scholarly journals Assimilating Surface Mesonet Observations with the EnKF to Improve Ensemble Forecasts of Convection Initiation on 29 May 2012

2015 ◽  
Vol 143 (9) ◽  
pp. 3700-3725 ◽  
Author(s):  
Ryan A. Sobash ◽  
David J. Stensrud
Keyword(s):  
Great Plains ◽  
Ensemble Forecasts ◽  
Moisture Profile ◽  
Southern Great Plains ◽  
Surface Moisture ◽  
Surface Data ◽  
Temporal And Spatial ◽  
Convection Initiation ◽  
The Impact ◽  
Surface Observations

Abstract Surface data assimilation (DA) has the potential to improve forecasts of convection initiation (CI) and short-term forecasts of convective evolution. Since the processes driving CI occur on scales inadequately observed by conventional observation networks, mesoscale surface networks could be especially beneficial given their higher temporal and spatial resolution. This work aims to assess the impact of high-frequency assimilation of mesonet surface DA on ensemble forecasts of CI initialized with ensemble Kalman filter (EnKF) analyses of the 29 May 2012 convective event over the southern Great Plains. Mesonet and conventional surface observations were assimilated every 5 min for 3 h from 1800 to 2100 UTC and 3-h ensemble forecasts were produced. Forecasts of CI timing and location were improved by assimilating the surface datasets in comparison to experiments where mesonet data were withheld. This primarily occurred due to a more accurate representation of the boundary layer moisture profile across the domain, especially in the vicinity of a dryline and stationary boundary. Ensemble forecasts produced by assimilating surface observations at hourly intervals, instead of every 5 min, showed only minor improvements in CI. The 5-min assimilation of mesonet data improved forecasts of the placement and timing of CI for this particular event due to the ability of mesonet data to capture rapidly evolving mesoscale features and to constrain model biases, particularly surface moisture errors, during the cycling period.

scholarly journals A 20-Year Climatology of Nocturnal Convection Initiation over the Central and Southern Great Plains during the Warm Season

2017 ◽  
Vol 145 (5) ◽  
pp. 1615-1639 ◽  
Author(s):  
Dylan W. Reif ◽  
Howard B. Bluestein
Keyword(s):  
Great Plains ◽  
Warm Season ◽  
Thunderstorm Activity ◽  
Surface Boundary ◽  
Initiation Time ◽  
Southern Great Plains ◽  
Surface Data ◽  
Convection Initiation ◽  
Storm Characteristics

Abstract A nocturnal maximum in rainfall and thunderstorm activity over the central Great Plains has been widely documented, but the mechanisms for the development of thunderstorms over that region at night are still not well understood. Elevated convection above a surface frontal boundary is one explanation, but this study shows that many thunderstorms form at night without the presence of an elevated frontal inversion or nearby surface boundary. This study documents convection initiation (CI) events at night over the central Great Plains from 1996 to 2015 during the months of April–July. Storm characteristics such as storm type, linear system orientation, initiation time and location, and others were documented. Once all of the cases were documented, surface data were examined to locate any nearby surface boundaries. The event’s initiation location relative to these boundaries (if a boundary existed) was documented. Two main initiation locations relative to a surface boundary were identified: on a surface boundary and on the cold side of a surface boundary; CI events also occur without any nearby surface boundary. There are many differences among the different nocturnal CI modes. For example, there appear to be two main peaks of initiation time at night: one early at night and one later at night. The later peak is likely due to the events that form without a nearby surface boundary. Finally, a case study of three nocturnal CI events that occurred during the Plains Elevated Convection At Night (PECAN) field project when there was no nearby surface boundary is discussed.

The Impact of Affective Heuristics in Decision-Making Regarding the Implementation of Prescribed Fire on Private Rangelands in the Southern Great Plains, USA

2021 ◽  
pp. 1-18
Author(s):  
J. Kelly Hoffman ◽  
R. Patrick Bixler ◽  
Morgan L. Treadwell ◽  
Lars G. Coleman ◽  
Thomas W. McDaniel ◽  
...  
Keyword(s):  
Decision Making ◽  
Great Plains ◽  
Prescribed Fire ◽  
Southern Great Plains ◽  
The Impact

scholarly journals Ten Years of Aerosol Effects on Single-Layer Overcast Clouds over the US Southern Great Plains and the China Loess Plateau

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Hongru Yan ◽  
Tianhe Wang
Keyword(s):  
Great Plains ◽  
Indirect Effect ◽  
Negative Relationship ◽  
Single Layer ◽  
Cloud Base ◽  
Atmospheric Conditions ◽  
Southern Great Plains ◽  
Aerosol Loading ◽  
The Us ◽  
The Impact

Using almost 10 years of observations of clouds and aerosols from the US Southern Great Plains (SGP) atmospheric observatory and the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) in China, the impact of aerosols on single-layer overcast clouds over continental land for different regimes were investigated. Atmospheric conditions at the two sites were first compared in an attempt to isolate the influence of aerosols on cloud properties from dynamic and thermodynamic influences. Cloud types and amounts are similar at the two sites. The dominant aerosol types at the SGP and SACOL sites are sulphate and dust, respectively, with greater aerosol optical depths (AODs) and absorption at the SACOL site. Aerosol first indirect effect (FIE) ranges from 0.021 to 0.152 and from −0.078 to 0.047 at the SGP and SACOL sites, respectively, when using the AOD below cloud base as CCN proxy. Although differences exist, the influence of meteorological conditions on the FIE at the two sites is consistent. FIEs are easily detected under descending motion and dry condition. The FIE at the SGP site is larger than that at the SACOL site, which suggests that the cloud albedo effect is more sensitive under relatively cleaner atmospheric conditions and the dominating aerosol at the SACOL site has less hygroscopicity. The radiative forcing of the FIE over the SGP site is −3.2 W m−2 for each 0.05 increment in FIE. Cloud durations generally prolong as aerosol loading increases, which is consistent with the hypothesis of the aerosol second indirect effect. The negative relationship between cloud duration time and aerosol loading when aerosol loading reaches a large value further might suggest a semidirect effect.

scholarly journals Convection Initiation along Soil Moisture Boundaries in the Southern Great Plains

2010 ◽  
Vol 138 (4) ◽  
pp. 1140-1151 ◽  
Author(s):  
John D. Frye ◽  
Thomas L. Mote
Keyword(s):  
Soil Moisture ◽  
Great Plains ◽  
Tropical Rainfall Measuring Mission ◽  
Moisture Gradient ◽  
Synoptic Type ◽  
Southern Great Plains ◽  
Volumetric Soil Moisture ◽  
Soil Moisture Gradient ◽  
Microwave Imager ◽  
Convection Initiation

Abstract Boundaries between two dissimilar air masses have been shown to be the focus region for convection initiation. One feature that has been shown to create these boundaries, as well as mesoscale circulation patterns conducive for convection, is soil moisture heterogeneities. These relationships have been validated in modeling studies, short-term field campaigns, and reanalysis of severe weather events. This study examines the role of soil moisture on convection initiation by using observational data over 7 yr (1998–2004) in the southern Great Plains. A key component to this research is the recently developed daily soil moisture product from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). The locations of convection initiation, based on the Weather Surveillance Radar-1988 Doppler (WSR-88D) data, were compared to volumetric soil moisture values and volumetric soil moisture gradient values. The locations of convection initiation were also examined based on synoptic-type day. On synoptically benign days, increased soil moisture and soil moisture gradient values were associated with decreased convection initiation, to a point. After soil moisture reached 15% (25%) on days with (without) a low-level jet, the likelihood of convection initiation increased. On synoptically primed days, the probabilities of convection initiation were more variable throughout the range of soil moisture values, indicating that the synoptically primed conditions may reduce the influence of soil moisture heterogeneities. Results indicate that a critical value in soil moisture and soil moisture gradient may exist that alters the mesoscale effect of changes in soil moisture on convection initiation, particularly on days that would be classified as synoptically benign.

Initiation Mechanisms of Nocturnal Convection without Nearby Surface Boundaries over the Central and Southern Great Plains during the Warm Season

2018 ◽  
Vol 146 (9) ◽  
pp. 3053-3078 ◽  
Author(s):  
Dylan W. Reif ◽  
Howard B. Bluestein
Keyword(s):  
Case Studies ◽  
Great Plains ◽  
Field Experiments ◽  
Warm Season ◽  
Surface Boundary ◽  
Spatiotemporal Resolution ◽  
Southern Great Plains ◽  
Convective Systems ◽  
Low Level Jet ◽  
Convection Initiation

Abstract The number of case studies in the literature of nocturnal convection has increased during the past decade, especially those that utilize high-spatiotemporal-resolution datasets from field experiments such as the International H2O Project (IHOP_2002) and Plains Elevated Convection at Night (PECAN). However, there are few case studies of events for convection initiation without a nearby surface boundary. These events account for approximately 25% of all nocturnal convection initiation (CI) events. Unique characteristics of these events include a peak initiation time later at night, a preferred initiation location in northern Kansas and southern Nebraska, and a preferred north–south orientation to linear convective systems. In this study, four case studies of convection that is initiated without a nearby surface boundary are detailed to reveal a number of possible initiation mechanisms, including quasigeostrophic-aided ascent, elevated ascent associated with convergent layers (of unknown causes), the low-level jet, and gravity waves. The case studies chosen illustrate the wide variety of synoptic-scale conditions under which these events can occur.

scholarly journals Understanding the Impact of Radar and In Situ Observations on the Prediction of a Nocturnal Convection Initiation Event on 25 June 2013 Using an Ensemble-Based Multiscale Data Assimilation System

2018 ◽  
Vol 146 (6) ◽  
pp. 1837-1859 ◽  
Author(s):  
Samuel K. Degelia ◽  
Xuguang Wang ◽  
David J. Stensrud ◽  
Aaron Johnson
Keyword(s):  
Data Assimilation ◽  
Great Plains ◽  
Cold Pool ◽  
Radar Observations ◽  
Low Level ◽  
In Situ Observations ◽  
Outflow Boundary ◽  
Convection Initiation ◽  
The Impact

The initiation of new convection at night in the Great Plains contributes to a nocturnal maximum in precipitation and produces localized heavy rainfall and severe weather hazards in the region. Although previous work has evaluated numerical model forecasts and data assimilation (DA) impacts for convection initiation (CI), most previous studies focused only on convection that initiates during the afternoon and not explicitly on nocturnal thunderstorms. In this study, we investigate the impact of assimilating in situ and radar observations for a nocturnal CI event on 25 June 2013 using an ensemble-based DA and forecast system. Results in this study show that a successful CI forecast resulted only when assimilating conventional in situ observations on the inner, convection-allowing domain. Assimilating in situ observations strengthened preexisting convection in southwestern Kansas by enhancing buoyancy and locally strengthening low-level convergence. The enhanced convection produced a cold pool that, together with increased convergence along the northwestern low-level jet (LLJ) terminus near the region of CI, was an important mechanism for lifting parcels to their level of free convection. Gravity waves were also produced atop the cold pool that provided further elevated ascent. Assimilating radar observations further improved the forecast by suppressing spurious convection and reducing the number of ensemble members that produced CI along a spurious outflow boundary. The fact that the successful CI forecasts resulted only when the in situ observations were assimilated suggests that accurately capturing the preconvective environment and specific mesoscale features is especially important for nocturnal CI forecasts.

scholarly journals An Evaluation of the Impact of Assimilating AERI Retrievals, Kinematic Profilers, Rawinsondes, and Surface Observations on a Forecast of a Nocturnal Convection Initiation Event during the PECAN Field Campaign

2019 ◽  
Vol 147 (8) ◽  
pp. 2739-2764 ◽  
Author(s):  
Samuel K. Degelia ◽  
Xuguang Wang ◽  
David J. Stensrud
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Operational Forecasts ◽  
Outflow Boundary ◽  
Convection Initiation ◽  
The Impact ◽  
Surface Observations ◽  
Wind Profilers

Abstract Numerical weather prediction models often fail to correctly forecast convection initiation (CI) at night. To improve our understanding of such events, researchers collected a unique dataset of thermodynamic and kinematic remote sensing profilers as part of the Plains Elevated Convection at Night (PECAN) experiment. This study evaluates the impacts made to a nocturnal CI forecast on 26 June 2015 by assimilating a network of atmospheric emitted radiance interferometers (AERIs), Doppler lidars, radio wind profilers, high-frequency rawinsondes, and mobile surface observations using an advanced, ensemble-based data assimilation system. Relative to operational forecasts, assimilating the PECAN dataset improves the timing, location, and orientation of the CI event. Specifically, radio wind profilers and rawinsondes are shown to be the most impactful instrument by enhancing the moisture advection into the region of CI in the forecast. Assimilating thermodynamic profiles collected by the AERIs increases midlevel moisture and improves the ensemble probability of CI in the forecast. The impacts of assimilating the radio wind profilers, AERI retrievals, and rawinsondes remain large throughout forecasting the growth of the CI event into a mesoscale convective system. Assimilating Doppler lidar and surface data only slightly improves the CI forecast by enhancing the convergence along an outflow boundary that partially forces the nocturnal CI event. Our findings suggest that a mesoscale network of profiling and surface instruments has the potential to greatly improve short-term forecasts of nocturnal convection.

scholarly journals The Heated Condensation Framework. Part I: Description and Southern Great Plains Case Study

2015 ◽  
Vol 16 (5) ◽  
pp. 1929-1945 ◽  
Author(s):  
Ahmed B. Tawfik ◽  
Paul A. Dirmeyer ◽  
Joseph A. Santanello
Keyword(s):  
Great Plains ◽  
Companion Paper ◽  
Layer Growth ◽  
Moisture Profile ◽  
Convective Initiation ◽  
Southern Great Plains ◽  
Clear Sky ◽  
The North ◽  
Convective State ◽  
Regional Reanalysis

Abstract This study extends the heated condensation framework (HCF) presented in Tawfik and Dirmeyer to include variables for describing the convective background state of the atmosphere used to quantify the contribution of the atmosphere to convective initiation within the context of land–atmosphere coupling. In particular, the ability for the full suite of HCF variables to 1) quantify the amount of latent and sensible heat energy necessary for convective initiation, 2) identify the transition from moistening advantage to boundary layer growth advantage, 3) identify locally originating convection, and 4) compare models and observations, directly highlighting biases in the convective state, is demonstrated. These capabilities are illustrated for a clear-sky and convectively active day over the Atmospheric Radiation Measurement Program Southern Great Plains central station using observations, the Rapid Update Cycle (RUC) operational model, and the North American Regional Reanalysis (NARR). The clear-sky day had a higher and unattainable convective threshold, making convective initiation unlikely. The convectively active day had a lower threshold that was attained by midafternoon, reflecting local convective triggering. Compared to observations, RUC tended to have the most difficulty representing the convective state and captured the threshold for the clear-sky case only because of compensating biases in the moisture and temperature profiles. Despite capturing the observed moisture profile very well, a stronger surface inversion in NARR returned overestimates in the convective threshold. The companion paper applies the HCF variables introduced here across the continental United States to examine the climatological behavior of convective initiation and local land–atmosphere coupling.

Cattle Trailing in the Nineteenth Century

1975 ◽  
Vol 35 (2) ◽  
pp. 458-460
Author(s):  
R. Taylor Dennen
Keyword(s):  
Nineteenth Century ◽  
Great Plains ◽  
Recent Article ◽  
Late Nineteenth Century ◽  
Relative Prices ◽  
Southern Great Plains ◽  
History Of ◽  
Late Nineteenth ◽  
The Impact

In a recent article in this Journal David Galenson presents an interesting hypothesis about the impact of changing relative prices on the cattle driving industry in the late nineteenth-century West. Briefly, he argues that movements of.cattle prices in the urban marketing centers relative to the local prices in the range areas affected the profitability of the industry and thus the quantity of cattle driven north from Texas. Unfortunately, in testing his hypothesis, Mr. Galenson has incorrectly interpreted the history of the southern Great Plains.

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