scholarly journals Seeking for key meteorological parameters to better understand Hector

2015 ◽  
Vol 3 (6) ◽  
pp. 3621-3653
Author(s):  
S. Gentile ◽  
R. Ferretti
Keyword(s):  
Potential Energy ◽  
Meteorological Parameters ◽  
Mesoscale Model ◽  
Initial Conditions ◽  
Convective Available Potential Energy ◽  
Surface Wind ◽  
Type A ◽  
Weather Forecasts ◽  
Low Level ◽  
Available Potential Energy

Abstract. Twelve Hector events, a storm developing in the northern Australia, are analyzed to the aim of identifying the main meteorological parameters involved in the convective development. Based on Crook's ideal study \\citep{Crook} wind speed and direction, wind shear, water vapor, Convective Available Potential Energy and type of convection are the parameters used for this analysis. Both European Centre for Medium-Range Weather Forecasts (ECMWF) analysis and high resolution simulations from the Fifth-Generation Mesoscale Model (MM5) are used. The MM5 simulations are used to connect the mean vertical velocity to the total condensate at the maximum stage and to study the dynamics of the storms. The ECMWF analysis are used to evaluate the initial conditions and the environmental fields contributing to Hector development. The analysis suggests that the strength of convection is largely contributing to the vertical distribution of hydrometeors. The role of total condensate and mean lifting vs. low level moisture, Convective Available Potential Energy, surface wind and direction is analyzed for shear and no-shear conditions to evaluate the differences between type A and B for real events. Results confirm the tendency suggested by Crook's analysis. On the other hand, Crook's hypothesis of low level moisture as the only parameter that differentiates between type A and B can be applied only if the events develop in the same meteorological conditions. Crook's tests also helped to asses how the the meteorological parameters contribute to Hector development in terms of percentage.

scholarly journals Seeking key meteorological parameters to better understand Hector

2016 ◽  
Vol 16 (2) ◽  
pp. 431-447
Author(s):  
S. Gentile ◽  
R. Ferretti
Keyword(s):  
Potential Energy ◽  
Vertical Velocity ◽  
Meteorological Parameters ◽  
Mesoscale Model ◽  
Initial Conditions ◽  
Convective Available Potential Energy ◽  
Surface Wind ◽  
Type A ◽  
Low Level ◽  
Available Potential Energy

Abstract. Twelve Hector events, a storm which develops in northern Australia, are analyzed with the aim of identifying the main meteorological parameters involved in the storm's convective development. Based on Crook's ideal study (Crook, 2001), wind speed and direction, wind shear, water vapor, convective available potential energy and type of convection are the parameters used for this analysis. Both the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis and high-resolution simulations from the Fifth-Generation Mesoscale Model (MM5) are used. The MM5 simulations are used to connect the mean vertical velocity to the total condensate at the maximum stage and to study the dynamics of the storms. The ECMWF analyses are used to evaluate the initial conditions and the environmental fields contributing to Hector's development. The analysis suggests that the strength of convection, defined in terms of vertical velocity, largely contributes to the vertical distribution of hydrometeors. The role of total condensate and mean lifting versus low-level moisture, convective available potential energy, surface wind and direction is analyzed for shear and no-shear conditions to evaluate the differences between type A and B for real events. Results confirm the tendency suggested by Crook's analysis. However, Crook's hypothesis of low-level moisture as the only parameter that differentiates between type A and B can only be applied if the events develop in the same meteorological conditions. Crook's tests also helped to assess how the meteorological parameters contribute to Hector's development in terms of percentage.

scholarly journals Analysis of the convective available potential energy by precipitation over Iraq using ECMWF data for the period of 1989–2018

2020 ◽  
Vol 29 (2) ◽  
pp. 196-211
Author(s):  
Osama Al-Taai ◽  
Zainab Abbood
Keyword(s):  
Potential Energy ◽  
Convective Available Potential Energy ◽  
Weather Conditions ◽  
Convective Precipitation ◽  
Total Precipitation ◽  
Weather Forecasts ◽  
Available Potential Energy ◽  
Medium Range ◽  
The Relationship ◽  
Very High

The Convective Available Potential Energy (CAPE) represents the amount of energy for a sample of air. The sample departs vertically within the atmosphere and through these values the potential energy to predict the extreme weather conditions such as storms, hurricanes, lightning and thunder. Data are taken by CAPE, convective precipitation (Cp) and total precipitation (Tp) from satellites recorded by the European Centre for Medium-Range Weather Forecasts (ECMWF). The choice of 30 years (1989– –2018) over Iraq station between two latitudes (29.5°–37.22° N) and two longitudes (48.45°–38.45° E). Otherwise, we have studied total yearly mean of CAPE, Cp and Tp over Iraq, the total monthly mean of CAPE, Cp and Tp for the selected station, as well as the relationship between of CAPE, Cp and Tp for the selected station. The results showed that the highest total yearly mean of CAPE, Cp and Tp over Iraq was included northern stations and lowest was included central and southern stations. The highest total monthly mean of CAPE, Cp and Tp for Zakho station. The relationship between the CAPE and Cp is positive and the relationship between CAPE and Tp is positive too at five stations but Mosul station represents very high correlation while Zakho station represents the low correlation.

The Effect of Topographic Variability on Initial Condition Sensitivity of Low-Level Wind Forecasts. Part I: Experiments Using Idealized Terrain

2013 ◽  
Vol 141 (7) ◽  
pp. 2137-2155 ◽  
Author(s):  
Paul E. Bieringer ◽  
Peter S. Ray ◽  
Andrew J. Annunzio
Keyword(s):  
Mesoscale Model ◽  
Initial Conditions ◽  
Surface Wind ◽  
Observation System ◽  
Initial Condition ◽  
State University ◽  
Weather Forecasts ◽  
The Difference ◽  
Meteorological Observations ◽  
Targeted Observation

Abstract The concept of improving the accuracy of numerical weather forecasts by targeting additional meteorological observations in areas where the initial condition error is suspected to grow rapidly has been the topic of numerous studies and field programs. The challenge faced by this approach is that it typically requires a costly observation system that can be quickly adapted to place instrumentation where needed. The present study examines whether the underlying terrain in a mesoscale model influences model initial condition sensitivity and if knowledge of the terrain and corresponding predominant flow patterns for a region can be used to direct the placement of instrumentation. This follows the same concept on which earlier targeted observation approaches were based, but eliminates the need for an observation system that needs to be continually reconfigured. Simulations from the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) and its adjoint are used to characterize the locations, variables, and magnitudes of initial condition perturbations that have the most significant impact on the surface wind forecast. This study examines a relatively simple case where an idealized mountain surrounded by a flat plain is located upwind of the forecast verification region. The results suggest that, when elevated terrain is present upstream of the target forecast area, the largest forecast impact (defined as the difference between the simulation with perturbed initial conditions and a control simulation where the initial condition was not perturbed) occurs when the initial analysis perturbations are made in regions with complex terrain.

An Unusual Hailstorm on 24 June 2006 in Boulder, Colorado. Part I: Mesoscale Setting and Radar Features

2008 ◽  
Vol 136 (8) ◽  
pp. 2813-2832 ◽  
Author(s):  
Paul T. Schlatter ◽  
Thomas W. Schlatter ◽  
Charles A. Knight
Keyword(s):  
Boundary Layer ◽  
Potential Energy ◽  
Convective Available Potential Energy ◽  
Meteorological Conditions ◽  
Vertical Shear ◽  
Low Density ◽  
The South ◽  
Low Level ◽  
Available Potential Energy

Abstract An unusual, isolated hailstorm descended on Boulder, Colorado, on the evening of 24 June 2006. Starting with scattered large, flattened, disk-shaped hailstones and ending with a deluge of slushy hail that was over 4 cm deep on the ground, the storm lasted no more than 20 min and did surprisingly little damage except to vegetation. Part I of this two-part paper examines the meteorological conditions preceding the storm and the signatures it exhibited on Weather Surveillance Radar-1988 Doppler (WSR-88D) displays. There was no obvious upper-tropospheric forcing for this storm, vertical shear of the low-level wind was minimal, the boundary layer air feeding the storm was not very moist (maximum dewpoint 8.5°C), and convective available potential energy calculated from a modified air parcel was at most 1550 J kg−1. Despite these handicaps, the hail-producing storm had low-level reflectivity exceeding 70 dBZ, produced copious low-density hail, exhibited strong rotation, and generated three extensive bounded weak-echo regions (BWERs) in succession. The earliest of these filled with high reflectivities as the second one to the south poked up through precipitation-filled air. This has implications for low-density hail growth, as discussed in Part II.

Changes in Convective Available Potential Energy and Convective Inhibition under Global Warming

2020 ◽  
Vol 33 (6) ◽  
pp. 2025-2050 ◽  
Author(s):  
Jiao Chen ◽  
Aiguo Dai ◽  
Yaocun Zhang ◽  
Kristen L. Rasmussen
Keyword(s):  
Global Warming ◽  
Potential Energy ◽  
Climate Model ◽  
Convective Available Potential Energy ◽  
The United States ◽  
Specific Humidity ◽  
Low Level ◽  
Available Potential Energy ◽  
Convective Inhibition ◽  
The Impact

AbstractAtmospheric convective available potential energy (CAPE) is expected to increase under greenhouse gas–induced global warming, but a recent regional study also suggests enhanced convective inhibition (CIN) over land although its cause is not well understood. In this study, a global climate model is first evaluated by comparing its CAPE and CIN with reanalysis data, and then their future changes and the underlying causes are examined. The climate model reasonably captures the present-day CAPE and CIN patterns seen in the reanalysis, and projects increased CAPE almost everywhere and stronger CIN over most land under global warming. Over land, the cases or times with medium to strong CAPE or CIN would increase while cases with weak CAPE or CIN would decrease, leading to an overall strengthening in their mean values. These projected changes are confirmed by convection-permitting 4-km model simulations over the United States. The CAPE increase results mainly from increased low-level specific humidity, which leads to more latent heating and buoyancy for a lifted parcel above the level of free convection (LFC) and also a higher level of neutral buoyancy. The enhanced CIN over most land results mainly from reduced low-level relative humidity (RH), which leads to a higher lifting condensation level and a higher LFC and thus more negative buoyancy. Over tropical oceans, the near-surface RH increases slightly, leading to slight weakening of CIN. Over the subtropical eastern Pacific and Atlantic Ocean, the impact of reduced low-level atmospheric lapse rates overshadows the effect of increased specific humidity, leading to decreased CAPE.

scholarly journals Evaluating the Effective Inflow Layer of Simulated Supercell Updrafts

2020 ◽  
Vol 148 (8) ◽  
pp. 3507-3532 ◽  
Author(s):  
Christopher J. Nowotarski ◽  
John M. Peters ◽  
Jake P. Mulholland
Keyword(s):  
Potential Energy ◽  
Deep Layer ◽  
Dynamic Pressure ◽  
Convective Available Potential Energy ◽  
Severe Weather ◽  
Convective Storms ◽  
Low Level ◽  
Available Potential Energy ◽  
Supercell Thunderstorms ◽  
Relative Flow

Abstract Proper prediction of the inflow layer of deep convective storms is critical for understanding their potential updraft properties and likelihood of producing severe weather. In this study, an existing forecast metric known as the effective inflow layer (EIL) is evaluated with an emphasis on its performance for supercell thunderstorms, where both buoyancy and dynamic pressure accelerations are common. A total of 15 idealized simulations with a range of realistic base states are performed. Using an array of passive fluid tracers initialized at various vertical levels, the proportion of simulated updraft core air originating from the EIL is determined. Results suggest that the EIL metric performs well in forecasting peak updraft origin height, particularly for supercell updrafts. Moreover, the EIL metric displays consistent skill across a range of updraft core definitions. The EIL has a tendency to perform better as convective available potential energy, deep-layer shear, and EIL depth are increased in the near-storm environment. Modifications to further constrain the EIL based on the most-unstable parcel height or storm-relative flow may lead to marginal improvements for the most stringent updraft core definitions. Finally, effects of the near-storm environment on low-level and peak updraft forcing and intensity are discussed.

scholarly journals Ocean Convective Available Potential Energy. Part II: Energetics of Thermobaric Convection and Thermobaric Cabbeling

2016 ◽  
Vol 46 (4) ◽  
pp. 1097-1115 ◽  
Author(s):  
Zhan Su ◽  
Andrew P. Ingersoll ◽  
Andrew L. Stewart ◽  
Andrew F. Thompson
Keyword(s):  
Potential Energy ◽  
Deep Convection ◽  
Center Of Mass ◽  
Convective Available Potential Energy ◽  
Vertical Mixing ◽  
Available Potential Energy ◽  
Energy Part ◽  
Different Temperatures ◽  
Simplifying Assumptions ◽  
Diabatic Processes

AbstractThe energetics of thermobaricity- and cabbeling-powered deep convection occurring in oceans with cold freshwater overlying warm salty water are investigated here. These quasi-two-layer profiles are widely observed in wintertime polar oceans. The key diagnostic is the ocean convective available potential energy (OCAPE), a concept introduced in a companion piece to this paper (Part I). For an isolated ocean column, OCAPE arises from thermobaricity and is the maximum potential energy (PE) that can be converted into kinetic energy (KE) under adiabatic vertical parcel rearrangements. This study explores the KE budget of convection using two-dimensional numerical simulations and analytical estimates. The authors find that OCAPE is a principal source for KE. However, the complete conversion of OCAPE to KE is inhibited by diabatic processes. Further, this study finds that diabatic processes produce three other distinct contributions to the KE budget: (i) a sink of KE due to the reduction of stratification by vertical mixing, which raises water column’s center of mass and thus acts to convert KE to PE; (ii) a source of KE due to cabbeling-induced shrinking of the water column’s volume when water masses with different temperatures are mixed, which lowers the water column’s center of mass and thus acts to convert PE into KE; and (iii) a reduced production of KE due to diabatic energy conversion of the KE convertible part of the PE to the KE inconvertible part of the PE. Under some simplifying assumptions, the authors also propose a theory to estimate the maximum depth of convection from an energetic perspective. This study provides a potential basis for improving the convection parameterization in ocean models.

scholarly journals Impact of Parameterization of Physical Processes on Simulation of Track and Intensity of Tropical Cyclone Nargis (2008) with WRF-NMM Model

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Sujata Pattanayak ◽  
U. C. Mohanty ◽  
Krishna K. Osuri
Keyword(s):  
Land Surface ◽  
Mesoscale Model ◽  
Initial Conditions ◽  
Surface Wind ◽  
India Meteorological Department ◽  
Heat Fluxes ◽  
Cumulus Convection ◽  
Cyclonic Storm ◽  
Parameterization Schemes ◽  
Cyclone Nargis

The present study is carried out to investigate the performance of different cumulus convection, planetary boundary layer, land surface processes, and microphysics parameterization schemes in the simulation of a very severe cyclonic storm (VSCS) Nargis (2008), developed in the central Bay of Bengal on 27 April 2008. For this purpose, the nonhydrostatic mesoscale model (NMM) dynamic core of weather research and forecasting (WRF) system is used. Model-simulated track positions and intensity in terms of minimum central mean sea level pressure (MSLP), maximum surface wind (10 m), and precipitation are verified with observations as provided by the India Meteorological Department (IMD) and Tropical Rainfall Measurement Mission (TRMM). The estimated optimum combination is reinvestigated with six different initial conditions of the same case to have better conclusion on the performance of WRF-NMM. A few more diagnostic fields like vertical velocity, vorticity, and heat fluxes are also evaluated. The results indicate that cumulus convection play an important role in the movement of the cyclone, and PBL has a crucial role in the intensification of the storm. The combination of Simplified Arakawa Schubert (SAS) convection, Yonsei University (YSU) PBL, NMM land surface, and Ferrier microphysics parameterization schemes in WRF-NMM give better track and intensity forecast with minimum vector displacement error.

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