scholarly journals High-resolution stable isotope signature of a land-falling Atmospheric River in southern Norway

2020 ◽  
Author(s):  
Yongbiao Weng ◽  
Harald Sodemann ◽  
Aina Johannessen
Keyword(s):  
High Resolution ◽  
Water Vapour ◽  
Isotope Composition ◽  
Cloud Microphysics ◽  
Convective Precipitation ◽  
Cloud Base ◽  
Near Surface ◽  
Surface Precipitation ◽  
Moisture Source ◽  
Isotopic Signal

Abstract. Heavy precipitation at the west coast of Norway is often connected to elongated meridional structures of high integrated water vapour transport known as Atmospheric Rivers (AR). Here we present high-resolution measurements of stable isotopes in water vapour and precipitation during a land-falling AR event in western Norway on 07 December 2016. In our analysis, we aim to identify the influences of moisture source conditions, weather system characteristics, and post-condensation processes on the isotopic signal in near-surface water vapour and surface precipitation. A total of 71 precipitation samples were collected during the 24-h sampling period, mostly taken at sampling intervals of 10–20 min. The isotope composition of near-surface vapour was continuously monitored in-situ with a cavity ring-down spectrometer. Local meteorological conditions were in addition observed from a vertical pointing rain radar, a laser disdrometer, and automatic weather stations. We observe a stretched, W-shaped evolution of isotope composition during the event. Combining isotopic and meteorological observations, we define four different stages of the event. The two most depletion periods in the isotope δ values are associated with frontal transitions, namely a combination of two warm fronts that follow each other within a few hours, and an upper-level cold front. The d-excess shows a single maximum, and a step-wise decline in both precipitation and a gradual decrease in near-surface vapour. Thereby, isotopic evolution of the near-surface vapour closely follows the precipitation with a time delay of about 30 min, except for the first stage of the event. Analysis using an isotopic below-cloud exchange framework shows that the initial period of low and even negative d-excess in precipitation was caused by evaporation below cloud base. At the ground, a near-constant signal representative of the airmass above is only reached after transition periods of several hours. Moisture source diagnostics for the event show that the moisture source conditions for these steady periods are partly reflected in the surface precipitation at these times. Based on our observations, we revisit the interpretation of precipitation isotope measurements during AR events in previous studies. Given that the isotopic signal in surface precipitation reflects a combination of atmospheric dynamics through moisture sources and atmospheric distillation, as well as cloud microphysics and below-cloud processes, we recommend caution regarding how Rayleigh distillation models are used during data interpretation. While the isotope composition in water vapour during convective precipitation events may be more adequately represented by idealized Rayleigh models, additional factors should be taken into account when interpreting a surface precipitation isotope signal from stratiform clouds.

scholarly journals High-resolution stable isotope signature of a land-falling atmospheric river in southern Norway

2021 ◽  
Vol 2 (3) ◽  
pp. 713-737
Author(s):  
Yongbiao Weng ◽  
Aina Johannessen ◽  
Harald Sodemann
Keyword(s):  
Surface Water ◽  
High Resolution ◽  
Water Vapour ◽  
Isotope Composition ◽  
Initial Period ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Near Surface ◽  
Surface Precipitation ◽  
Moisture Source

Abstract. Heavy precipitation at the west coast of Norway is often connected to elongated meridional structures of high integrated water vapour transport known as atmospheric rivers (ARs). Here we present high-resolution measurements of stable isotopes in near-surface water vapour and precipitation during a land-falling AR in southwestern Norway on 7 December 2016. In our analysis, we aim to identify the influences of moisture source conditions, weather system characteristics, and post-condensation processes on the isotope signal in near-surface water vapour and precipitation. A total of 71 precipitation samples were collected during the 24 h sampling period, mostly taken at sampling intervals of 10–20 min. The isotope composition of near-surface vapour was continuously monitored in situ with a cavity ring-down spectrometer. Local meteorological conditions were in addition observed from a vertical pointing rain radar, a laser disdrometer, and automatic weather stations. We observe a stretched, “W”-shaped evolution of isotope composition during the event. Combining paired precipitation and vapour isotopes with meteorological observations, we define four different stages of the event. The two most depleted periods in the isotope δ values are associated with frontal transitions, namely a combination of two warm fronts that follow each other within a few hours and an upper-level cold front. The d-excess shows a single maximum and a step-wise decline in precipitation and a gradual decrease in near-surface vapour. Thereby, the isotopic evolution of the near-surface vapour closely follows that of the precipitation with a time delay of about 30 min, except for the first stage of the event. Analysis using an isotopic below-cloud exchange framework shows that the initial period of low and even negative d-excess in precipitation was caused by evaporation below cloud base. The isotope signal from the cloud level became apparent at ground level after a transition period that lasted up to several hours. Moisture source diagnostics for the periods when the cloud signal dominates show that the moisture source conditions are then partly reflected in surface precipitation and water vapour isotopes. In our study, the isotope signal in surface precipitation during the AR event reflects the combined influence of atmospheric dynamics, moisture sources, and atmospheric distillation, as well as cloud microphysics and below-cloud processes. Based on this finding, we recommend careful interpretation of results obtained from Rayleigh distillation models in such events, in particular for the interpretation of surface vapour and precipitation from stratiform clouds.

High-resolution stable isotope signature of a land-falling Atmospheric River in southern Norway

2021 ◽  
Author(s):  
Weng Yongbiao ◽  
Aina Johannessen ◽  
Harald Sodemann
Keyword(s):  
Surface Water ◽  
High Resolution ◽  
Stable Isotope ◽  
Water Vapour ◽  
Isotope Composition ◽  
Convective Precipitation ◽  
Near Surface ◽  
Surface Precipitation ◽  
Moisture Sources ◽  
Isotopic Signal

<p>Heavy precipitation at the west coast of Norway is often connected to high integrated water vapour transport within Atmospheric Rivers (AR). Here we present high-resolution measurements of stable isotopes in near-surface water vapour and precipitation during a land-falling AR event in southwestern Norway on 07 December 2016. We analyze the influences of moisture sources, weather system characteristics, and post-condensation processes on the isotopic signal in near-surface water vapour and precipitation.</p><p>During the 24-h sampling period, a total of 71 precipitation samples were collected, sampled at intervals of 10-20 min. The isotope composition of near-surface vapour was continuously monitored with a cavity ring-down spectrometer. In addition, local meteorological conditions were monitored from a vertical pointing rain radar, a laser disdrometer, and automatic weather stations.</p><p>During the event, we observe a "W"-shaped evolution of the stable isotope composition. Combining isotopic and meteorological observations, we define four different stages of the event. The two most depletion periods in the isotope δ values are associated with frontal transitions, namely a combination of two warm fronts that follow each other within a few hours, and an upper-level cold front. The d-excess shows a single maximum, and a step-wise decline in precipitation and a gradual decrease in near-surface vapour. Thereby, isotopic evolution of the near-surface vapour closely follows the precipitation with a time delay of about 30 min, except for the first stage of the event. Analysis using an isotopic below-cloud exchange model shows that the initial period of low and even negative d-excess in precipitation was most likely caused by evaporation below cloud base. At the ground, a near-constant signal representative of the airmass above is only reached after transition periods of several hours. For these steady periods, the moisture source conditions are partly reflected in the surface precipitation.</p><p>Based on our observations, we revisit the interpretation of precipitation isotope measurements during AR events in previous studies. Given that the isotopic signal in surface precipitation reflects a combination of atmospheric dynamics through moisture sources and atmospheric distillation, as well as cloud microphysics and below-cloud processes, we recommend caution regarding how Rayleigh distillation models are used during data interpretation. While the isotope compositions during convective precipitation events may be more adequately represented by idealized Rayleigh models, additional factors should be taken into account when interpreting a surface precipitation isotope signal from stratiform clouds.</p>

Water vapour and precipitation isotope measurements from different platforms during the IGP campaign, Iceland, in 2018 connect evaporation sources to precipitation sinks

2020 ◽  
Author(s):  
Harald Sodemann ◽  
Alexandra Touzeau ◽  
Chris Barrell ◽  
John F. Burkhart ◽  
Andrew Elvidge ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Data Quality ◽  
Water Vapour ◽  
Isotope Composition ◽  
Cloud Microphysics ◽  
Heat Fluxes ◽  
The Arctic ◽  
Stable Water Isotopes ◽  
Coupled Models ◽  
Isotope Measurements

<p>The water cycle in atmospheric and coupled models is a major contributor to model uncertainty, in particular at high-latitudes, where contrasts between ice-covered regions and the open ocean fuel intense heat fluxes. However, observed atmospheric vapour concentrations do not allow us to disentangle the contributions of different processes, such as evaporation, mixing, and cloud microphysics, to the overall moisture budget. As a natural tracer, stable water isotopes provide access to the moisture sources and phase change history of atmospheric water vapour and precipitation.</p><p>Here we present a unique dataset of stable isotope measurements in water vapour and precipitation from the IGP (Iceland Greenland Seas Project) field campaign that took place during February and March 2018. The dataset includes simultaneous measurements from three platforms (a land-station at Husavik, Iceland, the R/V Alliance, and a Twin Otter aircraft) during winter conditions in the Arctic region. Precipitation was collected on an event basis on the research ship, and along two north-south transects in Northern Iceland, and analysed at two stable isotope laboratories. Airborne vapour isotope data was obtained from 10 flights covering a large geographic range (64 °N to 72 °N). Careful data treatment was applied to all stable isotope measurements to ensure sufficient data quality in a challenging measurement environment with predominantly cold and dry conditions, and characterised by strong isotope and humidity gradients. Data quality was confirmed by inter-comparison of the vapour isotope measurements both between ship and aircraft, and between the aircraft and Husavik station.</p><p>We exemplify the value of the observations from the analysis of several flights dedicated to the study of the atmosphere-ocean interactions, from low-levels legs and vertical sections across the boundary layer during Cold Air Outbreak (CAO) conditions. The precipitation in Northern Iceland collected at the precipitation sampling network shows clear co-variation with the upstream water vapour measurements at Husavik station, indicative of the wider spatial representativeness of the isotope signals. The land-based snow and vapour measurements are furthermore consistent with the isotope composition in upstream ocean regions sampled by the research vessel, and as linked from aircraft measurements.</p>

scholarly journals Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea ice to open ocean

2016 ◽  
Author(s):  
G. Young ◽  
H. M. Jones ◽  
T. W. Choularton ◽  
J. Crosier ◽  
K. N. Bower ◽  
...  
Keyword(s):  
Sea Ice ◽  
Liquid Water Content ◽  
Cloud Microphysics ◽  
Heat Fluxes ◽  
The Arctic ◽  
Cloud Base ◽  
Surface Boundary ◽  
Sea Ice Extent ◽  
Near Surface

Abstract. In situ airborne observations of cloud microphysics, aerosol properties and thermodynamic structure over the transition from sea ice to ocean are presented from the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign. A case study from 23 March 2013 provides a unique view of the cloud microphysical changes over this transition under cold air outbreak conditions. Cloud base and depth both increased over this transition, and mean droplet number concentrations also increased from approximately 80 cm−3 over the sea ice to 90 cm−3 over the ocean. The ice properties of the cloud remained approximately constant. Observed ice crystal concentrations averaged approximately 0.5–1.5 L−1, suggesting only primary ice nucleation was active; however, there was evidence of crystal fragmentation at cloud base over the ocean. The liquid-water content increased almost four-fold over the transition and this, in conjunction with the deeper cloud layer, allowed rimed snowflakes to develop which precipitated out of cloud base. Little variation in aerosol particle number concentrations was observed between the different surface conditions; however, some variability with altitude was observed, with notably greater concentrations measured at higher altitudes (> 800 m) over the sea ice. Near-surface boundary layer temperatures increased by 13 °C from sea ice to ocean, with corresponding increases in surface heat fluxes and turbulent kinetic energy. These significant thermodynamic changes were concluded to be the primary driver of the microphysical evolution of the cloud. This study represents the first investigation, using in situ airborne observations, of cloud microphysical changes with changing sea ice cover and addresses the question of how the microphysics of Arctic stratiform clouds may change as the region warms and sea ice extent reduces.

scholarly journals Improving High-Resolution Weather Forecasts Using the Weather Research and Forecasting (WRF) Model with an Updated Kain–Fritsch Scheme

2016 ◽  
Vol 144 (3) ◽  
pp. 833-860 ◽  
Author(s):  
Yue Zheng ◽  
Kiran Alapaty ◽  
Jerold A. Herwehe ◽  
Anthony D. Del Genio ◽  
Dev Niyogi
Keyword(s):  
High Resolution ◽  
Initial Conditions ◽  
Spatial Scales ◽  
Wrf Model ◽  
Cloud Microphysics ◽  
Cumulus Parameterization ◽  
Subgrid Scale ◽  
Grid Spacing ◽  
Dynamic Adjustment ◽  
Surface Precipitation

Abstract Efforts to improve the prediction accuracy of high-resolution (1–10 km) surface precipitation distribution and variability are of vital importance to local aspects of air pollution, wet deposition, and regional climate. However, precipitation biases and errors can occur at these spatial scales due to uncertainties in initial meteorological conditions and/or grid-scale cloud microphysics schemes. In particular, it is still unclear to what extent a subgrid-scale convection scheme could be modified to bring in scale awareness for improving high-resolution short-term precipitation forecasts in the WRF Model. To address these issues, the authors introduced scale-aware parameterized cloud dynamics for high-resolution forecasts by making several changes to the Kain–Fritsch (KF) convective parameterization scheme in the WRF Model. These changes include subgrid-scale cloud–radiation interactions, a dynamic adjustment time scale, impacts of cloud updraft mass fluxes on grid-scale vertical velocity, and lifting condensation level–based entrainment methodology that includes scale dependency. A series of 48-h retrospective forecasts using a combination of three treatments of convection (KF, updated KF, and the use of no cumulus parameterization), two cloud microphysics schemes, and two types of initial condition datasets were performed over the U.S. southern Great Plains on 9- and 3-km grid spacings during the summers of 2002 and 2010. Results indicate that 1) the source of initial conditions plays a key role in high-resolution precipitation forecasting, and 2) the authors’ updated KF scheme greatly alleviates the excessive precipitation at 9-km grid spacing and improves results at 3-km grid spacing as well. Overall, the study found that the updated KF scheme incorporated into a high-resolution model does provide better forecasts for precipitation location and intensity.

scholarly journals Differences between the Surface Precipitation Estimates from the TRMM Precipitation Radar and Passive Microwave Radiometer Version 7 Products

2014 ◽  
Vol 15 (6) ◽  
pp. 2157-2175 ◽  
Author(s):  
Chuntao Liu ◽  
Edward Zipser
Keyword(s):  
Large Scale ◽  
Microwave Radiometer ◽  
North Indian Ocean ◽  
Passive Microwave ◽  
Convective Precipitation ◽  
Trade Wind ◽  
Precipitation Radar ◽  
Near Surface ◽  
Surface Precipitation ◽  
East Pacific

Abstract With 15 yr of the Tropical Rainfall Measuring Mission (TRMM) observations, the passive microwave radiometers [TRMM Microwave Imager (TMI)] and the precipitation radar (PR) report a close geographical distribution of annual precipitation between 36°S and 36°N. However, large discrepancies between PR and TMI precipitation retrievals are also found over several specific regions, such as central Africa, the Amazon, the tropical east Pacific, and north Indian Ocean. To understand these discrepancies, the PR near-surface and the TMI surface precipitation retrievals are compared at both pixel and precipitation system levels using collocated pixels and a precipitation feature database from 1998 to 2012. Over land, the TMI overestimates precipitation in deep and intense convective systems, but misses significant amounts of warm rainfall in shallow systems. Over the ocean, because of the partial beam filling of large footprints of the lower-frequency sensors, the TMI reports a larger precipitation area than the PR and underestimates the precipitation rate in the convective precipitation region. The TMI tends to overestimate precipitation compared to the PR in a large proportion of shallow systems over the tropical east Pacific and trade wind regions with large-scale descent. The PR tends to overestimate precipitation compared to the TMI in a large proportion of shallow systems over rainy oceans, such as the west Pacific and the Atlantic ITCZ. All these findings imply that there are still large uncertainties in the precipitation climatology over some regions. Further ground validation campaigns are still needed, especially over the ocean.

scholarly journals On the Vertical Structure of Modeled and Observed Deep Convective Storms: Insights for Precipitation Retrieval and Microphysical Parameterization

2005 ◽  
Vol 44 (12) ◽  
pp. 1866-1884 ◽  
Author(s):  
Jamie L. Smedsmo ◽  
Efi Foufoula-Georgiou ◽  
Venugopal Vuruputur ◽  
Fanyou Kong ◽  
Kelvin Droegemeier
Keyword(s):  
High Resolution ◽  
Vertical Structure ◽  
Weather Prediction ◽  
Cloud Microphysics ◽  
Future Research ◽  
Surface Precipitation ◽  
Convective Storms ◽  
Precipitation Forecasting ◽  
Radar Echoes ◽  
Microphysical Parameterization

Abstract An understanding of the vertical structure of clouds is important for remote sensing of precipitation from space and for the parameterization of cloud microphysics in numerical weather prediction (NWP) models. The representation of cloud hydrometeor profiles in high-resolution NWP models has direct applications in inversion-type precipitation retrieval algorithms [e.g., the Goddard profiling (GPROF) algorithm used for retrieval of precipitation from passive microwave sensors] and in quantitative precipitation forecasting. This study seeks to understand how the vertical structure of hydrometeors (liquid and frozen water droplets in a cloud) produced by high-resolution NWP models with explicit microphysics, henceforth referred to as cloud-resolving models (CRMs), compares to observations. Although direct observations of 3D hydrometeor fields are not available, comparisons of modeled and observed radar echoes can provide some insight into the vertical structure of hydrometeors and, in turn, into the ability of CRMs to produce precipitation structures that are consistent with observations. Significant differences are revealed between the vertical structure of observed and modeled clouds of a severe midlatitude storm over Texas for which the surface precipitation is reasonably well captured. Possible reasons for this discrepancy are presented, and the need for future research is highlighted.

scholarly journals Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea ice to open ocean

2016 ◽  
Vol 16 (21) ◽  
pp. 13945-13967 ◽  
Author(s):  
Gillian Young ◽  
Hazel M. Jones ◽  
Thomas W. Choularton ◽  
Jonathan Crosier ◽  
Keith N. Bower ◽  
...  
Keyword(s):  
Sea Ice ◽  
Cloud Microphysics ◽  
Heat Fluxes ◽  
Cloud Layer ◽  
The Arctic ◽  
Cloud Base ◽  
Surface Boundary ◽  
Sea Ice Extent ◽  
Near Surface

Abstract. In situ airborne observations of cloud microphysics, aerosol properties, and thermodynamic structure over the transition from sea ice to ocean are presented from the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign. A case study from 23 March 2013 provides a unique view of the cloud microphysical changes over this transition under cold-air outbreak conditions. Cloud base lifted and cloud depth increased over the transition from sea ice to ocean. Mean droplet number concentrations, Ndrop, also increased from 110 ± 36 cm−3 over the sea ice to 145 ± 54 cm−3 over the marginal ice zone (MIZ). Downstream over the ocean, Ndrop decreased to 63 ± 30 cm−3. This reduction was attributed to enhanced collision-coalescence of droplets within the deep ocean cloud layer. The liquid water content increased almost four fold over the transition and this, in conjunction with the deeper cloud layer, allowed rimed snowflakes to develop and precipitate out of cloud base downstream over the ocean. The ice properties of the cloud remained approximately constant over the transition. Observed ice crystal number concentrations averaged approximately 0.5–1.5 L−1, suggesting only primary ice nucleation was active; however, there was evidence of crystal fragmentation at cloud base over the ocean. Little variation in aerosol particle number concentrations was observed between the different surface conditions; however, some variability with altitude was observed, with notably greater concentrations measured at higher altitudes ( >  800 m) over the sea ice. Near-surface boundary layer temperatures increased by 13 °C from sea ice to ocean, with corresponding increases in surface heat fluxes and turbulent kinetic energy. These significant thermodynamic changes were concluded to be the primary driver of the microphysical evolution of the cloud. This study represents the first investigation, using in situ airborne observations, of cloud microphysical changes with changing sea ice cover and addresses the question of how the microphysics of Arctic stratiform clouds may change as the region warms and sea ice extent reduces.

scholarly journals Geophysical investigations for stability and safety mitigation of regional crude-oil pipeline near abandoned coal mines

2021 ◽  
Vol 18 (1) ◽  
pp. 145-162
Author(s):  
B Butchibabu ◽  
Prosanta Kumar Khan ◽  
P C Jha
Keyword(s):  
High Resolution ◽  
Crude Oil ◽  
Seismic Refraction ◽  
High Resolution Imaging ◽  
Weak Zone ◽  
Near Surface ◽  
Oil Pipeline ◽  
Refraction Tomography ◽  
Geophysical Investigations ◽  
Resolution Imaging

Abstract This study aims for the protection of a crude-oil pipeline, buried at a shallow depth, against a probable environmental hazard and pilferage. Both surface and borehole geophysical techniques such as electrical resistivity tomography (ERT), ground penetrating radar (GPR), surface seismic refraction tomography (SRT), cross-hole seismic tomography (CST) and cross-hole seismic profiling (CSP) were used to map the vulnerable zones. Data were acquired using ERT, GPR and SRT along the pipeline for a length of 750 m, and across the pipeline for a length of 4096 m (over 16 profiles of ERT and SRT with a separation of 50 m) for high-resolution imaging of the near-surface features. Borehole techniques, based on six CSP and three CST, were carried out at potentially vulnerable locations up to a depth of 30 m to complement the surface mapping with high-resolution imaging of deeper features. The ERT results revealed the presence of voids or cavities below the pipeline. A major weak zone was identified at the central part of the study area extending significantly deep into the subsurface. CSP and CST results also confirmed the presence of weak zones below the pipeline. The integrated geophysical investigations helped to detect the old workings and a deformation zone in the overburden. These features near the pipeline produced instability leading to deformation in the overburden, and led to subsidence in close vicinity of the concerned area. The area for imminent subsidence, proposed based on the results of the present comprehensive geophysical investigations, was found critical for the pipeline.

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