector originally designed for aircraft is used to measure supercooled liquid water in winter orographic clouds at a fixed mountain-top site in the central Sierra Nevada of California. Supercooled liquid water concentrations have been determined using continuous records of rime ice accretion and windspeed. It is shown that supercooled liquid water is occurring within larger portions of storms than prior airborne observations over the operational area have indicated, particularly during pre-frontal periods. In many instances, supercooled liquid water occurs below safe aircraft operational altitudes over the mountainous project area. The ground-based measurementsystem provides an effective tool for semi-quan- titative determination of supercooled liquid water within specific cloud volumes heretofore unmeasured.