Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations

Abstract This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.

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Vertical Velocity and Microphysical Distributions Related to Rapid Intensification in a Simulation of Hurricane Dennis (2005)

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-016.1 ◽

2012 ◽

Vol 69 (12) ◽

pp. 3515-3534 ◽

Cited By ~ 24

Author(s):

Greg M. McFarquhar ◽

Brian F. Jewett ◽

Matthew S. Gilmore ◽

Stephen W. Nesbitt ◽

Tsung-Lin Hsieh

Keyword(s):

Vertical Velocity ◽

Model Simulation ◽

Weather Research And Forecasting ◽

Rapid Intensification ◽

Latent Heating ◽

Replicated Data ◽

Convective Bursts ◽

Before And After ◽

Hurricane Dennis ◽

Upward Flux

Abstract A 1-km Weather Research and Forecasting model simulation of Hurricane Dennis was used to identify precursors in vertical velocity and latent heating distributions to rapid intensification (RI). Although the observed structure qualitatively replicated data obtained during P-3 and Earth Resources-2 (ER-2) flights, the simulated reflectivity was overestimated. During the 6 h preceding RI, defined as 0000 UTC 8 July 2005 close to the time of simulated maximum central pressure deepening, the asymmetric convection transformed into an eyewall with the maximum 10-m wind speed increasing by 16 m s−1. Contour by frequency altitude diagrams showed unique changes in the breadth of simulated vertical velocity (w) distributions before and after RI. Outliers of w distributions at 14 km preceded RI onset, whereas the increase in w outliers at 6 km lagged it. Prior to RI there was an increase in the upward flux of hydrometeors between 10 and 15 km, with increased contributions from w > 6 m s−1. Increases in lower-level updraft airmass fluxes did not lead RI, but the 14-km positive w outliers were better indicators of RI onset than positive w averages. The area of convective bursts did not strongly increase before RI, but it continually increased after RI. Latent heating was dominated by contributions from w < 2 m s−1, meaning increases in positive w outliers before RI did not cause the increase in latent heating seen during RI. The location of convective bursts and outliers of positive and negative w distributions contracted toward the eye as the simulated Dennis intensified.

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Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-7155-2011 ◽

2011 ◽

Vol 11 (14) ◽

pp. 7155-7170 ◽

Cited By ~ 26

Author(s):

Y. Liu ◽

W. Wu ◽

M. P. Jensen ◽

T. Toto

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Cloud Fraction ◽

Shortwave Radiation ◽

Cloud Radiative Forcing ◽

Analytical Expression ◽

Cloud Albedo ◽

Annual Variations ◽

Hourly Data ◽

Radiation Parameterizations

Abstract. This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction, and cloud albedo. The analytical expression is then used to deduce a new approach for inferring cloud albedo from concurrent surface-based measurements of downwelling surface shortwave radiation and cloud fraction. High-resolution decade-long data on cloud albedos are obtained by use of this surface-based approach over the US Department of Energy's Atmospheric Radiaton Measurement (ARM) Program at the Great Southern Plains (SGP) site. The surface-based cloud albedos are further compared against those derived from the coincident GOES satellite measurements. The three long-term (1997–2009) sets of hourly data on shortwave cloud radiative forcing, cloud fraction and cloud albedo collected over the SGP site are analyzed to explore the multiscale (diurnal, annual and inter-annual) variations and covariations. The analytical formulation is useful for diagnosing deficiencies of cloud-radiation parameterizations in climate models.

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Estimating Changes in Temperature Distributions in a Large Ensemble of Climate Simulations Using Quantile Regression

Journal of Climate ◽

10.1175/jcli-d-17-0782.1 ◽

2018 ◽

Vol 31 (20) ◽

pp. 8573-8588 ◽

Cited By ~ 11

Author(s):

Matz A. Haugen ◽

Michael L. Stein ◽

Elisabeth J. Moyer ◽

Ryan L. Sriver

Keyword(s):

Quantile Regression ◽

Radiative Forcing ◽

Initial Conditions ◽

Model Simulation ◽

Extreme Temperature ◽

Single Model ◽

New Approach ◽

Temperature Distributions ◽

Climate Simulations ◽

Community Earth System Model

Understanding future changes in extreme temperature events in a transient climate is inherently challenging. A single model simulation is generally insufficient to characterize the statistical properties of the evolving climate, but ensembles of repeated simulations with different initial conditions greatly expand the amount of data available. We present here a new approach for using ensembles to characterize changes in temperature distributions based on quantile regression that more flexibly characterizes seasonal changes. Specifically, our approach uses a continuous representation of seasonality rather than breaking the dataset into seasonal blocks; that is, we assume that temperature distributions evolve smoothly both day to day over an annual cycle and year to year over longer secular trends. To demonstrate our method’s utility, we analyze an ensemble of 50 simulations of the Community Earth System Model (CESM) under a scenario of increasing radiative forcing to 2100, focusing on North America. As previous studies have found, we see that daily temperature bulk variability generally decreases in wintertime in the continental mid- and high latitudes (>40°). A more subtle result that our approach uncovers is that differences in two low quantiles of wintertime temperatures do not shrink as much as the rest of the temperature distribution, producing a more negative skew in the overall distribution. Although the examples above concern temperature only, the technique is sufficiently general that it can be used to generate precise estimates of distributional changes in a broad range of climate variables by exploiting the power of ensembles.

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Relationship between Shortwave Cloud Radiative Forcing and Local Meteorological Variables Compared in Observations and Several Global Climate Models

Journal of Climate ◽

10.1175/jcli3875.1 ◽

2006 ◽

Vol 19 (17) ◽

pp. 4344-4359 ◽

Cited By ~ 12

Author(s):

Markus Stowasser ◽

Kevin Hamilton

Keyword(s):

Relative Humidity ◽

Vertical Velocity ◽

Radiative Forcing ◽

Large Scale ◽

Climate Models ◽

Grid Point ◽

Global Climate Models ◽

Coupled Models ◽

Cloud Radiative Forcing ◽

Cloud Forcing

Abstract The relations between local monthly mean shortwave cloud radiative forcing and aspects of the resolved-scale meteorological fields are investigated in hindcast simulations performed with 12 of the global coupled models included in the model intercomparison conducted as part of the preparation for Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In particular, the connection of the cloud forcing over tropical and subtropical ocean areas with resolved midtropospheric vertical velocity and with lower-level relative humidity are investigated and compared among the models. The model results are also compared with observational determinations of the same relationships using satellite data for the cloud forcing and global reanalysis products for the vertical velocity and humidity fields. In the analysis the geographical variability in the long-term mean among all grid points and the interannual variability of the monthly mean at each grid point are considered separately. The shortwave cloud radiative feedback (SWCRF) plays a crucial role in determining the predicted response to large-scale climate forcing (such as from increased greenhouse gas concentrations), and it is thus important to test how the cloud representations in current climate models respond to unforced variability. Overall there is considerable variation among the results for the various models, and all models show some substantial differences from the comparable observed results. The most notable deficiency is a weak representation of the cloud radiative response to variations in vertical velocity in cases of strong ascending or strong descending motions. While the models generally perform better in regimes with only modest upward or downward motions, even in these regimes there is considerable variation among the models in the dependence of SWCRF on vertical velocity. The largest differences between models and observations when SWCRF values are stratified by relative humidity are found in either very moist or very dry regimes. Thus, the largest errors in the model simulations of cloud forcing are prone to be in the western Pacific warm pool area, which is characterized by very moist strong upward currents, and in the rather dry regions where the flow is dominated by descending mean motions.

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Composited structure of shallow cumulus clouds

10.5194/egusphere-egu21-3180 ◽

2021 ◽

Author(s):

Chris Holloway ◽

Jian-Feng Gu ◽

Bob Plant ◽

Todd Jones

Keyword(s):

Kinetic Energy ◽

Vertical Velocity ◽

Inversion Layer ◽

Potential Temperature ◽

Vertical Wind Shear ◽

Theoretical Models ◽

Turbulence Kinetic Energy ◽

Cloud Base ◽

Asymmetric Structures ◽

Negatively Buoyant

<div> <div> <div> <div> <p>The normalized distributions of thermodynamic and dynamical variables both within and outside shallow clouds are investigated through a composite algorithm using large eddy&#160;simulation of the BOMEX case. The normalized magnitude is&#160;maximum near cloud center and decreases outwards. While&#160;relative humidity (RH) and cloud liquid water (<em>q<sub>l&#160;</sub></em>) decrease&#160;smoothly to match the environment, the vertical velocity,&#160;virtual potential temperature (<em>&#952;<sub>v&#160;</sub></em>) and potential temperature&#160;(<em>&#952;</em>) perturbations have more complicated behaviour towards the cloud boundary. Below the inversion layer, <em>&#952;<sub>v</sub></em> becomes&#160;<span>negative before the vertical velocity has turned from updraft to subsiding shell outside the cloud, indicating the presence of a transition zone where the updraft is negatively buoyant. Due to the downdraft outside the cloud and the enhanced horizontal turbulent mixing across the edge, the normalized turbulence kinetic energy (TKE) and horizontal turbulence kinetic energy (HTKE) decrease more slowly from the cloud center outwards than the thermodynamic variables. The distributions all present asymmetric structures in response to the vertical wind shear, with more negatively buoyant air, stronger downdrafts and larger TKE on the downshear side. We discuss several implications of the distributions for theoretical models and parameterizations. Positive buoyancy near cloud base is mostly due to&#160;</span><span>the virtual effect of water vapor, emphasising the role of moisture in triggering. The mean vertical velocity is found&#160;</span><span>to be approximately half the maximum vertical velocity within each cloud, providing a constraint on some models. Finally, products of normalized distributions for different variables are shown to be able to well represent the vertical heat and moisture fluxes, but they underestimate fluxes in the inversion layer because they do not capture cloud top downdrafts.</span></p> </div> </div> </div> </div>

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Pathways to the Production of Precipitating Hydrometeors and Tropical Cyclone Development

Monthly Weather Review ◽

10.1175/mwr-d-15-0363.1 ◽

2016 ◽

Vol 144 (6) ◽

pp. 2395-2420 ◽

Cited By ~ 5

Author(s):

J.-W. Bao ◽

S. A. Michelson ◽

E. D. Grell

Keyword(s):

Tropical Cyclone ◽

Wrf Model ◽

Cloud Microphysics ◽

Weather Research And Forecasting ◽

Rapid Intensification ◽

Latent Heating ◽

Vertical Distributions ◽

Double Moment ◽

Microphysical Processes ◽

Definition Of

Abstract Pathways to the production of precipitation in two cloud microphysics schemes available in the Weather Research and Forecasting (WRF) Model are investigated in a scenario of tropical cyclone intensification. Comparisons of the results from the WRF Model simulations indicate that the variation in the simulated initial rapid intensification of an idealized tropical cyclone is due to the differences between the two cloud microphysics schemes in their representations of pathways to the formation and growth of precipitating hydrometeors. Diagnoses of the source and sink terms of the hydrometeor budget equations indicate that the major differences in the production of hydrometeors between the schemes are in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes, such as accretion growth and sedimentation. These differences lead to different horizontally averaged vertical profiles of net latent heating rate associated with significantly different horizontally averaged vertical distributions and production rates of hydrometeors in the simulated clouds. Results from this study also highlight the possibility that the advantage of double-moment formulations can be overshadowed by the uncertainties in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes.

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The Role of Vortex and Environment Errors in Genesis Forecasts of Hurricanes Danielle and Karl (2010)

Monthly Weather Review ◽

10.1175/mwr-d-12-00086.1 ◽

2013 ◽

Vol 141 (1) ◽

pp. 232-251 ◽

Cited By ~ 24

Author(s):

Ryan D. Torn ◽

David Cook

Keyword(s):

Water Vapor ◽

Vortex Structure ◽

Wind Shear ◽

Initial Conditions ◽

Vertical Wind Shear ◽

Environmental Parameters ◽

Empirical Orthogonal Functions ◽

Vertical Wind ◽

Orthogonal Functions ◽

Water Vapor Mixing Ratio

Abstract An ensemble of Weather Research and Forecasting Model (WRF) forecasts initialized from a cycling ensemble Kalman filter (EnKF) system is used to evaluate the sensitivity of Hurricanes Danielle and Karl’s (2010) genesis forecasts to vortex and environmental initial conditions via ensemble sensitivity analysis. Both the Danielle and Karl forecasts are sensitive to the 0-h circulation associated with the pregenesis system over a deep layer and to the temperature and water vapor mixing ratio within the vortex over a comparatively shallow layer. Empirical orthogonal functions (EOFs) of the 0-h ensemble kinematic and thermodynamic fields within the vortex indicate that the 0-h circulation and moisture fields covary with one another, such that a stronger vortex is associated with higher moisture through the column. Forecasts of the pregenesis system intensity are only sensitive to the leading mode of variability in the vortex fields, suggesting that only specific initial condition perturbations associated with the vortex will amplify with time. Multivariate regressions of the vortex EOFs and environmental parameters believed to impact genesis suggest that the Karl forecast is most sensitive to the vortex structure, with smaller sensitivity to the upwind integrated water vapor and 200–850-hPa vertical wind shear magnitude. By contrast, the Danielle forecast is most sensitive to the vortex structure during the first 24 h, but is more sensitive to the 200-hPa divergence and vertical wind shear magnitude at longer forecast hours.

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Assessing the Potential of a Long-Term Climate Forecast for Cuba Using the WRF Model

Environmental Sciences Proceedings ◽

10.3390/ecas2021-10338 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Lourdes Álvarez-Escudero ◽

Yandy G. Mayor ◽

Israel Borrajero-Montejo ◽

Arnoldo Bezanilla-Morlot

Keyword(s):

Mesoscale Model ◽

Initial Conditions ◽

Wrf Model ◽

Reanalysis Data ◽

Weather Research And Forecasting ◽

Tropical Storms ◽

Precipitation Regime ◽

Wide Debate ◽

One Year ◽

Cumulative Precipitation

Seasonal climatic prediction studies are a matter of wide debate all over the world. Cuba, a mainly agricultural nation, should greatly benefit from the knowledge, which is available months in advance of the precipitation regime and allows for the proper management of water resources. In this work, a series of six experiments were made with a mesoscale model WRF (Weather Research and Forecasting Model) that produced a 15-month forecast for each month of cumulative precipitation starting at two dates, and for three non-consecutive years with different meteorological characteristics: one dry year (2004), one year that started dry and turned rainy (2005), and one year where several tropical storms occurred (2008). ERA-Interim reanalysis data were used for the initial and border conditions and experiments started 1 month before the beginning of the rainy and the dry seasons, respectively. In a general sense, the experience of using WRF indicated that it was a valid resource for seasonal forecast, since the results obtained were in the same range as those reported by the literature for similar cases. Several limitations were revealed by the results: the forecasts underestimated the monthly cumulative precipitation figures, tropical storms entering through the borders sometimes followed courses different from the real courses inside the working domain, storms that developed inside the domain were not reproduced by WRF, and differences in initial conditions led to significantly different forecasts for the corresponding time steps (nonlinearity). Changing the model parameterizations and initial conditions of the ensemble forecast experiments was recommended.

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PRELIMINARY STUDY OF HORIZONTAL AND VERTICAL WIND PROFILE OF QUASI-LINEAR CONVECTIVE UTILIZING WEATHER RADAR OVER WESTERN JAVA REGION, INDONESIA

International Journal of Remote Sensing and Earth Sciences (IJReSES) ◽

10.30536/j.ijreses.2018.v15.a3075 ◽

2019 ◽

Vol 15 (2) ◽

pp. 177

Author(s):

Abdullah Ali ◽

Riris Adrianto ◽

Miming Saepudin

Keyword(s):

Velocity Profile ◽

Vertical Velocity ◽

Wind Shear ◽

Vertical Wind Shear ◽

Convective Cloud ◽

Vertical Wind ◽

Squall Line ◽

Vertical Velocity Profile ◽

Preliminary Study ◽

Wind Profiles

One of the weather phenomena that potentially cause extreme weather conditions is the linear-shaped mesoscale convective systems, including squall lines. The phenomenon that can be categorized as a squall line is a convective cloud pair with the linear pattern of more than 100 km length and 6 hours lifetime. The new theory explained that the cloud system with the same morphology as squall line without longevity threshold. Such a cloud system is so-called Quasi-Linear Convective System (QLCS), which strongly influenced by the ambient dynamic processes, include horizontal and vertical wind profiles. This research is intended as a preliminary study for horizontal and vertical wind profiles of QLCS developed over the Western Java region utilizing Doppler weather radar. The following parameters were analyzed in this research, include direction pattern and spatial-temporal significance of wind speed, divergence profile, vertical wind shear (VWS) direction, and intensity profiles, and vertical velocity profile. The subjective and objective analysis was applied to explain the characteristics and effects of those parameters to the orientation of propagation, relative direction, and speed of the cloud system’s movement, and the lifetime of the system. Analysis results showed that the movement of the system was affected by wind direction and velocity patterns. The divergence profile combined with the vertical velocity profile represents the inflow which can supply water vapor for QLCS convective cloud cluster. Vertical wind shear that effect QLCS system is only its direction relative to the QLCS propagation, while the intensity didn’t have a significant effect.

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Analysis of Total Column CO<sub>2</sub> and CH<sub>4</sub> Measurements in Berlin with WRF-GHG

10.5194/acp-2018-1116 ◽

2019 ◽

Author(s):

Xinxu Zhao ◽

Julia Marshall ◽

Stephan Hachinger ◽

Christoph Gerbig ◽

Jia Chen

Keyword(s):

Urban Areas ◽

Initial Conditions ◽

Ghg Emissions ◽

Concentration Field ◽

Weather Research And Forecasting ◽

Background Concentration ◽

Wind Fields ◽

Simulated Wind ◽

Global Population ◽

Good Agreement

Abstract. Though they cover less than 3 % of the global land area, urban areas are responsible for over 70 % of the global greenhouse gas (GHG) emissions and contain 55 % of the global population. A quantitative tracking of GHG emissions in urban areas is therefore of great importance, with the aim of accurately assessing the amount of emissions and identifying the emission sources. The Weather Research and Forecasting model (WRF) coupled with GHG modules (WRF-GHG) developed for mesoscale atmospheric GHG transport, can predict column-averaged abundances of CO2 and CH4 (XCO2 and XCH4). In this study, we use WRF-GHG to model the Berlin area at a high spatial resolution of 1 km. The simulated wind and concentration fields were compared with the measurements from a campaign performed around Berlin in 2014 (Hase et al., 2015). The measured and simulated wind fields mostly demonstrate good agreement and the simulated XCO2 agrees well with the measurement. In contrast, a bias in the simulated XCH4 of around 2.7 % is found, caused by relatively high initialization values for the background concentration field. We find that an analysis using differential column methodology (DCM) works well for the XCH4 comparison, as corresponding background biases then cancel out. From the tracer analysis, we find that the enhancement of XCH4 is highly dependent on human activities. The XCO2 signal in the vicinity of Berlin is dominated by anthropogenic behavior rather than biogenic activities. We conclude that DCM is an effective method for comparing models to observations independently of biases caused, e.g., by initial conditions. It allows us to use our high resolution WRF-GHG model to detect and understand sources of GHG emissions quantitatively in urban areas.

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