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 Characteristics of shallow thermally driven flow in the complex topography of the south-eastern Adriatic

2010 ◽  
Vol 28 (10) ◽  
pp. 1905-1922 ◽  
Author(s):  
M. T. Prtenjak ◽  
I. Tomažić ◽  
I. Kavčič ◽  
S. Đivanović
Keyword(s):  
Large Scale ◽  
Sea Breeze ◽  
Small Scale ◽  
The South ◽  
Fine Grid ◽  
Easterly Wind ◽  
Sodar Data ◽  
South Eastern ◽  
The North ◽  
Convergence Zones

Abstract. Characteristics of thermally induced flow, namely the sea breeze, are investigated along the south-eastern Adriatic. The chosen period 24–25 April 2006 favoured sea breeze development and simultaneously allowed a comparison of the large-scale wind influence (north-westerly wind versus south-easterly wind) and the complex terrain on the local circulations. Particular attention is paid to the small-scale formation of the wind field, convergence zones (CZs), channelling flows and small scale eddies, especially in the vicinity of two airports in the central part of south-eastern Adriatic. The results are based on wind measurements (from meteorological surface stations, radiosoundings, satellite data and sodar data) and further supplemented by model data at fine grid spacing. This study shows the formation of numerous irregular daytime and nighttime CZs, which occurred along the coastline in the lee of mountains and over the larger, elongated islands. The results show that the above mentioned airports are surrounded by daytime CZ formations within the lowermost 1000 m and associated updrafts of 1 m s−1, especially if CZs are maintained by the north-westerly large-scale winds. Whereas the daytime CZ was generated due to merged sea breezes, the weaker and shallower nighttime CZs were formed by wind convergence of the seaward breezes, and significantly modified by the large-scale flow of the topography (e.g., accelerated flow in the sea channels and substantial swirled flows around the islands). The passes between the coastal mountain peaks changed the inflow penetration, provoking the increase in wind speed of the channelled flow. The strongest sea breeze channelling was observed above the valley of the Neretva River, where the onshore flow reached 40 km inland with a strength of 8 m s−1, and the highly asymmetric offshore part was confined within the sea channel.

scholarly journals The 23–26 September 2012 U.K. Floods: Using PV Surgery to Quantify Sensitivity to Upper-Level Forcing

2017 ◽  
Vol 145 (10) ◽  
pp. 4055-4079 ◽  
Author(s):  
Sam Hardy ◽  
David M. Schultz ◽  
Geraint Vaughan
Keyword(s):  
United Kingdom ◽  
Large Scale ◽  
Extreme Event ◽  
Initial Conditions ◽  
Initial Position ◽  
River Flooding ◽  
The United Kingdom ◽  
Accumulated Rainfall ◽  
Upper Level ◽  
The Impact

Major river flooding affected the United Kingdom in late September 2012 as a slow-moving extratropical cyclone brought over 150 mm of rain to parts of northern England and north Wales. The cyclone deepened over the United Kingdom on 24–26 September as a potential vorticity (PV) anomaly approached from the northwest, elongated into a PV streamer, and wrapped around the cyclone. The strength and position of the PV anomaly is modified in the initial conditions of Weather Research and Forecasting Model simulations, using PV surgery, to examine whether different upper-level forcing, or different phasing between the PV anomaly and cyclone, could have produced an even more extreme event. These simulations reveal that quasigeostrophic (QG) forcing for ascent ahead of the anomaly contributed to the persistence of the rainfall over the United Kingdom. Moreover, weakening the anomaly resulted in lower rainfall accumulations across the United Kingdom, suggesting that the impact of the event might be proportional to the strength of the upper-level QG forcing. However, when the anomaly was strengthened, it rotated cyclonically around a large-scale trough over Iceland rather than moving eastward as in the verifying analysis, with strongly reduced accumulated rainfall across the United Kingdom. A similar evolution developed when the anomaly was moved farther away from the cyclone. Conversely, moving the anomaly nearer to the cyclone produced a similar solution to the verifying analysis, with slightly increased rainfall totals. These counterintuitive results suggest that the verifying analysis represented almost the highest-impact scenario possible for this flooding event when accounting for sensitivity to the initial position and strength of the PV anomaly.

scholarly journals Model and Observational Analysis of the Northeast U.S. Regional Climate and Its Relationship to the PNA and NAO Patterns during Early Winter

2006 ◽  
Vol 134 (11) ◽  
pp. 3479-3505 ◽  
Author(s):  
M. Notaro ◽  
W-C. Wang ◽  
W. Gong
Keyword(s):  
New York ◽  
Great Lakes ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Early Winter ◽  
Upper Level ◽  
Upper Level Jet ◽  
The Impact ◽  
Nao Pattern

Abstract The relationship between the large-scale circulation and regional climate of the northeast United States is investigated for early winter using observational data and the State University of New York at Albany regional climate model. Simulated patterns of temperature, precipitation, and atmospheric circulation compare well with observations, despite a cold, dry bias. Ten December runs are analyzed to investigate the impact of the Pacific–North American (PNA) pattern on temperature, precipitation, clouds, and circulation features. During a positive PNA pattern, the simulated and observed eastern U.S. jet shifts to the southeast, coinciding with cold, dry conditions in the Northeast. This shift and intensification of the upper-level jet stream during a positive PNA pattern coincides with a greater frequency of cyclones and anticyclones along a distinct southwest–northeast track. Despite increased cyclone activity, total wintertime precipitation is below normal during a positive PNA pattern because of enhanced stability and subsidence over land, along with lower-atmospheric moisture content. Lower surface air temperatures during a positive PNA pattern result in enhanced simulated cloud cover over the Great Lakes and Atlantic Ocean due to increased thermal contrast and fluxes of sensible and latent heat, and a reduction in clouds over land. Interactions between the PNA and North Atlantic Oscillation (NAO) patterns impact the Northeast winter climate. Observed frontal passages through New York are most abundant during a negative PNA and positive NAO pattern, with a zonal upper-level jet positioned over New York. A positive PNA pattern is frequently characterized by an earlier observed Great Lakes ice season, while the greatest lake-effect snowfall occurs during a positive PNA and negative NAO pattern. The NAO pattern has the largest impact on northeast U.S. temperatures and the eastern U.S. upper-level jet during a positive PNA pattern.

scholarly journals Warm Organized Rain Systems over the Tropical Eastern Pacific

2016 ◽  
Vol 29 (9) ◽  
pp. 3403-3422 ◽  
Author(s):  
Baohua Chen ◽  
Chuntao Liu
Keyword(s):  
Large Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Mean Value ◽  
Eastern Pacific ◽  
Tropical Eastern Pacific ◽  
Rain Area ◽  
Near Surface ◽  
Thermodynamic Structure ◽  
Low Level ◽  
Upper Level

Abstract This study uses 16-yr Tropical Rainfall Measuring Mission (TRMM) radar precipitation feature (RPF) data to characterize warm rain systems in the tropics with large horizontal extensions, referred to as warm organized rain systems. The systems are selected by specifying the RPFs with minimum infrared brightness temperature warmer than 0°C and rain area greater than 500 km2. ERA-Interim atmospheric fields and SST from NOAA are analyzed to highlight the environmental characteristics of warm organized rain systems. Warm organized systems occur over specific oceanic regions, including the eastern Pacific ITCZ, the eastern part of the SPCZ, and coastal regions. In contrast with ubiquitous warm isolated RPFs, warm organized systems have greater near-surface radar reflectivity. The rainfall amounts generated by warm organized systems are greater in winter than in summer. Composite analyses indicate that warm organized RPFs prefer to coexist with a dry midtroposphere associated with a strong upper-level descent, an enhanced near-surface moisture convergence, and a strong low-level large-scale ascent. The shallow meridional circulation in the eastern Pacific is significantly stronger for warm organized RPFs compared to the circulation for warm isolated RPFs. Warm organized systems over the tropical eastern Pacific occur at warm SSTs with mean value of about 27°C and a strong SST meridional gradient. The warm organized RPFs in the tropical eastern Pacific are found to be at the southern edge of deep ITCZ cores. This is probably related to the meridional asymmetrical thermodynamic structure over the eastern Pacific ITCZ with a higher low-level humidity to the south. Similar favorable large-scale environments for the warm organized RPFs are also found over the SPCZ and other regions.

scholarly journals Experiential Learning in Vehicle Dynamics Education via Motion Simulation and Interactive Gaming

2009 ◽  
Vol 2009 ◽  
pp. 1-15 ◽  
Author(s):  
Kevin Hulme ◽  
Edward Kasprzak ◽  
Ken English ◽  
Deborah Moore-Russo ◽  
Kemper Lewis
Keyword(s):  
Postsecondary Education ◽  
Vehicle Dynamics ◽  
Large Scale ◽  
Physical Simulation ◽  
Traditional Classroom ◽  
Motion Simulation ◽  
Student Centered ◽  
Student Centered Learning ◽  
Upper Level ◽  
The Impact

Creating active, student-centered learning situations in postsecondary education is an ongoing challenge for engineering educators. Contemporary students familiar with visually engaging and fast-paced games can find traditional classroom methods of lecture and guided laboratory experiments limiting. This paper presents a methodology that incorporates driving simulation, motion simulation, and educational practices into an engaging, gaming-inspired simulation framework for a vehicle dynamics curriculum. The approach is designed to promote active student participation in authentic engineering experiences that enhance learning about road vehicle dynamics. The paper presents the student use of physical simulation and large-scale visualization to discover the impact that design decisions have on vehicle design using a gaming interface. The approach is evaluated using two experiments incorporated into a sequence of two upper level mechanical engineering courses.

scholarly journals How Momentum Coupling Affects SST Variance and Large-Scale Pacific Climate Variability in CESM

2018 ◽  
Vol 31 (7) ◽  
pp. 2927-2944 ◽  
Author(s):  
Sarah M. Larson ◽  
Daniel J. Vimont ◽  
Amy C. Clement ◽  
Ben P. Kirtman
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Ocean Dynamics ◽  
Easterly Wind ◽  
Tropical Forcing ◽  
Freshwater Fluxes ◽  
The Pacific ◽  
Anomalous Wind ◽  
Momentum Coupling ◽  
The Impact

The contribution of buoyancy (thermal + freshwater fluxes) versus momentum (wind driven) coupling to SST variance in climate models is a longstanding question. Addressing this question has proven difficult because a gap in the model hierarchy exists between the fully coupled (momentum + buoyancy + ocean dynamics) and slab–mixed layer ocean coupled (thermal with no ocean dynamics) versions. The missing piece is a thermally coupled configuration that permits anomalous ocean heat transport convergence decoupled from the anomalous wind stress. A mechanically decoupled model configuration is provided to fill this gap and diagnose the impact of momentum coupling on SST variance in NCAR CESM. A major finding is that subtropical SST variance increases when momentum coupling is disengaged. An “opposing flux hypothesis” may explain why the subtropics (midlatitudes) experience increased (reduced) variance without momentum coupling. In a subtropical easterly wind regime, Ekman fluxes [Formula: see text] oppose thermal fluxes [Formula: see text], such that when the air and sea are mechanically decoupled [Formula: see text], [Formula: see text] variance increases. As a result, SST variance increases. In a midlatitude westerly regime where [Formula: see text] and [Formula: see text] typically reinforce each other, SST variance is reduced. Changes in mean surface winds with climate change could impact the [Formula: see text] and [Formula: see text] covariance relationships. A by-product of mechanically decoupling the model is the absence of ENSO variability. The Pacific decadal oscillation operates without momentum coupling or tropical forcing, although the pattern is modified with enhanced (reduced) variability in the subtropics (midlatitudes). Results show that Ekman fluxes are an important component to tropical, subtropical, and midlatitude SST variance.

scholarly journals The Next-Generation Goddard Convective–Stratiform Heating Algorithm: New Tropical and Warm-Season Retrievals for GPM

2018 ◽  
Vol 31 (15) ◽  
pp. 5997-6026 ◽  
Author(s):  
Stephen E. Lang ◽  
Wei-Kuo Tao
Keyword(s):  
Warm Season ◽  
Tropical Rainfall Measuring Mission ◽  
Shallow Convection ◽  
Heating Rates ◽  
Low Level ◽  
Precipitation Measurement ◽  
Cloud Resolving Model ◽  
Upper Level ◽  
Heating Profiles ◽  
Global Precipitation

The Goddard convective–stratiform heating (CSH) algorithm, used to estimate cloud heating in support of the Tropical Rainfall Measuring Mission (TRMM), is upgraded in support of the Global Precipitation Measurement (GPM) mission. The algorithm’s lookup tables (LUTs) are revised using new and additional cloud-resolving model (CRM) simulations from the Goddard Cumulus Ensemble (GCE) model, producing smoother heating patterns that span a wider range of intensities because of the increased sampling and finer GPM product grid. Low-level stratiform cooling rates are reduced in the land LUTs for a given rain intensity because of the rain evaporation correction in the new four-class ice (4ICE) scheme. Additional criteria, namely, echo-top heights and low-level reflectivity gradients, are tested for the selection of heating profiles. Those resulting LUTs show greater and more precise variation in their depth of heating as well as a tendency for stronger cooling and heating rates when low-level dB Z values decrease toward the surface. Comparisons versus TRMM for a 3-month period show much more low-level heating in the GPM retrievals because of increased detection of shallow convection, while upper-level heating patterns remain similar. The use of echo tops and low-level reflectivity gradients greatly reduces midlevel heating from ~2 to 5 km in the mean GPM heating profile, resulting in a more top-heavy profile like TRMM versus a more bottom-heavy profile with much more midlevel heating. Integrated latent heating rates are much better balanced versus surface rainfall for the GPM retrievals using the additional selection criteria with an overall bias of +4.3%.

scholarly journals Organization of convective ascents in a warm conveyor belt

2020 ◽  
Author(s):  
Nicolas Blanchard ◽  
Florian Pantillon ◽  
Jean-Pierre Chaboureau ◽  
Julien Delanoë
Keyword(s):  
Large Scale ◽  
Doppler Radar ◽  
Heavy Precipitation ◽  
Conveyor Belt ◽  
Isolated Cells ◽  
Low Level ◽  
The North ◽  
Low Level Jet ◽  
Upper Level ◽  
The Impact

Abstract. Warm conveyor belts (WCBs) are warm, moist airstreams of extratropical cyclones leading to widespread clouds and heavy precipitation, where associated diabatic processes can influence midlatitude dynamics. Although WCBs are traditionally seen as continuous slantwise ascents, recent studies have emphasized the presence of embedded convection and the production of mesoscale bands of negative potential vorticity (PV), the impact of which on large-scale dynamics is still debated. Here, detailed cloud and wind measurements obtained with airborne Doppler radar provide unique information on the WCB of the Stalactite cyclone on 2 October 2016 during the North Atlantic Waveguide and Downstream Impact Experiment. The measurements are complemented by a convection-permitting simulation, enabling online Lagrangian trajectories and 3-D objects clustering. The simulation reproduces well the mesoscale structure of the cyclone shown by satellite infrared observations, while the location of trajectories rising by 150 hPa during a relatively short 12 h window matches the WCB region expected from high clouds. One third of those trajectories, categorized as fast ascents, further reach a 100 hPa (2h)−1 threshold during their ascent and follow the cyclonic flow mainly at lower levels. In agreement with radar observations, convective updrafts are found in the WCB and are characterized by moderate reflectivity values up to 20 dBz and vertical velocities above 0.3 m s−1. Updraft objects and fast ascents consistently show three main types of convection in the WCB: (i) frontal convection along the surface cold front and the western edge of the low-level jet; (ii) banded convection at about 2 km altitude along the eastern edge of the low-level jet; (iii) mid-level convection below the upper-level jet. Mesoscale PV dipoles with strong positive and negative values are located in the vicinity of convective ascents and appear to accelerate both low-level and upper-level jets. Both convective ascents and negative PV organize into structures with coherent shape, location and evolution, thus suggesting a dynamical linkage. The results show that convection embedded in WCBs occurs in a coherent and organized manner rather than as isolated cells.

scholarly journals Uncertainty Assessments of Satellite Derived Rainfall Products

2016 ◽  
Author(s):  
Margaret Kimani ◽  
Joost Hoedjes ◽  
Zhongbo Su
Keyword(s):  
Large Scale ◽  
Rainfall Variability ◽  
Tropical Rainfall Measuring Mission ◽  
Global Precipitation Climatology Project ◽  
Rain Gauge ◽  
Climate Data ◽  
Error Distributions ◽  
Precipitation Estimation ◽  
Scatter Plots ◽  
Global Precipitation

Accurate and consistent rainfall observations are vital for climatological studies in support of better planning and decision making. However, estimation of accurate spatial rainfall is limited by sparse rain gauge distributions. Satellite rainfall products can thus potentially play a role in spatial rainfall estimation but their skill and uncertainties need to be under-stood across spatial-time scales. This study aimed at assessing the temporal and spatial performance of seven satellite products (TARCAT (Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT) African Rainfall Climatology And Time series), Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), Tropical Rainfall Measuring Mission (TRMM-3B43), Climate Prediction Center (CPC) Morphing (CMORPH), the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks- Climate Data Record (PERSIANN-CDR), CPC Merged Analysis of Precipitation (CMAP) and Global Precipitation Climatology Project (GPCP) using gridded (0.05o) rainfall data over East Africa for 15 years(1998-2012). The products’ error distributions were qualitatively compared with large scale horizontal winds (850 mb) and elevation patterns with respect to corresponding rain gauge data for each month during the ‘long’ (March-May) and ‘short’ (October-December) rainfall seasons. For validation only rainfall means extracted from 284 rain gauge stations were used, from which qualitative analysis using continuous statistics of Root Mean Squared Difference, Standard deviations, Correlations, coefficient of determinations (from scatter plots) were used to evaluate the products’ performance. Results revealed rainfall variability dependence on wind flows and modulated by topographic influences. The products’ errors showed seasonality and dependent on rainfall intensity and topography. Single sensor and coarse resolution products showed lowest performance on high ground areas. All the products showed low skills in retrieving rainfall during ‘short’ rainfall season when orographic processes were dominant. CHIRPS, CMORPH and TRMM performed well, with TRMM showing the best performance in both seasons. There is need to reduce products’ errors before applications.

scholarly journals Strong Surface Fronts over Sloping Terrain and Coastal Plains

2008 ◽  
Vol 55 ◽  
pp. 35-86 ◽  
Author(s):  
Lance F. Bosart ◽  
Alicia C. Wasula ◽  
Walter H. Drag ◽  
Keith W. Meier
Keyword(s):  
New England ◽  
Large Scale ◽  
Diabatic Heating ◽  
The United States ◽  
Entrance Region ◽  
The Arctic ◽  
Upper Level ◽  
Sloping Terrain ◽  
Low Amplitude ◽  
The Impact

Abstract This paper begins with a review of basic surface frontogenesis concepts with an emphasis on fronts located over sloping terrain adjacent to mountain barriers and fronts located in large-scale baroclinic zones close to coastlines. The impact of cold-air damming and differential diabatic heating and cooling on frontogenesis is considered through two detailed case studies of intense surface fronts. The first case, from 17 to 18 April 2002, featured the westward passage of a cold (side-door) front across coastal eastern New England in which 15°–20°C temperature decreases were observed in less than one hour. The second case, from 28 February to 4 March 1972, featured a long-lived front that affected most of the United States from the Rockies to the Atlantic coast and was noteworthy for a 50°C temperature contrast between Kansas and southern Manitoba, Canada. In the April 2002 case most of New England was initially covered by an unusually warm, dry air mass. Dynamical anticyclogenesis over eastern Canada set the stage for a favorable pressure gradient to allow chilly marine air to approach coastal New England from the east. Diabatic cooling over the chilly (5°–8°C) waters of the Gulf of Maine allowed surface pressures to remain relatively high offshore while diabatic heating over the land (31°–33°C temperatures) enabled surface pressures to fall relative to over the ocean. The resulting higher pressures offshore resulted in an onshore cold push. Frontal intensity was likely enhanced prior to leaf out and grass green-up as virtually all of the available insolation went into sensible heating. The large-scale environment in the February–March 1972 case favored the accumulation of bitterly cold arctic air in Canada. Frontal formation occurred over northern Montana and North Dakota as the arctic air moved slowly southward in conjunction with surface pressure rises east of the Canadian Rockies. The arctic air accelerated southward subsequent to lee cyclogenesis–induced pressure falls ahead of an upstream trough that crossed the Rockies. The southward acceleration of the arctic air was also facilitated by dynamic anticyclogenesis in southern Canada beneath a poleward jet-entrance region. Frontal intensity varied diurnally in response to differential diabatic heating. Three types of cyclogenesis events were observed over the lifetime of the event: 1) low-amplitude frontal waves with no upper-level support, 2) low-amplitude frontal waves that formed in a jet-entrance region, and 3) cyclones that formed ahead of advancing upper-level troughs. All cyclones were either nondeveloping or weak developments despite extreme baroclinicity, likely the result of large atmospheric static stability in the arctic frontal zone and unfavorable alongfront stretching deformation. Significant frontal–mountain interactions were observed over the Rockies and the Appalachians.

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