Seasonal Controls on Isolated Convective Storm Drafts, Precipitation Intensity, and Life Cycle As Observed During GoAmazon2014/5

Isolated deep convective cloud life cycle and seasonal changes in storm properties are observed for daytime events during the DOE-ARM GoAmazon2014/5 campaign to understand controls on storm behavior. Storm life cycles are documented using surveillance radar from initiation through maturity and dissipation. Vertical air velocity estimates are obtained from radar wind profiler overpasses, with the storm environment informed by radiosondes. Dry season storm conditions favored reduced morning shallow cloud coverage and larger low level convective available potential energy (CAPE) than wet season counterparts. The typical dry season storm reached its peak intensity and size earlier in its life cycle compared to wet season cells. These cells exhibited updrafts in core precipitation regions (Z &gt; 35 dBZ) to above the melting level, and persistent downdrafts aloft within precipitation adjacent to their cores. Moreover, dry season cells recorded more intense updrafts to earlier life cycle stages, and a higher incidence of strong updrafts (i.e., &gt; 5 m/s) at low levels. In contrast, wet season storms were longer-lived and featured a higher incidence of moderate (i.e., 2&ndash;5 m/s) updrafts aloft. These storms also favored a shift in their most intense properties to later life cycle stages. Strong downdrafts were far less frequent within wet season cells aloft, indicating a potential systematic difference in downdraft behaviors between the seasons. Results from a stochastic parcel model suggest that dry season cells may expect stronger updrafts at low levels because of larger low level CAPE in the dry season. Wet season cells anticipate strong updrafts aloft because of larger free-tropospheric relative humidity and reduced entrainment-driven dilution. The enhanced dry season downdrafts are attributed to increased evaporation, dry air entrainment-mixing, and negative buoyancy in regions adjacent to sampled dry season cores.</p

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

An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.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

Use of Polarimetric Radar Measurements to Constrain Simulated Convective Cell Evolution: A Pilot Study with Lagrangian Tracking

To probe the potential value of a radar-driven field campaign to constrain simulation of isolated convection subject to a strong aerosol perturbation, convective cells observed by the operational KHGX weather radar in the vicinity of Houston, Texas, are examined individually and statistically. Cells observed in a single case study of onshore flow conditions during July 2013 are first examined and compared with cells in a regional model simulation. Observed and simulated cells are objectively identified and tracked from observed or calculated positive specific differential phase (K(sub DP)) above the melting level, which is related to the presence of supercooled liquid water. Several observed and simulated cells are subjectively selected for further examination. Below the melting level, we compare sequential cross sections of retrieved and simulated raindrop size distribution parameters. Above the melting level, we examine time series of KDP and radar differential reflectivity (Z(sub DR)) statistics from observations and calculated from simulated supercooled rain properties, alongside simulated vertical wind and supercooled rain mixing ratio statistics. Results indicate that the operational weather radar measurements offer multiple constraints on the properties of simulated convective cells, with substantial value added from derived K(sub DP) and retrieved rain properties. The value of collocated three-dimensional lightning mapping array measurements, which are relatively rare in the continental US, supports the choice of Houston as a suitable location for future field studies to improve the simulation and understanding of convective updraft physics. However, rapid evolution of cells between routine volume scans motivates consideration of adaptive scan strategies or radar imaging technologies to amend operational weather radar capabilities. A 3-year climatology of isolated cell tracks, prepared using a more efficient algorithm, yields additional relevant information. Isolated cells are found within the KHGX domain on roughly 40 % of days year-round, with greatest concentration in the northwest quadrant, but roughly 5-fold more cells occur during June through September. During this enhanced occurrence period, the cells initiate following a strong diurnal cycle that peaks in the early afternoon, typically follow a south-to-north flow, and dissipate within 1 h, consistent with the case study examples. Statistics indicate that 150 isolated cells initiate and dissipate within 70 km of the KHGX radar during the enhanced occurrence period annually, and roughly 10 times as many within 200 km, suitable for multi-instrument Lagrangian observation strategies. In addition to ancillary meteorological and aerosol measurements, robust vertical wind speed retrievals would add substantial value to a radar-driven field campaign

Cloud-resolving model intercomparison of an MC3E squall line case: Part I-Convective updrafts

An intercomparison study of a midlatitude mesoscale squall line is performed using the Weather Research and Forecasting (WRF) model at 1 km horizontal grid spacing with eight different cloud microphysics schemes to investigate processes that contribute to the large variability in simulated cloud and precipitation properties. All simulations tend to produce a wider area of high radar reflectivity (Z_e > 45 dBZ) than observed but a much narrower stratiform area. The magnitude of the virtual potential temperature drop associated with the gust front passage is similar in simulations and observations, while the pressure rise and peak wind speed are smaller than observed, possibly suggesting that simulated cold pools are shallower than observed. Most of the microphysics schemes overestimate vertical velocity and Ze in convective updrafts as compared with observational retrievals. Simulated precipitation rates and updraft velocities have significant variability across the eight schemes, even in this strongly dynamically driven system. Differences in simulated updraft velocity correlate well with differences in simulated buoyancy and low-level vertical perturbation pressure gradient, which appears related to cold pool intensity that is controlled by the evaporation rate. Simulations with stronger updrafts have a more optimal convective state, with stronger cold pools, ambient low-level vertical wind shear, and rear-inflow jets. Updraft velocity variability between schemes is mainly controlled by differences in simulated ice-related processes, which impact the overall latent heating rate, whereas surface rainfall variability increases in no-ice simulations mainly because of scheme differences in collision-coalescence parameterizations

Two Isoforms of the mRNA Binding Protein IGF2BP2 Are Generated by Alternative Translational Initiation

IGF2BP2 is a member of a family of mRNA binding proteins that, collectively, have been shown to bind to several different mRNAs in mammalian cells, including one of the mRNAs encoding insulin-like growth factor-2. Polymorphisms in the Igf2bp2 gene are associated with risk of developing type 2 diabetes, but detailed functional characterisation of IGF2BP2 protein is lacking. By immunoblotting with C-terminally reactive antibodies we identified a novel IGF2BP2 isoform with a molecular weight of 58 kDa in both human and rodents, that is expressed at somewhat lower levels than the full-length 65 kDa protein. We demonstrated by mutagenesis that this isoform is generated by alternative translation initiation at the internal Met69. It lacks a conserved N-terminal RNA Recognition Motif (RRM) and would be predicted to differ functionally from the canonical full length isoform. We further investigated IGF2BP2 mRNA transcripts by amplification of cDNA using 5′-RACE. We identified multiple transcription start sites of the human, mouse and rat Igf2bp2 genes in a highly conserved region only 50–90 nts upstream of the major translation start site, ruling out the existence of N-terminally extended isoforms. We conclude that structural heterogeneity of IGF2BP2 protein should be taken into account when considering cellular function

Rainfall-Rate Estimation Using Gaussian Mixture Parameter Estimator: Training and Validation

ABSTRACT This study develops a Gaussian mixture rainfall-rate estimator (GMRE) for polarimetric radar-based rainfall-rate estimation, following a general framework based on the Gaussian mixture model and Bayes least squares estimation for weather radar-based parameter estimations. The advantages of GMRE are 1) it is a minimum variance unbiased estimator; 2) it is a general estimator applicable to different rain regimes in different regions; and 3) it is flexible and may incorporate/exclude different polarimetric radar variables as inputs. This paper also discusses training the GMRE and the sensitivity of performance to mixture number. A large radar and surface gauge observation dataset collected in central Oklahoma during the multiyear Joint Polarization Experiment (JPOLE) field campaign is used to evaluate the GMRE approach. Results indicate that the GMRE approach can outperform existing polarimetric rainfall techniques optimized for this JPOLE dataset in terms of bias and root-mean-square error

Cloud‐Resolving Model Intercomparison of an MC3E Squall Line Case: Part II. Stratiform Precipitation Properties

In this second part of a cloud microphysics scheme intercomparison study, we focus on biases and variabilities of stratiform precipitation properties for a midlatitude squall line event simulated with a cloud-resolving model implemented with eight cloud microphysics schemes. Most of the microphysics schemes underestimate total stratiform precipitation, mainly due to underestimation of stratiform precipitation area. All schemes underestimate the frequency of moderate stratiform rain rates (2-6mm/hr), which may result from low-biased ice number and mass concentrations for 0.2-2-mm diameter particles in the stratiform ice region. Most simulations overestimate ice water content (IWC) at altitudes above 7km for temperatures colder than -20 degrees C but produce a decrease of IWC approaching the melting level, which is opposite to the trend shown by in situ observations. This leads to general underestimations of stratiform IWC below 5-km altitude and rainwater content above 1-km altitude for a given rain rate. Stratiform precipitation area positively correlates with the convective condensate detrainment flux but is modulated by hydrometeor type, size, and fall speed. Stratiform precipitation area also changes by up to 17%-25% through alterations of the lateral boundary condition forcing frequency. Stratiform precipitation, rain rate, and area across the simulations vary by a factor of 1.5. This large variability is primarily a result of variability in the stratiform downward ice mass flux, which is highly correlated with convective condensate horizontal detrainment strength. The variability of simulated local microphysical processes in the stratiform region plays a secondary role in explaining variability in simulated stratiform rainfall properties. Plain Language Summary This is a unique model intercomparison study about different microphysics parametrizations commonly used, with the purposes of examining model biases and variability as well as identifying major factors/processes leading to bias and variability. The study simulated a well-observed squall line MCS from MC3E field campaign, and focused on the stratiform precipitation, following on our part 1 study focusing on convective part. We employed a more constrained approach compared with past intercomparison studies to better identify processes contributing to the differences. Another unique part is our comprehensive model evaluation, that is, we identify stratiform columns and evaluate vertical evolution of cloud properties including size distribution. We find that most of the microphysics schemes underestimate total stratiform precipitation, mainly due to underestimation of stratiform precipitation area. Moderate stratiform rain rates are underestimated, mainly due to incorrect vertical evolution of ice particles. Stratiform precipitation properties across the simulations vary by a factor of 1.5, primarily a result of variability in detrained condensate amount. In addition, we find that stratiform precipitation area correlates well with detrainment amount and is modulated by the detrained hydrometeor properties. So convective microphysics plays a key role in determining stratiform properties.U.S. Department of Energy (DOE) Atmospheric System Research (ASR) Program; U.S. Department of Energy (DOE) Climate Model Development and Validation (CMDV) program; DOE [DE-AC06-76RLO1830]; Office of Science of the U.S. DOE [DE-AC02-05CH1123]; National Basic Research Program of China [2013CB430105]; National Natural Science Foundation of China [41575130, 41775132]; U.S. DOE ASR grant [DE-SC0008678, DE-SC0008648, DE-SC0016476]; DOE CMDV project at University of Arizona [DE-SC0017015]; U.S. DOE [DE-AC02-98CH10886]; Israel Science Foundation [2027/17]; U.S. National Science Foundation; [DE-SC008811]6 month embargo; published online: 2 January 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]