Impacts of Multi-Timescale Circulations on Meridional Moisture Transport

2021 ◽  
pp. 1-64
Author(s):  
Qiao Liu ◽  
Tim Li ◽  
Weican Zhou
Keyword(s):  
Moisture Transport ◽  
Baroclinic Instability ◽  
Wrf Model ◽  
Phase Relationship ◽  
Reanalysis Data ◽  
Specific Humidity ◽  
Small Contribution ◽  
Wind Variability ◽  
The Mean ◽  
Meridional Moisture Transport

AbstractRelative impacts of the climatological annual mean, the climatological annual variation, the synoptic, the intra-seasonal and the inter-annual flows on meridional moisture transport were investigated based on reanalysis data. Due to an in-phase relationship between the poleward wind and specific humidity, the synoptic and intra-seasonal motions contribute about 50% and 30% of the maximum zonal and annual mean poleward moisture transport in the middle latitudes, respectively. The preferred latitudinal location (40°N or S) of the maximum zonal mean moisture transport by the synoptic motion is attributed to the combined effect of the maximum wind variability poleward of 40°N or S in association with atmospheric baroclinic instability and the maximum moisture variability equatorward of 40°N or S in association with the anomalous advection of the mean moisture. While the MJO and ENSO have a small contribution to the long-term mean transport, they may strongly affect regional moisture transport through interaction with the mean moisture and through the modulation to higher-frequency modes. A statistical relationship between tropical cyclone (TC) moisture and intensity was constructed based on a large number of high-resolution Weather Research and Forecasting (WRF) model simulations, and the so-derived relationship was further applied to estimate TC moisture transport. It is found that TC transport accounts for about 30% (53%) of the climatological seasonal mean total moisture transport over key northern (southern) hemispheric TC track regions in the northern (southern) hemispheric TC season.

scholarly journals A Comparison of Initial Developments Between Explosive and Ordinary Mid-latitude Cyclones Off the East Asian Coast in Winter

2021 ◽  
Author(s):  
Xiaoyu Gao ◽  
Ping Lu ◽  
Yang Hu ◽  
Shuqin Zhang ◽  
Xiaoyan Sun ◽  
...  
Keyword(s):  
Human Life ◽  
East Asian ◽  
Baroclinic Instability ◽  
Wrf Model ◽  
Detailed Comparison ◽  
Static Stability ◽  
Reanalysis Data ◽  
Sensitivity Experiment ◽  
Initial Development ◽  
Explosive Cyclones

Abstract Explosive cyclones (ECs) off the East Asian coast post challenges in forecasting and significant threats to human life and property. In searching for the key features that distinguish explosive cyclones (ECs) from ordinary extratropical cyclones (OCs), this study presents detailed comparison of winter ECs versus OCs in the perspective of potential vorticity (PV) using 10 years of reanalysis data with high temporal and spatial resolutions. ECs feature greater low-level baroclinity and stronger PV than OCs. The decomposition of local PV tendency shows the important contribution of cold advection (with correlation coefficient of 0.8) in the initial development of ECs. A stronger cold advection for ECs increases upstream static stability, leading to intrusion of higher PV along the steeper isentropic surfaces. The importance of cold advection is further proved by numerical experiments with the Weather Research and Forecast (WRF) model on a typical winter EC. The weakening of cold advection within low-troposphere in sensitivity experiment can significantly decrease PV and stop the cyclone from explosive deepening. In addition to the consensus that diabatic processes play important roles in the intensification of explosive cyclogenesis, this study emphasizes the importance of horizontal cold advection (which is also associated with baroclinic instability) in the preconditioning PV for explosive cyclogenesis.

Precipitation over the Southern Ocean: synoptic analysis and model evaluation using ground-based remote sensing and in-situ measurements

2021 ◽  
Author(s):  
Diogo Luis ◽  
Irina Gorodetskaya ◽  
Katherine Leonard ◽  
Elisabeth Schlosser ◽  
Etienne Vignon ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Moisture Transport ◽  
Precipitation Amount ◽  
Wrf Model ◽  
Reanalysis Data ◽  
In Situ Measurements ◽  
High Temporal Resolution ◽  
Prediction System ◽  
Pressure Ridge

<p>Precipitation is still a poorly known variable in the Southern Ocean/Antarctica due to the lack of measurements. Unique precipitation measurements were carried out during the Swiss Polar Institute’s Antarctic Circumnavigation Expedition (ACE) (December 2016 - March 2017). High temporal resolution measurements of precipitation were performed by a Snow Particle Counter (SPC) and by a micro rain radar (MRR) aboard the RV Akademik Tryoshnikov. Radiosondes were launched periodically to observe the vertical structure of the atmosphere. Additionally, MRR and radiosonde measurements from Dumont D’Urville station (DDU) were available when the expedition was in the Mertz Glacier region. These data offer a rare opportunity to evaluate model and reanalysis products performance in a region without regular precipitation measurements. In this study, ECMWF’s ERA5 reanalysis product and Antarctic Mesoscale Prediction System (AMPS) model data are evaluated using ACE and DDU in-situ observations. Two snowfall events that occurred around Mertz Glacier during the ACE campaign were chosen to compare ERA5 and AMPS data with in-situ measurements. The first event on 2 February 2017 was associated with an extratropical cyclone east of Adelie Land and a moderate along-shore moisture transport. The second event on 8-10 February 2017 was associated with a cyclone west of Mertz blocked by a high-pressure ridge, directing an intense moisture transport (identified as an atmospheric river) and precipitation to DDU. To assess if ERA5 reanalysis and AMPS (Antarctic Mesoscale Prediction System using Polar-WRF model) are able to represent these different types of precipitation events, we analyse the differences in precipitation amount between in-situ, model and reanalysis data and compare modelled vertical profiles with radiosonde measurements.</p>

scholarly journals TRACKING THE ORIGIN OF MOISTURE OVER SERBIA USING THE LAGRANGIAN METHOD

2018 ◽  
Vol 8 (2) ◽  
Author(s):  
MILICA STOJANOVIĆ ◽  
DANICA ĆIRIĆ ◽  
RAQUEL NIETO ◽  
ANITA DRUMOND ◽  
EVICA STOJILJKOVIĆ ◽  
...  
Keyword(s):  
Key Words ◽  
Moisture Transport ◽  
Dispersion Model ◽  
Reanalysis Data ◽  
Particle Dispersion ◽  
Lagrangian Method ◽  
Specific Humidity ◽  
Atmospheric Moisture ◽  
Moisture Sources ◽  
Evaporation Minus Precipitation

In this study, we investigate the sources of moisture over Serbia using a Lagrangian method based on the FLEXPART V9.0 particle dispersion model combined with ERA-Interim reanalysis data, to track changes in atmospheric moisture. This approach computes the budget of evaporation-minus-precipitation by calculating changes in specific humidity along forward and backward trajectories. We considered a period of 34 years, from 1980 to 2014, which allowed the identification of climatological moisture sources and moisture transport towards the country. The results showed that Serbia receive moisture mainly from two sources: the Mediterranean Sea which is the dominant source during the winter (October-March) and the own region which predominate during the summer (April-September). Key words: moisture sources, Flexpart, Lagrangian method, Serbia

scholarly journals Observations and Modeling of Atmospheric Profiles in the Arctic Seasonal Ice Zone

2015 ◽  
Vol 143 (1) ◽  
pp. 39-53 ◽  
Author(s):  
Zheng Liu ◽  
Axel Schweiger ◽  
Ron Lindsay
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Wrf Model ◽  
Specific Humidity ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
Low Level ◽  
The Mean ◽  
Seasonal Ice Zone

Abstract The authors use the Polar Weather Research and Forecasting (WRF) Model to simulate atmospheric conditions during the Seasonal Ice Zone Reconnaissance Survey (SIZRS) in the summer of 2013 over the Beaufort Sea. With the SIZRS dropsonde data, the performance of WRF simulations and two forcing datasets is evaluated: the Interim ECMWF Re-Analysis (ERA-Interim) and the Global Forecast System (GFS) analysis. General features of observed mean profiles, such as low-level temperature inversion, low-level jet (LLJ), and specific humidity inversion are reproduced by all three models. A near-surface warm bias and a low-level moist bias are found in ERA-Interim. WRF significantly improves the mean LLJ, with a lower and stronger jet and a larger turning angle than the forcing. The improvement in the mean LLJ is likely related to the lower values of the boundary layer diffusion in WRF than in ERA-Interim and GFS, which also explains the lower near-surface temperature in WRF than the forcing. The relative humidity profiles have large differences between the observations, the ERA-Interim, and the GFS. The WRF simulated relative humidity closely resembles the forcings, suggesting the need to obtain more and better-calibrated humidity data in this region. The authors find that the sea ice concentrations in the ECMWF model are sometimes significantly underestimated due to an inappropriate thresholding mechanism. This thresholding affects both ERA-Interim and the ECMWF operational model. The scale of impact of this issue on the atmospheric boundary layer in the marginal ice zone is still unknown.

scholarly journals Comparing Sudden Stratospheric Warming Definitions in Reanalysis Data*

2015 ◽  
Vol 28 (17) ◽  
pp. 6823-6840 ◽  
Author(s):  
Froila M. Palmeiro ◽  
David Barriopedro ◽  
Ricardo García-Herrera ◽  
Natalia Calvo
Keyword(s):  
Seasonal Cycle ◽  
Winter Season ◽  
Reanalysis Data ◽  
Sudden Stratospheric Warming ◽  
Pronounced Increase ◽  
Future Studies ◽  
Common Peak ◽  
Before And After ◽  
The Mean ◽  
Large Case

Abstract Sudden stratospheric warmings (SSWs) are characterized by a pronounced increase of the stratospheric polar temperature during the winter season. Different definitions have been used in the literature to diagnose the occurrence of SSWs, yielding discrepancies in the detected events. The aim of this paper is to compare the SSW climatologies obtained by different methods using reanalysis data. The occurrences of Northern Hemisphere SSWs during the extended-winter season and the 1958–2014 period have been identified for a suite of eight representative definitions and three different reanalyses. Overall, and despite the differences in the number and exact dates of occurrence of SSWs, the main climatological signatures of SSWs are not sensitive to the considered reanalysis. The mean frequency of SSWs is 6.7 events decade−1, but it ranges from 4 to 10 events, depending on the method. The seasonal cycle of events is statistically indistinguishable across definitions, with a common peak in January. However, the multidecadal variability is method dependent, with only two definitions displaying minimum frequencies in the 1990s. An analysis of the mean signatures of SSWs in the stratosphere revealed negligible differences among methods compared to the large case-to-case variability within a given definition. The stronger and more coherent tropospheric signals before and after SSWs are associated with major events, which are detected by most methods. The tropospheric signals of minor SSWs are less robust, representing the largest source of discrepancy across definitions. Therefore, to obtain robust results, future studies on stratosphere–troposphere coupling should aim to minimize the detection of minor warmings.

Study of the Mechanisms of Vortex Variability in the Lofoten Basin Based on the Energy Analysis

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
V. S. Travkin ◽  
◽  
T. V. Belonenko ◽  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Baroclinic Instability ◽  
Positive Trend ◽  
Barotropic Instability ◽  
Available Potential Energy ◽  
Conversion Rates ◽  
Order Of Magnitude ◽  
The Mean ◽  
Mean Kinetic Energy

Purpose. The Lofoten Basin is one of the most energetic zones of the World Ocean characterized by high activity of mesoscale eddies. The study is aimed at analyzing different components of general energy in the basin, namely the mean kinetic and vortex kinetic energy calculated using the integral of the volume of available potential and kinetic energy of the Lofoten Vortex, as well as variability of these characteristics. Methods and Results. GLORYS12V1 reanalysis data for the period 2010–2018 were used. The mean kinetic energy and the eddy kinetic one were analyzed; and as for the Lofoten Vortex, its volume available potential and kinetic energy were studied. The mesoscale activity of eddies in winter is higher than in summer. Evolution of the available potential energy and kinetic energy of the Lofoten Vortex up to the 1000 m horizon was studied. It is shown that the vortex available potential energy exceeds the kinetic one by an order of magnitude, and there is a positive trend with the coefficient 0,23⋅1015 J/year. It was found that in the Lofoten Basin, the intermediate layer from 600 to 900 m made the largest contribution to the potential energy, whereas the 0–400 m layer – to kinetic energy. The conversion rates of the mean kinetic energy into the vortex kinetic one and the mean available potential energy into the vortex available potential one (barotropic and baroclinic instability) were analyzed. It is shown that the first type of transformation dominates in summer, while the second one is characterized by its increase in winter. Conclusions. The vertical profile shows that the kinetic energy of eddies in winter is higher than in summer. The available potential energy of a vortex is by an order of magnitude greater than the kinetic energy. An increase in the available potential energy is confirmed by a significant positive trend and by a decrease in the vortex Burger number. The graphs of the barotropic instability conversion rate demonstrate the multidirectional flows in the vortex zone with the dipole structure observed in a winter period, and the tripole one – in summer. The barotropic instability highest intensity is observed in summer. The baroclinic instability is characterized by intensification of the regime in winter that is associated with weakening of stratification in this period owing to winter convection.

scholarly journals Empirical atmospheric thresholds for debris flows and flash floods in the southern French Alps

2014 ◽  
Vol 14 (6) ◽  
pp. 1517-1530 ◽  
Author(s):  
T. Turkington ◽  
J. Ettema ◽  
C. J. van Westen ◽  
K. Breinl
Keyword(s):  
Debris Flows ◽  
Warning System ◽  
Flash Floods ◽  
Rain Gauge ◽  
Reanalysis Data ◽  
Specific Humidity ◽  
Atmospheric Conditions ◽  
Convective Rainfall ◽  
French Alps ◽  
Mountainous Regions

Abstract. Debris flows and flash floods are often preceded by intense, convective rainfall. The establishment of reliable rainfall thresholds is an important component for quantitative hazard and risk assessment, and for the development of an early warning system. Traditional empirical thresholds based on peak intensity, duration and antecedent rainfall can be difficult to verify due to the localized character of the rainfall and the absence of weather radar or sufficiently dense rain gauge networks in mountainous regions. However, convective rainfall can be strongly linked to regional atmospheric patterns and profiles. There is potential to employ this in empirical threshold analysis. This work develops a methodology to determine robust thresholds for flash floods and debris flows utilizing regional atmospheric conditions derived from ECMWF ERA-Interim reanalysis data, comparing the results with rain-gauge-derived thresholds. The method includes selecting the appropriate atmospheric indicators, categorizing the potential thresholds, determining and testing the thresholds. The method is tested in the Ubaye Valley in the southern French Alps (548 km2), which is known to have localized convection triggered debris flows and flash floods. This paper shows that instability of the atmosphere and specific humidity at 700 hPa are the most important atmospheric indicators for debris flows and flash floods in the study area. Furthermore, this paper demonstrates that atmospheric reanalysis data are an important asset, and could replace rainfall measurements in empirical exceedance thresholds for debris flows and flash floods.

scholarly journals Using Empirical Orthogonal Teleconnections to evaluate interannual rainfall variability over China in the Met Office Unified Model Global Atmosphere 6.0 and Global Coupled 2.0 configurations

2017 ◽  
Author(s):  
Claudia Christine Stephan ◽  
Nicholas P. Klingaman ◽  
Pier Luigi Vidale ◽  
Andrew G. Turner ◽  
Marie-Estelle Demory ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Rainfall Variability ◽  
Reanalysis Data ◽  
Horizontal Resolution ◽  
Unified Model ◽  
Seasonal Precipitation ◽  
Climate Simulations ◽  
Interannual Rainfall Variability ◽  
The Mean

Abstract. Six climate simulations of the Met Office Unified Model Global Atmosphere 6.0 and Global Coupled 2.0 configurations are evaluated against observations and reanalysis data for their ability to simulate the mean state and year-to-year variability of precipitation over China. To analyze the sensitivity to air-sea coupling and horizontal resolution, atmosphere-only and coupled integrations at atmospheric horizontal resolutions of N96, N216 and N512 (corresponding to ~ 200, 90, and 40 km in the zonal direction at the equator, respectively) are analyzed. The mean and interannual variance of seasonal precipitation are too high in all simulations over China, but improve with finer resolution and coupling. Empirical Orthogonal Teleconnection (EOT) analysis is applied to simulated and observed precipitation to identify spatial patterns of temporally coherent interannual variability in seasonal precipitation. To connect these patterns to large-scale atmospheric and coupled air-sea processes, atmospheric and oceanic fields are regressed onto the corresponding seasonal-mean timeseries. All simulations reproduce the observed leading pattern of interannual rainfall variability in winter, spring and autumn; the leading pattern in summer is present in all but one simulation. However, only in two simulations are the four leading patterns associated with the observed physical mechanisms. Coupled simulations capture more observed patterns of variability and associate more of them with the correct physical mechanism, compared to atmosphere-only simulations at the same resolution. However, finer resolution does not improve the fidelity of these patterns or their associated mechanisms. This shows that evaluating climate models by only geographical distribution of mean precipitation and its interannual variance is insufficient. The EOT analysis adds knowledge about coherent variability and associated mechanisms.

scholarly journals The Realization of Extreme Tornadic Storm Events under Future Anthropogenic Climate Change

2016 ◽  
Vol 29 (14) ◽  
pp. 5251-5265 ◽  
Author(s):  
Robert J. Trapp ◽  
Kimberly A. Hoogewind
Keyword(s):  
Climate Change ◽  
Convective Available Potential Energy ◽  
Wrf Model ◽  
Real Data ◽  
Anthropogenic Climate Change ◽  
Basic Question ◽  
Storm Events ◽  
The Mean ◽  
Atmospheric State ◽  
Convection Initiation

Abstract This research seeks to answer the basic question of how current-day extreme tornadic storm events might be realized under future anthropogenic climate change. The pseudo global warming (PGW) methodology was adapted for this purpose. Three contributions to the CMIP5 archive were used to obtain the mean 3D atmospheric state simulated during May 1990–99 and May 2090–99. The climate change differences (or Δs) in temperature, relative humidity, pressure, and winds were added to NWP analyses of three high-end tornadic storm events, and this modified atmospheric state was then used for initial and boundary conditions for real-data WRF Model simulations of the events at high resolution. Comparison of an ensemble of these simulations with control simulations (CTRL) facilitated assessment of PGW effects. In contrast to the robust development of supercellular convection in each CTRL, the combined effects of increased convective inhibition (CIN) and decreased parcel lifting under PGW led to a failure of convection initiation in many of the experiments. Those experiments that had sufficient matching between the CIN and lifting tended to generate stronger convective updrafts than CTRL, although not in proportion to the projected higher levels of convective available potential energy (CAPE) under PGW. In addition, the experiments with enhanced updrafts also tended to have enhanced vertical rotation. In fact, such supercellular convection was even found in simulations that were driven with PGW-reduced environmental wind shear. Notably, the PGW modifications did not induce a change in the convective morphology in any of the PGW experiments with significant convective storminess.

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