Satellite-Observed Cloud-Top Height Changes in Tornadic Thunderstorms

Adler, Robert F.; Fenn, Douglas D.

doi:10.1175/1520-0450(1981)020<1369:socthc>2.0.co;2

Cited by 23 publications

(13 citation statements)

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“…where (@T/@z) is the environmental lapse rate, and dT B /dt is the satellite observed time rate of change of T B from the 10.8 mm MSG "window" channel (under the assumption that T % T B as the observed cloud top temperature). This relationship produces an average w on a horizontal scale of 1-3 km [Adler and Fenn, 1981]. Therefore, the w obtained from MSG will be significantly lower than that observed in real clouds, due to the fact that most updrafts are on scales of 100 to 1000 m 2 , leading to significant smoothing when observed in 3-4 km resolution data.…”

Section: Resultsmentioning

confidence: 92%

“…Alternatively, if an updraft from a convective cloud were to reach horizontal scales of 3–4 km 2 , the 10.8 µm cloud top cooling rates would more closely relate to updraft strength ( w ) by the relationship [from Adler and Fenn , , ]:

w = - {((), - \frac{\partial T}{\partial z})}^{- 1} (\frac{normald T_{B}}{normald t}),

where (∂ T /∂ z ) is the environmental lapse rate, and d T B /d t is the satellite observed time rate of change of T B from the 10.8 µm MSG “window” channel (under the assumption that T ≈ T B as the observed cloud top temperature). This relationship produces an average w on a horizontal scale of 1–3 km [ Adler and Fenn , ]. Therefore, the w obtained from MSG will be significantly lower than that observed in real clouds, due to the fact that most updrafts are on scales of 100 to 1000 m 2 , leading to significant smoothing when observed in 3–4 km resolution data.…”

Section: Resultsmentioning

confidence: 99%

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Geostationary infrared methods for detecting lightning‐producing cumulonimbus clouds

Matthee

Mecikalski

2013

JGR Atmospheres

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[1] This study documents the behavior of cloud top infrared (IR) fields known to describe physical processes associated with growing convective clouds, for 30 nonlightning and 33 cloud-to-ground (CG) lightning-producing convective storms. The goal is to define "critical" threshold values for up to 10 IR fields that delineate lightning from nonlightning convective storms. Meteosat Second Generation and United Kingdom Meteorological Office very low frequency arrival time difference satellite and lightning data, respectively, were used in this study. These were collected during the National Aeronautics and Space Administration (NASA) African Monsoon Multidisciplinary Analyses (NAMMA) field campaign in August-September 2006 in Equatorial Africa. The main conclusions show that eight of 10 IR fields that describe updraft strength, cloud depth, and glaciation (or ice at cloud top) are significantly different between the nonlightning and lightning-producing convective clouds. The lack of notch overlap in "box and whiskers" plots confirms a 95% confidence that the two data sets are different. Nonlightning-producing clouds are far less vertically developed and possess >50% weaker updrafts (as estimated from satellite trends), as well as little to no evidence of ice or glaciation at cloud top. Results from this study therefore can be used to nowcast and identify with high confidence convective clouds that are producing or are going to produce CG lightning using Meteosat data, assuming appropriate tracking of growing cumulus clouds is performed.

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Section: Resultsmentioning

confidence: 92%

w = - {((), - \frac{\partial T}{\partial z})}^{- 1} (\frac{normald T_{B}}{normald t}),

Section: Resultsmentioning

confidence: 99%

Geostationary infrared methods for detecting lightning‐producing cumulonimbus clouds

Matthee

Mecikalski

2013

JGR Atmospheres

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“…They showed that the satellite-derived parameters of minimum Cloud-Top Temperature (CTT) and rate of cold area expansion discriminated severe from nonsevere convective clouds. They further showed (Adler and Fenn, 1979b) how vertical velocity may be derived from rapid-interval infrared (IR) observations of cloud-top ascent and thus be used as an indicator of thunderstorm intensity. High temporal frequency (3-5 min) data are crucial to the study of vigorous convection by nature of the high variability in cloud-top height, especially during the growth phase.…”

Section: Introductionmentioning

confidence: 99%

“…10, October 1982 2. Evolution of individual tornadic storms In this analysis, storms are defined by the location of IR blackbody temperature (7BB) minima that display temporal continuity (Adler and Fenn, 1979b) and that have an associated low-level radar reflectivity maximum. (See, for example the Wichita Falls storm at 2355 GMT in the color imagery on the cover.)…”

Section: Introductionmentioning

confidence: 99%

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Cloud-top Structure of Tornadic Storms on 10 April 1979 from Rapid Scan and Stereo Satellite Observations1

Negri

1982

Bulletin of the American Meteorological Society

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The cloud top structure of the Wichita Falls tornadic storm of 10 April 1979 (and other severe storms on this day) is studied using remotely-sensed observations from radar and satellite. A comprehensive data set included 3 min interval visible (0.6 μm) and infrared (11 μm) radiances from the eastern GOES and similar 30 min interval data from the western GOES. The near synchronization of these two satellites allowed for the stereoscopic determination of cloud top heights. In addition, at 2048 GMT, TIROS-N scanned the storms within one minute of the geosynchronous stereo and provided 1 km resolution infrared blackbody temperatures. Because internal storm dynamics are hidden from the view of the satellite, storm updraft intensity must be inferred from cloud-top minimum temperature and its rate of change. The Wichita Falls, Tex. tornadic storm could be defined in the satellite data by a point of minimum temperature which displayed temporal continuity and achieved a temperature of 208 K. A cloud-top cooling rate above the tropopause of 7 K/21 min preceded tornadogenesis. An adjacent warm area (221 K) developed downwind and was surrounded by a “V”-shaped pattern of lower temperatures. The warm area is postulated as due to subsidence in the lee of an ascending tower. The measured stereo height of the Wichita Falls storm was 15.6 km at 2349 GMT, 1.5 km higher than severe storms 150 km downwind, although its minimum blackbody temperature was 9 K higher than that of these downwind storms. In addition, unrealistic fluctuations in the time sequence of temperature 30 min prior to the Wichita Falls tornado indicate that the IR measurements are affected by sensor response and/or field of view limitations, at least close to the anvil edge. Cross sections of stereo heights, IR temperature, and radar reflectivity at 2349 GMT demonstrate that while there is, in general, a co-location of high tops, low temperatures, and high low-level radar reflectivity, significant variations can exist in height/rainfall relationships. A comparison of data sets at 2048 GMT between stereo height measurements and IR temperatures from GOES-East and TIROS-N revealed that anvil top features can be up to 10 K warmer in the GOES field of view (100 km2) than from TIROS-N (1 km2), and that this difference can reach 20 K for young thunderstorms, with perhaps 4 K explained by calibration differences. The lapse rate for tops penetrating the tropopause was substantially closer to the adiabatic lapse rate when TIROS-N temperature minima, rather than GOES minima, were plotted as a function of stereo determined height.

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Electrical discharges in the overshooting tops of thunderstorms

2017

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Previous studies have found that the vertical distribution of sources of very high frequency (VHF) signals from discharges mapped by Lightning Mapping Arrays typically have a secondary maximum in a storm's overshooting top. Low rates of these sources tend to occur continually throughout the lifetime of the overshooting top (OT), rather than sources occurring in the episodic distinct flashes observed at lower altitudes. This study examines the evolution of the VHF OT signature (VHF OT, defined here as a sustained period of ≥4 VHF sources per minute per 200 m layer above a storm's level of neutral buoyancy (LNB)) relative to the evolution of radar reflectivity and IR imagery of overshooting tops in three supercell and two multicell storms. The VHF OT began before OTs were detected in IR satellite imagery of the supercell storms. No OT was observed in IR imagery for either multicell storm, but this lack may have been due to the spatial and temporal resolution of the current IR imager. The VHF OT began near the time the 18 or 30 dBZ echo top rose above the LNB and ended near the time it fell below the LNB. There were too few radar volume scans of OTs in the multicell storms for a correlation analysis. In the supercell storms, however, the maximum altitude of VHF sources typically was less than or equal to the altitude of 18 dBZ echo tops and was correlated with these echo tops (linear correlation coefficient ≥0.86) during the period of the VHF OT.

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Satellite-Observed Cloud-Top Height Changes in Tornadic Thunderstorms

Cited by 23 publications

References 7 publications

Geostationary infrared methods for detecting lightning‐producing cumulonimbus clouds

Geostationary infrared methods for detecting lightning‐producing cumulonimbus clouds

Cloud-top Structure of Tornadic Storms on 10 April 1979 from Rapid Scan and Stereo Satellite Observations1

Electrical discharges in the overshooting tops of thunderstorms

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