scholarly journals Convective Episodes in the East-Central United States

2007 ◽  
Vol 135 (11) ◽  
pp. 3707-3727 ◽  
Author(s):  
Matthew D. Parker ◽  
David A. Ahijevych
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Appalachian Mountains ◽  
Vertical Wind Shear ◽  
Radar Data ◽  
Daily Maximum ◽  
Eastern United States ◽  
East Central ◽  
Convective Systems ◽  
Central United States

Abstract Nine years of composited radar data are investigated to assess the presence of organized convective episodes in the east-central United States. In the eastern United States, the afternoon maximum in thunderstorms is ubiquitous over land. However, after removing this principal diurnal peak from the radar data, the presence and motion of organized convective systems becomes apparent in both temporally averaged fields and in the statistics of convective episodes identified by an objective algorithm. Convective echoes are diurnally maximized over the Appalachian chain, and are repeatedly observed to move toward the east. Partly as a result of this, the daily maximum in storms is delayed over the Piedmont and coastal plain relative to the Appalachian Mountains and the Atlantic coast. During the 9 yr studied, the objective algorithm identified 2128 total convective episodes (236 yr−1), with several recurring behaviors. Many systems developed over the elevated terrain during the afternoon and moved eastward, often to the coastline and even offshore. In addition, numerous systems formed to the west of the Appalachian Mountains and moved into and across the eastern U.S. study domain. In particular, many nocturnal convective systems from the central United States entered the western side of the study domain, frequently arriving at the eastern mountains around the next day’s afternoon maximum in storm frequency. A fraction of such well-timed systems succeeded in crossing the Appalachians and continuing across the Piedmont and coastal plain. Convective episodes were most frequent during the high-instability, low-shear months of summer, which dominate the year-round statistics. Even so, an important result is that the episodes still occurred almost exclusively in above-average vertical wind shear. Despite the overall dominance of the diurnal cycle, the data show that adequate shear in the region frequently leads to long-lived convective episodes with mesoscale organization.

Carabodes of the eastern United States and adjacent Canada (Acari: Oribatida: Carabodidae)

1992 ◽  
Vol 70 (10) ◽  
pp. 2042-2058 ◽  
Author(s):  
R. Marcel Reeves
Keyword(s):  
United States ◽  
North America ◽  
Coastal Plain ◽  
Forest Floor ◽  
Appalachian Mountains ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Eastern United States ◽  
Thelytokous Parthenogenesis ◽  
Atlantic Coastal

Adults of four new species of Carabodes, C. chandleri, C. erectus, C. interruptus, and C. pentasetosus, and the immatures of C. erectus, are described. All have been collected from a variety of forest-floor habitats, with C. chandleri, C. interruptus, and C. pentasetosus more common in leaf litter, and C. erectus preferring polyporous fungi. All four species are widely distributed in eastern North America, with C. chandleri, C. erectus, and C. interruptus more abundant in samples from the Appalachian Mountains and C. pentasetosus in those from the Atlantic coastal plain. Thelytokous parthenogenesis is suspected to occur in C. pentasetosus n.sp. and Carabodes granulatus Banks. A key to the 19 species of Carabodes found in North America is provided.

NAM Model Forecasts of Warm-Season Quasi-Stationary Frontal Environments in the Central United States

2010 ◽  
Vol 25 (4) ◽  
pp. 1281-1292 ◽  
Author(s):  
Shih-Yu Wang ◽  
Adam J. Clark
Keyword(s):  
United States ◽  
Mesoscale Model ◽  
Convective Available Potential Energy ◽  
Warm Season ◽  
Correlation Coefficients ◽  
Precipitable Water ◽  
Wind Fields ◽  
Vapor Flux ◽  
Convective Systems ◽  
Central United States

Abstract Using a composite procedure, North American Mesoscale Model (NAM) forecast and observed environments associated with zonally oriented, quasi-stationary surface fronts for 64 cases during July–August 2006–08 were examined for a large region encompassing the central United States. NAM adequately simulated the general synoptic features associated with the frontal environments (e.g., patterns in the low-level wind fields) as well as the positions of the fronts. However, kinematic fields important to frontogenesis such as horizontal deformation and convergence were overpredicted. Surface-based convective available potential energy (CAPE) and precipitable water were also overpredicted, which was likely related to the overprediction of the kinematic fields through convergence of water vapor flux. In addition, a spurious coherence between forecast deformation and precipitation was found using spatial correlation coefficients. Composite precipitation forecasts featured a broad area of rainfall stretched parallel to the composite front, whereas the composite observed precipitation covered a smaller area and had a WNW–ESE orientation relative to the front, consistent with mesoscale convective systems (MCSs) propagating at a slight right angle relative to the thermal gradient. Thus, deficiencies in the NAM precipitation forecasts may at least partially result from the inability to depict MCSs properly. It was observed that errors in the precipitation forecasts appeared to lag those of the kinematic fields, and so it seems likely that deficiencies in the precipitation forecasts are related to the overprediction of the kinematic fields such as deformation. However, no attempts were made to establish whether the overpredicted kinematic fields actually contributed to the errors in the precipitation forecasts or whether the overpredicted kinematic fields were simply an artifact of the precipitation errors. Regardless of the relationship between such errors, recognition of typical warm-season environments associated with these errors should be useful to operational forecasters.

Evaluation of Intensity Prediction Equations (IPEs) for Small-Magnitude Earthquakes

2021 ◽  
Author(s):  
Ganyu Teng ◽  
Jack W. Baker ◽  
David J. Wald
Keyword(s):  
United States ◽  
Ground Truth ◽  
Site Amplification ◽  
Eastern United States ◽  
Prediction Equations ◽  
Small Magnitude ◽  
Intensity Prediction ◽  
Central United States ◽  
Hazard Disaggregation

Abstract This study assesses existing intensity prediction equations (IPEs) for small unspecified magnitude (M ≤3.5) earthquakes at short hypocentral distances (Dh) and explores such earthquakes’ contribution to the felt shaking hazard. In particular, we consider IPEs by Atkinson and Wald (2007) and Atkinson et al. (2014), and evaluate their performance based on “Did You Feel It” (DYFI) reports and recorded peak ground velocities (PGVs) in the central United States. Both IPEs were developed based on DYFI reports in the central and eastern United States with moment magnitudes above Mw 3.0. DYFI reports are often used as the ground truth when evaluating and developing IPEs, but they could be less reliable when there are limited responses for small-magnitude earthquakes. We first compare the DYFI reports with intensities interpolated from recorded PGVs. Results suggest a minimal discrepancy between the two when the intensity is large enough to be felt (i.e., M >2 and Dh<15  km). We then compare intensities from 31,617 DYFI reports of 3049 earthquakes with the two IPEs. Results suggest that both the IPEs match well with observed intensities for 2.0< M <3.0 and Dh<10  km, but the IPE by Atkinson et al. (2014) matches better for larger distances. We also observe that intensities from DYFI reports attenuate faster compared with the two IPEs, especially for distances greater than 10 km. We then group DYFI reports by inferred VS30 as a proxy for site amplification effects. We observe that intensities at sites with VS30 around 300 m/s are consistently higher than at sites with VS30 around 700 m/s and are also closer to the two IPEs. Finally, we conduct hazard disaggregation for earthquakes at close distances (Dh=7.5  km) using the observed records. Results suggest that earthquakes with magnitudes below M 3.0 contribute more than 40% to the occurrence of felt shaking.

A 7,290-Year-Old Bottle Gourd from the Windover Site, Florida

1990 ◽  
Vol 55 (2) ◽  
pp. 354-360 ◽  
Author(s):  
Glen H. Doran ◽  
David N. Dickel ◽  
Lee A. Newsom
Keyword(s):  
United States ◽  
Organic Materials ◽  
Bottle Gourd ◽  
Lagenaria Siceraria ◽  
Eastern United States ◽  
East Central ◽  
Central Florida

A bottle gourd (Lagenaria siceraria) recovered from a burial context at the Windover site (8 BR246) in east-central Florida has been dated directly to 7,290 ± 120 radiocarbon years B.P. This provides the earliest documentation of bottle gourds north of Mexico and demonstrates approximate contemporaneity with other eastern United States Cucurbitacae. Investigations of wet sites such as Windover, while requiring substantially greater consideration of conservation than in typical dry sites, greatly expands the recovery of organic materials enabling broader insights to prehistoric processes.

scholarly journals Can the GPM IMERG Final Product Accurately Represent MCSs’ Precipitation Characteristics over the Central and Eastern United States?

2020 ◽  
Vol 21 (1) ◽  
pp. 39-57 ◽  
Author(s):  
Wenjun Cui ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Zhe Feng ◽  
Jiwen Fan
Keyword(s):  
United States ◽  
False Alarm ◽  
Stage Iv ◽  
Cloud Base ◽  
Eastern United States ◽  
Convective Systems ◽  
Precipitation Measurement ◽  
Precipitation Characteristics ◽  
Mesoscale Convective ◽  
Global Precipitation

AbstractMesoscale convective systems (MCSs) play an important role in water and energy cycles as they produce heavy rainfall and modify the radiative profile in the tropics and midlatitudes. An accurate representation of MCSs’ rainfall is therefore crucial in understanding their impact on the climate system. The V06B Integrated Multisatellite Retrievals from Global Precipitation Measurement (IMERG) half-hourly precipitation final product is a useful tool to study the precipitation characteristics of MCSs because of its global coverage and fine spatiotemporal resolutions. However, errors and uncertainties in IMERG should be quantified before applying it to hydrology and climate applications. This study evaluates IMERG performance on capturing and detecting MCSs’ precipitation in the central and eastern United States during a 3-yr study period against the radar-based Stage IV product. The tracked MCSs are divided into four seasons and are analyzed separately for both datasets. IMERG shows a wet bias in total precipitation but a dry bias in hourly mean precipitation during all seasons due to the false classification of nonprecipitating pixels as precipitating. These false alarm events are possibly caused by evaporation under the cloud base or the misrepresentation of MCS cold anvil regions as precipitating clouds by the algorithm. IMERG agrees reasonably well with Stage IV in terms of the seasonal spatial distribution and diurnal cycle of MCSs precipitation. A relative humidity (RH)-based correction has been applied to the IMERG precipitation product, which helps reduce the number of false alarm pixels and improves the overall performance of IMERG with respect to Stage IV.

scholarly journals Forecasting the Maintenance of Mesoscale Convective Systems Crossing the Appalachian Mountains

2010 ◽  
Vol 25 (4) ◽  
pp. 1179-1195 ◽  
Author(s):  
Casey E. Letkewicz ◽  
Matthew D. Parker
Keyword(s):  
Appalachian Mountains ◽  
Severe Weather ◽  
Mesoscale Convective Systems ◽  
Radiosonde Data ◽  
Eastern United States ◽  
Unique Problem ◽  
Convective Systems ◽  
Barrier Analysis ◽  
Mesoscale Convective ◽  
The Mean

Abstract Forecasting the maintenance of mesoscale convective systems (MCSs) is a unique problem in the eastern United States due to the influence of the Appalachian Mountains. At times these systems are able to traverse the terrain and produce severe weather in the lee, while at other times they instead dissipate upon encountering the mountains. To differentiate between crossing and noncrossing MCS environments, 20 crossing and 20 noncrossing MCS cases were examined. The cases were largely similar in terms of their 500-hPa patterns, MCS archetypes, and orientations with respect to the barrier. Analysis of radiosonde data, however, revealed that the environment east of the mountains discriminated between case types very well. The thermodynamic and kinematic variables that had the most discriminatory power included those associated with instability, several different bulk shear vector magnitudes, and also the mean tropospheric wind. Crossing cases were characterized by higher instability, which was found to be partially attributable to the diurnal cycle. However, these cases also tended to occur in environments with weaker shear and a smaller mean wind. The potential reasons for these results, and their forecasting implications, are discussed.

scholarly journals Survival of Cercospora sojina on Soybean Leaf Debris in Illinois

2014 ◽  
Vol 15 (3) ◽  
pp. 92-96 ◽  
Author(s):  
Guirong Zhang ◽  
Carl A. Bradley
Keyword(s):  
United States ◽  
Southern Illinois ◽  
Cercospora Sojina ◽  
North Central ◽  
East Central ◽  
The North ◽  
Central United States ◽  
Soybean Leaf ◽  
Soybean Leaves ◽  
Central Illinois

Historically, frogeye leaf spot (FLS, caused by Cercospora sojina) of soybean has been observed more frequently in the southern United States than the north-central United States. However, in recent years, FLS field observations have increased in the north-central United States. To better understand the survival rate of C. sojina in Illinois, a field study was conducted at three locations: Monmouth (west-central Illinois), Urbana (east-central Illinois), and Dixon Springs (southeastern Illinois). At each location, soybean leaves affected by FLS were placed at depths of 0, 10, and 20 cm and retrieved at different durations up to 24 months. To determine the viability of C. sojina in the collected leaves, a greenhouse bioassay was used. Survival of C. sojina declined equally with time at all three locations through 19 months. After 24 months, C. sojina from leaves that had been placed at Monmouth and Urbana were no longer viable, whereas leaves that had been placed at Dixon Springs produced viable inoculum. Depth of leaf placement had no effect on survival of C. sojina at any of the locations. These results suggest that planting a nonhost crop for two years in central Illinois will reduce levels of C. sojina inoculum to a negligible amount; however, soybean farmers in southern Illinois may need a longer rotation for FLS management. Accepted 10 May 2014. Published 23 July 2014.

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