scholarly journals Assimilation of GOES-R Geostationary Lightning Mapper Flash Extent Density Data in GSI EnKF for the Analysis and Short-Term Forecast of a Mesoscale Convective System

2020 ◽  
Vol 148 (5) ◽  
pp. 2111-2133 ◽  
Author(s):  
Rong Kong ◽  
Ming Xue ◽  
Alexandre O. Fierro ◽  
Youngsun Jung ◽  
Chengsi Liu ◽  
...  
Keyword(s):  
Mesoscale Convective System ◽  
Convective System ◽  
Lightning Flash ◽  
Moist Convection ◽  
State Variables ◽  
Short Term ◽  
Pixel Resolution ◽  
Cross Covariance ◽  
Mesoscale Convective ◽  
Total Lightning

Abstract The recently launched Geostationary Operational Environmental Satellite “R-series” (GOES-R) satellites carry the Geostationary Lightning Mapper (GLM) that measures from space the total lightning rate in convective storms at high spatial and temporal frequencies. This study assimilates, for the first time, real GLM total lightning data in an ensemble Kalman filter (EnKF) framework. The lightning flash extent density (FED) products at 10-km pixel resolution are assimilated. The capabilities to assimilate GLM FED data are first implemented into the GSI-based EnKF data assimilation (DA) system and tested with a mesoscale convective system (MCS). FED observation operators based on graupel mass or graupel volume are used. The operators are first tuned through sensitivity experiments to determine an optimal multiplying factor to the operator, before being used in FED DA experiments FEDM and FEDV that use the graupel-mass or graupel-volume-based operator, respectively. Their results are compared to a control experiment (CTRL) that does not assimilate any FED data. Overall, both DA experiments outperform CTRL in terms of the analyses and short-term forecasts of FED and composite/3D reflectivity. The assimilation of FED is primarily effective in regions of deep moist convection, which helps improve short-term forecasts of convective threats, including heavy precipitation and lightning. Direct adjustments to graupel mass via observation operator as well as adjustments to other model state variables through flow-dependent ensemble cross covariance within EnKF are shown to work together to generate model-consistent analyses and overall improved forecasts.

scholarly journals Evaluation of Different Storm Parameters as the Proxies for Gridded Total Lightning Flash Rates: A Convection-Allowing Model Study

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 95
Author(s):  
Xinyao Qian ◽  
Haoliang Wang
Keyword(s):  
Data Assimilation ◽  
Mesoscale Convective System ◽  
Radar Data ◽  
Skill Score ◽  
Convective System ◽  
Test Case ◽  
Lightning Flash ◽  
Simulation Accuracy ◽  
Mesoscale Convective ◽  
Total Lightning

Lightning simulation is important for a variety of applications, including lightning forecast, atmospheric chemical simulation, and lightning data assimilation. In this study, the potential of five storm parameters (graupel volume, precipitation ice mass, radar echo volume, maximum updraft, and updraft volume) to be used as the proxy for the diagnosis of gridded total lightning flash rates has been investigated in a convection-allowing model. A mesoscale convective system occurred in the Guangdong province of China was selected as the test case. Radar data assimilation was used to improve the simulation accuracy of the convective clouds, hence providing strong instantaneous correlations between observed and simulated storm signatures. The areal coverage and magnitude of the simulated lightning flash rates were evaluated by comparing to those of the total lightning observations. Subjective and the Fractions Skill Score (FSS) evaluations suggest that all the five proxies tested in this study are useful to indicate general tendencies for the occurrence, region, and time of lightning at convection-allowing scale (FSS statistics for the threshold of 1 flash per 9 km2 per hour were around 0.7 for each scheme). The FSS values were decreasing as the lightning flash rate thresholds used for FSS computation increased for all the lightning diagnostic schemes with different proxies. For thresholds from 1 to 3 and 16 to 20 flashes per 9 km2 per hour, the graupel contents related schemes achieved higher FSS values compared to the other three schemes. For thresholds from 5 to 15 flashes per 9 km2 per hour, the updraft volume related scheme yielded the largest FSS. When the thresholds of lightning flash rates were greater than 13 flashes per 9 km2 per hour, the FSS values were below 0.5 for all the lightning diagnostic schemes with different proxies.

scholarly journals Evaluating Smartphone Pressure Observations for Mesoscale Analyses and Forecasts

2017 ◽  
Vol 32 (2) ◽  
pp. 511-531 ◽  
Author(s):  
Luke E. Madaus ◽  
Clifford F. Mass
Keyword(s):  
United States ◽  
Rural Areas ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Active Period ◽  
Eastern United States ◽  
Short Term ◽  
Mesoscale Convective ◽  
Dynamic Structures ◽  
Further Development

Abstract Smartphone pressure observations have the potential to greatly increase surface observation density on convection-resolving scales. Currently available smartphone pressure observations are tested through assimilation in a mesoscale ensemble for a 3-day, convectively active period in the eastern United States. Both raw pressure (altimeter) observations and 1-h pressure (altimeter) tendency observations are considered. The available observation density closely follows population density, but observations are also available in rural areas. The smartphone observations are found to contain significant noise, which can limit their effectiveness. The assimilated smartphone observations contribute to small improvements in 1-h forecasts of surface pressure and 10-m wind, but produce larger errors in 2-m temperature forecasts. Short-term (0–4 h) precipitation forecasts are improved when smartphone pressure and pressure tendency observations are assimilated as compared with an ensemble that assimilates no observations. However, these improvements are limited to broad, mesoscale features with minimal skill provided at convective scales using the current smartphone observation density. A specific mesoscale convective system (MCS) is examined in detail, and smartphone pressure observations captured the expected dynamic structures associated with this feature. Possibilities for further development of smartphone observations are discussed.

Mesoscale Convective Vortices in Multiscale, Idealized Simulations: Dependence on Background State, Interdependency with Moist Baroclinic Cyclones, and Comparison with BAMEX Observations

2010 ◽  
Vol 138 (4) ◽  
pp. 1119-1139 ◽  
Author(s):  
Robert J. Conzemius ◽  
Michael T. Montgomery
Keyword(s):  
Tangential Velocity ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Pressure Amplitude ◽  
Moist Convection ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Common Center ◽  
Deep Moist Convection ◽  
Convective Vortices

Abstract A set of multiscale, nested, idealized numerical simulations of mesoscale convective systems (MCSs) and mesoscale convective vortices (MCVs) was conducted. The purpose of these simulations was to investigate the dependence of MCV development and evolution on background conditions and to explore the relationship between MCVs and larger, moist baroclinic cyclones. In all experiments, no mesoscale convective system (MCS) developed until a larger-scale, moist baroclinic system with surface pressure amplitude of at least 2 hPa was present. The convective system then enhanced the development of the moist baroclinic system by its diabatic production of eddy available potential energy (APE), which led to the enhanced baroclinic conversion of basic-state APE to eddy APE. The most rapid potential vorticity (PV) development occurred in and just behind the leading convective line. The entire system grew upscale with time as the newly created PV rotated cyclonically around a common center as the leading convective line continued to expand outward. Ten hours after the initiation of deep moist convection, the simulated MCV radii, heights of maximum winds, tangential velocity, and shear corresponded reasonably well to their counterparts in BAMEX. The increasing strength of the simulated MCVs with respect to larger values of background CAPE and shear supports the hypothesis that as long as convection is present, CAPE and shear both add to the strength of the MCV.

scholarly journals Comparison between Low-Flash and Non-Lightning-Producing Convective Areas within a Mature Mesoscale Convective System

2011 ◽  
Vol 26 (4) ◽  
pp. 468-486 ◽  
Author(s):  
Jennifer L. Palucki ◽  
Michael I. Biggerstaff ◽  
Donald R. MacGorman ◽  
Terry Schuur
Keyword(s):  
Vertical Motion ◽  
Mesoscale Convective System ◽  
Phase Region ◽  
Life Cycles ◽  
Radar Reflectivity ◽  
Mixed Phase ◽  
Convective System ◽  
Lightning Flash ◽  
Mesoscale Convective ◽  
Mixed Phase Region

Abstract Two small multicellular convective areas within a larger mesoscale convective system that occurred on 20 June 2004 were examined to assess vertical motion, radar reflectivity, and dual-polarimetric signatures between flash and non-flash-producing convection. Both of the convective areas had similar life cycles and general structures. Yet, one case produced two flashes, one of which may have been a cloud-to-ground flash, while the other convective area produced no flashes. The non-lightning-producing case had a higher peak reflectivity up to 6 km. Hence, if a reflectivity-based threshold were used as a precursor to lightning, it would have yielded misleading results. The peak upward motion in the mixed-phase region for both cases was 8 m s−1 or less. However, the lightning-producing storm contained a wider region where the updraft exceeded 5 m s−1. Consistent with the broader updraft region, the lightning-producing case exhibited a distinct graupel signature over a broader region than the non-lightning-producing convection. Slight differences in vertical velocity affected the quantity of graupel present in the mixed-phase region, thereby providing the subtle differences in polarimetric signatures that were associated with lightning activity. If the results here are generally applicable, then graupel volume may be a better precursor to a lightning flash than radar reflectivity. With the dual-polarimetric upgrade to the national observing radar network, it should be possible to better distinguish between lightning- and non-lightning-producing areas in weak convective systems that pose a potential safety hazard to the public.

scholarly journals A Subtropical Oceanic Mesoscale Convective Vortex Observed during SoWMEX/TiMREX

2011 ◽  
Vol 139 (8) ◽  
pp. 2367-2385 ◽  
Author(s):  
Hsiao-Wei Lai ◽  
Christopher A. Davis ◽  
Ben Jong-Dao Jou
Keyword(s):  
Vertical Wind Shear ◽  
Mesoscale Convective System ◽  
Southwest Monsoon ◽  
Convective System ◽  
Vortex Center ◽  
Moist Convection ◽  
Low Level ◽  
Mesoscale Convective ◽  
Deep Moist Convection ◽  
Mesoscale Convective Vortex

AbstractThis study examines a subtropical oceanic mesoscale convective vortex (MCV) that occurred from 1800 UTC 4 June to 1200 UTC 6 June 2008 during intensive observing period (IOP) 6 of the Southwest Monsoon Experiment (SoWMEX) and the Terrain-influenced Monsoon Rainfall Experiment (TiMREX). A dissipating mesoscale convective system reorganized within a nearly barotropic vorticity strip, which formed as a southwesterly low-level jet developed to the south of subsiding easterly flow over the southern Taiwan Strait. A cyclonic circulation was revealed on the northern edge of the mesoscale rainband with a horizontal scale of 200 km. An inner subvortex, on a scale of 25–30 km with maximum shear vorticity of 3 × 10−3 s−1, was embedded in the stronger convection. The vortex-relative southerly flow helped create local potential instability favorable for downshear convection enhancement. Strong low-level convergence suggests that stretching occurred within the MCV. Higher θe air, associated with significant potential and conditional instability, and high reflectivity signatures near the vortex center suggest that deep moist convection was responsible for the vortex stretching. Dry rear inflow penetrated into the MCV and suppressed convection in the upshear direction. A mesolow was also roughly observed within the larger vortex. The presence of intense vertical wind shear in the higher troposphere limited the vortex vertical extent to about 6 km.

scholarly journals Diurnal Variation of TRMM/LIS Lightning Flash Radiances

2017 ◽  
Vol 98 (7) ◽  
pp. 1453-1470 ◽  
Author(s):  
Themistoklis Chronis ◽  
William J. Koshak
Keyword(s):  
Diurnal Variation ◽  
Mesoscale Convective System ◽  
Tropical Rainfall Measuring Mission ◽  
The United States ◽  
Global Scale ◽  
Diurnal Variations ◽  
Convective System ◽  
Lightning Flash ◽  
Mesoscale Convective ◽  
Imaging Sensor

Abstract This study provides, for the first time, an analysis of the climatological diurnal variations in the lightning flash radiance data product ε from the Tropical Rainfall Measuring Mission Lightning Imaging Sensor (TRMM/LIS). The ε values over 13 years (2002–14), and over a global scale (∼38°S–38°N), reveal novel and remarkably consistent regional and seasonal patterns as a function of the local solar time (LST). In particular, the diurnal variation of ε (over both continental and oceanic regions) is characterized by a monotonic increase from late afternoon (∼2000 LST), attaining a maximum around 0900 LST, followed by a decreasing trend. The continental (oceanic) ε values reach a broader minimum spanning from ∼1500 to 1900 LST (∼1800 to 2000). The relative diurnal amplitude variation in continental ε is about 45%, compared to about 15% for oceanic ε. This study confirms that the results are not affected by diurnal biases associated with instrument detection or other statistical artifacts. Notable agreement is shown between the diurnal variations of ε and the global-scale (∼38°S–38°N) mesoscale convective system areal extent. Comparisons with recently published diurnal variations of cloud-to-ground lightning peak current over the United States also exhibit a marked similarity. Given the novelty of these findings, a few tentative hypotheses about the underlying physical mechanism(s) are discussed.

scholarly journals Evaluation of a Cloud-Scale Lightning Data Assimilation Technique and a 3DVAR Method for the Analysis and Short-Term Forecast of the 29 June 2012 Derecho Event

2014 ◽  
Vol 142 (1) ◽  
pp. 183-202 ◽  
Author(s):  
Alexandre O. Fierro ◽  
Jidong Gao ◽  
Conrad L. Ziegler ◽  
Edward R. Mansell ◽  
Donald R. MacGorman ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Computational Cost ◽  
Mesoscale Convective System ◽  
Radar Reflectivity ◽  
Convective System ◽  
Variational Technique ◽  
Short Term ◽  
Short Term Forecast ◽  
Term Forecast ◽  
Mesoscale Convective

Abstract This work evaluates the short-term forecast (≤6 h) of the 29–30 June 2012 derecho event from the Advanced Research core of the Weather Research and Forecasting Model (WRF-ARW) when using two distinct data assimilation techniques at cloud-resolving scales (3-km horizontal grid). The first technique assimilates total lightning data using a smooth nudging function. The second method is a three-dimensional variational technique (3DVAR) that assimilates radar reflectivity and radial velocity data. A suite of sensitivity experiments revealed that the lightning assimilation was better able to capture the placement and intensity of the derecho up to 6 h of the forecast. All the simulations employing 3DVAR, however, best represented the storm’s radar reflectivity structure at the analysis time. Detailed analysis revealed that a small feature in the velocity field from one of the six selected radars in the original 3DVAR experiment led to the development of spurious convection ahead of the parent mesoscale convective system, which significantly degraded the forecast. Thus, the relatively simple nudging scheme using lightning data complements the more complex variational technique. The much lower computational cost of the lightning scheme may permit its use alongside variational techniques in improving severe weather forecasts on days favorable for the development of outflow-dominated mesoscale convective systems.

Probing a post monsoon Mesoscale Convective System (MCS) and the generated Transient Luminous Events (TLEs) over Indian Region

2020 ◽  
Author(s):  
Sidha Sankalpa Moharana ◽  
Rajesh Singh
Keyword(s):  
Convective Available Potential Energy ◽  
Mesoscale Convective System ◽  
Lower Atmosphere ◽  
Space Environment ◽  
Mature Stage ◽  
Convective System ◽  
Lightning Flash ◽  
Monsoon Period ◽  
Post Monsoon ◽  
Mesoscale Convective

<p>A Mesoscale Convective System (MCS), consisting of three Super Cells<br>formed over South-east Indian, is assessed in detail with satellite and ground based<br>data-sets. The MCS under investigation generated a total of Ten (10) upward<br>electrical discharges (9 Sprites and 1 Gigantic Jet) commonly named as Transient<br>Luminous Events (TLEs). The TLEs were recorded from TLE observation station<br>located at Allahabad, India. The event occurred in the Post-Monsoon period of 2013<br>on October 7, during 15-23 UT hours. The MCS was spread over a region of 25000 sq.<br>Kilometers. A lowest cloud top temperature value of -84.7 0 C was observed in the<br>mature stage of the MCS, during 2130 UT hours, and the cloud top altitude was<br>reaching 17.6 km. The coldest cloud top region was covering an average area of<br>13000 sq. Km. The measured Convective Available Potential Energy (CAPE) value was<br>606.9 J/kg at 00 UT on 7 th October which dropped to 211 J/kg at 00 UT on 8 th<br>October. The mean lightning flash rate during the formation and maturity stages of<br>the MCS was around 46.03 min -1 . During the entire lifespan of the thunderstorm,<br>peak currents were found to be reaching ±400 kA. Such high electric currents,<br>extreme cold temperature and towering altitudes of the convective complexes show<br>how much a MCS is dynamically active and the TLEs which it produced are known to<br>electrically connect the lower atmosphere to the upper space environment.</p>

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