The ARM Mobile Facilities

Miller, Mark A.; Nitschke, Kim; Ackerman, Thomas P.; Ferrell, W.R.; Hickmon, N.; Ivey, Mark D.

doi:10.1175/amsmonographs-d-15-0051.1

Cited by 52 publications

(28 citation statements)

References 34 publications

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“…Our motivation is to further characterize MCS kinematic structure by exploring bulk MCS properties from two archetypal continental locations to demonstrate regional (midlatitude, tropical) and select seasonal variability. These characterizations are drawn from a multievent data set collected by the U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM, Mather & Voyles, ) program field site in Oklahoma, USA, and Mobile Facility (Miller et al, ) deployment in the Amazon Basin. Emphasis for the current study is on composite mean vertical air motion profiles and normalized time‐height characteristics for the passage of intense (e.g., rain rate > 10 mm/hr) and mature (e.g., precipitating line) stage MCSs over the RWPs.…”

Section: Introductionmentioning

confidence: 99%

The Characteristics of Tropical and Midlatitude Mesoscale Convective Systems as Revealed by Radar Wind Profilers

et al. 2019

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This study contrasts characteristics of mature squall‐line mesoscale convective systems (MCSs) observed by extended ground‐based radar wind profiler (RWP) deployments from the U.S. Department of Energy Atmospheric Radiation Measurement program. This analysis compares the dynamical structure, precipitation, and cold pool properties associated with MCS events over RWP sites in Oklahoma, USA, (midlatitude) to those observed during a 2‐year RWP deployment to Manaus, Brazil, during GoAmazon2014/5 campaign (tropical). The MCSs indicate similar convective line rainfall rates and total rainfall accumulations. However, midlatitude events suggest a larger fractional stratiform contribution to total precipitation. For both regions, convective line cold pools are associated with sharp decreases (approximately 10 K) in the surface equivalent potential temperature (θe) near the time of line passage. Surface θe properties for both regions suggest a modest relationship between rainfall rate and the probability of observing measurable surface rainfall. The probability of observing convective updrafts in both tropical and midlatitude MCS events is found to be similar as a function of low‐level radar reflectivity. However, midlatitude MCSs are associated with more intense convective updrafts, with upward air motions (mean, maximum) peaking at higher altitude. The most pronounced contrast is the propensity for deeper and more intense downdrafts in midlatitude MCSs. An analysis based on observed downdraft properties is performed using simple mixing assumptions. For these events, the vertical gradient of θe in the lower troposphere is relatively consistent between the Amazon and Oklahoma, suggesting similar mixing rates for downdrafts originating below 3 km (0.1 km−1). However, if downdrafts originate nearer to the level of minimum θe at SGP, mixing may be occurring at rates comparable to 0.3 km−1.

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Section: Introductionmentioning

confidence: 99%

The Characteristics of Tropical and Midlatitude Mesoscale Convective Systems as Revealed by Radar Wind Profilers

et al. 2019

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“…For example, Rémillard et al () report that for a 35‐event data set, Azores marine stratocumulus clouds generated precipitation 70% of the time, while “intense” drizzle rates (based on a near‐surface radar reflectivity threshold of 0 dBZ) are rare and preferentially occur near sunrise/sunset (<5% of the cases). Yang et al () found drizzle in >80% of cloud radar profiles of marine stratocumulus observed over a 20‐month deployment of the ARM mobile facility (Miller et al, ) on Graciosa Island (Wood et al, ), with precipitation reaching the surface in 30% of the profiles. Measurable surface precipitation therefore occurs in a relatively small fraction of the total lower cloud coverage over the ENA site.…”

Section: Introductionmentioning

confidence: 99%

Midlatitude Oceanic Cloud and Precipitation Properties as Sampled by the ARM Eastern North Atlantic Observatory

et al. 2019

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Marine low clouds are critical to the climate system because of their extensive coverage and associated controls on boundary layer dynamics and radiative energy balance. The primary foci for this study are marine low cloud observations over a heavily instrumented site on the Azores archipelago in the Eastern North Atlantic and their associated raindrop size distribution (DSD) properties, relative low cloud contributions to the precipitation, and additional sampling (instrument, environmental) considerations. The contribution from low clouds (e.g., cloud top < 4 km) to the overall precipitation over midlatitude oceans is poorly understood, in part because of the lack of coupled, high‐quality measurements of precipitation and low cloud properties. Cloud regime and precipitation breakdowns performed for a multiyear (2014–2017) record emphasize diurnal precipitation and raindrop size distribution characteristics for both low and deeper clouds, as well as differences between the two disdrometer types used. Results demonstrate that marine low clouds over this Eastern North Atlantic location account for a significant (45%) contribution to the total rainfall and exhibit a diurnal cycle in cloud (thickness, top, and base) and precipitation characteristics similar to satellite records. Additional controls on observed surface rainfall characteristics of low clouds allowed by the extended ground‐based facility data sets are also explored. From those analyses, it is suggested that the synoptic state exerts a significant control on low cloud and surface precipitation properties.

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“…The Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-section Intercomparison) Investigation of Clouds (MAGIC) field campaign was conducted in autumn 2012 and 2013 in the North Pacific (Zhou et al, 2015). During MAGIC, the ARM mobile facility (Mather and Voyles, 2013;Miller et al, 2016) was deployed on the Horizon Line cargo ship Spirit while it made regular transects between Los Angeles, California and Honolulu, Hawaii. In this study we use observations collected from seven of these transects of the MAGIC field campaign to retrieve entrainment rates in closed cellular marine stratocumulus clouds.…”

Section: Abstract Boundary Layer Entrainment Stratocumulus Introducmentioning

confidence: 99%

Estimates of entrainment in closed cellular marine stratocumulus clouds from the MAGIC field campaign

Ghate

Mechem

Cadeddu

et al. 2019

Quart J Royal Meteoro Soc

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Entrainment of warm, dry air from above the boundary layer into the cloud layer has a significant impact on stratocumulus clouds in the marine boundary layer. During the MAGIC field campaign, the Atmospheric Radiation Measurement (ARM) mobile facility was deployed aboard a container ship that made regular transects between Los Angeles, California and Honolulu, Hawaii. Observations made during MAGIC transects were collocated with observations from the Geostationary Operational Environmental Satellite (GOES‐15) and European Centre for Medium‐range Weather Forecasting (ECMWF) reanalysis model. From these data, hourly estimates of entrainment velocities in closed cellular stratocumulus cloud conditions were calculated from the mixed‐layer mass budget equation, modified to accommodate observations sampled from a moving platform. The technique is demonstrated using observations collected during Leg 15A (46 h) and then extended to 178 h of data. The average entrainment velocity was 7.83 ± 5.23 mm/s, and the average large‐scale vertical air motion at cloud top (obtained from reanalysis) was −2.56 ± 3.31 mm/s. The vertical air motion at cloud top was positive (upward) during 36 h (∼20%) with a mean of 2.68 mm/s. Entrainment velocity is highly variable and on average the MAGIC observations show no dependence of entrainment velocity on longitude or any pronounced diurnal cycle. When binned by inversion strength, the mean entrainment velocity and mean large‐scale vertical air motion mirrored each other, with both exhibiting substantial variability. Collectively, our results suggest a mean entrainment‐velocity behaviour associated with the background state, with large changes in entrainment velocity forced by strong variability in internal boundary‐layer properties like turbulence, radiation, and inversion strength. This cautions against using climatological mean estimates of entrainment velocities or neglecting instances with upward large‐scale vertical air motion.

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The ARM Mobile Facilities

Cited by 52 publications

References 34 publications

The Characteristics of Tropical and Midlatitude Mesoscale Convective Systems as Revealed by Radar Wind Profilers

The Characteristics of Tropical and Midlatitude Mesoscale Convective Systems as Revealed by Radar Wind Profilers

Midlatitude Oceanic Cloud and Precipitation Properties as Sampled by the ARM Eastern North Atlantic Observatory

Estimates of entrainment in closed cellular marine stratocumulus clouds from the MAGIC field campaign

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