Climatology and Trends in Hourly Precipitation for the Southeast United States

Abstract This research introduces a climatology of hourly precipitation characteristics, investigates trends in precipitation hours (PH) and hourly accumulation, and uses four different time series to determine if precipitation intensity is changing across the southeastern United States from 1960 to 2017. Results indicate hourly intensity significantly increased at 44% (22/50) of the stations, accompanied by an increase in average hourly accumulation at 40% of the sites analyzed (20/50). The average duration of precipitation events decreased at 82% (41/50) of the stations. However, the frequency of 90th percentile hourly events and events above station-specific average hourly totals did not show a broad increase similar to hourly intensity. It seems hourly events are becoming heavier on average, while the duration of the average precipitation event is decreasing. Geographically, heavy hourly events are more frequent along the Gulf Coast and decrease inland. PH significantly decreased across South Carolina, Georgia, and northern Florida, mainly due to significant decreases in winter (DJF) and spring (MAM). Decreases in PH during spring were contained to Georgia and South Carolina and were accompanied by a decrease in accumulation. Decreases in PH during winter were more widespread and did not exhibit a broad decrease in accumulation, suggesting winter precipitation across that portion of the region is becoming more intense.

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Power-law behaviour of hourly precipitation intensity and dry spell duration over the United States

10.5194/egusphere-egu2020-5632 ◽

2020 ◽

Author(s):

Christian Franzke ◽

Lichao Yang ◽

Zuntao Fu

Keyword(s):

United States ◽

Poisson Process ◽

Power Law ◽

Climate Models ◽

Regional Climate ◽

The United States ◽

Distribution Model ◽

Precipitation Event ◽

Hourly Precipitation ◽

Precipitation Events

<p>Precipitation is an important meteorological variable which is critical for weather risk assessment. For instance, intense but short precipitation events can lead to flash floods and landslides. Most statistical modelling studies assume that the occurrence of precipitation events is based on a Poisson process with exponentially distributed waiting times while precipitation intensities are typically described by a gamma distribution or a mixture of two exponential distributions. Here, we show by using hourly precipitation data over the United States that the waiting time between precipitation events is non-exponentially distributed and best described by a fractional Poisson process. A systematic model selection procedure reveals that the hourly precipitation intensities are best represented by a two-distribution model for about 90% of all stations. The two-distribution model consists of (a) a generalized Pareto distribution (GPD) model for bulk precipitation event sizes and (b) a power-law distribution for large and extreme events. Finally, we analyse regional climate model output to evaluate how the climate models represent the high-frequency temporal structure of U.S. precipitation. Our results reveal that these regional climate models fail to accurately reproduce the power-law behaviour of intensities and severely underestimate the long durations between events.</p>

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Earthquake sequences and b values in the southeast United States

Bulletin of the Seismological Society of America ◽

10.1785/bssa0640010267 ◽

1974 ◽

Vol 64 (1) ◽

pp. 267-273

Author(s):

Leland Timothy Long

Keyword(s):

United States ◽

South Carolina ◽

B Value ◽

Earthquake Activity ◽

Southeast United States ◽

B Values ◽

History Of ◽

Earthquake Sequences ◽

Foreshock Activity ◽

Epicentral Region

abstract Aftershock and foreshock activity within 12 hr of the July 13, 1971 earthquake near Seneca, South Carolina, indicates a b value of 0.9 at ML = 3.0. Approximately 40 events recorded in a 5-day aftershock survey near Seneca indicate a b value of 1.7 at ML = 0.5. A sequence of over 40 events occurring west of McCormick, South Carolina, indicates a b value of 1.3 at ML = 2.4. The McCormick sequence was active for 4 months. Unlike the Seneca region, the McCormick region has a history of earthquake activity. Examinations of other published southeastern b values suggest that southeastern United States earthquakes originate from conditions of ambient stress which vary with epicentral region or magnitude.

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Evaluation of NASA’s MERRA Precipitation Product in Reproducing the Observed Trend and Distribution of Extreme Precipitation Events in the United States

Journal of Hydrometeorology ◽

10.1175/jhm-d-15-0097.1 ◽

2016 ◽

Vol 17 (2) ◽

pp. 693-711 ◽

Cited By ~ 16

Author(s):

Hamed Ashouri ◽

Soroosh Sorooshian ◽

Kuo-Lin Hsu ◽

Michael G. Bosilovich ◽

Jaechoul Lee ◽

...

Keyword(s):

United States ◽

Extreme Precipitation ◽

Gulf Coast ◽

The United States ◽

Value Theory ◽

Extreme Value ◽

Precipitation Extremes ◽

Precipitation Product ◽

Extreme Precipitation Events ◽

Precipitation Events

Abstract This study evaluates the performance of NASA’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) precipitation product in reproducing the trend and distribution of extreme precipitation events. Utilizing the extreme value theory, time-invariant and time-variant extreme value distributions are developed to model the trends and changes in the patterns of extreme precipitation events over the contiguous United States during 1979–2010. The Climate Prediction Center (CPC) U.S. Unified gridded observation data are used as the observational dataset. The CPC analysis shows that the eastern and western parts of the United States are experiencing positive and negative trends in annual maxima, respectively. The continental-scale patterns of change found in MERRA seem to reasonably mirror the observed patterns of change found in CPC. This is not previously expected, given the difficulty in constraining precipitation in reanalysis products. MERRA tends to overestimate the frequency at which the 99th percentile of precipitation is exceeded because this threshold tends to be lower in MERRA, making it easier to be exceeded. This feature is dominant during the summer months. MERRA tends to reproduce spatial patterns of the scale and location parameters of the generalized extreme value and generalized Pareto distributions. However, MERRA underestimates these parameters, particularly over the Gulf Coast states, leading to lower magnitudes in extreme precipitation events. Two issues in MERRA are identified: 1) MERRA shows a spurious negative trend in Nebraska and Kansas, which is most likely related to the changes in the satellite observing system over time that has apparently affected the water cycle in the central United States, and 2) the patterns of positive trend over the Gulf Coast states and along the East Coast seem to be correlated with the tropical cyclones in these regions. The analysis of the trends in the seasonal precipitation extremes indicates that the hurricane and winter seasons are contributing the most to these trend patterns in the southeastern United States. In addition, the increasing annual trend simulated by MERRA in the Gulf Coast region is due to an incorrect trend in winter precipitation extremes.

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Analysis of Diurnal Patterns in Winter Precipitation across the Conterminous United States

Monthly Weather Review ◽

10.1175/mwr-2873.1 ◽

2005 ◽

Vol 133 (3) ◽

pp. 707-711 ◽

Cited By ~ 18

Author(s):

Shouraseni Sen Roy ◽

Robert C. Balling

Keyword(s):

United States ◽

Harmonic Wave ◽

Southeastern United States ◽

Winter Precipitation ◽

General Tendency ◽

Wind Speeds ◽

Diurnal Patterns ◽

Observation Bias ◽

Precipitation Events ◽

Variance Explained

Abstract Hourly winter (November–March) precipitation data were assembled for nearly 5000 stations in the conterminous United States over the period 1948–98. Despite a potential observation bias in the 24th hour, a general tendency for winter precipitation events was found to occur more frequently near sunrise than for any other time of the day. Based on the standardized amplitude of the first harmonic wave, the pattern is most pronounced in Texas and in an area surrounding Colorado and Wyoming. The pattern also appears significant in the southeastern United States and in northern California based on the variance explained by the first harmonic fit. It is suggested that the diurnal patterns seen in the conterminous United States are related to increased relative humidity values occurring near sunrise and increased wind speeds in the warm sector of cyclonic storms.

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Prolonged Dry Episodes over the Conterminous United States: New Tendencies Emerging during the Last 40 Years

Journal of Climate ◽

10.1175/2007jcli2013.1 ◽

2008 ◽

Vol 21 (9) ◽

pp. 1850-1862 ◽

Cited By ~ 108

Author(s):

Pavel Ya Groisman ◽

Richard W. Knight

Keyword(s):

United States ◽

Average Duration ◽

Warm Season ◽

Vegetation Period ◽

Total Precipitation ◽

Eastern United States ◽

The Past ◽

The Mean ◽

Rain Events ◽

Precipitation Events

Abstract A disproportionate increase in precipitation coming from intense rain events, in the situation of general warming (thus, an extension of the vegetation period with intensive transpiration), and an insignificant change in total precipitation could lead to an increase in the frequency of a potentially serious type of extreme events: prolonged periods without precipitation (even when the mean seasonal rainfall totals increase). This paper investigates whether this development is already occurring during the past several decades over the conterminous United States, for the same period when changes in frequency of intense precipitation events are being observed. Lengthy strings of “dry” days without sizeable (>1.0 mm) precipitation were assessed only during the warm season (defined as a period when mean daily temperature is above the 5°C threshold) when water is intensively used for transpiration and prolonged periods without sizable rainfall represent a hazard for terrestrial ecosystem’s health and agriculture. During the past four decades, the mean duration of prolonged dry episodes (1 month or longer in the eastern United States and 2 months or longer in the southwestern United States) has significantly increased. As a consequence the return period of 1-month-long dry episodes over the eastern United States has reduced more than twofold from 15 to 6–7 yr. The longer average duration of dry episodes has occurred during a relatively wet period across the country but is not observed over the northwestern United States.

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Subseasonal to Seasonal Extreme Precipitation Events in the Contiguous United States: Generation of a Database and Climatology

Journal of Climate ◽

10.1175/jcli-d-20-0580.1 ◽

2021 ◽

pp. 1-47

Author(s):

Ty A. Dickinson ◽

Michael B. Richman ◽

Jason C. Furtado

Keyword(s):

United States ◽

New England ◽

Extreme Precipitation ◽

Extreme Event ◽

Significant Risk ◽

Optimal Number ◽

Precipitation Event ◽

Hybrid Index ◽

Extreme Precipitation Events ◽

Precipitation Events

AbstractExtreme precipitation across multiple timescales is a natural hazard that creates a significant risk to life, with a commensurately large cost through property loss. We devise a method to create 14-day extreme event windows that characterize precipitation events in the contiguous United States (CONUS) for the years 1915 through 2018. Our algorithm imposes thresholds for both total precipitation and the duration of the precipitation to identify events with sufficient length to accentuate the synoptic and longer time scale contribution to the precipitation event. Kernel density estimation is employed to create extreme event polygons which are formed into a database spanning from 1915 through 2018. Using the developed database, we clustered events into regions using a k-means algorithm. We define the “Hybrid Index”, a weighted composite of silhouette score and number of clustered events, to show the optimal number of clusters is 14. We also show that 14-day extreme precipitation events are increasing in the CONUS, specifically in the Dakotas and much of New England. The algorithm presented in this work is designed to be sufficiently flexible to be extended to any desired number of days on the subseasonal-to-seasonal (S2S) timescale (e.g., 30 days). Additional databases generated using this framework are available for download from our GitHub. Consequently, these S2S databases can be analyzed in future works to determine the climatology of S2S extreme precipitation events and be used for predictability studies for identified events.

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Patterns of head shape and scutellation in Drymarchon couperi (Squamata: Colubridae) reveal a single species

Zootaxa ◽

10.11646/zootaxa.4695.2.6 ◽

2019 ◽

Vol 4695 (2) ◽

pp. 168-174

Author(s):

CRAIG GUYER ◽

BRIAN FOLT ◽

MICHELLE HOFFMAN ◽

DIRK STEVENSON ◽

SCOTT M. GOETZ ◽

...

Keyword(s):

United States ◽

South Carolina ◽

Gulf Coast ◽

Sequence Data ◽

Single Species ◽

Sensu Stricto ◽

Geographic Region ◽

Population Declines ◽

Genetic Lineages ◽

Fish And Wildlife Service

Krysko et al. (2016a) used analyses of DNA sequence data to reveal two genetic lineages of Drymarchon couperi. The Atlantic lineage contained specimens from southeastern Georgia and eastern peninsular Florida, and the Gulf Coast lineage contained specimens from western and southern peninsular Florida as well as western Florida, southern Alabama, and southern Mississippi. In a second paper Krysko et al. (2016b) analyzed morphological variation of the two lineages, which allowed them to restrict D. couperi to the Atlantic lineage and to describe the Gulf Coast lineage as a new species, Drymarchon kolpobasileus. This taxonomic discovery was remarkable for such a large, wide-ranging species and was notable for its impact on conservation. Because of population declines, particularly in western Florida, southern Alabama, and southern Mississippi, D. couperi (sensu lato) was listed as Threatened under the Endangered Species Act (United States Fish and Wildlife Service 1978, 2008) and repatriation of the species to areas where it had been extirpated was listed as a priority conservation goal (United States Fish and Wildlife Service 1982, 2008). Such repatriation efforts were attempted in Alabama, Florida, Georgia, and South Carolina, starting in 1977 (Speake et al. 1987), but failed to create viable populations, likely because too few snakes were released at too many sites (Guyer et al. 2019; Folt et al. 2019a). A second attempt at repatriation was started in 2010 and concentrated on release of snakes at a single site in Alabama (Stiles et al. 2013). However, Krysko et al. (2016a) criticized this repatriation effort because it appeared to involve release of D. couperi (sensu stricto) into the geographic region occupied by D. kolpobasileus (as diagnosed in Krysko et al. 2016b).

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Analysis of hourly precipitation characteristics in Kraków, southern Poland, using a classification of circulation types

Hydrology Research ◽

10.2166/nh.2009.056 ◽

2009 ◽

Vol 40 (6) ◽

pp. 553-563 ◽

Cited By ~ 4

Author(s):

Robert Twardosz

Keyword(s):

Atmospheric Circulation ◽

Circulation Type ◽

Exceedance Probability ◽

Maximum Precipitation ◽

Southern Poland ◽

Hourly Precipitation ◽

Circulation Types ◽

Precipitation Characteristics ◽

Pressure Centre ◽

Precipitation Events

This paper investigates the relationship between maximum precipitation in Kraków and types of atmospheric circulation in southern Poland, as classified by Niedźwiedź. Three characteristics were used to define this relationship: maximum precipitation (Pmax), its duration (d) and probability of exceedance (p). The input data came from Kraków's uniquely long and homogenous pluviographic record spanning the period 1886–2007. Hourly precipitation values for the maximum precipitation events were identified and arranged in 1–24 hour intervals. They were then processed using the generalized extreme value (GEV) distribution to produce quantiles of maximum precipitation totals in each of the intervals and broken down by the corresponding circulation type. Differences between the development mechanisms are manifested in relationships between precipitation characteristics and their measure of randomness, i.e. exceedance probability. This paper demonstrates that maximum precipitation events depend on their duration d and atmospheric circulation. The maximum short-duration (one-hour) events occur primarily in either of two circulation types: (i) cyclonic with advection from the east and from the southeast or (ii) low-pressure centre and cyclonic trough. Maximum long-duration precipitation events (24 hour), on the other hand, occur in the cyclonic type of circulation with advection from the north and from the northeast.

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A Climatology of Weakly Forced and Pulse Thunderstorms in the Southeast United States

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0005.1 ◽

2017 ◽

Vol 56 (11) ◽

pp. 3017-3033 ◽

Cited By ~ 11

Author(s):

Paul W. Miller ◽

Thomas L. Mote

Keyword(s):

United States ◽

Great Plains ◽

Gulf Coast ◽

Warm Season ◽

Large Sample Size ◽

Southeast United States ◽

Modes Of Variability ◽

Blue Ridge Mountains ◽

Fall Line ◽

River Valleys

AbstractWeakly forced thunderstorms (WFTs), convection forming in the absence of a synoptic forcing mechanism and its associated shear regime, are the dominant convective mode during the warm season in the southeast United States. This study uses 15 yr (2001–15) of warm-season (May–September) composite reflectivity images from 30 WSR-88D sites in the southeastern United States to detect WFTs and pulse thunderstorms, defined as WFTs associated with a severe weather event. Thunderstorms were identified as regions of contiguous reflectivities greater than or equal to 40 dBZ using connected neighborhoods labeling. Ward’s clustering was then performed upon the duration, size, strength, initiation time, and solidity of the approximately 1 900 000 thunderstorms. Of the 10 clusters of morphologically similar storms, five groups, containing 885 496 thunderstorms, were designated as WFTs. In line with previous work, WFT development mirrors landscape features, such as the Appalachian Mountains and Mississippi Delta. However, the large sample size also reveals more subtle nuances to the spatial distribution, such as decreases over river valleys and increases along the Atlantic fall line. The most active pulse thunderstorm region, the Blue Ridge Mountains, was displaced from the overall WFT maximum: the Florida Peninsula and Gulf Coast. Most pulse thunderstorms were associated with larger moisture values, particularly in the midlevels, which supported larger and longer-lasting WFT complexes. Synoptically, two distinct modes of variability yielded WFT-favorable environments: the intrusion of the Bermuda high from the east and the expansion of high pressure over the southern Great Plains from the west.

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Three Recent Flavors of Drought in the Pacific Northwest

Journal of Applied Meteorology and Climatology ◽

10.1175/2010jamc2423.1 ◽

2010 ◽

Vol 49 (9) ◽

pp. 2058-2068 ◽

Cited By ~ 8

Author(s):

Karin A. Bumbaco ◽

Philip W. Mote

Keyword(s):

United States ◽

Pacific Northwest ◽

Summer Precipitation ◽

Winter Precipitation ◽

Western United States ◽

Hydropower Generation ◽

The Past ◽

The Pacific ◽

Hydrologic Impacts ◽

Precipitation Events

Abstract In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future.

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