scholarly journals On the Development of Above-Anvil Cirrus Plumes in Extratropical Convection

2017 ◽  
Vol 74 (5) ◽  
pp. 1617-1633 ◽  
Author(s):  
Cameron R. Homeyer ◽  
Joel D. McAuliffe ◽  
Kristopher M. Bedka
Keyword(s):  
Gravity Wave ◽  
Wave Breaking ◽  
Lower Stratosphere ◽  
Atmospheric Conditions ◽  
Upper Troposphere ◽  
Using Data ◽  
The Stability ◽  
Anvil Cirrus ◽  
Cloud Material ◽  
Relative Wind

Abstract Expansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft-based imagery for several decades. Despite knowledge of their occurrence, the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known. Here, the formation of these cirrus “plumes” is examined using a combination of satellite imagery, four-dimensional ground-based radar observations, assimilated atmospheric states from a state-of-the-art reanalysis, and idealized numerical simulations with explicitly resolved convection. Using data from 20 recent events (2013–present), it is found that convective cores of storms with above-anvil cirrus plumes reach altitudes 1–6 km above the tropopause. Thus, it is likely that these clouds represent the injection of cloud material into the lower stratosphere. Comparison of storms with above-anvil cirrus plumes and observed tropopause-penetrating convection without plumes reveals an association with large vector differences between the motion of a storm and the environmental wind in the upper troposphere and lower stratosphere (UTLS), suggesting that gravity wave breaking and/or stretching of the tropopause-penetrating cloud are/is more prevalent in plume-producing storms. A weak relationship is found between plume occurrence and the stability of the lower stratosphere (or tropopause structure), and no relationship is found with the duration of stratospheric penetration or stratospheric humidity. Idealized model simulations of tropopause-penetrating convection with small and large magnitudes of storm-relative wind in the UTLS are found to reproduce the observationally established storm-relative wind relationship and show that frequent gravity wave breaking is the primary mechanism responsible for plume formation.

Internal gravity wave selection in the upper troposphere and lower stratosphere observed by the MU radar: Preliminary results

1989 ◽  
Vol 130 (2-3) ◽  
pp. 481-495 ◽  
Author(s):  
Manabu D. Yamanaka ◽  
Shoichiro Fukao ◽  
Hiromasa Matsumoto ◽  
Toru Sato ◽  
Toshitaka Tsuda ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Internal Gravity Wave ◽  
Upper Troposphere ◽  
Preliminary Results ◽  
Mu Radar

scholarly journals Determining the Best Method for Estimating the Observed Level of Maximum Detrainment Based on Radar Reflectivity

2016 ◽  
Vol 144 (8) ◽  
pp. 2915-2926 ◽  
Author(s):  
Nicholas D. Carletta ◽  
Gretchen L. Mullendore ◽  
Mariusz Starzec ◽  
Baike Xi ◽  
Zhe Feng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mass Transport ◽  
Lower Stratosphere ◽  
Radar Reflectivity ◽  
Radiative Properties ◽  
Cloud Formation ◽  
Upper Troposphere ◽  
Using Data ◽  
Mass Divergence

Abstract Convective mass transport is the transport of mass from near the surface up to the upper troposphere and lower stratosphere (UTLS) by a deep convective updraft. This transport can alter the chemical makeup and water vapor balance of the UTLS, which affects cloud formation and the radiative properties of the atmosphere. It is, therefore, important to understand the exact altitudes at which mass is detrained from convection. The purpose of this study was to improve upon previously published methodologies for estimating the level of maximum detrainment (LMD) within convection using data from a single ground-based radar. Four methods were used to identify the LMD and validated against dual-Doppler-derived vertical mass divergence fields for six cases with a variety of storm types. The best method for locating the LMD was determined to be the method that used a reflectivity texture technique to determine convective cores and a multilayer echo identification to determine anvil locations. Although an improvement over previously published methods, the new methodology still produced unreliable results in certain regimes. The methodology worked best when applied to mature updrafts, as the anvil needs time to grow to a detectable size. Thus, radar reflectivity is found to be valuable in estimating the LMD, but storm maturity must also be considered for best results.

Internal Gravity Wave Selection in the Upper Troposphere and Lower Stratosphere Observed by the MU Radar: Preliminary Results

1989 ◽  
pp. 481-495 ◽  
Author(s):  
Manabu D. Yamanaka ◽  
Shoichiro Fukao ◽  
Hiromasa Matsumoto ◽  
Toru Sato ◽  
Toshitaka Tsuda ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Internal Gravity Wave ◽  
Upper Troposphere ◽  
Preliminary Results ◽  
Mu Radar

scholarly journals High-Resolution Radio Acoustic Sounding System Observations and Analysis up to 20 km

2008 ◽  
Vol 25 (8) ◽  
pp. 1383-1396 ◽  
Author(s):  
Simon P. Alexander ◽  
Toshitaka Tsuda
Keyword(s):  
High Frequency ◽  
Lower Stratosphere ◽  
Energy Dissipation Rate ◽  
Energy Propagation ◽  
Acoustic Sounding ◽  
Upper Troposphere ◽  
Solar Tide ◽  
Frequency Changes ◽  
The Stability ◽  
Virtual Temperature

Abstract The first campaign-based measurements of virtual temperature in the upper-troposphere and lower-stratosphere (UTLS) region were made with the middle- and upper-atmosphere (MU) radar radio acoustic sounding system (RASS) during 4 days in August 1995. This dataset was examined in order to study high-frequency changes in the stability below 20 km, but especially in the UTLS region. Calculations of the WMO tropopause and cold-point tropopause heights showed the latter to be (1.0 ± 0.6) km higher, where 0.6 km is the standard deviation. A diurnal cycle of temperature and wind dominated the spectra, which was identified as the diurnal solar tide. Its phase maximum occurred in the afternoon between 5 and 15 km and showed upward energy propagation above this height. Changes in the UTLS kinetic energy dissipation rate ε showed significant high-frequency fluctuations embedded within layers that persisted for at least 1 day. Relative to the WMO tropopause height, the median ε increased from (0.5 ± 0.1) × 10−3 m2 s−3 in the upper troposphere to (0.7 ± 0.1) × 10−3 m2 s−3 in the lower stratosphere.

Investigating the Effect of Tropical Cyclones on Atmospheric Chemistry in the Upper Troposphere

2021 ◽  
Author(s):  
Lakhima Chutia ◽  
Pradip Bhuyan ◽  
Binita Pathak ◽  
Chandrakala Bharali
Keyword(s):  
Tropical Cyclones ◽  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Dominant Role ◽  
Air Masses ◽  
Upper Troposphere ◽  
Before And After ◽  
The Stability ◽  
Environmental Prediction ◽  
High Phase

<p>Tropical cyclones (TCs) containing widespread and intense convection, play a dominant role in stratosphere-troposphere exchange (STE) processes in the upper troposphere and lower stratosphere (UTLS) region. Here we examine the variation of meteorological and chemical fields associated with two different pre-monsoon tropical cyclones: MORA and FANI, by combining satellite-based observations from AIRS (The Atmospheric Infrared Sounder ) and different model reanalysis datasets from ERA5 (fifth generation of ECMWF atmospheric reanalyses), CAMS (Copernicus Atmosphere Monitoring Service), MERRA-2 (The Modern-Era Retrospective analysis for Research and Applications, Version 2), and NCEP (National Centers for Environmental Prediction). An increase in the upper-tropospheric ozone (O<sub>3</sub>) by 15– 30 ppbv is observed over the Bay of Bengal during the high phase of MORA cyclone. Intrusion of O<sub>3</sub> from lower stratosphere to upper troposphere is clearly observed from 50 to 300 hPa during the cyclonic period, contributing enhancement in the upper tropospheric O<sub>3</sub>. There are no such indication of enhanced O<sub>3</sub> values before and after the dissipation of MORA cyclone. General behavior of intrusion associated with severe MORA cyclone is well captured by all the models and satellite, however some differences are seen in the intensity and structure of the STE events. Strong updrafts and downdrafts present in the vicinity of tropopause during TC passage weakened the stability of tropopause layer. The low tropopause temperature with enhanced potential vorticity (PV) feature extended vertically downward from lower stratosphere to troposphere confirms the stratosphere to tropospheric intrusion during the cyclonic period. Concurrently, low relative humidity (RH) along with negative RH-O<sub>3</sub> correlation during the overhead cyclone further supports the intrusion. Contrarily, satellite and model results revealed no significant variation in O<sub>3</sub> mixing ratio in the lower stratosphere down to the tropopause level during the high phase of extremely severe FANI cyclone. Strong convective activity during the passage of FANI confirms the upward propagation of CO rich (O<sub>3</sub> poor) air masses from surface to the mid/upper troposphere. The air masses are then trapped by anticyclone around the tropopause levels. This study clearly reveals that tropical cyclones play major role in exchanges of mass and energy between the stratosphere and troposphere (and vice versa) besides being general weather phenomena.</p>

scholarly journals The Impact of Mountain Waves on an Idealized Baroclinically Unstable Large-Scale Flow

2018 ◽  
Vol 75 (9) ◽  
pp. 3285-3302 ◽  
Author(s):  
Maximo Q. Menchaca ◽  
Dale R. Durran
Keyword(s):  
Wave Breaking ◽  
Large Scale ◽  
Lower Stratosphere ◽  
Unstable Wave ◽  
Mean Flow ◽  
Mountain Waves ◽  
Upper Troposphere ◽  
Low Level ◽  
Flow Deceleration ◽  
Large Scale Flow

Abstract The feedback of mountain waves and low-level blocking on an idealized baroclinically unstable wave passing over an isolated ridge is examined through numerical simulation. Theoretical analysis implies that the volume-integrated perturbation momentum budget is dominated by mean-flow deceleration, the divergence of vertical fluxes of horizontal momentum, and the Coriolis force acting on the perturbation ageostrophic wind. These do indeed appear as the dominant balances in numerically computed budgets averaged over layers containing 1) wave breaking in the lower stratosphere, 2) flow blocking with wave breaking near the surface, and 3) a region of pronounced horizontally averaged mean-flow deceleration in the upper troposphere where there is no wave breaking. The local impact of wave breaking on the jet in the lower stratosphere is dramatic, with winds in the jet core reduced by almost 50% relative to the no-mountain case. Although it is the layer with the strongest average deceleration, the local patches of decelerated flow are weakest in the upper troposphere. The cross-mountain pressure drag over a 2-km-high ridge greatly exceeds the vertical momentum flux at mountain-top level because of low-level wave breaking, blocking, and lateral flow diversion. These pressure drags and the low-level momentum fluxes are significantly different from corresponding values computed for simulations with steady forcing matching the instantaneous conditions over the mountain in the evolving large-scale flow.

scholarly journals Mixing Layer Formation near the Tropopause Due to Gravity Wave–Critical Level Interactions in a Cloud-Resolving Model

2004 ◽  
Vol 61 (24) ◽  
pp. 3112-3124 ◽  
Author(s):  
Mohamed Moustaoui ◽  
Binson Joseph ◽  
Hector Teitelbaum
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Critical Level ◽  
Mixing Layer ◽  
Mixing Layers ◽  
Upper Troposphere ◽  
Cloud Resolving Model ◽  
Tropopause Region ◽  
Plausible Mechanism

Abstract A plausible mechanism for the formation of mixing layers in the lower stratosphere above regions of tropical convection is demonstrated numerically using high-resolution, two-dimensional (2D), anelastic, nonlinear, cloud-resolving simulations. One noteworthy point is that the mixing layer simulated in this study is free of anvil clouds and well above the cloud anvil top located in the upper troposphere. Hence, the present mechanism is complementary to the well-known process by which overshooting cloud turrets causes mixing within stratospheric anvil clouds. The paper is organized as a case study verifying the proposed mechanism using atmospheric soundings obtained during the Central Equatorial Pacific Experiment (CEPEX), when several such mixing layers, devoid of anvil clouds, had been observed. The basic dynamical ingredient of the present mechanism is (quasi stationary) gravity wave–critical level interactions, occurring in association with a reversal of stratospheric westerlies to easterlies below the tropopause region. The robustness of the results is shown through simulations at different resolutions. The insensitivity of the qualitative results to the details of the subgrid scheme is also evinced through further simulations with and without subgrid mixing terms. From Lagrangian reconstruction of (passive) ozone fields, it is shown that the mixing layer is formed kinematically through advection by the resolved-scale (nonlinear) velocity field.

ESTIMATION OF TECHNICAL, SPECIALIZED AND ECONOMIC EFFICIENCY OF CULTIVATED POTATO VARIETIES USING DATA ENVELOPE ANALYSIS METHOD (DEA) IN IRAQ FOR SPRING LUG 2018

2020 ◽  
pp. 119-131
Keyword(s):  
Technical Efficiency ◽  
Economic Efficiency ◽  
Potato Crop ◽  
Economic Status ◽  
Analysis Method ◽  
Envelope Analysis ◽  
Variable Capacity ◽  
Data Envelope Analysis ◽  
Using Data ◽  
The Stability

Research highlights the importance of potato crop, which occupies a prominent food and economic status in food security besides rice, wheat and corn at the local and global level. Despite the expansion of the cultivation of potato crop in Iraq in general and Ameriyah district in particular However, potato productivity remains substandard, this may be due to a lack of knowledge of the most efficient varieties and not to use productive resources at the levels at which technical, specialized and economic efficiency is achieved. Therefore, the aim of the research is to determine the technical, specialized and economic efficiency according to the cultivated seed category. The data envelope analysis (DEA) method was used to estimate technical, specialized and economic efficiency, assuming constant and variable capacity returns. As a result of the study, the Safrana variety achieved the highest average technical efficiency according to the stability of the yield and capacity efficiency in addition to achieving the highest average specialized and economic efficiency, The Lapadia variety achieved the highest average technical efficiency, assuming that capacity returns have changed. Therefore, we recommend the adoption of items that achieve higher efficiency and the need to redistribute the elements of production better and Achieving the optimum levels at which technical, specialized and economic efficiency is achieved and saving what has been wasted.

scholarly journals The Role of Employment Protection during an Exogenous Shock to an Economy

2011 ◽  
Vol 11 (2) ◽  
pp. 1850225 ◽  
Author(s):  
Miki Malul ◽  
Mosi Rosenboim ◽  
Tal Shavit ◽  
Shlomo Yedidia Tarba
Keyword(s):  
Economic Crisis ◽  
Employment Protection ◽  
Exogenous Shock ◽  
Unemployment Rates ◽  
World Crisis ◽  
Automatic Stabilizer ◽  
Medium Level ◽  
Using Data ◽  
The Stability

This paper explores the role of employment protection when powerful external crises reduce demand for products. We first present a theoretical framework that shows that employment protection has a U-shaped effect on abnormal unemployment during a negative exogenous shock to an economy. Using data from the 33 OECD countries, we analyze how the level of employment protection affected the stability of unemployment rates during the recent global economic crisis. The results suggest that countries with an intermediate level of employment protection will have more stable unemployment rates during a world crisis. The policy implication of our paper is that countries should seek a medium level of employment protection that may act as an automatic stabilizer of the economy on the macro level.

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