scholarly journals Drop-Size Distribution Variations Associated with Different Storm Types in Southeast Texas

Atmosphere ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 8 ◽  
Author(s):  
Larry J. Hopper ◽  
Courtney Schumacher ◽  
Karen Humes ◽  
Aaron Funk
Keyword(s):  
Tropical Cyclones ◽  
Drop Size ◽  
Deep Convection ◽  
Stratiform Rain ◽  
Cold Fronts ◽  
Southeast Texas ◽  
Dynamic Forcing ◽  
Upper Level ◽  
Rain Events ◽  
Rainfall Estimates

Drop-size distributions (DSDs) provide important microphysical information about rainfall and are used in rainfall estimates from radar. This study utilizes a four-year DSD dataset of 163 rain events obtained using a Joss–Waldvogel impact disdrometer located in southeast Texas. A seasonal comparison of the DSD data shows that small (~1 mm diameter) drops occur more frequently in winter and fall, whereas summer and spring months see an increase in the relative frequency of medium and large (~>2 mm diameter) drops, with notable interannual variability in all seasons. Each rain event is classified by dynamic forcing and radar precipitation structure to more directly link environmental and storm organization properties to storm microphysics. Cold fronts and upper-level disturbances account for 80% of the rain events, whereas warm fronts, weakly forced situations, and tropical cyclones comprise the other 20%. Warm frontal storms and upper-level disturbances have smaller drops compared to the climatological DSD for southeast Texas, whereas the more dynamically vigorous cold fronts and weakly forced environments have larger drops. Tropical cyclones generally produce smaller drops than the climatology, but their DSD anomalies are sensitive to what part of the storm is sampled. Regardless of dynamic forcing, storms with precipitation structures that are mostly deep convective or stratiform rain formed from deep convection have larger drops, whereas stratiform rain formed from non-deep convection has smaller drops. Reflectivity-rain rate (Z-R) relationships that account for dynamic forcing and precipitation structures improve rainfall estimates compared to climatological Z-R relationships despite a wide spread in Z-R relationships by storm.

scholarly journals Correction of Radar Reflectivity and Differential Reflectivity for Rain Attenuation at X Band. Part II: Evaluation and Application

2005 ◽  
Vol 22 (11) ◽  
pp. 1633-1655 ◽  
Author(s):  
S-G. Park ◽  
M. Maki ◽  
K. Iwanami ◽  
V. N. Bringi ◽  
V. Chandrasekar
Keyword(s):  
Drop Size ◽  
Earth Science ◽  
Radar Data ◽  
Rain Gauge ◽  
Radar Rainfall ◽  
X Band ◽  
Rain Events ◽  
Differential Reflectivity ◽  
Rainfall Estimates ◽  
Good Agreement

Abstract In this paper, the attenuation-correction methodology presented in Part I is applied to radar measurements observed by the multiparameter radar at the X-band wavelength (MP-X) of the National Research Institute for Earth Science and Disaster Prevention (NIED), and is evaluated by comparison with scattering simulations using ground-based disdrometer data. Further, effects of attenuation on the estimation of rainfall amounts and drop size distribution parameters are also investigated. The joint variability of the corrected reflectivity and differential reflectivity show good agreement with scattering simulations. In addition, specific attenuation and differential attenuation, which are derived in the correction procedure, show good agreement with scattering simulations. In addition, a composite rainfall-rate algorithm is proposed and evaluated by comparison with eight gauges. The radar-rainfall estimates from the uncorrected (or observed) ZH produce severe underestimation, even at short ranges from the radar and for stratiform rain events. On the contrary, the reflectivity-based rainfall estimates from the attenuation-corrected ZH does not show such severe underestimation and does show better agreement with rain gauge measurements. More accurate rainfall amounts can be obtained from a simple composite algorithm based on specific differential phase KDP, with the R(ZH_cor) estimates being used for low rainfall rates (KDP ≤ 0.3° km−1 or ZH_cor ≤ 35 dBZ). This improvement in accuracy of rainfall estimation based on KDP is a result of the insensitivity of the rainfall algorithm to natural variations of drop size distributions (DSDs). The ZH, ZDR, and KDP data are also used to infer the parameters (median volume diameter D0 and normalized intercept parameter Nw) of a normalized gamma DSD. The retrieval of D0 and Nw from the corrected radar data show good agreement with those from disdrometer data in terms of the respective relative frequency histograms. The results of this study demonstrate that high-quality hydrometeorological information on rain events such as rainfall amounts and DSDs can be derived from X-band polarimetric radars.

scholarly journals Secondary Eyewall Formation in Tropical Cyclones by Outflow–Jet Interaction

2017 ◽  
Vol 74 (6) ◽  
pp. 1941-1958 ◽  
Author(s):  
Yi Dai ◽  
Sharanya J. Majumdar ◽  
David S. Nolan
Keyword(s):  
Wind Speed ◽  
Numerical Simulations ◽  
Tropical Cyclones ◽  
Deep Convection ◽  
Stratiform Cloud ◽  
Jet Interaction ◽  
Secondary Eyewall Formation ◽  
Stratiform Region ◽  
Upper Level ◽  
Convective Cells

Abstract This study uses idealized numerical simulations to show that the interaction between tropical cyclones and a midlatitude jet can result in secondary eyewall formation. It is argued that the eddy activity by the outflow–jet interaction can enhance the upper-level outflow, thereby creating an asymmetric stratiform region outside of the primary eyewall. Numerous long-lasting deep convective cells are able to form in the stratiform cloud, creating forcing necessary for the secondary eyewall. The low-level inflow and the TC’s primary circulation advect the deep convective cells inward and cyclonically. The secondary eyewall forms after the deep convection has surrounded the TC. In contrast, numerical simulations without the jet do not show secondary eyewall formation. For moderately strong jets of wind speed 15–30 m s−1, there is little sensitivity to the jet strength. There is sensitivity to the distance between the jet and the TC, with secondary eyewall formation evident when their separation is 15° latitude but not when the separation exceeds 20°.

Effects of Radar Beam Shielding on Rainfall Estimation for the Polarimetric C-Band Radar

2007 ◽  
Vol 24 (11) ◽  
pp. 1839-1859 ◽  
Author(s):  
Katja Friedrich ◽  
Urs Germann ◽  
Jonathan J. Gourley ◽  
Pierre Tabary
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Radar Data ◽  
Drop Size Distribution ◽  
Rainfall Estimation ◽  
Axis Ratio ◽  
Radar Beam ◽  
Average Rainfall ◽  
Rain Events ◽  
Rainfall Estimates

Abstract Radar reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp) measured from the operational, polarimetric weather radar located in Trappes, France, were used to examine the effects of radar beam shielding on rainfall estimation. The objective of this study is to investigate the degree of immunity of Kdp-based rainfall estimates to beam shielding for C-band radar data during four typical rain events encountered in Europe. The rain events include two cold frontal rainbands with average rainfall rates of 7 and 17 mm h−1, respectively, and two summertime convective rain events with average rainfall rates of 11 and 22 mm h−1. The large effects of beam shielding on rainfall accumulation were observed for algorithms using Zh and Zdr with differences of up to ∼2 dB (40%) compared to a Kdp-based algorithm over a power loss range of 0–8 dB. This analysis reveals that Zdr and Kdp are not affected by partial beam shielding. Standard reflectivity corrections based on the degree of beam shielding would have overestimated rainfall rates by up to 1.5 dB for less than 40% beam shielding and up to 3 dB for beam shielding less than 75%. The investigation also examined the sensitivity of beam shielding effects on rainfall rate estimation to (i) axis–ratio parameterization and drop size distribution, (ii) methods used to smooth profiles of differential propagation phase (ϕdp) and estimate Kdp, and (iii) event-to-event variability. Although rainfall estimates were sensitive to drop size distribution and axis–ratio parameterization, differences between Zh- and Kdp-based rainfall rates increased independently from those parameters with amount of shielding. Different approaches to smoothing ϕdp profiles and estimating Kdp were examined and showed little impact on results.

scholarly journals Baroclinicity Influences on Storm Divergence and Stratiform Rain: Subtropical Upper-Level Disturbances

2009 ◽  
Vol 137 (4) ◽  
pp. 1338-1357 ◽  
Author(s):  
Larry J. Hopper ◽  
Courtney Schumacher
Keyword(s):  
Diabatic Heating ◽  
Doppler Radar ◽  
Mesoscale Model ◽  
Deep Convection ◽  
Separation Algorithm ◽  
Rain Area ◽  
Stratiform Rain ◽  
Wide Range ◽  
Upper Level ◽  
The Tropics

Abstract Divergence structures associated with the spectrum of precipitating systems in the subtropics and midlatitudes are not well documented. A mesoscale model is used to quantify the relative importance different baroclinic environments have on divergence profiles for storms primarily caused by upper-level disturbances in southeastern Texas, a subtropical region. The divergence profiles simulated for a subset of the modeled storms are consistent with those calculated from an S-band Doppler radar. Realistic convective and stratiform divergence signals are also generated when applying a two-dimensional convective–stratiform separation algorithm to reflectivities derived from the mesoscale model, although the model appears to underestimate stratiform rain area. Divergence profiles from the modeled precipitating systems vary in magnitude and structure across the wide range of baroclinicities common in southeastern Texas. Barotropic storms more characteristic of the tropics generate the most elevated divergence (and thus diabatic heating) structures with the largest magnitudes. In addition, stratiform rain regions in barotropic storms contain thicker, more elevated midlevel convergence signatures than more baroclinic storms. As the degree of baroclinicity increases, stratiform area fractions generally increase while the levels of nondivergence (LNDs) decrease. However, some weakly baroclinic storms contain stratiform area fractions and/or divergence profiles with magnitudes and LNDs that are similar to barotropic storms, despite having lower tropopause heights and less deep convection. Additional convection forms after the passage of barotropic and weakly baroclinic storms that contain elevated divergence signatures, circumstantially suggesting that heating at upper levels may cause diabatic feedbacks that help to drive regions of persistent convection in the subtropics.

scholarly journals Synoptic-Scale Environments of Predecessor Rain Events Occurring East of the Rocky Mountains in Association with Atlantic Basin Tropical Cyclones*

2013 ◽  
Vol 141 (3) ◽  
pp. 1022-1047 ◽  
Author(s):  
Benjamin J. Moore ◽  
Lance F. Bosart ◽  
Daniel Keyser ◽  
Michael L. Jurewicz
Keyword(s):  
Tropical Cyclones ◽  
Rocky Mountains ◽  
Composite Analysis ◽  
Synoptic Scale ◽  
Atlantic Basin ◽  
Upper Level ◽  
Rain Events ◽  
Upper Level Jet ◽  
Jet Streak ◽  
Baroclinic Zone

Abstract The synoptic-scale environments of predecessor rain events (PREs) occurring to the east of the Rocky Mountains in association with Atlantic basin tropical cyclones (TCs) are examined. PREs that occurred during 1988–2010 are subjectively classified based upon the synoptic-scale upper-level flow configuration within which the PRE develops, with a focus on the following: 1) the position of the jet streak relative to the TC, 2) the position of the jet streak relative to trough and ridge axes, and 3) the positions of trough and ridge axes relative to the PRE and to the TC. Three categories were identified from this classification procedure: “jet in ridge,” “southwesterly jet,” and “downstream confluence.” PRE-relative composite analysis for each category reveals that, consistent with previous studies, PREs typically occur near a low-level baroclinic zone, beneath the equatorward entrance region of an upper-level jet streak, and in the presence of a stream of water vapor from a TC. Despite these common characteristics, key differences exist among the three PRE categories related to the phasing of a TC with the synoptic-scale flow and to the interactions between a TC and its environment. Brief case studies of PREs associated with TC Rita (2005), TC Wilma (2005), and TC Ernesto (2006) are presented as specific examples of the three PRE categories.

scholarly journals PENGAMATAN KEJADIAN HUJAN DENGAN DISDROMETER DAN MICRO RAIN RADAR DI SERPONG

2017 ◽  
Vol 18 (1) ◽  
pp. 1
Author(s):  
Findy Renggono
Keyword(s):  
Size Distribution ◽  
Rainy Season ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Rain Event ◽  
Stratiform Rain ◽  
Convective Rain ◽  
Rain Events ◽  
Rain Radar

IntisariPengamatan hujan dengan menggunakan beberapa peralatan yang mempunyai metode berbeda telah dilakukan di wilayah Serpong. Peralatan yang digunakan adalah Disdrometer dan Micro Rain Radar (MRR). Kedua peralatan tersebut dipasang pada satu lokasi yang sama agar dapat mengukur kejadian hujan yang sama. Pengamatan dilakukan pada akhir tahun 2016 selama 5 bulan, disesuaikan dengan kondisi dimana musim hujan sudah mulai masuk untuk wilayah ini. Perbandingan pengukuran yang telah dilakukan menunjukkan kesesuaian hasil antara kedua peralatan tersebut.  Pengamatan distribusi ukuran butir air pada empat kejadian hujan antara bulan Agustus-Desember 2016 menunjukkan bahwa hujan konvektif mempunyai distribusi ukuran yang lebih besar dibandingkan hujan stratiform.  AbstractRain observation by using several instruments having different method has been done in Serpong area. The instrument used is Disdrometer and Micro Rain Radar (MRR). Both instruments are installed in the same location in order to measure the same rain events. Observations were made at the end of 2016 for 5 months, adjusted to the conditions in which the rainy season has begun to enter for the region. Comparison of measurements that have been done indicate the suitability of the results between the two instrument. Drop size distribution of four rain event during August - December 2016 shows that the drop size distribution on convective rain broaden than on stratiform rain. 

Intensification of Tilted Tropical Cyclones Over Relatively Cool and Warm Oceans in Idealized Numerical Simulations

2021 ◽  
Author(s):  
David A. Schecter
Keyword(s):  
Relative Humidity ◽  
Tropical Cyclones ◽  
Inner Core ◽  
Structural Parameters ◽  
Deep Convection ◽  
Surface Wind ◽  
Vertical Wind Shear ◽  
Surface Wind Speed ◽  
Cloud Resolving Model ◽  
Complete Alignment

Abstract A cloud resolving model is used to examine the intensification of tilted tropical cyclones from depression to hurricane strength over relatively cool and warm oceans under idealized conditions where environmental vertical wind shear has become minimal. Variation of the SST does not substantially change the time-averaged relationship between tilt and the radial length scale of the inner core, or between tilt and the azimuthal distribution of precipitation during the hurricane formation period (HFP). By contrast, for systems having similar structural parameters, the HFP lengthens superlinearly in association with a decline of the precipitation rate as the SST decreases from 30 to 26 °C. In many simulations, hurricane formation progresses from a phase of slow or neutral intensification to fast spinup. The transition to fast spinup occurs after the magnitudes of tilt and convective asymmetry drop below certain SST-dependent levels following an alignment process explained in an earlier paper. For reasons examined herein, the alignment coincides with enhancements of lower–middle tropospheric relative humidity and lower tropospheric CAPE inward of the radius of maximum surface wind speed rm. Such moist-thermodynamic modifications appear to facilitate initiation of the faster mode of intensification, which involves contraction of rm and the characteristic radius of deep convection. The mean transitional values of the tilt magnitude and lower–middle tropospheric relative humidity for SSTs of 28-30 °C are respectively higher and lower than their counterparts at 26 °C. Greater magnitudes of the surface enthalpy flux and core deep-layer CAPE found at the higher SSTs plausibly compensate for less complete alignment and core humidification at the transition time.

scholarly journals The Unexpected Rapid Intensification of Tropical Cyclones in Moderate Vertical Wind Shear. Part I: Overview and Observations

2018 ◽  
Vol 146 (11) ◽  
pp. 3773-3800 ◽  
Author(s):  
David R. Ryglicki ◽  
Joshua H. Cossuth ◽  
Daniel Hodyss ◽  
James D. Doyle
Keyword(s):  
Tropical Cyclones ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Convective Cloud ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Brightness Temperatures ◽  
Idealized Modeling ◽  
Hurricane Prediction ◽  
Upper Level

Abstract A satellite-based investigation is performed of a class of tropical cyclones (TCs) that unexpectedly undergo rapid intensification (RI) in moderate vertical wind shear between 5 and 10 m s−1 calculated as 200–850-hPa shear. This study makes use of both infrared (IR; 11 μm) and water vapor (WV; 6.5 μm) geostationary satellite data, the Statistical Hurricane Prediction Intensity System (SHIPS), and model reanalyses to highlight commonalities of the six TCs. The commonalities serve as predictive guides for forecasters and common features that can be used to constrain and verify idealized modeling studies. Each of the TCs exhibits a convective cloud structure that is identified as a tilt-modulated convective asymmetry (TCA). These TCAs share similar shapes, upshear-relative positions, and IR cloud-top temperatures (below −70°C). They pulse over the core of the TC with a periodicity of between 4 and 8 h. Using WV satellite imagery, two additional features identified are asymmetric warming/drying upshear of the TC relative to downshear, as well as radially thin arc-shaped clouds on the upshear side. The WV brightness temperatures of these arcs are between −40° and −60°C. All of the TCs are sheared by upper-level anticyclones, which limits the strongest environmental winds to near the tropopause.

scholarly journals Tropical Cyclone Diurnal Cycle Signals in a Hurricane Nature Run

2019 ◽  
Vol 147 (1) ◽  
pp. 363-388 ◽  
Author(s):  
Jason P. Dunion ◽  
Christopher D. Thorncroft ◽  
David S. Nolan
Keyword(s):  
Tropical Cyclones ◽  
Diurnal Cycle ◽  
Deep Layer ◽  
Squall Line ◽  
Distinguishing Characteristic ◽  
Optimal Conditions ◽  
Work Support ◽  
Upper Level ◽  
Radiation Thermodynamics ◽  
Low Shear

The diurnal cycle of tropical convection and tropical cyclones (TCs) has been previously described in observational-, satellite-, and modeling-based studies. The main objective of this work is to expand on these earlier studies by identifying signals of the TC diurnal cycle (TCDC) in a hurricane nature run, characterize their evolution in time and space, and better understand the processes that cause them. Based on previous studies that identified optimal conditions for the TCDC, a select period of the hurricane nature run is examined when the simulated storm was intense, in a low shear environment, and sufficiently far from land. When analyses are constrained by these conditions, marked radially propagating diurnal signals in radiation, thermodynamics, winds, and precipitation that affect a deep layer of the troposphere become evident in the model. These propagating diurnal signals, or TC diurnal pulses, are a distinguishing characteristic of the TCDC and manifest as a surge in upper-level outflow with underlying radially propagating tropical squall-line-like features. The results of this work support previous studies that examined the TCDC using satellite data and have implications for numerical modeling of TCs and furthering our understanding of how the TCDC forms, evolves, and possibly impacts TC structure and intensity.

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