scholarly journals Diurnal Effects of Regional Soil Moisture Anomalies on the Great Plains Low-Level Jet

2019 ◽  
Vol 147 (12) ◽  
pp. 4611-4631 ◽  
Author(s):  
Matthew A. Campbell ◽  
Craig R. Ferguson ◽  
D. Alex Burrows ◽  
Mark Beauharnois ◽  
Geng Xia ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Great Plains ◽  
Warm Season ◽  
Past Research ◽  
Severe Weather ◽  
Heat Accumulation ◽  
Low Level ◽  
Synoptic Conditions ◽  
Low Level Jet ◽  
Dry Soil

Abstract The Great Plains (GP) low-level jet (GPLLJ) contributes to GP warm season water resources (precipitation), wind resources, and severe weather outbreaks. Past research has shown that synoptic and local mesoscale physical mechanisms (Holton and Blackadar mechanisms) are required to explain GPLLJ variability. Although soil moisture–PBL interactions are central to local mechanistic theories, the diurnal effect of regional soil moisture anomalies on GPLLJ speed, northward penetration, and propensity for severe weather is not well known. In this study, two 31-member WRF-ARW stochastic kinetic energy backscatter scheme ensembles simulate a typical warm season GPLLJ case under CONUS-wide wet and dry soil moisture scenarios. In the GP (24°–48°N, 103°–90°W), ensemble mean differences in sensible heating and PBL height of 25–150 W m−2 and 100–700 m, respectively, at 2100 UTC (afternoon) culminate in GPLLJ 850-hPa wind speed differences of 1–4 m s−1 12 hours later (0900 UTC; early morning). Greater heat accumulation in the daytime PBL over dry soil impacts the east–west geopotential height gradient in the GP (synoptic conditions and Holton mechanism) resulting in a deeper thermal low in the northern GP, causing increases in the geostrophic wind. Enhanced daytime turbulent mixing over dry soil impacts the PBL structure (Blackadar mechanism), leading to increased ageostrophic wind. Overnight geostrophic and ageostrophic winds constructively interact, leading to a faster nocturnal GPLLJ over dry soil. Ensemble differences in CIN (~50–150 J kg−1) and CAPE (~500–1000 J kg−1) have implications for severe weather predictability.

scholarly journals Does Afternoon Precipitation Occur Preferentially over Dry or Wet Soils in Oklahoma?

2015 ◽  
Vol 16 (2) ◽  
pp. 874-888 ◽  
Author(s):  
Trent W. Ford ◽  
Anita D. Rapp ◽  
Steven M. Quiring
Keyword(s):  
Soil Moisture ◽  
Great Plains ◽  
Convective Available Potential Energy ◽  
Warm Season ◽  
Causal Link ◽  
Atmospheric Conditions ◽  
Low Level ◽  
Low Level Jet ◽  
The Impact ◽  
Soil Moisture Feedback

Abstract Soil moisture is an integral part of the climate system and can drive land–atmosphere interactions through the partitioning of latent and sensible heat. Soil moisture feedback to precipitation has been documented in several regions of the world, most notably in the southern Great Plains. However, the impact of soil moisture on precipitation, particularly at short (subdaily) time scales, has not been resolved. Here, in situ soil moisture observations and satellite-based precipitation estimates are used to examine if afternoon precipitation falls preferentially over wet or dry soils in Oklahoma. Afternoon precipitation events during the warm season (May–September) in Oklahoma from 2003 and 2012 are categorized by how favorable atmospheric conditions are for convection, as well as the presence or absence of the Great Plains low-level jet. The results show afternoon precipitation falls preferentially over wet soils when the Great Plains low-level jet is absent. In contrast, precipitation falls preferentially over dry soils when the low-level jet is present. Humidity (temperature) is increased (decreased) as soil moisture increases for all conditions, and convective available potential energy prior to convection is strongest when atmospheric humidity is above normal. The results do not demonstrate a causal link between soil moisture and precipitation, but they do suggest that soil moisture feedback to precipitation could potentially manifest itself over wetter- and drier-than-normal soils, depending on the overall synoptic and dynamic conditions.

The Great Plains Low-Level Jet during the Warm Season of 1993

1997 ◽  
Vol 125 (9) ◽  
pp. 2176-2192 ◽  
Author(s):  
Raymond W. Arritt ◽  
Thomas D. Rink ◽  
Moti Segal ◽  
Dennis P. Todey ◽  
Craig A. Clark ◽  
...  
Keyword(s):  
Great Plains ◽  
Warm Season ◽  
Low Level ◽  
Low Level Jet

scholarly journals Predictability of Midsummer Great Plains Low-Level Jet and Associated Precipitation

2020 ◽  
Vol 35 (1) ◽  
pp. 215-235 ◽  
Author(s):  
Kelsey M. Malloy ◽  
Ben P. Kirtman
Keyword(s):  
Great Plains ◽  
North American ◽  
Large Scale ◽  
Linear Regression Analysis ◽  
Intraseasonal Variability ◽  
Warm Season ◽  
Summer Precipitation ◽  
Climate System Model ◽  
Low Level ◽  
Low Level Jet

Abstract Warm-season precipitation in the U.S. “Corn Belt,” the Great Plains, and the Midwest greatly influences agricultural production and is subject to high interannual and intraseasonal variability. Unfortunately, current seasonal and subseasonal forecasts for summer precipitation have relatively low skill. Therefore, there are ongoing efforts to understand hydroclimate variability targeted at improving predictions, particularly through its primary transporter of moisture: the Great Plains low-level jet (LLJ). This study uses the Community Climate System Model, version 4 (CCSM4), July forecasts, made as part of the North American Multi-Model Ensemble (NMME), to assess skill in reproducing the monthly Great Plains LLJ and associated precipitation. Generally, the CCSM4 forecasts capture the climatological jet but have problems representing the observed variability beyond two weeks. In addition, there are predictors associated with the large-scale variability identified through linear regression analysis, shifts in kernel density estimators, and case study analysis that suggest potential for improving confidence in forecasts. In this study, a strengthened Caribbean LLJ, negative Pacific–North American (PNA) teleconnection, El Niño, and a negative Atlantic multidecadal oscillation each have a relatively strong and consistent relationship with a strengthened Great Plains LLJ. The circulation predictors, the Caribbean LLJ and PNA, present the greatest “forecast of opportunity” for considering and assigning confidence in monthly forecasts.

The Role of Upper-Level Coupling on Great Plains Low-Level Jet Structure and Variability

2020 ◽  
Vol 77 (12) ◽  
pp. 4317-4335
Author(s):  
D. Alex Burrows ◽  
Craig R. Ferguson ◽  
Lance F. Bosart
Keyword(s):  
Great Plains ◽  
Atmospheric Stability ◽  
Warm Season ◽  
Inertial Oscillation ◽  
Low Level ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Southern Central ◽  
Low Level Jet ◽  
Upper Level

AbstractThe Great Plains (GP) southerly nocturnal low-level jet (GPLLJ) is a dominant contributor to the region’s warm-season (May–September) mean and extreme precipitation, wind energy generation, and severe weather outbreaks—including mesoscale convective systems. The spatiotemporal structure, variability, and impact of individual GPLLJ events are closely related to their degree of upper-level synoptic coupling, which varies from strong coupling in synoptic trough–ridge environments to weak coupling in quiescent, synoptic ridge environments. Here, we apply an objective dynamic classification of GPLLJ upper-level coupling and fully characterize strongly coupled (C) and relatively uncoupled (UC) GPLLJs from the perspective of the ground-based observer. Through composite analyses of C and UC GPLLJ event samples taken from the European Centre for Medium-Range Weather Forecasts’ Coupled Earth Reanalysis of the twentieth century (CERA-20C), we address how the frequency of these jet types, as well as their inherent weather- and climate-relevant characteristics—including wind speed, direction, and shear; atmospheric stability; and precipitation—vary on diurnal and monthly time scales across the southern, central, and northern subregions of the GP. It is shown that C and UC GPLLJ events have similar diurnal phasing, but the diurnal amplitude is much greater for UC GPLLJs. C GPLLJs tend to have a faster and more elevated jet nose, less low-level wind shear, and enhanced CAPE and precipitation. UC GPLLJs undergo a larger inertial oscillation (Blackadar mechanism) for all subregions, and C GPLLJs have greater geostrophic forcing (Holton mechanism) in the southern and northern GP. The results underscore the need to differentiate between C and UC GPLLJs in future seasonal forecast and climate prediction activities.

scholarly journals The Synergistic Relationship between Soil Moisture and the Low-Level Jet and Its Role on the Prestorm Environment in the Southern Great Plains

2010 ◽  
Vol 49 (4) ◽  
pp. 775-791 ◽  
Author(s):  
John D. Frye ◽  
Thomas L. Mote
Keyword(s):  
Soil Moisture ◽  
Great Plains ◽  
Convective Available Potential Energy ◽  
Rank Correlation ◽  
Reanalysis Dataset ◽  
Synoptic Type ◽  
Southern Great Plains ◽  
Low Level ◽  
Convective Parameter ◽  
Low Level Jet

Abstract Changes in low-level moisture alter the convective parameters [e.g., convective available potential energy (CAPE), lifted index (LI), and convective inhibition (CIN)] as a result of alterations in the latent and sensible heat energy exchange. Two sources for low-level moisture exist in the southern Great Plains: 1) moisture advection by the low-level jet (LLJ) from the Gulf of Mexico and 2) evaporation and transpiration from the soils and vegetation in the region. The primary focus of this study is to examine the spatial distribution of soil moisture on a daily basis and to determine the effect it has on the convective parameters. The secondary objective is to investigate how the relationship between soil moisture and convective parameters is altered by the presence of an LLJ. The soil moisture data were obtained through newly developed procedures and advances in technology aboard the Tropical Rainfall Measuring Mission Microwave Imager. The convective parameter data were obtained through the North American Regional Reanalysis dataset. The study examined seven warm seasons (April–September) from 1998 to 2004 and found that the convective environment is more unstable (CAPE > 900 J kg−1, LI < −2°C) but more strongly capped (CIN > 70 J kg−1) on days with an LLJ present. Spearman’s rank correlation analysis showed a less stable atmosphere with increased soil moisture, after soil moisture reached 5%, on most days. Additional analysis determined that on all synoptic-type days the probability of reaching various thresholds of convective intensity increased as soil moisture values increased. The probabilities were even greater on days with an LLJ present than on the days without an LLJ present. An examination of four days representing each synoptic-type day indicates that on the daily scale the intensity of the convective environment is closely related to the high soil moisture and the presence of an LLJ.

scholarly journals Effects of Soil Moisture on the Longitudinal Dryline Position in the Southern Great Plains

2018 ◽  
Vol 19 (2) ◽  
pp. 273-287 ◽  
Author(s):  
Zachary F. Johnson ◽  
Nathan M. Hitchens
Keyword(s):  
Soil Moisture ◽  
Great Plains ◽  
Past Research ◽  
Severe Weather ◽  
Specific Humidity ◽  
Southern Great Plains ◽  
Average Value ◽  
Humidity Gradient ◽  
Longitudinal Position

Abstract The dryline is among the most important meteorological phenomena in the Great Plains because of its significance in tornadogenesis, severe weather, and consistent rainfall. Past research has extensively examined the dynamics of the dryline; however, recent meteorological research looks beyond dynamics and focuses on land–atmosphere interactions. This study focuses on how soil moisture, a surrogate for evapotranspiration, affects the climatological longitudinal positioning of the dryline, presenting a climatological study for the months of April–June during 2006–15 in the southern Great Plains. Here, drylines are defined as specific humidity gradients exceeding 3 g kg−1 (100 km)−1 that do not deviate more than 30° from a north–south orientation; they were found to occur on 33.4% of spring days, and the most favorable position was −100.9° at 0000 UTC. Specific humidity gradients ranged from 3.0 to 15.2 g kg−1 (100 km)−1, with an average value of 6.8 g kg−1 (100 km)−1. A relationship between the dryline longitudinal position and soil moisture was found; as soil moisture values increased, the dryline was located farther west, which suggests soil moisture may influence the longitudinal positioning of the dryline. There was also a relationship between the gradient of soil moisture and the intensity (specific humidity gradient) of the dryline, such that when longitudinal soil moisture gradients were strong (increasing from west to east), the dryline intensity increased.

Understanding the influence of ENSO on the Great Plains low-level jet in CMIP5 models

2017 ◽  
Vol 51 (4) ◽  
pp. 1537-1558 ◽  
Author(s):  
James F. Danco ◽  
Elinor R. Martin
Keyword(s):  
Great Plains ◽  
Cmip5 Models ◽  
Low Level ◽  
Low Level Jet

scholarly journals Assimilation of Satellite-Derived Soil Moisture for Improved Forecasts of the Great Plains Low-Level Jet

2020 ◽  
Vol 148 (11) ◽  
pp. 4607-4627
Author(s):  
Craig R. Ferguson ◽  
Shubhi Agrawal ◽  
Mark C. Beauharnois ◽  
Geng Xia ◽  
D. Alex Burrows ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Data Assimilation ◽  
Great Plains ◽  
Wrf Model ◽  
Added Value ◽  
Low Level ◽  
Convective Systems ◽  
South Central ◽  
Mesoscale Convective

AbstractIn the context of forecasting societally impactful Great Plains low-level jets (GPLLJs), the potential added value of satellite soil moisture (SM) data assimilation (DA) is high. GPLLJs are both sensitive to regional soil moisture gradients and frequent drivers of severe weather, including mesoscale convective systems. An untested hypothesis is that SM DA is more effective in forecasts of weakly synoptically forced, or uncoupled GPLLJs, than in forecasts of cyclone-induced coupled GPLLJs. Using the NASA Unified Weather Research and Forecasting (NU-WRF) Model, 75 GPLLJs are simulated at 9-km resolution both with and without NASA Soil Moisture Active Passive SM DA. Differences in modeled SM, surface sensible (SH) and latent heat (LH) fluxes, 2-m temperature (T2), 2-m humidity (Q2), PBL height (PBLH), and 850-hPa wind speed (W850) are quantified for individual jets and jet-type event subsets over the south-central Great Plains, as well as separately for each GPLLJ sector (entrance, core, and exit). At the GPLLJ core, DA-related changes of up to 5.4 kg m−2 in SM can result in T2, Q2, LH, SH, PBLH, and W850 differences of 0.68°C, 0.71 g kg−2, 59.9 W m−2, 52.4 W m−2, 240 m, and 4 m s−1, respectively. W850 differences focus along the jet axis and tend to increase from south to north. Jet-type differences are most evident at the GPLLJ exit where DA increases and decreases W850 in uncoupled and coupled GPLLJs, respectively. Data assimilation marginally reduces negative wind speed bias for all jets, but the correction is greater for uncoupled GPLLJs, as hypothesized.

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