scholarly journals Observational Evidence of State‐Dependent Positive and Negative Land Surface Feedback on Afternoon Deep Convection Over the Southern Great Plains

2020 ◽  
Vol 47 (5) ◽  
Author(s):  
Shaoyue Qiu ◽  
Ian N. Williams
Keyword(s):  
Great Plains ◽  
Land Surface ◽  
Deep Convection ◽  
Observational Evidence ◽  
Southern Great Plains ◽  
State Dependent

scholarly journals Summertime Continental Shallow Cumulus Cloud Detection Using GOES-16 Satellite and Ground-Based Stereo Cameras at the DOE ARM Southern Great Plains Site

2021 ◽  
Vol 13 (12) ◽  
pp. 2309
Author(s):  
Jingjing Tian ◽  
Yunyan Zhang ◽  
Stephen A. Klein ◽  
Likun Wang ◽  
Rusen Öktem ◽  
...  
Keyword(s):  
Great Plains ◽  
Land Surface ◽  
Detection Threshold ◽  
Department Of Energy ◽  
Surface Reflectance ◽  
Cloud Detection ◽  
Southern Great Plains ◽  
Clear Sky ◽  
Shallow Cumulus ◽  
Stereo Cameras

Summertime continental shallow cumulus clouds (ShCu) are detected using Geostationary Operational Environmental Satellite (GOES)-16 reflectance data, with cross-validation by observations from ground-based stereo cameras at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains site. A ShCu cloudy pixel is identified when the GOES reflectance exceeds the clear-sky surface reflectance by a reflectance detection threshold of ShCu, ΔR. We firstly construct diurnally varying clear-sky surface reflectance maps and then estimate the ∆R. A GOES simulator is designed, projecting the clouds reconstructed by stereo cameras towards the surface along the satellite’s slanted viewing direction. The dynamic ShCu detection threshold ΔR is determined by making the GOES cloud fraction (CF) equal to the CF from the GOES simulator. Although there are temporal variabilities in ΔR, cloud fractions and cloud size distributions can be well reproduced using a constant ΔR value of 0.045. The method presented in this study enables daytime ShCu detection, which is usually falsely reported as clear sky in the GOES-16 cloud mask data product. Using this method, a new ShCu dataset can be generated to bridge the observational gap in detecting ShCu, which may transition into deep precipitating clouds, and to facilitate further studies on ShCu development over heterogenous land surface.

scholarly journals Mechanisms of Seasonal Soil Moisture Drought Onset and Termination in the Southern Great Plains

2019 ◽  
Vol 20 (4) ◽  
pp. 751-771 ◽  
Author(s):  
Richard Seager ◽  
Jennifer Nakamura ◽  
Mingfang Ting
Keyword(s):  
Soil Moisture ◽  
North America ◽  
Great Plains ◽  
Land Surface ◽  
Tropical Pacific ◽  
Moisture Change ◽  
Southern Plains ◽  
Southern Great Plains ◽  
Continental Scale ◽  
Over Time

AbstractMechanisms of drought onset and termination are examined across North America with a focus on the southern Plains using data from land surface models and regional and global reanalyses for 1979–2017. Continental-scale analysis of covarying patterns reveals a tight coupling between soil moisture change over time and intervening precipitation anomalies. The southern Great Plains are a geographic center of patterns of hydrologic change. Drying is induced by atmospheric wave trains that span the Pacific and North America and place northerly flow anomalies above the southern Plains. In the southern Plains winter is least likely, and fall most likely, for drought onset and spring is least likely, and fall or summer most likely, for drought termination. Southern Plains soil moisture itself, which integrates precipitation over time, has a clear relationship to tropical Pacific sea surface temperature (SST) anomalies with cold conditions favoring dry soils. Soil moisture change, however, though clearly driven by precipitation, has a weaker relation to SSTs and a strong relation to internal atmospheric variability. Little evidence is found of connection of drought onset and termination to driving by temperature anomalies. An analysis of particular drought onsets and terminations on the seasonal time scale reveals commonalities in terms of circulation and moisture transport anomalies over the southern Plains but a variety of ways in which these are connected into the large-scale atmosphere and ocean state. Some onsets are likely to be quite predictable due to forcing by cold tropical Pacific SSTs (e.g., fall 2010). Other onsets and all terminations are likely not predictable in terms of ocean conditions.

Bores Observed during IHOP_2002: The Relationship of Bores to the Nocturnal Environment

2017 ◽  
Vol 145 (10) ◽  
pp. 3929-3946 ◽  
Author(s):  
Kevin R. Haghi ◽  
David B. Parsons ◽  
Alan Shapiro
Keyword(s):  
Great Plains ◽  
Deep Convection ◽  
Horizontal Wind ◽  
Wave Trapping ◽  
Southern Great Plains ◽  
Direction Of Movement ◽  
Low Level Jet ◽  
Relationship Of ◽  
The Relationship ◽  
Scorer Parameter

This study documents atmospheric bores and other convergent boundaries in the southern Great Plains’ nocturnal environment during the IHOP_2002 summer campaign. Observational evidence demonstrates that convective outflows routinely generate bores. Statistically resampled flow regimes, derived from an adaptation of hydraulic theory, agree well with observations. Specifically, convective outflows within the observed environments are likely to produce a partially blocked flow regime, which is a favorable condition for generating a bore. Once a bore develops, the direction of movement generally follows the orientation of the bulk shear vector between the nose of the nocturnal low-level jet and a height of 1.5 or 2.5 km AGL. This relationship is believed to be a consequence of wave trapping through the curvature of the horizontal wind with respect to height. This conclusion comes after analyzing the profile of the Scorer parameter. Overall, these findings provide an impetus for future investigations aimed at understanding and predicting nocturnal deep convection over this region.

scholarly journals Coupling between Large-Scale Atmospheric Processes and Mesoscale Land–Atmosphere Interactions in the U.S. Southern Great Plains during Summer. Part I: Case Studies

2004 ◽  
Vol 5 (6) ◽  
pp. 1223-1246 ◽  
Author(s):  
Christopher P. Weaver
Keyword(s):  
Great Plains ◽  
Large Scale ◽  
Deep Convection ◽  
Individual Case ◽  
Atmospheric Modeling ◽  
Surface Fluxes ◽  
Southern Great Plains ◽  
Atmospheric Processes ◽  
Mesoscale Processes

Abstract This paper is Part I of a two-part study that uses high-resolution Regional Atmospheric Modeling System (RAMS) simulations to investigate mesoscale land–atmosphere interactions in the summertime U.S. Southern Great Plains. The focus is on the atmospheric dynamics associated with mesoscale heterogeneity in the underlying surface fluxes: how shifts in meteorological regimes modulate these diurnal, mesoscale processes, and their overall impact at larger scales and over multiple diurnal cycles. Part I examines individual case study time periods drawn from the simulations that illustrate general points about the key land–atmosphere interactions. The main findings are as follows: The mesoscale processes are embedded within a synoptic-scale organization that controls the background meteorological regime at a given location. During the clear, dry days in the simulated months, heterogeneity in the surface fluxes forces strong, lower-tropospheric, mesoscale circulations that exhibit a characteristic dynamical life cycle over diurnal time scales. In general, the background large-scale flow does not affect the overall intensity of these coherent roll structures, though strong large-scale subsidence can sometimes dampen them. In addition, depending on the thermodynamic profile, the strong vertical motions associated with these circulations are sufficient to trigger shallow or even deep convection, with associated clouds and precipitation. Furthermore, surface heterogeneity sufficient to force such circulations can arise even without heterogeneity in preexisting land cover characteristics such as vegetation, for example, solely as a result of spatial variability in rainfall and other atmospheric processes. In Part II the mesoscale land–atmosphere interactions in these case study periods are placed in the larger context of the full, monthlong simulations.

scholarly journals Estimación de la evapotranspiración real en zonas de llanura mediante productos de humedad de suelo de la misión SMAP

2018 ◽  
pp. 17
Author(s):  
E. Walker ◽  
G. A. García ◽  
V. Venturini
Keyword(s):  
Great Plains ◽  
Land Surface ◽  
Water Cycle ◽  
Coefficient Of Determination ◽  
Southern Great Plains ◽  
Passive Sensors ◽  
New Equation ◽  
Humid Period ◽  
Pampas Region

<p>Evapotranspiration (ET) is an important process in the water cycle and in the land-surface energy balance. Over the last decades, remote sensing has provided valuable information to quantify ET. However, methodologies that use data from microwave passive sensors, such as “Soil Moisture Active Passive” (SMAP) mission, have been recently developed. In this work, a formulation to derive the relative evapotranspiration and ET from <em>in situ</em> and microwave data, is presented. The methodology is based on a modification of the original Komatsu (2003) equation by introducing a calibration parameter to represent the wind speed and vegetation effects and estimate the relative evapotranspiration. This new equation was used on the Bouchet’s complementary relationship with the Priestley-Taylor’s equation, to estimate ET at regional scales. The results were compared with observed data in the Southern Great Plains – USA (SGP) area, indicating that the new model estimated ET with a root mean square error (RMSE) of 0.88 mmd<sup>–1</sup> and a coefficient of determination (R<sup>2</sup> ) greater than 0.8. The calibrated model was applied in an extremely humid period in Argentinean Pampas region with results near to potential rates.</p>

scholarly journals Characteristics and Synoptic Environment of Drylines Occurring over the Higher Terrain of Southeastern Wyoming

2015 ◽  
Vol 30 (6) ◽  
pp. 1733-1748 ◽  
Author(s):  
Philip T. Bergmaier ◽  
Bart Geerts
Keyword(s):  
Great Plains ◽  
Rocky Mountains ◽  
Deep Convection ◽  
Potential Temperature ◽  
Warm Season ◽  
Thunderstorm Activity ◽  
Southern Great Plains ◽  
Synoptic Conditions ◽  
Virtual Potential Temperature ◽  
Close Relationship

Abstract Commonly observed over the broadly sloped terrain of the southern Great Plains (SGP), drylines are frequent loci of warm season deep convection and have been the focus of numerous observational, theoretical, and climatological studies over last half century. In this study, a 3-yr (2010–12) analysis of the characteristics and synoptic environment of drylines occurring elsewhere, over the high terrain in southeastern Wyoming just east of the Rocky Mountains, is presented. Observed on ~11% of the days between May and August of the years examined, southeastern Wyoming drylines were often associated with large moisture gradients [~5–10 g kg−1 (100 km)−1], large horizontal virtual potential temperature differences (~2–5 K), and convergent zonal wind flow at the surface. The synoptic conditions leading to their formation and their relationship to thunderstorm activity are also explored in an effort to aid local forecasters in anticipating the development and convective impact of drylines across the region. Similarities exist between these drylines and those found over the SGP, especially with regard to their strength and close relationship to deep convection. However, the frequency at which they occur, some characteristics of their diurnal motion, and the synoptic conditions driving their formation differ noticeably.

scholarly journals Monitoring Drought over the Conterminous United States Using MODIS and NCEP Reanalysis-2 Data

2010 ◽  
Vol 49 (8) ◽  
pp. 1665-1680 ◽  
Author(s):  
Yunjun Yao ◽  
Shunlin Liang ◽  
Qiming Qin ◽  
Kaicun Wang
Keyword(s):  
United States ◽  
Spatial Resolution ◽  
Great Plains ◽  
Land Surface ◽  
Remote Sensing Data ◽  
Moisture Stress ◽  
Ncep Reanalysis ◽  
Southern Great Plains ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Monitoring land surface drought using remote sensing data is a challenge, although a few methods are available. Evapotranspiration (ET) is a valuable indicator linked to land drought status and plays an important role in surface drought detection at continental and global scales. In this study, the evaporative drought index (EDI), based on the estimated actual ET and potential ET (PET), is described to characterize the surface drought conditions. Daily actual ET at 4-km resolution for April–September 2003–05 across the continental United States is estimated using a simple improved ET model with input solar radiation acquired by Moderate-Resolution Imaging Spectroradiometer (MODIS) at a spatial resolution of 4 km and input meteorological parameters from NCEP Reanalysis-2 data at a spatial resolution of 32 km. The PET is also calculated using some of these data. The estimated actual ET has been rigorously validated with ground-measured ET at six Enhanced Facility sites in the Southern Great Plains (SGP) of the Atmosphere Radiation Measurement Program (ARM) and four AmeriFlux sites. The validation results show that the bias varies from −11.35 to 27.62 W m−2 and the correlation coefficient varies from 0.65 to 0.86. The monthly composites of EDI at 4-km resolution during April–September 2003–05 are found to be in good agreement with the Palmer Z index anomalies, but the advantage of EDI is its finer spatial resolution. The EDI described in this paper incorporates information about energy fluxes in response to soil moisture stress without requiring too many meteorological input parameters, and performs well in assessing drought at continental scales.

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