scholarly journals Shifts in Precipitation Accumulation Extremes During the Warm Season Over the United States

2018 ◽  
Vol 45 (16) ◽  
pp. 8586-8595 ◽  
Author(s):  
Cristian Martinez‐Villalobos ◽  
J. David Neelin
Keyword(s):  
United States ◽  
Warm Season ◽  
The United States

scholarly journals A Radar-Based Climatology of Mesoscale Convective Systems in the United States

2019 ◽  
Vol 32 (5) ◽  
pp. 1591-1606 ◽  
Author(s):  
Alex M. Haberlie ◽  
Walker S. Ashley
Keyword(s):  
United States ◽  
Agricultural Land ◽  
Gulf Coast ◽  
Warm Season ◽  
The United States ◽  
Corn Belt ◽  
High Plains ◽  
Convective System ◽  
Aquifer Recharge ◽  
Mesoscale Convective

Abstract This research applies an automated mesoscale convective system (MCS) segmentation, classification, and tracking approach to composite radar reflectivity mosaic images that cover the contiguous United States (CONUS) and span a relatively long study period of 22 years (1996–2017). These data afford a novel assessment of the seasonal and interannual variability of MCSs. Additionally, hourly precipitation data from 16 of those years (2002–17) are used to systematically examine rainfall associated with radar-derived MCS events. The attributes and occurrence of MCSs that pass over portions of the CONUS east of the Continental Divide (ECONUS), as well as five author-defined subregions—North Plains, High Plains, Corn Belt, Northeast, and Mid-South—are also examined. The results illustrate two preferred regions for MCS activity in the ECONUS: 1) the Mid-South and Gulf Coast and 2) the Central Plains and Midwest. MCS occurrence and MCS rainfall display a marked seasonal cycle, with most of the regions experiencing these events primarily during the warm season (May–August). Additionally, MCS rainfall was responsible for over 50% of annual and seasonal rainfall for many locations in the ECONUS. Of particular importance, the majority of warm-season rainfall for regions with high agricultural land use (Corn Belt) and important aquifer recharge properties (High Plains) is attributable to MCSs. These results reaffirm that MCSs are a significant aspect of the ECONUS hydroclimate.

Comparison of Ground-Based Radar and Geosynchronous Satellite Climatologies of Warm-Season Precipitation over the United States

2008 ◽  
Vol 47 (12) ◽  
pp. 3264-3270 ◽  
Author(s):  
John D. Tuttle ◽  
Richard E. Carbone ◽  
Phillip A. Arkin
Keyword(s):  
United States ◽  
Brightness Temperature ◽  
Satellite Data ◽  
Warm Season ◽  
Propagation Speed ◽  
Radar Data ◽  
The United States ◽  
Temperature Threshold ◽  
Brightness Temperatures ◽  
The Difference

Abstract Studies in the past several years have documented the climatology of warm-season precipitation-episode statistics (propagation speed, span, and duration) over the United States using a national composited radar dataset. These climatological studies have recently been extended to other continents, including Asia, Africa, and Australia. However, continental regions outside the United States have insufficient radar coverage, and the newer studies have had to rely on geostationary satellite data at infrared (IR) frequencies as a proxy for rainfall. It is well known that the use of IR brightness temperatures to infer rainfall is subject to large errors. In this study, the statistics of warm-season precipitation episodes derived from radar and satellite IR measurements over the United States are compared and biases introduced by the satellite data are evaluated. It is found that the satellite span and duration statistics are highly dependent upon the brightness temperature threshold used but with the appropriate choices of thresholds can be brought into good agreement with those based upon radar data. The propagation-speed statistics of satellite events are on average ∼4 m s−1 faster than radar events and are relatively insensitive to the brightness temperature threshold. A simple correction procedure based upon the difference between the steering winds for the precipitation core and the winds at the level of maximum anvil outflow is developed.

scholarly journals The Association of the Elevated Mixed Layer with Significant Severe Weather Events in the Northeastern United States*

2010 ◽  
Vol 25 (4) ◽  
pp. 1082-1102 ◽  
Author(s):  
Peter C. Banacos ◽  
Michael L. Ekster
Keyword(s):  
United States ◽  
Mixed Layer ◽  
Trajectory Analysis ◽  
Source Region ◽  
Warm Season ◽  
The United States ◽  
Severe Weather ◽  
Lapse Rate ◽  
Northeastern United States ◽  
Weather Events

Abstract The occurrence of rare but significant severe weather events associated with elevated mixed-layer (EML) air in the northeastern United States is investigated herein. A total of 447 convective event days with one or more significant severe weather report [where significant is defined as hail 2 in. (5.1 cm) in diameter or greater, a convective gust of 65 kt (33 m s−1) or greater, and/or a tornado of F2 or greater intensity] were identified from 1970 through 2006 during the warm season (1 May–30 September). Of these, 34 event days (7.6%) were associated with identifiable EML air in regional rawinsondes preceding the event. Taken with two other noteworthy events in 1953 and 1969, a total of 36 significant severe weather events associated with EML air were studied via composite and trajectory analysis. Though a small percentage of the total, these 36 events compose a noteworthy list of historically significant derechos and tornadic events to affect the northeastern United States. It is demonstrated that plumes of EML air emanating from the Intermountain West in subsiding, anticyclonically curved flows can reinforce the capping inversion and maintain the integrity of the EML across the central United States over a few days. The EML plume can ultimately become entrained into a moderately fast westerly to northwesterly midtropospheric flow allowing for the plume’s advection into the northeastern United States. Resultant thermodynamic conditions in the convective storm environment are similar to those more typically observed closer to the EML source region in the Great Plains of the United States. In addition to composite and trajectory analysis, two case studies are employed to demonstrate salient and evolutionary aspects of the EML in such events. A lapse rate tendency equation is explored to put EML advection in context with other processes affecting lapse rate.

scholarly journals Ensemble-Based Forecast Uncertainty Analysis of Diverse Heavy Rainfall Events

2010 ◽  
Vol 25 (4) ◽  
pp. 1103-1122 ◽  
Author(s):  
Russ S. Schumacher ◽  
Christopher A. Davis
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Heavy Rainfall ◽  
Warm Season ◽  
The United States ◽  
Forecast Skill ◽  
Ensemble Prediction ◽  
Lead Times ◽  
Cool Season ◽  
Ensemble Prediction System

Abstract This study examines widespread heavy rainfall over 5-day periods in the central and eastern United States. First, a climatology is presented that identifies events in which more than 100 mm of precipitation fell over more than 800 000 km2 in 5 days. This climatology shows that such events are most common in the cool season near the Gulf of Mexico coast and are rare in the warm season. Then, the focus turns to the years 2007 and 2008, when nine such events occurred in the United States, all of them leading to flooding. Three of these were associated with warm-season convection, three took place in the cool season, and three were caused by landfalling tropical cyclones. Global ensemble forecasts from the European Centre for Medium-Range Weather Forecasts Ensemble Prediction System are used to assess forecast skill and uncertainty for these nine events, and to identify the types of weather systems associated with their relative levels of skill and uncertainty. Objective verification metrics and subjective examination are used to determine how far in advance the ensemble identified the threat of widespread heavy rains. Specific conclusions depend on the rainfall threshold and the metric chosen, but, in general, predictive skill was highest for rainfall associated with tropical cyclones and lowest for the warm-season cases. In almost all cases, the ensemble provides very skillful 5-day forecasts when initialized at the beginning of the event. In some of the events—particularly the tropical cyclones and strong baroclinic cyclones—the ensemble still shows considerable skill in 96–216-h precipitation forecasts. In other cases, however, the skill drops off much more rapidly as lead time increases. In particular, forecast skill at long lead times was the lowest and spread was the largest in the two cases associated with meso-α-scale to synoptic-scale vortices that were cut off from the primary upper-level jet. In these cases, it appears that when the vortex is present in the initial conditions, the resulting precipitation forecasts are quite accurate and certain, but at longer lead times when the model is required to both develop and correctly evolve the vortex, forecast quality is low and uncertainty is large. These results motivate further investigation of the events that were poorly predicted.

Characteristics of U.S. Extreme Rain Events during 1999–2003

2006 ◽  
Vol 21 (1) ◽  
pp. 69-85 ◽  
Author(s):  
Russ S. Schumacher ◽  
Richard H. Johnson
Keyword(s):  
United States ◽  
Warm Season ◽  
Mesoscale Convective System ◽  
Organizational Structures ◽  
The United States ◽  
Convective System ◽  
Precipitation Total ◽  
Extreme Rain ◽  
Rain Events ◽  
Reflectivity Data

Abstract This study examines the characteristics of a large number of extreme rain events over the eastern two-thirds of the United States. Over a 5-yr period, 184 events are identified where the 24-h precipitation total at one or more stations exceeds the 50-yr recurrence amount for that location. Over the entire region of study, these events are most common in July. In the northern United States, extreme rain events are confined almost exclusively to the warm season; in the southern part of the country, these events are distributed more evenly throughout the year. National composite radar reflectivity data are used to classify each event as a mesoscale convective system (MCS), a synoptic system, or a tropical system, and then to classify the MCS and synoptic events into subclassifications based on their organizational structures. This analysis shows that 66% of all the events and 74% of the warm-season events are associated with MCSs; nearly all of the cool-season events are caused by storms with strong synoptic forcing. Similarly, nearly all of the extreme rain events in the northern part of the country are caused by MCSs; synoptic and tropical systems play a larger role in the South and East. MCS-related events are found to most commonly begin at around 1800 local standard time (LST), produce their peak rainfall between 2100 and 2300 LST, and dissipate or move out of the affected area by 0300 LST.

The Precipitation Response over the Continental United States to Cold Tropical Pacific Sea Surface Temperatures

2014 ◽  
Vol 27 (13) ◽  
pp. 5036-5055 ◽  
Author(s):  
Hailan Wang ◽  
Siegfried Schubert
Keyword(s):  
United States ◽  
Warm Season ◽  
The United States ◽  
Tropical Pacific ◽  
Eastern United States ◽  
North Atlantic Subtropical High ◽  
Sst Variability ◽  
The Pacific ◽  
Central United States ◽  
Atmospheric Circulation Anomalies

The dominant pattern of SST variability in the Pacific during its cold phase produces pronounced precipitation deficits over the continental United States throughout the annual cycle. This study investigates the observed physical and dynamical processes through which the cold Pacific pattern affects U.S. precipitation, particularly the causes for the peak dry impacts in fall, as well as the nature of the differences between the summer and fall responses. Results show that the peak precipitation deficit over the United States during fall is primarily due to reduced atmospheric moisture transport from the Gulf of Mexico into the central and eastern United States and secondarily a reduction in local evaporation from land–atmosphere feedback. The former is associated with a strong and systematic low-level northeasterly flow anomaly over the southeastern United States that counteracts the northwest branch of the climatological North Atlantic subtropical high. The above northeasterly anomaly is maintained by both diabatic heating anomalies in the nearby intra-American seas and diabatic cooling anomalies in the tropical Pacific. In contrast, the modest summertime precipitation deficit over the central United States is mainly an intensification of the local dry anomaly in the preceding spring from local land–atmosphere feedback; the rather weak and disorganized atmospheric circulation anomalies over and to the south of the United States make little contribution. An evaluation of the NASA Seasonal-to-Interannual Prediction Project (NSIPP-1) AGCM simulations shows it to be deficient in simulating the warm season tropical convection responses over the intra-American seas to the cold Pacific pattern and thereby the precipitation responses over the United States, a problem that appears to be common to many AGCMs.

Listeria Prevalence and Listeria monocytogenes Serovar Diversity at Cull Cow and Bull Processing Plants in the United States†

2007 ◽  
Vol 70 (11) ◽  
pp. 2578-2582 ◽  
Author(s):  
MICHAEL N. GUERINI ◽  
DAYNA M. BRICHTA-HARHAY ◽  
STEVEN D. SHACKELFORD ◽  
TERRANCE M. ARTHUR ◽  
JOSEPH M. BOSILEVAC ◽  
...  
Keyword(s):  
United States ◽  
Listeria Monocytogenes ◽  
Causative Agent ◽  
Warm Season ◽  
The United States ◽  
Prevalence Data ◽  
Beef Processing ◽  
Processing Plants ◽  
Many Sources ◽  
Cull Cow

Listeria monocytogenes, the causative agent of epidemic and sporadic listeriosis, is routinely isolated from many sources, including cattle, yet information on the prevalence of Listeria in beef processing plants in the United States is minimal. From July 2005 through April 2006, four commercial cow and bull processing plants were sampled in the United States to determine the prevalence of Listeria and the serovar diversity of L. monocytogenes. Samples were collected during the summer, fall, winter, and spring. Listeria prevalence on hides was consistently higher during cooler weather (28 to 92% of samples) than during warmer weather (6 and 77% of samples). The Listeria prevalence data collected from preevisceration carcass ranged from undetectable in some warm season samples to as high as 71% during cooler weather. Listeria on postintervention carcasses in the chill cooler was normally undetectable, with the exception of summer and spring samples from one plant where >19% of the carcasses were positive for Listeria. On hides, L. monocytogenes serovar 1/2a was the predominant serovar observed, with serovars 1/2b and 4b present 2.5 times less often and serovar 1/2c not detected on any hides sampled. L. monocytogenes serovars 1/2a, 1/2c, and 4b were found on postintervention carcasses. This prevalence study demonstrates that Listeria species are more prevalent on hides during the winter and spring and that interventions being used in cow and bull processing plants appear to be effective in reducing or eliminating Listeria contamination on carcasses.

Reproductive Biology and Evidence of Diapause in the Cowpea Curculio (Coleoptera: Curculionidae)

2019 ◽  
Vol 113 (2) ◽  
pp. 882-886
Author(s):  
David G Riley ◽  
Sydni Barwick ◽  
Alton N Sparks ◽  
Thomas Harty ◽  
Negin Hamadi
Keyword(s):  
United States ◽  
Insect Pest ◽  
Warm Season ◽  
Adult Emergence ◽  
The United States ◽  
Infested Soil ◽  
Summer Generation ◽  
Growing Seasons ◽  
Historical Distribution ◽  
Larval Emergence

Abstract Chalcodermus aeneus Boheman (Coleoptera: Curculionidae) has been the most destructive insect pest of black-eyed peas or cowpeas, Vigna unguiculata L. (Fabales: Fabaceae), over the last century in the southeastern United States. The historical distribution of this semitropical pest suggests the likelihood that diapause plays a key role in the overwintering success in parts of the United States. However, this report is the first to document biological evidence for diapause in C. aeneus. Our study assessed larval emergence from cowpea pods in the summer to fall growing seasons, egg development in female adults over the first (summer) and second (fall) generations, and adult emergence from infested soil after the first and second generations. There was a clear reduction in larval emergence from summer to fall. Egg and follicle development in female C. aeneus dropped off dramatically by September of each year. There was an extended emergence pattern of weevil adults from the soil in the fall as compared to the summer generation. Any future regional management of cowpea curculio will have to take into account the ability of this insect to diapause, thereby increasing its capacity to overwinter in regions where the cowpea crop, a warm-season, semitropical plant, is terminated with winter freezing temperatures.

Evaluating the Reliability of the U.S. Cooperative Observer Program Precipitation Observations for Extreme Events Analysis Using the LTAR Network

2019 ◽  
Vol 36 (3) ◽  
pp. 317-332
Author(s):  
Eleonora M. C. Demaria ◽  
David C. Goodrich ◽  
Kenneth E. Kunkel
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Daily Precipitation ◽  
Warm Season ◽  
The United States ◽  
Observation Time ◽  
Dense Networks ◽  
Rain Gauges ◽  
Detection And Attribution ◽  
Precipitation Characteristics

AbstractThe detection and attribution of changes in precipitation characteristics relies on dense networks of rain gauges. In the United States, the COOP network is widely used for such studies even though there are reported inconsistencies due to changes in instruments and location, inadequate maintenance, dissimilar observation time, and the fact that measurements are made by a group of dedicated volunteers. Alternately, the Long-Term Agroecosystem Research (LTAR) network has been consistently and professionally measuring precipitation since the early 1930s. The purpose of this study is to compare changes in extreme daily precipitation characteristics during the warm season using paired rain gauges from the LTAR and COOP networks. The comparison, done at 12 LTAR sites located across the United States, shows underestimation and overestimation of daily precipitation totals at the COOP sites compared to the reference LTAR observations. However, the magnitude and direction of the differences are not linked to the underlying precipitation climatology of the sites. Precipitation indices that focus on extreme precipitation characteristics match closely between the two networks at most of the sites. Our results show consistency between the COOP and LTAR networks with precipitation extremes. It also indicates that despite the discrepancies at the daily time steps, the extreme precipitation observed by COOP rain gauges can be reliably used to characterize changes in the hydrologic cycle due to natural and human causes.

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