Balanced Response of an Axisymmetric Tropical Cyclone to Periodic Diurnal Heating

2017 ◽  
Vol 74 (10) ◽  
pp. 3325-3337 ◽  
Author(s):  
Erika L. Navarro ◽  
Gregory J. Hakim ◽  
Hugh E. Willoughby
Keyword(s):  
Diurnal Cycle ◽  
Lower Troposphere ◽  
Radiative Heating ◽  
Wind Fields ◽  
Periodic Heating ◽  
Dynamical Mechanism ◽  
Axisymmetric Solution ◽  
Upper Level ◽  
Comparison Of The Results ◽  
The Impact

Abstract A modified version of the Sawyer–Eliassen equation is applied to determine the impact of periodic diurnal heating on a balanced vortex. The TC diurnal cycle is a coherent signal that arises in the cirrus canopy. However, despite thorough documentation in the literature, the dynamical mechanism remains unknown. Recent work demonstrates that periodic radiative heating in the TC outflow layer is linked with an anomalous upper-level circulation; this heating is also associated with a cycle of latent heating in the lower troposphere that corresponds to a cycle in storm intensity. Using a method that is analogous to the Sawyer–Eliassen equation, but for solutions having the same time scale as time-periodic forcing, these distributions are analyzed to determine the effect of periodic diurnal heating on an axisymmetric vortex. Results for periodic heating in the lower troposphere show an overturning circulation that resembles the Sawyer–Eliassen solution. The model simulates positive perturbations in the azimuthal wind field of 2.5 m s−1 near the radius of maximum wind. Periodic heating near the top of the vortex produces a local overturning response in the region of heating and an inertia–buoyancy wave response in the storm environment. Comparison of the results from the modified Sawyer–Eliassen equation to those of an idealized axisymmetric solution for both heating distributions shows similarities in the structure of the perturbation wind fields, suggesting that the axisymmetric TC diurnal cycle is primarily a balanced response driven by periodic heating.

The impact of diurnal precipitation over Sumatra Island, Indonesia, on synoptic disturbances and its relation to the Madden-Julian Oscillation

2021 ◽  
Author(s):  
Ayako Seiki ◽  
Satoru Yokoi ◽  
Masaki Katsumata
Keyword(s):  
Indian Ocean ◽  
Diurnal Cycle ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Eastern Indian Ocean ◽  
Sumatra Island ◽  
The Indian Ocean ◽  
Precipitation Area ◽  
High Precipitation ◽  
The Impact

<p>The impact of diurnal precipitation over Sumatra Island, the Indonesian Maritime Continent (MC), on synoptic disturbances over the eastern Indian Ocean is examined using high-resolution rainfall data from the Global Satellite Mapping of Precipitation project and the Japanese 55-year Reanalysis data during the rainy season from September to April for the period 2000–2014. When the diurnal cycle is strong, the high precipitation area observed over Sumatra in the afternoon migrates offshore during nighttime and reaches 500 km off the coast on average. The strong diurnal events are followed by the development of synoptic disturbances over the eastern Indian Ocean for several days, and apparent twin synoptic disturbances straddling the equator develop only when the convective center of the Madden–Julian Oscillation (MJO) lies over the Indian Ocean (MJO-IO). Without the MJO, the synoptic disturbances develop mainly south of the equator. The differences in the locations and behaviors of active synoptic disturbances are related to the strength of mean horizontal winds in the lower troposphere. During the MJO-IO, the intensification of mean northeasterly winds in the northern hemisphere blowing into the organized MJO convection in addition to mean southeasterly winds in the southern hemisphere facilitate the formation of the twin disturbances. These results suggest that seed disturbances arising from the diurnal offshore migration of precipitation from Sumatra develop differently depending on the mean states over the eastern Indian Ocean. Furthermore, it is shown that the MJO events with the strong diurnal cycle tend to have longer duration and continuing eastward propagation of active convection across the MC, whereas the convective activities of the other MJO events weaken considerably over the MC and develop again over the western Pacific. These results suggest that the strong diurnal cycle over Sumatra facilitates the smooth eastward propagation of the intraseasonal convection across the MC.</p>

scholarly journals Targeting Studies for the Extratropical Transition of Hurricane Fabian: Signal Propagation, the Interaction between Fabian and Midlatitude Flow, and an Observation Strategy

2010 ◽  
Vol 138 (8) ◽  
pp. 3224-3242 ◽  
Author(s):  
Hua Chen ◽  
Weiyu Pan
Keyword(s):  
Potential Vorticity ◽  
Lower Troposphere ◽  
Signal Propagation ◽  
Synoptic Situation ◽  
Energy Dispersion ◽  
Extratropical Transition ◽  
Initial Errors ◽  
Targeted Observations ◽  
Upper Level ◽  
The Impact

Abstract This study examines how the impact of targeted observations propagates during the extratropical transition (ET) of Hurricane Fabian. Signal (i.e., the forecast difference between denial experiments and the control experiment) propagation can reveal the interaction between the tropical cyclone (TC) and the midlatitude jet, and the energy dispersion or propagation of the TC undergoing ET also can be determined. The crucial role of an upper-level trough is discussed. Based on this study, a strategy issue regarding targeted observations of ET and several typical problems regarding the numerical prediction of ET are discussed. The results show that the greatest signals along with their propagation are associated closely with various types of instabilities. In general, the signal first appears at the location of the TC, and then it propagates to the midlatitude jet through the interaction between the TC and the jet itself. Thereafter, signals propagate downstream along the jet and downward to the lower troposphere at the same time by way of Rossby wave packets; the jet essentially acts as a waveguide. Through the signal propagation and development in the jet, the impact of targeted observations seems sensitive to the ET process. The interaction between the TC and the jet occurs as high θ (low potential vorticity) air flows out of the TC toward the northeast and into the jet below the tropopause. The interaction may be strengthened by an upstream trough at upper levels. The TC outflow enhances the potential vorticity (PV) gradient and baroclinity in the jet. Therefore, the jet becomes stronger and more baroclinically unstable. The signal propagation also indicates the energy dispersion of a TC undergoing ET. The strong southwesterly flow ahead of the upper-level trough steers Fabian to higher latitudes, and strengthens the advection process of low PV air into the jet. Therefore, the development of the upper-level trough and its proximity to the TC are crucial for the interaction between the TC and the jet, and the resulting signal propagation. Small deviations from this synoptic situation may result in great differences in the signal propagation and the ET forecast. The most suitable region for targeting is likely a region where crucial synoptic processes can magnify initial errors.

scholarly journals Impact of multiple-scale circulation interactions on the spring diurnal precipitation over Luzon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cheng-An Lee ◽  
Wan-Ru Huang ◽  
Ya-Hui Chang ◽  
Shih-Ming Huang
Keyword(s):  
Large Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Sea Breeze ◽  
Multiple Scale ◽  
Wind Fields ◽  
Easterly Wind ◽  
Upper Level ◽  
Global Precipitation ◽  
The Impact ◽  
Circulation Changes

AbstractThis study examines the spatiotemporal characteristics of diurnal precipitation over Luzon and the nearby oceans in boreal spring. The study focuses on exploring the impact of the interaction between large- and local-scale circulation changes on the modulation of diurnal precipitation. We analyze the satellite precipitation data obtained from the Tropical Rainfall Measuring Mission and Global Precipitation Measurement Mission during the spring (March–May) of 2001–2019. The results show that the spring diurnal precipitation over Luzon and the nearby oceans consists of a clear eastward propagation signal. The direction of this propagation is opposite to that of the prevailing low-level easterly wind in spring and differs from the well-known westward propagation direction of diurnal precipitation over Luzon in summer. Diagnoses of the possible maintenance mechanisms suggest that the eastward propagation diurnal precipitation can be attributed to the interaction between the topography and multiple-scale circulation changes, including the mountain–valley breeze, island-scale land–sea breeze (LSB), large-scale LSB-like circulation, and mid-to-upper-level prevailing wind fields. This finding highlights the importance of considering multiple-scale circulation changes in the modulation of spring diurnal precipitation over the East Asia–western North Pacific region.

scholarly journals Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

2004 ◽  
Vol 22 (5) ◽  
pp. 1421-1434 ◽  
Author(s):  
A. Chakraborty ◽  
S. K. Satheesh ◽  
R. S. Nanjundiah ◽  
J. Srinivasan
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Monsoon Season ◽  
Lower Troposphere ◽  
Circulation Model ◽  
Indian Region ◽  
Radiative Heating ◽  
Aerosol Forcing ◽  
Absorbing Aerosols ◽  
The Impact

Abstract. The impact of anthropogenic absorbing aerosols (such as soot) on the climate over the Indian region has been studied using the NCMRWF general circulation model. The absorbing aerosols increase shortwave radiative heating of the lower troposphere and reduce the heating at the surface. These effects have been incorporated as heating of the lower troposphere (up to 700hPa) and cooling over the continental surface based on INDOEX measurements. The heating effect is constant in the pre-monsoon season and reduces to zero during the monsoon season. It is shown that even in the monsoon season when the aerosol forcing is zero, there is an overall increase in rainfall and a reduction in surface temperature over the Indian region. The rainfall averaged over the Tropics shows a small reduction in most of the months during the January to September period. The impact of aerosol forcing, the model's sensitivity to this forcing and its interaction with model-physics has been studied by changing the cumulus parameterization from the Simplified Arakawa-Schubert (SAS) scheme to the Kuo scheme. During the pre-monsoon season the major changes in precipitation occur in the oceanic Inter Tropical Convergence Zone (ITCZ), where both the schemes show an increase in precipitation. This result is similar to that reported in Chung2002. On the other hand, during the monsoon season the changes in precipitation in the continental region are different in the SAS and Kuo schemes. It is shown that the heating due to absorbing aerosols changes the vertical moist-static stability of the atmosphere. The difference in the precipitation changes in the two cumulus schemes is on account of the different responses in the two parameterization schemes to changes in vertical stability. Key words. Atmospheric composition and structure (aerosols and particles) – Meteorology and atmospheric dynamics (tropical meteorology; precipitation)

The Impact of Ice Phase Cloud Parameterizations on Tropical Cyclone Prediction

2014 ◽  
Vol 142 (2) ◽  
pp. 606-625 ◽  
Author(s):  
Yi Jin ◽  
Shouping Wang ◽  
Jason Nachamkin ◽  
James D. Doyle ◽  
Gregory Thompson ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Satellite Imagery ◽  
Hybrid Approach ◽  
Radiative Heating ◽  
Basin Scale ◽  
Single Moment ◽  
Upper Level ◽  
Cloud Ice ◽  
The Impact ◽  
Ice Phase

Abstract The impact of ice phase cloud microphysical processes on prediction of tropical cyclone environment is examined for two microphysical parameterizations using the Coupled Ocean–Atmosphere Mesoscale Prediction System–Tropical Cyclone (COAMPS-TC) model. An older version of microphysical parameterization is a relatively typical single-moment scheme with five hydrometeor species: cloud water and ice, rain, snow, and graupel. An alternative newer method uses a hybrid approach of double moment in cloud ice and rain and single moment in the other three species. Basin-scale synoptic flow simulations point to important differences between these two schemes. The upper-level cloud ice concentrations produced by the older scheme are up to two orders of magnitude greater than the newer scheme, primarily due to differing assumptions concerning the ice nucleation parameterization. Significant (1°–2°C) warm biases near the 300-hPa level in the control experiments are not present using the newer scheme. The warm bias in the control simulations is associated with the longwave radiative heating near the base of the cloud ice layer. The two schemes produced different track and intensity forecasts for 15 Atlantic storms. Rightward cross-track bias and positive intensity bias in the control forecasts are significantly reduced using the newer scheme. Synthetic satellite imagery of Hurricane Igor (2010) shows more realistic brightness temperatures from the simulations using the newer scheme, in which the inner core structure is clearly discernible. Applying the synthetic satellite imagery in both quantitative and qualitative analyses helped to pinpoint the issue of excessive upper-level cloud ice in the older scheme.

scholarly journals Interannual Variability and Trends in Sea Surface Temperature, Lower and Middle Atmosphere Temperature at Different Latitudes for 1980–2019

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 454
Author(s):  
Andrew R. Jakovlev ◽  
Sergei P. Smyshlyaev ◽  
Vener Y. Galin
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Lower Stratosphere ◽  
Middle Atmosphere ◽  
Southern Oscillation ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Sea Surface ◽  
The Arctic ◽  
The Impact

The influence of sea-surface temperature (SST) on the lower troposphere and lower stratosphere temperature in the tropical, middle, and polar latitudes is studied for 1980–2019 based on the MERRA2, ERA5, and Met Office reanalysis data, and numerical modeling with a chemistry-climate model (CCM) of the lower and middle atmosphere. The variability of SST is analyzed according to Met Office and ERA5 data, while the variability of atmospheric temperature is investigated according to MERRA2 and ERA5 data. Analysis of sea surface temperature trends based on reanalysis data revealed that a significant positive SST trend of about 0.1 degrees per decade is observed over the globe. In the middle latitudes of the Northern Hemisphere, the trend (about 0.2 degrees per decade) is 2 times higher than the global average, and 5 times higher than in the Southern Hemisphere (about 0.04 degrees per decade). At polar latitudes, opposite SST trends are observed in the Arctic (positive) and Antarctic (negative). The impact of the El Niño Southern Oscillation phenomenon on the temperature of the lower and middle atmosphere in the middle and polar latitudes of the Northern and Southern Hemispheres is discussed. To assess the relative influence of SST, CO2, and other greenhouse gases’ variability on the temperature of the lower troposphere and lower stratosphere, numerical calculations with a CCM were performed for several scenarios of accounting for the SST and carbon dioxide variability. The results of numerical experiments with a CCM demonstrated that the influence of SST prevails in the troposphere, while for the stratosphere, an increase in the CO2 content plays the most important role.

scholarly journals Optimal profile for concave slopes under static and seismic conditions

2016 ◽  
Vol 53 (9) ◽  
pp. 1522-1532 ◽  
Author(s):  
Farshid Vahedifard ◽  
Shahriar Shahrokhabadi ◽  
Dov Leshchinsky
Keyword(s):  
Limit Equilibrium ◽  
Stable Configuration ◽  
Preliminary Evaluation ◽  
Construction Technology ◽  
Stability Of Slopes ◽  
Optimal Profile ◽  
Stabilized Soil ◽  
The Stability ◽  
Comparison Of The Results ◽  
The Impact

This study presents a methodology to determine the stability and optimal profile for slopes with concave cross section under static and seismic conditions. Concave profiles are observed in some natural slopes suggesting that such geometry is a more stable configuration. In this study, the profile of a concave slope was idealized by a circular arc defined by a single variable, the mid-chord offset (MCO). The proposed concave profile formulation was incorporated into a limit equilibrium–based log spiral slope stability method. Stability charts are presented to show the stability number, MCO, and mode of failure for homogeneous slopes corresponding to the most stable configuration under static and pseudostatic conditions. It is shown that concave profiles can significantly improve the stability of slopes. Under seismic conditions, the impact of concavity is most pronounced. Good agreement was demonstrated upon comparison of the results from the proposed method against those attended from a rigorous upper bound limit analysis. The proposed methodology, along with recent advances in construction technology, can be employed to use concave profiles in trenches, open mine excavations, earth retaining systems, and naturally cemented and stabilized soil slopes. The results presented provide a useful tool for preliminary evaluation for adopting such concave profiles in practice.

scholarly journals Dynamical Processes Related to the Appearance of the Okhotsk High during Early Midsummer

2007 ◽  
Vol 20 (19) ◽  
pp. 4982-4994 ◽  
Author(s):  
Naoki Sato ◽  
Masaaki Takahashi
Keyword(s):  
Energy Conversion ◽  
Heat Budget ◽  
Lower Troposphere ◽  
Positive Pressure ◽  
Basic Field ◽  
Anomaly Field ◽  
Anomaly Pattern ◽  
Pressure Anomaly ◽  
Okhotsk High ◽  
Upper Level

Abstract The authors identified an upper-level pressure anomaly pattern corresponding to the interannual variability of the Okhotsk high in midsummer (late July and early August) as a predominant anomaly pattern in the Northern Hemisphere, by using objectively analyzed data. According to the results of empirical orthogonal function (EOF) analyses and composite analyses, a positive pressure anomaly appeared near the tropopause over eastern Siberia in years with strong Okhotsk highs. Examination of the heat budget in the lower troposphere revealed that a negative surface temperature anomaly observed in northern Japan was brought by the advection of the climatological temperature gradient from the anomalous wind associated with the upper-level anticyclonic anomaly. It was also demonstrated that the anomaly field over Siberia does not accompany predominant vorticity forcing or Rossby wave propagation from the west with a specific phase. However, positive kinetic energy conversion from the climatological basic field to the anomaly field is estimated. The energy conversion contributes to maintaining the anomaly pattern. By the numerical experiments using a linear barotropic model, it is suggested that the upper-level anomaly pattern related to the anomalous Okhotsk high appears through the interaction with the climatological basic field, even though the external forcings are homogeneously distributed.

Deceleration of sliding motorcycles (mainly scooters) in accident reconstructions

2017 ◽  
Vol 232 (7) ◽  
pp. 866-876 ◽  
Author(s):  
Carlo Cialdai ◽  
Dario Vangi ◽  
Antonio Virga
Keyword(s):  
Urban Areas ◽  
Test Session ◽  
Road Accidents ◽  
Factors Affecting ◽  
Different Types ◽  
Energy Dissipated ◽  
Comparison Of The Results ◽  
Two Wheeler ◽  
The Impact ◽  
Good Agreement

This paper presents an analysis of the situation in which a two-wheeler (i.e. a motorcycle, where the term motorcycles includes scooters) falls over to the side and then successively slides; this typically occurs in road accidents involving this type of vehicle. Knowing the deceleration rate of the sliding phase allows the kinetic energy dissipated and the speed of the motorcycle just before the fall to the ground to be calculated. These parameters are very important in the analysis and reconstruction of accidents. The work presented in this paper was developed in two experimental test sessions on fully faired motorcycles which are mainly of the scooter type and widely used in urban areas. In the first session, sliding tests were carried out, with the speed in the range 10–50 km/h, on three different types of road surface. Analysis of the evidence allowed the dissipative main phases of motion of the motorcycle (the impact with the ground, the rebounds and the stabilized swiping) to be identified and some factors affecting the phenomenon to be studied. The coefficient of average deceleration was calculated using two typical equations. The second test session consisted of drag tests. In these tests, the motorcycle, which had previously laid on its side, was dragged for a few metres at a constant speed of about 20 km/h, while the drag force was measured. A comparison of the results obtained in these tests with those obtained in the sliding tests yielded very good agreement in the coefficients of deceleration.

scholarly journals Gaseous chemistry and aerosol mechanism developments for version 3.5.1 of the online regional model, WRF-Chem

2014 ◽  
Vol 7 (6) ◽  
pp. 2557-2579 ◽  
Author(s):  
S. Archer-Nicholls ◽  
D. Lowe ◽  
S. Utembe ◽  
J. Allan ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Reduced Form ◽  
Sea Spray ◽  
Wind Fields ◽  
Aerosol Composition ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
The Impact ◽  
Phase Chemical

Abstract. We have made a number of developments to the Weather, Research and Forecasting model coupled with Chemistry (WRF-Chem), with the aim of improving model prediction of trace atmospheric gas-phase chemical and aerosol composition, and of interactions between air quality and weather. A reduced form of the Common Reactive Intermediates gas-phase chemical mechanism (CRIv2-R5) has been added, using the Kinetic Pre-Processor (KPP) interface, to enable more explicit simulation of VOC degradation. N2O5 heterogeneous chemistry has been added to the existing sectional MOSAIC aerosol module, and coupled to both the CRIv2-R5 and existing CBM-Z gas-phase schemes. Modifications have also been made to the sea-spray aerosol emission representation, allowing the inclusion of primary organic material in sea-spray aerosol. We have worked on the European domain, with a particular focus on making the model suitable for the study of nighttime chemistry and oxidation by the nitrate radical in the UK atmosphere. Driven by appropriate emissions, wind fields and chemical boundary conditions, implementation of the different developments are illustrated, using a modified version of WRF-Chem 3.4.1, in order to demonstrate the impact that these changes have in the Northwest European domain. These developments are publicly available in WRF-Chem from version 3.5.1 onwards.

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