Propagation of Convective Systems Associated with Early Morning Precipitation and Different Northerly Background Winds over Western Java

ABSTRACT The diurnal cycle of precipitation and thermodynamic profiles over western Colombia are examined in new GPM satellite rainfall products, first-ever research balloon launches during 2016 over both sea and land, and numerical simulations with the Weather Research and Forecasting (WRF) Model. This paper evaluates the Mapes et al. mechanism for midnight–early morning coastal convection that propagates offshore: reduction of inhibition in the crests of lower-tropospheric internal waves. Shipborne balloon launches confirm the evening development of such inhibition by a warm overhang in saturation moist static energy (SMSE) near 700–800 hPa. This feature relaxes overnight, consistent with the disinhibition hypothesis for early morning rains. Over the coastal plain, soundings also show late afternoon increases in near-surface MSE large enough to predominate over the overhang’s inhibition effect, driving a second peak in the rainfall diurnal cycle. Parameterized convection simulations fail to simulate the observed coastal rainfall. Still, during a November 2016 wet spell, a cloud-permitting one-way nested 4 km simulation performs better, simulating morning coastal rainfall. In that simulation, however, early morning cooling in the 700–800 hPa layer appears mainly as a standing signal resembling the local radiative effect rather than as a propagating wave. We consider the additional hypothesis that the offshore propagation of that morning convection could involve advection or wind shear effects on organized convective systems. Strong easterlies at mountaintop level were indeed simulated, but that is one of the model’s strongest biases, so the mechanisms of the model’s partial success in simulating diurnal rainfall remain ambiguous.

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Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-14249-2016 ◽

2016 ◽

Vol 16 (22) ◽

pp. 14249-14264 ◽

Cited By ~ 16

Author(s):

Shuaiqi Tang ◽

Shaocheng Xie ◽

Yunyan Zhang ◽

Minghua Zhang ◽

Courtney Schumacher ◽

...

Keyword(s):

Vertical Velocity ◽

Large Scale ◽

Early Morning ◽

Dry Season ◽

Diurnal Variations ◽

Wet Season ◽

Convective Systems ◽

Heating Source ◽

Seasonal And Diurnal Variations ◽

Eddy Fluxes

Abstract. This study describes the characteristics of large-scale vertical velocity, apparent heating source (Q1) and apparent moisture sink (Q2) profiles associated with seasonal and diurnal variations of convective systems observed during the two intensive operational periods (IOPs) that were conducted from 15 February to 26 March 2014 (wet season) and from 1 September to 10 October 2014 (dry season) near Manaus, Brazil, during the Green Ocean Amazon (GoAmazon2014/5) experiment. The derived large-scale fields have large diurnal variations according to convective activity in the GoAmazon region and the morning profiles show distinct differences between the dry and wet seasons. In the wet season, propagating convective systems originating far from the GoAmazon region are often seen in the early morning, while in the dry season they are rarely observed. Afternoon convective systems due to solar heating are frequently seen in both seasons. Accordingly, in the morning, there is strong upward motion and associated heating and drying throughout the entire troposphere in the wet season, which is limited to lower levels in the dry season. In the afternoon, both seasons exhibit weak heating and strong moistening in the boundary layer related to the vertical convergence of eddy fluxes. A set of case studies of three typical types of convective systems occurring in Amazonia – i.e., locally occurring systems, coastal-occurring systems and basin-occurring systems – is also conducted to investigate the variability of the large-scale environment with different types of convective systems.

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Large-Scale Vertical Velocity, Diabatic Heating and Drying Profiles Associated with Seasonal and Diurnal Variations of Convective Systems Observed in the GoAmazon2014/5 Experiment

10.5194/acp-2016-644 ◽

2016 ◽

Author(s):

Shuaiqi Tang ◽

Shaocheng Xie ◽

Yunyan Zhang ◽

Minghua Zhang ◽

Courtney Schumacher ◽

...

Keyword(s):

Vertical Velocity ◽

Large Scale ◽

Early Morning ◽

Dry Season ◽

Diurnal Variations ◽

Wet Season ◽

Convective Systems ◽

Heating Source ◽

Seasonal And Diurnal Variations ◽

Eddy Fluxes

Abstract. This study describes the characteristics of large-scale vertical velocity, apparent heating source (Q1) and apparent moisture sink (Q2) profiles associated with seasonal and diurnal variations of convective systems observed during the two intensive operational periods (IOPs) of the Green Ocean Amazon (GoAmazon2014/5) experiment, which was conducted near Manaus, Brazil in 2014 and 2015. The derived large-scale fields have large diurnal variations according to convective activity in the GoAmazon region and the morning profiles show distinct differences between the dry and wet seasons. In the wet season, propagating convective systems originating far from the GoAmazon region are often seen in the early morning, while in the dry season, they are rarely observed. Afternoon convective systems due to solar heating are frequently seen in both seasons. Accordingly, in the morning, there is strong upward motion and associated heating and drying throughout the entire troposphere in the wet season, which is limited to lower levels in the dry season. In the afternoon, both seasons exhibit weak heating and strong moistening in the boundary layer related to the vertical convergence of eddy fluxes. A set of case studies of three typical types of convective systems occurring in Amazonia – i.e., locally-occurring systems, coastal-occurring systems and basin-occurring systems – is also conducted to investigate the variability of the large-scale environment with different types of convective systems.

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The Diurnal and Microphysical Characteristics of MJO Rain Events during DYNAMO

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0316.1 ◽

2019 ◽

Vol 2019 (1) ◽

pp. 67-80 ◽

Cited By ~ 1

Author(s):

Angela K. Rowe ◽

Robert A. Houze ◽

Stacy Brodzik ◽

Manuel D. Zuluaga

Keyword(s):

Deep Convection ◽

Intraseasonal Variability ◽

Early Morning ◽

Synoptic Scale ◽

Convective Systems ◽

Mesoscale Convective ◽

The Mean ◽

Microphysical Processes ◽

Rain Events ◽

Afternoon Peak

Abstract The Madden–Julian oscillation (MJO) dominates the intraseasonal variability of cloud populations of the tropical Indian and Pacific Oceans. Suppressed MJO periods consist primarily of shallow and isolated deep convection. During the transition to an active MJO, the shallow and isolated deep clouds grow upscale into the overnight hours. During active MJO periods, mesoscale convective systems occur mostly during 2–4-day bursts of rainfall activity with a statistically significant early morning peak. Yet when these rain events are separated into individual active periods, some periods do not follow the mean pattern, with the November events in particular exhibiting an afternoon peak. The radar-observed microphysical processes producing the precipitation during the major rain events of active MJO periods evolve in connection with synoptic-scale wave passages with varying influences of diurnal forcing. MJO studies that do not account for the intermittency of rainfall during active MJO phases through averaging over multiple events can lead to the misimpression that the primary rain-producing clouds of the MJO are modulated solely by the diurnal cycle.

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The Diurnal Cycle of Rainfall and Convective Intensity according to Three Years of TRMM Measurements

Journal of Climate ◽

10.1175/1520-0442-16.10.1456 ◽

2003 ◽

Vol 16 (10) ◽

pp. 1456-1475 ◽

Cited By ~ 463

Author(s):

Stephen W. Nesbitt ◽

Edward J. Zipser

Keyword(s):

Diurnal Cycle ◽

Tropical Rainfall Measuring Mission ◽

Early Morning ◽

Convective Systems ◽

Rain Gauges ◽

Mesoscale Convective ◽

Late Evening ◽

Microwave Imager ◽

Trmm Microwave Imager ◽

Rain Rates

Abstract The Tropical Rainfall Measuring Mission (TRMM) satellite measurements from the precipitation radar and TRMM microwave imager have been combined to yield a comprehensive 3-yr database of precipitation features (PFs) throughout the global Tropics (±36° latitude). The PFs retrieved using this algorithm (which number nearly six million Tropicswide) have been sorted by size and intensity ranging from small shallow features greater than 75 km2 in area to large mesoscale convective systems (MCSs) according to their radar and ice scattering characteristics. This study presents a comprehensive analysis of the diurnal cycle of the observed precipitation features' rainfall amount, precipitation feature frequency, rainfall intensity, convective–stratiform rainfall portioning, and remotely sensed convective intensity, sampled Tropicswide from space. The observations are sorted regionally to examine the stark differences in the diurnal cycle of rainfall and convective intensity over land and ocean areas. Over the oceans, the diurnal cycle of rainfall has small amplitude, with the maximum contribution to rainfall coming from MCSs in the early morning. This increased contribution is due to an increased number of MCSs in the nighttime hours, not increasing MCS areas or conditional rain rates, in agreement with previous works. Rainfall from sub-MCS features over the ocean has little appreciable diurnal cycle of rainfall or convective intensity. Land areas have a much larger rainfall cycle than over the ocean, with a marked minimum in the midmorning hours and a maximum in the afternoon, slowly decreasing through midnight. Non-MCS features have a significant peak in afternoon instantaneous conditional rain rates (the mean rain rate in raining pixels), and convective intensities, which differs from previous studies using rain rates derived from hourly rain gauges. This is attributed to enhancement by afternoon heating. MCSs over land have a convective intensity peak in the late afternoon, however all land regions have MCS rainfall peaks that occur in the late evening through midnight due to their longer life cycle. The diurnal cycle of overland MCS rainfall and convective intensity varies significantly among land regions, attributed to MCS sensitivity to the varying environmental conditions in which they occur.

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Tornadoes from Squall Lines and Bow Echoes. Part I: Climatological Distribution

Weather and Forecasting ◽

10.1175/waf-835.1 ◽

2005 ◽

Vol 20 (1) ◽

pp. 23-34 ◽

Cited By ~ 102

Author(s):

Robert J. Trapp ◽

Sarah A. Tessendorf ◽

Elaine Savageau Godfrey ◽

Harold E. Brooks

Keyword(s):

United States ◽

Tropical Cyclones ◽

Early Morning ◽

Time Of Day ◽

Primary Objective ◽

Radar Reflectivity ◽

Convective Systems ◽

Late Night ◽

Squall Lines ◽

Tornado Event

Abstract The primary objective of this study was to estimate the percentage of U.S. tornadoes that are spawned annually by squall lines and bow echoes, or quasi-linear convective systems (QLCSs). This was achieved by examining radar reflectivity images for every tornado event recorded during 1998–2000 in the contiguous United States. Based on these images, the type of storm associated with each tornado was classified as cell, QLCS, or other. Of the 3828 tornadoes in the database, 79% were produced by cells, 18% were produced by QLCSs, and the remaining 3% were produced by other storm types, primarily rainbands of landfallen tropical cyclones. Geographically, these percentages as well as those based on tornado days exhibited wide variations. For example, 50% of the tornado days in Indiana were associated with QLCSs. In an examination of other tornado attributes, statistically more weak (F1) and fewer strong (F2–F3) tornadoes were associated with QLCSs than with cells. QLCS tornadoes were more probable during the winter months than were cells. And finally, QLCS tornadoes displayed a comparatively higher and statistically significant tendency to occur during the late night/early morning hours. Further analysis revealed a disproportional decrease in F0–F1 events during this time of day, which led the authors to propose that many (perhaps as many as 12% of the total) weak QLCSs tornadoes were not reported.

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Elucidating the Life Cycle of Warm-Season Mesoscale Convective Systems in Eastern China from the Himawari-8 Geostationary Satellite

Remote Sensing ◽

10.3390/rs12142307 ◽

2020 ◽

Vol 12 (14) ◽

pp. 2307

Author(s):

Dandan Chen ◽

Jianping Guo ◽

Dan Yao ◽

Zhe Feng ◽

Yanluan Lin

Keyword(s):

Life Cycle ◽

Large Scale ◽

Eastern China ◽

Warm Season ◽

Northern China ◽

Early Morning ◽

Geostationary Satellite ◽

Mesoscale Convective Systems ◽

Convective Systems ◽

Mesoscale Convective

The life cycle of mesoscale convective systems (MCSs) in eastern China is yet to be fully understood, mainly due to the lack of observations of high spatio-temporal resolution and objective methods. Here, we quantitatively analyze the properties of warm-season (from April to September of 2016) MCSs during their lifetimes using the Himawari-8 geostationary satellite, combined with ground-based radars and gauge measurements. Generally, the occurrence of satellite derived MCSs has a noon peak over the land and an early morning peak over the ocean, which is several hours earlier than the precipitation peak. The developing and dissipative stages are significantly longer as total durations of MCSs increase. Aided by three-dimensional radar mosaics, we find the fraction of convective cores over northern China is much lower when compared with those in central United States, indicating that the precipitation produced by broad stratiform clouds may be more important for northern China. When there exists a large amount of stratiform precipitation, it releases a large amount of latent heat and promotes the large-scale circulations, which favors the maintenance of MCSs. These findings provide quantitative results about the life cycle of warm-season MCSs in eastern China based on multiple data sources and large numbers of samples.

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Total Lightning Characteristics Relative to Radar and Satellite Observations of Oklahoma Mesoscale Convective Systems

Monthly Weather Review ◽

10.1175/mwr-d-11-00268.1 ◽

2013 ◽

Vol 141 (5) ◽

pp. 1593-1611 ◽

Cited By ~ 13

Author(s):

Jeffrey A. Makowski ◽

Donald R. MacGorman ◽

Michael I. Biggerstaff ◽

William H. Beasley

Keyword(s):

Early Morning ◽

Mesoscale Convective Systems ◽

Very High Frequency ◽

Maximum Area ◽

Convective Systems ◽

Lightning Detection ◽

Mesoscale Convective ◽

Total Lightning ◽

Cloud Tops ◽

Mapping Arrays

Abstract The advent of regional very high frequency (VHF) Lightning Mapping Arrays (LMAs) makes it possible to begin analyzing trends in total lightning characteristics in ensembles of mesoscale convective systems (MCSs). Flash initiations observed by the Oklahoma LMA and ground strikes observed by the National Lightning Detection Network were surveyed relative to infrared satellite and base-scan radar reflectivity imagery for 30 mesoscale convective systems occurring over a 7-yr period. Total lightning data were available for only part of the life cycle of most MCSs, but well-defined peaks in flash rates were usually observed for MCSs having longer periods of data. The mean of the maximum 10-min flash rates for the ensemble of MCSs was 203 min−1 for total flashes and 41 min−1 for cloud-to-ground flashes (CGs). In total, 21% of flashes were CGs and 13% of CGs lowered positive charge to ground. MCSs with the largest maximum flash rates entered Oklahoma in the evening before midnight. All three MCSs entering Oklahoma in early morning after sunrise had among the smallest maximum flash rates. Flash initiations were concentrated in or near regions of larger reflectivity and colder cloud tops. The CG flash rates and total flash rates frequently evolved similarly, although the fraction of flashes striking ground usually increased as an MCS decayed. Total flash rates tended to peak approximately 90 min before the maximum area of the −52°C cloud shield, but closer in time to the maximum area of colder cloud shields. MCSs whose −52°C cloud shield grew faster tended to have larger flash rates.

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Characteristics of Precipitating Convective Systems in the Premonsoon Season of South Asia

Journal of Hydrometeorology ◽

10.1175/2010jhm1311.1 ◽

2011 ◽

Vol 12 (2) ◽

pp. 157-180 ◽

Cited By ~ 52

Author(s):

Ulrike Romatschke ◽

Robert A. Houze

Keyword(s):

South Asia ◽

Tropical Rainfall Measuring Mission ◽

Maximum Size ◽

Early Morning ◽

Mountain Ranges ◽

Convective Systems ◽

Diurnal Cycles ◽

Synoptic Forcing ◽

Trmm Precipitation ◽

Downslope Flow

Abstract Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data obtained over South Asia during eight premonsoon seasons (March–May) show that the precipitation is more convective in nature and more sensitive to synoptic forcing than during the monsoon. Over land areas, most rain falls from medium-sized systems (8500–35 000 km2 in horizontal area). In continental regions near the Himalayas, these medium-sized systems are favored by 500-mb trough conditions and are of two main types: 1) systems triggered by daytime heating over high terrain and growing to reach maximum size a few hours later and 2) systems triggered at night, as moist upstream flow is lifted over cold downslope flow from the mountains, and reaching maximum development upstream of the central and eastern Himalayas in the early morning hours. Systems triggered by similar mechanisms also account for the precipitation maxima in mountainous coastal regions, where the diurnal cycles are dominated by systems triggered in daytime over the higher coastal terrain. Medium-sized nocturnal systems are also found upstream of coastal mountain ranges. West-coastal precipitation systems over India and Myanmar are favored when low pressure systems occur over the upstream oceans, whereas Indian east-coastal systems occur when high pressure dominates over Bangladesh. Over the Bay of Bengal, the dominant systems are larger (>35 000 km2), and have large stratiform components. They occur in connection with depressions over the Bay and exhibit a weaker diurnal cycle.

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Radar-Observed Characteristics of Precipitating Systems during NAME 2004

Journal of Climate ◽

10.1175/jcli4082.1 ◽

2007 ◽

Vol 20 (9) ◽

pp. 1713-1733 ◽

Cited By ~ 59

Author(s):

Timothy J. Lang ◽

David A. Ahijevych ◽

Stephen W. Nesbitt ◽

Richard E. Carbone ◽

Steven A. Rutledge ◽

...

Keyword(s):

Gulf Of California ◽

Early Morning ◽

Reanalysis Data ◽

North American Monsoon ◽

Minor Role ◽

Small Subset ◽

Easterly Waves ◽

Convective Systems ◽

Precipitation Regimes ◽

Mesoscale Convective

Abstract A multiradar network, operated in the southern Gulf of California (GoC) region during the 2004 North American Monsoon Experiment, is used to analyze the spatial and temporal variabilities of local precipitation. Based on the initial findings of this analysis, it is found that terrain played a key role in this variability, as the diurnal cycle was dominated by convective triggering during the afternoon over the peaks and foothills of the Sierra Madre Occidental (SMO). Precipitating systems grew upscale and moved WNW toward the gulf. Distinct precipitation regimes within the monsoon are identified. The first, regime A, corresponded to enhanced precipitation over the southern portions of the coast and GoC, typically during the overnight and early morning hours. This was due to precipitating systems surviving the westward trip (∼7 m s−1; 3–4 m s−1 in excess of steering winds) from the SMO after sunset, likely because of enhanced environmental wind shear as diagnosed from local soundings. The second, regime B, corresponded to the significant northward/along-coast movement of systems (∼10 m s−1; 4–5 m s−1 in excess of steering winds) and often overlapped with regime A. The weak propagation is explainable by shallow–weak cold pools. Reanalysis data suggest that tropical easterly waves were associated with the occurrence of disturbed regimes. Gulf surges occurred during a small subset of these regimes, so they played a minor role during 2004. Mesoscale convective systems and other organized systems were responsible for most of the rainfall in this region, particularly during the disturbed regimes.

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