scholarly journals Verification of Extratropical Cyclones within the NCEP Operational Models. Part I: Analysis Errors and Short-Term NAM and GFS Forecasts

2009 ◽  
Vol 24 (5) ◽  
pp. 1173-1190 ◽  
Author(s):  
Michael E. Charles ◽  
Brian A. Colle
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
Eastern Pacific ◽  
Extratropical Cyclones ◽  
Global Forecast System ◽  
Eastern United States ◽  
Forecast System ◽  
Short Term ◽  
The North

Abstract This paper verifies extratropical cyclones around North America and the adjacent oceans within the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) and North American Mesoscale (NAM) models during the 2002–07 cool seasons (October–March). The analyzed cyclones in the Global Forecast System (GFS) model, North American Mesoscale (NAM) model, and the North American Regional Reanalysis (NARR) were also compared against sea level pressure (SLP) observations around extratropical cyclones. The GFS analysis of SLP was clearly superior to the NAM and NARR analyses. The analyzed cyclone pressures in the NAM improved in 2006–07 when its data assimilation was switched to the Gridpoint Statistical Interpolation (GSI). The NCEP GFS has more skillful cyclone intensity and position forecasts than the NAM over the continental United States and adjacent oceans, especially over the eastern Pacific, where the NAM has a large positive (underdeepening) bias in cyclone central pressure. For the short-term (0–60 h) forecasts, the GFS and NAM cyclone errors over the eastern Pacific are larger than the other regions to the east. There are relatively large biases in cyclone position for both models, which vary spatially around North America. The eastern Pacific has four to eight cyclone events per year on average, with errors >10 mb at hour 48 in the GFS; this number has not decreased in recent years. There has been little improvement in the 0–2-day cyclone forecasts during the past 5 yr over the eastern United States, while there has been a relatively large improvement in the cyclone pressure predictions over the eastern Pacific in the NAM.

scholarly journals Spatial Distribution and Evolution of Extratropical Cyclone Errors over North America and its Adjacent Oceans in the NCEP Global Forecast System Model

2011 ◽  
Vol 26 (2) ◽  
pp. 129-149 ◽  
Author(s):  
Brian A. Colle ◽  
Michael E. Charles
Keyword(s):  
United States ◽  
North America ◽  
East Coast ◽  
Eastern Pacific ◽  
Central Pressure ◽  
Global Forecast System ◽  
Eastern United States ◽  
Forecast System ◽  
Western Atlantic ◽  
The U.S

Abstract Short- to medium-range (1–5 day) forecasts of extratropical cyclones around North America and its adjacent oceans are verified within the Global Forecast System (GFS) model at the National Centers for Environmental Prediction (NCEP) during the 2002–07 cool seasons (October–March). Cyclones in the immediate lee of the Rockies and U.S. Great Plains have 25%–50% smaller pressure errors than other regions after hour 36. The central pressure and displacement errors are largest over the central and eastern Pacific for the 42–72-h forecast, while the western and central Atlantic pressure errors for 96–120 h are similar to the central and eastern Pacific. For relatively strong cyclones, the western Atlantic and central/eastern Canada pressure errors are larger than those for the Pacific by 108–120 h. There are large spatial variations in the central pressure biases at 72–120 h, with overdeepened GFS cyclones (negative errors) extending from the northern Pacific and Bering Strait eastward to western Canada, while underdeepened GFS cyclones (positive errors) occur across northeast Canada and just east of the U.S. east coast. GFS cyclone tracks and spatial composites using the daily NCEP reanalysis are used to illustrate flow patterns and source regions for some of the large GFS cyclone errors and biases. Relatively large central pressure errors over the central Pacific early in the forecast (30 h) spread eastward over Canada by 66 h and the eastern United States by 84 h. The underdeepened GFS cyclone errors (>1.5 standard deviations) at day 4 over the western Atlantic are associated with an anomalous ridge over the western United States and trough over the eastern United States, and most of the underdeepening occurs with cyclones tracking east-northeastward across the Gulf Stream. Many of the overdeepened cyclones have tracks more parallel to the U.S. east coast. The underdeepened cyclones over the central and eastern Pacific tend to occur farther south (35°–45°N) than the overdeepened events.

Observed Local and Remote Influences of Vegetation on the Atmosphere across North America Using a Model-Validated Statistical Technique That First Excludes Oceanic Forcings*

2014 ◽  
Vol 27 (1) ◽  
pp. 362-382 ◽  
Author(s):  
Fuyao Wang ◽  
Michael Notaro ◽  
Zhengyu Liu ◽  
Guangshan Chen
Keyword(s):  
United States ◽  
North America ◽  
Statistical Method ◽  
North American ◽  
Climate Model ◽  
Statistical Technique ◽  
Eastern United States ◽  
Climate System Model ◽  
The North ◽  
Vegetation Impact

Abstract The observed local and nonlocal influences of vegetation on the atmosphere across North America are quantified after first removing the oceanic impact. The interaction between vegetation and the atmosphere is dominated by forcing from the atmosphere, making it difficult to extract the forcing from vegetation. Furthermore, the atmosphere is not only influenced by vegetation but also the oceans, so in order to extract the vegetation impact, the oceanic forcing must first be excluded. This study identified significant vegetation impact in two climatically and ecologically unique regions: the North American monsoon region (NAMR) and the North American boreal forest (NABF). A multivariate statistical method, a generalized equilibrium feedback assessment, is applied to extract vegetation influence on the atmosphere. The statistical method is validated using a dynamical experiment for the NAMR in a fully coupled climate model, the Community Climate System Model, version 3.5 (CCSM3.5). The observed influence of NAMR vegetation on the atmosphere peaks in June–August and is primarily attributed to both roughness and hydrological feedbacks. Elevated vegetation amount increases evapotranspiration and surface roughness, which leads to a local decline in sea level pressure and generates an atmospheric teleconnection response. This atmospheric response leads to moister and cooler (drier and warmer) conditions over the western and central United States (Gulf states). The observed influence of the NABF on the atmosphere peaks in March–May, related to a thermal feedback. Enhanced vegetation greenness increases the air temperature locally. The atmosphere tends to form a positive Pacific–North American (PNA)-like pattern, and this anomalous atmospheric circulation and associated moisture advection lead to moister (drier) conditions in the western (eastern) United States.

Intraseasonal Teleconnection between North American and Western North Pacific Monsoons with 20-Day Time Scale

2008 ◽  
Vol 21 (11) ◽  
pp. 2664-2679 ◽  
Author(s):  
Xianan Jiang ◽  
Ngar-Cheung Lau
Keyword(s):  
United States ◽  
North American ◽  
North Pacific ◽  
Time Scale ◽  
Western North Pacific ◽  
Wave Train ◽  
Eastern Pacific ◽  
Southwestern United States ◽  
Low Level ◽  
The North

Abstract Based on a recently released, high-resolution reanalysis dataset for the North American region, the intraseasonal variability (ISV; with a time scale of about 20 days) of the North American monsoon (NAM) is examined. The rainfall signals associated with this phenomenon first emerge near the Gulf of Mexico and eastern Pacific at about 20°N. They subsequently migrate to the southwestern United States along the slope of the Sierra Madre Occidental. The rainfall quickly dissipates upon arrival at the desert region of Arizona and New Mexico (AZNM). The enhanced rainfall over AZNM is accompanied by strong southeasterly low-level flow along the Gulf of California. This pattern bears strong resemblance to the circulation related to “gulf surge” events, as documented by many studies. The southeasterly flow is associated with an anomalous low vortex over the subtropical eastern Pacific Ocean off California, and a midlatitude anticyclone over the central United States in the lower troposphere. This flow pattern is in broad agreement with that favoring the “wet surges” over the southwestern United States. It is further demonstrated that the aforementioned low-level circulations associated with ISV of the NAM are part of a prominent trans-Pacific wave train extending from the western North Pacific (WNP) to the Eastern Pacific/North America along a “great circle” path. The circulation anomalies along the axis of this wave train exhibit a barotropic vertical structure over most regions outside of the WNP, and a baroclinic structure over the WNP, thus suggesting the important role of convective activities over the WNP in sustaining this wave train. This inference is further substantiated by an analysis of the pattern of wave-activity–flux vectors. Variations in the WNP convection are correlated with the ISV of the monsoons in both North American and East Asian (EA)/WNP sectors. These relationships lead to notable teleconnections between NAM and the EA/WNP monsoon on 20-day time scales.

scholarly journals Intraseasonal and Interannual Variability in North American Storm Tracks and Its Relationship to Equatorial Pacific Variability

2013 ◽  
Vol 141 (10) ◽  
pp. 3610-3625 ◽  
Author(s):  
Kevin M. Grise ◽  
Seok-Woo Son ◽  
John R. Gyakum
Keyword(s):  
North America ◽  
Interannual Variability ◽  
North American ◽  
Southern Oscillation ◽  
Extratropical Cyclones ◽  
The North ◽  
The Pacific ◽  
Cyclone Tracks ◽  
Lagrangian Tracking ◽  
The North Atlantic Oscillation

Abstract Extratropical cyclones play a principal role in wintertime precipitation and severe weather over North America. On average, the greatest number of cyclones track 1) from the lee of the Rocky Mountains eastward across the Great Lakes and 2) over the Gulf Stream along the eastern coastline of North America. However, the cyclone tracks are highly variable within individual winters and between winter seasons. In this study, the authors apply a Lagrangian tracking algorithm to examine variability in extratropical cyclone tracks over North America during winter. A series of methodological criteria is used to isolate cyclone development and decay regions and to account for the elevated topography over western North America. The results confirm the signatures of four climate phenomena in the intraseasonal and interannual variability in North American cyclone tracks: the North Atlantic Oscillation (NAO), the El Niño–Southern Oscillation (ENSO), the Pacific–North American pattern (PNA), and the Madden–Julian oscillation (MJO). Similar signatures are found using Eulerian bandpass-filtered eddy variances. Variability in the number of extratropical cyclones at most locations in North America is linked to fluctuations in Rossby wave trains extending from the central tropical Pacific Ocean. Only over the far northeastern United States and northeastern Canada is cyclone variability strongly linked to the NAO. The results suggest that Pacific sector variability (ENSO, PNA, and MJO) is a key contributor to intraseasonal and interannual variability in the frequency of extratropical cyclones at most locations across North America.

A REVISION OF THE NORTH AMERICAN OMALIINAE (COLEOPTERA: STAPHYLINIDAE): THE GENERA ARPEDIUM ERICHSON AND EUCNECOSUM REITTER

1984 ◽  
Vol 116 (4) ◽  
pp. 487-527 ◽  
Author(s):  
J. M. Campbell
Keyword(s):  
United States ◽  
North American ◽  
Biological Data ◽  
Eastern United States ◽  
European Species ◽  
Boreal Species ◽  
Line Drawings ◽  
The North ◽  
New Synonymy ◽  
Scanning Electron

AbstractThe North American species of the genera Arpedium Erichson, and Eucnecosum Reitter are revised. Five species are recognized, the holarctic species E. brachypterum (Gravenhorst), E. tenue (LeConte) and E. brunnescens (J. Sahlberg), the transcontinental boreal species A. cribratum Fauvel and the eastern United States species A. schwarzi Fauvel.Lectotypes are designated for E. brachypterum, A. cribratum, A. angulare Fauvel (= A. cribratum), and A. schwarzi. The following new synonymy is established, Arpedium norvegicum var. sallasi Munster and Eucnecosum meybohmi Lohse (= E. tenue) and Arpedium angulare Fauvel and A. columbiense Hatch (= A. cribratum). All genera and species are described and illustrated with scanning electron photomicrographs and line drawings, four maps showing the North American distribution of each species are provided, and keys are presented to aid in the identification of all the species as well as the European species Arpedium quadrum (Gravenhorst). All available records and biological data for the species are summarized.The use of the generic name Eucnecosum Reitter is discussed and the transfer of brachypterum, tenue, and brunnescens from Arpedium to this genus by Lohse is confirmed.

A Field Key to the North American Species of Hylobius (Curculionidae)

1961 ◽  
Vol 93 (7) ◽  
pp. 501-502 ◽  
Author(s):  
R. J. Finnegan
Keyword(s):  
United States ◽  
North American ◽  
Economic Importance ◽  
North American Species ◽  
Eastern United States ◽  
Eastern Canada ◽  
The North

There are five known North American species in the genus Hylobius; H. pales (Hbst.), H. congener Dalla Torre, H. pinicola (Couper), H. radicis Buch., and H. warreni Wood. In recent years four of these species have increased considerably in economic importance in central and eastern Canada and the eastern United States; H. pales and H. radicis attacking pines and H. pinicola and H. warreni attacking spruces and pines. H. congener occurs only in small numbers and little is known about its ecology. It is important, therefore, to be able to separate these species readily in the field.

scholarly journals The North American Lightning Detection Network (NALDN)—Analysis of Flash Data: 2001–09

2011 ◽  
Vol 139 (5) ◽  
pp. 1305-1322 ◽  
Author(s):  
Richard E. Orville ◽  
Gary R. Huffines ◽  
William R. Burrows ◽  
Kenneth L. Cummins
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
The United States ◽  
The North ◽  
Lightning Detection ◽  
Geographical Regions ◽  
Positive Peak ◽  
The U.S ◽  
Cg Lightning

Cloud-to-ground (CG) lightning data have been analyzed for the years 2001–09 for North America, which includes Alaska, Canada, and the lower 48 U.S. states. Flashes recorded within the North American Lightning Detection Network (NALDN) are examined. No corrections for detection efficiency variability are made over the 9 yr of the dataset or over the large geographical area comprising North America. There were network changes in the NALDN during the 9 yr, but these changes have not been corrected for nor have the recorded data been altered in any way with the exception that all positive lightning reports with peak currents less than 15 kA have been deleted. Thus, the reader should be aware that secular changes are not just climatological in nature. All data were analyzed with a spatial resolution of 20 km. The analyses presented in this work provide a synoptic view of the interannual variability of lightning observations in North America, including the impacts of physical changes in the network during the 9 yr of study. These data complement and extend previous analyses that evaluate the U.S. NLDN during periods of upgrade. The total (negative and positive) flashes for ground flash density, the percentage of positive lightning, and the positive flash density have been analyzed. Furthermore, the negative and positive first stroke peak currents and the flash multiplicity have been examined. The highest flash densities in Canada are along the U.S.–Canadian border (1–2 flashes per square kilometer) and in the United States along the Gulf of Mexico coast from Texas through Florida (exceeding 14 flashes per square kilometer in Florida). The Gulf Stream is “outlined” by higher flash densities off the east coast of the United States. Maximum annual positive flash densities in Canada range primarily from 0.01 to 0.3 flashes per square kilometer, and in the United States to over 0.5 flashes per square kilometer in the Midwest and in the states of Louisiana and Mississippi. The annual percentage of positive lightning to ground varies from less than 2% over Florida to values exceeding 25% off the West Coast, Alaska, and the Yukon. A localized maximum in the percentage of positive lightning in the NALDN occurs in Manitoba and western Ontario, just north of North Dakota and Minnesota. When averaged over North America, first stroke negative median peak currents range from 19.8 kA in 2001 to 16.0 kA in 2009 and for all years, average 16.1 kA. First stroke positive median peak currents range from a high of 29.0 kA in 2008 and 2009 to a low of 23.3 kA in 2003 with a median of 25.7 kA for all years. There is a relatively sharp transition from low to high median negative peak currents along the Gulf and Atlantic coasts of the United States. No sharp transitions are observed for the median positive peak currents. Relatively lower positive peak currents occur throughout the southeastern United States. The highest values of mean negative multiplicity exceed 3.0 strokes per flash in the NALDN with some variation over the 9 yr. Lower values of mean negative multiplicity occur in the western United States. Positive flash mean multiplicity is slightly higher than 1.1, with the highest values of 1.7 observed in the southwestern states. As has been noted in prior research, CG lightning has significant variations from storm to storm as well as between geographical regions and/or seasons and, consequently, a single distribution for any lightning parameter, such as multiplicity or peak current, may not be sufficient to represent or describe the parameter.

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