An Overview of the International H2O Project (IHOP_2002) and Some Preliminary Highlights

The International H2O Project (IHOP_2002) is one of the largest North American meteorological field experiments in history. From 13 May to 25 June 2002, over 250 researchers and technical staff from the United States, Germany, France, and Canada converged on the Southern Great Plains to measure water vapor and other atmospheric variables. The principal objective of IHOP_2002 is to obtain an improved characterization of the time-varying three-dimensional water vapor field and evaluate its utility in improving the understanding and prediction of convective processes. The motivation for this objective is the combination of extremely low forecast skill for warm-season rainfall and the relatively large loss of life and property from flash floods and other warm-season weather hazards. Many prior studies on convective storm forecasting have shown that water vapor is a key atmospheric variable that is insufficiently measured. Toward this goal, IHOP_2002 brought together many of the existing operational and new state-of-the-art research water vapor sensors and numerical models. The IHOP_2002 experiment comprised numerous unique aspects. These included several instruments fielded for the first time (e.g., reference radiosonde); numerous upgraded instruments (e.g., Wyoming Cloud Radar); the first ever horizontal-pointing water vapor differential absorption lidar (DIAL; i.e., Leandre II on the Naval Research Laboratory P-3), which required the first onboard aircraft avoidance radar; several unique combinations of sensors (e.g., multiple profiling instruments at one field site and the German water vapor DIAL and NOAA/Environmental Technology Laboratory Doppler lidar on board the German Falcon aircraft); and many logistical challenges. This article presents a summary of the motivation, goals, and experimental design of the project, illustrates some preliminary data collected, and includes discussion on some potential operational and research implications of the experiment.

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Convection Initiation Caused by Heterogeneous Low-Level Jets over the Great Plains

Monthly Weather Review ◽

10.1175/mwr-d-18-0002.1 ◽

2018 ◽

Vol 146 (8) ◽

pp. 2615-2637 ◽

Cited By ~ 17

Author(s):

Joshua G. Gebauer ◽

Alan Shapiro ◽

Evgeni Fedorovich ◽

Petra Klein

Keyword(s):

Great Plains ◽

Three Dimensional ◽

Warm Season ◽

The United States ◽

Dimensional Structure ◽

Nonuniform Heating ◽

Low Level ◽

Low Level Jets ◽

Convection Initiation ◽

Capping Inversion

AbstractObservations from three nights of the Plains Elevated Convection at Night (PECAN) field campaign were used in conjunction with Rapid Refresh model forecasts to find the cause of north–south lines of convection, which initiated away from obvious surface boundaries. Such pristine convection initiation (CI) is relatively common during the warm season over the Great Plains of the United States. The observations and model forecasts revealed that all three nights had horizontally heterogeneous and veering-with-height low-level jets (LLJs) of nonuniform depth. The veering and heterogeneity were associated with convergence at the top-eastern edge of the LLJ, where moisture advection was also occurring. As time progressed, this upper region became saturated and, due to its placement above the capping inversion, formed moist absolutely unstable layers, from which the convergence helped initiate elevated convection. The structure of the LLJs on the CI nights was likely influenced by nonuniform heating across the sloped terrain, which led to the uneven LLJ depth and contributed toward the wind veering with height through the creation of horizontal buoyancy gradients. These three CI events highlight the importance of assessing the full three-dimensional structure of the LLJ when forecasting nocturnal convection over the Great Plains.

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Irrigation Effects on Land–Atmosphere Coupling Strength in the United States

Journal of Climate ◽

10.1175/jcli-d-15-0706.1 ◽

2017 ◽

Vol 30 (10) ◽

pp. 3671-3685 ◽

Cited By ~ 10

Author(s):

Yaqiong Lu ◽

Keith Harding ◽

Lara Kueppers

Keyword(s):

United States ◽

Soil Moisture ◽

Water Vapor ◽

Great Plains ◽

Coupling Strength ◽

Climate Models ◽

The United States ◽

Lower Sensitivity ◽

Local Soil ◽

Irrigation Effects

Abstract Land–atmosphere coupling strength describes the degree to which the atmosphere responds (e.g., via changes in precipitation) to changes in the land surface state (e.g., soil moisture). The Midwest and Great Plains of the United States have been shown to be “hot spots” of coupling by many climate models and some observations. However, very few of the modeling studies have reported whether the climate models applied irrigation in the Midwest and Great Plains, where 24%–27% of farmland is irrigated, leaving open the question of whether irrigation affects current estimates of coupling strength. This study used a regional climate model that incorporated dynamic crop growth and precision irrigation (WRF3.3–CLM4crop) to investigate irrigation effects on land–atmosphere coupling strength. Coupling strength was quantified using multiple indices and the irrigated land-induced precipitation was tracked using a back trajectory method. The indices showed a consistent and significant decline in local coupling strength with irrigation in the Midwest and northern Great Plains. These reductions were due to increased soil moisture but decreased local precipitation and lower sensitivity of latent heat flux to soil moisture over irrigated regions. The back trajectories of water vapor transport confirmed that irrigation largely did not contribute to local precipitation. Water vapor from irrigated land was transported to the Midwest and U.S. Northeast where it fell as precipitation, suggesting that irrigation has a broader spatial impact on soil moisture–precipitation coupling than simply through local soil moisture–evapotranspiration coupling. The present study suggests that climate models without irrigation schemes may overestimate the land–atmosphere coupling strength over irrigated agricultural regions but underestimate coupling strength over neighboring nonirrigated regions.

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Interspecific Hybridization: Potential for Movement of Herbicide Resistance from Wheat to Jointed Goatgrass (Aegilops cylindrica)

Weed Technology ◽

10.1614/wt-04-217r.1 ◽

2005 ◽

Vol 19 (3) ◽

pp. 674-682 ◽

Cited By ~ 28

Author(s):

Bradley D. Hanson ◽

Carol A. Mallory-Smith ◽

William J. Price ◽

Bahman Shafii ◽

Donald C. Thill ◽

...

Keyword(s):

Pacific Northwest ◽

Great Plains ◽

Herbicide Resistance ◽

Field Experiments ◽

Introgressive Hybridization ◽

Acetolactate Synthase ◽

The United States ◽

Aegilops Cylindrica ◽

Herbicide Resistant ◽

Jointed Goatgrass

The transfer of herbicide resistance genes from crops to related species is one of the greatest risks of growing herbicide-resistant crops. The recent introductions of imidazolinone-resistant wheat in the Great Plains and Pacific Northwest regions of the United States and research on transgenic glyphosate-resistant wheat have raised concerns about the transfer of herbicide resistance from wheat to jointed goatgrass via introgressive hybridization. Field experiments were conducted from 2000 to 2003 at three locations in Washington and Idaho to determine the frequency and distance that imidazolinone-resistant wheat can pollinate jointed goatgrass and produce resistant F1hybrids. Each experiment was designed as a Nelder wheel with 16 equally spaced rays extending away from a central pollen source of ‘Fidel-FS4’ imidazolinone-resistant wheat. Each ray was 46 m long and contained three rows of jointed goatgrass. Spikelets were collected at maturity at 1.8-m intervals along each ray and subjected to an imazamox screening test. The majority of all jointed goatgrass seeds tested were not resistant to imazamox; however, 5 and 15 resistant hybrids were found at the Pullman, WA, and Lewiston, ID, locations, respectively. The resistant plants were identified at a maximum distance of 40.2 m from the pollen source. The overall frequency of imazamox-resistant hybrids was similar to the predicted frequency of naturally occurring acetolactate synthase resistance in weeds; however, traits with a lower frequency of spontaneous mutations may have a relatively greater risk for gene escape via introgressive hybridization.

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The diminishing contribution of low-level jets to the U.S. Great Plains water budget

10.5194/egusphere-egu21-7017 ◽

2021 ◽

Author(s):

Craig R. Ferguson

Keyword(s):

Water Vapor ◽

Great Plains ◽

Water Budget ◽

Structural Changes ◽

Warm Season ◽

Water Vapor Transport ◽

Northern Great Plains ◽

Wind Maximum ◽

Low Level ◽

Low Level Jets

<p>In the semi-arid U.S. Great Plains, nocturnal southerly low-level jets (LLJs) serve critical roles as conveyors of remotely-sourced (i.e., Gulf of Mexico) water vapor and agents of atmospheric instability in the warm-season. &#160;Defined by a diurnally oscillating wind maximum between 0&#8211;3 km above the surface, LLJs have been studied by meteorologists for over 60-years due to their role in severe weather outbreaks. It is only within the past decade that a subset of LLJs with especially high vertically integrated water vapor transport, termed atmospheric rivers, have drawn the attention of hydrologists.</p><p>In this study, changes in LLJ frequency and structure over the period from 1901&#8211;2010 are quantified using ECMWF&#8217;s Coupled Reanalysis of the Twentieth Century (CERA-20C). A new objective dynamical LLJ classification dataset is used to separately quantify changes in the two predominant LLJ types: synoptically coupled and uncoupled. The findings reveal that both the frequency of Great Plains LLJs and their associated precipitation have decreased significantly over the 20th century. Decreases in LLJ associated precipitation range between 10&#8211;14% of total present day May&#8211;September precipitation. The largest differences observed are attributable to uncoupled jet frequency and structural changes during July and August over the central and northern Great Plains. Overall, the results indicate the contribution of LLJs to the region&#8217;s water budget has diminished.</p>

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An Intercomparison and Validation of High-Resolution Satellite Precipitation Estimates with 3-Hourly Gauge Data

Journal of Hydrometeorology ◽

10.1175/2008jhm1052.1 ◽

2009 ◽

Vol 10 (1) ◽

pp. 149-166 ◽

Cited By ~ 258

Author(s):

M. R. P. Sapiano ◽

P. A. Arkin

Keyword(s):

United States ◽

High Resolution ◽

Pacific Ocean ◽

Information Service ◽

Warm Season ◽

The United States ◽

Naval Research ◽

General Tendency ◽

Validation Data ◽

Gauge Data

Abstract The last several years have seen the development of a number of new satellite-derived, globally complete, high-resolution precipitation products with a spatial resolution of at least 0.25° and a temporal resolution of at least 3-hourly. These products generally merge geostationary infrared data and polar-orbiting passive microwave data to take advantage of the frequent sampling of the infrared and the superior quality of the microwave. The Program to Evaluate High Resolution Precipitation Products (PEHRPP) was established to evaluate and intercompare these datasets at a variety of spatial and temporal resolutions with the intent of guiding dataset developers and informing the user community regarding the error characteristics of the products. As part of this project, the authors have performed a subdaily intercomparison of five high-resolution datasets [Climate Prediction Center morphing (CMORPH) technique; Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis (TMPA); Naval Research Laboratory (NRL) blended technique; National Environmental Satellite, Data, and Information Service Hydro-Estimator; and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN)] with existing subdaily gauge data over the United States and the Pacific Ocean. Results show that these data are effective at representing high-resolution precipitation, with correlations against 3-hourly gauge data as high as 0.7 for CMORPH, which had the highest correlations with the validation data. Biases are relatively high for most of the datasets over land (apart from the TMPA, which is gauge adjusted) and ocean, with a general tendency to overestimate warm season rainfall over the United States and to underestimate rainfall over the tropical Pacific Ocean. Additionally, all the products studied faithfully resolve the diurnal cycle of precipitation when compared with the validation data.

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

Monthly Weather Review ◽

10.1175/mwr-d-18-0040.1 ◽

2018 ◽

Vol 146 (9) ◽

pp. 3053-3078 ◽

Cited By ~ 7

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.

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Tropopause-Penetrating Convection from Three-Dimensional Gridded NEXRAD Data

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-15-0190.1 ◽

2016 ◽

Vol 55 (2) ◽

pp. 465-478 ◽

Cited By ~ 16

Author(s):

David L. Solomon ◽

Kenneth P. Bowman ◽

Cameron R. Homeyer

Keyword(s):

United States ◽

Three Dimensional ◽

Warm Season ◽

The United States ◽

Lapse Rate ◽

High Plains ◽

Annual Cycles ◽

Weather Radars ◽

The North ◽

The Stability

AbstractA new method that combines radar reflectivities from individual Next Generation Weather Radars (NEXRAD) into a three-dimensional composite with high horizontal and vertical resolution is used to estimate storm-top altitudes for the continental United States east of the Rocky Mountains. Echo-top altitudes are compared with the altitude of the lapse-rate tropopause calculated from the ERA-Interim reanalysis and radiosondes. To sample the diurnal and annual cycles, tropopause-penetrating convection is analyzed at 3-h intervals throughout 2004. Overshooting convection is most common in the north-central part of the United States (the high plains). There is a pronounced seasonal cycle; the majority of overshooting systems occur during the warm season (March–August). There is also a strong diurnal cycle, with maximum overshooting occurring near 0000 UTC. The overshooting volume decreases rapidly with height above the tropopause. Radiosonde observations are used to evaluate the quality of the reanalysis tropopause altitudes and the dependence of overshooting depth on environmental characteristics. The radar–radiosonde comparison reveals that overshooting is deeper in double-tropopause environments and increases as the stability of the lower stratosphere decreases.

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Climatology of Linear Mesoscale Convective System Morphology in the United States based on Random Forests Method

Journal of Climate ◽

10.1175/jcli-d-20-0862.1 ◽

2021 ◽

pp. 1-52

Author(s):

Wenjun Cui ◽

Xiquan Dong ◽

Baike Xi ◽

Zhe Feng

Keyword(s):

United States ◽

Great Plains ◽

Warm Season ◽

Mesoscale Convective System ◽

Propagation Speed ◽

Extreme Rainfall ◽

The United States ◽

Convective System ◽

Large Variability ◽

Mesoscale Convective

AbstractThis study uses machine learning methods, specifically the random forest (RF), on a radar-based mesoscale convective system (MCS) tracking dataset to classify the five types of linear MCS morphology in the contiguous United States during the period 2004-2016. The algorithm is trained using radar- and satellite-derived spatial and morphological parameters, and reanalysis environmental information from 5-yr manually identified nonlinear and five linear MCS modes. The algorithm is then used to automate the classification of linear MCSs over 8 years with high accuracy, providing a systematic, long-term climatology of linear MCSs. Results reveal that nearly 40% of MCSs are classified as linear MCSs, in which half of the linear events belong to the type of system having a leading convective line. The occurrence of linear MCSs shows large annual and seasonal variations. On average, 113 linear MCSs occur annually during the warm season (through March to October), with most of these events clustered from May through August in the central eastern Great Plains. MCS characteristics, including duration, propagation speed, orientation, and system cloud size, have large variability among the different linear modes. The systems having a trailing convective line and the systems having a back-building area of convection typically move more slowly and have higher precipitation rate, and thus have higher potential in producing extreme rainfall and flash flooding. Analysis of the environmental conditions associated with linear MCSs show that the storm-relative flow is of most importance in determining the organization mode of linear MCSs.

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Sensitivity to Horizontal Resolution in the AGCM Simulations of Warm Season Diurnal Cycle of Precipitation over the United States and Northern Mexico

Journal of Climate ◽

10.1175/jcli4090.1 ◽

2007 ◽

Vol 20 (9) ◽

pp. 1862-1881 ◽

Cited By ~ 76

Author(s):

Myong-In Lee ◽

Siegfried D. Schubert ◽

Max J. Suarez ◽

Isaac M. Held ◽

Arun Kumar ◽

...

Keyword(s):

Great Plains ◽

Diurnal Cycle ◽

North American ◽

General Circulation ◽

Warm Season ◽

The United States ◽

Horizontal Resolution ◽

Moist Convection ◽

The North ◽

Diurnal Cycle Of Precipitation

Abstract This study examines the sensitivity of the North American warm season diurnal cycle of precipitation to changes in horizontal resolution in three atmospheric general circulation models, with a primary focus on how the parameterized moist processes respond to improved resolution of topography and associated local/regional circulations on the diurnal time scale. It is found that increasing resolution (from approximately 2° to ½° in latitude–longitude) has a mixed impact on the simulated diurnal cycle of precipitation. Higher resolution generally improves the initiation and downslope propagation of moist convection over the Rockies and the adjacent Great Plains. The propagating signals, however, do not extend beyond the slope region, thereby likely contributing to a dry bias in the Great Plains. Similar improvements in the propagating signals are also found in the diurnal cycle over the North American monsoon region as the models begin to resolve the Gulf of California and the surrounding steep terrain. In general, the phase of the diurnal cycle of precipitation improves with increasing resolution, though not always monotonically. Nevertheless, large errors in both the phase and amplitude of the diurnal cycle in precipitation remain even at the highest resolution considered here. These errors tend to be associated with unrealistically strong coupling of the convection to the surface heating and suggest that improved simulations of the diurnal cycle of precipitation require further improvements in the parameterizations of moist convection processes.

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