scholarly journals Impact of TMI SST on the Simulation of a Heavy Rainfall Episode over Mumbai on 26 July 2005

2008 ◽  
Vol 136 (10) ◽  
pp. 3714-3741 ◽  
Author(s):  
S. K. Deb ◽  
C. M. Kishtawal ◽  
P. K. Pal ◽  
P. C. Joshi
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Convective Available Potential Energy ◽  
India Meteorological Department ◽  
Tropical Rainfall Measuring Mission ◽  
Atmospheric Modeling ◽  
Cumulus Parameterization ◽  
Surface Boundary ◽  
Maximum Rainfall ◽  
The Impact

In this study the simulation of a severe rainfall episode over Mumbai on 26 July 2005 has been attempted with two different mesoscale models. The numerical models used in this study are the Brazilian Regional Atmospheric Modeling System (BRAMS) developed originally by Colorado State University and the Advanced Research Weather Research Forecast (WRF-ARW) Model, version 2.0.1, developed at the National Center for Atmospheric Research. The simulations carried out in this study use the Grell–Devenyi Ensemble cumulus parameterization scheme. Apart from using climatological sea surface temperature (SST) for the control simulations, the impact of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) SST on the simulation of rainfall is evaluated using these two models. The performances of the models are compared by examining the predicted parameters like upper- and lower-level circulations, moisture, temperature, and rainfall. The strength of convective instability is also derived by calculating the convective available potential energy. The intensity of maximum rainfall around Mumbai is significantly improved with TMI SST as the surface boundary condition in both the models. The large-scale circulation features, moisture, and temperature are compared with those in the National Centers for Environmental Prediction analyses. The rainfall prediction is assessed quantitatively by comparing the simulated rainfall with the rainfall from TRMM products and the observed station values reported in Indian Daily Weather Reports from the India Meteorological Department.

scholarly journals Physical Mechanisms Regulating Summertime Rainfall over Northwestern Australia

2011 ◽  
Vol 24 (14) ◽  
pp. 3705-3717 ◽  
Author(s):  
Gareth Berry ◽  
Michael J. Reeder ◽  
Christian Jakob
Keyword(s):  
Large Scale ◽  
Convective Available Potential Energy ◽  
Tropical Rainfall Measuring Mission ◽  
Maximum Rainfall ◽  
Diurnal Cycles ◽  
Physical Mechanisms ◽  
Synoptic Variability ◽  
Synoptic Weather ◽  
Dry Conditions ◽  
Northwestern Australia

Abstract Summertime (December–February) rainfall over northwestern Australia has increased significantly since the middle of the twentieth century. As a prerequisite to understanding the observed trend, this investigation examines the broad characteristics of rainfall and identifies the physical mechanisms by which rainfall in the region is initiated. This is achieved using a combination of in situ, spaceborne, and numerical reanalysis datasets. Hourly pluviograph data and the Tropical Rainfall Measuring Mission (TRMM)-3B42 dataset show distinctly different diurnal cycles of rainfall in different geographical subregions; near the coast, rainfall rates peak in the midafternoon, whereas inland (near the maximum rainfall trend) the rainfall rate is largest overnight. These data also indicate that most of the summertime rain falls in events lasting 2–5 days. Analysis of the ECMWF Re-Analysis (ERA-Interim) demonstrates that convergence into the continental heat low controls the diurnal cycle of rainfall but cannot explain the synoptic variability. Composites of wet and dry conditions from ERA-Interim expose synoptic-scale differences in the environmental flow. Prior to rain falling in the interior of northwestern Australia, there is a distinct shift in the origins of low-level air parcels, such that air with high convective available potential energy is advected from the tropical maritime regions, rather than from over the continent. Preliminary analysis suggests that these flow changes may be linked to transient synoptic disturbances such as midlatitude cyclones and monsoon lows. Rather than reflecting a large-scale change in the ocean state, these results imply that the observed increase in rainfall may be linked more closely to changes in the synoptic weather systems.

The importance of phase morphology for rheology of ferropericlase-bridgmanite mixtures

2021 ◽  
Author(s):  
Marcel Thielmann ◽  
Gregor Golabek ◽  
Hauke Marquardt
Keyword(s):  
Lower Mantle ◽  
Mantle Convection ◽  
Effective Viscosity ◽  
Large Scale ◽  
Numerical Models ◽  
Phase Morphology ◽  
Strong Impact ◽  
Analytical Approximations ◽  
The Impact ◽  
Strong Control

<p>The rheology of the Earth’s lower mantle is poorly constrained due to a lack of knowledge of the rheological behaviour of its constituent minerals. In addition, the lower mantle does not consist of only a single, but of multiple mineral phases with differing deformation behaviour. The rheology of Earth’s lower mantle is thus not only controlled by the rheology of its individual constituents (bridgmanite and ferropericlase), but also by their interplay during deformation. This is particularly important when the viscosity contrast between the different minerals is large. Experimental studies have shown that ferropericlase may be significantly weaker than bridgmanite and may thus exert a strong control on lower mantle rheology.</p><p>Here, we thus explore the impact of phase morphology on the rheology of a ferropericlase-bridgmanite mixture using numerical models. We find that elongated ferropericlase structures within the bridgmanite matrix significantly lower the effective viscosity, even in cases where no interconnected network of weak ferropericlase layers has been formed. In addition to the weakening, elongated ferropericlase layers result in a strong viscous anisotropy. Both of these effects may have a strong impact on lower mantle dynamics, which makes is necessary to develop upscaling methods to include them in large-scale mantle convection models. We develop a numerical-statistial approach to link the statistical properties of a ferropericlase-bridgmanite mixture to its effective viscosity tensor. With this approach, both effects are captured by analytical approximations that have been derived to describe the evolution of the effective viscosity (and its anisotropy) of a two-phase medium with aligned elliptical inclusions, thus allowing to include these microscale processes in large-scale mantle convection models.</p>

scholarly journals Sensitivities of Summertime Mesoscale Circulations in the Coastal Carolinas to Modifications of the Kain–Fritsch Cumulus Parameterization

2017 ◽  
Vol 145 (11) ◽  
pp. 4381-4399 ◽  
Author(s):  
Aaron P. Sims ◽  
Kiran Alapaty ◽  
Sethu Raman
Keyword(s):  
Numerical Models ◽  
Deep Convection ◽  
Coastal Region ◽  
Turnover Time ◽  
Cumulus Parameterization ◽  
Parameterization Scheme ◽  
Subgrid Scale ◽  
Mesoscale Circulations ◽  
Near Surface ◽  
The Impact

Two mesoscale circulations, the Sandhills circulation and the sea breeze, influence the initiation of deep convection over the Sandhills and the coast in the Carolinas during the summer months. The interaction of these two circulations causes additional convection in this coastal region. Accurate representation of mesoscale convection is difficult as numerical models have problems with the prediction of the timing, amount, and location of precipitation. To address this issue, the authors have incorporated modifications to the Kain–Fritsch (KF) convective parameterization scheme and evaluated these mesoscale interactions using a high-resolution numerical model. The modifications include changes to the subgrid-scale cloud formulation, the convective turnover time scale, and the formulation of the updraft entrainment rates. The use of a grid-scaling adjustment parameter modulates the impact of the KF scheme as a function of the horizontal grid spacing used in a simulation. Results indicate that the impact of this modified cumulus parameterization scheme is more effective on domains with coarser grid sizes. Other results include a decrease in surface and near-surface temperatures in areas of deep convection (due to the inclusion of the effects of subgrid-scale clouds on the radiation), improvement in the timing of convection, and an increase in the strength of deep convection.

Regional Impacts of Irrigation in Mexico and the Southwestern United States on Hydrometeorological Fields in the North American Monsoon Region

2016 ◽  
Vol 17 (12) ◽  
pp. 2981-2995 ◽  
Author(s):  
Alex Mahalov ◽  
Jialun Li ◽  
Peter Hyde
Keyword(s):  
North American ◽  
Land Surface ◽  
Large Scale ◽  
Rainfall Variability ◽  
Convective Available Potential Energy ◽  
North American Monsoon ◽  
Western Slope ◽  
Surface Model ◽  
Southern Mexico ◽  
The Impact

Abstract In this study, the impacts of Mexican and southwestern U.S. agricultural and urban irrigation on North American monsoon (NAM) rainfall and other hydrometeorological fields are investigated using the Weather Research and Forecasting (WRF) Model by implementing an irrigation scheme into the WRF–land surface model. Taking the 2000–12 monsoon seasons as examples, multiple WRF simulations with irrigation are conducted by designing different crops’ maximum allowable water depletions (SWm). In comparison with gridded rainfall observations in urban and rural area, the WRF simulations with/without irrigation generally capture the observations very well, but with underestimation along the western slope of the Sierra Madre Occidental (SMO) and overestimation over southern Mexico. The simulations of WRF with irrigation are slightly improved over those without irrigation, compared with rainfall and sounding observations. Sensitivity studies reveal that the impact of irrigation on rainfall varies with location and NAM rainfall variability. Irrigation increases rainfall in eastern Arizona–western New Mexico and in northwestern Mexico because of the irrigation-induced increases of convective available potential energy (CAPE) and precipitable water. Overall, irrigation decreases rainfall in western Arizona, along the western slope of the SMO, and in central Mexico because of irrigation-induced increases of convective inhibition (CIN), decreases of CAPE, and/or large-scale water vapor divergence.

scholarly journals Characteristics of Summer Precipitation around the Western Ghats and the Myanmar West Coast

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Dibas Shrestha ◽  
Rashila Deshar ◽  
Kenji Nakamura
Keyword(s):  
West Coast ◽  
Western Ghats ◽  
Large Scale ◽  
Summer Precipitation ◽  
Tropical Rainfall Measuring Mission ◽  
Precipitation Radar ◽  
Maximum Rainfall ◽  
Trmm Precipitation ◽  
The Western Ghats ◽  
Coastal Mountain

Characteristics of summer (June–August) precipitation over two coastal mountain regions in South Asia (Western Ghats: WG and Myanmar West Coast: MWC) with a focus on topographic impact are analyzed using the 13-year (1998–2010) high spatial resolution (0.05° × 0.05°) version 6 data obtained from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). A relationship between precipitation patterns and topography was observed in the coastal mountains. In both the WG and MWC, maximum rainfall along a tight line on the upwind side of the coastal mountains is primarily attributed to rain frequency. However, intense precipitation was observed over the offshore regions. Compared with the WG, deeper and large-scale precipitation systems develop over the MWC, producing more intense rainfall. It is suggested that insufficient humidity deters large-scale convection over the WG, and the atmosphere is sufficiently moist over the MWC.

Can the Deforestation Breeze Change the Rainfall in Amazonia? A Case Study for the BR-163 Highway Region

2010 ◽  
Vol 14 (18) ◽  
pp. 1-25 ◽  
Author(s):  
Sandra I. Saad ◽  
Humberto R. da Rocha ◽  
Maria A. F. Silva Dias ◽  
Rafael Rosolem
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Three Dimensional ◽  
Atmospheric Modeling ◽  
Thermal Cell ◽  
Soil Wetness ◽  
Soil Dryness ◽  
Regional Atmospheric Modeling ◽  
The Impact

Abstract The authors simulated the effects of Amazonian mesoscale deforestation in the boundary layer and in rainfall with the Brazilian Regional Atmospheric Modeling System (BRAMS) model. They found that both the area and shape (with respect to wind incidence) of deforestation and the soil moisture status contributed to the state of the atmosphere during the time scale of several weeks, with distinguishable patterns of temperature, humidity, and rainfall. Deforestation resulted in the development of a three-dimensional thermal cell, the so-called deforestation breeze, slightly shifted downwind to large-scale circulation. The boundary layer was warmer and drier above 1000-m height and was slightly wetter up to 2000-m height. Soil wetness affected the circulation energetics proportionally to the soil dryness (for soil wetness below ∼0.6). The shape of the deforestation controlled the impact on rainfall. The horizontal strips lined up with the prevailing wind showed a dominant increase in rainfall, significant up to about 60 000 km2. On the other hand, in the patches aligned in the opposite direction (north–south), there was both increase and decrease in precipitation in two distinct regions, as a result of clearly separated upward and downward branches, which caused the precipitation to increase for patches up to 15 000 km2. The authors’ estimates for the size of deforestation impacting the rainfall contributed to fill up the low spatial resolution in other previous studies.

scholarly journals Analysis of Major Rainfall Factors Affecting Inundation Based on Observed Rainfall and Random Forest

2020 ◽  
Vol 20 (6) ◽  
pp. 301-310
Author(s):  
Hyunil Kim ◽  
Byunghyun Kim
Keyword(s):  
Random Forest ◽  
Numerical Models ◽  
Statistical Characteristics ◽  
Target Area ◽  
Two Dimensional ◽  
Weather System ◽  
Urban Flood ◽  
Maximum Rainfall ◽  
Factors Affecting ◽  
The Impact

It is important to analyze urban floods according to uncertain rainfall patterns. This study was carried out to determine key statistical characteristics of rainfall affecting the occurrences of flooding by using observed rainfall, one- and two-dimensional hydraulic analysis models, and random forests. The target area selected was the Centum City area of Busan, where flooding occurs frequently with heavy rainfall. For analysis, the rainfall data from the Automatic Weather System (AWS) and radar observatory in the entire city of Busan were collected. Using the results from the one- and two-dimensional numerical models, the occurrence of flooding was determined according to the observed rainfall events. The random forest was used to classify the presence or absence of flooding according to the statistical characteristics of rainfall, and the importance evaluation function was applied to determine the impact of each statistical factor. The three main statistical factors of rainfall with the greatest impact on the occurrence of flooding were analyzed as the 1-hr maximum rainfall, the average rainfall, and the skewness. On the other hand, the three main factors affecting the maximum flood depth were the 3-hrs maximum rainfall, the 1-hr maximum rainfall, and the total rainfall. It is judged that the results of this study will be useful in suggesting quantitative urban flood forecasting standards when rainfall is examined in real-time by using various observation equipment.

scholarly journals FINAL DESIGN OF THE NAGS HEAD BEACH NOURISHMENT PROJECT USING A LONGSHORE NUMERICAL MODEL

2012 ◽  
Vol 1 (33) ◽  
pp. 64 ◽  
Author(s):  
Haiqing Liu Kaczkowski ◽  
Timothy W Kana
Keyword(s):  
Numerical Model ◽  
Large Scale ◽  
Numerical Models ◽  
Normal Wave ◽  
Beach Nourishment ◽  
Shoreline Evolution ◽  
Longshore Transport ◽  
Final Design ◽  
Model Setup ◽  
The Impact

Nags Head, located at the northeastern part of North Carolina in the U.S., has sustained chronic erosion over the past 50 years. In 2005, Coastal Science & Engineering (CSE) was retained by the town of Nags Head to develop an interim beach restoration plan. Profile volume change was used in the planning and preliminary design of the project, and longshore and cross-shore numerical models were used in the final design to refine the preliminary nourishment plan and increase potential longevity of the project. This paper focuses on the key factors of the longshore numerical model setup for the project. These include model selection, input data and parameters, model calibration, and applications under different design alternatives. The Generalized Model for Simulating Shoreline Changes (GENESIS) was used in this study to evaluate shoreline evolution under normal wave conditions during various stages of the design life following the beach nourishment project. The model was used to identify the potential occurrence of erosional hotspots and to optimize the nourishment design so that the effects of such hotspots could be avoided or minimized where possible. Model results were also used to evaluate the impact of borrow area dredging on longshore transport in the project area and the impact of nourishment on shoaling in the adjacent inlet. The project encompasses 10.11 miles (mi) (16.28 kilometers-km) of ocean shoreline, and the design nourishment volume is based on the total permitted volume of 4 million cubic yards (cy) (3 million cubic meters-m³). [Note: As-built length was 10.0 mi and volume was 4.615 million cubic yards.] The final design has fill densities varying from north to south in relation to historical erosion rates and model projections. The average fill density is 75 cubic yards per foot (cy/ft) (188 m³/m) and ranges from 38 cy/ft to 150 cy/ft (95 m³/m to 375 m³/m). In conclusion, it is shown that the numerical model selected in this study was capable of predicting the overall performance of the large scale beach nourishment project in Nags Head as well as the performance at a particular location within or adjacent to the project, and its design methods can offer guidance to future projects.

scholarly journals Precipitation climatology over Mediterranean Basin from ten years of TRMM measurements

2008 ◽  
Vol 17 ◽  
pp. 87-91 ◽  
Author(s):  
A. V. Mehta ◽  
S. Yang
Keyword(s):  
Mediterranean Sea ◽  
Rainy Season ◽  
Mediterranean Region ◽  
Large Scale ◽  
Eastern Mediterranean ◽  
Tropical Rainfall Measuring Mission ◽  
Western Mediterranean ◽  
Sea Temperature ◽  
Maximum Rainfall ◽  
The Mediterranean

Abstract. Climatological features of mesoscale rain activities over the Mediterranean region between 5° W–40° E and 28° N–48° N are examined using the Tropical Rainfall Measuring Mission (TRMM) 3B42 and 2A25 rain products. The 3B42 rainrates at 3-hourly, 0.25°×0.25° spatial resolution for the last 10 years (January 1998 to July 2007) are used to form and analyze the 5-day mean and monthly mean climatology of rainfall. Results show considerable regional and seasonal differences of rainfall over the Mediterranean Region. The maximum rainfall (3–5 mm day−1) occurs over the mountain regions of Europe, while the minimum rainfall is observed over North Africa (~0.5 mm day−1). The main rainy season over the Mediterranean Sea extends from October to March, with maximum rainfall occurring during November–December. Over the Mediterranean Sea, an average rainrate of ~1–2 mm day−1 is observed, but during the rainy season there is 20% larger rainfall over the western Mediterranean Sea than that over the eastern Mediterranean Sea. During the rainy season, mesoscale rain systems generally propagate from west to east and from north to south over the Mediterranean region, likely to be associated with Mediterranean cyclonic disturbances resulting from interactions among large-scale circulation, orography, and land-sea temperature contrast.

scholarly journals A Cumulus Parameterization with State-Dependent Entrainment Rate. Part II: Impact on Climatology in a General Circulation Model

2010 ◽  
Vol 67 (7) ◽  
pp. 2194-2211 ◽  
Author(s):  
Minoru Chikira
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Convective Available Potential Energy ◽  
Circulation Model ◽  
South Pacific Convergence Zone ◽  
Cumulus Parameterization ◽  
Convergence Zone ◽  
Entrainment Rate ◽  
Cumulus Congestus ◽  
The Impact

Abstract The impact of a new cumulus parameterization developed in Part I of this paper on climatology in an atmospheric general circulation model (AGCM) is compared with that of the Arakawa–Schubert scheme. The parameterization is characterized by a vertically variable entrainment rate depending on the surrounding environment. Two kinds of formulations on entrainment rate are tested and produce similar results in the AGCM. The results show reduction of precipitation over land and increase over the sea, weakening of the southern side of the double intertropical convergence zone (ITCZ) over the southeastern Pacific, and better representation of the South Pacific convergence zone (SPCZ), all of which are consistent with observations. The population of cumulus congestus is significantly increased, thereby inducing additional heating in the lower troposphere. The diurnal variation over land shows that deep convection tends to be suppressed earlier because of the reduction of convective available potential energy and tropospheric humidity caused by the convective activity itself. An analysis of the daily outputs suggests that a better representation of the cumulus congestus and sensitivity of the scheme to tropospheric humidity are important for the realistic representation of the precipitation over the double ITCZ and SPCZ.

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