A Case Study on the Impact of Moisture Variability on Convection Initiation Using Radar Refractivity Retrievals

2010 ◽  
Vol 49 (8) ◽  
pp. 1766-1778 ◽  
Author(s):  
D. Bodine ◽  
P. L. Heinselman ◽  
B. L. Cheong ◽  
R. D. Palmer ◽  
D. Michaud
Keyword(s):  
Inversion Layer ◽  
Small Scale ◽  
Low Level ◽  
Dewpoint Temperature ◽  
Observation Network ◽  
Convergence Zones ◽  
Convection Initiation ◽  
The Impact ◽  
Moisture Variability

Abstract A case study illustrating the impact of moisture variability on convection initiation in a synoptically active environment without strong moisture gradients is presented. The preconvective environment on 30 April 2007 nearly satisfied the three conditions for convection initiation: moisture, instability, and a low-level lifting mechanism. However, a sounding analysis showed that a low-level inversion layer and high LFC would prevent convection initiation because the convective updraft velocities required to overcome the convective inhibition (CIN) were much higher than updraft velocities typically observed in convergence zones. Radar refractivity retrievals from the Twin Lakes, Oklahoma (KTLX), Weather Surveillance Radar-1988 Doppler (WSR-88D) showed a moisture pool contributing up to a 2°C increase in dewpoint temperature where the initial storm-scale convergence was observed. The analysis of the storm-relative wind field revealed that the developing storm ingested the higher moisture associated with the moisture pool. Sounding analyses showed that the moisture pool reduced or nearly eliminated CIN, lowered the LFC by about 500 m, and increased CAPE by 2.5 times. Thus, these small-scale moisture changes increased the likelihood of convection initiation within the moisture pool by creating a more favorable thermodynamic environment. The results suggest that refractivity data could improve convection initiation forecasts by assessing moisture variability at finer scales than the current observation network.

scholarly journals Mountain-Wave Propagation under Transient Tropospheric Forcing: A DEEPWAVE Case Study

2018 ◽  
Vol 146 (6) ◽  
pp. 1861-1888 ◽  
Author(s):  
Tanja C. Portele ◽  
Andreas Dörnbrack ◽  
Johannes S. Wagner ◽  
Sonja Gisinger ◽  
Benedikt Ehard ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Wave Attenuation ◽  
Small Scale ◽  
Propagation Time ◽  
Mountain Range ◽  
Mountain Wave ◽  
Low Level ◽  
Momentum Fluxes ◽  
The Impact

The impact of transient tropospheric forcing on the deep vertical mountain-wave propagation is investigated by a unique combination of in situ and remote sensing observations and numerical modeling. The temporal evolution of the upstream low-level wind follows approximately a [Formula: see text] shape and was controlled by a migrating trough and connected fronts. Our case study reveals the importance of the time-varying propagation conditions in the upper troposphere and lower stratosphere (UTLS). Upper-tropospheric stability, the wind profile, and the tropopause strength affected the observed and simulated wave response in the UTLS. Leg-integrated along-track momentum fluxes ([Formula: see text]) and amplitudes of vertical displacements of air parcels in the UTLS reached up to 130 kN m−1 and 1500 m, respectively. Their maxima were phase shifted to the maximum low-level forcing by ≈8 h. Small-scale waves ([Formula: see text] km) were continuously forced, and their flux values depended on wave attenuation by breaking and reflection in the UTLS region. Only maximum flow over the envelope of the mountain range favored the excitation of longer waves that propagated deeply into the mesosphere. Their long propagation time caused a retarded enhancement of observed mesospheric gravity wave activity about 12–15 h after their observation in the UTLS. For the UTLS, we further compared observed and simulated [Formula: see text] with fluxes of 2D quasi-steady runs. UTLS momentum fluxes seem to be reproducible by individual quasi-steady 2D runs, except for the flux enhancement during the early decelerating forcing phase.

scholarly journals Numerical simulations of June 7, 2020 convective precipitation over Slovakia using deterministic, probabilistic, and convection-permitting approaches

Időjárás ◽  
2021 ◽  
Vol 125 (4) ◽  
pp. 571-607
Author(s):  
André Simon ◽  
Martin Belluš ◽  
Katarína Čatlošová ◽  
Mária Derková ◽  
Martin Dian ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Weather Prediction ◽  
Severe Weather ◽  
Precipitation Forecast ◽  
Convective Precipitation ◽  
Small Scale ◽  
Limited Area ◽  
Systematic Effect ◽  
The Impact

The paper presented is dedicated to the evaluation of the influence of various improvements to the numerical weather prediction (NWP) systems exploited at the Slovak Hydrometeorological Institute (SHMÚ). The impact was illustrated in a case study with multicell thunderstorms and the results were confronted with the reference analyses from the INCA nowcasting system, regional radar reflectivity data, and METEOSAT satellite imagery. The convective cells evolution was diagnosed in non-hydrostatic dynamics experiments to study weak mesoscale vortices and updrafts. The growth of simulated clouds and evolution of the temperature at their top were compared with the brightness temperature analyzed from satellite imagery. The results obtained indicated the potential for modeling and diagnostics of small-scale structures within the convective cloudiness, which could be related to severe weather. Furthermore, the non-hydrostatic dynamics experiments related to the stability and performance improvement of the time scheme led to the formulation of a new approach to linear operator definition for semi-implicit scheme (in text referred as NHHY). We demonstrate that the execution efficiency has improved by more than 20%. The exploitation of several high resolution measurement types in data assimilation contributed to more precise position of predicted patterns and precipitation representation in the case study. The non-hydrostatic dynamics provided more detailed structures. On the other hand, the potential of a single deterministic forecast of prefrontal heavy precipitation was not as high as provided by the ensemble system. The prediction of a regional ensemble system A-LAEF (ALARO Limited Area Ensemble Forecast) enhanced the localization of precipitation patterns. Though, this was rather due to the simulation of uncertainty in the initial conditions and also because of the stochastic perturbation of physics tendencies. The various physical parameterization setups of A-LAEF members did not exhibit a systematic effect on precipitation forecast in the evaluated case. Moreover, the ensemble system allowed an estimation of uncertainty in a rapidly developing severe weather case, which was high even at very short range.

THE ROLE OF YOUTH ORGANIZATIONS IN INCREASING CHILDREN'S READING INTEREST: A CASE STUDY OF OEMAH DOLAN ORGANIZATIONS IN KEDONGDONG VILLAGE, SUSUKAN DISTRICT, CIREBON REGENCYIl

2021 ◽  
Vol 5 (2) ◽  
pp. 1161-1171
Author(s):  
Alifatuz Zahro
Keyword(s):  
Qualitative Approach ◽  
Youth Organizations ◽  
Low Level ◽  
Analysis Technique ◽  
Children's Reading ◽  
The Impact ◽  
Reading Interest ◽  
Descriptive Qualitative

The impact of the modernization era on elementary and Kindergaten children can be seen from the intensity of children playing with gadgets, and the low level of literacy in children. This is the background for the presence of the Oemah Dolan organization. This study aims to identify and describe Oemah Dolan's programs and the role of Oemah Dolan in increasing reading interest in children in Kedongdong Village. This study uses a descriptive-qualitative approach with the analysis technique of Miles and Huberman. The results of this study indicate that Oemah Dolan has several programs, namely: book stalls, reading, fun learning, and creativity week.

scholarly journals Noise assessment of the small-scale wind farm

2019 ◽  
Vol 112 ◽  
pp. 02011
Author(s):  
Cristian-Gabriel Alionte ◽  
Daniel-Constantin Comeaga
Keyword(s):  
Power Systems ◽  
Large Scale ◽  
Wind Farm ◽  
Wind Farms ◽  
Small Scale ◽  
Large Power ◽  
Small Power ◽  
Noise Assessment ◽  
The Impact

The importance of renewable energy and especially of eolian systems is growing. For this reason, we propose the investigation of an important pollutant - the noise, which has become so important that European Commission and European Parliament introduced Directive 2002/49/CE relating to the assessment and management of environmental noise. So far, priority has been given to very large-scale systems connected to national energy systems, wind farms whose highly variable output power could be regulated by large power systems. Nowadays, with the development of small storage capacities, it is feasible to install small power wind turbines in cities of up to 10,000 inhabitants too. As a case study, we propose a simulation for a rural locality where individual wind units could be used. This specific case study is interesting because it provides a new perspective of the impact of noise on the quality of life when the use of this type of system is implemented on a large scale. This option, of distributed and small power wind turbine, can be implemented in the future as an alternative or an adding to the common systems.

scholarly journals The Impact of Structural Reforms on Wages and Employment: The Case of Formal versus Informal Workers in Bolivia

2004 ◽  
pp. 91-122
Author(s):  
Julius Spatz
Keyword(s):  
Small Scale ◽  
Reform Process ◽  
Structural Reforms ◽  
Public Companies ◽  
Informal Workers ◽  
Transmission Mechanisms ◽  
Factor Markets ◽  
Set Up ◽  
The Impact

This paper seeks to contribute to the ongoing controversy on the distributional effects of structural reforms in developing countries. To this end, we set up a small-scale macroeconomic model of a dual economy to capture the transmission mechanisms through which the deregulation of product and factor markets, the liberalization of the trade and FDI regime, and the privatization of public companies impact on the distribution of employment and wages between the formal and the informal sector. We empirically test the implications of our theoretical model in a detailed case study on the structural reform process in Bolivia since 1985.

scholarly journals On the Orographically Generated Low-Level Easterly Jet and Severe Downslope Storms of March 2006 over the Tacheng Basin of Northwest China

2018 ◽  
Vol 146 (6) ◽  
pp. 1667-1683 ◽  
Author(s):  
Guangxing Zhang ◽  
Da-Lin Zhang ◽  
Shufang Sun
Keyword(s):  
Large Scale ◽  
Inversion Layer ◽  
Dust Storms ◽  
Frozen Soil ◽  
Gradient Force ◽  
Mountain Range ◽  
Pressure Gradient Force ◽  
Low Level ◽  
Downslope Winds ◽  
The Impact

A high-latitude low-level easterly jet (LLEJ) and downslope winds, causing severe dust storms over the Tacheng basin of northwestern China in March 2006 when the dust source regions were previously covered by snow with frozen soil, are studied in order to understand the associated meteorological conditions and the impact of complex topography on the generation of the LLEJ. Observational analyses show the development of a large-scale, geostrophically balanced, easterly flow associated with a northeastern high pressure and a southeastern low pressure system, accompanied by a westward-moving cold front with an intense inversion layer near the altitudes of mountain ridges. A high-resolution model simulation shows the generation of an LLEJ of near-typhoon strength, which peaked at about 500 m above the ground, as well as downslope windstorms with marked wave breakings and subsidence warming in the leeside surface layer, as the large-scale cold easterly flow moves through a constricting saddle pass and across a higher mountain ridge followed by a lower parallel ridge, respectively. The two different airstreams are merged to form an intense LLEJ of cold air, driven mostly by zonal pressure gradient force, and then the LLEJ moves along a zonally oriented mountain range to the north. Results indicate the importance of the lower ridge in enhancing the downslope winds associated with the higher ridge and the importance of the saddle pass in generating the LLEJ. We conclude that the intense downslope winds account for melting snow, warming and drying soils, and raising dust into the air that is then transported by the LLEJ, generated mostly through the saddle pass, into the far west of the basin.

scholarly journals TARGET BENEFICIARY PARTICIPATION AND ITS IMPACT ON THE IMPLEMENTATION OF CDF FUNDED PROJECTS: A CASE STUDY OF LAMU EAST CONSTITUENCY

2017 ◽  
Vol 2 (1) ◽  
pp. 73-90
Author(s):  
Aisha M. Mohamed ◽  
Dr. Moses M. Otieno
Keyword(s):  
Project Management ◽  
Case Study Research ◽  
Target Population ◽  
Specific Reference ◽  
Level Of Education ◽  
Low Level ◽  
Awareness Campaigns ◽  
The Government ◽  
The Impact

Purpose: The aim of this study was to establish the impact of beneficiary involvement and participation in CDF funded projects with specific reference of CDF projects in LAMU Constituency.Methodology: The study adopted a descriptive case study research design. The population of the study consisted of 107 projects in Lamu East constituency. This implied that 107 project management committees (PMC) were the target population. The preferred data collection instrument was a questionnaire. The data was analyzed by both statistical package for social sciences (SPSS) and excel spreadsheet.Results: The study findings indicated that the beneficiaries /community members of Lamu East constituency were not given the opportunity or right to participate in evaluating, Selecting and prioritizing projects.   Overall, there was low beneficiary participation in CDF projects. From the findings, it is possible to conclude that that there is a low awareness of CDF projects in LAMU east constituency. Furthermore, the level of education of project beneficiaries was low. The low level of awareness may have led to the low participation of beneficiaries. To a large extent the level of education had affected the level of participation in CDF funded projects. It was also possible to conclude that the low level of education may have led to the low participation of beneficiaries in CDF projects. Finally, it was possible to conclude that, the low level of beneficiary participation affected CDF project implementation.Unique contribution to theory, practice and policy:  It was recommended that the project management committees should encourage the participation of beneficiaries in evaluating, selecting and prioritizing projects, determining the location of the projects, follow-up or monitor the project and participation of management of project funds. Furthermore, the Government through the CDF committee should carry out awareness campaigns to sensitize the beneficiaries of their right and obligation to participate in CDF projects.

scholarly journals The impact of GPS and high-resolution radiosonde nudging on the simulation of heavy precipitation during HyMeX IOP6

2021 ◽  
Author(s):  
Alberto Caldas-Alvarez ◽  
Samiro Khodayar ◽  
Peter Knippertz
Keyword(s):  
High Resolution ◽  
Temporal Resolution ◽  
Hydrological Cycle ◽  
Weather Prediction ◽  
Heavy Precipitation ◽  
Convective Precipitation ◽  
Small Scale ◽  
High Temporal Resolution ◽  
The Impact

Abstract. Heavy precipitation is one of the most devastating weather extremes in the western Mediterranean region. Our capacity to prevent negative impacts from such extreme events requires advancements in numerical weather prediction, data assimilation and new observation techniques. In this paper we investigate the impact of two state-of-the-art data sets with very high resolution, Global Positioning System-Zenith Total Delays (GPS-ZTD) with a 10 min temporal resolution and radiosondes with ~700 levels, on the representation of convective precipitation in nudging experiments. Specifically, we investigate whether the high temporal resolution, quality, and coverage of GPS-ZTDs can outweigh their lack of vertical information or if radiosonde profiles are more valuable despite their scarce coverage and low temporal resolution (24 h to 6 h). The study focuses on the Intensive Observation Period 6 (IOP6) of the Hydrological Cycle in the Mediterranean eXperiment (HyMeX; 24 September 2012). This event is selected due to its severity (100 mm/12 h), the availability of observations for nudging and validation, and the large observation impact found in preliminary sensitivity experiments. We systematically compare simulations performed with the COnsortium for Small scale MOdelling (COSMO) model assimilating GPS, high- and low vertical resolution radiosoundings in model resolutions of 7 km, 2.8 km and 500 m. The results show that the additional GPS and radiosonde observations cannot compensate errors in the model dynamics and physics. In this regard the reference COSMO runs have an atmospheric moisture wet bias prior to precipitation onset but a negative bias in rainfall, indicative of deficiencies in the numerics and physics, unable to convert the moisture excess into sufficient precipitation. Nudging GPS and high-resolution soundings corrects atmospheric humidity, but even further reduces total precipitation. This case study also demonstrates the potential impact of individual observations in highly unstable environments. We show that assimilating a low-resolution sounding from Nimes (southern France) while precipitation is taking place induces a 40 % increase in precipitation during the subsequent three hours. This precipitation increase is brought about by the moistening of the 700  hPa level (7.5 g kg−1) upstream of the main precipitating systems, reducing the entrainment of dry air above the boundary layer. The moist layer was missed by GPS observations and high-resolution soundings alike, pointing to the importance of profile information and timing. However, assimilating GPS was beneficial for simulating the temporal evolution of precipitation. Finally, regarding the scale dependency, no resolution is particularly sensitive to a specific observation type, however the 2.8 km run has overall better scores, possibly as this is the optimally tuned operational version of COSMO. In follow-up experiments the Icosahedral Nonhydrostatic Model (ICON) will be investigated for this case study to assert whether its numerical and physics updates, compared to its predecessor COSMO, are able to improve the quality of the simulations.

scholarly journals Heavy Rainfall Associated with Double Low-Level Jets over Southern China. Part II: Convection Initiation

2019 ◽  
Vol 147 (2) ◽  
pp. 543-565 ◽  
Author(s):  
Yu Du ◽  
Guixing Chen
Keyword(s):  
Heavy Rainfall ◽  
Mesoscale Model ◽  
Southern China ◽  
Northern South China Sea ◽  
Lower Troposphere ◽  
Small Scale ◽  
The South ◽  
Low Level ◽  
Low Level Jets ◽  
Convection Initiation

Abstract Heavy rainfall that occurred at the south coast of China on 10–11 May 2014 was associated with a synoptic-system-related low-level jet (SLLJ) and a boundary layer jet (BLJ). To clarify the role of the double low-level jets in convection initiation (CI), we perform convective-permitting simulations using a nonhydrostatic mesoscale model. The simulations reproduce the occurrence location and mesoscale evolution of new convective cells as well as their small-scale wavelike structures at the elevated layers, which are generally consistent with radar observations despite some differences in their orientation. The nighttime BLJ over the northern South China Sea strengthens the convergence at ~950 hPa near the coast where the BLJ’s northern terminus reaches the coastal terrain. Meanwhile, the SLLJ to the south of the inland cold front provides divergence at ~700 hPa near the SLLJ’s entrance region. Such low-level convergence and midlevel divergence collectively produce strong mesoscale lifting for CI at the coast. In addition to the enhanced mesoscale lifting, the double low-level jets also provide favorable conditions for the superimposed small-scale disturbances that can serve as effective moistening mechanisms of the lower troposphere during CI. In a sensitivity experiment with coastal terrain removed, CI still occurs near the coast but is delayed and weaker compared to the control run. This latter experiment suggests that double low-level jets and their coupling indeed exert key effects on CI, while the BLJ colliding with terrain may enhance coastal convergence for amplifying CI. These findings provide new insights into the occurrence of coastal heavy rainfall in the warm sector far ahead of the fronts.

Sign in / Sign up

Export Citation Format

Share Document