Steven A. Rutledge

• Colorado State University

Statistical analyses of a large disdrometer data set and a diverse set of model simulations for convection using the Regional Atmospheric Modeling System were conducted, with the mutual goal of providing insights into precipitation formation and microphysical processes. We demonstrate that a two‐moment bulk microphysical model successfully captures...

This study evaluates rainfall, cloudiness, and related fields in the European Centre for Medium-Range Weather Forecast 5 th generation climate reanalysis (ERA5) and the National Aeronautics and Space Administration’s Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) gridded global reanalysis products against obser...

An intercomparison of rain drop mean diameter frequency distribution (RDFD) is performed for numerical simulations of precipitating cloud systems using an array of models and microphysics schemes. This includes results from the Regional Atmospheric Modeling System (RAMS) double-moment microphysics, the Hebrew University Cloud Model bin microphysics...

Isolated warm-rain cells are an important feature over the tropical oceans. Although warm rain is typically associated with relatively small raindrops, large raindrops (> 4.5 mm in diameter) have been observed in some cases. Previous studies have examined warm rain cells with large drops on a case-study basis, but they have yet to be investigated i...

Orographic precipitation results from complex interactions between terrain, large-scale flow, turbulent motions, and microphysical processes. This study appeals to polarimetric radar data in conjunction with surface-based disdrometer observations, airborne particle probes, and reanalysis data to study these processes and their interactions as obser...

Plain Language Summary Several distinct classes of high peak‐current lightning processes are known to occur in thunderstorms, such as cloud‐to‐ground (CG) strokes, narrow bipolar events (NBEs), and the recently revealed energetic in‐cloud pulses (EIPs). Here, we report on another type of high‐amplitude event that is generated almost always over mou...

The Propagation of Intraseasonal Oscillations (PISTON) field campaign took place in the waters of the western tropical North Pacific during the late-summer and early-fall of 2018 and 2019. During both research cruises, the Colorado State University SEA-POL polarimetric C-Band weather radar obtained continuous 3D measurements of oceanic precipitatio...

Using 17-yr spaceborne precipitation radar measurements, this study investigates how diurnal cycles of rainfall and convective characteristics over the South China Sea region are modulated by the boreal summer intraseasonal oscillation (BSISO). Generally, diurnal cycles change significantly between suppressed and active BSISO periods. Over the Phil...

During the boreal summer, satellite-based precipitation estimates indicate a distinct maximum in rainfall off the west coast of the island of Luzon in the Philippines. Also occurring during the summer months is the Boreal Summer Intraseasonal Oscillation (BSISO), a main driver of intraseasonal variability in the region. This study investigates the...

This study contrasts midlatitude continental and tropical maritime deep convective cores using polarimetric radar observables and retrievals from selected deep convection episodes during the MC3E and TWPICE field campaigns. The continental convective cores produce stronger radar reflectivities throughout the profiles, while maritime convective core...

Production and transport of NOx by convection is critical as it serves as a precursor to tropospheric ozone, an important greenhouse gas. Lightning serves as the largest source of nitrogen oxides (NOx = NO + NO2) to the upper troposphere (UT) and is one of the largest natural sources of NOx. Interest is placed on the vertical advection of NOx becau...

The Deep Convective Clouds and Chemistry (DC3) project aimed to determine the impact of deep, midlatitude continental convective clouds on tropospheric composition and chemistry. The DC3 field campaign was conducted over a broad area of the central United States during May–June 2012. Data collected by DC3 have been extensively analyzed, with many r...

A new, advanced radar has been developed at Colorado State University (CSU). The Sea-Going Polarimetric (SEA-POL) radar is a C-band, polarimetric Doppler radar specifically designed to deploy on research ships. SEA-POL is the first such weather radar developed in the United States. Ship-based weather radars have a long history, dating back to GATE...

Using lightning data from the World Wide Lightning Location Network, infrared satellite imagery, and microwave observations, this study investigates lightning outbreaks and convective evolution in the inner core (0–100 km) of Super Typhoon Haiyan (2013), the strongest storm on record to make landfall in the northwest Pacific. This storm was charact...

This paper introduces a synthetic polarimetric radar simulator and retrieval package, POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS), for evaluating cloud‐resolving models (CRMs). POLARRIS is composed of forward (POLARRIS‐f) and inverse (retrieval and diagnostic) components (iPOLARRIS) to generate not only polarimetric radar obser...

Stratification of the upper few meters of the ocean limits the penetration depth of wind mixing and the vertical distribution of atmospheric fluxes. Significant density stratification at depths ≤ 5 m was observed in 38% of a 2‐month data set from the central Indian Ocean collected during the DYNAMO experiment (Dynamics of the MJO, Madden‐Julian Osc...

This study describes the generation and testing of a reference rainfall product created from field campaign datasets collected during the NASA Global Precipitation Measurement (GPM) mission Ground Validation Iowa Flood Studies (IFloodS) experiment. The study evaluates ground-based radar rainfall (RR) products acquired during IFloodS in the context...

Microphysical and kinematic characteristics of two storm populations, based on their macroscale charge structures, are investigated in an effort to increase our understanding of the processes that lead to anomalous (or inverted charge) structures. Nine normal polarity cases (midlevel negative charge) with dual-Doppler and polarimetric coverage that...

Using lightning mapping arrays (LMAs), lightning flash locations in three dimensions have been investigated using multiple methods. Approximately 500,000 flashes were analyzed to reveal the variability of lightning channel locations within convective storms. These flashes were produced by over 4000 isolated convective storms during one warm season...

Dual-polarization radar rainfall estimation relationships have been extensively tested in continental and subtropical coastal rain regimes, with little testing over tropical oceans where the majority of rain on Earth occurs. A 1.5-yr Indo-Pacific warm pool disdrometer dataset was used to quantify the impacts of tropical oceanic drop-size distributi...

The objective of this study is to determine the relative contributions of normalized CAPE (NCAPE), cloud condensation nuclei (CCN) concentrations, warm cloud depth (WCD), vertical wind shear (SHEAR), and environmental relative humidity (RH) to the variability of lightning and radar reflectivity within convective features (CFs) observed by the Tropi...

The Olympic Mountains Experiment (OLYMPEX) took place during the 2015/16 fall–winter season in the vicinity of the mountainous Olympic Peninsula of Washington State. The goals of OLYMPEX were to provide physical and hydrologic ground validation for the U.S.–Japan Global Precipitation Measurement (GPM) satellite mission and, more specifically, to st...

This study examines covariability of boundary layer cloud condensation nuclei (CCN) concentrations (estimated using the GEOS-Chem transport model), convective clouds, precipitation, and lightning observed over the central equatorial Indian Ocean (CIO). Three distinct Madden-Julian Oscillation (MJO) episodes were observed during the recent Dynamics...

Two sprite-producing thunderstorms were observed on 8 and 25 June 2012 in northeastern Colorado by a combination of low-light cameras, a lightning mapping array, polarimetric and Doppler radars, the National Lightning Detection Network, and charge moment change measurements. The 8 June event evolved from a tornadic hailstorm to a larger multicellul...

Approximately 63 million lightning flashes have been identified and analyzed from multiple years of Washington DC, northern Alabama, and northeast Colorado lightning mapping array (LMA) data using an open-source flash-clustering algorithm. LMA networks detect radiation produced by lightning breakdown processes, allowing for high resolution mapping...

We have developed semi-independent methods for determining CH2O scavenging efficiencies (SEs) during strong midlatitude convection over the western, south-central Great Plains, and southeastern regions of the United States during the 2012 Deep Convective Clouds and Chemistry (DC3) Study. The Weather Research and Forecasting model coupled with chemi...

This study statistically investigates the timing and underlying processes of the shallow-to-deep convective transition (SDT) associated with MJO initiation over the Indian Ocean. Results show that SDT periods have a median value of 8-10 days with a wide spectrum of 2-20 days. SDTs lasting 10-20 days occurred nearly 50% of the time, consistent with...

Thunderstorm anvils were studied during the Deep Convective Clouds and Chemistry experiment (DC3), using in situ measurements and observations of ice particles and NOx together with radar and Lightning Mapping Array measurements. A characteristic ice particle and NOx signature was found in the anvils from three storms, each containing high lightnin...

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission, was conducted in south-central Oklahoma during April–May 2011....

The variability of precipitation and water supply along the U.S. West Coast creates major challenges to the region’s economy and environment, as evidenced by the recent California drought. This variability is strongly influenced by atmospheric rivers (ARs), which deliver much of the precipitation along the U.S. West Coast and can cause flooding, an...

During the second week of September 2013, a seasonally uncharacteristic weather pattern stalled over the Rocky Mountain Front Range region of northern Colorado bringing with it copious amounts of moisture from the Gulf of Mexico, Caribbean Sea, and the tropical eastern Pacific Ocean. This feed of moisture was funneled toward the east-facing mountai...

The Deep Convective Clouds and Chemistry (DC3) field experiment produced an exceptional dataset on thunderstorms, including their dynamical, physical, and electrical structures and their impact on the chemical composition of the troposphere. The field experiment gathered detailed information on the chemical composition of the inflow and outflow reg...

Two-dimensional video disdrometer (2DVD) data were analyzed from two equatorial Indian (Gan) and west Pacific Ocean (Manus) islands where precipitation is primarily organized by the intertropical convergence zone and the Madden–Julian oscillation (MJO). The 18 (3.5) months of 2DVD data from Manus (Gan) Island show that 1) the two sites have similar...

A database consisting of approximately 4000 storm observations has been objectively analyzed to determine environmental characteristics that produce high radar reflectivities above the freezing level, large total lightning flash rates on the order of 10 flashes per minute, and anomalous vertical charge structures (most notably, dominant midlevel po...

This paper describes the transformation of the Colorado State University-University of Chicago-Illinois State Water Survey (CSU-CHILL) National Radar Facility from a single-frequency (S band) dual-polarization Doppler weather radar system to a dual-frequency (S and X bands) dual-polarization Doppler system with coaxial beams. A brief history regard...

This study compares and evaluates single-polarization (SP)- and dual-polarization (DP)-based radarrainfall (RR) estimates using NEXRAD data acquired during Iowa Flood Studies (IFloodS), a NASA GPM ground validation field campaign carried out in May-June 2013. The objective of this study is to understand the potential benefit of the DP quantitative...

As part of the Deep Convective Cloud and Chemistry (DC3) experiment, the NSF/NCAR GV and NASA DC-8 research aircraft probed the chemical composition of the inflow and outflow of two convective storms (north storm, NS, south storm, SS) originating in the Colorado region on June 22, 2012, a time when the High Park wild fire was active in the area. A...

The use of both total charge moment change (CMC) and impulse charge moment change (iCMC) magnitudes to assess the potential of a cloud-to-ground (CG) lightning stroke to induce a mesospheric sprite has been well described in the literature, particularly on a case study basis. In this climatological study, large iCMC discharges for thresholds of >10...

This study uses DYNAMO shipborne (R/V Revelle) radar and TRMM Precipitation Radar (PR) datasets to investigate MJO-associated convective systems in specific organizational modes (MCS vs. sub-MCS, linear vs. non-linear). The Revelle radar sampled many “climatological” aspects of MJO convection as indicated by comparison with the long-term TRMM PR st...

The purpose of this study is to demonstrate the use of polarimetric observations in a radar-based winter hydrometeor classification algorithm. This is accomplished by deriving bulk electromagnetic scattering properties of stratiform, cold-season rain, freezing rain, sleet, dry aggregated snowflakes, dendritic snow crystals, and platelike snow cryst...

High-resolution X-band polarimetric radar data were collected in 19 snowstorms over northern Colorado in early 2013 as part of the Front Range Orographic Storms (FROST) project. In each case, small, vertically erect convective turrets were observed near the echo top. These "generating cells" are similar to those reported in the literature and are c...

The issuance of timely warnings for the occurrence of severe-class hail (hailstone diameters of 2.5 cm or larger) remains an ongoing challenge for operational forecasters. This study examines the application of two remotely sensed data sources between 0100 and 0400 UTC 14 July 2011 when pulse-type severe thunderstorms occurred in the jurisdiction o...

Pyrocumulus clouds above three Colorado wildfires (Hewlett Gulch, High Park, and Waldo Canyon; all during the summer of 2012) electrified and produced localized intracloud discharges whenever the smoke plumes grew above 10 km MSL (approximately -45 degrees C). Vertical development occurred during periods of rapid wildfire growth, as indicated by th...

This study examines the occurrence and morphology of frozen-drop aggregates in thunderstorm anvils from the United States Midwest and describes the environmental conditions where they are found. In situ airborne data collected in anvils using several particle imaging and sizing probes and bulk total water instrumentation during the 2012 Deep Convec...

Upward lightning from tall objects can be either self-initiated (SIUL), that is, leaders originating due to locally strong electric fields but without any preceding lightning, or triggered by prior lightning discharges in the general vicinity, termed lightning-triggered upward lightning (LTUL). The LTULs can be triggered by (1) nearby +CG return st...

Researchers demonstrate how observations from 1 km beneath to 25 km above the sea surface reveal the complex interactions in Indian Ocean westerly wind bursts associated with the Madden-Julian oscillation (MJO). This phenomenon exerts a strong influence on Earth's weather and climate systems, acting globally on intra-seasonal time scales. The barri...

This study examines the occurrence and morphology of frozen drop aggregates in thunderstorm anvils from the US Midwest and describes the environmental conditions where they are found. In situ airborne data collected in anvils using several particle imaging and sizing probes and bulk total water instrumentation during the 2012 Deep Convective Clouds...

The Front Range Observational Network Testbed is a joint effort by NCAR and CSU to provide the research and educational user communities with streamlined access to the EOL S-Pol and CSU-CHILL NSF research radars while they are at their home base locations in Colorado. As part of this effort, a new operating site for S-Pol with improved views of bot...

A new 10-category, polarimetric-based hydrometeor identification algorithm (HID) for C band is developed from theoretical scattering simulations including wet snow, hail, and big drops/melting hail. The HID is applied to data from seven wet seasons in Darwin, Australia, using the polarimetric C-band (C-POL) radar, to investigate microphysical diffe...

This study examined the meteorological characteristics of precipitation systems that produced 38 "sprite-class" negative cloud-to-ground (CG) strokes (i.e., peak currents in excess of 100 kA and charge moment changes in excess of 800 C km) as well as those that produced three confirmed negative sprites on 23 different days during 2009-2011. Within...

An analysis of thunderstorm environment, structure, and evolution associated with six gigantic jets (five negative polarity, one positive) was conducted. Three of these gigantic jets were observed within detection range of very high frequency lightning mapping networks. All six were within range of operational radars and two-dimensional lightning n...

Two mesoscale convective systems (MCSs) observed during the African Monsoon Multidisciplinary Analyses (AMMA) experiment are simulated using the three-dimensional (3D) Goddard Cumulus Ensemble model. This study was undertaken to determine the performance of the cloud-resolving model in representing distinct convective and microphysical differences...

The multi-year, multi-institution effort entitled Physical Origins of Coupling to the Upper Atmosphere from Lightning (PhOCAL), has among its goals, to qualitatively understand the meteorology and lightning flash characteristics that produce the unusual and/or very energetic lightning responsible for phenomena such as sprites, halos, elves, blue je...

A 13-year (1998–2010) climatology of mesoscale convective characteristics associ-ated with the West African monsoon are investigated using precipitation radar and passive microwave data from the NASA Tropical Rainfall Measuring Mission satel-lite. Seven regions defined as continental northeast and northwest, southeast and southwest, coastal, and ma...

The Midlatitude Continental Convective Clouds Experiment (MC3E) took place from 22 April through 6 June 2011 centered at the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Southern Great Plains Central Facility in north-central Oklahoma. This campaign was a joint effort between the ARM and the National Aeronautics and Space Adm...

The Mid-Latitude Continental Convective Clouds Experiment (MC3E) was a joint DOE ARM, NASA GPM field campaign during April - June 2011 centered at the ARM Southern Great Plains site. The overarching scientific goals of this campaign were to advance the understanding of the different components of convective parameterization and to improve the fidel...

Despite relatively good agreement between reflectivity profiles, comparisons of rainfall statistics derived from TRMM Precipitation Radar (PR) deviate from ground-based radar (GR) observations in various field locations across the globe. TRMM PR rain rate probability distribution functions underestimate the occurrence of high rain rates (> 80 mm hr...

Two negative polarity gigantic jets were recently observed near high-frequency lightning networks. One was over the Oklahoma Lightning Mapping Array (OKLMA) and the other over the Florida Four-Dimensional Lightning Surveillance System (4DLSS). Previous studies have shown lightning characteristics leading up to the GJ have to be similar in these sto...

Recently, Lang et al. (2010) analyzed the parent lightning of transient luminous events (TLEs) in the context of the structure and evolution of two mesoscale convective systems (MCSs). These two MCSs were very different - one a giant symmetric leading-line/trailing stratiform storm, and one a small asymmetric MCS that contained a mesoscale convecti...

We have examined two negative gigantic jets that occurred sufficiently near a very high-frequency (VHF) lightning mapping network that the associated lightning development is well characterized. Remote sensing of broadband (<1 Hz to 400 kHz) magnetic fields provides extra insights into the charge transfer and detailed sequence of fast discharge eve...

Charge moment change (DeltaMQ) data were examined for 41 positive cloud-to-ground (+CG) lightning discharges that were parents of transient luminous events (TLEs; mainly sprites) over two different storms: 9 May (20 parents) and 20 June 2007 (21). Data were broken down by contributions from the impulse DeltaMQ (iDeltaMQ), within the first 2 ms of t...

A framework for the statistical analysis of large radar and lightning datasets is described and implemented in order to analyze two research questions in atmospheric electricity: storms dominated by positive cloud-to-ground (+CG) lightning and estimating the probability of lightning in convection. The framework-a collection of computer programs run...

We report the observations of two gigantic jets, one during daytime over sea and one at nighttime over land, in the context of detailed associated observations of lightning flash and discharge evolution provided by a variety of radio measurements.

Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger (continental), Kawsara, Senegal (coastal), and Praia, Republic of Cape Verde (maritime)) are analyzed to determine convective system characteristics in each domain during a 29-day period in 2006. Ancillary datasets...

The Colorado State University-University of Chicago-Illinois State Water Survey (CSU-CHILL) national weather radar facility has been operated by the Colorado State University under a cooperative agreement with the U.S. National Science Foundation from 1990 to the present. The radar is configured to measure the elements of the 3 3 3 polarimetric cov...

1] We report observations of two negative polarity gigantic jets sufficiently near very high‐frequency (VHF) lightning mapping networks that the associated lightning character-istics and charge transfer could be investigated. In both cases the gigantic jet‐producing flash began as ordinary intracloud lightning with upper level channels attempting t...

This study is based on analyses of dual-polarization radar observations made by the 11-cm-wavelength Colorado State University-University of Chicago-Illinois State Water Survey (CSU-CHILL) system during four significant winter storms in northeastern Colorado. It was found that values of specific differential phase K DP often reached local maxima of...

The efficacy of dual-polarization radar for quantitative precipitation estimation (QPE) has been demonstrated in a number of previous studies. Specifically, rainfall retrievals using combinations of reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp) have advantages over traditional Z–R methods because more inf...

A major objective of the North American Monsoon Experiment (NAME) was to quantify microphysical processes within convection occurring near the steep topography of northwestern Mexico. A previous study compared examples of isolated convection using polarimetric radar data and noted a dependence on mixed-phase processes via drop freezing and subseque...

Continuing research on transient luminous events (TLEs) above two mesoscale convective systems (MCSs) in range of the Oklahoma Lightning Mapping Array (LMA) is discussed. The 20 June 2007 MCS was a massive leading-line/trailing-stratiform storm that produced 282 observed TLEs over a 4-h period, while the 9 May 2007 storm was an asymmetric MCS that...

The spatial and temporal variability of convection during the North American Monsoon Experiment (NAME) was examined via analysis of three-dimensional polarimetric radar data. Terrain bands were defined as the Gulf of California (over water) and elevations of 0-500 m above mean sea level (MSL; coastal plain), 500-1500 mMSL, and.1500 mMSL. Convective...

Of utmost importance for global precipitation estimates from satellites such as TRMM and the upcoming Global Precipitation Measurement (GPM) is to understand processes that lead to variability in precipitation on sub-seasonal, seasonal, and climatological scales. Many studies have linked differences in rainfall characteristics such as mean diameter...

One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve coldseason precipitation measurements in mid- and high latitudes through the use of high-frequency passive microwave radiometry. For this purpose, the Weather Research and Forecasting model (WRF) with the Goddard microphysics scheme is coupled with a Sat...

1] Two warm‐season mesoscale convective systems (MCSs) were analyzed with respect to their production of transient luminous events (TLEs), mainly sprites. The 20 June 2007 symmetric MCS produced 282 observed TLEs over a 4 h period, during which the storm's intense convection weakened and its stratiform region strengthened. TLE production correspond...

Data from the Collaborative Adaptive Sensing of the Atmosphere (CASA) Integrated Project I (IP1) network of polarimetric X-band radars are used to observe a convective storm. A fuzzy logic hydrometeor identification algorithm is employed to study microphysical processes. Dual-Doppler techniques are used to analyze the 3D wind field. The scanning st...

This study describes the vertical structure of mesoscale convective systems (MCSs) that characterized the 2004 North American monsoon utilizing observations from a 2875-MHz (S band) profiler and a dual-polarimetric scanning Doppler radar. Both instrument platforms operated nearly continuously during the North American Monsoon Experiment (NAME). A t...

Studies of tropical precipitation characteristics from the TRMM-LBA and NAME field campaigns using ground-based polarimetric S-band data have revealed significant differences in microphysical processes occurring in the various meteorological regimes sampled in those projects. In TRMM-LMA (January-February 1999 in Brazil; a TRMM ground validation ex...

Quantitative precipitation forecasting (QPF) is the most important and significant challenge of weather forecasting. Advances in computing and observational technology combined with theoretical advances regarding the chaotic nature of the atmosphere offer the possibility of significant improvement in QPF. To achieve these improvements, this report...

The evolution of an African Easterly Wave (AEW) is described using ground based radar data from 3 distinct locations in West Africa: Niamey, Niger (continental), Dakar, Senegal (coastal), and Praia, Republic of Cape Verde (oceanic). The data were collected during the combined African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) c...

Althoughmuchworkhas beendoneat S bandtoautomatically identifyhydrometeorsbyusing polarimetric radar, several challengesare presented whenadapting such algorithms to X band. At X band, attenuation and non-Rayleigh scattering can pose significant problems. This study seeks to develop a hydrometeor identifi- cation (HID) algorithm for X band based on...

The efficacy of dual polarimetric radar for quantitative precipitation estimation (QPE) is firmly established. Specifically, rainfall retrievals using combinations of reflectivity (ZH), differential reflectivity (ZDR), and specific differential phase (KDP) have advantages over traditional Z-R methods because more information about the drop size dis...

The NASA TRMM satellite has provided unprecedented data for over 11 years. TRMM precipitation products have advanced our understanding of tropical precipitation considerably. Field programs in the tropics, specifically TRMM-LBA (January-February 1999 in Brazil; a TRMM ground validation experiment) and NAME (North American Monsoon Experiment, summer...