Note: This page contains sample records for the topic summer convective storms from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Convective storms in planetary atmospheres  

NASA Astrophysics Data System (ADS)

The atmospheres of the planets in the Solar System have different physical properties that in some cases can be considered as extreme when compared with our own planet's more familiar atmosphere. From the tenuous and cold atmosphere of Mars to the dense and warm atmosphere of Venus in the case of the terrestrial planets, to the gigantic atmospheres of the outer planets, or the nitrogen and methane atmosphere of Saturn's moon Titan, we can find a large variety of physical environments. The comparative study of these atmospheres provides a better understanding of the physics of a geophysical fluid. In many of these worlds convective storms of different intensity appear. They are analogous to terrestrial atmospheres fed by the release of latent heat when one of the gases in the atmosphere condenses and they are therefore called moist convective storms. In many of these planets they can produce severe meteorological phenomena and by studying them in a comparative way we can aspire to get a further insight in the dynamics of these atmospheres even beyond the scope of moist convection. A classical example is the structure of the complex systems of winds in the giant planets Jupiter and Saturn. These winds are zonal and alternate in latitude but their deep structure is not accessible to direct observation. However the behaviour of large--scale convective storms vertically extending over the "weather layer" allows to study the buried roots of these winds. Another interesting atmosphere with a rather different structure of convection is Titan, a world where methane is close to its triple point in the atmosphere and can condense in bright clouds with large precipitation fluxes that may model part of the orography of the surface making Titan a world with a methane cycle similar to the hydrological cycle of Earth's atmosphere.

Hueso, R.; Sánchez-Lavega, A.

2013-05-01

2

Towards an offline parameterization of convective dust storms  

NASA Astrophysics Data System (ADS)

Around half of dust emissions worldwide originate from the Sahel and Sahara regions, of which a major but uncertain fraction are caused by convectively-generated dust storms (haboobs). In these storms, evaporation-driven downdrafts form cold pools that quickly propagate and create near-surface wind gusts. Current global models do not capture such storms, because their convection schemes do not allow effective formation of such cold pools. We suggest a parameterization of near-surface wind gusts and dust emissions generated by cold pools, based on the downdraft mass flux from the convection scheme. It assumes the horizontal dispersion of all downdrafts into cold pools and the unknown geometry of the cold pools results in one free parameter. The parameterization is applied to Unified Model (Cascade) runs for the 2006 Summer in West Africa. The free parameter is tuned for 40-km and 12-km runs with convection scheme, using 4-km convection-permitting runs as a reference (4-km runs have been evaluated using 1.5-km runs in previous studies). The parameterization successfully increases the near-surface wind beyond the threshold for dust emission and compensates for the lack of convectively-generated dust storms when the convection scheme is activated. The long-standing problem of too early activation of the convection scheme in the Sahel and Sahara regions remains an issue in the parameterization of the diurnal cycle of dust emissions. This parameterization is developed in the framework of the ERC Desert Storms project.

Pantillon, Florian; Knippertz, Peter; Marsham, John; Birch, Cathryn

2014-05-01

3

Interactions between convective storms and their environment  

NASA Technical Reports Server (NTRS)

The ways in which intense convective storms interact with their environment are considered for a number of specific severe storm situations. A physical model of subcloud wind fields and vertical wind profiles was developed to explain the often observed intensification of convective storms that move along or across thermal boundaries. A number of special, unusually dense, data sets were used to substantiate features of the model. GOES imagery was used in conjunction with objectively analyzed surface wind data to develop a nowcast technique that might be used to identify specific storm cells likely to become tornadic. It was shown that circulations associated with organized meso-alpha and meso-beta scale storm complexes may, on occasion, strongly modify tropospheric thermodynamic patterns and flow fields.

Maddox, R. A.; Hoxit, L. R.; Chappell, C. F.

1979-01-01

4

Principles of Convection III: Shear and Convective Storms  

NSDL National Science Digital Library

This module discusses the role of wind shear in the structure and evolution of convective storms. Using the concept of horizontal vorticity, the module demonstrates how shear enhances uplift, leading to longer-lived supercell and multicell storms. The module also explores the role of shear in the development of mesoscale convective systems, including bow echoes and squall lines. Most of the material in this module previously appeared in the COMET modules developed with Dr. Morris Weisman. This version includes a concise summary for quick reference and a final exam to test your knowledge.

Spangler, Tim

2003-10-01

5

Urban Aerosol Impacts on Downwind Convective Storms  

Microsoft Academic Search

The impacts of urban-enhanced aerosol concentrations on convective storm development and precipita- tion over and downwind of St. Louis, Missouri, are investigated. This is achieved through the use of a cloud-resolving mesoscale model, in which sophisticated land use processes and aerosol microphysics are both incorporated. The results indicate that urban-forced convergence downwind of the city, rather than the presence of

Susan C. van den Heever; William R. Cotton

2007-01-01

6

Moist convective storms in the atmosphere of Saturn  

Microsoft Academic Search

Moist convective storms might be a key aspect in the global energy budget of the atmospheres of the Giant Planets. In spite of its dull appearance, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots, the last of them arising in 1990 triggered a planetary scale disturbance that encircled the whole

R. Hueso; A. Sánchez-Lavega

2003-01-01

7

A Convective Storm Matrix: Buoyancy/Shear Dependencies  

NSDL National Science Digital Library

In order to help forecasters build a strategy for anticipating convective storm structures, their evolution, and the potential for severe weather, A Convective Storm Matrix provides learners the opportunity for extensive exploration of the relationship between a storm's environment and its structure. The matrix is composed of 54 four-dimensional numerical simulations based on the interactions of 16 different hodographs and 4 thermodynamic profiles. By comparing animated displays of these simulations, learners are able to discern the influences of varying buoyancy and vertical wind shear profiles on storm structure and evolution. A series of questions guides the exploration and helps to reveal key storm/environment relationships evident in the matrix. A synopsis of the physical processes that control storm structure, as well as the current conceptual models of key convective storms types, is included for reference.

Spangler, Tim

1998-01-01

8

Mixing length controls on high resolution simulations of convective storms  

NASA Astrophysics Data System (ADS)

Convective storms are a crucially important forecasting problem in the UK, not least because of the flooding they can cause. In the last few years many operational weather centres have begun to run at "convection permitting" resolutions, with the UK Met Office currently running a 1.5 km forecast model. While there is evidence that precipitation forecasts at this resolution are more accurate than lower resolution forecasts, it is clear that there are still significant shortcomings in the nature of the simulated convective cells at this resolution. Cells in the model tend to be too large and too intense, and tend not to organise into mesoscale complexes as observed, illustrating our lack of understanding of the nature of small-scale mixing and microphysical processes. The DYMECS (Dynamical and Microphysical Evolution of Convective Storms) project has obtained a large database of convective storm lifecycles by tracking storms with the Chilbolton Advanced Meteorological Radar. Individual storms were tracked on 40 days using a combination of scanning techniques to extract the dynamical and microphysical properties of the storm (such as storm size, vertical velocity, maximum surface rain-rate and hail intensity). In this study we perform simulations of some of the DYMECS cases with the Met Office Unified Model (UM) at horizontal grid lengths ranging from 1.5 km to 200 m, which allows us to apply a statistical approach to evaluate the properties and evolution of the simulated storms over a range of conditions. Here we present results comparing the storm morphology in the model and reality which show that the simulated storms become smaller as resolution increases and that the resolution that fits the observations best changes with the size of the observed cells. We investigate the sensitivity of storm morphology in the model to the mixing length used in the subgrid Smagorinsky mixing scheme. As the subgrid mixing length is decreased, the number of small storms with high area-averaged rain rates increases.

Hanley, Kirsty; Plant, Bob; Lean, Humphrey; Halliwell, Carol; Stein, Thorwald; Hogan, Robin

2013-04-01

9

3D Simulations of methane convective storms on Titan's atmosphere  

NASA Astrophysics Data System (ADS)

The arrival of the Cassini/Huygens mission to Titan has opened an unprecedented opportunity to study the atmosphere of this satellite. Under the pressure-temperature conditions on Titan, methane, a large atmospheric component amounting perhaps to a 3-5% of the atmosphere, is close to its triple point, potentially playing a similar role as water on Earth. The Huygens probe has shown a terrain shaped by erosion of probably liquid origin, suggestive of past rain. On the other hand, Voyager IRIS spectroscopic observations of Titan imply a saturated atmosphere of methane (amounting perhaps to 150 covered by methane clouds, if we think on Earth meteorology. However, observations from Earth and Cassini have shown that clouds are localized, transient and fast evolving, in particular in the South Pole (currently in its summer season). This might imply a lack of widespread presence on Titan of nuclei where methane could initiate condensation and particle growth with subsequent precipitation. We investigate different scenarios of moist convective storms on Titan using a complete 3D atmospheric model that incorporates a full microphysics treatment required to study cloud formation processes under a saturated atmosphere with low concentration of condensation nuclei. We study local convective development under a variety of atmospheric conditions: sub-saturation, super-saturation, abundances of condensation nuclei fall, condensation nuclei lifted from the ground or gently falling from the stratosphere. We show that under the appropriate circumstances, precipitation rates comparable to typical tropical storms on Earth can be found. Acknowledgements: This work has been funded by Spanish MCYT PNAYA2003-03216, fondos FEDER and Grupos UPV 15946/2004. R. Hueso acknowledges a post-doc fellowship from Gobierno Vasco.

Hueso, R.; Sánchez-Lavega, A.

2005-08-01

10

Late-summer Martian Dust Storm  

NASA Technical Reports Server (NTRS)

This is an image of Mars taken from orbit by the Mars Reconnaissance Orbiter's Mars Color Imager (MARCI). The Red Planet's polar ice-cap is in the middle of the image. Captured in this image is a 37,000 square-kilometer (almost 23,000 miles) dust storm that moved counter-clockwise through the Phoenix landing site on Oct 11, 2008, or Sol 135 of the mission.

Viewing this image as if it were the face of a clock, Phoenix is shown as a small white dot, located at about 10 AM. The storm, which had already passed over the landing site earlier in the day, is located at about 9:30 AM.

2008-01-01

11

Moist convective storms in the atmosphere of Saturn  

NASA Astrophysics Data System (ADS)

Moist convective storms might be a key aspect in the global energy budget of the atmospheres of the Giant Planets. In spite of its dull appearance, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots, the last of them arising in 1990 triggered a planetary scale disturbance that encircled the whole Equatorial region. However, Saturn seems to be very much less convective than Jupiter, being convective storms rare and small for the most part of the cases. Here we present simulations of moist convective storms in the atmosphere of Saturn at different latitudes, the Equator and 42 deg S, the regions where most of the convective activity of the planet has been observed. We use a 3D anelastic model of the atmosphere with parameterized microphysics (Hueso and Sánchez-Lavega, 2001) and we study the onset and evolution of moist convective storms. Ammonia storms are able to develop only if the static stability of the upper atmosphere is slightly decreased. Water storms are difficult to develop requiring very specific atmospheric conditions. However, when they develop they can be very energetic arriving at least to the 150 mbar level. The Coriolis forces play a mayor role in the characteristics of water based storms in the atmosphere of Saturn. The 3-D Coriolis forces at the Equator transfer upward momentum to westward motions acting to diminish the strength of the equatorial jet. The GWS of 1990 could have been a mayor force in reducing the intensity of the equatorial jet stream as revealed recently (Sánchez-Lavega et al. Nature, 2003). The Cassini spacecraft will arrive to Saturn in a year. Its observations of the atmosphere will allow to measure the amount of convective activity on the planet, its characteristics and it will clarify the role of moist convection in the atmospheric dynamics of the Giant Planets. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. RH acknowledges a Post-doctoral fellowship from Gobierno Vasco.

Hueso, R.; Sánchez-Lavega, A.

2003-05-01

12

Severe local convective storms in Bangladesh: Part II.: Environmental conditions  

NASA Astrophysics Data System (ADS)

This paper examines the environmental conditions of severe local convective storms during the pre-monsoon season (from March to May) in Bangladesh. We compared composite soundings on severe local convective storm days (SLCSD) with those on non-severe local convective storm days (NSLCSD) using rawinsonde data at 06 Bangladesh Standard Time (BST) in Dhaka (90.3°E and 23.7°N). Temperatures are rising in the lower layer and falling in the middle layer, and the amount of water vapor is significantly increasing in the lowest layer with southerly wind intensified on SLCSD compared with NSLCSD. This situation produces great thermal instability in the atmosphere on SLCSD. Convective parameters on SLCSD are computed with the rawinsonde data at 06 BST in Dhaka and compared with those on NSLCSD. The comparison shows that while most convective parameters related to thermal instability can discriminate between SLCSD and NSLCSD with statistical significance, no convective parameters related to the vertical wind shear can distinguish between the two categories. We evaluated the forecast skill of the convective parameters using Heidke Skill Score (HSS). The evaluation shows that the HSS for the Lifted Index and Precipitable Water are better among all parameters and have great forecast ability.

Yamane, Yusuke; Hayashi, Taiichi; Dewan, Ashraf Mahmmood; Akter, Fatima

2010-03-01

13

Relationship between surface conditions and subsequent rainfall in convective storms  

NASA Astrophysics Data System (ADS)

This paper describes the relationship between surface conditions (temperature and humidity) and subsequent rainfall. The focus is on convective storms that are forced and maintained locally due to conditional instability in the vertical distribution of atmospheric temperature. These storms are described using two probabilistic measures: (1) the probability of occurrence of storms given surface conditions and (2) the average storm rainfall. The surface conditions are described by a single variable: surface wet-bulb temperature. The proposed theoretical relationships are tested using an hourly data set on rainfall and wet-bulb temperature from the Amazon region. These observations confirm that both measures increase linearly with wet-bulb temperature. However, for the occurrence of any storm the wet-bulb temperature has to exceed a threshold of about 22°C. The sensitivity of the frequency of storms to changes in the climatology of surface wet-bulb temperature is larger than the corresponding sensitivity of the average storm rainfall. These general concepts are applied in discussing the potential impact of changes in land cover on rainfall patterns using two specific examples: deforestation in the Amazon region and development of irrigation projects in the Columbia River basin.

Eltahir, Elfatih A. B.; Pal, Jeremy S.

1996-11-01

14

Convective storm downdraft outflows detected by NASA/MSFC's Airborne 10.6 micron pulsed Doppler Lidar System  

NASA Technical Reports Server (NTRS)

The capability of a unique Airborne Doppler Lidar System to measure the horizontal winds in the vicinity of severe storm activity is demonstrated. The Airborne Doppler Lidar System (ADLS), developed at NASA/MSFC, was flown on a CV990 research aircraft during the CCOPE (Cooperative Convective Precipitation Experiments, Montana, Summer 1981). Flown between 400 and 600 m AGL, the lidar probed the subcloud regions of several deep convection storms. ADLS data collected near storms on 21 and 23 July 1981 are presented along with satellite imagery, radar echo maps and surface station measurements. These case studies are evidence of the successful performance of an airborne remote wind sensing system and the advantages of two dimension flow visualization of storm outflow structures and interactions.

Emmitt, G. D.

1985-01-01

15

A-Train Observations of Deep Convective Storm Tops  

NASA Technical Reports Server (NTRS)

The paper highlights simultaneous observations of tops of deep convective clouds from several space-borne instruments including the Moderate Resolution Imaging Spectroradiometer (MODIS) of the Aqua satellite, Cloud Profiling Radar (CPR) of the CloudSat satellite, and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) flown on the CALIPSO satellite. These satellites share very close orbits, thus together with several other satellites they are referred to as the "A-Train" constellation. Though the primary responsibility of these satellites and their instrumentation is much broader than observations of fine-scale processes atop convective storms, in this study we document how data from the A-Train can contribute to a better understanding and interpretation of various storm-top features, such as overshooting tops, cold-U/V and cold ring features with their coupled embedded warm areas, above anvil ice plumes and jumping cirrus. The relationships between MODIS multi-spectral brightness temperature difference (BTD) fields and cloud top signatures observed by the CPR and CALIOP are also examined in detail to highlight the variability in BTD signals across convective storm events.

Setvak, Martin; Bedka, Kristopher; Lindsey, Daniel T.; Sokol, Alois; Charvat, Zdenek; Stastka, Jindrich; Wang, Pao K.

2013-01-01

16

A-Train observations of deep convective storm tops  

NASA Astrophysics Data System (ADS)

The paper highlights simultaneous observations of tops of deep convective clouds from several space-borne instruments including the Moderate Resolution Imaging Spectroradiometer (MODIS) of the Aqua satellite, Cloud Profiling Radar (CPR) of the CloudSat satellite, and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) flown on the CALIPSO satellite. These satellites share very close orbits, thus together with several other satellites they are referred to as the "A-Train" constellation. Though the primary responsibility of these satellites and their instrumentation is much broader than observations of fine-scale processes atop convective storms, in this study we document how data from the A-Train can contribute to a better understanding and interpretation of various storm-top features, such as overshooting tops, cold-U/V and cold ring features with their coupled embedded warm areas, above anvil ice plumes and jumping cirrus. The relationships between MODIS multi-spectral brightness temperature difference (BTD) fields and cloud top signatures observed by the CPR and CALIOP are also examined in detail to highlight the variability in BTD signals across convective storm events.

Setvák, Martin; Bedka, Kristopher; Lindsey, Daniel T.; Sokol, Alois; Charvát, Zden?k; Š?ástka, Jind?ich; Wang, Pao K.

2013-04-01

17

Modes of isolated, severe convective storm formation along the dryline  

SciTech Connect

Patterns of the formation of isolated, severe convective storms along the dryline in the Southern plains of the United States during the spring over a 16-year period were determined from an examination of the evolution of radar echoes as depicted by WSR-57 microfilm data. It was found that in the first 30 min after the first echo, more than half of the radar echoes evolved into isolated storms as isolated cells from the start; others developed either from a pair of cells, from a line segment, from a cluster of cells, from the merger of mature cells, or from a squall line. Proximity soundings were constructed from both standard and special soundings, and from standard surface data. It was found that the estimated convective available potential energy and vertical shear are characteristic of the environment of supercell storms. The average time lag between the first echo and the first occurrence of severe weather of any type, or tornadoes alone, was approximately 2 h. There were no significant differences in the environmental parameters for the different modes of storm formation. 49 refs., 15 figs., 3 tabs.

Bluestein, H.B.; Parker, S.S. (Univ. of Oklahoma, Norman (United States))

1993-05-01

18

The Dynamics of Simulated Convective Storms in Hurricane Environments.  

NASA Astrophysics Data System (ADS)

Numerical simulations of convection in selected hurricane environments show that supercell storms are possible, even when buoyancy is relatively small. In one simulated supercell, the dynamic pressure force is found to reach a maximum about three times as strong as that of buoyancy in the late stages of the simulation. Updrafts reach peak intensity at low levels, often around 2-3 km AGL, and may exceed magnitudes expected from consideration of moist CAPE alone. Interactions between updraft and ambient vertical shear, and, later, growing contributions from vorticity, appear to dominate the development of the dynamic pressure field. Although the weak buoyancy tends to restrict storm intensity, a favorable matching of the vertical distribution of buoyancy with that of the vertical shear allows the pressure forces to become strong enough to take up the slack. Terms in the disturbance kinetic energy budget are correspondingly more strongly influenced by pressure effects than by buoyancy. Although the simulated supercells display the very strong, organized rotation characteristic of tornadic storms, many of the multicell storms which appear in the simulations also contain local concentrations of vorticity intense enough to suggest tornado potential. Simulations with differing background rotation (Coriolis) rates "f" show that convection which was multicellular at low f can become supercellular at higher f. The enhanced vertical vorticity that develops naturally in decaying tropical cyclones when angular momentum disperses under the influence of weakening pressure gradients may, by analogy, help explain why dissipating tropical cyclones are an especially fertile breeding ground for tornadic storms. Test simulations in which surface drag and a slightly modified subgrid mixing formulation were used show that the details of storm behavior can be quite sensitive to changes in these model parameters, although updraft and vorticity statistics are not altered greatly. In general, predictability appears to be reduced in these very moist environments.

McCaul, Eugene Williamson, Jr.

19

Particle Energization During Magnetic Storms with Steady Magnetospheric Convection  

NASA Astrophysics Data System (ADS)

Relativistic electrons pose a space weather hazard to satellites in the radiation belts. Although about half of all geomagnetic storms result in relativistic electron flux enhancements, other storms decrease relativistic electron flux, even under similar solar wind drivers. Radiation belt fluxes depend on a complex balance between transport, loss, and acceleration. A critically important aspect of radiation belt enhancements is the role of the 'seed' population--plasma sheet particles heated and transported Earthward by magnetotail processes--which can become accelerated by wave-particle interactions with chorus waves. While the effect of substorms on seed electron injections has received considerable focus, in this study we explore how quasi-steady convection during steady magnetospheric convection (SMC) events affects the transport and energization of electrons. SMC events are long-duration intervals of enhanced convection without any substorm expansions, and are an important mechanism in coupling magnetotail plasma populations to the inner magnetosphere. We detail the behavior of the seed electron population for stormtime SMC events using the Van Allen Probes in the outer radiation belt and THEMIS in the plasma sheet and inner magnetosphere. Together, the two missions provide the ability to track particle transport and energization from the plasma sheet into the radiation belts. We present SMC events with Van Allen Probes/THEMIS conjunctions and compare plasma sheet fast flows/enhanced transport to radiation belt seed electron enhancements. Finally we utilize statistical analyses to quantify the relative importance of SMC events on radiation belt electron acceleration in comparison to isolated substorms.

Kissinger, J.; Kepko, L.; Baker, D. N.; Kanekal, S. G.; Li, W.; McPherron, R. L.; Angelopoulos, V.

2013-12-01

20

Changes in concentration of Alternaria and Cladosporium spores during summer storms.  

PubMed

Fungal spores are known to cause allergic sensitization. Recent studies reported a strong association between asthma symptoms and thunderstorms that could be explained by an increase in airborne fungal spore concentrations. Just before and during thunderstorms the values of meteorological parameters rapidly change. Therefore, the goal of this study was to create a predictive model for hourly concentrations of atmospheric Alternaria and Cladosporium spores on days with summer storms in Szczecin (Poland) based on meteorological conditions. For this study we have chosen all days of June, July and August (2004-2009) with convective thunderstorms. There were statistically significant relationships between spore concentration and meteorological parameters: positive for air temperature and ozone content while negative for relative humidity. In general, before a thunderstorm, air temperature and ozone concentration increased, which was accompanied by a considerable increase in spore concentration. During and after a storm, relative humidity increased while both air temperature ozone concentration along with spore concentrations decreased. Artificial neural networks (ANN) were used to assess forecasting possibilities. Good performance of ANN models in this study suggest that it is possible to predict spore concentrations from meteorological variables 2 h in advance and, thus, warn people with spore-related asthma symptoms about the increasing abundance of airborne fungi on days with storms. PMID:23161270

Grinn-Gofro?, Agnieszka; Strzelczak, Agnieszka

2013-09-01

21

Empirical reconstruction of storm-time steady magnetospheric convection events  

NASA Astrophysics Data System (ADS)

We investigate the storm-scale morphology of the magnetospheric magnetic field as well as underlying distributions of electric currents, equatorial plasma pressure and entropy for four Steady Magnetospheric Convection (SMC) events that occurred during the May 2000 and October 2011 magnetic storms. The analysis is made using the empirical geomagnetic field model TS07D, in which the structure of equatorial currents is not predefined and it is dictated by data. The model also combines the strengths of statistical and event-oriented approaches in mining data for the reconstruction of the magnetic field. The formation of a near-Earth minimum of the equatorial magnetic field in the midnight sector is inferred from data without ad hoc assumptions of a special current system postulated in earlier empirical reconstructions. In addition, a new SMC class is discovered where the minimum equatorial field is substantially larger and located closer to Earth. The magnetic field tailward of the minimum is also much larger, and the corresponding region of accumulated magnetic flux may occupy a very short tail region. The equatorial current and plasma pressure are found to be strongly enhanced far beyond geosynchronous orbit and in a broad local time interval covering the whole nightside region. This picture is consistent with independent recent statistical studies of the SMC pressure distributions, global MHD and kinetic RCM-E simulations. Distributions of the flux tube volume and entropy inferred from data reveal different mechanisms of the magnetotail convection crisis resolution for two classes of SMC events.

Stephens, G. K.; Sitnov, M. I.; Kissinger, J.; Tsyganenko, N. A.; McPherron, R. L.; Korth, H.; Anderson, B. J.

2013-12-01

22

Empirical reconstruction of storm time steady magnetospheric convection events  

NASA Astrophysics Data System (ADS)

We investigate the storm-scale morphology of the magnetospheric magnetic field as well as underlying distributions of electric currents, equatorial plasma pressure, and entropy for four steady magnetospheric convection (SMC) events that occurred during the May 2000 and October 2011 magnetic storms. The analysis is made using the empirical geomagnetic field model TS07D, in which the structure of equatorial currents is not predefined and it is dictated by data. The model also combines the strengths of statistical and event-oriented approaches in mining data for the reconstruction of the magnetic field. The formation of a near-Earth minimum of the equatorial magnetic field in the midnight sector is inferred from data without ad hoc assumptions of a special current system postulated in earlier empirical reconstructions. In addition, a new SMC class is discovered where the minimum equatorial field is substantially larger and located closer to Earth. The magnetic field tailward of the minimum is also much larger, and the corresponding area of accumulated magnetic flux may occupy a very short tail region. The equatorial current and plasma pressure are found to be strongly enhanced far beyond geosynchronous orbit and in a broad local time interval covering the whole nightside region. This picture is consistent with independent recent statistical studies of the SMC pressure distributions, global MHD, and kinetic Rice Convection Model-Equilibrium (RCM-E) simulations. Distributions of the flux tube volume and entropy inferred from data reveal different mechanisms of the magnetotail convection crisis resolution for two classes of SMC events.

Stephens, G. K.; Sitnov, M. I.; Kissinger, J.; Tsyganenko, N. A.; McPherron, R. L.; Korth, H.; Anderson, B. J.

2013-10-01

23

Formaldehyde Photochemistry in the Upper Troposphere in and Near Convective Storms During the DC3 Study  

NASA Astrophysics Data System (ADS)

The 2012 Deep Convective Clouds and Chemistry (DC3) campaign in the summer of 2012 provided an opportunity to study the impacts of deep convection on various reactive and soluble precursors of ozone and HOx radicals in the upper troposphere and lower stratosphere over North America. Formaldehyde (CH2O) is one such gas. Formaldehyde measurements on the NASA DC-8 aircraft by difference frequency generation infrared absorption spectroscopy (DFGAS) and laser-induced fluorescence along with DFGAS measurements on the NSF/NCAR GV aircraft were acquired in the inflow and outflow of numerous storms over the course of this study. An overview of these measurements with past measurements over the continental U.S. will be given for both context and to illustrate the magnitude of CH2O perturbations caused by deep continental convection. A number of case studies were identified for comparison of these measurements with the NASA Langley Lagrangian photochemical box model and the WRF-Chem model. The former is constrained by time varying observations of CH2O precursors in both the boundary layer and upper troposphere to determine the magnitude of CH2O produced by gas-phase photochemistry in both the storm core and the outflow at various times for different storm types. These determinations will be used as a constraint on CH2O scavenging efficiency results obtained by a 3-component mixture method and as a means to assess the magnitude of potential CH2O production mechanisms from other sources such as heterogeneous production when smoke plumes intercept clouds.

Fried, A.; Weibring, P.; Richter, D.; Walega, J.; Olson, J. R.; Crawford, J. H.; Diskin, G. S.; Sachse, G. W.; Hanisco, T. F.; Arkinson, H. L.; Barth, M. C.; Campos, T. L.; Flocke, F. M.; Apel, E. C.; Hornbrook, R. S.; Hall, S. R.; Bela, M. M.; Cantrell, C. A.; Blake, D. R.; Blake, N. J.

2013-12-01

24

Plasmapause Convects to the Magnetopause During Halloween Solar Storm  

NSDL National Science Digital Library

The plasmasphere is a region of ionospheric plasma which co-rotates with the Earth, carried by the magnetic field lines. The plasmapause marks the outer boundary of this region. This colder plasma is more easily moved by the electric fields created by strong solar storms. In the Halloween 2003 event, these fields convected some of the cold plasma out to the magnetopause (grey, semi-transparent surface) and reduced the size of the cold plasma region near the Earth. For this visualization, the 3-dimensional structure was constructed from the equatorial profile of the plasmapause (as measured by IMAGE-EUV data) by extending the region along field lines of a simple dipole field.

Bridgman, Tom; Williams, James; Shirah, Greg; Goldstein, Jerald

2004-12-15

25

Initiation of a convective dust storm over North India on 21 April 2010 inferred using satellite data  

NASA Astrophysics Data System (ADS)

Dust storms commonly occur during the pre-monsoon (summer) season in north and northwest parts of India. Characteristics of dust events of the pressure gradient type are well understood. However, comprehensive studies on mechanism of convective dust storms in India are few. A convective dust storm which occurred on 21 April 2010 in association with a western disturbance over North India was hence studied. In the absence of in situ data, we used available satellite data to study the event. Dust storm that occurred on 20 April 2010 on the surface of the Thar Desert transported dust to northern and northwestern parts of India (Rajasthan, Haryana, Delhi and some parts of Uttar Pradesh). This formed a background of aerosols that affected the thunderstorm formed in association with western disturbance and the strong updraft in the thunderstorm carried the dust lingering in the atmosphere to higher altitudes. Large amount of aerosols carried to higher altitude suppressed the chance of precipitation by affecting the cloud top microphysics. Enhancement in evaporation due to an increase in aerosol concentration and strong downdrafts during dissipation of the thunderstorm resulted in emission of dust particles which led to the convective dust event of 21 April 2010.

Desouza, Nirmala Devidas; Kurchania, Rajnish; Qureshi, Muhammad Shums

2013-10-01

26

Numerical modeling of severe convective storms occurring in the Carpathian Basin  

NASA Astrophysics Data System (ADS)

Squall lines often cause serious damages due to the strong surface outflow, hail, or heavy precipitation in Hungary every summer. Squall lines in the Carpathian Basin can be classified into two main categories: pre-frontal squall-lines and frontal convective lines. In this paper, these two types of severe mesoscale phenomena are investigated using the high resolution numerical weather prediction model, the MM5. The case study for the first type of convective systems occurred on 18th May 2005 when two main convective lines with their embedded severe storms formed daytime and caused high-velocity wind events and extensive damages in the eastern part of Hungary. The second case study is a frontal squall line that hit Budapest on 20th August 2006 and the associated high precipitation (HP) supercells reached the capital of Hungary at same time when the traditional Constitution Day firework began. The consequences were catastrophic: five people were killed and more than one thousand were injured due to the extreme weather. The non-hydrostatic high resolution MM5 model was able to simulate and catch the severe weather events occurred on the days under discussion. Moreover, the model was able to compute the detailed structure of the supercells embedded in thunderstorm lines. By studying the equivalent potential temperature (EPT) fields at lower levels, we state that in the prefrontal case, there is a competition between the supercell thunderstorms for the wet and warm air. A thunderstorm that can collect the wet and warm air from larger area will have longer lifetime and more intense updraft. In the second case, the frontal squall lines, the movement and the behavior of the supercell storms embedded in the line was highly determined by the synoptic-scale motions and less affected by the EPT field of the prefrontal masses.

Horváth, Á.; Geresdi, I.; Németh, P.; Csirmaz, K.; Dombai, F.

27

Intense summer storms identified on the basis of lightning strikes in Switzerland  

NASA Astrophysics Data System (ADS)

A differentiation between the two basic types of precipitation, i.e. convective and stratiform, is of great importance in hydrological modeling and engineering practice. In this study we propose a methodology for the estimation of the character of precipitation events exclusively on the basis of local high resolution meteorological data (lightning strikes, precipitation), and not taking into consideration any information on the character of precipitation on the basis of remote measurements (radars, satellites). Identification of convective events is based on the hypothesis that thunderstorms with strong convective lifting are commonly associated with lightning. The study is based on precipitation depth measurements at a 10-min time step with a heated tipping-bucket gauge with tip resolution 0.1 mm from the SwissMetNet (MeteoSwiss) network at 63 stations that cover altitudes ranging from 200 up to 3300 m a.s.l. over the period 1981-2012 (32 years). Additionally, the same stations also measure the number of lightning strikes within a range of 30 km from the station. Although these data are available for the period 1987-2012 (25 years), we confine the lightning information to the period 1987-2005 (18 years) only, since changes made to the lightning observation methodology in the years 2005-2006 raise concerns about the homogeneity of the whole observation record. Independent rainfall events that occurred during the warm half-year (April to September) are first identified from this database, with the requirement that the inter-arrival time between two subsequent events is at least 2 hours. Then, for each rainfall event, the key storm characteristics (total rainfall depth R, storm duration D, and peak 10-min intensity I) are computed, and the number of lightning strikes is assigned in the case the event was accompanied by lightning activity. We found that peak rainfall intensity I during events accompanied by lightning is significantly higher than during those events where no lightning was observed. There are smaller differences in the distributions of event durations and rainfall totals. On this basis, we define a threshold of peak intensity I* that differentiates between events with and without lightning with an acceptably small probability of misclassification. This allows us to identify intense summer events with convective character as those where I > I* regardless of their duration or total rainfall depth. In a final step, the spatial variability of I* across the analyzed stations in Switzerland is examined. The results suggest that threshold intensities I* are not constant in space and vary with a strong topographic and climatological signature.

Gaal, Ladislav; Molnar, Peter; Szolgay, Jan

2013-04-01

28

Short-Term Forecasting of Severe Convective Storms by Using Satellite Retrieved Cloud Microstructure  

NASA Astrophysics Data System (ADS)

Severe convective storms are characterized by strong updrafts, caused by the combination of instability and wind shear. The intensity of the updrafts can be revealed by satellite observations of cloud top temperature (T) and indicated particle effective radius (Re) of the tops of the growing convective towers in developing storms. The hydrometeors have less time to develop in stronger updrafts, hence rendering Re smaller. Therefore, slower growth of Re with decreasing T is indicative of greater vigor of the storm. Observations of T-Re relations from geostationary satellites allow early detection of hail and tornadic storms. A computerized algorithm for automated early alerts of the severe convective storms showed a substantial skill in predicting the storms with a lead time of two hours. The methodology was operationally tested successfully at the Severe Storms Prediction Center in the USA during the spring of 2008. The methodology was also tested on several case studies over Europe with the METEOSAT-8 geostationary satellite in validated cases of damaging hail storms, and shows similar or better potential compared to the application in the USA, due to the better quality of the METEOSAT-8 as compared to the GOES satellites. This opens a whole new concept of using the multispectral capabilities of the METEOSAT Second Generation for identification of clouds that have the potential to become severe convective storms. The physical principle, methodology and results of the operational tests will be shown.

Rosenfeld, Daniel

2010-05-01

29

Application of the Aventech AIMMS20AQ airborne probe for turbulence measurements during the Convective Storm Initiation Project  

NASA Astrophysics Data System (ADS)

The Convective Storm Initiation Project (CSIP) took place during the summers of 2004 and 2005, centred on the research radar at Chilbolton, UK. Precursors to convective precipitation were studied, using a comprehensive and broad-based range of fieldwork and modelling. The principal aim of CSIP was the detection of the primary and secondary initiation of convective cells. The Universities Facility for Atmospheric Measurements (UFAM) Cessna 182 was used to map temperature and humidity fields over a broad area within and beyond the Chilbolton radar beam. Additionally, air motion was measured using a new turbulence probe, the AIMMS20AQ. The performance of the probe is critically appraised, based on calibrations, test flights and data flights flown during CSIP intensive operating periods. In general, the probe performed well, although some aspects require more careful data interpretation which we describe in detail.

Beswick, K. M.; Gallagher, M. W.; Webb, A. R.; Norton, E. G.; Perry, F.

2007-03-01

30

Atmospheric structure and variability in areas of convective storms determined from 3-h rawinsonde data  

NASA Technical Reports Server (NTRS)

The structure and variability of the atmosphere in areas of radar-observed convection were established by using 3-h rawinsonde and surface data from NASA's second Atmospheric Variability Experiment. Convective activity was shown to exist in areas where the low and middle troposphere is moist and the air is potentially and convectively unstable and has upward motion, in combination with positive moisture advection, at either the surface or within the boundary layer. The large variability of the parameters associated with convective storms over time intervals less than 12 h was also demonstrated so as to possibly produce a change in the probability of convective activity by a factor of 8 or more in 3 h. Between 30 and 60 percent of the total changes in parameters associated with convective activity over a 12-h period were shown to take place during a 3-h period. These large changes in parameters are related to subsynoptic-scale systems that often produce convective storms.

Wilson, G. S.; Scoggins, J. R.

1976-01-01

31

Observed and Simulated Radiative and Microphysical Properties of Tropical Convective Storms  

NASA Technical Reports Server (NTRS)

Increases in the ice content, albedo and cloud cover of tropical convective storms in a warmer climate produce a large negative contribution to cloud feedback in the GISS GCM. Unfortunately, the physics of convective upward water transport, detrainment, and ice sedimentation, and the relationship of microphysical to radiative properties, are all quite uncertain. We apply a clustering algorithm to TRMM satellite microwave rainfall retrievals to identify contiguous deep precipitating storms throughout the tropics. Each storm is characterized according to its size, albedo, OLR, rain rate, microphysical structure, and presence/absence of lightning. A similar analysis is applied to ISCCP data during the TOGA/COARE experiment to identify optically thick deep cloud systems and relate them to large-scale environmental conditions just before storm onset. We examine the statistics of these storms to understand the relative climatic roles of small and large storms and the factors that regulate convective storm size and albedo. The results are compared to GISS GCM simulated statistics of tropical convective storms to identify areas of agreement and disagreement.

DelGenio, Anthony D.; Hansen, James E. (Technical Monitor)

2001-01-01

32

Penetration Electric Fields and Magnetospheric Convection During Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

Knowledge of the magnetospheric convection electric field pattern is essential to any study of the inner magnetosphere. While a number of empirical and theoretical electric field models have been developed in the past, none of them contains a good description of the stormtime magnetospheric electric fields, in particular the electric fields that penetrate to low L-values as a result of the breakdown of the shielding near the inner edge of the ring current. The potential drop equatorward/earthward of the auroral oval/electron plasma sheet can exceed 60 kV, a substantial fraction of the total potential drop across the polar cap/magnetosphere. The Defense Meteorological Satellite Program (DMSP) spacecraft have been providing ion drift measurements in the ionosphere since 1988 as well as precipitating auroral particle measurements since 1982 and geomagnetic field measurements since 1994. At times, these measurements have been provided simultaneously by 5 separate spacecraft. We have analyzed a number of geomagnetic storms, focusing on the penetration of the stormtime electric fields to latitudes well below the equatorward edge of the electron plasma sheet. The ion drift measurements can be mapped to the magnetosphere and combined to derive realistic parameterized stormtime magnetospheric electric field patterns.

O'Brien, T. P.; Anderson, P. C.

2002-12-01

33

Penetration Electric Fields and Magnetospheric Convection During Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

Knowledge of the magnetospheric convection electric field pattern is essential to any study of the inner magnetosphere. While a number of empirical and theoretical electric field models have been developed in the past, none of them contains a good descrip- tion of the stormtime magnetospheric electric fields, in particular the electric fields that penetrate to low L-values as a result of the breakdown of the shielding near the inner edge of the ring current. The potential drop equatorward/earthward of the auroral oval/electron plasma sheet can exceed 60 kV, a substantial fraction of the total poten- tial drop across the polar cap/magnetosphere. The Defense Meteorological Satellite Program (DMSP) spacecraft have been providing ion drift measurements in the iono- sphere since 1988 as well as precipitating auroral particle measurements since 1982 and geomagnetic field measurements since 1994. At times, these measurements have been provided simultaneously by 5 separate spacecraft. We have analyzed a number of geomagnetic storms, focusing on the penetration of the stormtime electric fields to latitudes well below the equatorward edge of the electron plasma sheet. The ion drift measurements can be mapped to the magnetosphere and combined to derive a realistic stormtime magnetospheric electric field pattern driven by AE and Dst.

Anderson, P. C.

34

Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 2  

NASA Technical Reports Server (NTRS)

The parameters of the conceptual model are evaluated from the analysis of eight years of summer rainstorm data from the dense raingage network in the Walnut Gulch catchment near Tucson, Arizona. The occurrence of measurable rain at any one of the 93 gages during a noon to noon day defined a storm. The total rainfall at each of the gages during a storm day constituted the data set for a single storm. The data are interpolated onto a fine grid and analyzed to obtain: an isohyetal plot at 2 mm intervals, the first three moments of point storm depth, the spatial correlation function, the spatial variance function, and the spatial distribution of the total storm depth. The description of the data analysis and the computer programs necessary to read the associated data tapes are presented.

Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodriguez-Iturbe, I.

1986-01-01

35

Growth Of The Summer Daytime Convective Boundary Layer At Anand  

NASA Astrophysics Data System (ADS)

The heights of the daytime convective boundary layer (CBL), computed by a one-dimensional model for a bare soil surface at a semi-arid station,Anand, during the dry and hot summer month of May 1997, are presented. As input, the model requires surface heat flux, friction velocity and air temperature as functions of time. Temperature data at the one-metre level from a tower and sonic anemometer data at 9.5 m collected during the period 13-17 May 1997 in the Land Surface Processes Experiment (LASPEX-97) are used to compute hourly values of surface heat flux, friction velocity and Obukhov length following the operational method suggested by Holtslag and Van Ulden [J. Climate Appl. Meteorol. 22,517-529 (1983)]. The model has been tested with different values for the potential temperature gradient ( ) above the inversion. The model-estimated CBL heights comparefavourably with observed heights obtained from radiosonde ascents.

Nagar, S. G.; Tyagi, Ajit; Seetaramayya, P.; et al.

36

Initialization of a modeled convective storm using Doppler radar-derived fields  

NASA Technical Reports Server (NTRS)

A method is developed to initialize convective storm simulations with Doppler radar-derived fields. Input fields for initialization include velocity, rainwater derived from radar reflectivity, and pressure and temperature fields obtained through thermodynamic retrieval. A procedure has been developed to fill in missing wind data, followed by a variational adjustment to the filled wind field to minimize 'shocks' that would otherwise cause the simulated fields to deteriorate rapidly. A series of experiments using data from a simulated storm establishes the feasibility of the initialization method. Multiple-Doppler radar observations from the 20 May 1977 Del City tornadic storm are used for the initialization experiments. Simulation results are shown and compared to observations taken at a later time. The simulated storm shows good agreement with the subsequent observations, though the simulated storm appears to be evolving faster than observed. Possible reasons for the discrepancies are discussed.

Lin, Ying; Ray, Peter S.; Johnson, Kenneth W.

1993-01-01

37

Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 1  

NASA Technical Reports Server (NTRS)

Eight years of summer raingage observations are analyzed for a dense, 93 gage, network operated by the U. S. Department of Agriculture, Agricultural Research Service, in their 150 sq km Walnut Gulch catchment near Tucson, Arizona. Storms are defined by the total depths collected at each raingage during the noon to noon period for which there was depth recorded at any of the gages. For each of the resulting 428 storms, the 93 gage depths are interpolated onto a dense grid and the resulting random field is anlyzed. Presented are: storm depth isohyets at 2 mm contour intervals, first three moments of point storm depth, spatial correlation function, spatial variance function, and the spatial distribution of total rainstorm depth.

Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodrigues-Iturbe, I.

1986-01-01

38

Severe convective storm detection based on satellite infrared imagery analysis  

NASA Technical Reports Server (NTRS)

Several cases of GOES digital infrared data and Doppler Sounder array data during the three-hour time period immediately preceding the touchdown of the tornado were analyzed. Tornado-associated clouds are compared with non-tornado-associated clouds using satellite infrared data, ray tracing of gravity waves detected by the Doppler Sounder array and rawinsonde data. The satellite observations are at 15-minute intervals. Our study shows that tornado-associated clouds are always accompanied by overshooting turrets penetrating above the tropopause. The growth rate of the overshooting turret above the tropopause for severe storm-associated clouds is much greater than that for non-severe storm-associated clouds.

Hung, R. J.; Smith, R. E.

1984-01-01

39

Analysis of Severe Convective Storms Observed by Radar  

Microsoft Academic Search

A survey of thunderstorms observed during 1956 by CPS-9 radar from Blue Hill (Milton, Massachusetts) revealed a high frequency of hail occurrence (as reported by a regional network of cooperative observers) in storms in which the radar echo attained high altitudes and large values of radar reflectivity factor. Hail frequencies are related to these criteria, and to the single criterion

Ralph J. Donaldson Jr.

1958-01-01

40

Variability of the North Atlantic summer storm track: mechanisms and impacts on European climate  

NASA Astrophysics Data System (ADS)

The summertime variability of the extratropical storm track over the Atlantic sector and its links to European climate have been analysed for the period 1948-2011 using observations and reanalyses. The main results are as follows. (1) The dominant mode of the summer storm track density variability is characterized by a meridional shift of the storm track between two distinct paths and is related to a bimodal distribution in the climatology for this region. It is also closely related to the Summer North Atlantic Oscillation (SNAO). (2) A southward shift is associated with a downstream extension of the storm track and a decrease in blocking frequency over the UK and northwestern Europe. (3) The southward shift is associated with enhanced precipitation over the UK and northwestern Europe and decreased precipitation over southern Europe (contrary to the behaviour in winter). (4) There are strong ocean-atmosphere interactions related to the dominant mode of storm track variability. The atmosphere forces the ocean through anomalous surface fluxes and Ekman currents, but there is also some evidence consistent with an ocean influence on the atmosphere, and that coupled ocean-atmosphere feedbacks might play a role. The ocean influence on the atmosphere may be particularly important on decadal timescales, related to the Atlantic Multidecadal Oscillation (AMO).

Dong, Buwen; Sutton, Rowan T.; Woollings, Tim; Hodges, Kevin

2013-09-01

41

Sensitivity of Severe Convective Storms to Soil Moisture and Lower Atmospheric Water Vapor  

NASA Astrophysics Data System (ADS)

Numerous studies have examined the sensitivity of the atmospheric state to soil moisture on time scales of up to a day. Dry line intensity, lower tropospheric water vapor content, and precipitation have all been shown through modeling studies to be affected by modest perturbations to upstream soil moisture content and subsequent lower atmospheric water vapor. Since all of these aspects could be associated with convection, a high-impact forecast event that exhibits rapid nonlinear error growth, it is reasonable to expect that irrigation practices might influence severe convective storms. Understanding the link between soil moisture and specific convective elements could have broad implications for severe weather forecasting, and could reveal the degree to which irrigation-induced storm-scale inadvertent weather modification exists. This work examines the sensitivity to soil moisture and lower atmospheric water vapor content of a severe convective storm that struck Moore, Oklahoma, USA on May 20th, 2013, killing 24 people. While adjoint sensitivity analysis that employs the tangent linear version of a numerical weather prediction model might be used to examine convective sensitivities to soil moisture, the strong nonlinearity associated with these events likely renders this technique inaccurate. Alternatively, the approach here utilizes backward trajectory analysis to identify the regions up to a day prior to which the storm might be sensitive. Once the regions are identified, an ensemble of model forecasts is created by varying initial soil moisture to reveal the degree to which perturbations must be made to influence the downstream storm. Subsequent comparisons are made between the required soil moisture perturbations and realistic soil water values added through irrigation.

Ancell, Brian; Nauert, Christian

2014-05-01

42

The DYMECS project: The Dynamical and Microphysical Evolution of Convective Storms  

NASA Astrophysics Data System (ADS)

A new frontier in weather forecasting is emerging by operational forecast models now being run at convection-permitting resolutions at many national weather services. However, this is not a panacea; significant systematic errors remain in the character of convective clouds and rainfall distributions. The DYMECS project (Dynamical and Microphysical Evolution of Convective Storms) is taking a fundamentally new approach to evaluate and improve such models: rather than relying on a limited number of cases, which may not be representative, we have gathered a large database of 3D storm structures on 40 convective days using an automated storm-tracking and scan-scheduling algorithm for the high resolution Chilbolton radar in southern England. These structures have been related to storm life-cycles derived by tracking features in the rainfall from the UK radar network, and compared statistically to simulated reflectivity fields from multiple versions of the Met Office model, varying horizontal grid length between 1.5 km and 100 m, and changing the sub-grid mixing and microphysics schemes. We also evaluated the scale and intensity of convective updrafts using a new radar technique. We find that the horizontal size of simulated convective clouds and the updrafts within them decreases with decreasing grid lengths down to 200 m, below which no further decrease is found. Comparison with observations reveals that at these resolutions, updrafts are about the right size (around 2 km across), but the clouds are typically too narrow and rain too intense (in both cases by around a factor of two), while progressing through their lifecycle too slowly. The scale error may be remedied by artificially increasing mixing length, but the microphysics scheme has little effect on either scale or intensity.

Stein, Thorwald; Hogan, Robin; Hanley, Kirsty; Nicol, John; Plant, Robert; Lean, Humphrey; Clark, Peter; Halliwell, Carol

2014-05-01

43

Evolution of conserved variables related to storm cells during severe convection in a mesoscale model  

NASA Astrophysics Data System (ADS)

The WEX-MOP project aims at a next generation ensemble prediction system for the mesoscale. One goal of WEX-MOP is to quantify the role of conserved quantities during extreme convective weather. Conserved variables might offer new insight in the predictability of those events. An important conserved quantity is potential vorticity (PV), a fundamental property of the atmospheric flow on synoptic and planetary scales. However, investigations thereof on the atmospheric mesoscale are relatively new. PV has a close relation to rotation and balance, which is important in storm dynamics. Here we characterize the evolution of storm cells in terms of PV to provide new insights into storm dynamics. Tracking of storm cells has been frequently performed using radar and/or satellite data. It received less attention using model data. We present storm cell tracks for two cases of severe convection in June 2011 simulated using the non hydrostatic COSMO-DE weather model. The two cases have a very different background: on 5 June 2011 the convection was primarily locally forced by CAPE, while on 22 June there was strong forcing due to a cold front. For each of the two cases vertical velocity maxima are tracked. High intensity cells in both cases show a high correlation between PV and vertical velocity anomalies. This has been attributed to a strong environment storm relative helicity and/or CAPE close to the surface. For both cases there is a high variability in the cell characteristics. However, the PV anomalies on 22 June are larger than those on 5 June and have a higher correlation between vertical velocity and PV, consistent with the larger wind shear and helicity in the environment at this day. Study of further cases is necessary to test the hypothesis that a high helicity environment leads to more intense long lasting cells.

Weijenborg, Chris; Chagnon, Jeffrey; Friederichs, Petra; Gray, Suzanne; Hense, Andreas

2014-05-01

44

Convective Activities in the Tropical Western Pacific and Their Impact on the Northern Hemisphere Summer Circulation  

Microsoft Academic Search

Interannual and intraseasonal variations of convective activities in the tropical western Pacific during summer and their impact on the Northern Hemisphere circulation are investigated by using satellite cloud amount, sea surface temperature (SST) and geopotential data for 7 years (1978-1984). During summers when SST in the tropical western Pacific is about 1.0°C warmer than normal, active convection regions consisting of

Tsuyoshi Nitta

1987-01-01

45

What can simulated convective storms tell us about thunderstorm behavior under climate change?  

NASA Astrophysics Data System (ADS)

Isolated convective storms are responsible for numerous high-impact weather events. Their frequency and intensity under the present climate change has been the subject of much speculation, and this uncertainty is magnified when considering that these storms are sensitive to modest changes in their ambient environments. In this work we use an idealized, cloud-resolving model to study the role of environmental changes on storm behavior. This approach is useful since it allows direct comparison of storm morphology between one environment (e.g., the present) and another (e.g., the future). Our current understanding is that for much of the globe, atmospheric temperature and water vapor will increase, and, at least in the middle latitudes, tropospheric wind shear may decrease owing to a weakening of the zonal temperature gradient that maintains the polar jet stream. The vertically integrated effects of temperature and water vapor can be summarized by the convective available potential energy (CAPE), a measure of buoyant energy available to updrafts. These two parameters, CAPE and tropospheric wind shear, are known to exert significant control on storm behavior and are explored herein. Between simulations, either CAPE or shear or both are varied (by 200 J kg-1 and 2 m s-1, respectively), and storm properties in the various environments are then compared. In 112 experiment pairs with CAPE increased and shear decreased, 56% of storms produce stronger updrafts, with some that are stronger by as much as 20 m s-1. However, the magnitude and sign of the change is strongly dependent on the starting values of CAPE and shear. For example, in simulations where CAPE is already >2000 J kg-1 and shear is weak, such as the moist tropics, small changes to either parameter actually work to reduce updraft intensity, by 5 to 10 m/s. In environments where CAPE is very low (400 J kg-1), addition of just 200 J kg-1 of buoyancy can be the difference between storms that last 30-40 minutes, and storms that last over 2 hours and produce updrafts in excess of 30 m s-1. When considering storm rotation, only 44% of storms produce more vorticity near the ground when CAPE is increased and shear decreased. As with updraft speeds, these results are also highly sensitive to starting values. Additional analyses will be presented, including impacts on total rainfall, surface wind speeds, and hail production. These results underscore the need for further study of convective storm predictability as climate continues to change and highlight the importance of climate change as a regional phenomenon with implications that go beyond global temperatures. It is hoped that this work will foster discussion on such regional trends, what their outcomes might be, and the vital role of convective storms in earth's climate system.

Kirkpatrick, C.

2013-12-01

46

Sensitivity of the Amazon rainforest to convective storms  

NASA Astrophysics Data System (ADS)

The Amazon rainforest is the largest contiguous continental tropical forest in the world and is a world center of carbon storage, biodiversity, biogeochemical cycles and biogeophysical processes that affect the Earth climate system. Yet anthropogenic activities have produced changes in the forest-climate system. Consequently, an increase in rainfall in both the Western and Central Amazon and a decrease in the Eastern Amazon are expected due to these anthropogenic activities. While the projected decrease in rainfall has been discussed under the context of drought, deforestation, and fires, the effect of an increase in rainfall, and associated convective processes, on forest ecosystems has been overlooked. Across the Amazon rainforest, Western Amazonia has the highest precipitation rates, wood productivity, soil fertility, recruitment and mortality rates. Yet our field-measured tree mortality data from blowdowns that occurred in Western and Central Amazonia do not show a statistical difference in tree mortality between these regions. However, downburst velocities associated with these disturbances were calculated to be lower in Western Amazonia than in the Central Amazon. This suggests the Western Amazon is more highly sensitive to intense convective systems. This result is particularly relevant given the expected increase in rainfall in the Western and Central Amazon. The increase in rainfall is associated with more intense convective systems that in turn imply an increase in low level jet stream (LLJ) intensity east of the Andes. The presence of the LLJ is the main cause of squall lines and an increase in LLJ intensity will therefore cause increased propagation of squall lines into the Amazon basin. More frequent and active squall lines have the potential to increase the intensity and frequency of downbursts responsible for large forest blowdowns that will affect the biogeophysical feedbacks on the forest ecosystem and carbon budget.

Negron Juarez, R. I.; Chambers, J. Q.; Rifai, S. W.; Urquiza Munoz, J. D.; Tello, R.; Alegria Munoz, W.; Marra, D.; Ribeiro, G.; Higuchi, N.

2012-12-01

47

Saturn's Great Storm of 2010-2011: Cloud particles containing ammonia and water ices indicate a deep convective origin. (Invited)  

NASA Astrophysics Data System (ADS)

Saturn's Great Storm of 2010-2011 was first detected by amateur astronomers in early December 2010 and later found in Cassini Imaging Science Subsystem (ISS) images taken on 5 December, when it took the form of a 1000 km wide bright spot. Within a week the head of the storm grew by a factor of ten in width and within a few months created a wake that encircled the planet. This is the sixth Great Saturn Storm in recorded history, all having appeared in the northern hemisphere, and most near northern summer solstice at intervals of roughly 30 years (Sanchez-Lavega et al. 1991, Nature 353, 397-401). That the most recent storm appeared 10 years early proved fortunate because Cassini was still operating in orbit around Saturn and was able to provide unique observations from which we could learn much more about these rare and enormous events. Besides the dramatic dynamical effects displayed at the visible cloud level by high-resolution imaging observations (Sayanagi et al. 2013, Icarus 223, 460-478), dramatic thermal changes also occurred in the stratosphere above the storm (Fletcher et al. 2011, Science 332, 1413), and radio measurements of lightning (Fischer et al., 2011, Nature 475, 75-77) indicated strong convective activity at deeper levels. Numerical models of Saturn's Giant storms (Hueso and Sanchez-Lavega 2004, Icarus 172, 255-271) suggest that they are fueled by water vapor condensation beginning at the 10-12 bar level, some 250 km below the visible cloud tops. That idea is also supported by our detection of water ice near the cloud tops (Sromovsky et al. 2013, Icarus 226, 402-418). From Cassini VIMS spectral imaging taken in February 2011, we learned that the storm's cloud particles are strong absorbers of sunlight at wavelengths from 2.8 to 3.1 microns. Such absorption is not seen on Saturn outside of storm regions, implying a different kind of cloud formation process as well as different cloud composition inside the storm region. We found compelling evidence that the storm cloud contains a multi-component aerosol population. We needed at least three different materials to obtain good spectral fits. The most obvious contributor is ammonia ice, with water ice the best-defined secondary component. The most likely third component is ammonium hydrosulfide or some weakly absorbing material similar to what dominates visible clouds outside the storm region. Horizontally heterogeneous cloud models favor ammonium hydrosulfide as the third component, while horizontally uniform models favor the weak absorber. Both models rely on water ice absorption to compensate for residual spectral gradients produced by ammonia ice from 3.0 microns to 3.1 microns and need the relatively conservative third component to fill in the sharp ammonia ice absorption peak near 2.96 microns. The best heterogeneous model has spatial coverage fractions of 55% ammonia ice, 22% water ice, and 23% ammonium hydrosulfide. The best homogeneous model has an optically thin layer of weakly absorbing particles above an optically thick layer of water ice particles coated by ammonia ice. These Cassini data provide the first spectroscopic evidence of water ice in Saturn's atmosphere. This research was supported by NASA's Outer Planets Research Program under grant NNX11AM58G.

Sromovsky, L. A.; Baines, K. H.; Fry, P.

2013-12-01

48

The distribution of deep convection over ocean and land during the Asian summer monsoon  

NASA Technical Reports Server (NTRS)

The characteristics of the convection over the summer monsoon are investigated using the highly reflective cloud (HRC) data set (which is a subjective-analyzed daily index of organized deep convection, at one degree resolution, for years between 1971 and 1988 of the polar-orbiting satellite imagery). The results of the analysis are used to obtain the geographical distribution of HRCs for the climatological mean summer monsoon season and its four component months and to examine the intraseasonal variation of convection over selected areas. The model results of Webster and Chou (1980) are tested by comparing the relative frequency of occurrence of HRC for continental areas, coastal zones, and open ocean.

Grossman, Robert L.; Garcia, Oswaldo

1990-01-01

49

Infrasound observed in the Czech Republic during convective storms 9 - 10 July 2011  

NASA Astrophysics Data System (ADS)

An experimental array has been built at the observatory Panska Ves, Czech Republic (50°31' N 14°34' E). It is equipped with three differential microbarographs (type ISGM03). The sensors are arranged in an equilateral triangle; the distance between sensors is approximately 200 m. Using this array, we studied infrasound phenomena related with intense convective storms on 9-10 July 2011. In the studied frequency range 0.1-4 Hz, we observed phenomena of short duration related to lightning activity and also signals that persisted tens of seconds. The latter type of infrasound signals is the object of the current study. Azimuth of arrival of the signals corresponded well with position of convective storms towards the observatory and changed as convective storms were travelling across the Czech Republic from the south west to the north east. Apparent velocity often exceeded 340 m/s (considered as the local speed of sound); it means the signals arrived under some elevation angle (up to 40°). The azimuth of arrival showed higher variability at the beginning of the event; we repeatedly observed gradual variations in azimuth up to the change of 90°. The azimuth of arrival was more stable after 02 UT on 10 July 2011.

Sindelarova, Tereza; Skripnikova, Katerina; Chum, Jaroslav; Lastovicka, Jan; Base, Jiri; Mosna, Zbysek

2013-04-01

50

Revisiting the latent heat nudging scheme for the rainfall assimilation of a simulated convective storm  

NASA Astrophysics Data System (ADS)

Next-generation, operational, high-resolution numerical weather prediction models require economical assimilation schemes for radar data. In the present study we evaluate and characterise the latent heat nudging (LHN) rainfall assimilation scheme within a meso-? scale NWP model in the framework of identical twin simulations of an idealised supercell storm. Consideration is given to the model’s dynamical response to the forcing as well as to the sensitivity of the LHN scheme to uncertainty in the observations and the environment. The results indicate that the LHN scheme is well able to capture the dynamical structure and the right rainfall amount of the storm in a perfect environment. This holds true even in degraded environments but a number of important issues arise. In particular, changes in the low-level humidity field are found to affect mainly the precipitation amplitude during the assimilation with a fast adaptation of the storm to the system dynamics determined by the environment during the free forecast. A constant bias in the environmental wind field, on the other hand, has the potential to render a successful assimilation with the LHN scheme difficult, as the velocity of the forcing is not consistent with the system propagation speed determined by the wind. If the rainfall forcing moves too fast, the system propagation is supported and the assimilated storm and forecasts initialised therefrom develop properly. A too slow forcing, on the other hand, can decelerate the system and eventually disturb the system dynamics by decoupling the low-level moisture inflow from the main updrafts during the assimilation. This distortion is sustained in the free forecast. It has further been found that a sufficient temporal resolution of the rainfall input is crucial for the successful assimilation of a fast moving, coherent convective storm and that the LHN scheme, when applied to a convective storm, appears to necessitate a careful tuning.

Leuenberger, D.; Rossa, A.

2007-12-01

51

Midweek Increase in U.S. Summer Rain and Storm Heights, Suggests Air Pollution Invigorates Rainstorms  

NASA Technical Reports Server (NTRS)

Tropical Rainfall Measuring Mission (TRMM) satellite data show a significant midweek increase in summertime rainfall over the southeast U.S., due to afternoon intensification. TRMM radar data show a significant midweek increase in rain area and in the heights reached by afternoon storms. Weekly variations in model-reanalysis wind patterns over the region and in rain-gauge data are consistent with the satellite data. A midweek decrease of rainfall over the nearby Atlantic is also seen. EPA measurements of particulate concentrations show a midweek peak over much of the U.S. These observations are consistent with the theory that anthropogenic air pollution suppresses cloud-drop coalescence and early rainout during the growth of thunderstorms over land, allowing more water to be carried above the 0 C isotherm, where freezing yields additional latent heat, invigorating the storms--most dramatically evidenced by the shift in the midweek distribution of afternoon-storm heights--and producing large ice hydrometeors. The enhanced convection induces regional convergence, uplifting and an overall increase of rainfall. Compensating downward air motion suppresses convection over the adjacent ocean areas. Pre-TRMM-era data suggest that the weekly cycle only became strong enough to be detectable beginning in the 1980's. Rain-gauge data also suggest that a weekly cycle may have been detectable in the 1940's, but with peak rainfall on Sunday or Monday, possibly explained by the difference in composition of aerosol pollution at that time. This "weekend effect" may thus offer climate researchers an opportunity to study the regional climate-scale impact of aerosols on storm development and monsoon-like circulation.

Bell, Thomas L.; Rosenfeld, Daniel; Kim, Kyu-Myong; Yoo, Jung-Moon; Hahnenberger, Maura

2007-01-01

52

Deep Convective Clouds and Chemistry: A Field Experiment Planned for Summer 2009  

NASA Astrophysics Data System (ADS)

Convective transport is a major pathway of rapidly moving chemical constituents (including water) from the boundary layer to the upper troposphere (UT) and in some cases to the lower stratosphere (LS). Yet the global-scale impact of convective transport on the UTLS composition and chemistry has not been characterized. In addition, only a few studies have attempted to examine the detailed dynamics of deep convection and the concomitant redistribution, production, or removal of reactive constituents. The proposed Deep Convective Cloud and Chemistry (DC3) experiment will obtain measurements of enough chemical species to characterize the effects of convection on the transport and transformation of ozone and its precursors. For example, HOx species, its precursors, and NOx species in both inflow and outflow regions of deep convection will be measured along with microphysical properties, storm kinematics, and lightning discharges. These measurements are planned for over the Great Plains of the United States, where we hope to contrast regions of remote continental air to those more influenced by anthropogenic emissions. The primary goals of DC3 are 1) to quantify the impact of continental, midlatitude convective storm dynamics, multiphase chemistry, lightning, and cloud microphysics on the transport of chemical constituents to the upper troposphere, 2) to evaluate the anvil dynamics, microphysics, radiation, electrification, and multiphase chemistry that leads to the chemical composition observed in the convective outflow, 3) to determine the effects of convectively-perturbed air masses on ozone and its related chemistry in the midlatitude upper troposphere and lower stratosphere 12-48 hours after the near convection region is sampled, and 4) to contrast the influence of different boundary-layer chemical inputs on the composition of convective outflow. The strategy of reaching these goals as part of DC3 will be presented.

Barth, M. C.; Brune, W.; Cantrell, C.; Rutledge, S.

2006-12-01

53

The Impacts of Microphysics and Planetary Boundary Layer Physics on Model Simulations of U. S. Deep South Summer Convection  

NASA Technical Reports Server (NTRS)

Inspection of output from various configurations of high-resolution, explicit convection forecast models such as the Weather Research and Forecasting (WRF) model indicates significant sensitivity to the choices of model physics parameterizations employed. Some of the largest apparent sensitivities are related to the specifications of the cloud microphysics and planetary boundary layer physics packages. In addition, these sensitivities appear to be especially pronounced for the weakly-sheared, multicell modes of deep convection characteristic of the Deep South of the United States during the boreal summer. Possible ocean-land sensitivities also argue for further examination of the impacts of using unique ocean-land surface initialization datasets provided by the NASA Short-term Prediction Research and Transition (SPoRT Center to select NOAA/NWS weather forecast offices. To obtain better quantitative understanding of these sensitivities and also to determine the utility of the ocean-land initialization data, we have executed matrices of regional WRF forecasts for selected convective events near Mobile, AL (MOB), and Houston, TX (HGX). The matrices consist of identically initialized WRF 24-h forecasts using any of eight microphysics choices and any of three planetary boundary layer choices. The resulting 24 simulations performed for each event within either the MOB or HGX regions are then compared to identify the sensitivities of various convective storm metrics to the physics choices. Particular emphasis is placed on sensitivities of precipitation timing, intensity, and coverage, as well as amount and coverage of lightning activity diagnosed from storm kinematics and graupel in the mixed phase layer. The results confirm impressions gleaned from study of the behavior of variously configured WRF runs contained in the ensembles produced each spring at the Center for the Analysis and Prediction of Storms, but with the benefit of more straightforward control of the physics package choices. The design of the experiments thus allows for more direct interpretation of the sensitivities to each possible physics combination. The results should assist forecasters in their efforts to anticipate and correct for possible biases in simulated WRF convection patterns, and help the modeling community refine their model parameterizations.

McCaul, E. W., Jr.; Case, J. L.; Zavodsky, B. T.; Srikishen, J.; Medlin, J. M.; Wood, L.

2014-01-01

54

Initialization of a modeled convective storm using Doppler radar-derived fields  

SciTech Connect

A method is developed to initialize convective storm simulations with Doppler radar-derived fields. Input fields for initialization include velocity, rain water derived from radar reflectivity, and pressure and temperature fields obtained through thermodynamic retrieval. A procedure has been developed to fill in missing wind data, followed by a variational adjustment to the filled wind field to minimize [open quotes]shocks[close quotes] that would otherwise cause the simulated fields to deteriorate rapidly. A series of experiments using data from a simulated storm establishes the feasibility of the initialization method. Multiple Doppler radar observations from the 20 May 1977 Del City tornadic storm are used for the initialization experiments. Simulation results initialized from observations taken at two different stages of storm development are shown and compared to observations taken at later times. A simulation initialized from one of the observation times showed good agreement with subsequent observations, though the simulated storm appeared to be evolving much faster than observed. Possible mechanisms for error growth are discussed.

Lin, Y.

1992-01-01

55

European climatology of severe convective storm environmental parameters: A test for significant tornado events  

NASA Astrophysics Data System (ADS)

A climatology of various parameters associated with severe convective storms has been constructed for Europe. This involves using the reanalysis data base from ERA-40 for the period 1971-2000 and calculating monthly means, variability range and extremes occurrence of fields such as convective available potential energy, convective inhibition energy, mid-tropospheric lapse rate, low-tropospheric moisture content and storm relative helicity for different layers. This process is a first step towards development of a synthetic climatology of European severe weather, and is publicly available at the web site http://ecss.uib.es. Preliminary results derived from these products were presented during the ECSS 2004 conference. This paper is devoted to a more detailed presentation and discussion of the main results. It is hypothesized that preferred areas for severe thunderstorms occurrence in Europe would extend along a zonal belt over the south-central regions, where high helicity associated with the extratropical storm tracks and thermodynamically-favourable profiles established over the southern Atlantic and Mediterranean Sea would most likely be concatenated. Further, this effort has been complemented with a collection of existing reports of significant (at least F2) tornadoes in Europe during the period 1971-2003. We present this data set in this paper and it also can be found at the website http://ecss.uib.es. Thus, the tornado collection can be used to test the appropriateness of the parameters selected for the synthetic climatology. In particular, it is found that the convective available potential energy, low-tropospheric moisture content and environmental shear, when related to the monthly climatology, are reasonably good descriptors of the tornadic environments.

Romero, Romualdo; Gayà, Miquel; Doswell, Charles A.

2007-02-01

56

Ionospheric convection during the magnetic storm of 20-21 March 1991  

NASA Technical Reports Server (NTRS)

We report on the response of high-latitude ionospheric convection during the magnetic storm of March 20-21 1990. IMP-8 measurements of solar wind plasma and interplanetary magnetic field (IMF), ionospheric convection flow measurements from the Wick and Goose Bay coherent radars, EISCAT, Millstone Hill and Sondrestorm incoherent radars and three digisondes at Millstone Hill, Goose Bay and Qaanaaq are presented. Two intervals of particular interest have been indentified. The first starts with a storm sudden commencement at 2243 UT on March 20 and includes the ionospheric activity in the following 7 h. The response time of the ionospheric convection to the southward tuning of the IMF in the dusk to midnight local times is found to be approximately half that measured in a similar study at comparable local times during more normal solar wind conditions. A subsequent reconfiguration of the nightside convection pattern was also observed, although it was not possible to distinguish between effects due to possible changes in B(sub y) and effects due to substorm activity. The second interval, 1200-2100 UT 21 March 1990, included a southward turning of the IMF which resulted in the B(sub z) component becoming -10 nT. The response time on the dayside to this change in the IMF at the magnetopause was approximately 15 min to 30 min which is a factor of approximately 2 greater than those previously measured at higher latitudes. A movement of the nightside flow reversal, possibly driven by current systems associated with the substorm expansion phases, was observed, implying that the nightside convection pattern can be dominated by substorm activity.

Taylor, J. R.; Yeoman, T. K.; Lester, M.; Buonsanto, M. J.; Scali, J. L.; Ruohoniemi, J. M.; Kelly, J. D.

1994-01-01

57

CONVECTIVE BURSTS AND THE COUPLING OF SATURN'S EQUATORIAL STORMS AND INTERIOR ROTATION  

SciTech Connect

Temporal variations of Saturn's equatorial jet and magnetic field hint at rich dynamics coupling the atmosphere and the deep interior. However, it has been assumed that rotation of the interior dynamo must be steady over tens of years of modern observations. Here we use a numerical convection model and scaling estimates to show how equatorial convective bursts can transfer angular momentum to the deeper interior. The numerical model allows angular momentum transfer between a fluid outer spherical shell and a rigid inner sphere. Convection drives a prograde equatorial jet exhibiting quasiperiodic bursts that fill the equatorial volume outside the tangent cylinder. For each burst strong changes in the equatorial surface velocity are associated with retrograde torque on the inner sphere. Our results suggest that Saturn's Great White Spot, a giant storm that was observed to fill the equatorial region in 1990, could mobilize a volume of fluid carrying roughly 15% of Saturn's moment of inertia. Conservation of angular momentum then implies that a 20% change in the equatorial jet angular velocity could change the average interior rotation rate by about 0.1%-roughly an order of magnitude less than the apparent rotation rate changes associated with Saturn's kilometric radio (SKR) signal. However, if the SKR signal originates outside the liquid metal core in a 'planetary tachocline' that separates the layer of fast zonal flow from the magnetically controlled and slowly convecting deep interior, then convective bursts can provide a possible mechanism for the observed {approx}1% SKR changes.

Heimpel, Moritz [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1 (Canada); Aurnou, Jonathan M., E-mail: mheimpel@ualberta.ca, E-mail: aurnou@ucla.edu [Department of Earth and Space Sciences, University of California, Los Angeles, CA (United States)

2012-02-10

58

Ionospsheric observation of enhanced convection-initiated gravity waves during tornadic storms  

NASA Technical Reports Server (NTRS)

Atmospheric gravity waves associated with tornadoes, with locally severe storms occuring with tornadoes, and with hurricanes were studied through the coupling between the ionosphere and the troposphere. Reverse group ray tracing computations of gravity waves observed by an ionospheric Doppler sounder array were analyzed. The results of ray tracing computations and comparisons between the computed location of the wave sources and with conventional meteorological data indicate that the computed sources of the waves were near the touchdown of the tornadoes, near the eye of the hurricanes, and directly on the squall line of the severe thunderstorms. The signals excited occurred one hour in advance of the tornadoes and three hours in advance of the hurricanes. Satellite photographs show convective overshooting turrets occurring at the same locations and times the gravity waves were being excited. It is suggested that gravity wave observations, conventional meteorological data, and satellite photographs be combined to develop a remote sensing technique for detecting severe storms.

Hung, R. J.

1981-01-01

59

Influence of the Convection Electric Field Models on Predicted Plasmapause Positions During Magnetic Storms  

NASA Technical Reports Server (NTRS)

In the present work, we determine how three well documented models of the magnetospheric electric field, and two different mechanisms proposed for the formation of the plasmapause influence the radial distance, the shape and the evolution of the plasmapause during the geomagnetic storms of 28 October 2001 and of 17 April 2002. The convection electric field models considered are: Mcllwain's E51) electric field model, Volland-Stern's model and Weimer's statistical model compiled from low-Earth orbit satellite data. The mechanisms for the formation of the plasmapause to be tested are: (i) the MHD theory where the plasmapause should correspond to the last-closed- equipotential (LCE) or last-closed-streamline (LCS), if the E-field distribution is stationary or time-dependent respectively; (ii) the interchange mechanism where the plasmapause corresponds to streamlines tangent to a Zero-Parallel-Force surface where the field-aligned plasma distribution becomes convectively unstable during enhancements of the E-field intensity in the nightside local time sector. The results of the different time dependent simulations are compared with concomitant EUV observations when available. The plasmatails or plumes observed after both selected geomagnetic storms are predicted in all simulations and for all E-field models. However, their shapes are quite different depending on the E-field models and the mechanisms that are used. Despite the partial success of the simulations to reproduce plumes during magnetic storms and substorms, there remains a long way to go before the detailed structures observed in the EUV observations during periods of geomagnetic activity can be accounted for very precisely by the existing E-field models. Furthermore, it cannot be excluded that the mechanisms currently identified to explain the formation of "Carpenter's knee" during substorm events, will', have to be revised or complemented in the cases of geomagnetic storms.

Pierrard, V.; Khazanov, G.; Cabrera, J.; Lemaire, J.

2007-01-01

60

Gravity shear waves atop the cirrus layer of intense convective storms  

NASA Technical Reports Server (NTRS)

Recent visual satellite photographs of certain intense convective storms have revealed concentric wave patterns. A model for the generation and growth of these waves is proposed. The proposed initial generating mechanism is similar to the effect noticed when a pebble is dropped into a calm pond. The penetration of the tropopause by overshooting convection is analogous to the pebble's penetration of the water's surface. The model for wave growth involves instability due to the wind shear resulting from the cirrus outflow. This model is based on an equation for the waves' phase speed which is similar to the Helmholtz equation. It, however, does not assume an incompressible atmosphere, but rather assumes density is a logarithmic function of height. Finally, the model is evaluated on the two mid-latitude and three tropical cases. The data indicate that shearing instability may be a significant factor in the appearance of these waves.

Stobie, J. G.

1975-01-01

61

Intense Convective Storms with Little or No Lightning over Central Arizona: A Case of Inadvertent Weather Modification?.  

NASA Astrophysics Data System (ADS)

On 20/21 August 1993, deep convective storms occurred across much of Arizona, except for the southwestern quarter of the state. Several storms were quite severe, producing downbursts and extensive wind damage in the greater Phoenix area during the late afternoon and evening. The most severe convective storms occurred from 0000 to 0230 UTC 21 August and were noteworthy in that, except for the first reported severe thunderstorm, there was almost no cloud-to-ground (CG) lightning observed during their life cycles. Other intense storms on this day, particularly early storms to the south of Phoenix and those occurring over mountainous terrain to the north and east of Phoenix, were prolific producers of CG lightning. Radar data for an 8-h period (2000 UTC 20 August-0400 UTC 21 August) indicated that 88 convective cells having maximum reflectivities greater than 55 dBZ and persisting longer than 25 min occurred within a 200-km range of Phoenix. Of these cells, 30 were identified as `low-lightning' storms, that is, cells having three or fewer detected CG strikes during their entire radar-detected life cycle. The region within which the low-lightning storms were occurring spread to the north and east during the analysis period.Examination of the reflectivity structure of the storms using operational Doppler radar data from Phoenix, and of the supportive environment using upper-air sounding data taken at Luke Air Force Base just northwest of Phoenix, revealed no apparent physical reasons for the distinct difference in observed cloud-to-ground lightning character between the storms in and to the west of the immediate Phoenix area versus those to the north, east, and south. However, the radar data do reveal that several extensive clouds of chaff initiated over flight-restricted military ranges to the southwest of Phoenix. The prevailing flow advected the chaff clouds to the north and east. Convective storms that occurred in the area likely affected by the dispersing chaff clouds were characterized by little or no CG lightning.Field studies in the 1970s demonstrated that chaff injected into building thunderstorms markedly decreased CG lightning strikes. There are no data available regarding either the in-cloud lightning character of storms on this day or the technical specifications of the chaff being used in military aircraft anti-electronic warfare systems. However, it is hypothesized that this case of severe, but low-lightning, convective storms resulted from inadvertent lightning suppression over south-central Arizona due to an extended period of numerous chaff releases over the military ranges.

Maddox, Robert A.; Howard, Kenneth W.; Dempsey, Charles L.

1997-04-01

62

Effects of a Large Convective Storm on the Atmospheric Dynamics of a Jovian Planet  

NASA Astrophysics Data System (ADS)

Voyager observations showed that Saturn's equatorial jet blew eastward at 450 m/s in 1980-81. However, subsequent Earth observations between 1996-2002 showed the equatorial jet speed to be approximately 350 m/s (Sanchez-Lavega et al., 2003). Sanchez-Lavega et al. interpreted this difference to be a true slowdown, but uncertainties in cloud altitudes combined with Cassini CIRS observations of vertical wind shear raise questions about whether the difference represents a real slowdown or simply changes in the altitudes of the observed clouds. A major event that could have influenced the winds occurred in 1990, when a huge convective storm, called a Great White Spot (GWS), erupted in the equatorial region of Saturn (Sanchez-Lavega, 1994). Here, we test the hypothesis that a GWS-like convective event can cause a slowdown of Saturn's equatorial jet like that observed. Mechanisms for slowing the winds include (1) potential vorticity mixing caused by such a storm, which would transport eastward momentum to higher latitudes, (2) momentum transport away from the jet by storm-induced atmospheric waves and (3) direct vertical mixing with a hypothetical source of deep, slow-moving air. We present order-of-magnitude estimates and fully nonlinear numerical simulations of the atmospheric flow using the EPIC atmosphere model. We envision that GWS-like convective events transport moist air from the deep troposphere to the neutrally buoyant level near the tropopause. Accordingly, we added localized mass-pulses to the equatorial upper troposphere to represent the effects of a GWS in the EPIC model. Our estimates and preliminary simulations suggest that GWS-like events can only cause wind-speed variations exceeding 50 m/s when the storm mass is unrealistically large. To elucidate the dynamical mechanisms involved, we performed a range of simulations which showed that the background wind profiles and other parameters strongly influence the dynamical response to a GWS. We will summarize these simulations in our presentation. This study is supported by NSF grant AST-0206269.

Sayanagi, K. M.; Showman, A. P.; Kursinski, E. R.

2004-11-01

63

Evaluation and development of satellite inferences of convective storm intensity using combined case study and thunderstorm model simulations  

NASA Technical Reports Server (NTRS)

Observational requirements for predicting convective storm development and intensity as suggested by recent numerical experiments are examined. Recent 3D numerical experiments are interpreted with regard to the relationship between overshooting tops and surface wind gusts. The development of software for emulating satellite inferred cloud properties using 3D cloud model predicted data and the simulation of Heymsfield (1981) Northern Illinois storm are described as well as the development of a conceptual/semi-quantitative model of eastward propagating, mesoscale convective complexes forming to the lee of the Rocky Mountains.

Cotton, W. R.; Tripoli, G. J.

1982-01-01

64

Sprite-producing Convective Storms within the Colorado Lightning Mapping Array  

NASA Astrophysics Data System (ADS)

The multi-year, multi-institution effort entitled Physical Origins of Coupling to the Upper Atmosphere from Lightning (PhOCAL), has among its goals to qualitatively understand the meteorology and lightning flash characteristics that produce the unusual and/or very energetic lightning responsible for phenomena such as sprites, halos, elves, blue jets and gigantic jets, collectively known as Transient Luminous Events (TLEs). A key task is to obtain simultaneous video, ideally with a high-speed imager (HSI), of both a TLE and its parent lightning discharge, within the domain of a 3-D Lightning Mapping Array (LMA). While conceptually simple, this task is logistically quite complicated. In 2012, a new 15-station Colorado LMA (COLMA) became operational, covering northeastern Colorado, with the Yucca Ridge Field Station (YRFS) near its western edge. The National Charge Moment Change Network (CMCN), which since 2007 has been documenting sprite-class +CGs (those with impulse change moment changes >100 C km), indicates that a strong gradient of energetic +CGs exists west-to-east through the COLMA, with the most likely region for sprite-producing storms being in the COLMA eastern fringes (western Kansas and Nebraska). Yet, on 8 and 25 June, 2012, intense convective systems formed in the COLMA along and just east of the Front Range, producing severe weather and intense lightning. On the 8th, four sprite parent +CGs were captured at 3000 fps from YRFS with the sprites confirmed by dual (conventional speed) cameras in New Mexico. In a second storm on the 25th, viewing conditions prevented +CG video acquisition, but sprites were logged over the COLMA and detailed reconstructions of the discharges are being made. The parent discharges often began as upward negative leaders propagating into a mid-level positive charge layer at 8-10 km. They often originated within or near the convective core before expanding outward into a stratiform region and involving several hundred square kilometers, to be followed by +CG and strong continuing currents. LMA indications of recoil leaders appear confirmed by some high-speed video. These storms were somewhat smaller than the typical sprite-bearing MCS. The storm structures will be categorized using GOES IR, NEXRAD reflectivity, NLDN lightning data, CMCN impulse charge moment data, and full charge moment charge retrievals. The sprite parent CG discharges will be cataloged along with their points of origin, the height and volume from which charge is removed, the charge lowered to ground, and the continuing current characteristics. These CGs will be placed in the context of the storms' meteorological structure and evolution.

Lyons, W. A.; Cummer, S. A.; Rison, W.; Krehbiel, P. R.; Lang, T. J.; Rutledge, S. A.; Lu, G.; Stanley, M. A.; Ashcraft, T.; Nelson, T. E.

2012-12-01

65

Winter storm- and summer thunderstorm-related loss events with regard to climate change in Germany  

NASA Astrophysics Data System (ADS)

The development of winter storm- and summer thunderstorm-related loss events within the next decades in Germany was investigated with regard to change in frequency and intensity caused by climate changes. As a first step, observed meteorological data were connected with insurance data on a statistical basis. A regional climate model was then used to estimate future climate development. Using the statistical relations between meteorological and insurance data, the development of climate-driven damages was calculated. Results show that an increase of loss events can be expected within the next decades. These results show loss ratios shifting from higher return periods to smaller ones. In progressive decades, all these loss events become regionally more differentiated.

Gerstengarbe, Friedrich-Wilhelm; Werner, Peter C.; Österle, Hermann; Burghoff, Olaf

2013-11-01

66

Assessment of the European Severe Convective Storm Climatology using Reanalysis Data  

NASA Astrophysics Data System (ADS)

Thunderstorms and their accompanying phenomena like large hail, severe wind gusts, tornadoes and excessive precipitation are increasingly recognized as an important hazard to life and property in Europe. Within the project STEPCLIM ("Severe Thunderstorm Evaluation and Predictability in Climate Models"), we link historic severe thunderstorm events in Europe to atmospheric conditions resolved by reanalysis data. The aim is to find a relation between quantities, which can be represented by relatively coarse climate models, and the occurrence of short-lived and local severe weather phenomena associated with convection. At a later stage, this relation will be applied to climate forecast data, so that the effects of climate change on the frequency and intensity of severe convective storms can be investigated. A set of parameters is defined for the characterization of the local state of the atmosphere at any given point in place and time. These parameters represent the "ingredients" for severe thunderstorms, namely instability, vertical wind shear, and a measure of support for convective initiation. They are calculated from 6-hourly ERA-Interim reanalysis fields (1979-2011). The such derived fields are compared with the occurrence or non-occurrence of severe weather phenomena according to the quality-controlled severe storm reports collected in the European Severe Weather Database (ESWD). A logistic regression is then fitted in order to find the best relation between a given combination of parameters and the associated severe weather probability. This relation is postulated to be invariant against any changes in climate, an assumption that is justified by the physics-based nature of the chosen parameters. With this restriction, the derived relation can be used to estimate future severe weather frequencies based on modeled climatic changes of the underlying parameter distributions. In this presentation, emphasis is put on the used methodology and on a way to deal with spatial and temporal inhomogeneities of the observational data.

Pistotnik, Georg; Groenemeijer, Pieter; Kühne, Thilo

2013-04-01

67

Diurnal evolution and distribution of warm-season convective storms in different prevailing wind regimes over contiguous North China  

NASA Astrophysics Data System (ADS)

diurnal evolution and distribution of warm-season convective storms in different prevailing wind regimes at the 925 hPa and 500 hPa levels over contiguous North China have been studied using a climatology based on radar reflectivity mosaics, soundings, and reanalysis data from 15 May to 15 September, in 2008-2011. In the wind regimes at the 925 hPa level, the frequency of occurrence of convection is highest for south-southwesterly flows, followed by that for south-southeasterly flows. The low-level southerly warm and moist flow over the foothills and plains favors initiation and intensification of convection resulting from topographic forcing. Among the wind regimes at the 500 hPa level, the frequency of occurrence of convection shows a pronounced maximum for west-southwesterly flows, and most of these storms initiate and develop over the foothills and plains. Convection in the wind regime shows the morphology and slowly east-southeastward moving characteristics of well-organized, longer-lived systems, with environmental conditions conducive to vertical wind shear and instability. At the 500 hPa level, the high frequency of occurrence of convection for west-southwesterly flows is followed by that for west-northwesterly flows. Under west-northwesterly flows, convective storms initiated over mountains located to the northwest in the early afternoon move rapidly to the plains in the southeast of the study region. These storms show the primary formation characteristics of shorter-lived convection and intensify noticeably as they move from the mountains to the foothills and plains.

Chen, Mingxuan; Wang, Yingchun; Gao, Feng; Xiao, Xian

2014-03-01

68

The Evolution of Convective Storms from Their Footprints on the Sea as Viewed by Synthetic Aperture Radar from Space  

Microsoft Academic Search

SEASAT synthetic aperture radar (SAR) echoes from the sea have previously been shown to be the result of rain and winds produced by convective storms; rain damps the surface waves and causes echo-free holes, while the diverging winds associated with the downdraft generate waves and associated echoes surrounding the holes. Gust fronts are also evident. Such a snapshot from 8

David Atlas; Peter G. Black

1994-01-01

69

Using a WRF simulation to examine regions where convection impacts the Asian summer monsoon anticyclone  

NASA Astrophysics Data System (ADS)

The Asian summer monsoon is a prominent feature of the global circulation that is associated with an upper-level anticyclone (ULAC) that stands out vividly in satellite observations of trace gases. The ULAC also is an important region of troposphere-to-stratosphere transport. We ran the Weather Research and Forecasting (WRF) model at convective-permitting scales (4 km grid spacing) between 10-20 August 2012 to understand the role of convection in transporting boundary layer air into the upper-level anticyclone. Such high-resolution modeling of the Asian ULAC previously has not been documented in the literature. Comparison of our WRF simulation with reanalysis and satellite observations showed that WRF simulated the atmosphere sufficiently well to be used to study convective transport into the ULAC. A back-trajectory analysis based on hourly WRF output showed that >90% of convectively influenced parcels reaching the ULAC came from the Tibetan Plateau (TP) and the southern slope (SS) of the Himalayas. A distinct diurnal cycle is seen in the convective trajectories, with their greatest impact occurring between 1600-2300 local solar time. This finding highlights the role of 'everyday' diurnal convection in transporting boundary layer air into the ULAC. WRF output at 15 min intervals was produced for 16 August to examine the convection in greater detail. This high-temporal output revealed that the weakest convection in the study area occurred over the TP. However, because the TP is at 3000-5000 m MSL, its convection does not have to be as strong to reach the ULAC as in lower altitude regions. In addition, because the TP's elevated heat source is a major cause of the ULAC, we propose that convection over the TP and the neighboring SS is ideally geographically situated to impact the ULAC. The vertical mass flux of water vapor into the ULAC also was calculated. Results show that the TP and SS regions dominate other Asian regions in vertically transporting moisture into the ULAC. Because convection reaching the ULAC is more widespread over the TP than nearby, we propose that the abundant convection partially explains the TP's dominant water vapor fluxes. In addition, greater outgoing longwave radiation reaches the upper levels of the TP due to its elevated terrain. This creates a warmer ambient upper level environment, allowing parcels with greater saturation mixing ratios to enter the ULAC. Lakes in the Tibetan Plateau are shown to provide favorable conditions for deep convection during the night.

Heath, N.; Fuelberg, H. E.

2013-12-01

70

Dynamics of the AMPERE Region 1 Birkeland current oval during storms, substorms and steady magnetospheric convection  

NASA Astrophysics Data System (ADS)

Using radial current densities provided by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) we employ a fitting scheme to identify the location of the maximum Region 1 field-aligned (Birkeland) current at all magnetic local times. We call this parameter the "R1 oval" and we investigate its behavior during various modes of magnetospheric activity such as storms, substorms and steady magnetospheric convection (SMCs). Results show the following: (1) during substorms the radius of the R1 oval undergoes a cyclic inflation and contraction which matches the standard paradigm for substorm growth (loading) and expansion (unloading); (2) during SMCs the R1 oval is relatively steady consistent with balanced dayside and nightside reconnection during these events; and (3) during magnetic storms the size of the R1 oval is strongly correlated with the strength of the ring current specified by the Sym-H index. We also examine the behavior of the R1 oval in the northern and southern hemispheres simultaneously as a function of season in an effort to understand the role that internal magnetosphere-ionosphere coupling influences may play in modulating the response of the magnetosphere during these various types of events.

Baker, J. B.; Clausen, L.; Ruohoniemi, J. M.; Milan, S. E.; Kissinger, J.; Anderson, B. J.; Wing, S.

2012-12-01

71

Sensitivity analysis of numerically-simulated convective storms using direct and adjoint methods  

SciTech Connect

The goal of this project is to evaluate the sensitivity of numerically modeled convective storms to control parameters such as the initial conditions, boundary conditions, environment, and various physical and computational parameters. In other words, the authors seek the gradient of the solution vector with respect to specified parameters. One can use two approaches to accomplish this task. In the first or so-called brute force method, one uses a fully nonlinear model to generate a control forecast starting from a specified initial state. Then, a number of other forecasts are made in which chosen parameters (e.g., initial conditions) are systematically varied. The obvious drawback is that a large number of full model predictions are needed to examine the effects of only a single parameter. The authors describe herein an alternative, essentially automated method (ADIFOR, or Automatic DIfferentiation of FORtran) for obtaining the solution gradient that bypasses the adjoint altogether yet provides even more information about the gradient. (ADIFOR, like the adjoint technique, is constrained by the linearity assumption.) Applied to a 1-D moist cloud model, the authors assess the utility of ADIFOR relative to the brute force approach and evaluate the validity of the tangent linear approximation in the context of deep convection.

Park, S.K.; Droegemeier, K.K. [Univ. of Oklahoma, Norman, OK (United States); Bischof, C.; Knauff, T. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.

1994-06-01

72

Diagnosis of the secondary circulation of tropical storm Bilis (2006) and the effects of convective systems on its track  

NASA Astrophysics Data System (ADS)

We diagnose characteristics of the quasi-balanced flow and secondary circulation (SC) of tropical storm Bilis (2006) using the potential vorticity (PV)- ? inversion method. We further analyze how secondary steering flows associated with mesoscale convective systems affected the track of tropical storm Bilis after it made landfall. The quasi-balanced asymmetric and axisymmetric circulation structures of tropical storm Bilis are represented well by the PV- ? inversion. The magnitude of the nonlinear quasi-balanced vertical velocity is approximately 75% of the magnitude simulated using the Weather Research and Forecasting (WRF) model. The SC of Bilis (2006) contained two strong regions of ascending motion, both of which were located in the southwest quadrant of the storm. The first (150-200 km southwest of the storm center) corresponded to the eyewall region, while the second (approximately 400 km southwest of the storm center) corresponded to latent heat release associated with strong precipitation in major spiral rainbands. The SC was very weak in the northeast quadrant (the upshear direction). Dynamical processes related to the environmental vertical wind shear produced an SC that partially offset the destructive effects of the environmental vertical wind shear (by 20%-25%). This SC consisted of upward motion in the southwest quadrant and subsidence in the northeast quadrant, with airflow oriented from southwest to northeast at high altitudes and from northeast to southwest at lower levels. The inverted secondary zonal and meridional steering flows associated with continuous asymmetric mesoscale convective systems were about -2.14 and -0.7 m s-1, respectively. These steering flows contributed substantially to the zonal (66.15%) and meridional (33.98%) motion of the storm at 0000 UTC 15 July 2006. The secondary steering flow had a significant influence on changing the track of Bilis from southward to northward. The direction of the large-scale meridional steering flow (3.02 m s-1) was opposite to the actual meridional motion (-2.06 m s-1).

Yu, Jinhua; Fu, Hao; Tang, Sheng; Sheng, Siwei

2014-02-01

73

Evaluate the urban effect on summer convective precipitation by coupling a urban canopy model with a Regional Climate Model  

NASA Astrophysics Data System (ADS)

One of the most significant urbanization in the world occurred in Great Beijing Area of China during the past several decades. The land use and land cover changes modifies the land surface physical characteristics, including the anthropogenic heat and thermo-dynamic conduction. All of those play important roles in the urban regional climate changes. We developed a single layer urban canopy module based on the Community Land Surface Model Urban Module (CLMU). We have made further improvements in the urban module: the energy balances on the five surface conditions are considered separately: building roof, sun side and shade side wall, pervious and impervious land surface. Over each surface, a method to calculate sky view factor (SVF) is developed based on the physically process while most urban models simply provide an empirical value; A new scheme for calculating the latent heat flux is applied on both wall and impervious land; anthropogenic heat is considered in terms of industrial production, domestic wastes, vehicle and air condition. All of these developments improve the accuracy of surface energy balance processing in urban area. The urban effect on summer convective precipitation under the unstable atmospheric condition in the Great Beijing Area was investigated by simulating a heavy rainfall event in July 21st 2012. In this storm, strong meso-scale convective complexes (MCC) brought precipitation of averagely 164 mm within 6 hours, which is the record of past 60 years in the region. Numerical simulating experiment was set up by coupling MCLMU with WRF. Several condition/blank control cases were also set up. The horizontal resolution in all simulations was 2 km. While all of the control results drastically underestimate the urban precipitation, the result of WRF-MCLMU is much closer to the observation though still underestimated. More sensitive experiments gave a preliminary conclusion of how the urban canopy physics processing affects the local precipitation: the existence of large area of impervious surfaces restrain the surface evaporation and latent heat flux in urban while the anthropogenic heat and enhanced sensible heat flux warm up the lower atmospheric layer and strengthen the vertical stratification instability; In this storm event, the water supply of the MCC was thought to be sufficient, thus the instability of the vertical stratification was the key factor for precipitation.

Liu, Z.; Liu, S.; Xue, Y.; Oleson, K. W.

2013-12-01

74

Automatic differentiation as a tool for sensitivity analysis of a convective storm in a 3-D cloud model  

SciTech Connect

The ADIFOR automatic differentiation tool is applied to a 3-D storm-scale meteorological model to generate a sensitivity-enhanced code capable of providing derivatives of all model output variables and related diagnostic (derived) parameters as a function of specified control parameters. The tangent linear approximation, applied to a deep convective storm by the first of its kind using a full-physics compressible model, is valid up to 50 min for a 1% water vapor perturbations. The result is very encouraging considering the highly nonlinear and discontinuous properties of solutions. The ADIFOR-generated code has provided valuable sensitivity information on storm dynamics. Especially, it is very efficient and useful for investigating how a perturbation inserted at earlier time propagates through the model variables at later times. However, it is computationally very expensive to be applied to the variational data assimilation, especially for 3-D meteorological models, which potentially have a large number of input variables.

Park, S.K.; Droegemeier, K.K. [Univ. of Oklahoma, Norman, OK (United States); Bischof, C.H. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.

1996-10-01

75

Van Allen Probes based investigation of storm time plasmasphere erosion and earthward penetration of the convection electric field  

NASA Astrophysics Data System (ADS)

Using the Van Allen Probes we investigate the erosion of the plasmasphere as well as the evolution in location of the plasmapause during large storms (Dst < -100 nT). In addition, we also examine the penetration of the large scale storm-time convection electric field to low L ( < 3 RE) and its role in erosion of the plasmasphere. The enhanced convection electric field penetrates to low L during large storms, and a tangible effect on plasmasphere erosion is observed at low L. The plasmaspause is identified through the UHR line in EMFISIS high frequency spectral data and plasma densities determined from calibration fits to the spacecraft potential from the EFW instrument; such fits are also presented herein. During large storms the plasmapause can move to within L~1.9 RE of the earth. The erosion of the plasmasphere and consequent inward movement of the plasmapause to low L from quite time locations (4-5 RE) occurs within less than one orbit period (~9hr).

Thaller, S. A.; Wygant, J. R.; Dai, L.; Breneman, A. W.; Kersten, K.; Kletzing, C.; Kurth, W. S.; Bonnell, J. W.; De Pascuale, S.; Hospodarsky, G. B.; Bounds, S. R.

2013-12-01

76

Influence of storm characteristics on sulfate in precipitation  

SciTech Connect

The effects of storm dynamics on precipitation chemistry were examined using an atmospheric budget for SO/sub 4//sup =/. One hundred storms occurring between 1975 and 1978 at Hubbard Brook Experimental Forest in New Hampshire were used as test data. Concentrations of major ions were usually greater in convective storms than in continuouus or layer storms. For example the geometric mean concentrations of SO/sub 4//sup =/ in convective and continous storms were 4.1 and 1.1 mg L/sup -1/, respectively. Higher SO/sub 4//sup =/ concentrations also occurred when surface wind direction were south or southwest. The summer maximum in convective activity along with the seasonal dependence of surface wind directions and the seasonal atmospheric chemistry cycle can account for the summer maximum in SO/sub 4//sup =/ concentrations observed in the northeastern United States. 22 references, 5 figures, 4 tables.

Bloxam, R.M.; Hornbeck, J.W.; Martin, C.W.

1984-01-01

77

Summer season land cover—Convective cloud associations for the midwest U.S. “Corn Belt”  

NASA Astrophysics Data System (ADS)

Human-induced land cover modifications impact the planetary boundary layer's (PBL) thermal and moisture regimes on mesoscales. We investigate the association of croplands, forest, and the crop-forest “boundary” (CFB) with convective-cloud development (timing, amount) for three target areas (TAs) in the U.S. Midwest “Corn Belt”, during the summer seasons (JJA) 1991-98. For each land cover, hourly satellite-retrieved albedo and cloud-top temperature values are composited for three classes of mid-tropospheric synoptic circulation. On days with the strongest anticyclonicity, there are no consistent differences in convection related to land cover type: cloud development is regionalized and tied primarily to synoptic conditions. However, on days having weaker anticyclonicity the CFB is the dominant site of free convection, suggesting that Non-Classical Mesoscale Circulations (NCMCs) between cropped and adjacent forest areas may operate when reduced subsidence in the mid-troposphere does not effectively cap the PBL. Index terms: Land/atmosphere interactions (3322), Mesoscale meteorology (3329), Climate dynamics (1620), Anthropogenic effects (1803).

Carleton, Andrew M.; Adegoke, Jimmy; Allard, Jason; Arnold, David L.; Travis, David J.

78

Changes in monoterpene mixing ratios during summer storms in rural New Hampshire (USA)  

USGS Publications Warehouse

Monoterpenes are an important class of biogenic hydrocarbons that influence ambient air quality and are a principle source of secondary organic aerosol (SOA). Emitted from vegetation, monoterpenes are a product of photosynthesis and act as a response to a variety of environmental factors. Most parameterizations of monoterpene emissions are based on clear weather models that do not take into account episodic conditions that can drastically change production and release rates into the atmosphere. Here, the monoterpene dataset from the rural Thompson Farm measurement site in Durham, New Hampshire is examined in the context of a set of known severe storm events. While some storm systems had a negligible influence on ambient monoterpene mixing ratios, the average storm event increased mixing ratios by 0.59 ?? 0.21 ppbv, a factor of 93% above pre-storm levels. In some events, mixing ratios reached the 10's of ppbv range and persisted overnight. These mixing ratios correspond to increases in the monoterpene emission rate, ranging from 120 to 1240 g km-2 h -1 compared to an estimated clear weather rate of 116 to 193 g km-2 h-1. Considering the regularity of storm events over most forested areas, this could be an important factor to consider when modeling global monoterpene emissions and their resulting influence on the formation of organic aerosols.

Haase, Karl B.; Jordan, C.; Mentis, E.; Cottrell, L.; Mayne, H. R.; Talbot, R.; Sive, B. C.

2011-01-01

79

Changes in monoterpene mixing ratios during summer storms in rural New Hampshire (USA)  

USGS Publications Warehouse

Monoterpenes are an important class of biogenic hydrocarbons that influence ambient air quality and are a principle source of secondary organic aerosol (SOA). Emitted from vegetation, monoterpenes are a product of photosynthesis and act as a response to a variety of environmental factors. Most parameterizations of monoterpene emissions are based on clear weather models that do not take into account episodic conditions that can drastically change production and release rates into the atmosphere. Here, the ongoing monoterpene dataset from the rural Thompson Farm measurement site in Durham, New Hampshire is examined in the context of a set of known severe storm events. While some storm systems had a negligible influence on ambient monoterpene mixing ratios, the average storm event increased mixing ratios by 0.59 ?? 0.21 ppbv, a factor of 93 % above pre-storm levels. In some events, mixing ratios reached the 10's of ppbv range and persisted overnight. These mixing ratios correspond to increases in the monoterpene emission rate, ranging from 120 to 1240 g km-2 h -1 compared to an estimated clear weather rate of 116 to 193 g km-2 h-1. Considering the regularity of storm events over most forested areas, this could be an important factor to consider when modeling global monoterpene emissions and their resulting influence on the formation of organic aerosols. ?? 2011 Author(s).

Haase, K. B.; Jordan, C.; Mentis, E.; Cottrell, L.; Mayne, H. R.; Talbot, R.; Sive, B. C.

2011-01-01

80

Performance assessment of three convective parameterization schemes in WRF for downscaling summer rainfall over South Africa  

NASA Astrophysics Data System (ADS)

Austral summer rainfall over the period 1991/1992 to 2010/2011 was dynamically downscaled by the weather research and forecasting (WRF) model at 9 km resolution for South Africa. Lateral boundary conditions for WRF were provided from the European Centre for medium-range weather (ECMWF) reanalysis (ERA) interim data. The model biases for the rainfall were evaluated over the South Africa as a whole and its nine provinces separately by employing three different convective parameterization schemes, namely the (1) Kain-Fritsch (KF), (2) Betts-Miller-Janjic (BMJ) and (3) Grell-Devenyi ensemble (GDE) schemes. All three schemes have generated positive rainfall biases over South Africa, with the KF scheme producing the largest biases and mean absolute errors. Only the BMJ scheme could reproduce the intensity of rainfall anomalies, and also exhibited the highest correlation with observed interannual summer rainfall variability. In the KF scheme, a significantly high amount of moisture was transported from the tropics into South Africa. The vertical thermodynamic profiles show that the KF scheme has caused low level moisture convergence, due to the highly unstable atmosphere, and hence contributed to the widespread positive biases of rainfall. The negative bias in moisture, along with a stable atmosphere and negative biases of vertical velocity simulated by the GDE scheme resulted in negative rainfall biases, especially over the Limpopo Province. In terms of rain rate, the KF scheme generated the lowest number of low rain rates and the maximum number of moderate to high rain rates associated with more convective unstable environment. KF and GDE schemes overestimated the convective rain and underestimated the stratiform rain. However, the simulated convective and stratiform rain with BMJ scheme is in more agreement with the observations. This study also documents the performance of regional model in downscaling the large scale climate mode such as El Niño Southern Oscillation (ENSO) and subtropical dipole modes. The correlations between the simulated area averaged rainfalls over South Africa and Nino3.4 index were -0.66, -0.69 and -0.49 with KF, BMJ and GDE scheme respectively as compared to the observed correlation of -0.57. The model could reproduce the observed ENSO-South Africa rainfall relationship and could successfully simulate three wet (dry) years that are associated with La Niña (El Niño) and the BMJ scheme is closest to the observed variability. Also, the model showed good skill in simulating the excess rainfall over South Africa that is associated with positive subtropical Indian Ocean Dipole for the DJF season 2005/2006.

Ratna, Satyaban B.; Ratnam, J. V.; Behera, S. K.; Rautenbach, C. J. deW.; Ndarana, T.; Takahashi, K.; Yamagata, T.

2014-06-01

81

The vertical profile of radar reflectivity of convective cells: A strong indicator of storm intensity and lightning probability?  

NASA Technical Reports Server (NTRS)

Reflectivity data from Doppler radars are used to construct vertical profiles of radar reflectivity (VPRR) of convective cells in mesoscale convective systems (MCSs) in three different environmental regimes. The National Center for Atmospheric Research CP-3 and CP-4 radars are used to calculate median VPRR for MCSs in the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central in 1985. The National Oceanic and Atmospheric Administration-Tropical Ocean Global Atmosphere radar in Darwin, Australia, is used to calculate VPRR for MCSs observed both in oceanic, monsoon regimes and in continental, break period regimes during the wet seasons of 1987/88 and 1988/89. The midlatitude and tropical continental VPRRs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level. In sharp contrast, the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with height beginning just above the freezing level. The tropical oceanic profile in the Darwin area is almost the same shape as that for two other tropical oceanic regimes, leading to the conclustion that it is characteristic. The absolute values of reflectivity in the 0 to 20 C range are compared with values in the literature thought to represent a threshold for rapid storm electrification leading to lightning, about 40 dBZ at -10 C. The large negative vertical gradient of reflectivity in this temperature range for oceanic storms is hypothesized to be a direct result of the characteristically weaker vertical velocities observed in MCSs over tropical oceans. It is proposed, as a necessary condition for rapid electrification, that a convective cell must have its updraft speed exceed some threshold value. Based upon field program data, a tentative estimate for the magnitude of this threshold is 6-7 m/s for mean speed and 10-12 m/s for peak speed.

Zipser, Edward J.; Lutz, Kurt R.

1994-01-01

82

A case study of aerosol impacts on summer convective clouds and precipitation over northern China  

NASA Astrophysics Data System (ADS)

The emissions such as greenhouse gases, precursor gases and particulate matters may directly alter the Earth radiative budget or indirectly modify cloud and precipitation processes, and possibly induce changes in climate and the hydrological cycle at the regional to global scale. The previous publications reported a few quantitative assessments and inconsistent results on the effects of the emissions on cloud and precipitation. The aerosol properties and possible impacts on a convective precipitation case on 4 July 2008 over the urban region of northern China are investigated based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data and the Weather Research and Forecast (WRF) model coupled with Chemistry (WRF–Chem). Results show that the Aerosol Optical Depth (AOD) is over 0.9 in the study area, indicating a high concentration of aerosol pollution. The value of Angstrom exponent in the study area is larger than 1.0, indicating that the main particles in the area are industrial and biomass burning pollution aerosols with radii less than 0.25–0.5 ?m. The modeling results show that the domain-averaged precipitation amount under polluted conditions can be increased up to 17% during the whole cloud lifetime. However, the maximum rainfall rate above 30 mm/h is enhanced, whereas that below 30 mm/h is suppressed in most cloud lifetime. The differences of cloud microphysics and dynamics between polluted and clean conditions indicate that both warm and ice microphysics and updraft are suppressed at the storm's initial and dissipating stages, whereas those at the storm's mature stage are obviously enhanced under polluted conditions.

Guo, Xueliang; Fu, Danhong; Guo, Xin; Zhang, Chunming

2014-06-01

83

Measurement of Attenuation with Airborne and Ground-Based Radar in Convective Storms Over Land Its Microphysical Implications  

NASA Technical Reports Server (NTRS)

Observations by the airborne X-band Doppler radar (EDOP) and the NCAR S-band polarimetric (S-Pol) radar from two field experiments are used to evaluate the surface reference technique (SRT) for measuring the path integrated attenuation (PIA) and to study attenuation in deep convective storms. The EDOP, flying at an altitude of 20 km, uses a nadir beam and a forward pointing beam. It is found that over land, the surface scattering cross-section is highly variable at nadir incidence but relatively stable at forward incidence. It is concluded that measurement by the forward beam provides a viable technique for measuring PIA using the SRT. Vertical profiles of peak attenuation coefficient are derived in two deep convective storms by the dual-wavelength method. Using the measured Doppler velocity, the reflectivities at the two wavelengths, the differential reflectivity and the estimated attenuation coefficients, it is shown that: supercooled drops and (dry) ice particles probably co-existed above the melting level in regions of updraft, that water-coated partially melted ice particles probably contributed to high attenuation below the melting level.

Tian, Lin; Heymsfield, G. M.; Srivastava, R. C.; O'C.Starr, D. (Technical Monitor)

2001-01-01

84

A Dual Doppler Variational Objective Analysis as Applied to Studies of Convective Storms.  

National Technical Information Service (NTIS)

Numerous investigations in the past ten years have sought to determine wind velocities in precipitating weather systems from pulse Doppler data. At least two Doppler radars scanning a common volume are necessary to adequately deduce in-storm velocities. A...

C. L. Ziegler

1978-01-01

85

Satellite detection of severe convective storms by their retrieved vertical profiles of cloud particle effective radius and thermodynamic phase  

NASA Astrophysics Data System (ADS)

A new conceptual model that facilitates the inference of the vigor of severe convective storms, producing tornadoes and large hail, by using satellite-retrieved vertical profiles of cloud top temperature (T)-particle effective radius (re) relations is presented and tested. The driving force of these severe weather phenomena is the high updraft speed, which can sustain the growth of large hailstones and provide the upward motion that is necessary to evacuate the violently converging air of a tornado. Stronger updrafts are revealed by the delayed growth of re to greater heights and lower T, because there is less time for the cloud and raindrops to grow by coalescence. The strong updrafts also delay the development of a mixed phase cloud and its eventual glaciation to colder temperatures. Analysis of case studies making use of these and related criteria show that they can be used to identify clouds that possess a significant risk of large hail and tornadoes. Although the strength and direction of the wind shear are major modulating factors, it appears that they are manifested in the updraft intensity and cloud shapes and hence in the T-re profiles. It is observed that the severe storm T-re signature is an extensive property of the clouds that develop ahead in space and time of the actual hail or tornadic storm, suggesting that the probabilities of large hail and tornadoes can be obtained at substantial lead times. Analysis of geostationary satellite time series indicates lead times of up to 2 h.

Rosenfeld, Daniel; Woodley, William L.; Lerner, Amit; Kelman, Guy; Lindsey, Daniel T.

2008-02-01

86

ST-AR (STorm-ARchive): A project developed to assess the ground effects of severe convective storms in the Po Valley  

NASA Astrophysics Data System (ADS)

An analysis of remote sensing data related to convective precipitation events in Northern Italy is presented in order to evaluate the ability of the logistic regression models to calculate the probability of particular ground effects as hail, wind damage or small floods. In order to carry out and test the method, a database containing both remote sensing data and ground effects reports about convective thunderstorms in 2003 and 2004 summers was developed. Numerous parameters were extracted from satellite, radar and lighting location systems data of the 2003 sample and were used to determine probability models. The sample of 2004 data was used for a preliminary test of the method. The method of logistic regression seems to be a useful tool to evaluate a binary response (presence or absence of a particular effect) on the basis of continuous or binary variables. The calculated indexes of success are also presented and analysed. The best results are obtained with the model to establish the presence of wind damage and the one for determining the absence of important ground effects. All the models present moreover the advantage of having low false alarm rates. The obtained results encourage the use of this statistical technique for further statistical analysis on larger data set.

Collino, Elena; Bonelli, Paolo; Gilli, Luciano

87

Origin of the pre-tropical storm Debby (2006) African easterly wave-mesoscale convective system  

NASA Astrophysics Data System (ADS)

The origins of the pre-Debby (2006) mesoscale convective system (MCS) and African easterly wave (AEW) and their precursors were traced back to the southwest Arabian Peninsula, Asir Mountains (AS), and Ethiopian Highlands (EH) in the vicinity of the ITCZ using satellite imagery, GFS analysis data and ARW model. The sources of the convective cloud clusters and vorticity perturbations were attributed to the cyclonic convergence of northeasterly Shamal wind and the Somali jet, especially when the Mediterranean High shifted toward east and the Indian Ocean high strengthened and its associated Somali jet penetrated farther to the north. The cyclonic vorticity perturbations were strengthened by the vorticity stretching associated with convective cloud clusters in the genesis region—southwest Arabian Peninsula. A conceptual model was proposed to explain the genesis of convective cloud clusters and cyclonic vorticity perturbations preceding the pre-Debby (2006) AEW-MCS system.

Lin, Yuh-Lang; Liu, Liping; Tang, Guoqing; Spinks, James; Jones, Wilson

2013-05-01

88

Infrasound From Convective Storms: An Experimental Test of Electrical Source Mechanisms  

Microsoft Academic Search

paper reports the results of such a test. We find that the spatial and temporal correlation between the two kinds of emissions is much lower than we would expect if the two were causally related; therefore the source of severe storm infrasound is probably not electrical.

William H. Beasley; T. M. Georges; Michael W. Evans

1976-01-01

89

A Life History of an Intense Mesoscale Convective Storm in Oklahoma  

Microsoft Academic Search

A simple automated objective analysis scheme is developed to analyze upper air sounding data from the National Severe Storm Laboratory mesonetwork. This scheme uses a combination of Cressman' successive correction technique and cubic spline curve fitting.This scheme is applied to a squall line case that occurred on 8 June 1966 along the confluent line where and air from the desert

Yoshmitsu Ogura; Yi-Leng Chen

1977-01-01

90

Mesospheric concentric gravity waves generated by multiple convective storms over the North American Great Plain  

NASA Astrophysics Data System (ADS)

We report on six continuous hours of OH airglow imager observations (at z ˜ 87 km) of convectively generated gravity waves (GWs) near Fort Collins, Colorado, on the evening of 08 September 2005. These GWs appeared as nearly concentric rings, and had epicenters near the locations of deep convection in three thunderstorms in Colorado, Nebraska and South Dakota. Using GOES satellite and weather radar observations, we show that the GWs closely follow the thunderstorms. Using the background wind from a nearby radar, the intrinsic wave parameters and vertical wavelengths are calculated. The temperature perturbations are estimated to be T?/T¯ ˜ 1-3% for GWs with horizontal wavelengths ?h ˜ 20-40 km and horizontal phase speeds ˜40-60 m/s. The horizontal wavelengths of GWs from a convective cluster decreased in time from 30 to 15 km. We employ convective plume and ray-trace models to simulate the GW-induced OH intensity perturbations from convective plumes, clusters and complexes. We find that the results using the background model wind (radiosonde/TIME-GCM) agree well with the late-time observations, when the images are dominated by southwestward, short-wavelength, high-frequency GWs. These late-time GWs propagate against the background wind, and have ?h ˜ 30-40 km and periods of ? ˜ 20-30 min. The OH intensity perturbations are enhanced because the vertical wavelengths ?z increased, T?/T¯ increased, and the vertical velocity perturbations w? decreased (because the GWs were near their reflection levels). We also find that these short-wavelength GWs were created ˜5 h earlier by an extremely energetic, deep convective plume in South Dakota, thereby showing that small-scale, convective GWs directly link the troposphere and mesopause region.

Vadas, Sharon; Yue, Jia; Nakamura, Takuji

2012-04-01

91

Application of the Zhang-Gal-Chen Single-Doppler Velocity Retrieval to a Deep Convective Storm.  

NASA Astrophysics Data System (ADS)

The Zhang-Gal-Chen single-Doppler velocity retrieval (SDVR) technique is applied to a multicell storm observed by three radars near the Orlando, Florida, airport on 9 August 1991. This dataset is unique in that 3-min volume scans at very high spatial resolution (200 m) are available during a 24-min period. The retrieved (unobserved) wind, determined using only the radial wind and reflectivity from one of the radars, is compared to the (observed) winds obtained from a hybrid three-dimensional wind synthesis.Error statistics demonstrate that the retrievals perform best when applied in a reference frame moving with the storm; however, the results also show that the specification of this frame is problematic. The findings also indicate that, in an environment where the mean flow has a critical layer, the moving reference frame is best defined as a function of height rather than a volume mean. The benefit of such a reference frame is case dependent and is best realized in regions such as a surface cold pool or upper-level divergence at storm top.Error statistics demonstrate that the SDVR technique recovers the horizontal wind with greater accuracy than it does the vertical velocity-suggesting that for deep convection, the absence of dynamical constraints is critical. The kinematic and O'Brien techniques and a new variational technique, in which the solution to a second-order ordinary differential equation for the vertical velocity is expressed in terms of Bessel functions, are tested as possible alternatives to the SDVR vertical velocity. Results indicate that this new technique yields vertical velocities significantly better than those using the other three methods.

Lazarus, Steven; Shapiro, Alan; Droegemeier, Kelvin

2001-05-01

92

Unforced variability in summer storm track position over the past millennium  

NASA Astrophysics Data System (ADS)

Gridded past millennium climate reconstructions, encompassing the European continent (e.g. Luterbacher et al 2004), based on proxy records, have previously been generated assuming that spatial temperature covariance across the region behaves in the past in the same way as it does in the observational period. This strategy bears the risk of artificially identifying the same patterns of variability as presently observed and overlooking periodically occurring modes of internal climate variability, that are not uniformly spatio-temporally expressed. Here, we construct regional proxy composites for Europe which are not constrained by the modes of variability expressed in the 20th century, and should thus broadly represent coherent regional summer temperatures back through time, independent from present modes of variability. The proxy data set analysed was provided by the efforts of the EU 6th Framework Millennium project. Proxy data are dominated by tree ring width, density and annual height increment. Four composites are used describing summer temperatures in the Arctic, Central, Pyrenean and Alpine zones of Europe. The proxy data sets cover the period AD 1260-1996. We jointly analyse an ensemble of simulations with global climate models participating in the Climate Model Intercomparison Project (CMIP5) included in the 5th Assessment report of the Intergovernmental Panel on Climate Change (IPCC) covering the period AD 850-2005, with the above aims in mind. The climate models were driven by estimations of the main external forcings. The implementations of these forcings may vary among simulations, depending on the different estimates used and on the structure of the models themselves. We analyse three simulations (CCSM4, IPSL, MPI-ESM) that, at the time of writing, provide daily data over the period AD 850-2005 obtained with the very same model version through the whole period. The analysis of both proxy and model data allowed us to more precisely identify the behaviour of the internal climate mode identified.

Gagen, Mary; Zorita, Eduardo; McCarroll, Danny; Loader, Neil; Young, Giles; Robertson, Iain

2014-05-01

93

High resolution radiometric measurements of convective storms during the GATE experiment  

NASA Technical Reports Server (NTRS)

Using passive microwave data from the NASA CV-990 aircraft and radar data collected during the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE), an empirical model was developed relating brightness temperatures sensed at 19.35 GHz to surface rainfall rates. This model agreed well with theoretical computations of the relationship between microwave radiation and precipitation in the tropics. The GATE aircraft microwave data was then used to determine the detailed structure of convective systems. The high spatial resolution of the data permitted identification of individual cells which retained unique identities throughout their lifetimes in larger cloud masses and allowed analysis of the effects of cloud merger.

Fowler, G.; Lisa, A. S.

1976-01-01

94

Sensitivity of regional climate simulations of the summer 1998 extreme rainfall to convective parameterization schemes  

NASA Astrophysics Data System (ADS)

In this paper, a comparison study of three cumulus parameterization schemes (CPSs), Kain-Fritsch2 (KF2), Grell (GR) and Anthes-Kuo (AK), is carried out using the Pennsylvania State University-National Center for Atmospheric Research mesoscale model (i.e., MM5). The performances of three CPSs are examined in simulations of the long-term heavy Meiyu-frontal rainfall events over the middle to lower reaches of the Yangtze River Basin (YRB-ML) during the summer of 1998. The initial and lateral boundary atmosphere conditions are taken from the National Centers for Environmental Prediction/Department of Energy Reanalysis-2 (R-2) data. The experiment with KF2 scheme (EX_KF2) reproduces reasonably well the major rainfall events, especially the heavy rainfall over YRB-ML during the later stage, and the middle and lower troposphere circulation patterns. In contrast, the experiments with both GR and AK schemes (EX_GR and EX_AK) only simulate the heavy rainfall during the first Meiyu rainy phase with weak intensity, and almost miss the rainfall along YRB-ML during the second phase. The analyses show that the location of 500 hPa western Pacific subtropical high during the first rainy phase, the northward advance during the transition period and the retreat during the second rainy phase, observed from the R-2 data, are successfully captured by EX_KF2, compared to the poor performance of EX_GR and EX_AK. A reasonable proportion of the subgrid-scale rainfall and smaller biases of temperature and moisture from lower to middle troposphere in EX_KF2 decide its good rainfall simulations, in contrast with the absolutely high proportions and the cold and dry biases caused by the decreased vertically convective transportation and the weak southwesterly wind in EX_GR and EX_AK. Overall, the three CPSs show substantial intersimulation differences in rainfall as well as in three-dimensional atmospheric structures, and KF2 shows superior performances. The results suggest that the realistic subgrid-scale CPS is still highly required for the high-resolution regional climate models to simulate the heavy rainfall events.

Liu, Hongbo; Wang, Bin

2011-10-01

95

Laboratory and field observations related to ice particle and aircraft charging in convective storms  

NASA Technical Reports Server (NTRS)

Graupel particle charging in simulated cloud conditions which show the need for the presence of ice crystals and cloud water simultaneously except under conditions where secondary ice crystal production occurs when charging initially occurs in the absence of ice crystals was examined. The magnitude of the charging increases with size of ice crystals, and impact velocity; it is also sensitive to impurities. The magnitude of the charge is also sensitive to temperature and the sign changes between -10 and -20 C, depending on cloud liquid water content. Aircraft studies were carried out in Montana convective clouds to test the validity of the extrapolation of the laboratory data to the atmosphere from the viewpoint of generation of charge, electric field, and aircraft charging during cloud penetration.

Christian, H.; Lillie, L.; Saunders, C. P. R.; Hallett, J.

1983-01-01

96

Three-Dimensional Simulation of a Convective Storm: Sensitivity Studies on Subgrid Parameterization and Spatial Resolution.  

NASA Astrophysics Data System (ADS)

This article presents the main features of a three-dimensional model for deep convection developed with special care given to the formulation of subgrid turbulent processes. It explicitly simulates the dynamics of turbulent eddies, including condensation and precipitation processes. Second-order moments are expressed as a function of the grid-averaged field of variables and of a prognostic turbulent kinetic energy. The formulation includes a simple statistical treatment of subgrid condensation and subgrid conversion of cloud water into rain water. The coherence and relative importance of the various closure hypotheses are tested in an idealized case of precipitating cloud.Results indicate the extent that features of the computed field are dependent on hypotheses used in the turbulence closure, choice of the basic turbulent variables, and formulation of the second-order moments. Significant benefits are obtained from the use of variables that are conserved in the condensation process. The computation of grid-scale condensation and precipitation is mostly dependent on the hypotheses made respectively for subgrid condensation and precipitation. Finally, it is shown that an advanced subgrid turbulence parameterization can partially compensate for the effects of a low spatial resolution.

Redelsperger, J. L.; Sommeria, G.

1986-11-01

97

Summer Storm Fire Safety  

MedlinePLUS

... Read more about generator safety Heating Safety Kerosene heaters may not be legal in your area and ... can be a source of toxic fumes. Alternative heaters need their space. Keep anything combustible at least ...

98

Analysis of Summer Thunderstorms in Central Alabama Using the NASA Land Information System  

NASA Technical Reports Server (NTRS)

Forecasters have difficulty predicting "random" afternoon thunderstorms during the summer months. Differences in soil characteristics could be a contributing factor for storms. The NASA Land Information System (LIS) may assist forecasters in predicting summer convection by identifying boundaries in land characteristics. This project identified case dates during the summer of 2009 by analyzing synoptic weather maps, radar, and satellite data to look for weak atmospheric forcing and disorganized convective development. Boundaries in land characteristics that may have lead to convective initiation in central Alabama were then identified using LIS.

James, Robert; Case, Jonathan; Molthan, Andrew; Jedloved, Gary

2010-01-01

99

Mesoscale aspects of jet streak coupling and implications for the short term forecasting of severe convective storms. [severe environmental storms and mesoscale experiment (SESAME)  

NASA Technical Reports Server (NTRS)

An analysis of a tornado outbreak in Wichita Falls, Texas was analyzed. The coupling of upper and lower tropospheric jet streaks, leading to severe storm outbreaks is illustrated. The high resolution SESAME data sets indicate that mass and momentum adjustments which couple upper and lower tropospheric jets occur within a 3 to 6 hr time frame over a 100 to 500 km domain, and establish the role of isallobaric forcing in the storm development. It is suggested that the output rate of data from the existing 12 hr network be increased to provide better temporal resolution of wind, mass and moisture data.

Uccellini, L. W.; Kocin, P. J.

1981-01-01

100

Effects of acid deposition on dissolution of carbonate stone during summer storms in the Adirondack Mountains, New York, 1987-89  

USGS Publications Warehouse

This study is part of a long-term research program designed to identify and quantify acid rain damage to carbonate stone. Acidic deposition accelerates the dissolution of carbonate-stone monuments and building materials. Sequential sampling of runoff from carbonate-stone (marble) and glass (reference) microcatchments in the Adirondack Mountains in New York State provided a detailed record of the episodic fluctuations in rain rate and runoff chemistry during individual summer storms. Rain rate and chemical concentrations from carbonate-stone and glass runoff fluctuated three to tenfold during storms. Net calcium-ion concentrations from the carbonatestone runoff, a measure of stone dissolution, typically fluctuated twofold during these storms. High net sulfate and net calcium concentrations in the first effective runoff at the start of a storm indicated that atmospheric pollutants deposited on the stone surface during dry periods formed calcium sulfate minerals, an important process in carbonate stone dissolution. Dissolution of the carbonate stone generally increased up to twofold during coincident episodes of low rain rate (less than 5 millimeters per hour) and decreased rainfall (glass runoff) pH (less than 4.0); episodes of high rain rate (cloudbursts) were coincident with a rapid increase in rainfall pH and also a rapid decrease in the dissolution of carbonate-stone. During a storm, it seems the most important factors causing increased dissolution of carbonate stone are coincident periods of low rain rate and decreased rainfall pH. Dissolution of the carbonate stone decreased slightly as the rain rate exceeded about 5 millimeters per hour, probably in response to rapidly increasing rainfall pH during episodes of high rain rate and shorter contact time between the runoff and the stone surface. High runoff rates resulting from cloudbursts remove calcium sulfate minerals formed during dry periods prior to storms and also remove dissolution products formed in large measure by chemical weathering as a result of episodes of low rain rate and decreased rainfall pH during a storm.

Schuster, Paul F.; Reddy, Michael M.; Sherwood, S. I.

1994-01-01

101

Convections  

NSDL National Science Digital Library

This experiment demonstrates convection, the fundamental reason we have weather. Explore what happens when cold ice hits a tub of warm water. This activity guide includes a step-by-step instructional video.

Center, Saint L.

2013-01-30

102

The Impact on Simulated Storm Structure and Intensity of Variations in the Lifted Condensation Level and the Level of Free Convection  

NASA Technical Reports Server (NTRS)

The sensitivities of convective storm structure and intensity to changes in the altitudes of the prestorm environmental lifted condensation level and level of free convection axe studied using a full-physics three-dimensional cloud model. Matrices of simulations are conducted for a range of LCL=LFC altitudes, using a single moderately-sheared curved hodograph trace in conjunction with 1 convective available potential energy values of either 800 or 2000 J/kg, with the matrices consisting of all four combinations of two distinct choices of buoyancy and shear profile shape. For each value of CAPE, the LCL=LFC altitudes are also allowed to vary in a series of simulations based on the most highly compressed buoyancy and shear profiles for that CAPE, with the environmental buoyancy profile shape, subcloud equivalent potential temperature, subcloud lapse rates of temperature and moisture, and wind profile held fixed. For each CAPE, one final simulation is conducted using a near optimal LFC, but a lowered LCL, with a neutrally buoyant environmental thermal profile specified in between. Results show that, for the buoyancy-starved small-CAPE environments, the simulated storms are supercells and are generally largest and most intense when LCL=LFC altitudes lie in the approximate range 1.5-2.5 km above the surface. The simulations show similar trends for the shear-starved large-CAPE environments, except that conversion from supercell to multicell morphology frequently occurs when the LCL is high. For choices of LCL=LFC height within the optimal 1.5-2.5 km range, peak storm updraft overturning efficiency may approaches unity relative to parcel theory, while for lower LCL=LFC heights, overturning efficiency is reduced significantly. The enhancements of overturning efficiency and updraft diameter with increasing LFC height are shown to be the result of systematic increases in the mean equivalent potential temperature of the updraft at cloud base. For the shear-starved environments, the tendency for outflow dominance is eliminated, but a large overturning efficiency maintained, when a low LCL is used in conjunction with a high LFC. The result regarding outflow dominance at high LCL is consistent with expectations, but the beneficial effect of a high LFC on convective overturning efficiency has not previously been widely recognized. The simulation findings here also appear to be consistent with statistics from previous severe storm environment climatologies, but provide a new framework for interpreting those statistics.

McCaul, Eugene W., Jr.; Cohen, Charles; Arnold, James E. (Technical Monitor)

2001-01-01

103

Convective Inhibition as a Predictor of the Outbreak of Convection in AVE-SESAME II (Severe Environmental Storms and Mesoscale Experiment).  

National Technical Information Service (NTIS)

In this paper, one data set from the Sever Environmental Storms and Mesosclae Experiment (SESAME) is examined. The case involves a squall line which developed in a region of weak convergence. Both observational analysis and modeling are used to determine ...

F. P. Colby

1983-01-01

104

Summer Study Program in Geophysical Fluid Dynamics-The Influence of Convection on Large-Scale Circulations-1988.  

National Technical Information Service (NTIS)

Contents: Review of Dry Convection; Other Buoyant Plumes and Thermals; Global Convection; Moist Thermodynamics; Non Precipitating Cloud; Taxonomy of Precipitating Clouds; The Dynamics of precipitating Convection; Tropical Cyclones: Observations and Energe...

G. R. Flierl P. J. Goulart

1989-01-01

105

Severe storms and storm systems: Scientific background, methods, and critical questions  

Microsoft Academic Search

The structure and dynamics of severe convective storms and their mesoscale environments is described on the basis of current literature. Numerical modeling of regional and cloud-scale meteorology is reviewed with respect to its contribution to the understanding of convective storm evolution. Observation techniques are surveyed briefly. Critical questions, principally on the triggering of convective storms, are listed and a U.S.

Douglas K. Lilly

1975-01-01

106

Inner magnetosphere responses to the solar wind-magnetosphere energy transfers: Storms, saw-tooth oscillations and steady magnetospheric convection events.  

NASA Astrophysics Data System (ADS)

We present a quantitative investigation of the processes controlling the inner magnetospheric magnetic field topology during several dynamical states of the Earth's magnetosphere, namely, geomagnetic storms, sawtooth oscillations and steady magnetospheric convection (SMC) events. For this analysis we use our event-oriented model, a unique tool to provide a realistic representation of the magnetospheric magnetic field during disturbed times for specific events. The model is specified using solar wind and IMF data, all available in-situ and ground magnetic field measurements, and in addition, the magnetic field direction information derived from plasma electron distribution functions from the LANL MPA instrument. The output from this model is an input to the Inner Magnetosphere Particle Transport and Acceleration model (IMPTAM). This model traces ions and electrons with arbitrary pitch angles in the drift approximation in time-dependent magnetic and electric fields taking into account the loss processes. The initial particle distribution and boundary conditions are set and varied during the modeling based on observations during specific events. We model two storm events, one moderate with Dst drop of - 150 nT on November 6-7, 1997 and one intense with Dst drop of - 250 nT on October 21-23, 1999, two saw-tooth events, on October 22, 2001 and April 18, 2002, and two SMC events on February 3-4, 1998 and May 5, 1998. With this modeling we quantify which of the major current systems cause what aspects of the magnetic field distortion during magnetospheric dynamical states. With our physics-based numerical models we will determine the flow of plasma leading to the current systems that dominate the magnetic field distortion of the magnetosphere. In addition, the contribution of temporal variations of plasma dynamics (e.g., dispersed and dispersionless injections) to magnetic field distortions will be investigated. Furthermore, the detailed comparison between sawtooth oscillations and steady magnetosphric convection (SMC) events in terms of their observational features and model outputs will be conducted. By the analysis of sawtooth oscillations and steady magnetospheric convection (SMC) events a fundamental question whether the sawtooth events form a new class of magnetospheric events or whether they are simply quasi-periodic storm-time substorms will be addressed.

Ganushkina, N.; Kubyshkina, M.; Liemohn, M.; Pulkkinen, T.

2009-04-01

107

10-25-day intraseasonal variations of convection and circulation associated with thermal state of the western Pacific warm pool during boreal summer  

NASA Astrophysics Data System (ADS)

This study focuses on the characteristics of 10-25-day oscillation associated with the interannual variability of the thermal state in the western Pacific warm pool. The time series of 10-25-day oscillation shows a distinct feature between warm (WARM case) and cold (COLD case) summers over the western Pacific warm pool. The significant negative relationship between the time series of 10-25-day convection anomalies in Warm and Cold cases appears over most of Asian-Pacific region manifesting the interactions between the convection on interannual and 10-25-day intraseasonal time scales. At the peak and trough stages of 10-25-day convection oscillation, a Gill-type low-level atmospheric circulation anomaly, cyclonic or anticyclonic, appears northwest of the convection anomaly, This relationship between the convection and circulation exists both in Warm case and in Cold case. However, at other stages rather than the peak and trough stages, there is no Gill-type circulation response, and the circulation anomaly shows a distinct feature between the Warm and Cold cases, although the convection oscillation exhibits a roughly similar feature.

Ren, B. H.; Huang, R. H.

2002-03-01

108

Simulations of summer monsoon climate over East Asia with a Regional Climate Model (RegCM) using Tiedtke convective parameterization scheme (CPS)  

NASA Astrophysics Data System (ADS)

In this study, we implemented the Tiedtke convective parameterization scheme (CPS) into the Abdus Salam International Centre for Theoretical Physics (ICTP) Regional Climate Model version 3 (RegCM3) and simulated the East Asian Summer Monsoon (EASM) climate. A 6-year experiment was completed, from September 1996 through August 2002, and compared with an analogous experiment employing the Grell CPS option available in RegCM3. The ability of the model to represent the average climatology was investigated. Our results indicate that the Tiedtke CPS shows a generally good performance in describing surface climate and large-scale circulation throughout the summer monsoon period. Compared to the simulation with Grell CPS, the simulation with Tiedtke scheme shows a number of improvements, including a better distribution of summer monsoon precipitation due to a better positioning of the Western Pacific Subtropical High (WPSH) in the middle troposphere and the southwesterly jet in the lower troposphere, and more realistic seasonal evolution of the monsoon precipitation. The cold surface air temperature bias characteristic frequently seen in Grell scheme over this region is also reduced. Generally, the Tiedtke scheme simulates warm and wet atmospheric conditions in the middle and lower tropospheres, a result more in agreement with the European Centre for Medium-Range Weather Forecasts (ECMWF) 40 Years analysis (ERA-40). The Tiedtke scheme is more prone to activate convection in the lower troposphere than the Grell scheme due to more moist static energy available for activating and supporting the development of convection systems.

Bao, Yan

2013-12-01

109

Case studies of sprite-producing and non-sprite-producing summer thunderstorms  

NASA Astrophysics Data System (ADS)

Three summer thunderstorms in the eastern region of China were analyzed in detail using multiple data, including Doppler radar, lightning location network, TRMM (Tropical Rainfall Measuring Mission), MTSAT (Multi-Function Transport Satellite) images, NCEP (National Centers for Environmental Prediction) Reanalysis, and radiosonde. Two of the three storms were sprite-producing and the other was non-spriteproducing. The two sprite-producing storms occurred on 1-2 August and 27-28 July 2007, producing 16 and one sprite, respectively. The non-sprite-producing storm occurred on 29-30 July 2007. The major objective of the study was to try to find possible differences between sprite-producing and non-sprite producing storms using the multiple datasets. The results showed that the convection in the 1-2 August storm was the strongest compared with the other storms, and it produced the largest number of sprites. Precipitation ice, cloud ice and cloud water content in the convective regions in the 1-2 August storm were larger than in the other two storms, but the opposite was true in the weak convective regions. The storm microphysical properties along lines through parent CG (cloud-to-ground lightning) locations showed no special characteristics related to sprites. The flash rate evolution in the 1-2 August storm provided additional confirmation that major sprite activity coincides with a rapid decrease in the negative CG flash rate. However, the evolution curve of the CG flash rate was erratic in the sprite-producing storm on 27-28 July, which was significantly different from that in the 1-2 August storm. The average positive CG peak current in sprite-producing storms was larger than that in the non-sprite-producing one.

Yang, Jing; Yang, Meirong; Liu, Chao; Feng, Guili

2013-11-01

110

Response of mating activity of the plainfin midshipman to inflow into San Francisco Bay from a summer storm  

NASA Astrophysics Data System (ADS)

The plainfin midshipman (Porichthys notatus) is a small fish which nests in estuarine waters during summer months. The male makes a loud continuous droning call to attract females to a nest, where eggs and newborn young are guarded by the male. Midshipman calls have been recorded continuously with a fixed hydrophone near a pier in San Francisco Bay, over two successive mating seasons. A dramatic increase in calling followed a very unusual intense rainstorm in mid-October 2009. This suggests a response to biochemical stimuli from the runoff water. Further study may make it possible to isolate the contaminants producing this alteration of sexual behavior.

Bland, R. W.

2010-12-01

111

Roles of the tropical convective activities over different regions in the earlier onset of the South China Sea summer monsoon after 1993  

NASA Astrophysics Data System (ADS)

The South China Sea summer monsoon (SCSSM) onset experiences evidently an interdecadal change around mid-1990s. Generally, the SCSSM broke out half a month earlier during 1994-2010 than IN 1978-1993. Possible causes are analyzed in this study. The results suggest that the earlier onset of the SCSSM is due to earlier retreat of the subtropical high (STH) over the western Pacific, which is closely related to enhanced intraseasonal oscillations of tropical convections. The enhanced convective activities can be found in three regions: the eastern tropical Indian Ocean (TIO), the equatorial SCS-Kalimantan (ESK) and the tropical western Pacific (TWP). Both convections in the TIO and the ESK are greatly influenced by the interaction of the westerly wind from the TIO and the easterly wind from the TWP. The convections in the TIO are never found to propagate to the east of 100°E, while those in the ESK are usually quite weak and not great help to the SCSSM onset. Our results suggest that the earlier retreat of the STH is mainly caused by the enhanced convections in the TWP, while the later may be the consequence of warming over the TWP on the interdecadal timescale. Therefore, the La Niña-like interdecadal change of the sea surface temperature (SST) in the Pacific is likely to be responsible for the interdecadal advance of the SCSSM onset.

Yuan, Fang; Chen, Wen

2013-07-01

112

Boreal summer intraseasonal variability simulated in the NCEP climate forecast system: insights from moist static energy budget and sensitivity to convective moistening  

NASA Astrophysics Data System (ADS)

The NCEP Climate Forecast System (CFS) with the relaxed Arakawa Schubert (RAS, hereafter referred to as CTRL) convection scheme of Moorthi and Suarez exhibits better performance in representing boreal summer tropical intraseasonal variability as compared with a simulation using simplified Arakawa-Schubert scheme. The intraseasonal moist static energy (MSE) budget is analyzed in this version of the CFS model (CTRL), which produces realistic eastward and northward propagation characteristics. The moist and thermodynamic processes involved in the maintenance and propagation of the poleward moving intraseasonal oscillation (ISO) disturbances are examined here. Budget diagnostics show that horizontal MSE advection is the principal component of the budget, contributing to the poleward movement of the convection. The injection of MSE moistens the atmosphere north of the convective area causing the poleward movement of convection by destabilization of the atmosphere. The moistening process is mainly contributed by the climatological wind acting on the anomalous moisture gradient as confirmed from the examination of moisture advection equation. While surface enthalpy fluxes (consisting of radiative and surface turbulent heat fluxes) maintain the ISO anomalies, they oppose the MSE tendency due to horizontal advection thus regulating the poleward propagation characteristics. In addition, the model results show that wind-evaporation feedback dominates over cloud-radiation feedback for ISO propagation; this is in contrast to our estimates using the newly available European Centre for Medium Range Weather Forecasts Interim reanalysis. Sensitivity experiments suggest that intraseasonal variability in the CFS model with the RAS scheme is highly sensitive to the parameterization of both the shallow convection and the convective rain evaporation and downdrafts. Removal of these components adversely affects the propagation characteristics and greatly reduces the amplitude of intraseasonal variability. Our results support the primary importance of the moisture preconditioning ahead of the ISO and the physical relationship between moisture and precipitation. For realistic ISO simulations, models need to represent these features appropriately.

Sooraj, K. P.; Seo, Kyong-Hwan

2013-09-01

113

The benefit of convection permitting horizontal resolution in a climate model for the representation of summer precipitation in the Alp region.  

NASA Astrophysics Data System (ADS)

Accurate model projections of precipitation distribution, especially the frequency and intensity of wet extremes, still remains one of the largest challenges in the climate model community. To investigate possible improvements and limitations in simulated precipitation using convection permitting resolution, in this study we have run the HARMONIE regional climate model at 2 km resolution over the Alp region in Europe. The model is configured with model physics based on the research MESO-NH non-hydrostatic model with explicitly resolved convection. The question we seek to answer is how well summer precipitation characteristics, with focus on convective events, on sub-daily time scales are captured by HARMONIE in an area with complex terrain. Our means to answer this question involves the evaluation of diurnal timing and the intensities, durations and frequencies of precipitation spells. The model results are evaluated against high-resolution gridded observations, based on synoptic as well as radar measurements, and also against two other HARMONIE runs at the coarser 6.25 and 15 km resolutions to investigate the sensitivity to horizontal resolution. In these double nested experiments, the 6.25 and 15 km runs have been simulated on the CORDEX Europe domain forced by ERA-Interim on the boundaries, and in turn provide the boundary conditions to the 2 km simulation. In contrast to the 2 km run these model simulations uses a hydrostatic dynamical core and with convection parametrisation. Our results show a significantly improved realism of the sub-daily temporal characteristics of precipitation at convection permitting resolution, especially concerning duration and frequency as well as the atmospheric conditions leading to the events. The diurnal timing of precipitation is also better represented at the highest resolution in areas of flatter terrain whereas in connection with steep orography all simulations deviates significantly from observations. These results indicate a clear benefit of using convection permitting scales with explicit convection and a means to increase our confidence in possible changes in precipitation and its extremes induced by a perturbed climate system.

Lind, Petter; Lindstedt, David; Jones, Colin; Kjellström, Erik

2014-05-01

114

What is a geomagnetic storm?  

Microsoft Academic Search

The authors present a review of geomagnetic storm research. They examine the interaction of the solar wind with the magnetosphere. They argue that a storm results from the extended interaction of the solar wind\\/magnetosphere when a strong convection electric field is generated, which is able to perturb the ring current above some threshold level, triggering the event. They touch on

W. D. Gonzales; J. A. Joselyn; Y. Kamide; H. W. Kroehl; G. Rostoker; B. T. Tsurutani; V. M. Vasyliunas

1994-01-01

115

Urban signatures in the spatial clustering of summer heavy rainfall events over the Beijing metropolitan region  

NASA Astrophysics Data System (ADS)

climatology of summer heavy rainfall events over the Beijing metropolitan region during 2008-2012 is investigated with the aid of an observational network of rain gauges and the Weather Research and Forecasting model. Two "hot spots" of higher frequency of summer heavy rainfall events are observed. One is located over the urban core region and the other resides in the climatological downwind region. Two comparative sets of model runs are designed to assess the effect of land surface properties with and without the presence of the city on the model simulation results. By comparing the two sets of model runs, the changes of rainfall statistics, behaviors of storm cells, and variables related to convection due to urbanization are analyzed and quantified. The intensity of heavy rainfall is increased over the urban and downwind region, corresponding to the locations of the two observed hot spots based on rain gauges. The changes of rainfall statistics suggest that the probability distribution of rainfall is shifted toward a heavier upper tail distribution. The Lagrangian properties of storm cells are examined using a newly developed Storm-Cell Identification procedure. High-echo storm cells tend to split approaching the city and merge in the downwind region. The level of free convection and the height of the planetary boundary layer are significantly increased over the urban region and maximum convective available potential energy is decreased. Increased sensible heat flux from the urban surfaces plays a dominant role in the modification of simulated rainfall from a climatological perspective.

Yang, Long; Tian, Fuqiang; Smith, James A.; Hu, Heping

2014-02-01

116

Calibration of a convective parameterization scheme in the WRF model and its impact on the simulation of East Asian summer monsoon precipitation  

NASA Astrophysics Data System (ADS)

Reasonably modeling the magnitude, south-north gradient and seasonal propagation of precipitation associated with the East Asian summer monsoon (EASM) is a challenging task in the climate community. In this study we calibrate five key parameters in the Kain-Fritsch convection scheme in the WRF model using an efficient importance-sampling algorithm to improve the EASM simulation. We also examine the impacts of the improved EASM precipitation on other physical process. Our results suggest similar model sensitivity and values of optimized parameters across years with different EASM intensities. By applying the optimal parameters, the simulated precipitation and surface energy features are generally improved. The parameters related to downdraft, entrainment coefficients and CAPE consumption time (CCT) can most sensitively affect the precipitation and atmospheric features. Larger downdraft coefficient or CCT decrease the heavy rainfall frequency, while larger entrainment coefficient delays the convection development but build up more potential for heavy rainfall events, causing a possible northward shift of rainfall distribution. The CCT is the most sensitive parameter over wet region and the downdraft parameter plays more important roles over drier northern region. Long-term simulations confirm that by using the optimized parameters the precipitation distributions are better simulated in both weak and strong EASM years. Due to more reasonable simulated precipitation condensational heating, the monsoon circulations are also improved. By using the optimized parameters the biases in the retreating (beginning) of Mei-yu (northern China rainfall) simulated by the standard WRF model are evidently reduced and the seasonal and sub-seasonal variations of the monsoon precipitation are remarkably improved.

Yang, Ben; Zhang, Yaocun; Qian, Yun; Huang, Anning; Yan, Huiping

2014-03-01

117

Observed Climate Properties of Tropical Precipitating Convection  

NASA Technical Reports Server (NTRS)

Conflicting theories about the contribution of convective systems to cloud feedback highlight the need for observational constraints on the properties of these storms. The NASA Tropical Rainfall Measuring Mission (TRMM) satellite provides unprecedented information on the hydrological properties and energetics of tropical convection. We present an analysis of almost 9,000 TRMM storms, focusing on how convection strength affects storm cloud properties and rainfall, and what this implies for the opposing "adaptive iris" and "thermostat" hypotheses.

DelGenio, Anthony

2002-01-01

118

Climatology of summer midtropospheric perturbations in the U.S. northern plains. Part I: Influence on northwest flow severe weather outbreaks  

SciTech Connect

Northwest flow severe weather outbreaks (NWF outbreaks) describe a type of summer convective storm that occurs in areas of mid-level NWF in the central United States. Convective storms associated with NWF outbreaks are often progressive (i.e. traveling a long distance) along systematic, northwestsoutheast oriented tracks throughout the northern plains. Previous studies have observed that progressive convective storms under NWF are often coupled with subsynoptic-scale midtropospheric perturbations (MPs) coming from the Rocky Mountains. This study traces such MPs for the decade of 1997-2006 using the North American Regional Reanalysis to examine their climatology and possible influence on NWF outbreaks. MPs initiated over the Rocky Mountains have a maximum frequency in July when the North American anticyclone fully develops and forms prevailing NWF over the northern plains. MPs developed under this anticyclone appear restricted in their vertical extension. Nevertheless, persistent upward motion is apparent in the leading edge (east) of MPs soon after their genesis subsequently inducing or intensifying convective storms. MPs propagate along systematic tracks similar to those of NWF outbreaks. The propagation of MPs also synchronizes with the progressive behavior of the associated convective storms. When encountering strong low-level jets (LLJs), upward motion and convergence of water vapor flux associated with MPs intensify substantially, resulting in strongly enhanced convection and precipitation. Convective wind and hail frequencies associated with MPs in strong LLJs reveal a pattern and magnitude very similar to that of NWF outbreaks. While about 60% of summer rainfall in the northern plains is linked to MPs, 75% of these instances occur in strong LLJs.

Wang, Shih-Yu; Chen, Tsing-Chang; Correia, James

2011-02-13

119

Winter Storms  

NSDL National Science Digital Library

This site offers general background about winter storms as well as interactive activities to teach visitors about these storms. It also offers a teacher's guide to using this site and links to other weather-related pages. There are four main topics: All About Winter Storms, Interactive Weather Maker, Interactive Winter Storm Timeline, and Ask Our Winter Storm Expert. All About Winter Storms gives general background information an a glossary of weather terms. The Weather Maker offers students a chance to control the weather through a simulation in which they affect the weather by changing variables such as humidity, equatorward temperature, and polarward temperature. The Storm Timeline offers students a chance to move up and down the timeline to learn about past winter storms. In Ask the Expert, students can email their questions to a winter storm expert and have them answered. This section also gives a brief biography of the expert.

1996-01-01

120

Storm Prediction Center  

NSDL National Science Digital Library

The Storm Prediction Center (SPC) is an agency of the National Oceanic and Atmospheric Administration (NOAA) National Weather Service. Materials available on the website include current weather watches, mesoscale discussions, convective outlooks, six-hour thunderstorm outlooks, and fire weather forecasts; research publications, experimental products and techniques; weather information including watch/warning maps, climatological data, and current radar; and a section on tornadoes. There is also an archive of weather images, and sections on the organization and history of the Center.

121

The Role of Convection in Redistributing Formaldehyde to the Upper Troposphere Over North America and the North Atlantic during the Summer 2004 INTEX Campaign  

NASA Technical Reports Server (NTRS)

Measurements of CH2O from a tunable diode laser absorption spectrometer (TDLAS) were acquired onboard the NASA DC-8 during the summer 2004 INTEX-NA (Intercontinental Chemical Transport Experiment - North America) campaign to test our understanding of convection and production mechanisms in the upper troposphere (UT, 6-12-km) over continental North America and the North Atlantic Ocean. Point-by-point comparisons with box model calculations, when MHP (CH3OOH) measurements were available for model constraint, resulted in a median CH2O measurement/model ratio of 0.91 in the UT. Multiple tracers were used to arrive at a set of UT CH2O background and perturbed air mass periods, and 46% of the TDLAS measurements fell within the latter category. At least 66% to 73% of these elevated UT observations were caused by enhanced production from CH2O precursors rather than direct transport of CH2O from the boundary layer. This distinction is important, since the effects from the former can last for over a week or more compared to one day or less in the case of convective transport of CH2O itself. In general, production of CH2O from CH4 was found to be the dominant source term, even in perturbed air masses. This was followed by production from MHP, methanol, PAN type compounds, and ketones, in descending order of their contribution. In the presence of elevated NO from lightning and potentially from the stratosphere, there was a definite trend in the CH2O discrepancy, which for the highest NO mixing ratios produced a median CH2O measurement/model ratio of 3.9 in the 10-12-km range. Discrepancies in CH2O and HO2 in the UT with NO were highly correlated and this provided further information as to the possible mechanism(s) responsible. These discrepancies with NO are consistent with additional production sources of both gases involving CH3O2 + NO reactions, most likely caused by unmeasured hydrocarbons.

Fried, Alan; Olson, Jennifer R.; Walega, Jim; Crawford, Jim H.; Chen, Gao; Weibring, Petter; Richter, Dirk; Roller, Chad; Tittel, Frank; Porter, Michael; Fuelberg, Henry; Halland, Jeremy; Bertram, Timothy H.; Cohen, Ronald C.; Pickering, Kenneth; Heikes, Brian G.

2007-01-01

122

Variability of the TRMM-PR total and convective and stratiform rain fractions over the Indian region during the summer monsoon  

NASA Astrophysics Data System (ADS)

Level 3 (3A25) TRMM Precipitation Radar (PR) data are used for 13 years period (1998-2010) to prepare climatology of TRMM PR derived near surface rain (Total rain) and rain fractions for the 4-months duration of Indian Summer Monsoon season (June-September) as well as for individual months. It is found that the total rain is contributed mostly (99 %) by two rain fractions i.e. stratiform and convective rain fractions for the season as well as on the monthly basis. It is also found that total rain estimates by PR are about 65 % of the gauge measured rain over continental India as well as on sub-regional basis. Inter-annual variability of TRMM-PR rain estimates for India mainland and its sub-regions as well as over the neighboring oceanic regions, in terms of coefficient of variability (CV) is discussed. The heaviest rain region over north Bay of Bengal (BoB) is found to have the lowest CV. Another sub-region of low CV lies over the eastern equatorial Indian ocean (EEIO). The CVs of total rain as well as its two major constituents are found to be higher on monthly basis compared to seasonal basis. Existence of a well known dipole between the EEIO and the north BoB is well recognized in PR data also. Significant variation in PR rainfall is found over continental India between excess and deficit monsoon seasons as well as between excess and deficit rainfall months of July and August. Examination of rainfall fractions between the BoB and Central India on year to year basis shows that compensation in rainfall fractions exists on monthly scale on both the regions. Also on the seasonal and monthly scales, compensation is observed in extreme monsoon seasons between the two regions. However, much less compensation is observed between the north BoB and EEIO belts in extreme rain months. This leads to speculation that the deficit and excess seasons over India may result from slight shift of the rainfall from Central India to the neighboring oceanic regions of north BoB. Contribution of stratiform and convective rain fractions have been also examined and the two fractions are found to contribute almost equally to the total rain. Results are further discussed in terms of the possible impact of the two rain fractions on circulation based on possible difference is vertical profiles of latent heat of two types of rain. Substantial differences in the lower and upper tropospheric circulation regimes are noticed in both deficit and excess monsoon months/seasons, emphasizing the interaction between rainfall (latent heat) and circulation.

Pokhrel, Samir; Sikka, D. R.

2013-07-01

123

Multilinear approach to the precipitation-lightning relationship: a case study of summer local electrical storms in the northern part of Spain during 2002-2009 period  

NASA Astrophysics Data System (ADS)

Storms developed under local instability conditions are studied in the Spanish Basque region with the aim of establishing precipitation-lightning relationships. Those situations may produce, in some cases, flash flood. Data used correspond to daily rain depth (mm) and the number of CG flashes in the area. Rain and lightning are found to be weakly correlated on a daily basis, a fact that seems related to the existence of opposite gradients in their geographical distribution. Rain anomalies, defined as the difference between observed and estimated rain depth based on CG flashes, are analysed by PCA method. Results show a first EOF explaining 50% of the variability that linearly relates the rain anomalies observed each day and that confirms their spatial structure. Based on those results, a multilinear expression has been developed to estimate the rain accumulated daily in the network based on the CG flashes registered in the area. Moreover, accumulates and maximum values of rain are found to be strongly correlated, therefore making the multilinear expression a useful tool to estimate maximum precipitation during those kind of storms.

Herrero, I.; Ezcurra, A.; Areitio, J.; Diaz-Argandoña, J.; Ibarra-Berastegi, G.; Saenz, J.

2013-11-01

124

High-Resolution Modeling of the Predictability of Convective Systems, and Influences by Absorbing Aerosols Over Northern India and the Himalayas Foothills During Boreal Summer  

NASA Technical Reports Server (NTRS)

The Himalayas foothills region (HFR) is an important component of the South Asian monsoon. To the south, the HFR borders the fertile, populous, and heavily polluted Indo-Gangetic Plain (IGP). To the north, it rises to great height (approx. 4-5 km) to the Tibetan Plateau over a distance of less than 100 km. The HFR itself consists of complex mountainous terrain, with strong orographic forcing for precipitation. During the late spring and early summer, dust aerosol from the Thar and Middle East deserts , as well as moisture from the Arabian Sea were transported to the western part of the western part of the IGP and foothills spurs pre-monsoon severe thunderstorm over the region. During the monsoon season (mid June -August) convection from the Bay of Bengal, spread along the foothills northwestward to northern Pakistan. Recent climate model studies and preliminary observations have indicted not only the importance of dynamical forcing of precipitation in the HFR, but also possible strong impacts by the dense aerosols, from both local sources, and remote transport, that blanket the IGP from late spring up to the onset of the monsoon in June, and during monsoon breaks in July. In this work, we use the NASA Unified Weather Research and Forecasting (Nu-WRF) model to study the predictability ( 1-7 days) South Asian monsoon rainfall system. Results of 7 -day forecast experiments using an embedded domain of 27 km and 9 km resolution were conducted for the period June 11- July 15, 2008, with and without aerosol forcing are carried out to assess the intrinsic predictability of rainfall over the HFR, and possible impacts by aerosol direct effect, and possible connection of large-scale South Asian monsoon system.

Kim, Kyu-Myong; Lau, William K.-M.; Tao, Wei-Kuo; Shi, Jainn; Tan, Qian; Chin, Mian; Matsui, Toshihisa; Bian, Huisheng

2011-01-01

125

Daytime identification of summer hailstorm cells from MSG data  

NASA Astrophysics Data System (ADS)

Identifying deep convection is of paramount importance, as it may be associated with extreme weather phenomena that have significant impact on the environment, property and populations. A new method, the hail detection tool (HDT), is described for identifying hail-bearing storms using multispectral Meteosat Second Generation (MSG) data. HDT was conceived as a two-phase method, in which the first step is the convective mask (CM) algorithm devised for detection of deep convection, and the second a hail mask algorithm (HM) for the identification of hail-bearing clouds among cumulonimbus systems detected by CM. Both CM and HM are based on logistic regression models trained with multispectral MSG data sets comprised of summer convective events in the middle Ebro Valley (Spain) between 2006 and 2010, and detected by the RGB (red-green-blue) visualization technique (CM) or C-band weather radar system of the University of León. By means of the logistic regression approach, the probability of identifying a cumulonimbus event with CM or a hail event with HM are computed by exploiting a proper selection of MSG wavelengths or their combination. A number of cloud physical properties (liquid water path, optical thickness and effective cloud drop radius) were used to physically interpret results of statistical models from a meteorological perspective, using a method based on these "ingredients". Finally, the HDT was applied to a new validation sample consisting of events during summer 2011. The overall probability of detection was 76.9 % and the false alarm ratio 16.7 %.

Merino, A.; López, L.; Sánchez, J. L.; García-Ortega, E.; Cattani, E.; Levizzani, V.

2014-04-01

126

Remote sensing of tornadic storms from space  

NASA Technical Reports Server (NTRS)

By using infrared images obtained from GOES satellite, the digital count values of pixels representing blackbody temperatures of the cloud top, convective storms are observed throughout their life cycles. Clouds associated with a tornadic storm are compared with those without a tornadic storm to illustrate how the infrared and visible observations from a geosynchronous satellite can be used to study the differences in their life cycles.

Hung, R. J.; Smith, R. E.

1982-01-01

127

Magnetospheric Storms at Saturn  

NASA Astrophysics Data System (ADS)

The Ion and Neutral Camera (INCA) on board the Cassini mission images magnetospheric proton and O+ distributions in the ~10-300 keV range in the Saturnian magnetosphere. The most outstanding feature of the global energetic ion distributions is the occurrence of gradual increases (~1 d) on the nightside of Saturn, followed by corotation lasting several days of a localized distribution. We have studied the interplanetary magnetic field (IMF) obtained from the Cassini Magnetic Field Experiment (MFE), and solar wind speed obtained from the Cassini Charge Energy Mass Spectrometer (CHEMS), when Cassini was outside the magnetosphere. Through comparisons with the dynamics and morphology of the global energetic ion distributions obtained by INCA images, we find a behavior that resembles the global behavior of the terrestrial ring current during geomagnetic storms observed by the High Energy Neutral Atom imager on board the IMAGE mission: Gradual increases on the nightside at Saturn appear to be related to conditions that lead to high convection (northward IMF and high solar-wind speed) - the storm mainphase. At Earth, such periods correspond to strong magnetospheric convection and a small Alfven layer, so that hot plasma is convected from the tail sunward to the nightside, where particle distributions reach their highest intensity (partial ring current). The sudden transition to a localized distribution corotating with a period about the same as the periodicity determined from Saturn Kilometric Radiation (SKR) measurements, appears to be related to changes in the solar wind leading to decreased convection (southward IMF and lower solar wind speed) - the storm recovery phase. At Earth, such periods correspond to weak magnetospheric convection and a larger Alfven layer enclosing the previously convection-dominated plasma so that the region becomes dominated by magnetic drifts (corotation dominated at Saturn). We study two periods, 2-4 December, 2004 and 2-7 January, 2005, and investigate what the similarities and differences to global signatures of terrestrial storms are. We will put our results into context with similar studies of solar wind driving of auroral activity on Saturn ( Cowley, Bunce, Crary and others), which advocate that magnetospheric activity at Saturn is mostly controlled by solar wind pressure and less by the polarity of the IMF.

Brandt, P. C.; Mitchell, D. G.; Hill, M. E.; Mauk, B. H.; Paranicas, C. J.; Roelof, E. C.; Krimigis, S. M.

2005-12-01

128

Tropical storm structure revealed by stereoscopic photographs from Skylab  

Microsoft Academic Search

A stereo pair of photographs taken by Skylab astronauts over Hurricane Ellen, September 19, 1973, resulted in the first stereo analysis over tropical storms. This pair is also the first evidence to indicate the existence of ``supercell'' convection in developing tropical storms. The photos are analyzed to determine the cloud top structure of the intense convection occurring in one quadrant

P. G. Black

1982-01-01

129

Polarimetric and Multi-Doppler Radar Observations of Sprite-producing Storms  

NASA Technical Reports Server (NTRS)

Sprites are caused by luminous electrical breakdown of the upper atmosphere, and frequently occur over large mesoscale precipitation systems. Two sprite-producing storms (on 8 and 25 June) were observed in Colorado during the summer of 2012. Unlike most past studies of sprites, these storms were observed by a polarimetric radar - the CSU-CHILL facility - which provided both PPI and RHI scans of the cases. Also available were multiple-Doppler syntheses from CSU-CHILL, local NEXRAD radars, and the CSU-Pawnee radar; as well as data from the Colorado Lightning Mapping Array (COLMA), high speed cameras, and other lightning-detection instrumentation. This unique dataset provided an unprecedented look at the detailed kinematic and microphysical structures of the thunderstorms as they produced sprites, including electrical alignment signatures in the immediate location of the charge layers neutralized by sprite-parent positive cloud-to-ground lightning strokes. One of the sprite-producing cases (25 June) featured an anomalous charge structure and may serve as a model for how sprites can be produced over convection rather than the more typical stratiform regions. Also to be presented will be evidence for advection of charge into a common stratiform precipitation region (on 8 June), which was then tapped by lightning originating from multiple different convective cores to produce sprites. Depending on the outcome of the 2013 convective season, polarimetric data from additional storms that produce sprites and other transient luminous events (TLEs) may be presented.

Lang, TImothy J.; Lyons, Walter A.; Rutledge, Steven A.; Dolan, Brenda; Cummer, Steven A.; Krehbiel, Paul; Rison, William

2014-01-01

130

Estimating probable maximum precipitation using a storm model approach  

Microsoft Academic Search

An approach to estimating probable maximum precipitation (PMP) using a simple, totally objective, storm model of convective systems is outlined. PMP hyetographs are compared with observations for severe events, and the variation of storm model PMP with storm duration is compared with PMP values derived using the UK Flood Studies Report (FSR) (NERC, 1975, Department of the Environment, London) approach.

C. G. Collier; P. J. Hardaker

1996-01-01

131

Deep winds beneath Saturn's upper clouds from a seasonal long-lived planetary-scale storm  

Microsoft Academic Search

Convective storms occur regularly in Saturn's atmosphere. Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years). Current models propose that the outbreak of a Great White Spot is due to moist convection induced by water. However, the generation of the global

A. Sánchez-Lavega; T. del Río-Gaztelurrutia; R. Hueso; J. M. Gómez-Forrellad; J. F. Sanz-Requena; J. Legarreta; E. García-Melendo; F. Colas; J. Lecacheux; L. N. Fletcher; D. Barrado y Navascués; D. Parker; T. Akutsu; T. Barry; J. Beltran; S. Buda; B. Combs; F. Carvalho; P. Casquinha; M. Delcroix; S. Ghomizadeh; C. Go; J. Hotershall; T. Ikemura; G. Jolly; A. Kazemoto; T. Kumamori; M. Lecompte; P. Maxson; F. J. Melillo; D. P. Milika; E. Morales; D. Peach; J. Phillips; J. J. Poupeau; J. Sussenbach; G. Walker; S. Walker; T. Tranter; A. Wesley; T. Wilson; K. Yunoki

2011-01-01

132

Total Storm Currents in Relation to Storm Type and Lifecycle  

NASA Astrophysics Data System (ADS)

Electrified lightning and non-lightning producing clouds of various types are thought to play a major role in supplying current to the global electric circuit (GEC). However, the contribution of storm conduction currents of different cloud types to the GEC is still not entirely known. Estimates of storm total conduction currents for different electrified clouds for the general categories of oceanic and continental electrified clouds were recently estimated from data collected over two decades during multiple field campaigns involving the NASA ER-2 and Altus-II aircraft. Building on this previous work, in this study we differentiate cloud categories into more specific cloud types (e.g. convective and stratiform partitions, severe versus ordinary single cell storms) and investigate on a case by case basis their underlying microphysical and dynamical structure. We also investigate the temporal evolution of storm total conduction currents during the lifecycle of electrified clouds.

Deierling, W.; Kalb, C. P.; Mach, D. M.; Liu, C.

2013-12-01

133

Hail Storms  

NSDL National Science Digital Library

This website contains photos and information about hail and hail storms as a weather phenomenon. The images show hail stones, storms with falling hail, cloud formations, and damage from hail. Each photo has a description with information about the weather system and occurrence of hail.

Moore, Gene

134

Regional scale flood modeling using NEXRAD rainfall, GIS, and HEC-HMS/RAS: a case study for the San Antonio River Basin Summer 2002 storm event.  

PubMed

This paper develops a framework for regional scale flood modeling that integrates NEXRAD Level III rainfall, GIS, and a hydrological model (HEC-HMS/RAS). The San Antonio River Basin (about 4000 square miles, 10,000 km2) in Central Texas, USA, is the domain of the study because it is a region subject to frequent occurrences of severe flash flooding. A major flood in the summer of 2002 is chosen as a case to examine the modeling framework. The model consists of a rainfall-runoff model (HEC-HMS) that converts precipitation excess to overland flow and channel runoff, as well as a hydraulic model (HEC-RAS) that models unsteady state flow through the river channel network based on the HEC-HMS-derived hydrographs. HEC-HMS is run on a 4 x 4 km grid in the domain, a resolution consistent with the resolution of NEXRAD rainfall taken from the local river authority. Watershed parameters are calibrated manually to produce a good simulation of discharge at 12 subbasins. With the calibrated discharge, HEC-RAS is capable of producing floodplain polygons that are comparable to the satellite imagery. The modeling framework presented in this study incorporates a portion of the recently developed GIS tool named Map to Map that has been created on a local scale and extends it to a regional scale. The results of this research will benefit future modeling efforts by providing a tool for hydrological forecasts of flooding on a regional scale. While designed for the San Antonio River Basin, this regional scale model may be used as a prototype for model applications in other areas of the country. PMID:15854726

Knebl, M R; Yang, Z-L; Hutchison, K; Maidment, D R

2005-06-01

135

August 28, 1978, Storm 1. GEOS 2 observations of the initial magnetopause crossings and STARE observations near the ionospheric convection reversal  

SciTech Connect

During the postdawn period on August 28, 1978, from approx.0750 to 0830 magnetic local time, the magnetopause moved several earth radii inward to less than 6.6 R/sub E/, where it remained until approx.1120 MLT. As the magnetopause approached the earth, the poleward boundary of the westward auroral electrojet moved southward to geomagnetic latitudes less than 66/sup 0/. Fortuitously, the geostationary satellite GEOS 2 was located in this morning sector during this entire period, and experienced a series of magnetopause crossings. In quiet periods GEOS 2 was conjugate to that area of the lower E region which constituted the field-of-view of the Scandinavian Twin Auroral Radar Experiment (STARE) radars. This paper compares the magnetospheric satellite and ionospheric radar observations. The combined observations suggest that, near the dawnside magnetopause, large-scale merging was occurring, while in the ionosphere, the convection reversal region and poleward portion of the auroral zone underwent major equatorward shifts and featured prominent sunward moving ULF pulsations. Between the magnetopause and ionosphere a large increase in the ring current accompanied the equatorward shift of the convection reversal.

Sofko, G.J.; Korth, A.; Kremser, G.

1985-02-01

136

Principles of Convection II: Using Hodographs  

NSDL National Science Digital Library

Part of the Mesoscale Meteorology Primer, this module provides a basic understanding of how to plot and interpret hodographs, with application to convective environments. Most of the material previously appeared in the CD module, A Convective Storm Matrix, developed with Dr. Morris Weisman. Principles of Convection II: Using Hodographs includes a concise summary for quick reference and a final exam to test your knowledge.

Spangler, Tim

2003-10-01

137

Magnetic Storms  

NSDL National Science Digital Library

This is a lesson to introduce the Kp index, a common numerical indicator of magnetic storminess. Learners will access and analyze Kp index plots of magnetic storm strength and determine the relative frequency of stronger versus weaker magnetic storms during years of maximum solar activity. This resource is activity 13 from the Magnetic Mysteries of the Aurora teachers guide. Internet access is required for this activity.

138

Gravity wave initiated convection  

NASA Technical Reports Server (NTRS)

The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.

Hung, R. J.

1990-01-01

139

Day-time identification of summer hailstorm cells from MSG data  

NASA Astrophysics Data System (ADS)

Identifying deep convection is of paramount importance, as it may be associated with extreme weather that has significant impact on the environment, property and the population. A new method, the Hail Detection Tool (HDT), is described for identifying hail-bearing storms using multi-spectral Meteosat Second Generation (MSG) data. HDT was conceived as a two-phase method, in which the first step is the Convective Mask (CM) algorithm devised for detection of deep convection, and the second a Hail Detection algorithm (HD) for the identification of hail-bearing clouds among cumulonimbus systems detected by CM. Both CM and HD are based on logistic regression models trained with multi-spectral MSG data-sets comprised of summer convective events in the middle Ebro Valley between 2006-2010, and detected by the RGB visualization technique (CM) or C-band weather radar system of the University of León. By means of the logistic regression approach, the probability of identifying a cumulonimbus event with CM or a hail event with HD are computed by exploiting a proper selection of MSG wavelengths or their combination. A number of cloud physical properties (liquid water path, optical thickness and effective cloud drop radius) were used to physically interpret results of statistical models from a meteorological perspective, using a method based on these "ingredients." Finally, the HDT was applied to a new validation sample consisting of events during summer 2011. The overall Probability of Detection (POD) was 76.9% and False Alarm Ratio 16.7%.

Merino, A.; López, L.; Sánchez, J. L.; García-Ortega, E.; Cattani, E.; Levizzani, V.

2013-10-01

140

Storm morphology and electrification from CHUVA-GLM Vale do Paraiba field campaign  

NASA Astrophysics Data System (ADS)

CHUVA [Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GPM (GlobAl Precipitation Measurement)] Project is a series of itinerant field campaigns with the objective of characterizing the main precipitating systems observed in Brazil as a support for Global Precipitation Measurement (GPM) mission. The fourth field campaign was conducted at Vale do Paraiba in São Paulo, Brazil, from 1 November 2011 to 31 March 2012. For this specific field experiment, several lightning location systems (LLS) were deployed as part of GOES-R Geostationary Lightning Mapper (GLM) and MTG Lightning Imager (LI) pre-launch activities, resulting in a joint effort between INPE, USP, NOAA, NASA, EUMETSAT and several vendors of operational LLS for network intercomparison and GLM and LI proxy data generation. Among these networks, 4 of them detect total (intra-cloud and cloud-to-ground) lightning, including a Lightning Mapping Array (LMA), allowing a detailed description of the cloud electrification. To depict precipitating weather systems, CHUVA uses a mobile XPOL Doppler Radar, micro-rain radars, disdrometers, rain gauges, microwave radiometer, Lidar, and a GPS network for water vapor retrievals. Also, Vale do Paraíba and São Paulo are covered by 3 operational S-band radars. The precipitation data collected by these radars and the lightning detected by the LLS were grouped in a structure of storm features built by tracking the precipitating systems and its associated lightning. This storm feature database makes it easier to group similar convective systems and compare them in terms of area, lifetime, rainfall and convection intensity, lightning activity, and more. During this field experiment a large variety of cloud systems were sampled: cold fronts, squall lines, the South Atlantic Convergence Zone (SACZ) and local convective systems. Microphysical characteristics (such as hydrometeor identification and ice/water mass) of these summer 2011-2012 precipitating systems can be inferred from the X-Pol and 3 operational S-band radars, and the LLS provide detailed information about the storms electrical activity (such as charge centers and lighting propagation processes). We will summarize the results from this experiment providing an in-depth study of the relationship between the storm type and its microphysical-electrical characteristics by presenting the role of storm morphology on cloud electrification, rainfall and severe weather (hail and damaging winds) production. Also, this storm feature database will provide an easy access to CHUVA data for case studies and GLM and LI activities.

Albrecht, R. I.; Morales, C.; Lima, W. F.; Biscaro, T. S.; Mello, I. B.

2013-12-01

141

Metal Storm  

NSDL National Science Digital Library

The National Institute of Justice (NIJ) is exploring a unique application of biometrics technologies: a handgun that can recognize its owner and only fire when being held by that person. This innovation could make it impossible for a criminal to steal an officer's firearm and use it against other people. Metal Storm, the company that is working with the NIJ to develop the gun, has presentations and technology descriptions on its home page.

142

Severe dust storms over the Arabian Peninsula: Observations and modeling  

NASA Astrophysics Data System (ADS)

Dust aerosols and dust storms have tremendous effects on human health and all development activities. Also atmospheric dust plays a major role in the Earth climate system by its interaction with radiation and clouds. Severe dust storms are considered the severest phenomena in the Arabian Peninsula, since they are occurring all the year round with maximum activity and frequency in Summer. The Regional Climate Model (RegCM4) has been used to simulate severe dust storms events in the Arabian Peninsula from 1998 up to 2011. This long period simulation shows a typical pattern and dynamical features of the large-scale severe dust storm in winter seasons and summer seasons. The Aerosol Optical Depth (AOD) from the model outputs have been compared against ground--base observations of three AERONET stations (i.e., Kuwait, Mazeria and Solar-Village) and daily space--based observations of MISR, Deepblue and OMI. The dynamical analysis of the large—scale severe dust storms reveal the difference between winter time storms and summer time storm. Winter time storm occurs when the cold air front in the north is coupled with the extension of the Red Sea trough from the south. However, the summer time storm is associated with strong Shamal wind that extend from northern Kuwait to the southern Arabian Peninsula.

shalaby, ahmed

2014-05-01

143

A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part II: Simulations of Convective Storms in Different Large-Scale Environments and Comparisons with other Bulk Parameterizations.  

NASA Astrophysics Data System (ADS)

Part I of this study described a detailed four-class bulk ice scheme (4ICE) developed to simulate the hydro-meteor profiles of convective and stratiform precipitation associated with mesoscale convective systems. In Part II, the 4ICE scheme is incorporated into the Goddard Cumulus Ensemble (GCE) model and applied without any `tuning' to two squall lines occurring in widely different environments, namely, one over the `Pica) ocean in the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE) and the other over a midlatitude continent in the Cooperative Huntsville Meteorological Experiment (COHMEX). Comparisons were made both with earlier three-class ice formulations and with observations. In both cases, the 4ICE scheme interacted with the dynamics so as to resemble the observations much more closely than did the model runs with either of the three-class ice parameterizations. The following features were well simulated in the COHMEX case: a lack of stratiform rain at the surface ahead of the storm, reflectivity maxima near 60 dBZ in the vicinity of the melting level, and intense radar echoes up to near the tropopause. These features were in strong contrast with the GATE simulation, which showed extensive trailing stratiform precipitation containing a horizontally oriented radar bright band. Peak reflectivities were below the melting level, rarely exceeding 50 dBz, with a steady decrease in reflectivity with height above. With the other bulk formulations, the large stratiform rain areas were not reproduced in the GATE conditions.The microphysical structure of the model clouds in both environments were more realistic than that of earlier modeling efforts. Number concentrations of ice of O(100 L1) occurred above 6 km in the GATE model clouds as a result of ice enhancement and rime splintering in the 4ICE runs. These processes were more effective in the GATE simulation, because near the freezing level the weaker updrafts were comparable in magnitude to the fall speeds of newly frozen drops. Many of the ice crystals initiated at relatively warm temperatures (above 15°C) grew rapidly by deposition into sizes large enough to be converted to snow. In contrast, in the more intense COHMEX updrafts, very large numbers of small ice crystals were initiated at colder temperatures (below 15°C) by nucleation and stochastic freezing of droplets, such that relatively few ice crystals grew by deposition to sizes large enough to be converted to snow. In addition, the large number of frozen drops of O(5 L1) in the 4ICE run am consistent with airborne microphysical data in intense COHMEX updrafts.Numerous sensitivity experiments were made with the four-class and three-class ice schemes, varying fall speed relationships, particle characteristics, and ice collection efficiencies. These tests provide strong support to the conclusion that the 4ICE scheme gives improved resemblance to observations despite present uncertainties in a number of important microphysical parameters.

Schoenberg Ferrier, Brad; Tao, Wei-Kuo; Simpson, Joanne

1995-04-01

144

POCATELLO STORM DRAIN STUDY, BANNOCK COUNTY, IDAHO - 1979  

EPA Science Inventory

The City of Pocatello (17040208) storm drains were sampled during a winter snowmelt period and during a summer rainstorm. Chemical analyses of the drain water indicated levels of suspended solids, total solids, Chemical Oxygen Demand, sodium, potassium, chloride, fluoride, arsen...

145

Effect of season and synoptic storm type on precipitation chemistry  

SciTech Connect

For a two-year period, the chemistry of daily precipitation samples for a site in southern Indiana was analyzed for effect of seasons and synoptic storm types. The storms were classified as frontal, cyclonic, convective and other. Statistically significant (5 percent level) higher concentrations of sulfate, ammonium and hydrogen ion and lower sodium occurred in the warm seasons (April-September) than in the cold (October-March); nitrate, chloride and calcium concentrations were similar in both seasons. In general, convective and frontal storms contained the highest concentrations of ions, and cyclonic and other the lowest. Frontal storms showed significant higher sulfate, nitrate, ammonium and hydrogen ion and lower sodium in warm seasons than in cold, while cyclonic storms yielded significant (1 percent level) higher nitrate in the cold seasons. These results are generally consistent with the well-known behavior of the meteorological weather system categories.

Topol, L.E.; Vijayakumar, R.; McKinley, C.M.; Waldron, T.L.

1986-04-01

146

Winter storms  

NSDL National Science Digital Library

This project explores factors that help create severe winter weather. An interactive simulation provides hands-on experience, followed by guiding questions and resource exploration. Weather affects our everyday lives. Some days it's sunny and some days its not. The years weather is split up into seasons. 1. What are the four seasons? 2. What kind of weather do you see in the summer? 3. What kind of weather is unique to winter? 4. ...

Brieanne

2011-02-14

147

Interactions of Cloud Microphysics and Dynamics Simulated in a PRE-STORM Squall Line Case  

NASA Astrophysics Data System (ADS)

The Goddard Cumulus Ensemble (GCE) Model is used to simulate the June 10-11, 1985 PRE-STORM squall line. The 2-D version of the GCE model initialized with a cool pool is integrated for 12 hours until the storm develops into a semi-steady state. It is found that, with all environmental conditions identical, the strength of the rain evaporation affects the steady state storm dynamics significantly. When the rain evaporation is weak, the negative vorticity generated by the surface cool pool nearly balances the positive vorticity of the ambient wind shear. The leading convective cell in this type of squall system is upright and tall. The air detrained from the leading convective cell loses most of its buoyancy. It brings the ice particles back to the stratiform region without developing any weak convective cells, producing uniform weak ascending and more homogeneous stratiform rain with a prominent bright band in the simulated radar reflectivity pattern. On the other hand, when the rain evaporation rate is strong, the cool pool is strong, too. The negative vorticity generated by the cool pool overpowers the ambient near surface positive vorticity. The resulted leading cell tilts downshear. The updraft in the leading cell is cut by the downdraft produced by rain evaporation. The remained buoyant air parcel continues to rise while moving into the stratiform region, forming weak convective cells in the stratiform region. The differences in evaporation strengths simulated in the GCE Model are produced by two self-consistent microphysical schemes, one is a bulk type, and the other is an explicit bin model. The assumption in the bulk scheme that the intercept of the raindrop size distribution is a fixed value results in stronger rain evaporations, especially in the downdraft cores. In a dry and unstable summer time mid-latitude environment, this produces significant differences in storm structure, rainfall pattern, and rain efficiencies. This study suggests that under certain circumstances, small differences in cloud microphysical processes may have comparable sensitivities as changing some of the environmental conditions. In addition to the rain evaporation, the terminal fall velocity of precipitable ice particles also plays an important role in shaping the stratiform rain in this squall line case. When the fall velocities of ice particles are reduced, significantly more stratiform rain is produced by the squall line. The wind and pressure patterns of the squall line changes accordingly, too.

Li, X.; Tao, W.; Khain, A.; Simpson, J.

2005-05-01

148

Initiation of deep convection along boundary layer convergence lines in a semitropical environment  

SciTech Connect

The initiation of deep convection through forcing along boundary layer convergence lines is examined using observations from the Convection and Precipitation/Electrification (CaPE) Experiment conducted in east-central Florida during the summer of 1991. The study is concerned with the evolution and interaction of two converging air masses that were initially separated by an intervening boundary layer characterized by neutral stability and horizontal convective rolls. As anticipated, major thunderstorms erupt when the east coast breeze eventually collides with thunderstorm outflows from the west, but unexpected convection takes place prior to their merger along a well-defined confluence zone associated with a persistent quasi-stationary roll vortex signature. In this study, complementary interactions between roll vortex convergence lines and the sea-breeze front are not sufficient to trigger deep convection. However, organized convergence along the eastward-spreading thunderstorm outflows did interact periodically with roll vortex convergence maxima to initiate a new series of new storms. Results from two-dimensional numerical model simulations replicate many of the observed boundary layer features. Surface heating produces circulations similar to sea-breeze frontal zones that appear near the coastlines and progress steadily toward each other as the interior boundary layer deepens. Vertical velocity maxima develop over the associated convergence zones, but weaker periodic maxima also occur within the interior air mass at intervals similar to the spacing of observed horizontal roll vortices.

Fankhauser, J.C.; Crook, N.A.; Tuttle, J.; Miller, L.J.; Wade, C.G. [NCAR, Boulder, CO (United States)] [NCAR, Boulder, CO (United States)

1995-02-01

149

Does Ice Matter? Heavy Rainfall from Warm and Mixed-phase Convection in COPE  

NASA Astrophysics Data System (ADS)

The COnvective Precipitation E experiment (COPE), which took place over the southwestern peninsula of the UK in Summer 2013, was motivated by a number of convective storms that produced flash flooding, chief among them the Boscastle flood event of 2004. Cloud tops during the Boscastle flood reached temperatures of -15 to -20 °C. Coupled with possible seeding from aloft, it was reasonable to presume that ice processes played an important role in precipitation formation. Some heavy precipitation events were sampled by the suite of ground-based and airborne instruments assembled for COPE, despite the unusually warm and dry weather in the UK at that time. Convective cells during several of these events had tops below the freezing level, or not far above where no ice was observed by the aircraft. Impressively, heavy rainfall was observed at the ground-based X-band radar with reflectivities frequently exceedeeding +60 dBZ. Here we use new in situ observations from the University of Wyoming King Air and the Wyoming Cloud Radar to corroborate reflectivity from the ground-based X-band radar. These observations, along with atmospheric soundings and calculations from a 1D warm rain model, are also utilized to understand the dynamic, thermodynamic and microphysical structure of these heavily precipitating convective cells. These observations lead us to question the prevalent assumption that ice processes are critical to the production of heavy convective precipitation.

Leon, David.; Lasher-Trapp, Sonia; French, Jeffrey; Blyth, Alan; Bennett, Lindsay; Brown, Phil

2014-05-01

150

Storm diagnostic/predictive images derived from a combination of lightning and satellite imagery  

NASA Technical Reports Server (NTRS)

A technique is presented for generating trend or convective tendency images using a combination of GOES satellite imagery and cloud-to-ground lightning observations. The convective tendency images can be used for short term forecasting of storm development. A conceptual model of cloud electrical development and an example of the methodology used to generate lightning/satellite convective tendency imagery are given. Successive convective tendency images can be looped or animated to show the previous growth or decay of thunderstorms and their associated lighting activity. It is suggested that the convective tendency image may also be used to indicate potential microburst producing storms.

Goodman, Steven J.; Buechler, Dennis E.; Meyer, Paul J.

1988-01-01

151

Hydrochemical response during storm events in a South African mountain catchment: the influence of antecedent conditions  

Microsoft Academic Search

The influence of different antecedent conditions on hydrochemical response during storm events was investigated in a small, south-western Cape mountain catchment. Winter and summer storms (four in total) were sampled both before and after the catchment was deliberately burnt. During winter storms, discharge responded rapidly to rainfall, and direct runoff represented the major component of streamflow. Marked lags were observed

D. L. Britton; J. A. Day; M.-P. Henshall-Howard

1993-01-01

152

Anvil and Convective Lightning: A TRMM Perspective  

NASA Astrophysics Data System (ADS)

Twelve years of TRMM observations in the tropics and extra-tropics up to 36 degrees latitude in the University of Utah’s TRMM Precipitation Feature database are used to investigate lightning-producing convective cells from both a climatological and case study perspective. Of particular interest are convective cells capable of producing large numbers of anvil and stratiform lightning. Lightning flashes from TRMM Lightning Imaging System (LIS) are categorized into anvil, stratiform and convective types based on the locations of the flashes relative to the convective cells defined by Precipitation Radar reflectivity profiles. Anvil and stratiform lightning were found to each account for roughly 6% of the total lightning flashes. Stratiform lightning was more common later in the day in expansive multi-cell systems, and tended to occur at a much greater distance from the storm’s convective center than other types. Moreover, anvil lightning was the most common type of lightning in single-cell storms, and those with a small number of cells and smaller cell area than the other types. Using the nearest neighbor method, a convective cell most likely associated with each lightning flash is identified. Analysis of the properties of the convective cells associated with anvil and stratiform lightning flashes and their correlations to the distance of flashes from the convective cell will be presented.

Peterson, M. J.; Liu, C.

2010-12-01

153

Rocket dust storms and detached layers in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

Airborne dust is the main climatic agent in the Martian environment. Local dust storms play a key role in the dust cycle; yet their life cycle is poorly known. Here we use mesoscale modeling with radiatively-active transported dust to predict the evolution of a local dust storm monitored by OMEGA onboard Mars Express. We show that the evolution of this dust storm is governed by deep convective motions. The supply of convective energy is provided by the absorption of incoming sunlight by dust particles, in lieu of latent heating in moist convection on Earth. We propose to use the terminology "rocket dust storm", or conio-cumulonimbus, to describe those storms in which rapid and efficient vertical transport takes place, injecting dust particles at high altitudes in the Martian troposphere (30 to 50 km). Combined to horizontal transport by large-scale winds, rocket dust storms form detached layers of dust reminiscent of those observed with instruments onboard Mars Global Surveyor and Mars Reconnaissance Orbiter. Detached layers are stable over several days owing to nighttime sedimentation being unable to counteract daytime convective transport, and to the resupply of convective energy at sunrise. The peak activity of rocket dust storms is expected in low-latitude regions at clear season, which accounts for the high-altitude tropical dust maximum unveiled by Mars Climate Sounder. Our findings on dust-driven deep convection have strong implications for the Martian dust cycle, thermal structure, atmospheric dynamics, cloud microphysics, chemistry, and robotic and human exploration.ensity-scaled dust optical depth at local times 1400 1600 and 1800 (lat 2.5°S, Ls 135°) hortwave heating rate at local time 1500 and latitude 2.5°S.

Spiga, A.; Faure, J.; Madeleine, J.; Maattanen, A. E.; Forget, F.

2012-12-01

154

Ongoing Studies of the Characteristics of Storms and Lightning Discharges Which Do and Do Not Produce Sprites  

NASA Astrophysics Data System (ADS)

Within a year after the first intentional ground and aircraft monitoring of sprites (1993), it had become apparent that this class of mesospheric transient luminous event was almost uniquely associated with positive polarity cloud-to-ground lightning strokes (+CGs). Yet not all +CGs, even those with high peak currents, produce sprites. Moreover, sprite parent +CGs (SP+CGs) tend to occur only in certain types of convective storm systems. On the U.S. High Plains, the SP+CGs are most common in the stratiform precipitation regions of mature mesoscale convective systems (MCSs) larger than 10-20x10**4 km**2. The summer 2000 Severe Thunderstorm Electrification and Precipitation Study (STEPS) produced the most complete database of coordinated low-light television (LLTV), 3-D lightning mapping array (LMA) and remote ELF transient data available to date. A major question is whether large charge moment changes are both a necessary and a sufficient condition for sprites? This presentation presents the results of a reanalysis of the STEPS database which, aided by ELF charge moment change estimates, has revealed substantially more events than in the original catalog. Particular attention is paid to charge moment changes in three major classes of storms, (1) MCSs with many SP+CGs in the stratiform region, (2) supercells with only sporadic sprite events during restricted portions of their life cycle, and (3) MCSs and supercell storms which, in spite of many +CGs, produce no transient luminous events. In addition, the characteristics of continuing currents in High Plains lightning discharges monitored using high speed video cameras (1000 fps) is compared with ELF/ULF measurements (Courtesy: Martin Fullekrug). Additional observations of sprites and elves were obtained during summer 2003, in conjunction with an upgraded Duke University ELF transient monitoring system. Some initial results will be presented.

Lyons, W. A.; Cummer, S. A.; Stanley, M. A.

2003-12-01

155

Research Opportunities at Storm Peak Laboratory  

NASA Astrophysics Data System (ADS)

The Desert Research Institute (DRI) operates a high elevation facility, Storm Peak Laboratory (SPL), located on the west summit of Mt. Werner in the Park Range near Steamboat Springs, Colorado at an elevation of 3210 m MSL (Borys and Wetzel, 1997). SPL provides an ideal location for long-term research on the interactions of atmospheric aerosol and gas- phase chemistry with cloud and natural radiation environments. The ridge-top location produces almost daily transition from free tropospheric to boundary layer air which occurs near midday in both summer and winter seasons. Long-term observations at SPL document the role of orographically induced mixing and convection on vertical pollutant transport and dispersion. During winter, SPL is above cloud base 25% of the time, providing a unique capability for studying aerosol-cloud interactions (Borys and Wetzel, 1997). A comprehensive set of continuous aerosol measurements was initiated at SPL in 2002. SPL includes an office-type laboratory room for computer and instrumentation setup with outside air ports and cable access to the roof deck, a cold room for precipitation and cloud rime ice sample handling and ice crystal microphotography, a 150 m2 roof deck area for outside sampling equipment, a full kitchen and two bunk rooms with sleeping space for nine persons. The laboratory is currently well equipped for aerosol and cloud measurements. Particles are sampled from an insulated, 15 cm diameter manifold within approximately 1 m of its horizontal entry point through an outside wall. The 4 m high vertical section outside the building is capped with an inverted can to exclude large particles.

Hallar, A. G.; McCubbin, I. B.

2006-12-01

156

The relative contributions of summer and cool-season precipitation to groundwater recharge, Spring Mountains, Nevada, USA  

USGS Publications Warehouse

A comparison of the stable-isotope signatures of spring waters, snow, snowmelt, summer (July thru September) rain, and cool season (October thru June) rain indicates that the high-intensity, short-duration summer convective storms, which contribute approximately a third of the annual precipitation to the Spring Mountains, provide only a small fraction (perhaps 10%) of the recharge to this major upland in southern Nevada, USA. Late spring snowmelt is the principal means of recharging the fractured Paleozoicage carbonate rocks comprising the central and highest portion of the Spring Mountains. Daily discharge measurements at Peak Spring Canyon Creek during the period 1978-94 show that snowpacks were greatly enhanced during E1 Nin??o events.

Winograd, I. J.; Riggs, A. C.; Coplen, T. B.

1998-01-01

157

3-Dimensional simulations of storm dynamics on Saturn  

NASA Astrophysics Data System (ADS)

The formation and evolution of convective clouds in the atmosphere of Saturn is investigated using an anelastic three-dimensional time-dependent model with parameterized microphysics. The model is designed to study the development of moist convection on any of the four giant planets and has been previously used to investigate the formation of water convective storms in the jovian atmosphere. The role of water and ammonia in moist convection is investigated with varying deep concentrations. Results imply that most of the convective activity observed at Saturn may occur at the ammonia cloud deck while the formation of water moist convection may happen only when very strong constraints on the lower troposphere are met. Ammonia storms can ascend to the 300 mb level with vertical velocities around 30 ms-1. The seasonal effect on the thermal profile at the upper troposphere may have important effects on the development of ammonia storms. In the cases where water storms can develop they span many scale heights with peak vertical velocities around 160 ms-1 and cloud particles can be transported up to the 150 mb level. These predicted characteristics are similar to the Great White Spots observed in Saturn which, therefore, could be originated at the water cloud base level. This work has been supported by Gobierno Vasco PI 1997-34. R. Hueso acknowledges a PhD fellowship from Gobierno Vasco.

Hueso, R.; Sanchez-Lavega, A.

2000-10-01

158

The Dynamics of Titan's Convective Clouds  

NASA Astrophysics Data System (ADS)

Titan's deep convective clouds are the most dynamic phenomena known to operate within the atmosphere of the moon. Previous studies have focused primarily on the control of these storms by the large scale thermodynamic environment, especially methane abundance, which determines the amount of convective available potential energy (CAPE). This study looks at factors in addition to the thermodynamic environment that may have a first order impact on the evolution and structure of Titan's deep convective clouds. To the extent that thunderstorms on Earth provide a reasonable analog to the storms on Titan, it is well established that CAPE alone is insufficient to determine the structure and behavior of deep convection. Wind shear—both directional and speed—is also known to exert a first order effect. The influence of both CAPE and wind speed shear is typically expressed as the ratio of the two parameters in the form of the Bulk Richardson Number. On Earth, for a fixed value of CAPE, the addition of wind speed shear (i.e., the reduction of the Bulk Richardson Number) will tend to produce storms that are longer lived, tilted upshear with height, and multi-cellular in nature. These multi-cellular storms also tend to be more violent than storms generated in low wind speed shear environments: strong winds and large hail are common. The addition of directional shear (i.e., helicity) can transform the multi-cell storms into single, intense supercell storms. These are the storms associated typically associated with tornadoes. With respect to Titan, if there is a similar dependence on the Bulk Richardson Number, then this would have implications for how long Titan's storms live, how much precipitation they can produce, the area they cover, and the strength and duration of winds. A series of numerical simulations of Titan's deep convective clouds from the Titan Regional Atmospheric Modeling System are presented. A reasonable sweep of the parameter space of CAPE and shear for Titan is used to quantify the dependence of Titan's storms on the same parameters known to affect deep convection on Earth. The results of the simulations and the implications for Titan are then discussed.imulated convection in a calm (left) and wind shear environment (right). Cloud mixing ratio (g/kg) is shaded. Winds are indicated by vectors with a reference in the lower right of each panel.

Rafkin, S. C.

2012-12-01

159

Temperature measurements of a Martian local dust storm  

NASA Technical Reports Server (NTRS)

A technique for estimating the ground and near-ground atmospheric temperatures within a Martian local dust storm is presented. It is applied to soundings taken by the Viking orbiter infrared thermal mapper (IRTM) instrument at four times-of-day for one storm. Essentially, a comparison is made between infrared radiances emerging from the storm interior and those from the region surrounding the storm. Particle extinction properties are assumed to be independent of position in the storm region, and scattering properties must be selected arbitrarily. For the storm studied here, the ground temperature in the interior is at least 6 K cooler, whereas the near-ground atmospheric temperature may be less than or comparable to, those of the surroundings. The thermal structure of the storm interior did not change measurably between 11.5 and 16.6 hours local time. These observations favor theories of dust storm development in which regional winds rather than local, dust-driven convection initiate the mobilization of dust from the surface. It is also concluded that the optical properties of dust particles in this local storm differ from those observed by Mariner 9 during the 1971-1972 global dust storm.

Kahn, Ralph

1995-01-01

160

Summer Swimtime: Staying Healthy at the Pool and Beach  

MedlinePLUS

... the water. But recreational waters—including swimming pools, lakes and oceans—can sometimes get contaminated with bacteria ... in your summer plans. Natural water sources, including lakes, rivers and oceans, often get contaminated from storm ...

161

Summer Astronomy  

ERIC Educational Resources Information Center

This brief article describes what can be expected of the skies in the summer of 2004 with quite a few celestial thrills to anticipate. In addition to the planet viewing opportunities, there is a very rare Venus transit of the Sun and the annual Perseid meteor shower. The 2004 summer also marks both an end and beginning for the Cassini/Huygens…

Riddle, Bob

2004-01-01

162

Lightning as an indication of storm severity  

NASA Technical Reports Server (NTRS)

There is a substantial case for the theory that cloud electrification is related primarily to strong convection and the sizeable relative air motion that it implies; therefore, the electrification and subsequent discharge rates can be related to the air motion environment of thunderstorms. The isoceraunic contour map used by the WMO for observing and measuring thunderstorm occurrence contains no information on flash rates, flash density, flash relationship to storm severity, or flash variation with meteorological environment. A constant-view geosynchronous lightning mapper would permit simultaneous studies of the lightning discharge patterns and the meteorological environment of storms, thus establishing whether or not there is a reliable enough relationship to use the observed flash rates and characteristics as supplemental guidance for storm forecast refinement.

Dodge, J. C.

1979-01-01

163

Mantle Convection  

NSDL National Science Digital Library

This page discusses thermal convection as it applies to the Earth's mantle and includes three QuickTime movies for three different cases of convection: heating from below, heating from within, and a combination of the two.

Schmeling, H.; Goethe Universitat, Facheinheit G.

164

The role of moist convection in the West African monsoon system: Insights from continental-scale convection-permitting simulations  

NASA Astrophysics Data System (ADS)

Predicting the West African monsoon (WAM) remains a major challenge for weather and climate models. We compare multiday continental-scale simulations of the WAM that explicitly resolve moist convection with simulations which parameterize convection. Simulations with the same grid spacing but differing representations of convection isolate the impact of the representation of convection. The more realistic explicit convection gives greater latent and radiative heating farther north, with latent heating later in the day. This weakens the Sahel-Sahara pressure gradient and the monsoon flow, delaying its diurnal cycle and changing interactions between the monsoon and boundary layer convection. In explicit runs, cold storm outflows provide a significant component of the monsoon flux. In an operational global model, biases resemble those in our parameterized case. Improved parameterizations of convection that better capture storm structures, their diurnal cycle, and rainfall intensities will therefore substantially improve predictions of the WAM and coupled aspects of the Earth system.

Marsham, John H.; Dixon, Nick S.; Garcia-Carreras, Luis; Lister, Grenville M. S.; Parker, Douglas J.; Knippertz, Peter; Birch, Cathryn E.

2013-05-01

165

Magnetic storms as a human infarction hazard: season effects  

NASA Astrophysics Data System (ADS)

There are a great number of clinical and statistical studies confirming that the myocardial infarction number rises during geomagnetic disturbances, which have a maximum of occurrence near equinox. Contrary to that, the analysis of the daily numbers of Moscow ambulance calls (1979-1981), related to the myocardial infarction, showed the strong winter maximum and summer minimum. The similar result we obtained by using the 25 year data (1970-1995) on the death from infarction in Bulgaria. We analyzed the biotropic efficacy of 129 geomagnetic storms and found that its hazard depends on the season. About of 90% of the winter time magnetic storms were accompanied by the infarction enhancement, but only ~ 3% of the summer magnetic storms led to the increasing of the cardiac problems. It means that the human organism stability to the "negative" influence of magnetic storms is stronger in summer than in winter. We also found that the different magnetic storm phases demonstrate the different hazard. As a rule, the storm main phase was not accompanied by the enhancement of the infarction number. However, the storm recovery phase typically leads to infarction increasing, particularly, if it was accompanied by the geomagnetic pulsation at periods of a few seconds.

Kleimenova, N.; Kozyreva, O.

2009-04-01

166

Report of convective phenomena team  

NASA Technical Reports Server (NTRS)

A group meeting was assembled to focus on the planning of specific experiments, to establish some priorities, identify interested scientists who would like to participate, establish any special requirements, make recommendations on data processing, and to prepare flight plan outlines. Since the number of convective storms in the CCOPE (Cooperative Convective Precipitation Experiment) field experiment area are limited to only a few days during the operational time period the flight plans must be designed with a hierarchy of abort experiments so that the easily identified and lowest probability events should take priority until their quota is filled.

Orville, H.; Koenig, R.; Miller, J.; Telford, J.; Jones, B.; Alger, G.; Lee, R.; Boudle, D.

1980-01-01

167

Convection initiation along a dryline under conditions of weak synoptic forcing  

NASA Astrophysics Data System (ADS)

During the spring and early summer a dryline characterized by relatively weak temperature (density) gradients but large moisture contrasts is a common feature over the southern Great Plains (SGP) region of the United States. In the spring, when strong vertical wind shear is present, the dryline often serves as a focus for severe convective storms. In the current study we examine a quasi-stationary dryline present over the SGP for a five-day period from 19 to 23 June 1998. In contrast to the more widely reported spring cases, this dryline episode and its associated deep convection occurred in the absence of strong vertical wind shear and organized synoptic-scale ascent. The detailed mechanisms of convection initiation along drylines are not well understood. The current case allows a unique opportunity for the assessment of planetary boundary layer (PBL)-based deep convection initiation mechanisms, which are likely to be of general importance in dryline convection cases, without the complicating effects of strong large-scale forcing. Numerical simulations with the Pennsylvania State/NCAR Mesoscale Model Version 5 (MM5), at both deep convection resolving resolutions and at coarser resolution over regional scale domains, have accurately reproduced the initiation and short term (3-6 h) evolution of deep convection, as revealed by satellite, radar, and surface rainfall observations. Convection initiation was both observed and simulated at the eastern edge of the dryline, which later retrogressed westward during the lifecycle of the slowly eastward moving convection. During the five-day episode there was little severe weather reported, however, localized heavy rainfall amounts were common in the large-CAPE environment along and slightly east of the dryline. Trajectory analysis with model output elucidates the thermodynamic destabilization of the PBL air that feeds the updrafts of the developing convection. Model-based sensitivity studies are planned to examine the role of land-surface atmosphere interactions (particularly the impact of soil moisture and temperature), which are likely to be especially important for convection initiation in the weakly forced synoptic environment. Results from this analysis will be discussed at the conference.

Trier, S.; Chen, F.; Manning, K.

2003-04-01

168

Regional analysis of convective systems during the West African monsoon  

NASA Astrophysics Data System (ADS)

The West African monsoon (WAM) occurs during the boreal summer and is responsible for a majority of precipitation in the northern portion of West Africa. A distinct shift of precipitation, often driven by large propagating mesoscale convective systems, is indicated from satellite observations. Excepting the coarser satellite observations, sparse data across the continent has prevented understanding of mesoscale variability of these important systems. The interaction between synoptic and mesoscale features appears to be an important part of the WAM system. Without an understanding of the mesoscale properties of precipitating systems, improved understanding of the feedback mechanism between spatial scales cannot be attained. Convective and microphysical characteristics of West African convective systems are explored using various observational data sets. Focus is directed toward meso -alpha and -beta scale convective systems to improve our understanding of characteristics at this spatial scale and contextualize their interaction with the larger-scale. Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger [continental], Kawsara, Senegal [coastal], and Praia, Republic of Cape Verde [maritime]) are analyzed to determine convective system characteristics in each domain during a 29 day period in 2006. Ancillary datasets provided by the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) field campaigns are also used to place the radar observations in context. Results show that the total precipitation is dominated by propagating mesoscale convective systems. Convective characteristics vary according to environmental properties, such as vertical shear, CAPE, and the degree of synoptic forcing. Data are bifurcated based on the presence or absence of African easterly waves. In general, African easterly waves appear to enhance mesoscale convective system strength characteristics (e.g. total precipitation and vertical reflectivity profiles) at the inland and maritime sites. The wave regime also resulted in an increased population of the largest observed mesoscale convective systems observed near the coast, which led to an increase in stratiform precipitation. Despite this increase, differentiation of convective strength characteristics was less obvious between wave and no-wave regimes at the coast. Due to the propagating nature of these advecting mesoscale convective systems, interaction with the regional thermodynamic and dynamic environment appears to result in more variability than enhancements due to the wave regime, independent of location. A 13-year (1998-2010) climatology of mesoscale convective characteristics associated with the West African monsoon are also investigated using precipitation radar and passive microwave data from the NASA Tropical Rainfall Measuring Mission satellite. Seven regions defined as continental northeast and northwest, southeast and southwest, coastal, and maritime north and south are compared to analyze zonal and meridional differences. Data are categorized according to identified African easterly wave (AEW) phase and when no wave is present. While some enhancements are observed in association with AEW regimes, regional differences were generally more apparent than wave vs. no-wave differences. Convective intensity metrics confirm that land-based systems exhibit stronger characteristics, such as higher storm top and maximum 30-dBZ heights and significant 85-GHz brightness temperature depressions. Continental systems also contain a lower fraction of points identified as stratiform. Results suggest that precipitation processes also varied depending upon region and AEW regime, with warm-rain processes more apparent over the ocean and the southwest continental region and ice-based microphysics more dominant over land, including mixed-phase processes. AEW regimes did show variability in stratiform fraction and ice and liquid water content, suggesting modulation of mesoscale characteristics possibly throug

Guy, Bradley Nicholas

169

Storms in Space  

NASA Astrophysics Data System (ADS)

Introduction; The cast of characters; Vignettes of the storm; 1. Two kinds of weather; 2. The saga of the storm; 3. Weather stations in space; 4. Lights in the night: the signature of the storm; 5. A walking tour of the magnetosphere; 6. The sun: where it all begins; 7. Nowcasting and forecasting storms in space; 8. Technology and the risks from storms in space; 9. A conversation with Joe Allen; 10. Manned exploration and space weather hazards; 11. The present and future of space weather forecasting; Mathematical appendix. A closer look; Glossary; Figure captions.

Freeman, John W.

2012-11-01

170

Vorticity imbalance and stability in relation to convection  

NASA Technical Reports Server (NTRS)

A complete synoptic-scale vorticity budget was related to convection storm development in the eastern two-thirds of the United States. The 3-h sounding interval permitted a study of time changes of the vorticity budget in areas of convective storms. Results of analyses revealed significant changes in values of terms in the vorticity equation at different stages of squall line development. Average budgets for all areas of convection indicate systematic imbalance in the terms in the vorticity equation. This imbalance resulted primarily from sub-grid scale processes. Potential instability in the lower troposphere was analyzed in relation to the development of convective activity. Instability was related to areas of convection; however, instability alone was inadequate for forecast purposes. Combinations of stability and terms in the vorticity equation in the form of indices succeeded in depicting areas of convection better than any one item separately.

Read, W. L.; Scoggins, J. R.

1977-01-01

171

Subtropical Storm Andrea  

NASA Technical Reports Server (NTRS)

The circling clouds of an intense low-pressure system sat off the southeast coast of the United States on May 8, 2007, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image. By the following morning, the storm developed enough to be classified as a subtropical storm, a storm that forms outside of the tropics, but has many of the characteristics--hurricane-force winds, driving rains, low pressure, and sometimes an eye--of a tropical storm. Although it arrived several weeks shy of the official start of the hurricane season (June 1), Subtropical Storm Andrea became the first named storm of the 2007 Atlantic hurricane season. The storm has the circular shape of a tropical cyclone in this image, but lacks the tight organization seen in more powerful storms. By May 9, the storm's winds reached 75 kilometers per hour (45 miles per hour), and the storm was not predicted to get any stronger, said the National Hurricane Center. Though Subtropical Storm Andrea was expected to remain offshore, its strong winds and high waves pummeled coastal states, prompting a tropical storm watch. The winds fueled wild fires (marked with red boxes) in Georgia and Florida. The wind-driven flames generated thick plumes of smoke that concentrated in a gray-brown mass over Tampa Bay, Florida. Unfortunately for Georgia and Florida, which are experiencing moderate to severe drought, Subtropical Storm Andrea was not predicted to bring significant rain to the region right away, according to reports on the Washington Post Website.

2007-01-01

172

Summer Modification  

NASA Technical Reports Server (NTRS)

5 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the outer edge of the south polar residual cap of Mars during southern summer. The variability in brightness across the image would not be as apparent had the data been acquired during late winter or spring, owing to the presence of seasonally deposited, carbon dioxide frost. Over the spring and into early summer, the seasonal carbon dioxide is removed through sublimation, and then the thicker, older accumulations of carbon dioxide -- deposited hundreds or thousands of years ago -- erodes. As this occurs, some surfaces become darker, either because they are roughened by erosion, contain dark material such as mineral dust, or both.

Location near: 86.9oS, 111.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

173

Characterizing Extreme Ionospheric Storms  

NASA Astrophysics Data System (ADS)

Ionospheric storms consist of disturbances of the upper atmosphere that generate regions of enhanced electron density typically lasting several hours. Depending upon the storm magnitude, gradients in electron density can sometimes become large and highly localized. The existence of such localized, dense irregularities is a major source of positioning error for users of the Global Positioning System (GPS). Consequently, satellite-based augmentation systems have been implemented to improve the accuracy and to ensure the integrity of user position estimates derived from GPS measurements. Large-scale irregularities generally do not pose a serious threat to estimate integrity as they can be readily detected by such systems. Of greater concern, however, are highly localized irregularities that interfere with the propagation of a signal detected by a user measurement but are poorly sampled by the receivers in the system network. The most challenging conditions have been found to arise following disturbances of large magnitude that occur only rarely over the course of a solar cycle. These extremely disturbed conditions exhibit behavior distinct from moderately disturbed conditions and, hence, have been designated "extreme storms". In this paper we examine and compare the behavior of the extreme ionospheric storms of solar cycle 23 (or, more precisely, extreme storms occurring between January 1, 2000, and December 31, 2008), as represented in maps of vertical total electron content. To identify these storms, we present a robust means of quantifying the regional magnitude of an ionospheric storm. Ionospheric storms are observed frequently to occur in conjunction with magnetic storms, i.e., periods of geophysical activity as measured by magnetometers. While various geomagnetic indices, such as the disturbance storm time (Dst) and the planetary Kp index, have long been used to rank the magnitudes of distinct magnetic storms, no comparable, generally recognized index exists for measuring ionospheric storm magnitudes. Since the level of ionospheric disturbance (as represented, for example, by enhancements or depletions in total electron content) does not always scale directly with the level of geophysical disturbance in a coincident magnetic storm, however, an independent, purely ionospheric storm index is preferable for ranking ionospheric storms by their magnitudes. Our storm magnitude metric is calculated from the standard ?2 goodness-of-fit parameter values associated with estimates of vertical total electron content (derived from observations collected by networks of GPS receivers) on a grid at regularly spaced intervals of geodetic latitude and longitude. It takes into account both the instantaneous magnitude of the storm and its temporal duration.

Sparks, L.; Komjathy, A.; Altshuler, E.

2011-12-01

174

Polar Summer  

NASA Technical Reports Server (NTRS)

6 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows south polar mesas composed largely of solid carbon dioxide separated by generally circular depressions. The arcuate scarps, which delineate the mesas, retreat approximately 3 meters per Mars year (two Earth years), owing to sublimation which occurs primarily during the martian summer months.

Location near: 86.9oS, 340.2oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

175

Spatial analysis of storm depths from an Arizona raingage network  

NASA Technical Reports Server (NTRS)

Eight years of summer rainstorm observations are analyzed by a dense network of 93 raingages operated by the U.S. Department of Agriculture, Agricultural Research Service, in the 150 km Walnut Gulch experimental catchment near Tucson, Arizona. Storms are defined by the total depths collected at each raingage during the noon-to-noon period for which there was depth recorded at any of the gages. For each of the resulting 428 storm days, the gage depths are interpolated onto a dense grid and the resulting random field analyzed to obtain moments, isohyetal plots, spatial correlation function, variance function, and the spatial distribution of storm depth.

Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodriguez-Iturbe, I.

1986-01-01

176

Large Eddy Simulations of Severe Convection Induced Turbulence  

NASA Technical Reports Server (NTRS)

Convective storms can pose a serious risk to aviation operations since they are often accompanied by turbulence, heavy rain, hail, icing, lightning, strong winds, and poor visibility. They can cause major delays in air traffic due to the re-routing of flights, and by disrupting operations at the airports in the vicinity of the storm system. In this study, the Terminal Area Simulation System is used to simulate five different convective events ranging from a mesoscale convective complex to isolated storms. The occurrence of convection induced turbulence is analyzed from these simulations. The validation of model results with the radar data and other observations is reported and an aircraft-centric turbulence hazard metric calculated for each case is discussed. The turbulence analysis showed that large pockets of significant turbulence hazard can be found in regions of low radar reflectivity. Moderate and severe turbulence was often found in building cumulus turrets and overshooting tops.

Ahmad, Nash'at; Proctor, Fred

2011-01-01

177

Tropical Storms, Worldwide  

NSDL National Science Digital Library

The University of Hawaii's Mees Solar Observatory, stationed at Haleakala, Maui, provides a wealth of data and images in its Webpages. This page, Tropical Storms Worldwide, gives regional maps and written updates of hurricane, typhoon, and tropical cyclone activity around the globe. The page also features a strike probability calculator where users click on a list of geographic locations or enter map coordinates or a US zip code in order to view the probability of a tropical storm reaching that area. A storm data archive (1994-2000) and printer-friendly .pdf-formatted storm track maps are also available.

1996-01-01

178

Remote Imaging of Storm-Phase Ion Heating  

NASA Astrophysics Data System (ADS)

The MENA (Medium Energy Neutral Atom) instrument onboard the IMAGE spacecraft allows for global imaging of the magnetosphere in neutral atoms with energies ranging from 1 to 60 keV. Using known charge exchange cross sections and the properties of the instrument, the measured neutral atom energy spectra along each line-of-sight of the instrument can be converted into ion energy spectra. By fitting the ion energy spectra with a Maxwellian velocity distribution, global maps of the ion temperature during periods of elevated activity can be generated [Scime et al., 2002]. In this work, we combine remote ion temperature imaging using neutral atoms with an image processing algorithm that accounts for variations in the viewing geometry due to orbital precession and seasonal variations to sum images from eight large geomagnetic storms. Storm time images were separated into four intervals, pre-storm, main phase, early recovery, and late recovery. To distinguish between storms with differing convection electric field strengths, the storms were sorted by cross polar cap potential drops obtained from DMSP satellite measurements of ion flows. We find that storms with strong polar cap potential drops (i.e. < - 80 kV) exhibit more ion heating during the main phase and throughout the recovery than storms with more mild potential drops (i.e. ~ -50 kV). Ion heating clearly localized to the ring current region is also more apparent in those storms with stronger polar cap potential drops.

Zaniewski, A.; Scime, E.; Hairston, M.; Thomsen, M.; Skoug, R.; Henderson, M.

2005-05-01

179

Summer Days.  

ERIC Educational Resources Information Center

In response to regular faculty complaints about mainstreamed students, a 5-week Summer Special Education Program was implemented in 1986 at the Western Navajo Agency's Tuba City Boarding School. The program's purpose was to train regular teachers and support personnel in special education procedures and practices and to provide the exceptional…

Foster, Carl; Beeman, Sandi

180

Occurrence frequency of convective gravity waves during the North American thunderstorm season  

Microsoft Academic Search

Convective gravity waves are an important driver of the equator-to-pole circulation in the stratospheric summer hemisphere, but their nature is not well known. Previous studies showing tight relationships between deep convection and convective waves mainly focus on tropical latitudes. For midlatitudes most analyses are based on case studies. Here we present a new multiyear occurrence frequency analysis of convective waves

L. Hoffmann; M. J. Alexander

2010-01-01

181

The Role of Ionospheric Outflow Preconditioning in Determining Storm Geoeffectiveness  

NASA Astrophysics Data System (ADS)

It is now well accepted that ionospheric outflow plays an important role in the development of the plasma sheet and ring current during geomagnetic storms. Furthermore, even during quiet times, ionospheric plasma populates the magnetospheric lobes, producing a reservoir of hydrogen and oxygen ions. When the Interplanetary Magnetic Field (IMF) turns southward, this reservoir is connected to the plasma sheet and ring current through magnetospheric convection. Hence, the conditions of the ionosphere and magnetospheric lobes leading up to magnetospheric storm onset have important implications for storm development. Despite this, there has been little research on this preconditioning; most global simulations begin just before storm onset, neglecting preconditioning altogether. This work explores the role of preconditioning in determining the geoeffectiveness of storms using a coupled global model system. A model of ionospheric outflow (the Polar Wind Outflow Model, PWOM) is two-way coupled to a global magnetohydrodynamic model (the Block-Adaptive Tree Solar wind Roe-type Upwind Scheme, BATS-R-US), which in turn drives a ring current model (the Ring current Atmosphere interactions Model, RAM). This unique setup is used to simulate an idealized storm. The model is started at many different times, from 1 hour before storm onset to 12 hours before. The effects of storm preconditioning are examined by investigating the total ionospheric plasma content in the lobes just before onset, the total ionospheric contribution in the ring current just after onset, and the effects on Dst, magnetic elevation angle at geosynchronous, and total ring current energy density. This experiment is repeated for different solar activity levels as set by F10.7 flux. Finally, a synthetic double-dip storm is constructed to see how two closely spaced storms affect each other by changing the preconditioning environment. It is found that preconditioning of the magnetospheric lobes via ionospheric outflow greatly influences the geoeffectiveness of magnetospheric storms.

Welling, D. T.; Liemohn, M. W.; Ridley, A. J.

2012-12-01

182

Effect of storm type on rainwater composition in southeastern North Carolina  

SciTech Connect

Rainwater composition in Wilmington, NC, varies as a function of storm origin or type. During 1983-1987, the most acidic rain and highest sulfate and nitrate concentrations occurred in rain from local summer thunderstorms, followed by rain from continental frontal storms, with the least acidic rain coming from coastal storms. Seasonal variation was observed for rainwater pH (although not for sulfate or nitrate concentrations) from continental storms, with the most acidic rain in the summer. Thunderstorm nitrate concentrations were high enough to affect seasonal averages for nitrate concentration because thunderstorms are a warm-season type of rain. Coastal storm rainwater did not show seasonal changes; this type of rainwater is similar in pH, sulfate, and nitrate concentrations to rainwater in remote areas of the world. Sulfate from sea spray was a small percentage of the total sulfate except in coastal storm rainwater. Large annual differences in rainwater composition were observed.

Willey, J.D.; Bennett, R.I.; Williams, J.M. Denne, R.K.; Kornegay, C.R.; Perlotto, M.S.; Moore, B.M.

1988-01-01

183

Feedbacks on convection from an African wetland  

NASA Astrophysics Data System (ADS)

The Niger Inland Delta in Mali floods every year in response to rain falling hundreds of kilometers upstream. This study examines the remote hydrological feedback between rainfall, fluvial inundation, and new convective storms. A satellite thermal infra-red dataset spanning 24 years is used to quantify both temporal variability in wetland extent, and the response of cloud cover to the wetland during August and September. The daytime initiation of convective storms is found to double during periods of inundation, consistent with a hypothesised “wetland breeze” effect. A signal of enhanced cloud cover propagates hundreds of kilometers westwards, linked to increased numbers of long-lived Mesoscale Convective Systems emanating from the wetland region. This effect raises the possibility that changes in upstream water use could have a climatic impact over a wide area.

Taylor, Christopher M.

2010-03-01

184

Hubble Observes a New Saturn Storm  

NASA Technical Reports Server (NTRS)

This NASA Hubble Space Telescope image of the ringed planet Saturn shows a rare storm that appears as a white arrowhead-shaped feature near the planet's equator. The storm is generated by an upwelling of warmer air, similar to a terrestrial thunderhead. The east-west extent of this storm is equal to the diameter of the Earth (about 7,900 miles). Hubble provides new details about the effects of Saturn's prevailing winds on the storm. The new image shows that the storm's motion and size have changed little since its discovery in September, 1994.

The storm was imaged with Hubble's Wide Field Planetary Camera 2 (WFPC2) in the wide field mode on December 1, 1994, when Saturn was 904 million miles from the Earth. The picture is a composite of images taken through different color filters within a 6 minute interval to create a 'true-color' rendition of the planet. The blue fringe on the right limb of the planet is an artifact of image processing used to compensate for the rotation of the planet between exposures.

The Hubble images are sharp enough to reveal that Saturn's prevailing winds shape a dark 'wedge' that eats into the western (left) side of the bright central cloud. The planet's strongest eastward winds (clocked at 1,000 miles per hour from analysis of Voyager spacecraft images taken in 1980-81) are at the latitude of the wedge.

To the north of this arrowhead-shaped feature, the winds decrease so that the storm center is moving eastward relative to the local flow. The clouds expanding north of the storm are swept westward by the winds at higher latitudes. The strong winds near the latitude of the dark wedge blow over the northern part of the storm, creating a secondary disturbance that generates the faint white clouds to the east (right) of the storm center.

The storm's white clouds are ammonia ice crystals that form when an upward flow of warmer gases shoves its way through Saturn's frigid cloud tops. This current storm is larger than the white clouds associated with minor storms that have been reported more frequently as bright cloud features.

Hubble observed a similar, though larger, storm in September 1990, which was one of three major Saturn storms seen over the past two centuries. Although these events were separated by about 57 years (approximately 2 Saturnian years) there is yet no explanation why they apparently follow a cycle -- occurring when it is summer in Saturn's northern hemisphere.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

1994-01-01

185

On the seasonal response of the thermosphere and ionosphere to geomagnetic storms  

Microsoft Academic Search

Ionosonde observations have provided the data to build a picture of the response of the midlatitude ionosphere to a geomagnetic storm. The particular characteristic of interest is the preference for ``negative storms'' (decrease in the peak electron density, NmF2) in summer and ``positive storms'' (increase in NmF2) in winter. A three-dimensional, time-dependent model of the coupled thermosphere and ionosphere is

T. J. Fuller-Rowell; M. V. Codrescu; H. Risbeth; R. J. Moffett; S. Quegan

1996-01-01

186

Storm Window Treatments  

NSDL National Science Digital Library

Students will be asked to analyze a given set of data to determine the best storm window treatments for a local company to use when building a new homes. Students will be asked to write a letter to the company explaining how they ranked the storm window treatments.

2012-12-03

187

Storm-Surge Forecasting.  

National Technical Information Service (NTIS)

The report contains an adaptation of a unique storm-surge forecasting technique developed by Dr. C. P. Jelesnianski. This technique results in a computed storm surge profile at the inner boundary of an artificial standard basin seaward of the coast. The p...

J. W. Nickerson

1971-01-01

188

Proton Storms - Aurora - Climate  

Microsoft Academic Search

Years ago a strong correlation was found between climate and geomagnetic storms. Is this still a surprise? Some months ago observations via IMAGE and Cluster satellites showed a possible missing link. Earth-directed proton storms can pervade the magnetic shield causing proton aurora and a positive charge of all drops and ice crystals of a cloud. Then these cloud-particles push each

L. Körtvelyessy

2004-01-01

189

Investigating Magnetic Storms  

NSDL National Science Digital Library

This is a lesson to introduce the Kp index, a common numerical indicator of magnetic storminess. Learners will access and analyze Kp index plots of magnetic storm strength and determine the relative frequency of stronger versus weaker magnetic storms. This is the fourteenth activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

190

STORM WATER MANAGEMENT MODEL  

EPA Science Inventory

Storm Water Management Model (SWMM) is a comprehensive model for analysis of quantity and quality problems associated with urban runoff. Both single-event and continuous simulation may be performed on catchments having storm sewers, combined sewers, and natural drainage, for pred...

191

Tropical Storm Cristobal  

NSDL National Science Digital Library

This animation shows Tropical Storm Cristobal on August 7, 2002 . Cristobal was located east of St. Augustine, Florida. The storm has had a maximum sustained wind speed of 45 MPH.Cristobal is expected to move east-northeast within the next 24 hours.

Perkins, Lori; Halverson, Jeff

2002-08-07

192

The Vertical Distribution of Dust in the Martian Atmosphere: The Haze in the Clear Season and the Haze After the Storm  

NASA Astrophysics Data System (ADS)

Observations by the Mars Climate Sounder (MCS) over the last two martian years have permitted the creation of pressure-pegged retrievals of temperature, dust opacity, and water ice opacity at a vertical resolution of approximately 5 km. These retrievals provide information about the vertical distribution of dust and water ice over a wide dynamic range of mass mixing ratio and/or aerosol heating rate. Thus, MCS retrievals can powerfully complement observations by nadir-looking instruments on Mars Reconnaissance Orbiter or surface landers. For whereas nadir-looking instruments are most sensitive to order unity cloud cover near the surface, MCS limb retrievals are most sensitive to the sub-visible hazes farther above the surface. In this presentation, we will discuss two broad types of dust haze we have identified in MCS retrievals and their significance for dust lifting, transport, and removal processes in the martian atmosphere. In late northern spring and early northern summer, the dust mass mixing ratio profile in the tropics appears to have a significant maximum between 15 and 25 km above the local surface, “the high altitude tropical dust maximum.” While water ice condensation on dust particles and orographically-driven dust lifting may play some role in driving this distribution, we have argued that its primary driver is more likely to be a process akin to moist convection in which shortwave heating of dust in Mars’s thin atmosphere has very similar effects to the latent heat released by condensing water vapor in the Earth’s atmosphere. This type of haze is associated with low column dust opacities throughout the latitudinal band in which it occurs. The other type of haze is associated with the much higher column opacities attributed to dust storm activity. We will present examples from north polar cap edge dust storm activity in northern spring, early season tropical dust storm activity in the middle of northern summer, and the global dust storm of 2007. The latter two events produced hazes with dust mass mixing ratio maxima of greater magnitude and at higher altitude than the high altitude tropical dust maximum, which are consonant with hazes observed by MGS/TES during the 2001 global dust storm. These observations raise the question of whether the second type of dust haze could be driven by a larger-scale version of the pseudo-moist convection we have proposed to explain the first.

Heavens, N. G.; Richardson, M. I.; Kleinboehl, A.; Kass, D.; McCleese, D. J.; Mars Climate Sounder Science Team

2010-12-01

193

Summer Reading  

NSDL National Science Digital Library

Summer is a great time to kick back with a good book. Try The Bailey School Kids Series... it\\'s Great! Bailey School Kids Jan Brett is my favorite artist. It takes longer to look at the pictures than it does to read the book. But it\\'s worth it. Jan Brett I love Bunnicula, almost as much as I love Harold. Find out ...

Roner, Mrs.

2005-03-31

194

Oxidant Enhancement in Martian Dust Devils and Storms: I. Storm Electric Fields and Electron Dissociative Attachment  

NASA Astrophysics Data System (ADS)

Laboratory studies, computer simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity". In convective structures such as dust devils or storms, grain stratification (leading to charge separation) gives rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies indicate that this storm electric field on Mars can approach the ambient breakdown field strength of 20 kV/m. Noteable, in terrestrial dust devils, coherent dipolar electric fields have been measured to near 20 kV/m. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via electric fields to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model, we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach breakdown levels of 20-30 kV/m. These storm-related chemical products are key ingredients for the generation of oxidants which can ultimately affect the habitability of Mars, as discussed in the following companion presentation.

Delory, G. T.; Farrell, W. T.; Sentman, D. D.; Renno, N. O.; Atreya, S. K.; Wong, A.; Cummer, S. A.; Marshall, J.; Rafkin, S.; Catling, D.

2004-12-01

195

Structure of Highly Sheared Tropical Storm Chantal during CAMEX-4  

NASA Technical Reports Server (NTRS)

Tropical Storm Chantal during August 2001 was a storm that failed to intensify over the few days prior to making landfall on the Yucatan Peninsula. An observational study of Tropical Storm Chantal is presented using a diverse dataset including remote and in situ measurements from the NASA ER-2 and DC-8 and the NOAA WP-3D N42RF aircraft and satellite. The authors discuss the storm structure from the larger-scale environment down to the convective scale. Large vertical shear (850-200-hPa shear magnitude range 8-15 m/s) plays a very important role in preventing Chantal from intensifying. The storm had a poorly defined vortex that only extended up to 5-6-km altitude, and an adjacent intense convective region that comprised a mesoscale convective system (MCS). The entire low-level circulation center was in the rain-free western side of the storm, about 80 km to the west-southwest of the MCS. The MCS appears to have been primarily the result of intense convergence between large-scale, low-level easterly flow with embedded downdrafts, and the cyclonic vortex flow. The individual cells in the MCS such as cell 2 during the period of the observations were extremely intense, with reflectivity core diameters of 10 km and peak updrafts exceeding 20 m/s. Associated with this MCS were two broad subsidence (warm) regions, both of which had portions over the vortex. The first layer near 700 hPa was directly above the vortex and covered most of it. The second layer near 500 hPa was along the forward and right flanks of cell 2 and undercut the anvil divergence region above. There was not much resemblance of these subsidence layers to typical upper-level warm cores in hurricanes that are necessary to support strong surface winds and a low central pressure. The observations are compared to previous studies of weakly sheared storms and modeling studies of shear effects and intensification. The configuration of the convective updrafts, low-level circulation, and lack of vertical coherence between the upper- and lower-level warming regions likely inhibited intensification of Chantal. This configuration is consistent with modeled vortices in sheared environments, which suggest the strongest convection and rain in the downshear left quadrant of the storm, and subsidence in the upshear right quadrant. The vertical shear profile is, however, different from what was assumed in previous modeling in that the winds are strongest in the lowest levels and the deep tropospheric vertical shear is on the order of 10-12 m/s.

Heymsfield, G. M.; Halverson, J.; Ritchie, E.; Simpson, Joanne; Molinari, J.; Tian, L.

2006-01-01

196

Meteorology, Macrophysics, Microphysics, Microwaves, and Mesoscale Modeling of Mediterranean Mountain Storms: The M8 Laboratory  

NASA Technical Reports Server (NTRS)

Comprehensive understanding of the microphysical nature of Mediterranean storms can be accomplished by a combination of in situ meteorological data analysis and radar-passive microwave data analysis, effectively integrated with numerical modeling studies at various scales, from synoptic scale down through the mesoscale, the cloud macrophysical scale, and ultimately the cloud microphysical scale. The microphysical properties of and their controls on severe storms are intrinsically related to meteorological processes under which storms have evolved, processes which eventually select and control the dominant microphysical properties themselves. This involves intense convective development, stratiform decay, orographic lifting, and sloped frontal lifting processes, as well as the associated vertical motions and thermodynamical instabilities governing physical processes that affect details of the size distributions and fall rates of the various types of hydrometeors found within the storm environment. Insofar as hazardous Mediterranean storms, highlighted in this study by three mountain storms producing damaging floods in northern Italy between 1992 and 2000, developing a comprehensive microphysical interpretation requires an understanding of the multiple phases of storm evolution and the heterogeneous nature of precipitation fields within a storm domain. This involves convective development, stratiform transition and decay, orographic lifting, and sloped frontal lifting processes. This also involves vertical motions and thermodynamical instabilities governing physical processes that determine details of the liquid/ice water contents, size disi:ributions, and fall rates of the various modes of hydrometeors found within hazardous storm environments.

Starr, David O. (Technical Monitor); Smith, Eric A.

2002-01-01

197

New insights on geomagnetic storms from observations and modeling  

SciTech Connect

Understanding the response at Earth of the Sun's varying energy output and forecasting geomagnetic activity is of central interest to space science, since intense geomagnetic storms may cause severe damages on technological systems and affect communications. Episodes of southward (Bzstorms representative of each interplanetary condition with our kinetic ring current atmosphere interactions model (RAM), and investigate the mechanisms responsible for trapping particles and for causing their loss. We find that periods of increased magnetospheric convection coinciding with enhancements of plasma sheet density are needed for strong ring current buildup. During the HSS-driven storm the convection potential is highly variable and causes small sporadic injections into the ring current. The long period of enhanced convection during the CME-driven storm causes a continuous ring current injection penetrating to lower L shells and stronger ring current buildup.

Jordanova, Vania K [Los Alamos National Laboratory

2009-01-01

198

The 2008 Super Tuesday Tornado Outbreak: Overview of the Tornadoes and their Parent Storms  

NASA Technical Reports Server (NTRS)

The cold-season Tornado outbreak that occurred over the Southeast on 5-6 February 2008 was significant for the following reasons: about 84 tornadoes were documented over a 15 h period between late afternoon on 5 February and early morning on 6 February 2008; a wide variety of parent storms were associated with the tornadoes; a total of five EF-4 tornadoes occurred, with two forming over Alabama during the early morning hours prior to sunrise; there was a significant lull period between the initial convective and the early morning activity over Alabama 10 hours later; and, a wide spectrum of storm types, ranging from isolated supercell storms to QLCS bow echoes, accompanied the tornadoes. The goal of this paper is to provide a general description of the outbreak including the distribution of tornadoes and supercell storms over the region, a detailed map of the tornado tracks, time series of tornadoes and parent storms, and general characteristics of all parent tornado storms. The total number of major storms (duration greater than 3 h, at least three tornadoes produced) was seven. Several noteworthy storms are described: a long track (198 km long) tornado and its parent storm over Arkansas; a prolific supercell storm persisted for 7-8 hours and produced 16 tornadoes from north-central Mississippi to southern KY; and, bow echo storms (QLCS's) were simultaneous over KY and produced 16 tornadoes.

Knupp, Kevin R.; Coleman, Tim; Carey, Larry; Petersen, Walt

2008-01-01

199

Tropical Storm Don  

NASA Video Gallery

GOES-13 data was compiled into an animation by the NASA GOES Project at NASA Goddard that shows the development of Tropical Storm Don in the southern Gulf of Mexico, west of Cuba. The animation run...

200

Climate science: Shifting storms  

NASA Astrophysics Data System (ADS)

An analysis of historical storm data reveals that the average latitude at which tropical cyclones attain their maximum intensity has undergone a pronounced shift towards the poles over the past three decades. See Letter p.349

Ramsay, Hamish

2014-05-01

201

Dust Storm Safety  

MedlinePLUS

... stop on the traveled portion of the roadway. LIGHTS OUT! In the past, motorists driving in dust storms have pulled off the roadway, leaving lights on. Vehicles approaching from the rear and using ...

202

Ionospheric Storms — A Review  

Microsoft Academic Search

In this paper, our current understanding and recent advances in the study of ionospheric storms is reviewed, with emphasis\\u000a on the F2-region. Ionospheric storms represent an extreme form of space weather with important effects on ground- and space-based\\u000a technological systems. These phenomena are driven by highly variable solar and magnetospheric energy inputs to the Earth's\\u000a upper atmosphere, which continue to

M. J. Buonsanto

1999-01-01

203

Predicting lightning storms  

NASA Astrophysics Data System (ADS)

Lightning is the second most deadly weather phenomenon after flash floods. It kills more people a year than tornadoes and damages utilities, curtails recreational activities, and affects flight paths. Roughly half of all aviation accidents are weather related according to Delain Edman, of the National Weather Service's National Severe Storms Forecast Center, Kansas City, Mo. That's why meteorologists are testing a new lightning detection network to help predict storms and pinpoint “hot spots” of lightning activity.

Wainger, Lisa A.

204

Observation and numerical simulation of a convective initiation during COHMEX  

NASA Technical Reports Server (NTRS)

Under a synoptically undisturbed condition, a dual-peak convective lifecycle was observed with the COoperative Huntsville Meteorological EXperiment (COHMEX) observational network over a 24-hour period. The lifecycle included a multicell storm, which lasted about 6 hours, produced a peak rainrate exceeding 100 mm/hr, and initiated a downstream mesoscale convective system. The 24-hour accumulated rainfall of this event was the largest during the entire COHMEX. The downstream mesoscale convective system, unfortunately, was difficult to investigate quantitatively due to the lack of mesoscale observations. The dataset collected near the time of the multicell storm evolution, including its initiation, was one of the best datasets of COHMEX. In this study, the initiation of this multicell storm is chosen as the target of the numerical simulations.

Song, J. Aaron; Kaplan, Michael L.

1991-01-01

205

Why do Tornados and Hail Storms Rest on Weekends?  

NASA Technical Reports Server (NTRS)

When anthropogenic aerosols over the eastern USA during summertime are at their weekly mid-week peak, tornado and hail storm activity there is also near its weekly maximum. The weekly cycle in storm activity is statistically significant and unlikely to be due to natural variability. The pattern of variability supports the hypothesis that air pollution aerosols invigorate deep convective clouds in a moist, unstable atmosphere, to the extent of inducing production of large hailstones and tornados. This is caused by the effect of aerosols on cloud-drop nucleation, making cloud drops smaller, delaying precipitation-forming processes and their evaporation, and hence affecting cloud dynamics.

Rosenfeld, Daniel; Bell, Thomas L.

2010-01-01

206

The moisture budget in relation to convection  

NASA Technical Reports Server (NTRS)

An evaluation of the moisture budget in the environment of convective storms is presented by using the unique 3- to 6-h rawinsonde data. Net horizontal and vertical boundary fluxes accounted for most of the large amounts of moisture which were concentrated into convective regions associated with two squall lines that moved through the area during the experiment. The largest values of moisture accumulations were located slightly downwind of the most intense convective activity. Relationships between computed moisture quantities of the moisture budget and radar-observed convection improved when lagging the radar data by 3 h. The residual of moisture which represents all sources and sinks of moisture in the budget equation was largely accounted for by measurements of precipitation.

Scott, R. W.; Scoggins, J. R.

1977-01-01

207

Trajectory analysis of Saudi Arabian dust storms  

NASA Astrophysics Data System (ADS)

Temporal and spatial characteristics of Saudi Arabian dust storms, with focus on associated air parcel trajectories, are investigated using station and gridded weather observations and remotely-sensed aerosol optical depth (AOD). For 13 focal stations, an extensive pool of 84-h backward trajectories is developed for dust storm days, and the trajectories are grouped into 3-5 representative clusters based on the K-means technique and Silhouette Coefficients. Saudi Arabian dust storms are most prominent during February-June, with a mid-winter peak along the southern coast of the Red Sea, spring peak across northern Saudi Arabia around the An Nafud Desert, and early summer peak in eastern Saudi Arabia around the Ad Dahna Desert. Based on backward trajectories, the primary local dust source is the Rub Al Khali Desert and the primary remote sources are the Saharan Desert, for western Saudi Arabia, and Iraqi Deserts, for northern and eastern Saudi Arabia. During February-April, the Mediterranean storm track is active, with passing cyclones and associated cold fronts carrying Saharan dust to Saudi Arabian stations along the northern coast of the Red Sea. Across Saudi Arabia, the highest AOD is achieved during dust storms that originate from the Rub Al Khali and Iraqi Deserts. Most stations are dominated by local dust sources (primarily Rub Al Khali), are characterized by three dominant trajectory paths, and achieve AOD values exceeding 1. In contrast, for stations receiving predominantly remote dust (particularly Saharan), 3-5 trajectory paths emerge and AOD values only reach approximately 0.6 as dust is lost during transport.

Notaro, Michael; Alkolibi, Fahad; Fadda, Eyad; Bakhrjy, Fawzieh

2013-06-01

208

How does the thermosphere and ionosphere react to a geomagnetic storm?  

NASA Astrophysics Data System (ADS)

Unraveling the ionospheric and thermospheric response to a geomagnetic storm has been a challenge for many decades, due largely to the complex interactions between the plasma and neutral species. Geomagnetic storm sources to the upper atmosphere are caused by an increase in the convective electric field and auroral precipitation, that give rise to Joule heating, the primary driver of global atmospheric change. Driven by the impulsive energy input, wave surges propagate and interact globally, and are dependent on Universal lime (UT) and the time history of the source. There is a strong preference for surges to maximize on the nightside and in the longitude sector adjacent to the magnetic pole. Equatorward wind surges drive the plasma upwards and can initiate a positive ionospheric change. The divergent nature of the wind field causes upwelling and changes to the neutral composition that can be transported by the storm and background wind fields. Negative ionospheric phases result from increased molecular species. Ionosondes have recorded the apparently chaotic ionospheric response for more than 50 years, but it is only recently that local time (LT) and seasonal dependencies have been quantified. Numerical models have shed light on the physical processes; the LT response is caused by the diurnal wind field migration of the composition "bulge," and the seasonal dependence is controlled through the transport of the bulge by the summer-to-winter prevailing circulation. Neutral density changes and satellite airglow observations support this basic concept. At low latitudes, electrodynamic changes are initiated by penetration of magnetospheric fields followed by rapid shielding. After shielding, the electrodynamics is forced by dynamo action of the disturbed neutral atmosphere, driving a sequence of equatorial plasma drifts for more than a day. The precise mechanisms responsible for this equatorial response have yet to be defined, but it is tempting to associate the time-scales with those of the global dynamical and composition response of the neutral atmosphere. Despite an increase in our understanding of the causes of the mid-latitude ionospheric response, simulation of a real storm has yet to confirm theory. We are limited by accurate knowledge of the source function, and by the lack of comprehensive data coverage of both the neutral and ionospheric parameters. Both are needed before theory and models can be thoroughly tested.

Fuller-Rowell, T. J.; Codrescu, M. V.; Roble, R. G.; Richmond, A. D.

209

Indian Summer  

SciTech Connect

This paper focuses on preserving and strengthening two resources culturally and socially important to the Shoshone-Bannock Indian Tribe on the Fort Hall Reservation in Idaho; their young people and the Pacific-Northwest Salmon. After learning that salmon were not returning in significant numbers to ancestral fishing waters at headwater spawning sites, tribal youth wanted to know why. As a result, the Indian Summer project was conceived to give Shoshone-Bannock High School students the opportunity to develop hands-on, workable solutions to improve future Indian fishing and help make the river healthy again. The project goals were to increase the number of fry introduced into the streams, teach the Shoshone-Bannock students how to use scientific methodologies, and get students, parents, community members, and Indian and non-Indian mentors excited about learning. The students chose an egg incubation experiment to help increase self-sustaining, natural production of steelhead trout, and formulated and carried out a three step plan to increase the hatch-rate of steelhead trout in Idaho waters. With the help of local companies, governmental agencies, scientists, and mentors students have been able to meet their project goals, and at the same time, have learned how to use scientific methods to solve real life problems, how to return what they have used to the water and land, and how to have fun and enjoy life while learning.

Galindo, E. [Sho-Ban High School, Fort Hall, ID (United States)

1997-08-01

210

Convection Current  

NSDL National Science Digital Library

In this activity, learners make their own heat waves in an aquarium. Warmer water rising through cooler water creates turbulence effects that bend light, allowing you to project swirling shadows onto a screen. Use this demonstration to show convection currents in water as well as light refraction in a simple, visually appealing way.

Exploratorium, The

2012-06-26

211

Convection towers  

DOEpatents

Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

Prueitt, Melvin L. (Los Alamos, NM)

1996-01-01

212

Convection towers  

DOEpatents

Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

Prueitt, Melvin L. (Los Alamos, NM)

1995-01-01

213

Mesoscale characteristics of monsoonal convection and associated stratiform precipitation  

NASA Technical Reports Server (NTRS)

Observations undertaken on 12 January 1990 at Darwin (Australia) are used to document the structure of a monsoonal rainband in a low convective available potential energy low-shear tropical environment. Dual-Doppler radar analyses are employed to investigate the structure and kinematics of the convective and stratiform regions. A system with the characteristics of a relatively short-lived squall line in which warm rain processes play a significant role in the production of precipitation is evident. Planetary boundary layer cold-pool production is important in the organization and motion of the system. A trailing stratiform region is evident with a mean updraft-downdraft circulation, but is composed of in situ decaying convective cells. A storm-relative mesoscale cyclonic circulation is also observed within the stratiform cloud. This vortex was maintained by thermodynamically induced midlevel convergence, convectively generated storm-scale circulations, and their interaction with the background monsoon flow.

Keenan, Thomas D.; Rutledge, Steven A.

1993-01-01

214

Superposed epoch analyses of ion temperatures during CME- and CIR/HSS-driven storms  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) and corotating interaction regions associated with high speed solar wind streams (CIR/HSSs) drive geomagnetic storms in the terrestrial magnetosphere. Each type of storm driver yields different dynamics of storm evolution. We present results from comparative superposed epoch analyses of global ion temperatures calculated from TWINS energetic neutral atom (ENA) data and simulations using the comprehensive ring current model (CRCM). During the June 2008-April 2012 timeframe, 48 geomagnetic storms (minimum Dst?-40 nT) occurred. Of these, 21 storms were CME-driven and 15 were driven by CIR/HSSs. Superposed epoch analysis results demonstrate that ion temperatures increase during the recovery phase of CIR/HSS-driven storms, while ions are rapidly heated at the commencement of CME-driven storms then cool over the main phase, particularly for intense (minimum Dst?-78 nT) CME-driven storms. Higher energy ions are convected to lower L-shells during CME-driven storms, while CIR/HSS-driven storms tend to have average ion temperatures that are higher on the dayside than nightside.

Keesee, A. M.; Elfritz, J. G.; Fok, M.-C.; McComas, D. J.; Scime, E. E.

2014-08-01

215

Complex Weather Study to Target Summer Storm Forecasting  

NSF Publications Database

... that fuel heavy rain across the southern Great Plains from Texas to Kansas. Scientists hope that ... heavy rainfall out a few hours, you're doing great." Heavy rain depends on an ample supply of ...

216

Banded ion morphology - Main and recovery storm phases  

NASA Technical Reports Server (NTRS)

The occurrence of bands in ion spectra obtained with the high-altitude and low-altitude plasma instruments on DE-1 and DE-2, respectively, during main and recovery storm phases from the period September 1981 - January 1982 is analyzed statistically. Typical spectra are shown; diagrams and graphs of storm morphology are provided; and two theoretical models (one based on time-of-flight effects and another based on convective dispersion) are discussed. It is found that bands occur more often in the main phase than in the recovery phase, and more often and at higher latitudes in the evening than before noon. From the stability of the bands and the dependence of energy on latitude it is inferred that convective dispersion plays a more important role than time-of-flight effects in the motion of heavy ions in the magnetosphere.

Frahm, R. A.; Reiff, P. H.; Winningham, J. D.; Burch, J. L.

1986-01-01

217

Storm Track Sensitivity to Changes in Moist Circulation in a General Circulation Model  

NASA Astrophysics Data System (ADS)

Global warming projections in General Circulation Models (GCMs) show that the moisture content in both the tropics and midlatitudes will increase. Both of these changes may affect the midlatitude storm tracks. For instance, more vigorous moist convection within the Hadley Cell may increase the export Rossby waves. On the other hand, more moisture in the poleward component of midlatitude storms increases their efficiency at moving energy poleward. Thus, the relative role of these regional changes in forcing the storm tracks is an open question. To gain perspective on how the storm tracks respond in a GCM, experiments are carried out using the atmosphere component of the NASA Goddard Institute for Space Studies ModelE2. We generate a set of different simulations by changing either: (1) the model configuration, or (2) the model's parameterized convection scheme. By design, these runs have different climatological mean states, especially in terms of their atmospheric moisture content. The storm tracks from each simulation are compared, in terms of their location, strength, seasonal cycle and interannual variability. Then, the behavior of the storm tracks is placed in the context of existing theories through an analysis of each simulation's Hadley Circulation and midlatitude vertical stability. We find that the storm track location varies with the strength of Hadley circulation, however local changes in physics affect the amplitude of the storm track response. Finally, each model's moist overturning circulation is calculated by averaging the mean circulation on moist isentropes. This analysis is presented as both (I) a tool for understanding the moist isentropic circulation, and (II) a method for comparing storm tracks with the moist circulation. We find that the strength of the moist overturning circulation north of the midlatitude baroclinic zone has a positive correlation with the strength of the storm tracks in this model. However, south of the midlatitude baroclinic zone, extending into the subtropics, the strength of the moist overturning circulation does not positively co-vary with the storm track strength.

Booth, J. F.

2012-12-01

218

Tropical Storm Lee to Newfoundland  

NASA Video Gallery

This video shows Tropical Storm Lee as it made landfall in Louisiana and Mississippi on September 4, 2011. This storm produced flooding and tornadoes to the southern states all the way to flooding ...

219

Kinetic energy budgets in areas of convection  

NASA Technical Reports Server (NTRS)

Synoptic scale budgets of kinetic energy are computed using 3 and 6 h data from three of NASA's Atmospheric Variability Experiments (AVE's). Numerous areas of intense convection occurred during the three experiments. Large kinetic energy variability, with periods as short as 6 h, is observed in budgets computed over each entire experiment area and over limited volumes that barely enclose the convection and move with it. Kinetic energy generation and transport processes in the smaller volumes are often a maximum when the enclosed storms are near peak intensity, but the nature of the various energy processes differs between storm cases and seems closely related to the synoptic conditions. A commonly observed energy budget for peak storm intensity indicates that generation of kinetic energy by cross-contour flow is the major energy source while dissipation to subgrid scales is the major sink. Synoptic scale vertical motion transports kinetic energy from lower to upper levels of the atmosphere while low-level horizontal flux convergence and upper-level horizontal divergence also occur. Spatial fields of the energy budget terms show that the storm environment is a major center of energy activity for the entire area.

Fuelberg, H. E.

1979-01-01

220

Lightning as a Detector of Convective Surges in Thunderstorms  

NASA Astrophysics Data System (ADS)

New Mexico Tech's 3-dimensional lightning mapping system (LMA) was operated in support of the Severe Thunderstorm Electrification and Precipitation Study (STEPS) from late May to early August 2000. Previous LMA studies discovered occasions where high-altitude radiation sources were frequently observed above convective thunderstorms. These observations represented a lightning phenomena which had not been observed prior to the advent of the LMA. The events consisted of frequent, localized, short-duration discharges and appeared to occur continuously and independently of other lightning activity in the lower regions of the storm. Indications were that the events happen within (or possibly above) overshooting tops associated with strong convective bursts in thunderstorms. On June 29, 2000 during STEPS, the LMA recorded a storm which produced an F1 tornado. Prior to tornado formation there were three periods where lightning sources rose above the main discharge regions of the storm. During these occasions of enhanced high-altitude activity, lightning free holes formed in the central region of the cell, indicating that the events correlate with overshooting convective tops. Several other convective bursts occurred in rapid succession after the third, and an F1 tornado formed. Following the tornado, the storm continued to show strong convective surges as well as an overall increase in height of lightning activity. In this paper we discuss case studies where a height versus time display, over the active lifetime of a storm, demonstrates similar behavior. When the data is displayed over a large time range the epochs of enhanced high-altitude discharges are very clear, and indicate an increase in storm intensity and severity.

Hamlin, T.; Harlin, J. D.; Krehbiel, P. R.; Rison, W.; Thomas, R. J.

2001-12-01

221

A portable CW/FM-CW Doppler radar for local investigation of severe storms  

NASA Astrophysics Data System (ADS)

During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm.

Unruh, Wesley P.; Wolf, Michael A.; Bluestein, Howard B.

222

A portable CW/FM-CW Doppler radar for local investigation of severe storms  

SciTech Connect

During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm. 2 refs., 2 figs.

Unruh, W.P.; Wolf, M.A.; Bluestein, H.B.

1988-01-01

223

Analysis and tracking of convective cells over north-western Italy  

Microsoft Academic Search

The identification and storm-tracking of convective cells is one of the most interesting sectors of that field of meteorology known as nowcasting. In the present work the main behaviour of the convective cells above North-Western Italy was studied, , using the ARPA Piemonte weather radar. The analysis carried out evaluates the spatial and temporal distribution of many parameters that characterize

P. Davini; R. Cremonini; R. Bechini; C. Cassardo

2009-01-01

224

Signatures of Magnetic Storms Induced by Magnetic Clouds  

NASA Astrophysics Data System (ADS)

We have studied 11 magnetic storms (in 1997) that were induced by the smoothly varying Bz component of the interplanetary magnetic field typical of interplanetary magnetic clouds. It was found that there was a lack of substorm expansion phases for long periods of time (up to 7 hr) in 5 out of 11 storm main phases. In this paper, a relatively weak magnetic storm event (with minimum SYM-H at -47 nT) that occurred on July 15, 1997 is studied using ground-based magnetograms, polar cap potentials from SuperDARN, and LANL geosynchronous energetic particle data as well as the Polar UV imaging (for aurorae) and Wind (for the solar wind) data. It is shown that during the storm main phase, there was a lack of substorm expansion phase activity (from imaging and the ground-based data) and a lack of energetic particle injections at the geostationary orbit. The corresponding ring current intensification was weak. The most prominent auroral forms were north-south aligned auroral patches and torches. Dawn and dusk aurorae were more intense than the aurorae near midnight, where auroral gaps were seen. In addition, this paper shows that there was significant directly driven activity during the storm main phase when the IMF was continually southward. We argue that during this event the ring current intensification was more strongly associated with enhanced magnetospheric convection than with substorm-generated impulsive unloading of energy from the tail. Three scenarios are suggested to explain the relatively low-intensity of the magnetic storm induced by a magnetic cloud. They are: 1) weak nightside auroral zone ionospheric ion outflows (due to lack of substorms), 2) choked penetration of the tail plasma flow (due to lack of substorms), 3) retarded magnetospheric convection (due to reduced solar wind-magnetosphere reconnection). The observed saturation of the polar cap potential drop is consistent with this last mechanism.

Zhou, X.; Tsurutani, B. T.; Ruohoniemi, J. M.; Reeves, G.; Rostoker, G.; Sun, W.; Kamide, Y.; Lui, T. Y.; Parks, G. K.; Gonzalez, W. D.

2003-12-01

225

Storm restoration: people, technology, process  

Microsoft Academic Search

Summary form only given. Progress Energy Corporation believes the most significant key to storm restoration success is the committed and heroic efforts of Progress Energy's employees and the many friends from neighboring utilities and utility contractors that came to our aid. Comprehensive, well-documented storm response plans are vital to being prepared. At Progress Energy, our storm plan is a living

S. Hoyt

2004-01-01

226

Reverse convection  

SciTech Connect

A model of magnetospheric topology for periods when the interplanetary magnetic field (IMF) points northward indicates that reverse convection can readily occur when Earth's dipole or the IMF tilt toward or away from the Sun. In either case, all or part of one tail lobe drapes over the dayside, and the magnetopause merging voltage is applied directly to the ionosphere in that lobe only, to the center or nightside of the polar cap. The overdraped lobe forms layers both earthward and sunward of the magnetopause, similar to layers observed during periods of northward IMF. The model predicts two quasi-steady state patterns of reverse convection: (1) lobe cells in the polar cap of the overdraped lobe, generated by open-to-open flux transfer at the magnetopause and (2) merging cells in both polar caps, generated by closed-to-open flux transfer at the magnetopause and balanced open-to-closed transfer at an internal reconnection site, comparable to the tail merging site for southward IMF. The model also predicts transitional patterns of reverse convection for growing and shrinking polar caps in response to changes in dipole tilt and B[sub x] and in response to a sudden transition from southward to northward IMF. The model predicts theta aurora bar formation on the dawnside polar cap boundary when activation of the internal reconnection site ends polar cap growth. In this view the theta aurora becomes the northward IMF counterpart to substorms.

Crooker, N.U. (Univ. of California, Los Angeles (United States))

1992-12-01

227

TLEs, ITCZ, Storm Tracks and Their Correlation  

NASA Astrophysics Data System (ADS)

Between July 2004 and February 2008, ISUAL has recorded 6747 elves, 718 sprites, 783 halos, 1081 blue jets, and 17 gigantic jets. We examine the correlation between the distribution of TLEs and the annual Inter- tropical Convergence Zone (ITCZ) distribution by analyzing the outgoing long-wave radiation (OLR) data from NOAA/ESRL Physical Sciences Division. The results indicate that there are two different TLE distribution patterns. For the low latitude region, the movement of TLEs occurrence follows the seasonal migration of the IITCZ. In northern hemisphere summer, the ITCZ is mainly located to the north of the equator and the distribution of TLEs follows. In southern hemisphere summer, part of ITCZ moves to south of the equator and so does the distribution of TLEs. In the middle and high latitude winter regions, the ISUAL recorded TLEs are defined as the winter TLEs, which are generally associated with cold fronts, air masses and mid-latitude cyclones. From the global distribution of winter TLEs, it is shown that they tend to congregate in some specific regions. Namely, in the northern winter , TLEs concentrate over the Japan Sea , north Pacific Ocean , northwest Atlantic Ocean and Mediterranean Sea ; while in the southern winter , TLEs distribute primarily over the south coast of Australia , south Pacific Ocean and east coast of south America. We find the distribution of winter TLEs is well collocated with the storm tracks. The correlation between the winter TLEs and storm tracks is thus analyzed.

Lee, L.; Chen, A. B.; Tsai, L.; Chou, J.; Chang, S.; Kuo, C.; Su, H.; Hsu, R.; Wu, C.; Lin, P.; Lee, L.

2008-12-01

228

STORM INLET FILTRATION DEVICE  

EPA Science Inventory

Five field tests were conducted to evaluate the effectiveness of the Storm and Groundwater Enhancement Systems (SAGES) device for removing contaminants from stormwater. The SAGES device is a three-stage filtering system that could be used as a best management practices (BMP) retr...

229

Magnetic Storms and Aurora  

NSDL National Science Digital Library

This is a lesson to investigate auroras. Learners will plot and compare the amount of energy dissipated by auroras in the northern hemisphere with the recorded Kp index of magnetic storm severity. This is the sixteenth activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

230

California's Perfect Storm  

ERIC Educational Resources Information Center

The United States today faces an economic crisis worse than any since the Great Depression of the 1930s. Nowhere is it sharper than in the nation's schools. Last year, California saw a perfect storm of protest in virtually every part of its education system. K-12 teachers built coalitions with parents and students to fight for their jobs and their…

Bacon, David

2010-01-01

231

Stories from the Storm  

ERIC Educational Resources Information Center

For four months, St. Paul's Episcopal School in the Lakeview neighborhood of New Orleans, Louisiana remained closed after Hurricane Katrina ravaged the entire city in August 2005. The storm left St. Paul's campus under nine feet of water for two weeks, destroying many buildings and the entire first floor of the campus. As the only remaining art…

Smoczynski, Carol

2007-01-01

232

Big Storm Named Katrina.  

National Technical Information Service (NTIS)

Many students are affect every year by hurricanes and the weather hazards that come with a storm. Through this book students will become aware of how important it is to understand hurricanes and their impacts. Students can tell their parents and friends w...

R. T. Carson

2006-01-01

233

Hurricane Sandy Storm Tide Mapper  

NSDL National Science Digital Library

United States Geological Survey (USGS) provides real-time map-based information from USGS storm tide sensors. The data is reflected on the Hurricane Sandy Tide Mapper. The mapper provides location information, site photos and data for storm tide and inland flooding. In addition, the data from these sensors is used to create models of the precise time the storm-tide arrived, how ocean and inland water levels changed during the storm, the depth of the storm-tide throughout the event, and how long it took for the water to recede.

234

Forecasting Dust Storms - Version 2  

NSDL National Science Digital Library

Forecasting Dust Storms Version 2 provides background and operational information about dust storms. The first part of the module describes dust source regions, the life cycle of a dust storm, and the major types of dust storms, particularly those found in the Middle East. The second part presents a process for forecasting dust storms and applies it to a case in the Middle East. Although the process refers to U.S. Department of Defense models and tools, it can easily be adapted to other forecast requirements and data sources. Note that this module is an updated version of the original one published in 2003.

Weingroff, Marianne

2007-02-02

235

Energy and Mass Transport of Magnetospheric Plasmas during the November 2003 Magnetic Storm  

NASA Technical Reports Server (NTRS)

Intensive energy and mass transport from the solar wind across the magnetosphere boundary is a trigger of magnetic storms. The storm on 20-21 November 2003 was elicited by a high-speed solar wind and strong southward component of interplanetary magnetic field. This storm attained a minimum Dst of -422 nT. During the storm, some of the solar wind particles enter the magnetosphere and eventually become part of the ring current. At the same time, the fierce solar wind powers strong outflow of H+ and O+ from the ionosphere, as well as from the plasmasphere. We examine the contribution of plasmas from the solar wind, ionosphere and plasmasphere to the storm-time ring current. Our simulation shows, for this particular storm, ionospheric O+ and solar wind ions are the major sources of the ring current particles. The polar wind and plasmaspheric H+ have only minor impacts. In the storm main phase, the strong penetration of solar wind electric field pushes ions from the geosynchronous orbit to L shells of 2 and below. Ring current is greatly intensified during the earthward transport and produces a large magnetic depression in the surface field. When the convection subsides, the deep penetrating ions experience strong charge exchange loss, causing rapid decay of the ring current and fast initial storm recovery. Our simulation reproduces very well the storm development indicated by the Dst index.

Fok, Mei-Chging; Moore, Thomas

2008-01-01

236

Connecting Soluble Trace Gases and Aerosol Vertical Distributions to Storm Properties  

NASA Astrophysics Data System (ADS)

Wet deposition is important because it removes soluble trace gases and aerosols from the atmosphere, thereby affecting ozone photochemistry, visibility, and potentially the radiation budget of the atmosphere. Wet deposition of chemical constituents not only depends on the solubility of the compound, but also on the storm properties, such as liquid and ice water contents, precipitation production and evaporation, and the ice-to-water partitioning. These storm properties, in turn, depend on the storm dynamics and its thermodynamic environment. We analyze the Deep Convective Clouds and Chemistry (DC3) observations to connect the aircraft measurements of a range of soluble gases (e.g. HNO3, H2O2, HCHO, CH3OOH) to the storm and environment observations. These observations include aircraft measurements of water content, radar reflectivity (including hydrometeor structure), radar vertical velocities, and pre-storm soundings of convective available potential energy and wind shear. We use the 2-component mixture model to estimate scavenging and transport efficiencies. We then compare these efficiencies to various storm properties. Estimates of scavenging efficiencies vary substantially for HCHO (10-84%) for four different thunderstorms ranging from low shear, moderate CAPE to high shear, high CAPE environments. The preliminary scavenging efficiencies for H2O2 for the same four storms are estimated to be all >90%.

Barth, M. C.; Bela, M. M.; Applegate, M.; Fried, A.; Weibring, P.; Hanisco, T. F.; Arkinson, H. L.; Apel, E. C.; O'Sullivan, D. W.; Heikes, B.; Wennberg, P. O.; Crounse, J.; St Clair, J. M.; Nenes, A.; Markovic, M. Z.; Stith, J. L.; Campos, T. L.; Rutledge, S. A.; Basarab, B.; Fuchs, B.; Carey, L. D.; Bain, A. L.; Biggerstaff, M. I.; Wisthaler, A.; Diskin, G. S.; Campuzano Jost, P.; Ryerson, T. B.; Flocke, F. M.; Lance, S.

2013-12-01

237

Dynamics Of Saturn'S Mid-scale Storms In The Cassini Era.  

NASA Astrophysics Data System (ADS)

Convective storms, similar to those in Earth, but of much larger scale, develop often in Saturn's atmosphere. During the Voyagers’ flybys of Saturn in 1981 mid-scale storms, with an horizontal extension of the order of 1000-3000 km were observed to occur mainly in a narrow tropical-latitude band in the Northern hemisphere at latitudes 38-40 deg North. Contrasting with the Voyagers’ era, since the starting of the Cassini mission in 2004, a similar mid-scale convective activity has concentrated in the so-called "storm alley", a narrow band at a symmetric Southern latitude of 38 deg.. In this work, we characterize this storm activity using available visual information provided by Cassini ISS cameras and the continuous survey from the Earth by the International Outer Planets Watch (IOPW) and its online database PVOL (Hueso et al., Planetary and Space Science, 2010). We study the frequency of appearance of storms with sizes above 2000 km, their characteristic size and life-time, as well as their interaction with surrounding dynamical features. In particular we examine the possibility that storms might provide a mechanism of injection of energy into Saturn's jets, the influence of storms in the generation of atmospheric vortices, and the analogies and differences of Voyagers’ and present day jet structure at the relevant latitudes. Acknowledgments: This work has been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464

Del Rio Gaztelurrutia, Teresa; Hueso, R.; Sánchez-Lavega, A.

2010-10-01

238

An Update to the Warm-Season Convective Wind Climatology of KSC/CCAFS  

NASA Technical Reports Server (NTRS)

Total of 1100 convective events in the 17-year warm-season climatology at KSC/CCAFS. July and August typically are the peak of convective events, May being the minimum. Warning and non-warning level convective winds are more likely to occur in the late afternoon (1900-2000Z). Southwesterly flow regimes and wind directions produce the strongest winds. Storms moving from southwesterly direction tend to produce more warning level winds than those moving from the northerly and easterly directions.

Lupo, Kevin

2012-01-01

239

Convective weather hazards in the Twin Cities Metropolitan Area, MN  

NASA Astrophysics Data System (ADS)

This dissertation investigates the frequency and intensity of severe convective storms, and their associated hazards, in the Twin Cities Metropolitan Area (TCMA), Minnesota. Using public severe weather reports databases and high spatial density rain gauge data, annual frequencies and return-periods are calculated for tornadoes, damaging winds, large hail, and flood-inducing rainfall. The hypothesis that severe thunderstorms and tornadoes are less likely in the central TCMA than in surrounding areas also is examined, and techniques for estimating 100-year rainfall amounts are developed and discussed. This research finds that: (i) storms capable of significant damage somewhere within the TCMA recur annually (sometimes multiple times per year), while storms virtually certain to cause such damage recur every 2-3 years; (ii) though severe weather reports data are not amenable to classical comparative statistical testing, careful treatment of them suggests all types and intensity categories of severe convective weather have been and should continue to be approximately as common in the central TCMA as in surrounding areas; and (iii) applications of Generalized Extreme Value (GEV) statistics and areal analyses of rainfall data lead to significantly larger (25-50%) estimates of 100-year rainfall amounts in the TCMA and parts of Minnesota than those currently published and used for precipitation design. The growth of the TCMA, the popular sentiment that downtown areas somehow deter severe storms and tornadoes, and the prior underestimation of extreme rainfall thresholds for precipitation design, all act to enhance local susceptibility to hazards from severe convective storms.

Blumenfeld, Kenneth A.

240

Extreme Precipitation and Climate Change: A Storm's Perspective  

NASA Astrophysics Data System (ADS)

Extreme precipitation events have the potential of causing widespread damage and are a common issue to address for insurance companies. There are many challenges facing the prediction of extreme precipitation events, including the ability to forecast the intensity of the events with high-resolution forecast models and to determine the projected change in these events is in a warmer climate. This talk examines these two challenges from a storm's perspective. The floods during the summer of 2007 in the UK were caused by the presence of a persistent upper-level cut-off low providing a continuous moisture supply over the UK. This allowed the development of a series of convective systems embedded within the synoptic system, causing persistent extreme rainfall for several hours. A 12km and a 4km UK Met Office Limited Area Model (LAM) with ECMWF re-analysis boundary conditions was run to investigate whether the LAM was able to predict the intensities and distribution observed through raingauge and radar data. The results suggest that whilst the large-scale distribution of the rainfall is similar to that observed by the radar, the intensity of the rainfall does not equate to the raingauge observations. This intensity error is not reduced at the higher resolution, however the distribution is improved. The effect on the precipitation of synoptic scale events in a warmer climate has also been investigated. The TRACK software was used to track storms in the ECHAM5 T319 Global Climate Model (GCM) to determine whether the intensity and frequency of such events will change under the IPCC A1B warming scenario. These results were compared to the results from the T213 resolution run presented in Bengtsson et al (2009). The effect of a warming climate is for the number of extreme events to increase, and for the intensity, for the precipitation and vorticity fields, to increase. These are the same conclusions as for the T213 run. The effect of a warmer climate has a consistent response across all the seasons, however the increase in resolution does not have a uniform response across the seasons. The increase in resolution predicts more extreme events, and an increase in the intensity of these events, for precipitation and vorticity, for all seasons and both climates, with the exception of 20C DJF in the precipitation which shows no change due to resolution. This peculiarity in the response of the ECHAM5 model to an increase in resolution has been investigated and the results are given in this talk. Future work relating the increase in the intensity of extreme precipitation events with climate change, and the results from the LAM runs will also be discussed. References: Bengtsson, L, K. Hodges, and N. Keenlyside, 2009: Will Extratropical Storms Intensify in a Warmer Climate? J. Clim., 22, 2276-2301.

Champion, Adrian; Hodges, Kevin; Bengtsson, Lennart

2010-05-01

241

Storm water pollution prevention plans  

SciTech Connect

National Pollutant Discharge Elimination System (NPDES) general permit applications for industrial storm water discharge were to have been filed by October 1992. The Environmental Protection Agency (EPA) and state agencies are now issuing permits based on these applications. One compliance aspect of the permits is the Storm Water Pollution Prevention Plan (SWP3). The plan must identify the facility's potential sources of storm water pollution and develop and implement best management practices (BMPs) to reduce pollutants in storm water runoff. The objectives of the NPDES storm water program are to eliminate illegal dumping and illicit connections, and to reduce pollutants in industrial storm water discharge. These regulations require industry to develop detailed facility site maps, and describe the types, amounts and locations of potential pollutants. Based on this information, industry can develop and implement best management practices to reduce pollutants in storm water runoff.

Rossmiller, R.L. (HDR Engineering, Inc., Bellevue, WA (United States))

1993-03-01

242

Large Eddy Simulations of Severe Convection Induced Turbulence.  

National Technical Information Service (NTIS)

Convective storms can pose a serious risk to aviation operations since they are often accompanied by turbulence, heavy rain, hail, icing, lightning, strong winds, and poor visibility. They can cause major delays in air traffic due to the re-routing of fli...

F. Proctor N. Ahmad

2011-01-01

243

Pilot Convective Weather Decision Making in En Route Airspace  

NASA Technical Reports Server (NTRS)

The present research investigates characteristics exhibited in pilot convective weather decision making in en route airspace. In a part-task study, pilots performed weather avoidance under various encounter scenarios. Results showed that the margins of safety that pilots maintain from storms are as fluid as deviation decisions themselves.

Wu, Shu-Chieh; Gooding, Cary L.; Shelley, Alexandra E.; Duong, Constance G.; Johnson, Walter W.

2012-01-01

244

Slithering into Summer  

ERIC Educational Resources Information Center

The summer provides a unique opportunity for children to further their interests in science, especially science in the out-of-doors. Once school is out for the summer, there is seemingly unlimited time, with no strict curriculum guidelines to follow. For students with a passion for the out-of-doors, summer science camps and school-based summer

Scott, Catherine; Matthews, Catherine

2012-01-01

245

The soundproof dynamical core for COSMO model: representation of convective flows.  

NASA Astrophysics Data System (ADS)

Research conducted at Polish Institute of Meteorology and Water Management, National Research Institute, in collaboration with Consortium for Small Scale Modeling (COSMO) are aimed at developing new conservative dynamical core for next generation operational weather prediction model. As the result, a new prototype model was developed with dynamical core based on anelastic set of equation and numerics adopted from the EULAG model. An employment of EULAG allowed to profit from its desirable conservative properties and numerical robustness confirmed in number of benchmark tests and widely documented in scientific literature. The hybrid model consists of EULAG dynamical core implemented into the software environment of the operational COSMO model and basic COSMO physical parameterizations involving turbulence, friction, radiation, moist processes and surface fluxes (COSMO-EULAG). The tool is capable to compute weather forecast in mountainous area for the horizontal resolution of 0.28 km and with slopes reaching 60 degrees of inclination. The presentation is focused on two current research topics. First, the model and especially its dynamics-physics coupling is examined within idealized framework for representation of convective flows. The study is based on two complementary convection benchmarks of Weisman and Klemp (Mon. Wea. Rev. 110:504, 1982) and Grabowski et al. (Q. J. R. Meteorol. Soc. 132:317, 2006). While the first experiment can be used to examine a life cycle of a single convective storm structure in COSMO-EULAG model, the second experiment allows to evaluate the model representation of statistical properties of daytime convective development over land, involving convection initiation as well as is transition into a deep phase. The study involves also the comparison of COSMO-EULAG results with results of standard compressible COSMO-Runge-Kutta model to test the suitability of the anelastic dynamical core for operational mesoscale high-resolution NWP. Next, the results of a realistic case study of Alpine summer convection simulated by COSMO-EULAG with very high horizontal resolutions ranging from 2.2 to 0.28km are presented. While the simulations, even with highest resolution, do not require any artificial orography smoothing, the influence of such smoothing on simulation results is investigated. The study shows e.g. a comparison of flow, cloud and precipitation structure, and spectral analyses of horizontal wind fields. The Cosmo-Eulag forecast is also compared with available meteorological information.

Wójcik, Damian; Piotrowski, Zbigniew; Rosa, Bogdan; Ziemia?ski, Micha?

2014-05-01

246

Peace at Storm King  

SciTech Connect

Energy and environmental interests clashed for two decades before agreement was reached on a proposed Storm King Mountain pumped storage plant on the Hudson River. Intervenors argued that scenic beauty, fishing interests, and other environmental qualities were in jeopardy. A compromise settlement mediated by Russel Train, former EPA administrator, required concession on both sides. The utilities will halt construction on the Hudson, take specific steps to protect fish, and endow a foundation to study power plant impacts. Consolidated Edison will donate the Storm King site as a park. In compensation, cooling towers will not be required on closed-cell systems. The compromise has economic as well as environmental benefits. It illustrates how negotiation and mediation can lead to effective and acceptable alternatives. (DCK)

Temple, T.

1981-02-01

247

Severe storm electricity  

NASA Technical Reports Server (NTRS)

Successful ground truth support of U-2 overflights was been accomplished. Data have been reduced for 4 June 1984 and some of the results have been integrated into some of MSFC's efforts. Staccato lightning (multiply branched, single stroke flash with no continuing current) is prevalent within the rainfree region around the main storm updraft and this is believed to be important, i.e., staccato flashes might be an important indicator of severe storm electrification. Results from data analysis from two stations appear to indicate that charge center heights can be estimated from a combination of intercept data with data from the fixed laboratory at NSSL. An excellent data base has been provided for determining the sight errors and efficiency of NSSL's LLP system. Cloud structures, observable in a low radar reflectivity region and on a scale smaller than is currently resolved by radar, which appear to be related to electrical activity are studied.

Arnold, R. T.; Rust, W. D.

1984-01-01

248

Dust Storm, Aral Sea  

NASA Technical Reports Server (NTRS)

The Aral Sea has shrunk to less than half its size since 1985. The Aral Sea receives little water (sometimes no water) from the two major rivers that empty into it-the Syr Darya and Amu Darya. Instead, the river water is diverted to support irrigation for the region's extensive cotton fields. Recently, water scarcity has increased due to a prolonged drought in Central Asia. As the Aral Sea recedes, its former sea bed is exposed. The Aral's sea bed is composed of fine sediments-including fertilizers and other agricultural chemicals-that are easily picked up by the region's strong winds, creating thick dust storms. The International Space Station crew observed and recorded a large dust storm blowing eastward from the Aral Sea in late June 2001. This image illustrates the strong coupling between human activities (water diversions and irrigation), and rapidly changing land, sea and atmospheric processes-the winds blow across the

2002-01-01

249

Oxidant Enhancement in Martian Dust Devils and Storms: Storm Electric Fields and Electron Dissociative Attachment  

NASA Astrophysics Data System (ADS)

Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity." In convective structures such as dust devils and dust storms, grain stratification leads to macroscopic charge separations and gives rise to an overall electric dipole moment in the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous numerical simulations indicate that these storm electric fields on Mars can approach the ambient breakdown field strength of ~25 kV/m. In terrestrial dust phenomena, potentials ranging from ~20 to 160 kV/m have been directly measured. The large electrostatic fields predicted in martian dust devils and storms can energize electrons in the low pressure martian atmosphere to values exceeding the electron dissociative attachment energy of both CO2 and H2O, which results in the formation of the new chemical products CO/O and OH/H, respectively. Using a collisional plasma physics model, we present calculations of the CO/O and OH/H reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach the breakdown value of ~25 kV/m. The dissociation of H2O into OH/H provides a key ingredient for the generation of oxidants; thus electrically charged dust may significantly impact the habitability of Mars.

Delory, Gregory T.; Farrell, William M.; Atreya, Sushil K.; Renno, Nilton O.; Wong, Ah-San; Cummer, Steven A.; Sentman, Davis D.; Marshall, John R.; Rafkin, Scot C. R.; Catling, David C.

2006-06-01

250

Defining Coastal Storm and Quantifying Storms Applying Coastal Storm Impulse Parameter  

NASA Astrophysics Data System (ADS)

What defines a storm condition and what would initiate a "storm" has not been uniquely defined among scientists and engineers. Parameters that have been used to define a storm condition can be mentioned as wind speed, beach erosion and storm hydrodynamics parameters such as wave height and water levels. Some of the parameters are storm consequential such as beach erosion and some are not directly related to the storm hydrodynamics such as wind speed. For the purpose of the presentation, the different storm conditions based on wave height, water levels, wind speed and beach erosion will be discussed and assessed. However, it sounds more scientifically to have the storm definition based on the hydrodynamic parameters such as wave height, water level and storm duration. Once the storm condition is defined and storm has initiated, the severity of the storm would be a question to forecast and evaluate the hazard and analyze the risk in order to determine the appropriate responses. The correlation of storm damages to the meteorological and hydrodynamics parameters can be defined as a storm scale, storm index or storm parameter and it is needed to simplify the complexity of variation involved developing the scale for risk analysis and response management. A newly introduced Coastal Storm Impulse (COSI) parameter quantifies storms into one number for a specific location and storm event. The COSI parameter is based on the conservation of linear, horizontal momentum to combine storm surge, wave dynamics, and currents over the storm duration. The COSI parameter applies the principle of conservation of momentum to physically combine the hydrodynamic variables per unit width of shoreline. This total momentum is then integrated over the duration of the storm to determine the storm's impulse to the coast. The COSI parameter employs the mean, time-averaged nonlinear (Fourier) wave momentum flux, over the wave period added to the horizontal storm surge momentum above the Mean High Water (MHW) integrated over the storm duration. The COSI parameter methodology has been applied to a 10-year data set from 1994 to 2003 at US Army Corps of Engineers, Field Research Facility (FRF) located on the Atlantic Ocean in Duck, North Carolina. The storm duration was taken as the length of time (hours) that the spectral significant wave heights were equal or greater than 1.6 meters for at least a 12 hour, continuous period. Wave heights were measured in 8 meters water depth and water levels measured at the NOAA/NOS tide gauge at the end of the FRF pier. The 10-year data set were analyzed applying the aforementioned storm criteria and produced 148 coastal events including Hurricanes and Northeasters. The results of this analysis and application of the COSI parameter to determine "Extra Ordinary" storms in Federal Projects for the Gulf of Mexico, 2012 hurricane season will be discussed at the time of presentation.

Mahmoudpour, Nader

2014-05-01

251

PROJECT STORM 2 - A \\  

Microsoft Academic Search

With a projected 20-year wastewater capex programme of over $1.4B, an annual wastewater tariff of $90M and a projected 20-year growth in population of over 30%, a sophisticated asset planning tool for supporting infrastructure decision making is vital to Watercare. Watercare's first dynamic wastewater network model, created in 1997 during Project Storm, was at the time the largest and most

Geoff Milsom; David Ward; Darren Wilson

252

Ice Storm Supercomputer  

SciTech Connect

"A new Idaho National Laboratory supercomputer is helping scientists create more realistic simulations of nuclear fuel. Dubbed 'Ice Storm,' this 2048-processor machine allows researchers to model and predict the complex physics behind nuclear reactor behavior. And with a new visualization lab, the team can see the results of its simulations on the big screen." For more information about INL research, visit http://www.facebook.com/idahonationallaboratory.

None

2009-01-01

253

Investigating Magnetic Storms  

NSDL National Science Digital Library

In this activity, students use an internet archive of data on the Earth's magnetic field to study the frequency of magnetic storms of different intensities during the year, and during the solar sunspot cycle. The archive contains values of the Kp scale, an index of how disturbed the Earth's magnetic field was, on average, over each three-hour period of the day. They will select their data, construct a bar graph with it, and answer questions on what their data reveals.

Odenwald, Sten

254

Development in the STORM  

PubMed Central

The recent invention of super-resolution microscopy has brought up much excitement in the biological research community. Here, we will focus on Stochastic Optical Reconstruction Microscopy/Photoactivated Localization Microscopy (STORM/PALM) to discuss the challenges in applying super-resolution microscopy to the study of developmental biology, including tissue imaging, sample preparation artifacts, and image interpretation. We will also summarize new opportunities that super-resolution microscopy could bring to the field of developmental biology.

Kamiyama, Daichi; Huang, Bo

2012-01-01

255

Ice Storm Supercomputer  

ScienceCinema

"A new Idaho National Laboratory supercomputer is helping scientists create more realistic simulations of nuclear fuel. Dubbed 'Ice Storm,' this 2048-processor machine allows researchers to model and predict the complex physics behind nuclear reactor behavior. And with a new visualization lab, the team can see the results of its simulations on the big screen." For more information about INL research, visit http://www.facebook.com/idahonationallaboratory.

None

2013-05-28

256

Horizontal Convection  

NASA Astrophysics Data System (ADS)

Horizontal convection, caused by differential heating along the horizontal boundary of a fluid, is a model of the meridional overturning circulation of the oceans. We explore aspects of horizontal convection using laboratory experiments. We use salt rather than heat, with sinks and sources of dense and fresh water on the upper boundary of the tank so that the net flux of salt into the tank is statistically zero. We measure the density using the Synthetic Schlieren method and a conductivity probe, and dye the incoming fluid and measure its concentration using optical methods. We also use particle tracking to visualize the velocity field within the tank. Our goal is to examine the role of the aspect ratio and governing dimensionless parameters of the system, as well as the effect of the location of sources and sinks, and relate these to features of the flow such as boundary-layer thickness and net overturning circulation. The use of salt rather than temperature results in a high Schmidt number, with implications for the understanding of the experiments and their relation to the ocean.

Matusik, Katarzyna; Smith, Stefan Llewellyn

2010-11-01

257

Oxidant Enhancement in the Martian dust devils and Storms: I. Storm electric fields and electron dissociative attachment  

NASA Astrophysics Data System (ADS)

Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity". In convective structures such as dust devils or dust storms, grain stratification (leading to charge separation) gives rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies indicate that this storm electric field on Mars can approach the ambient breakdown field strength of 20 kV/m. In terrestrial dust devils, coherent dipolar electric fields have been measured near 20 kV/m. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via the fields to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model, we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach breakdown levels 20-30 kV/m. These storm-related chemical products are key ingredients for the generation of oxidants which can ultimately affect the habitability of Mars, as discussed in the following presentation.

Delory, G. T.; Farrell, W. M.; Sentman, D. D.; Renno, N. O.; Atreya, S. K.; Wong, A.-S.; Cummer, S. A.; Marshall, J. R.; Rafkin, S. C. R.; Catling, D.

2004-11-01

258

Doppler Radar Methodology for the Observation of Convective Storms.  

National Technical Information Service (NTIS)

The paper is an attempt to outline the practical concepts and limitations involved in the dual-Doppler radar method. COPLAN scanning is a substantial improvement of the method, offering major advantages such as: shorter time requirement for stationarity o...

R. M. Lhermitte L. J. Miller

1970-01-01

259

EVALUATION OF IKONOS SATELLITE IMAGERY FOR DETECTING ICE STORM DAMAGE TO OAK FORESTS IN EASTERN KENTUCKY  

Microsoft Academic Search

Ice storms are a recurring landscape-scale disturbance in the eastern U.S. where they may cause varying levels of damage to upland hardwood forests. High-resolution Ikonos imagery and semi- automated detection of ice storm damage may be an alternative to manually interpreted aerial photography. We evaluated Ikonos multispectral, winter and summer imagery as a tool for detecting forest canopy damage to

W. Henry McNab; Tracy Roof; Jeffrey F. Lewis

260

Evolving dominant charge structures during upscale storm growth in West Texas on 4 June 2012  

NASA Astrophysics Data System (ADS)

The Deep Convective Cloud Chemistry (DC3) field campaign occurred from 15 May and 30 June 2012 with a primary goal of understanding the source of oxides of nitrogen (NOx) in the upper atmosphere due to lightning. In order to better understand this effect, it is necessary to better understand how the local environment can impact the polarity of the lightning in a storm. If polarity changes are driven by changes in electrification mechanisms, changes to the vertical distribution of the lightning channels and NOx source may result. One of the regions participating in DC3 extended from west Texas into central Oklahoma, where an arrangement of three Lightning Mapping Arrays (LMA) allowed for continuous analysis of electrification processes as storms moved across the region and through different local environments. On 4 June 2012 isolated storms initiated within range of the West Texas LMA and generated a mesoscale convective system, part of which dissipated over the West Texas LMA and Southwest Oklahoma LMA domains overnight. Initial storm cells developed within a relatively dry mid-level environment and were observed to contain a mid-level positive charge. However, later storm cells, both further east in deeper moisture and within areas that had previously been moistened by convection, were primarily observed to contain a mid-level negative charge. This presentation will detail the transition from initial discrete storm cells with mid-level positive charge regions and predominantly -IC flashes, to increased cellular coverage with a mixture of charge structures, to longer-lived multicellular clusters dominated by mid-level negative charge and +ICs at upper levels in the storm. These charge structures will be compared to proposed controls on storm electrification, including moisture variability in the mid-troposphere and its relationship to depletion of cloud liquid water.

Sullivan, V. C.; Bruning, E. C.; MacGorman, D. R.; Krehbiel, P. R.; Rison, W.; Edens, H. E.

2013-12-01

261

Effects of cumulus convection on the simulated monsoon circulation in a general circulation model  

SciTech Connect

The effect of cumulus convection on the Asian summer monsoon circulation is investigated, using a general circulation model. Two simulations for the summer months (June, July, and August) are performed, one parameterizing convection using a mass flux scheme and the other without convective parameterization. The results show that convection has significant effects on the monsoon circulation and its associated precipitation. In the simulation with the mass flux convective parameterization, precipitation in the western Pacific is decreased, together with a decrease in surface evaporation and wind speed. In the indian monsoon region it is almost the opposite. Comparison with a simulation using moist convective adjustment to parameterize convection shows that the monsoon circulation and precipitation distribution in the no-convection simulation are very similar to those in the simulation with moist convective adjustment. The difference in the large-scale circulation with and without convective parameterization is interpreted in terms of convective stabilization of the atmosphere by convection, using dry and moist static energy budgets. It is shown that weakening of the low-level convergence in the western Pacific in the simulation with convection is closely associated with the stabilization of the atmosphere by convection, mostly through drying of the lower troposphere; changes in low-level convergence lead to changes in precipitation. The precipitation increase in the Indian monsoon can be explained similarly. 29 refs., 12 figs.

Zhang, Guang Jun (Univ. of California, San Diego, La Jolla, CA (United States))

1994-09-01

262

Multisensor Investigation of Deep Convection  

NASA Astrophysics Data System (ADS)

The array of sensors for studying cloud systems from space provides the opportunity to globally map the occurrence of various types of deep convective cloud systems more precisely than ever before. The revolutionary TRMM satellite has not only determined rainfall from space but also identified the structures of storms producing the rainfall and how the different types of convective structures relate to features of the global circulation. The multiple sensors of the A-Train constellation have added more capacity to globally map convective cloud system types. By simultaneously using Aqua's MODIS 11-micron brightness temperature sensor to map cloud-top size and coldness, Aqua's AMSR-E passive microwave to detect rainfall, and CloudSat's cloud radar observations to see the internal structure of the nonprecipitating anvil clouds extending laterally from the precipitating cores of mesoscale convective systems (MCSs), we have objectively identified and mapped different types of MCSs. This multisensor analysis has determined the degrees to which MCSs vary according to size, amount of anvil cloud, and whether or not they occur separately or in merged complexes. Using these multisensor-derived quantities, we have established the patterns in which tropical MCSs occur over land, ocean, or the maritime continent. Ongoing work is integrating more sensors and other innovative global datasets into the analysis of A-Train data to further knowledge of MCSs and their variability over the Earth. Global lightning data are being integrated with the A-Train data to better understand convective intensity in different types of MCSs. Environments of the MCSs identified by multisensor A-Train analysis are being further analyzed using AIRS temperature profiles and MODIS and CALIPSO aerosol fields to better document the influence of environmental properties on the different types of mesoscale system. The integration of aerosol loading into the global analysis of the patterns of occurrence of deep convective system identified by multisensor analysis is especially important, as it will be the first truly global assessment of aerosol on the largest atmospheric convective systems. Although we are learning a lot about global patterns of deep MCSs from these multisensor studies, there remains a difficulty. Although the TRMM and A-Train satellite programs are both leading to exciting new information on the global patterns of deep convection and its organization into important mesoscale cloud entities, the knowledge gained from these two satellite programs is difficult to integrate in the quest for a more complete and holistic understanding of deep convection over the Earth. The A-Train data are showing in unprecedented detail aspects of the entire cloud system, and they have the powerful ability to separate the raining cores of the cloud systems from their nonprecipitating anvil clouds. However, the A-Train data lack three-dimensional details on the structure and type of convection. The TRMM radar on the other hand shows the detailed embedded structure of the precipitation cores but lacks information on the nonprecipitating cloud components. Future satellite programs should perhaps focus on how sensors detecting the precipitating components of deep convective cloud systems can be more simultaneously determining information from cloud radars and lidars that best show the nonprecipitating components of the cloud systems.

Houze, R.; Yuan, J.; Barnes, H. C.; Brodzik, S. R.

2012-12-01

263

TRMM precipitation analysis of extreme storms in South America: Bias and climatological contribution  

NASA Astrophysics Data System (ADS)

The TRMM (Tropical Rainfall Measuring Mission) satellite was designed both to measure spatial and temporal variation of tropical rainfall around the globe and to understand the factors controlling the precipitation. TRMM observations have led to the realization that storms just east of the Andes in southeastern South America are among the most intense deep convection in the world. For a complete perspective of the impact of intense precipitation systems on the hydrologic cycle in South America, it is necessary to assess the contribution from various forms of extreme storms to the climatological rainfall. However, recent studies have suggested that the TRMM Precipitation Radar (PR) algorithm significantly underestimates surface rainfall in deep convection over land. Prior to investigating the climatological behavior, this research first investigates the range of the rain bias in storms containing four different types of extreme radar echoes: deep convective cores, deep and wide convective cores, wide convective cores, and broad stratiform regions over South America. The TRMM PR algorithm exhibits bias in all four extreme echo types considered here when the algorithm rates are compared to a range of conventional Z-R relations. Storms with deep convective cores, defined as high reflectivity echo volumes that extend above 10 km in altitude, show the greatest underestimation, and the bias is unrelated to their echo top height. The bias in wide convective cores, defined as high reflectivity echo volumes that extend horizontally over 1,000 km2, relates to the echo top, indicating that storms with significant mixed phase and ice hydrometeors are similarly affected by assumptions in the TRMM PR algorithm. The subtropical region tends to have more intense precipitating systems than the tropics, but the relationship between the TRMM PR rain bias and storm type is the same regardless of the climatological regime. The most extreme storms are typically not collocated with regions of high climatological precipitation. A quantitative approach that accounts for the previously described bias using TRMM PR data is employed to investigate the role of the most extreme precipitating systems on the hydrological cycle in South America. These data are first used to investigate the relative contribution of precipitation from the TRMM-identified echo cores to each separate storm in which the convective cores are embedded. The second part of the study assesses how much of the climatological rainfall in South America is accounted for by storms containing deep convective, wide convective, and broad stratiform echo components. Systems containing these echoes produce very different hydrologic responses. From a hydrologic and climatological viewpoint, this empirical knowledge is critical, as the type of runoff and flooding that may occur depends on the specific character of the convective storm and has broad implications for the hydrological cycle in this region.

Rasmussen, K. L.; Houze, R.; Zuluaga, M. D.; Choi, S. L.; Chaplin, M.

2013-12-01

264

Features of ionospheric O+ ion upflowing during great magnetic storms  

NASA Astrophysics Data System (ADS)

With coordinate data analysis of in-situ satellite FAST measurements of particles (EES, IES, TEAMS) and fields (DCF), POLAR EUV image of aurora, along with EISCAT/ESR radar observations, an investigation is made on the features of O+ up-flowing versus MLT, ILAT and storm phases for 8 major magnetic storms with minimum Dst less than -200nT during 1998-2001. Attention is also paid to the relationships between large O+ up-flowing fluxes with strong soft electron precipitation, convection shear and field- aligned currents, respectively. It is found that strong O+ up-flowing occur during both of main and recovery phase of magnetic storms, with larger integrated fluxes during recovery phase than main phase, though the largest differential fluxes appear mostly during the main phases. Dayside cusp/cleft is a very important region of storm-time ionospheric O+ up-flowing, but not the unique dominant one. The latitude-integrated fluxes with energy less than 1 keV show statistically a prominent peak around 06:00 MLT, suggesting a very important contribution of out-flowing energetic oxygen O+ from dawn sector ionosphere to storm-time ring currents. The observed events of strong O+ up-flowing are mostly associated with concurrent large convection shear, field-aligned currents and strong precipitation of soft electrons at adjacent areas. Most of O+ upflow bursts occur near the poleward edge of strong aurora activity region, mapping into magnetospheric boundary layers, such as LLBL, BPS, cusp/cleft etc.

Ma, S. Y.; Dang, G.; Zhou, Y. L.; Schlegel, K.

265

Monitoring and automatic detection of the cold-ring patterns atop deep convective clouds using Meteosat data  

NASA Astrophysics Data System (ADS)

This paper presents a newly established database of deep convective storms that exhibit a cold ring at their cloud top, as observed in enhanced infrared (IR) window satellite imagery. The database consists of cold-ring patterns as seen on the Meteosat data over the summer period between 2006 and 2010 for Slovenia and parts of Italy, Austria, Hungary and Croatia. It includes 139 cold rings at different stages, where typically large hail was reported on the ground and as such it serves as an important source of information for any quantitative analysis of the cold rings in this region. The typical characteristics of cold rings in this database are presented and discussed. It was found that the median of the difference between the minimum brightness temperature in the cold ring and the maximum brightness temperature in the central warm spot is 7.1 K, and that the median distance between such pair is 27 km. In addition, the paper presents in detail a new objective satellite-based method for cold-ring or cold-U/V pattern detection on storm tops in infrared imagery. This method uses a combination of infrared brightness temperature from the Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI) and the tropopause temperatures from radiosonde measurements. The method was built and evaluated on the cold-ring patterns from the presented database.

Žibert, Mateja Irši?; Žibert, Janez

2013-04-01

266

Use of the Aerosonde Unihabited Aerial Vehicle (UAV) in the Fourth Convection and Moisture Experiment (CAMEX 4)  

NASA Technical Reports Server (NTRS)

The Fourth Convection and Moisture Experiment (CAMEX 4) was a scientific field experiment based in Florida in summer 2001 focused on the study of hurricanes off the east coast of the United States. Sponsored by the National Aeronautics and Space Administration's Office of Earth Science, and conducted in collaboration with the National Oceanic and Atmospheric Administration's annual hurricane research program, CAMEX 4 utilized aircraft, ground-based and satellite instrumentation to obtain unprecedented, three dimensional characterizations of these important storms. The Aerosonde UAV was selected by NASA to participate in CAMEX 4 because it provided a unique capability to obtain measurements in the atmospheric boundary layer in and around the storms, unattainable by other platforms or measurement capabilities. This talk focuses on the NASA review process that was followed to coordinate the UAV activity with the conventional aircraft operations, as well as with the other participating agencies and the FAA. We will discuss how Aerosonde addressed the issues of safety, coordination and communication and summarize the lessons learned.

Hipskind, R. Stephen; Curry, Judy; Holland, Greg

2001-01-01

267

Methane storms on Saturn's moon Titan.  

PubMed

The presence of dry fluvial river channels and the intense cloud activity in the south pole of Titan over the past few years suggest the presence of methane rain. The nitrogen atmosphere of Titan therefore appears to support a methane meteorological cycle that sculptures the surface and controls its properties. Titan and Earth are the only worlds in the Solar System where rain reaches the surface, although the atmospheric cycles of water and methane are expected to be very different. Here we report three-dimensional dynamical calculations showing that severe methane convective storms accompanied by intense precipitation may occur in Titan under the right environmental conditions. The strongest storms grow when the methane relative humidity in the middle troposphere is above 80 per cent, producing updrafts with maximum velocities of 20 m s(-1), able to reach altitudes of 30 km before dissipating in 5-8 h. Raindrops of 1-5 mm in radius produce precipitation rainfalls on the surface as high as 110 kg m(-2) and are comparable to flash flood events on Earth. PMID:16871212

Hueso, R; Sánchez-Lavega, A

2006-07-27

268

The UAE Rainfall Enhancement Assessment Program: Implications of Thermodynamic Profiles on the Development of Precipitation in Convective Clouds over the Oman Mountains  

NASA Astrophysics Data System (ADS)

During the winter and summer seasons of 2001 and 2002, data were collected to assess the efficacy of cloud seeding to enhance precipitation in the United Arab Emirates (UAE). The results of the feasibility study concluded: 1) that winter clouds in the UAE rarely produced conditions amenable to hygroscopic cloud seeding; 2) that summer convective clouds developed often enough, particularly over the Oman Mountains (e.g., the Hajar Mountains along the eastern UAE border and into Oman) to justify a randomized seeding experiment; 3) that collecting quantitative radar observations continues to be a complex but essential part of evaluating a cloud seeding experiment; 4) that successful flight operations would require solving several logistical issues; and 5) that several scientific questions would need to be studied in order to fully evaluate the efficacy and feasibility of hygroscopic cloud seeding, including cloud physical responses, radar-derived rainfall estimates as related to rainfall at the ground, and hydrological impacts. Based on these results, the UAE program proceeded through the design and implemention of a randomized hygroscopic cloud seeding experiment during the summer seasons to statistically quantify the potential for cloud seeding to enhance rainfall, specifically over the UAE and Oman Mountains, while collecting concurrent and separate physical measurements to support the statistical results and provide substantiation for the physical hypothesis. The randomized seeding experiment was carried out over the summers of 2003 and 2004, and a total of 134 cases were treated over the two summer seasons, of which 96 met the analysis criteria established in the experimental design of the program. The statistical evaluation of these cases yielded largely inconclusive results. Evidence will show that the thermodynamic profile had a large influence on storm characteristics and on precipitation development. This in turn provided a confounding factor in the conduct of the seeding experiment, particularly in the lateness of treatment in the storm cycle. The prevalence of capping inversions and the sensitivity of clouds to the level of the inversions as well as to wind shear will be shown using several data sets (soundings, aircraft, radar, numerical models). Concurrent physical measurements with the randomized experiment provided new insights into the physical processes of precipitation that developed in summertime convective clouds over the UAE that in turn helped in the interpretation of the statistical results.

Breed, D.; Bruintjes, R.; Jensen, T.; Salazar, V.; Fowler, T.

2005-12-01

269

Convective heater  

DOEpatents

A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation. 14 figs.

Thorogood, R.M.

1983-12-27

270

Convective heater  

DOEpatents

A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

Thorogood, Robert M. (Macungie, PA)

1986-01-01

271

Convective heater  

DOEpatents

A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

Thorogood, Robert M. (Macungie, PA)

1983-01-01

272

A numerical simulation of thermal convection in the Martian lower atmosphere with a two-dimensional anelastic model.  

NASA Astrophysics Data System (ADS)

We have examined the wind velocity and the surface stress associated with thermal convection in dust free Martian atmosphere by using a two-dimensional numerical model. Outbreak of dust storm is a striking phenomenon in the Martian atmosphere. However, it has been well recognized that the Martian general circulation model (GCM) does not produce sufficient surface wind stress to raise dust from the surface under dust free condition. Small-scale wind fluctuations which are not represented in GCM may supplement the necessary surface stress. Daily thermal convection is one of the possible contributers. The numerical model is an two-dimensional anelastic model with radiative and surface processes. The computational domain extends horizontally to 51.2 km and vertically to the height of 20 km. Both the horizontal and vertical grid intervals are 100 m except in the lowermost 100 m, where the vertical resolution is enhanced. The solar flux at the top of the model atmosphere changes diurnally with the northern summer condition (Ls=100° ) at 20° N latitude. The model is integrated for 6 days, and the data of the last day is utilized for analyses. The results of the simulation reveal that the thermal convection in the Martian lower atmosphere is km-size; the vertical and horizontal scales of convective cells are 10 km and several km, respectively. The magnitude of wind velocity associated with the km-size thermal convection is quite large. The values of both horizontal and vertical wind velocity often exceeds 20 m/sec. This magnitude can be understood by considering that the work done by the buoyancy force on a plume (about 2 K higher than the surroundings) is converted to the kinetic energy. The instantaneous maximum value of the surface stress associated with the km-size thermal convection reaches 0.04 Pa, which is equal to the threshold value to raise dust from the surface. The result suggests that GCM can represent dust injection into the Martian atmosphere self-consistently by parameterizing the wind fluctuation associated with the km-size thermal convection in the calculation of surface stress.

Odaka, M.; Nakajima, K.; Ishiwatari, M.; Hayashi, Y.

2001-12-01

273

Empirical STORM-E model: I. Theoretical and observational basis  

NASA Astrophysics Data System (ADS)

Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region peak electron densities. The empirical model is called STORM-E and will be incorporated into the 2012 release of the International Reference Ionosphere (IRI). The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) volume emission rates (VER) derived from the TIMED/SABER 4.3 ?m channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 ?m VER is sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 ?m VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. Part II of this series describes the explicit development of the empirical storm-time correction factor for E-region peak electron densities, and shows comparisons of E-region electron densities between STORM-E predictions and incoherent scatter radar measurements. In this paper, Part I of the series, the efficacy of using SABER-derived NO+(v) VER as a proxy for the E-region response to solar-geomagnetic disturbances is presented. Furthermore, a detailed description of the algorithms and methodologies used to derive NO+(v) VER from SABER 4.3 ?m limb emission measurements is given. Finally, an assessment of key uncertainties in retrieving NO+(v) VER is presented.

Mertens, Christopher J.; Xu, Xiaojing; Bilitza, Dieter; Mlynczak, Martin G.; Russell, James M.

2013-02-01

274

Empirical STORM-E Model. [I. Theoretical and Observational Basis  

NASA Technical Reports Server (NTRS)

Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region peak electron densities. The empirical model is called STORM-E and will be incorporated into the 2012 release of the International Reference Ionosphere (IRI). The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) volume emission rates (VER) derived from the TIMED/SABER 4.3 lm channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 lm VER is sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 lm VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. Part II of this series describes the explicit development of the empirical storm-time correction factor for E-region peak electron densities, and shows comparisons of E-region electron densities between STORM-E predictions and incoherent scatter radar measurements. In this paper, Part I of the series, the efficacy of using SABER-derived NO+(v) VER as a proxy for the E-region response to solar-geomagnetic disturbances is presented. Furthermore, a detailed description of the algorithms and methodologies used to derive NO+(v) VER from SABER 4.3 lm limb emission measurements is given. Finally, an assessment of key uncertainties in retrieving NO+(v) VER is presented

Mertens, Christopher J.; Xu, Xiaojing; Bilitza, Dieter; Mlynczak, Martin G.; Russell, James M., III

2013-01-01

275

Forecasting Dust Storms - Version 2  

NSDL National Science Digital Library

This resource provides background and operational information about dust storms. The first part of the module describes dust source regions, the life cycle of a dust storm, and the major types of dust storms, particularly those found in the Middle East. The second part presents a process for forecasting dust storms and applies it to a case in the Middle East. Although the process refers to U.S. Department of Defense models and tools, it can easily be adapted to other forecast requirements and data sources. Note that this module is an updated version of the original one published in 2003 and is available in Spanish. Registration is required.

2010-12-22

276

Storm Tracks Across Eastern Canada  

NASA Astrophysics Data System (ADS)

The global storm tracks patterns across the Northern Hemisphere are well documented, but their regional impact on populations has yet to be characterized, as very few studies took a local perspective on storm tracks. In this study, a Lagrangian tracking algorithm is applied to the 850 hPa relative vorticity field to characterize extratropical storm tracks that pass through major cities in Canada. Storm tracks are first classified in reference to the metropolitan cities that they impact, such as Toronto, Montreal, Halifax and St-John's. They are then subjected to several analyses, including but not limited to the identification of main development regions, typical tracks, mean growth rate, intensity and typical regions of decay. We found that the preferential development regions are the lee of the Rockies, the Great Lakes and the Western Atlantic. The collection of storm tracks across each city is composed of storms developing not from a single development region, but from several. Results show that the storm track variability at a city is dominated by the storm track variability of its predominant development region. Among others, we found that the ensembles of storms crossing East coast cities (Halifax, St-John's) are dominated by Atlantic storms that are most frequent during the winter. Storms passing through Montreal and Toronto travel primarily from the Great Lakes and the mid-latitude Rockies. In eastern Canada, storms from the southernmost part of the Rockies are much less frequent, but this development region is the main source of extreme storms, and is thus important in terms of impacts on metropolitan areas. The relationship between storm tracks and modes of atmospheric variability are also examined with an emphasis on the El Nino Southern Oscillation (ENSO) and Northern Annular Mode (NAM). We found that teleconnection shifts storm tracks differently in different development regions. The anomalous storm track densities are presented, as well as their direct impact on specific metropolitan areas. Results show that the combination of these shifts impact cities differently according to their geographic location.

Plante, Mathieu; Son, Seok-Woo; Gyakum, John; Kevin, Grise

2013-04-01

277

Role of wetlands in attenuation of storm surges using coastal circulation model (ADCIRC), Chesapeake Bay region  

NASA Astrophysics Data System (ADS)

The Chesapeake Bay, Virginia is subject to storm surge from extreme weather events nearly year-round; from tropical storms and hurricanes during the summer and fall, (e.g., hurricanes Isabel [2003] and Sandy [2012]), and from nor'easters during the winter (e.g., winter storms Nemo and Saturn [2013]). Coastal wetlands can deliver acute fortification against incoming hurricane storm surges. Coastal wetlands and vegetation shape the hydrodynamics of storm surge events by retaining water and slowing the propagation of storm surge, acting as a natural barrier to flooding. Consequently, a precise scheme to quantify the effect of wetlands on coastal surge levels was also prerequisite. Two wetland sites were chosen in the Chesapeake Bay region for detailed cataloging of vegetation characteristics, including: height, stem diameter, and density. A framework was developed combining these wetlands characterizations with numerical simulations. Storms surges were calculated using Coastal circulation model (ADCIRC) coupled to a wave model (SWAN) forced by an asymmetric hurricane vortex model using an unstructured mesh (comprised of 1.8 million nodes) under a High Performance Computing environment. The Hurricane Boundary Layer (HBL) model was used to compute wind and pressure fields for historical tropical storms and for all of the synthetic storms. Wetlands were characterized in the coupled numerical models by bathymetric and frictional resistance. Multiple model simulations were performed using historical hurricane data and hypothetical storms to compare the predicted storm surge inundation resulting from various levels of wetlands expansion or reduction. The results of these simulations demonstrate the efficacy of wetlands in storm surge attenuation and also the outcome will scientifically support planning of wetlands restoration projects with multi-objective benefits for society.

Deb, Mithun; Ferreira, Celso; Lawler, Seth

2014-05-01

278

Superposed epoch analysis of ion temperatures during CIR/HSS-driven storms  

NASA Astrophysics Data System (ADS)

Ion temperatures in the plasma sheet influence the development of the ring current. The variation of ion temperatures in the magnetosphere during geomagnetic storms depends on the storm driver. While the magnitude of storms driven by corotating interaction regions and the associated high speed streams (CIR/HSS), as measured by Dst index, tends to be smaller than that for CME-driven storms, significant ion heating occurs during these storms. The TWINS Mission provides a global view of the magnetosphere with continuous temporal coverage provided by two satellites. Ion temperature images with spatial and temporal resolution can be calculated from the energetic neutral atom (ENA) data provided by the satellites. Using this technique, we have found that ion temperatures increase throughout the recovery phase of CIR/HSS-driven storms. Denton and Borovsky [2008] performed a superposed epoch analysis of CIR/HSS-driven storms and found that ion heating begins at convection onset, as measured by the midnight boundary index (MBI). We present superposed epoch analysis results of ion temperature evolution during CIR/HSS-driven storms using both the minimum in the Sym-H index and the MBI for comparison.

Keesee, A. M.; Scime, E. E.

2013-05-01

279

Extreme convection in subtropical South America: TRMM observations and high-resolution modeling  

NASA Astrophysics Data System (ADS)

Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. Measurements from the TRMM satellite have allowed for detailed analysis of extreme weather patterns in remote regions of the world, such as subtropical South America. An investigation of the most intense storms for 11 years of TRMM Precipitation Radar (PR) data has shown a tendency for squall lines to initiate and develop in this region. The synoptic environment and mechanisms leading to extreme convection and MCSs in subtropical South America are similar to those found in other regions of the world, including the United States. The mesoscale organizational structure of storms in subtropical South America and the U.S. are markedly similar. However, the topographical influence on the convective initiation and maintenance of the MCSs is unique to South America, where the Andes and related topography focus deep convection initiation in a narrow region. In a previous study, we examined the storm evolution by making use of the time continuity of the GOES infrared satellite data and NCEP/NCAR reanalysis. However, information about the underlying dynamics could not be determined from the data alone. Therefore, we have conducted numerical simulations with the NCAR Weather Research and Forecasting (WRF) Model to extend the analysis and provide an objective dynamical evaluation of storm initiation mechanisms, which include a capping inversion in the lee of the Andes, orographic triggering of the convection, and downstream organization into mesoscale storm systems. We simulated two representative cases with triple-nested domains. The simulated mesoscale systems closely resemble the storm structures seen by the TRMM satellite as well as the overall shape and character of the storms shown in the GOES satellite data. Results from these simulations will be presented at the conference including the role of small scale topographic features, subsidence in the lee of the Andes, and sensitivity to model microphysics.

Rasmussen, K. L.; Houze, R.; Kumar, A.

2012-12-01

280

Draconid meteor storms  

NASA Astrophysics Data System (ADS)

Outbursts and storms in the October Draconid meteor shower occur because meteoroids from the parent periodic comet, 21P/Giacobini-Zinner, are not dispersed uniformly around the stream. The comet's orbital evolution has allowed meteoroidal material to be fed into the stream for the past few centuries and to be supplied for the next thousand years or more, but this depends on the nucleus continuing to be physically active. Various shower outbursts can be linked to the comet's observed activity during the past century.

Asher, D. J.; Steel, D. I.

2012-01-01

281

LP Summer Student Program  

Cancer.gov

D  CCR Home   About CCR   CCR Intranet        Laboratory of Pathology LP Home Clinical Services Basic Sciences Training LP Staff Accessibility of Web Site LP Summer Student Program 2003/2004 Poster Day Images Past Student Images Summer Student Home About

282

Investigation of Ring Current Response to CIR-Driven Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

The physics of ring current behavior during Coronal Mass Ejection (CME)-driven storms is well understood and can be modeled with moderate accuracy. The effects of Corotating Interaction Region (CIR)-driven storms are less understood and tend to not agree with expected values. Various approaches are employed to examine the differences in ring current behavior during storms driven by these two types of events. Satellite data (Polar CAM-MICE/MICS) are analyzed to determine differences in pitch angle distributions and energy densities, in order to provide insight into how the various ring current enhancement and loss processes differ during the different types of events. A ring current model (the Comprehensive Ring Current Model) is also employed to analyze these differences by modeling ring current behavior during CME and CIR events that fit a typical solar wind profile. No differences in convection were noted in satellite data during CME and CIR-driven storms of similar strength, although oxygen was found to contribute more to the energy density during CIRs. However, model results demonstrated that there is a significant difference in ring current response during storms associated with the different drivers. It was determined that particle convection appears to be the primary ring current energization mechanism for CME-driven events, while other factors seem to influence the induced surface magnetic disturbance during CIR-driven storms; possibly boundary conditions, external currents or fluctuations caused by the associated wave-induced oscillations in the solar wind.

Cramer, William Douglas

283

Current understanding of magnetic storms: Storm-substorm relationships  

Microsoft Academic Search

This paper attempts to summarize the current understanding of the storm\\/substorm relationship by clearing up a considerable amount of controversy and by addressing the question of how solar wind energy is deposited into and is dissipated in the constituent elements that are critical to magnetospheric and ionospheric processes during magnetic storms. (1) Four mechanisms are identified and discussed as the

Y. Kamide; W. Baumjohann; I. A. Daglis; W. D. Gonzalez; M. Grande; J. A. Joselyn; R. L. McPherron; J. L. Phillips; E. G. D. Reeves; G. Rostoker; A. S. Sharma; H. J. Singer; B. T. Tsurutani; V. M. Vasyliunas

1998-01-01

284

A study of severe storm electricity via storm intercept  

NASA Technical Reports Server (NTRS)

Storm electricity data, radar data, and visual observations were used both to present a case study for a supercell thunderstorm that occurred in the Texas Panhandle on 19 June 1980 and to search for insight into how lightning to ground might be related to storm dynamics in the updraft/downdraft couplet in supercell storms. It was observed that two-thirds of the lightning ground-strike points in the developing and maturing stages of a supercell thunderstorm occurred within the region surrounding the wall cloud (a cloud feature often characteristic of a supercell updraft) and on the southern flank of the precipitation. Electrical activity in the 19 June 1980 storm was atypical in that it was a right-mover. Lightning to ground reached a peak rate of 18/min and intracloud flashes were as frequent as 176/min in the final stages of the storm's life.

Arnold, Roy T.; Horsburgh, Steven D.; Rust, W. David; Burgess, Don

1985-01-01

285

Summer Library Reading Programs  

ERIC Educational Resources Information Center

Virtually all public libraries in the United States provide some type of summer library reading program during the traditional summer vacation period. Summer library reading programs provide opportunities for students of many ages and abilities to practice their reading skills and maintain skills that are developed during the school year. Fiore…

Fiore, Carole D.

2007-01-01

286

Summer Correspondence Program.  

ERIC Educational Resources Information Center

THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: The goals of the Summer Correspondence Program have been to help students maintain their basic skills and avoid summer fall-out, as well as to promote parent involvement and positive community relations. After Proposition 13 left no funds for continuation of summer school programs, Sulphur Springs…

Sulphur Springs Union Elementary School District, Canyon Country, CA.

287

Summer Programs for Educators  

ERIC Educational Resources Information Center

There are so many great ways to extend oneself professionally--or personally--over the summer. This paper presents several opportunities for summer 2009: (1) The Teacher-to-Teacher Initiative; (2) Courage to Teach; (3) University of South Carolina's Summer Institute in Computer Science; (4) Online Program in Online Teaching; and (5) College Board…

Curriculum Review, 2009

2009-01-01

288

Slowing the Summer Slide  

ERIC Educational Resources Information Center

Research shows that summer slide--the loss of learning over the summer break--is a huge contributor to the achievement gap between low-income students and their higher-income peers. In fact, some researchers have concluded that two-thirds of the 9th-grade reading achievement gap can be explained by unequal access to summer learning opportunities…

Smith, Lorna

2012-01-01

289

Guidelines for Calibration and Application of STORM.  

National Technical Information Service (NTIS)

This report provides specific information on calibration and application of the Storage, Treatment, Overflow Runoff Model (STORM). The STORM model is intended for use in simulation of the quantity and quality of storm water runoff. In particular, the repo...

J. Abbott

1977-01-01

290

46 CFR 116.920 - Storm rails.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Storm rails. 116.920 Section 116.920 Shipping...49 PASSENGERS CONSTRUCTION AND ARRANGEMENT Rails and Guards § 116.920 Storm rails. Suitable storm rails or hand grabs must...

2013-10-01

291

Magnetic storm response of lower thermosphere density  

NASA Astrophysics Data System (ADS)

Measurements of atmospheric density near 200 km from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment are used to delineate the temporal, seasonal-latitudinal, and day/night dependences of the response to magnetic storm-related perturbations in high-latitude energetic inputs. Five periods of geomagnetic activity are analyzed and yield consistent results which can be interpreted within the framework of recent thermosphere-ionosphere simulations by Fuller-Rowell et al. [1995]: In response to a change in magnetic activity level from quiet (Kp~1-2) to active (Kp~4-7) conditions, an increase in daytime (1030 LT) density of order 50-70% occurs between 60 and 80° geographic latitude in the summer hemisphere, with about half the maximum response in the winter hemisphere. This difference is mainly due to the difference in ionization/conductivity levels (and hence joule heating rates) between the hemispheres. On the dayside, penetration of the disturbance at about the 50% intensity level is realized at the equator, whereas in the winter hemisphere equatorward penetration is much weaker. These effects are connected with the prevailing solar-driven circulation; the net summer-to-winter meridional flow facilitates equatorward advection of the disturbance bulge in the summer hemisphere but hinders advection in the winter hemisphere. In both hemispheres the daytime component of the solar-driven diurnal circulation tends to oppose equatorward penetration to the same degree. However, on the nightside (2230 LT) penetration at nearly the 100% level of both summer and winter disturbance bulges are realized to within 20° of the geographic equator. This behavior is associated with the equatorward advection in both hemispheres consistent with the nighttime component of the solar-driven circulation. Comparisons with the MSISE90 model [Hedin, 1991] show it to capture the salient features of the daytime behavior but exhibits little day/night asymmetry, in contrast to the experimental results.

Forbes, J. M.; Gonzalez, R.; Marcos, F. A.; Revelle, D.; Parish, H.

1996-02-01

292

Outreach Plans for Storm Peak Laboratory  

NASA Astrophysics Data System (ADS)

The Desert Research Institute (DRI) operates a high elevation facility, Storm Peak Laboratory (SPL), located on the west summit of Mt. Werner in the Park Range near Steamboat Springs, Colorado at an elevation 10,500 ft. SPL provides an ideal location for long-term research on the interactions of atmospheric aerosol and gas- phase chemistry with cloud and natural radiation environments. SPL includes an office-type laboratory room for computer and instrumentation setup with outside air ports and cable access to the roof deck, a full kitchen and two bunk rooms with sleeping space for nine persons. We plan to create a unique summer undergraduate education experiences for students of diversity at Storm Peak Laboratory. As stressed by the College Pathways to Science Education Standards [Siebert and McIntosh, 2001], to support changes in K-12 science education transformations must first be made at the college level, including inquiry-oriented opportunities to engage in meaningful research. These workshops will be designed to allow students to experience the excitement of science, increasing their likelihood of pursing careers within the fields of scientific education or research.

Hallar, A. G.; McCubbin, I. B.

2006-12-01

293

Hydromagnetic Theory of Geomagnetic Storms  

Microsoft Academic Search

A hydromagnetic theory is presented which explains the average characteristics of geomagnetic storms. The magnetic storm is caused by a sudden increase in the intensity of the solar wind. Stresses are then set up in the geomagnetic field by the solar plasma impinging upon the geomagnetic field and becoming trapped in it. These stresses, which are propagated to the earth

A. J. Dessler; E. N. Parker

1959-01-01

294

Evaluating and Understanding Parameterized Convective Processes and their Role in the Development of Mesoscale Precipitation Systems  

NASA Technical Reports Server (NTRS)

Research efforts during the second year have centered on improving the manner in which convective stabilization is achieved in the Penn State/NCAR mesoscale model MM5. Ways of improving this stabilization have been investigated by (1) refining the partitioning between the Kain-Fritsch convective parameterization scheme and the grid scale by introducing a form of moist convective adjustment; (2) using radar data to define locations of subgrid-scale convection during a dynamic initialization period; and (3) parameterizing deep-convective feedbacks as subgrid-scale sources and sinks of mass. These investigations were conducted by simulating a long-lived convectively-generated mesoscale vortex that occurred during 14-18 Jul. 1982 and the 10-11 Jun. 1985 squall line that occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. The long-lived vortex tracked across the central Plains states and was responsible for multiple convective outbreaks during its lifetime.

Fritsch, J. Michael; Kain, John S.

1997-01-01

295

Mars Atmospheric Chemistry in Electrified Dust Devils and Storms  

NASA Technical Reports Server (NTRS)

Laboratory studies, simulations and desert field tests all indicate that aeolian mixing dust can generate electricity via contact electrification or "triboelectricity". In convective structures like dust devils or storms, grain stratification (or charge separation) occurs giving rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies [1] indicate that this storm electric field on Mars can approach atmospheric breakdown field strength of 20 kV/m. In terrestrial dust devils, coherent dipolar electric fields exceeding 20 kV/m have been measured directly via electric field instrumentation. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via the electric field to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with ambient electric field, with substantial production of dissociative products when fields approach breakdown levels of 20-30 kV/m.

Farrell, W. M.; Delory, G. T.; Atreya, S. K.; Wong, A.-S.; Renno, N. O.; Sentmann, D. D.; Marshall, J. G.; Cummer, S. A.; Rafkin, S.; Catling, D.

2005-01-01

296

Positive Cloud-to-Ground Lightning in Mesoscale Convective Systems.  

NASA Astrophysics Data System (ADS)

We have examined the characteristics of positive cloud-to-ground lightning flashes in Mesoscale Convective Systems observed during the Oklahoma-Kansas PRE-STORM project in 1985. Lightning frequencies and patterns of ground strike locations are related to observed storm precipitation structures, with emphasis placed on relating observed lightning patterns to the stratiform precipitation regions. Positive ground flashes are categorized in relation to their position relative to storm radar echo patterns, and frequency of occurrence relative to storm lifecycles. Observations presented indicate that many of the positive flashes are likely produced by the advection of positive charge from the upper levels of the convective portions of the storm. We suggest that an additional class of positive ground flashes are associated with the generation of charge by stratiform precipitation processes, specifically related to ice-ice interactions in regions of low supercooled liquid water contents. A simple one-dimensional model is developed and used to show that stratiform microphysical processes are capable of producing charge densities of 2-4 C km3. The charge structure inferred from the model is an inverted dipole with positive charge being situated below negative charge. The model results are contrasted to charge structures inferred from observational studies, one of which suggests the presence of an inverted polarity dipole.

Rutledge, Steven A.; Lu, Chungu; Macgorman, Donald R.

1990-09-01

297

Extreme Lightning Flash Rates as an Early Indicator of Severe Storms  

NASA Technical Reports Server (NTRS)

Extreme lightning flash rates are proving to be an early indicator of intensifying storms capable of producing tornadoes, damaging winds and hail. Most of this lightning is in the cloud, where the naked eye can not see it. Recent global observations of thunderstorms from space indicate that giant electrical storms (supercells and convective complexes) with flash rates on the order of 1 flash per second are most common over the land masses of the America sub-tropics and equatorial Congo Basin. Within the United States, the average tornado warning lead time on a national basis is about 11 min. The real-time observation of extreme flash rates and the rapid increase in the in-cloud flash rate, signalling the intensification of the storm updraft, may provide as much as a 50% increase in severe storm warning lead time.

Goodman, Steven J.; Arnold, James E. (Technical Monitor)

2002-01-01

298

Evolution of remotely measured inner magnetospheric ion temperatures during a geomagnetic storm  

NASA Astrophysics Data System (ADS)

With the Medium Energy Neutral Atom (MENA) instrument aboard the IMAGE spacecraft, it is possible to remotely measure the ion temperature of the terrestrial magnetosphere during periods of strong geomagnetic activity [Scime et al., 2002]. Using a superposed-epoch analysis of multiple storm intervals and a novel image summing algorithm to account for variations in viewing geometry, we have utilized over twenty geomagnetic storms to produce average ion temperature maps as a function of storm phase. In addition, because the magnetic local time dependence of the ion temperature structure can depend upon the magnitude of the convective electric field, we sorted the storms according to the strength of the cross polar cap potential drop using data from the Defense Meteorlogical Satellites Program (DMSP) in situ measurements of ion flows.

Zaniewski, Anna; Scime, Earl; Hairston, Marc; Pollock, Craig; Thomsen, Michelle; Skoug, Ruth

2004-11-01

299

Clouds and Dust Storms  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 2 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

This image was acquired during mid-spring near the North Pole. The linear water-ice clouds are now regional in extent and often interact with neighboring cloud system, as seen in this image. The bottom of the image shows how the interaction can destroy the linear nature. While the surface is still visible through most of the clouds, there is evidence that dust is also starting to enter the atmosphere.

Image information: VIS instrument. Latitude 68.4, Longitude 180 East (180 West). 38 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2004-01-01

300

GOES sounding improvement and applications to severe storm nowcasting  

NASA Astrophysics Data System (ADS)

An improved clear-sky physical retrieval algorithm for atmospheric temperature and moisture is applied to the Geostationary Operational Environmental Satellite-12 (GOES-12) Sounder. A comparison with the microwave radiometer (MWR) measured total precipitable water (TPW) at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site from June 2003 to May 2005 shows that the TPW retrievals are improved by 0.4 mm over the legacy GOES Sounder TPW product. The Lifted Index (LI) derived product imagery (DPI) from the improved soundings better depicts the pre-convective environment surrounding a tornadic supercell at Eagle Pass, Texas on 24 April 2007. Another severe storm case from 13 April 2006 demonstrates that the improved physical algorithm successfully detects low-level moisture. Both cases show the new retrievals along with the derived products will help the forecasters with short-term severe storm nowcasting.

Li, Zhenglong; Li, Jun; Menzel, W. Paul; Schmit, Timothy J.; Nelson, James P.; Daniels, Jaime; Ackerman, Steven A.

2008-02-01

301

Winter Storm Activity  

NSDL National Science Digital Library

This project explores factors that help create severe winter weather. An interactive simulation provides hands-on experience, followed by guiding questions and resource exploration. Weather affects our everyday lives. Some days it's sunny and some days its not. The years weather is split up into seasons. 1. What are the four seasons? 2. What kind of weather do you see in the summer? 3. What kind of weather is unique to winter? 4. What ...

Haight, Jennifer

2010-02-22

302

ARkStorm: A West Coast Storm Scenario  

NASA Astrophysics Data System (ADS)

The United Stated Geological Survey (USGS) Multi-Hazards Demonstration Project (MHDP) is preparing a new emergency-preparedness scenario, called ARkStorm, to address massive U.S. West Coast storms analogous to those that devastated California in 1861-62. Storms of this magnitude are projected to become more frequent and intense as a result of climate change. The MHDP has assembled experts from the National Oceanic and Atmospheric Administration (NOAA), USGS, Scripps Institute of Oceanography, the State of California, California Geological Survey, the University of Colorado, the National Center for Atmospheric Research, and other organizations to design the large, but scientifically plausible, hypothetical scenario storm that would provide emergency responders, resource managers, and the public a realistic assessment of what is historically possible. The ARkStorm patterns the 1861 - 1862 historical events but uses modern modeling methods and data from large storms in 1969 and 1986. The ARkStorm draws heat and moisture from the tropical Pacific, forming Atmospheric Rivers (ARs) that grow in size, gain speed, and with a ferocity equal to hurricanes, slam into the U.S. West Coast for several weeks. Using sophisticated weather models and expert analysis, precipitation, snowlines, wind, and pressure data the modelers will characterize the resulting floods, landslides, and coastal erosion and inundation. These hazards will then be translated into the infrastructural, environmental, agricultural, social, and economic impacts. Consideration will be given to catastrophic disruptions to water supplies resulting from impacts on groundwater pumping, seawater intrusion, water supply degradation, and land subsidence. Possible climate-change forces that could exacerbate the problems will also be evaluated. In contrast to the recent U.S. East and Gulf Coast hurricanes, only recently have scientific and technological advances documented the ferocity and strength of possible future West Coast storms. A task of ARkStorm is to elevate the visibility of the very real threats to human life, property, and ecosystems posed by extreme storms on the U.S. West Coast. This enhanced visibility will help increase the preparedness of the emergency management community and the public to such storms. ARkStorm is scheduled to be completed by September 2010 and will be the basis of a state-wide emergency response drill, Golden Guardian, led by the California Emergency Management Agency in 2011.

Cox, D. A.; Jones, L. M.; Ralph, F. M.; Dettinger, M. D.; Porter, K.; Perry, S. C.; Barnard, P. L.; Hoover, D.; Wills, C. J.; Stock, J. D.; Croyle, W.; Ferris, J. C.; Plumlee, G. S.; Alpers, C. N.; Miller, M.; Wein, A.; Rose, A.; Done, J.; Topping, K.

2009-12-01

303

Dust storm in Chad  

NASA Technical Reports Server (NTRS)

Lake Chad (lower left) and the surrounding wetlands are under increasing pressure from desertification. The encroachment of the Sahara occurs with creeping sand dunes and major dust storms, such as the one pictured in this MODIS image from October 28, 2001. The amount of open water (lighter green patch within the darker one) has declined markedly over the last decades and the invasion of dunes is creating a rippled effect through the wetlands that is all too clear in the high-resolution images. Growing population and increasing demands on the lake give it an uncertain future. The loss of such an important natural resource will have profound effects on the people who depend on the rapidly diminishing source of fresh water. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

2002-01-01

304

Peace at Storm King  

SciTech Connect

A 20 year struggle between energy and environmental interests concerning a proposed pumped storage plant near Storm King Mountain, N.Y., has ended in a compromise that will hopefully protect the Hudson River's fish and scenic beauty. Consolidated Edison has agreed to halt construction of the pumped storage power plant and, along with other utilities operating power generating units on the Hudson River, has agreed to undertake appropriate measures to reduce destruction of fish and other aquatic life. These utilities will also set up a $12 million endowment to fund independent research on ways to lessen power plant impacts on aquatic ecosystems. In exchange for these commitments, the utilities will not be required to build cooling towers at operating power plant sites, and all lawsuits and administrative proceedings against them will be dropped.

Temple, T.

1981-02-01

305

Storm Events Database  

NSDL National Science Digital Library

From the National Climatic Data Center comes the Storms Events Database. Events are included from 1993 to the present, but as is stated on the site, the site is usually 90-120 days behind the current month. Users first choose a state and then, if necessary, a county, date, and event type. Results can be limited by tornado type, hail size, wind speed, number of injuries or deaths, and even amount of property or crop damage. The generated report lists all of the events during the time period specified and, when clicked, contain specific information about that event. Although the reports can not be downloaded, this powerful resource can be an helpful addition to a researcher's toolbox.

306

Deep convection in the Sahel : a focus on gust fronts  

NASA Astrophysics Data System (ADS)

Convection in the Sahel presents a diurnal variability that is influenced by deep convection systems like the Mesoscale Convective Systems (MCSs) and isolated storms or smaller convective systems. These smaller systems have drew less attention than the MCSs, even though they also play a role in the water cycle of this region, contribute to the monsoon dynamics, and to set the scales of the surface heterogeneities. During the African Monsoon Multidisciplinary Analysis (AMMA) intensive observation period in 2006, many of these smaller systems have been observed with the Massachusetts Institute of Technology (MIT) radar that was installed in Niamey, Niger. A systematic study of daytime convection observed during the month of July 2006 is carried out based on the MIT radar data and on the complementary observations given by the ARM mobile facility, in order to analyse the processes and mechanisms involved of deep convection initiation. The results highlight a large frequency of occurrence of the density currents, and their importance in the initiation of new convective cells. Based on this observational analysis and on results from Large Eddy Simulation (LES), density currents are specifically studied, with the aim at : (1) evaluating their frequency of occurrence, (2) assessing their ability to trigger new convective cells, (3) analysing the sensitivity of density currents velocity to land surface contrasts, (4) testing a simple model for their parametrization, (5) evaluating the ability of the LES to represent density currents.

Dione, Cheikh; Lothon, Marie; Campistron, Bernard; Sall, Saidou M.; Guichard, Françoise; Badiane, Daouda; Couvreux, Fleur

2014-05-01

307

Overview of the Deep Convective Clouds and Chemistry Experiment  

NASA Astrophysics Data System (ADS)

The Deep Convective Clouds and Chemistry (DC3) project conducted a 7-week field campaign during May and June 2012 to study thunderstorm dynamical, physical, and electrical characteristics, as well as their effects on the atmosphere's composition, especially ozone and particles in the climate-sensitive upper troposphere near the thunderstorm tops. The NSF/NCAR Gulfstream V (GV) and the NASA DC-8 aircraft flew 17 coordinated flights to sample low-level inflow and upper troposphere outflow air near thunderstorms and to sample convective outflow air as it chemically aged during the next 24 hours. The DLR Falcon aircraft observed the fresh storm outflow and also obtained measurements of aged outflow. In total, 19 cases of active thunderstorms and over 6 cases of photochemical aging were flown. The DC3 aircraft, based in Salina, Kansas, were equipped with instruments to measure a variety of gases, aerosols, and cloud particle characteristics in situ as well as the NASA DC-8 measuring the ozone and aerosol distribution by lidar. The aircraft targeted storms predicted to occur within range of coverage by ground-based radar pairs, lightning mapping arrays (LMAs), and frequent launches of balloon-borne instruments that could measure the storm's physical, kinematic, and lightning characteristics. This coverage occurred in three regions: 1) northeastern Colorado, 2) central Oklahoma to western Texas, and 3) northern Alabama. DC3 demonstrated that it is possible to sample with two aircraft the inflow and outflow of storms, which were simultaneously sampled by the ground radars, LMAs, and soundings. The DC3 data set is extensive and rich. This presentation will summarize the overall statistics of the DC3 measurements giving a general idea of storm characteristics, transport of trace gases, and photochemical aging of species. Examples will be given of specific thunderstorm cases, including a Colorado case where a biomass-burning plume was ingested by a storm, and of sampling a thunderstorm, forecasting the location of the convective outflow plume the next day, and sampling the Day 2 convective outflow. In addition, the photochemical aging of convective outflow air from a decaying Mesoscale Convective System will be highlighted.

Barth, M. C.; Brune, W. H.; Cantrell, C. A.; Rutledge, S. A.; Crawford, J. H.; Flocke, F. M.; Huntrieser, H.

2012-12-01

308

Detection of Infrasonic Energy From Tornado-Producing Storms  

NASA Astrophysics Data System (ADS)

There are numerous reports in the literature on the observation of infrasound emitted from tornadic thunderstorms. Most of these observations have been made from sensors that are several hundreds of kilometers from the location of the storm, and "ground truth" about the tornadic activity is not well established. We report here on a campaign carried out during the summer of 2011 in which 50 infrasound microphones (whose approximate frequency response is 0.01-500 Hz) developed at the University of Mississippi were deployed by members of Hyperion Technology Group and their associates as part of an ongoing multi-university program on hazard detection and alert funded by the National Oceanic and Atmospheric Administration (NOAA). In this campaign, our deployment teams were able to deploy sensors along the paths of developing tornadic storms, including sensors that were located between twin F5 tornados near Oklahoma City on May 24, 2011. For this particular deployment we had sensors located a few kilometers from the northern most F5 tornado, and a second array, composed of three linear element arrays, that was optimally northeast of the storm. (A total of 7 tornados touched down in this area during this particular severe weather outbreak.) Substantial meteorological information, including ground truth about tornados (intensity and size as a function of time), and the relative close proximity of the sensors to the storms, provides us with a level of detail not available in previous storms. We will report on our infrasound measurements and analysis (source strength, frequency content as a function of tornadic intensity) from this outbreak as well as data from two other interceptions of tornadic storms, which occurred on the dates of May 30 and June 19, 2001.

Talmadge, C. L.; Waxler, R.; Kleinert, D. E.; Carter, G. E.; Godbold, G.; Harris, D. R.; Williams, C.

2011-12-01

309

Microphysics, Meteorology, Microwave and Modeling of Mediterranean Storms: The M(sup 5) Problem  

NASA Technical Reports Server (NTRS)

Comprehensive understanding of the microphysical nature of Mediterranean storms requires a combination of in situ meteorological data analysis and radar-passive microwave data analysis, effectively integrated with numerical modeling studies at various scales, particularly from synoptic scale down to mesoscale. The microphysical properties of and their controls on severe storms are intrinsically related to meteorological processes under which storms have evolved, processes which eventually select and control the dominant microphysical properties themselves. Insofar as hazardous Mediterranean storms, highlighted by the September 25-28/1992 Genova flood event, the October 5-7/1998 Friuli flood event, and the October 13-15/2000 Piemonte flood event (all taking place in northern Italy), developing a comprehensive microphysical interpretation requires an understanding of the multiple phases of storm evolution and the heterogeneous nature of precipitation fields within the storm domains. This involves convective development, stratiform transition and decay, orographic lifting, and sloped frontal lifting proc esses. This also involves vertical motions and thermodynamical instabilities governing physical processes that determine details of the liquid/ice water contents, size distributions, and fall rates of the various modes of hydrometeors found within the storm environments. This paper presents detailed 4-dimensional analyses of the microphysical elements of the three severe Mediterranean storms identified above, investigated with the aid of SSM/I and TRMM satellite measurements (and other remote sensing measurements). The analyses are guided by nonhydrostatic mesoscale model simulations at high resolution of the intense rain producing portions of the storm environments. The results emphasize how meteorological controls taking place at the large scale, coupled with localized terrain controls, ultimately determine the most salient features of the bulk microphysical properties of the storms. These results have bearing on precipitation remote sensing from space, and the role of modeling in designing precipitation retrieval algorithms.

Smith, Eric A.; Fiorino, Steven; Mugnai, Alberto; Panegrossi, Giulia; Tripoli, Gregory; Starr, David (Technical Monitor)

2001-01-01

310

A density-temperature description of the outer electron radiation belt during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Bi-Maxwellian fits are made to energetic-electron flux measurements from seven satellites in geosynchronous orbit, yielding a number density (n) and temperature (T) description of the outer electron radiation belt. For 54.5 spacecraft years of measurements the median value of n is 3.7 × 10-4 cm-3, and the median value of T is 148 keV. General statistical properties of n, T, and the 1.1-1.5 MeV flux F are investigated, including local-time and solar-cycle dependencies. Using superposed-epoch analysis where the zero epoch is convection onset, the evolution of the outer electron radiation belt through high-speed-stream-driven storms is investigated. The number-density decay during the calm before the storm, relativistic-electron dropouts and recoveries, and the heating of the outer electron radiation belt during storms are analyzed. Using four different "triggers" (sudden storm commencement (SSC), southward interplanetary magnetic field (IMF) portions of coronal mass ejection (CME) sheaths, southward-IMF portions of magnetic clouds, and minimum Dst) a selection of CME-driven storms are analyzed with superposed-epoch techniques. For CME-driven storms, only a very modest density decay prior to storm onset is found. In addition, the compression of the outer electron radiation belt at the time of SSC is analyzed, the number-density increase and temperature decrease during storm main phase are characterized, and the increase in density and temperature during storm recovery phase is determined. During the different phases of storms, changes in the flux are sometimes in response to changes in the temperature, sometimes to changes in the number density, and sometimes to changes in both. Differences are found between the density-temperature and flux descriptions, and it is concluded that more information is available using the density-temperature description.

Denton, Michael H.; Borovsky, Joseph E.; Cayton, Thomas E.

2010-01-01

311

Polar Cap Potential Saturation and Ionospheric Convection Patterns during Superstorms  

NASA Astrophysics Data System (ADS)

Five super intense magnetic storms (with minimum Dst < -200 nT) were examined to investigate the relationship between polar cap potential (PCP) saturation and ionospheric convection patterns. A quantitative method was used to determine whether or not PCP was saturated by applying both linear and nonlinear (exponential) fits for each event. The results showed that PCP saturation occurred for two of five. The two events with saturation had distorted ionospheric convection patterns (D-CONV) with asymmetric vortices, while for the other three events without PCP saturation had well-known standard convection (S-CONV) with quasi-symmetric twin vortices. The authors conclude that sporadic midnight sector substorm electric fields may contribute to the asymmetric convection patterns and PCP saturation, in agreement with previous speculations. Further analyses are needed to confirm this hypothesis.t;

Du, A.; Sun, W.; Tsurutani, B.

2012-12-01

312

Energy analysis of convectively induced wind perturbations  

NASA Technical Reports Server (NTRS)

Budgets of divergent and rotational components of kinetic energy (KD and KR) are examined for four upper level wind speed maxima that develop during the fourth Atmospheric Variability Experiment (AVE IV) and the first AVE-Severe Environmental Storms and Mesoscale Experiment (AVE-SESAME I). A similar budget analysis is performed for a low-level jet stream during AVE-SESAME I. The energetics of the four upper level speed maxima is found to have several similarities. The dominant source of KD is cross-contour flow by the divergent wind, and KD provides a major source of KR via a conversion process. Conversion from available potential energy provides an additional source of KR in three of the cases. Horizontal maps reveal that the conversions involving KD are maximized in regions poleward of the convection. Low-level jet development during AVE-SESAME I appears to be assisted by convective activity to the west.

Fuelberg, Henry E.; Buechler, Dennis E.

1989-01-01

313

Added value of convection permitting seasonal simulations  

NASA Astrophysics Data System (ADS)

In this study the added value of a ensemble of convection permitting climate simulations (CPCSs) compared to coarser gridded simulations is investigated. The ensemble consists of three non hydrostatic regional climate models providing five simulations with ~10 and ~3 km (CPCS) horizontal grid spacing each. The simulated temperature, precipitation, relative humidity, and global radiation fields are evaluated within two seasons (JJA 2007 and DJF 2007-2008) in the eastern part of the European Alps. Spatial variability, diurnal cycles, temporal correlations, and distributions with focus on extreme events are analyzed and specific methods (FSS and SAL) are used for in-depth analysis of precipitation fields. The most important added value of CPCSs are found in the diurnal cycle improved timing of summer convective precipitation, the intensity of most extreme precipitation, and the size and shape of precipitation objects. These improvements are not caused by the higher resolved orography but by the explicit treatment of deep convection and the more realistic model dynamics. In contrary improvements in summer temperature fields can be fully attributed to the higher resolved orography. Generally, added value of CPCSs is predominantly found in summer, in complex terrain, on small spatial and temporal scales, and for high precipitation intensities.

Prein, A. F.; Gobiet, A.; Suklitsch, M.; Truhetz, H.; Awan, N. K.; Keuler, K.; Georgievski, G.

2013-11-01

314

Centralized Storm Information System (CSIS)  

NASA Technical Reports Server (NTRS)

A final progress report is presented on the Centralized Storm Information System (CSIS). The primary purpose of the CSIS is to demonstrate and evaluate real time interactive computerized data collection, interpretation and display techniques as applied to severe weather forecasting. CSIS objectives pertaining to improved severe storm forecasting and warning systems are outlined. The positive impact that CSIS has had on the National Severe Storms Forecast Center (NSSFC) is discussed. The benefits of interactive processing systems on the forecasting ability of the NSSFC are described.

Norton, C. C.

1985-01-01

315

Overstory and understory leaf area index as indicators of forest response to ice storm damage  

Microsoft Academic Search

Leaf area index (LAI) was measured with the tracing radiation and architecture of canopies (TRAC) optical instrument in three consecutive summers from 1999 to 2001 in sugar maple forests across eastern Ontario to monitor recovery from ice storm damage suffered in January 1998. The study sites were experimental blocks of the Ontario Ministry of Natural Resources (OMNR) designed for measurement

Ian Olthof; Douglas J. King; R. A. Lautenschlager

2002-01-01

316

Changes in submerged plants at the South end of Cayuga Lake following Tropical Storm Agnes  

Microsoft Academic Search

Tropical Storm Agnes produced increased suspended sediments and decreased water transparency at the southern end of Cayuga Lake for a sustained period during the early summer of 1972. The 1972 community of submerged vascular plants was severely affected. Standing crops were drastically reduced and the species composition of the plant community changed compared to 1970. In 1973, standing crop values

Ray T. Oglesby; Albert Vogel; John H. Peverly; Robert Johnson

1976-01-01

317

Severe storm cell classification using derived products optimized by genetic algorithms  

Microsoft Academic Search

Meteorological volumetric radar data is used to detect thunderstorms that are responsible for most severe summer weather. Discriminating between different storm types is a difficult problem, however. A radar data processing system conducts a volume scan by stepping a continuously rotating antenna through a series of elevation angles at regular intervals. Systems exist that allow meteorologists to focus their attention

Pak C. Li; Nicolino Pizzi; Witold Pedrycz; Dave Westmore; Rodrigo Vivancot

2000-01-01

318

A simulation of the merger of convective clouds in the torrential rainfalls associated with the Meiyu front  

NASA Astrophysics Data System (ADS)

The merger of convective clouds in severe precipitation associated with the Meiyu front occurred near Nanjing during 4-5 July 2003 is investigated using satellite observational analyses and numerical simulations with the Weather Research and Forecast version 3.2. It is found that the merger of convective clouds plays a crucial role in the excessive storm. The severe rainfall event experiences a multi-scale organized process ranging from triggered convective bulbs, growing convective cells, to the formation of the convective complex. The development of convections causes the large-scale dynamic and thermodynamic environment change, which in turn favors the organized processes of convective systems and promotes multi-scale coupling of the nonlinear interaction between convections and its large-scale environment.

Ping, Fan; Luo, Zhexian; Tang, Xiba; Hu, Liang

2014-01-01

319

Celebrate Summer with Reading  

NSDL National Science Digital Library

School is out and the summer is full of both official and unofficial holidays that prompt us to enjoy science and the profession of sharing it. As in past years, the reviewers and editors of NSTA Recommends --ready and willing to share their enthusiasm for reading with you--have been gathering suggestions for the summer. So along with your beach chairs, flags, and fireworks schedules; collect some reading material for a summer of personal enrichment.

Texley, Juliana

2007-07-01

320

Variations in Convectively Coupled Wave Activity and their Relationship with the Background Environment  

NASA Astrophysics Data System (ADS)

Different types of convectively coupled equatorial waves are isolated through space-time filtering techniques applied to the NCAR/NCEP Outgoing Long-wave Radiation (OLR) global daily dataset. For each type of wave, a wavelet analysis is applied on the filtered OLR time-series at each grid-point in the Tropics, and the wavelet power is averaged over the range of scale corresponding to the wave type. The resulting daily quantity can be used as an index of the evolution of wave activity with time. The variations of these envelopes of wave activity, and the main time-scales involved, are studied in the context of the waves’ background environment through Empirical Orthogonal Function (EOF) and lag-regression analyses. The evolution of the waves’ envelope of activity onto an index of the Madden Julian Oscillation for the winter and summer seasons suggest that part of the Kelvin wave and Equatorial Rossby (ER) wave activity signals are modulated by MJO phases. Interestingly, the first spatial EOF mode of the Kelvin wave activity envelope does not correspond directly to an MJO signal. This suggests that other modulating factors are likely to be involved. The potential influence of the background flow and of the extra-tropical transient activity in the mid-latitude storm-tracks are also explored. It is found that Pacific Kelvin wave activity is favored during periods of westerly shear with height on the equator in that basin. Strong co-dependence of Kelvin wave activity on the extratropical storm track activity is seen, suggesting that at least some periods of Kelvin activity is excited by extratropical forcing.

Leroux, S.; Kiladis, G. N.

2010-12-01

321

Mantle Convection Modeling  

NSDL National Science Digital Library

This research page provides links to two animations of modeled mantle convection, showing the progression of convection over millions of years. There are also links to other work and publications by the author.

Livnat, Yarden; Utah, University O.

322

Colorful Convection Currents  

NSDL National Science Digital Library

In this activity, students create artifical convection currents using hot and cold water, food coloring, and bottles. A materials list, instructions, and a brief explanation of the convection phenomenon are included.

323

FASEB Summer Research Conferences  

NSDL National Science Digital Library

This website provides information regarding summer research conferences hosted internationally by FASEB. The conferences spread a wide range of scientific specialties and serve academics and health professionals.

2012-07-24

324

Computer Summer Camp.  

ERIC Educational Resources Information Center

Describes the objectives, organization, and daily activities of a youth summer camp program providing general knowledge about computers, computing, social implications of computers, and opportunities for careers. (CMV)

Zabinski, Toby F.; Zabinski, Michael P.

1979-01-01

325

Convective Structure Observed from HIWRAP During MC3E  

NASA Astrophysics Data System (ADS)

The High-altitude Imaging Wind and Rain Profiler (HIWRAP) was configured to fly on the high-altitude NASA ER-2 during Mid-Latitude Continental Convective Clouds Experiment (MC3E) in support of Global Precipitation Mission (GPM) Ground Validation algorithm development. HIWRAP-ER2 is a dual-frequency (Ku, Ka-band) nadir pointing Doppler radar. While our specific objectives were to get data sets for GPM algorithm development, the HIWRAP data provided excellent vertical cross sections through a variety of convective and stratiform systems that were near or within the enhanced Southern Great Plains (SGP) network. In this presentation, we provide preliminary analyses of HIWRAP observations along with coordinated ground-based radar coverage when available. The focus will be on a.) general structural characteristics of the convection, and b.) dual frequency reflectivity and Doppler measurements and their implications on the microphysical structure of the storms. The convective structure during MC3E will be compared with tropical and subtropical convective storms previously studied with the high-altitude radar measurements.

Heymsfield, G. M.; Tian, L.; Li, L.; Mclinden, M.; Reynolds, A.; Cervantes, J.

2011-12-01

326

Magnetospheric Storms at Saturn and Earth  

NASA Astrophysics Data System (ADS)

Terrestrial magnetospheric storms are a well-known phenomenon in which plasma from the solar wind and the ionosphere is convected into the inner magnetosphere ("ring current") and energized by betatron acceleration and rapid changes in the magnetic field (substorms). Here we compare terrestrial storm characteristics with similar, newly found characteristics of Saturn's magnetosphere. We characterize Saturn's magnetospheric response to solar wind variability by using remote energetic neutral atom (ENA) measurements with simultaneous in-situ solar wind measurements when Cassini was outside the Saturnian magnetosphere. The Ion and Neutral Camera on board the Cassini spacecraft have obtained global energetic neutral atom (ENA) images of the hot plasma of Saturn's magnetosphere since July 2004. INCA obtains ENA images in the ~3-200 keV/nuc of protons and O+. The typical observations show hot plasma distributed roughly between 6 to 30 RS orbiting the planet at a period around the 10h45min rotation period depending on energy and species. However, some observations show how ENA intensity builds up on the nightside during intervals longer than the rotation period which indicates a gradual source of plasma. The intervals are often ended by a dramatic ENA intensification followed by a rotation of the newly injected plasma around the planet. We have selected a few of such intervals when Cassini was in the solar wind and could obtain solar wind parameters and simulataneous ENA image sequences. We use the Magnetic Field Experiment (MFE), the Cassini Charge Energy Mass Spectrometer (CHEMS), and the Cassini Plasma Spectrometer Subsystem (CAPS) to study the IMF, solar wind speed and density during these events and find that Saturn's magnetospheric activity most likely depends more on solar wind pressure than magnetic field orientation.

Brandt, P.; Mitchell, D.; Rymer, A.; Hill, M.

2007-08-01

327

Magnetospheric Storms at Saturn and Earth  

NASA Astrophysics Data System (ADS)

The terrestrial magnetospheric storms are a well-known phenomenon in which plasma from the solar wind and the ionosphere is convected into the inner magnetosphere ("ring current") and energized by betatron acceleration and rapid changes in the magnetic field (substorms). Here we compare terrestrial storm characteristics with similar, newly found characteristics of Saturn's magnetosphere. We characterize Saturn's magnetospheric response to solar wind variability by using remote energetic neutral atom (ENA) measurements with simultaneous in-situ solar wind measurements when Cassini was outside the Saturnian magnetosphere. The Ion and Neutral Camera on board the Cassini spacecraft have obtained global energetic neutral atom (ENA) images of the hot plasma of Saturn's magnetosphere since February 2004. INCA obtains ENA images in the ~3-200 keV/nuc of protons and O+. The typical observations show hot plasma distributed roughly between 6 to 30 RS orbiting the planet with a period around the 10h45min rotation period depending on energy and species. However, some observations show how ENA intensity builds up on the nightside during intervals longer than the rotation period which indicates a gradual source of plasma. The intervals are often ended by a dramatic ENA intensification followed by a rotation of the newly injected plasma around the planet. We have selected a few of such intervals when Cassini was in the solar wind and could obtain solar wind parameters and simulataneous ENA image sequences. We use the Magnetic Field Experiment (MAG), the Cassini Charge Energy Mass Spectrometer (CHEMS), and the Cassini Plasma Spectrometer Subsystem (CAPS) to study the IMF, solar wind speed and density during these events and find that Saturn's magnetospheric activity most likely depends more on solar wind pressure than magnetic field orientation.

Brandt, P. C.; Mitchell, D. G.; Carbary, J.; Rymer, A.; Hill, M. E.; Paranicas, C.; Dougherty, M. K.; Young, D. T.

2007-12-01

328

The Radiation Belt Storm Probes  

NASA Video Gallery

The Radiation Belt Storm Probe mission (RBSP) will explore the Van Allen Radiation Belts in the Earth's magnetosphere. The charge particles in these regions can be hazardous to both spacecraft and ...

329

Cloudsat Dissects Tropical Storm Ileana  

NASA Video Gallery

NASA's CloudSat satellite's Cloud Profiling Radar captured a sideways look across Tropical Storm Ileana on Aug. 27 at 20:40 UTC. The colors indicate intensity of reflected radar energy. The blue ar...

330

Variability of total electron content near the crest of the equatorial anomaly during moderate geomagnetic storms  

NASA Astrophysics Data System (ADS)

The ionospheric responses to a large number (116) of moderate (-50?Dst>-100 nT) geomagnetic storms distributed over the period (1980-1990) are investigated using total electron content (TEC) data recorded at Calcutta (88.38°E, 22.58°N geographic, dip: 32°N). TEC perturbations exhibit a prominent dependence on the local times of main phase occurrence (MPO). The storms with MPO during daytime hours are more effective in producing larger deviations and smaller time delays for maximum positive deviations compared to those with nighttime MPO. Though the perturbations in the equinoctial and winter solstitial months more or less follow the reported climatology, remarkable deviations are detected for the summer solstitial storms. Depending on the local times of MPO, the sunrise enhancement in TEC is greatly perturbed. The TEC variability patterns are interpreted in terms of the storm time modifications of equatorial electric field, wind system and neutral composition.

Chakraborty, S. K.; Hajra, R.

2010-07-01

331

Hurricane Katrina Storm Surge Reconnaissance  

Microsoft Academic Search

Hurricane Katrina August 23-30, 2005 was one of the costliest and deadliest hurricanes to ever strike the United States, impacting low-lying coastal plains particularly vulnerable to storm surge flooding. Maximum storm surges, overland flow depths, and inundation distances were measured along the Gulf Coast of Florida, Alabama, Mississippi, and Louisiana. The vehicle-based survey was complemented by inspections with the reconnaissance

Hermann M. Fritz; Chris Blount; Robert Sokoloski; Justin Singleton; Andrew Fuggle; Brian G. McAdoo; Andrew Moore; Chad Grass; Banks Tate

2008-01-01

332

Magnetic Storms and Solar Activity  

NSDL National Science Digital Library

This is a lesson about the Kp index, a common numerical indicator of magnetic storminess. Learners will access and analyze Kp index plots of magnetic storm strength and determine the relative frequency of stronger versus weaker magnetic storms during periods of higher and lower solar activity. This is the fifteenth activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

333

Hurricane and Severe Storm Lenticular  

NSDL National Science Digital Library

This resource is a 4 x 6" lenticular card on NASA's HS3 (Hurricane and Severe Storm Sentinel) aircraft mission, which will overfly tropical storms and hurricanes using NASA's Global Hawk Unmanned Aircraft Systems (UAS) in the Northern Atlantic, Caribbean, and Gulf of Mexico. These flights will improve our understanding of the processes that lead to the development of intense hurricanes. The mission will take place for one-month periods during the 2012, 2013, and 2014 Atlantic Basin hurricane seasons.

334

Climatic regimes of tropical convection and rainfall  

SciTech Connect

Annual distribution and phase propagation of tropical convection are delineated using harmonic and amplitude-phase characteristics analysis of climatological pentad mean outgoing longwave radiation and monthly frequencies of highly reflective cloud. An annual eastward propagation of peak rainy season along the equator from the central Indian Ocean (60[degrees]E) to Arafura Sea (130[degrees]E) is revealed. This indicates a transition from the withdrawal of the Indian summer monsoon to the onset of the Australian summer monsoon. Significant bimodal variations are found around major summer monsoon regions. These variations originate from the interference of two adjacent regimes. The convergence zones over the eastern North Pacific, the South Pacific, and the southwest Indian Ocean are identified as a marine monsoon regime that is characterized by a unimodal variation with a concentrated summer rainfall associated with the development of surface westerlies equatorward of a monsoon trough. Conversely, the central North Pacific and North Atlantic convergence zones between persistent northeast and southeast trades are classified as trade-wind convergence zones; which differ from the marine monsoon regime by their persistent rainy season and characteristic bimodal variation with peak rainy seasons occurring in late spring and fall. The roles of the annual march of sea surface temperature in the phase propagation and formation of various climatic regimes of tropical convection are also discussed. 34 refs., 8 figs., 1 tab.

Wang, Bin (Univ. of Hawaii, Honolulu, HI (United States))

1994-07-01

335

Storm Precipitation in the United States. Part II: Soil Erosion Characteristics.  

NASA Astrophysics Data System (ADS)

Soil erosion is a major global challenge. An increased understanding of the mechanisms driving soil erosion, especially the storms that produce it, is vital to reducing the impact on agriculture and the environment. The objective of this work was to study the spatial distribution and time trends of the soil erosion characteristics of storms, including the maximum 30-min precipitation intensity (I30), storm kinetic energy of the falling precipitation (KE), and the storm erosivity index (EI) using a long-term 15-min precipitation database. This is the first time that such an extensive climatology of soil erosion characteristics of storms has been produced. The highest mean I30, KE, and EI values occurred in all seasons in the southeastern United States, while the lowest occurred predominantly in the interior west. The lowest mean I30, KE, and EI values typically occurred in winter, and the highest occurred in summer. The exception to this was along the West Coast where winter storms exhibited the largest mean KE and EI values. Linear regression was used to identify trends in mean storm erosion characteristics for nine U.S. zones over the 31-yr study period. The south-central United States showed increases for all three storm characteristics for all four seasons. On the other hand, higher elevations along the West Coast showed strong decreases in all three storm characteristics across all seasons. The primary agricultural region in the central United States showed significant increases in fall and winter mean EI when there is less vegetative cover. These results underscore the need to update the storm climatology that is related to soil erosion on a regular basis to reflect changes over time.

Angel, James R.; Palecki, Michael A.; Hollinger, Steven E.

2005-06-01

336

Oval Storms Merging on Jupiter  

NASA Technical Reports Server (NTRS)

These four images of clouds in a portion of Jupiter's southern hemisphere show steps in the consolidation of three 'white oval' storms into one over a three-year span of time. They were obtained on four dates, from Sept. 18, 1997, to Sept. 2, 2000, by NASA's Hubble Space Telescope. The widths of the white ovals range from about 8,000 kilometers to 12,000 kilometers (about 5,000 miles to 7,500 miles). North is up and east is to the right.

The top image shows three white oval storms, which had coexisted for about 60 years. They were nicknamed FA, DE and BC, in order from west to east. By mid-1998, as shown in the second image, the two easternmost storms had merged into one, called BE. By October 1999, as shown in the third image, the merged oval and the last of the original three were approaching each other, but they were separated by a dark storm, called o 1, between them. The two white oval storms later merged into a single storm, as shown in the final image from September 2000.

The Hubble Space Telescope is a facility of NASA and the European Space Agency. It is operated by the Space Telescope Science Institute, Baltimore, Md., which is managed for NASA by the Association of Universities for Research in Astronomy in Honolulu.

2000-01-01

337

Comparison of Rainfall Characteristics and Convective Properties of Monsoon Precipitation Systems over South China and Yangtze-and-Huai River Basin  

NASA Astrophysics Data System (ADS)

Rainfall characteristics and convective properties of monsoon precipitation systems over the South China (SC) and the Yangtze-and-Huai River Basin (YHRB) are investigated by combining a gridded daily precipitation data product based on surface station observations, a Tropical Rainfall Measuring Mission dataset, the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations data products. Atmospheric aerosol amounts are inferred using a Moderate Resolution Imaging Spectroradiometer aerosol product. Comparison between the two regions is made for their monsoon active periods to reveal variations of the monsoon precipitation systems along with the northward march of the East Asian summer monsoon rainbelt from the SC to the YHRB. Relative to the YHRB, precipitation systems over the SC occur more frequently, resulting in larger maxima of the monsoon rainfall accumulation, but the SC systems are convectively less intense which is linked to the contrasts in strength of low-level vortices and surface fronts between the two regions. Contrasting among the pre-monsoon, monsoon active and break, and post-monsoon periods is also conducted for each region to unveil intraseasonal transitions of the precipitation systems, atmospheric conditions, and weather systems. Convective activities of the precipitation systems enhance progressively from the pre-monsoon to the monsoon and further to the post-monsoon period at both regions with more significant convection intensification from the pre-monsoon to the monsoon period at the YHRB, being largely in agreement with the intraseasonal variations of atmospheric thermodynamic conditions (convective available potential energy). From the pre-monsoon to the monsoon periods, the lightning flash rates decrease substantially at the SC, in contrast to the YHRB where the rates increase slightly. While aerosol loading is in favor of electrification during the pre-monsoon periods at both regions, the convective strength of the YHRB pre-monsoon is too weak to boost up lightning activity. The SC region, on the other hand, has more similar convective intensity from the pre-monsoon to the active monsoon, so aerosol effect stands out. Moreover, horizontal extents of precipitation systems are larger (smaller) on average during the monsoon active and pre-monsoon (post-monsoon and break) periods, which can be largely explained by the scale difference of the driving mechanisms: the precipitation storms are less controlled by large-scale weather systems (dynamically driven) but more by local instability due to solar heating (thermodynamically driven) during the post-monsoon and break periods.

Luo, Y.; Wang, H.; Zhang, R.; Qian, W.; Luo, Z.

2012-04-01

338

The Summer Stars Program.  

ERIC Educational Resources Information Center

Designing projects around Gardner's multiple intelligences, a Connecticut school created a one-week summer camp where children can tap into their unique strengths. The Summer Stars program allows children ages 7-12 to choose materials and activities from many topics and to participate in one of three internships involving a discovery museum, a…

Cantrell, Mary Lou; Ebdon, Susan Austin; Firlik, Russell; Johnson, Diane; Rearick, Dianne

1997-01-01

339

Summer Youth Employment Guide.  

ERIC Educational Resources Information Center

This 2-part experimental and demonstration project report is based on research and analysis conducted by the Center for Urban Programs at St. Louis University. Part I, which is derived from observations of summer youth employment programs in several cities, describes a general program guide for operating future summer youth employment programs.…

Manpower Administration (DOL), Washington, DC.

340

Under Summer Skies  

ERIC Educational Resources Information Center

There's no better way to celebrate 2009, the International Year of Astronomy, than by curling up with a good book under summer skies. To every civilization, in every age, the skies inspired imagination and scientific inquiry. There's no better place to start your summer reading than under their influence. Here are a few selections identified by…

Texley, Juliana

2009-01-01

341

Book Your Summer Vacation  

ERIC Educational Resources Information Center

Summer's the time for teachers to travel, not only physically from the confines of the classroom to exotic places, but vicariously, through the magic of books. Summer adventures help teachers expand their experience and enrich their store of context so that they can offer their students more when school resumes in the fall. That's why each year…

Texley, Juliana

2012-01-01

342

Summer by the Book  

NSDL National Science Digital Library

Are you looking for ways to log professional development hours without traveling too far away from home this summer? Through reading, a teacher can spend valuable hours updating content background and methods, or simply refreshing the spirit --at your leisure! This article offers suggestions for summer reading that are sure to catch the interest of any middle school science teacher.

Texley, Juliana

2005-07-01

343

Celebrate Summer with Reading  

ERIC Educational Resources Information Center

School is out and the summer is full of both official and unofficial holidays that prompt us to enjoy science and the profession of sharing it. As in past years, the reviewers and editors of "NSTA Recommends"--ready and willing to share their enthusiasm for reading with you--have been gathering suggestions for the summer. So along with your beach…

Texley, Juliana

2007-01-01

344

Your Best Summer Ever  

ERIC Educational Resources Information Center

"It must be nice to have summers off." Only other teachers know just how short summer is, with much of August devoted to planning for the new school year. This article offers 17 fresh ideas for exploring, making money, and preparing for next year. Plus, a reading list that hits all the marks!

Cleaver, Samantha

2012-01-01

345

ABC SUMMER PROGRAM, 1967.  

ERIC Educational Resources Information Center

THE THIRD SUMMER (1967) OF THE MT. HOLYOKE COLLEGE RESIDENTIAL SUMMER PROGRAM FOR ABLE, DISADVANTAGED HIGH SCHOOL GIRLS IS DESCRIBED. BECAUSE OF A DRASTIC CUT IN SCHOLARSHIP FUNDS, THE PROGRAM WAS FORCED TO CHANGE FROM ITS ORIGINAL PLAN TO PREPARE THESE GIRLS FOR ADMISSION TO PRIVATE SCHOOLS. INSTEAD, THE PROGRAM OFFERED COLLEGE PREPARATION AND…

KERR, FRANCES M.; RUSSELL, VALERIE E.

346

An Evaluation of Lightning Flash Rate Parameterizations Based on Observations of Colorado Storms during DC3  

NASA Astrophysics Data System (ADS)

Predicting lightning activity in thunderstorms is important in order to accurately quantify the production of nitrogen oxides (NOx = NO + NO2) by lightning (LNOx). Lightning is an important global source of NOx, and since NOx is a chemical precursor to ozone, the climatological impacts of LNOx could be significant. Many cloud-resolving models rely on parameterizations to predict lightning and LNOx since the processes leading to charge separation and lightning discharge are not yet fully understood. This study evaluates predicted flash rates based on existing lightning parameterizations against flash rates observed for Colorado storms during the Deep Convective Clouds and Chemistry Experiment (DC3). Evaluating lightning parameterizations against storm observations is a useful way to possibly improve the prediction of flash rates and LNOx in models. Additionally, since convective storms that form in the eastern plains of Colorado can be different thermodynamically and electrically from storms in other regions, it is useful to test existing parameterizations against observations from these storms. We present an analysis of the dynamics, microphysics, and lightning characteristics of two case studies, severe storms that developed on 6 and 7 June 2012. This analysis includes dual-Doppler derived horizontal and vertical velocities, a hydrometeor identification based on polarimetric radar variables using the CSU-CHILL radar, and insight into the charge structure using observations from the northern Colorado Lightning Mapping Array (LMA). Flash rates were inferred from the LMA data using a flash counting algorithm. We have calculated various microphysical and dynamical parameters for these storms that have been used in empirical flash rate parameterizations. In particular, maximum vertical velocity has been used to predict flash rates in some cloud-resolving chemistry simulations. We diagnose flash rates for the 6 and 7 June storms using this parameterization and compare to observed flash rates. For the 6 June storm, a preliminary analysis of aircraft observations of storm inflow and outflow is presented in order to place flash rates (and other lightning statistics) in the context of storm chemistry. An approach to a possibly improved LNOx parameterization scheme using different lightning metrics such as flash area will be discussed.

Basarab, B.; Fuchs, B.; Rutledge, S. A.

2013-12-01

347

Characterization of Convective Systems in Africa in Terms of their Vertical Structure, Electrification and Dynamics  

NASA Astrophysics Data System (ADS)

Mesoscale Convective Systems (MCS) are cloud systems that occur from an ensemble of thunder storms and result in a precipitation that covers a huge contiguous area. They are long-lived storm system having dimensions much larger than an individual storm. Storm systems associated with MCSs over the Africa are tracked for the period July to December 2004 and their properties at different stages of their life are investigated in terms of the vertical reflectivity profile, electrification and dynamics of clouds. The research is facilitated by remote sensing data, which include instantaneous vertical reflectivity fields derived from the TRMM precipitation radar (PR), coincident 1/2-hourly observations of long-range lightning accumulation and Global IR fields. Results show a strong indication of the magnitude and intensity of electrification of a thunderstorm with the stage of its life. More vigorous dynamic conditions with intense electrification are observed during the growing stage of the storm and more or less stable situation uniform distribution of electrification has been distributed to most of the pixels in the storm during its maturity stage and less rainfall and electrification during its decaying stage was a general observation during the period. The vertical reflectivity has been found to be strongly related to the electrification and the stage of the convective life cycle in such away that the reflectivity decrease as the storm matures and decays. A good correlation is observed between the strength of vertical profile of reflectivity, which is a proxy for the ice concentration, and lightning activity.

Tadesse, A.; Anagnostou, E. N.

2007-05-01

348

Characterization of Storms in the Tropical Andes of Central Peru Using the Trmm Precipitation Radar  

NASA Astrophysics Data System (ADS)

In the Peruvian Andes, the great geographical heterogeneity and the sparsity of raingauge networks precludes an adequate characterization of the precipitation distribution and estimation techniques based in remote sensing satellite cloud observations have not been successful in this region. However, the available data indicates very strong year-long rainfall in the eastern slopes of the Andes that is probably a substantial contribution to the Amazon discharge, whereas rainfall in the internal Andean valleys is substantially weaker but has great importance for the local population, In this study we characterize storms in both regions using data from the precipitation radar (PR) onboard TRMM, particularly the products 2A25 and 2A23, which allows us to obtain the three-dimensional spatial distribution of rainfall, an estimated surface rainfall, as well as other properties such as rain type (i.e. convective vs stratiform) and storm depth. Images from the GOES geostationary satellite also provide information of clouds and their brightness temperature. Field measurements of the Drop Size Distribution (DSD) using the filter paper technique in the Mantaro Valley in the central Andes of Peru, are used to validate the PR 2A25 algorithm for this the region, particularly the a and b parameters in the relation between rain rate (R) and reflectivity (Z), i.e. R=aZb, finding an excelent agreement for b, but a n overestimation of a in the 2A25 algorithm. We found than in the TRMM PR data for the central Andes, the overall majority of the raining pixels are stratiform and only a few pixels are convective, yet the total rain associated to the convective pixels equals to the stratiform ones. On the other hand, for a orographically-forced rainfall core in the eastern slope of the Andes, we found that although there is a larger fraction of convective pixels than in the highlands, the total stratiform and convective rainfall are similar, highlighting the importance of stratiform precipitation in this heavily raining region. Thus, rainfall estimation techniques that assume a relationship between storm height and rainfall rates do not work. It was further verified that even for convective events, GOES IR4 brightness temperature, which provides a measure of cloud top height, does not present a significant relationship with rainfall rates. However, it was found that the maximum rainfall in any storm size is correlated with the percentage of convective pixels of which the storm is made. These results yield some light on the reported underestimation of rain by some satellites-based rainfall products in the upper Amazon Basin.

Chavez, S. P.; Takahashi, K.

2013-05-01

349

An Improved Scheme for Convective/Stratiform Echo Classification Using Radar Reflectivity.  

NASA Astrophysics Data System (ADS)

An improved algorithm for the partitioning of radar reflectivity into convective and stratiform rain classifications has been developed and tested using data from the Houston, Texas, Weather Surveillance Radar-1988 Doppler. The algorithm starts with output from the current operational version of the Tropical Rainfall Measuring Mission (TRMM) convective/stratiform classification scheme for the ground-based validation sites and corrects the output based on physical characteristics of convective and stratiform rain diagnosed from the three-dimensional structure of the radar reflectivity field. The modified algorithm improved the performance of echo classification by correcting two main sources of error. Heavy stratiform rain, originally classified as convective, and the periphery of convective cores, originally classified as stratiform, were both reclassified by the modified algorithm. When applied to a large dataset of convective storms comprising squall lines, unorganized convection, and embedded convection, it was found that roughly 25% of the total echo area and 14% of the total rain volume were reclassified. The magnitudes of the differences between the original and modified algorithms varied with the morphology of the storm system, suggesting that the quality of current echo classification information supplied by the TRMM program could vary by location depending on the structure of the dominant precipitation systems within a given region. The analysis presented here helps to establish the level of uncertainty in the existing echo classification products available from TRMM.

Biggerstaff, Michael I.; Listemaa, Steven A.

2000-12-01

350

Winter storms in the central Himalayas  

NASA Astrophysics Data System (ADS)

Based on observations from a hydrometeorological network in the Marsyandi river basin, on the eastern slopes of the Annapurna Range, the summer monsoon (June-September) is responsible for 80-90% of annual precipitation at low elevations (< 2000 m MSL) in central Nepal, with nearly all of it in liquid form even during the winter. However, high elevations (> 3000 m MSL) can receive up to 25-35% of their annual precipitation as snowfall during the winter, with the percentage of the annual total an increasing function of elevation. Major snowstorms are associated with terrain-locked low-pressure systems that form when upper-level disturbances (the so-called Western Disturbances) pass over the notch formed by the Himalayas and Hindu Kush mountains, causing upper-level SW flow over central Nepal and orographically forced precipitation. Notable case studies for three winters (January-March 2000-2002) are reviewed using local precipitation (snow and rain) and other meteorological data, as well as satellite (Meteosat-5 and TRMM) and NCEP/NCAR Reanalysis data. A 30-year (1973-2002) climatology of “notch” depressions reveals that winter storms in the central Himalayas are characterized by strong inter-annual variability, which cannot be explained based on known modes of climate variability (e.g., ENSO, NAO, etc). Finally, a cloud-resolving model with realistic topography is used to investigate mechanisms for controlling the spatial and temporal variability of precipitation during typical winter storms. The results indicate that precipitation occurs in the central Himalayas only when the large-scale circulation evolves to a spatial configuration that favors orographic precipitation processes. In addition, westerly-propagating along-barrier precipitation features fed by an easterly barrier jet apparently play an important role in bringing precipitation to lower elevations.

Barros, A.; Lang, T.

2003-04-01

351

Large magnetic storm-induced nighttime ionospheric flows at midlatitudes and their impacts on GPS-based navigation systems  

Microsoft Academic Search

Analysis of GPS phase fluctuations in conjunction with regional total electron content (TEC) maps, in situ measurements of subauroral polarization streams (SAPS) and auroral convection from several Defense Meteorological Satellite Program spacecraft, and dynasonde measurements at the Bear Lake Observatory obtained during the intense magnetic storm of 7–8 November 2004 have indicated the serious impact of large ionospheric velocities on

Su. Basu; S. Basu; E. MacKenzie; P. Doherty; J. W. Wright; F. Rich; M. J. Keskinen; R. E. Sheehan

2008-01-01

352

IISME Summer Fellowship Program  

NASA Technical Reports Server (NTRS)

During the summer of 1997, NASA-Ames scientists served as mentors to six teachers who worked as IISME (Industry Initiatives for Science and Math Education) Teacher Fellows over the summer. These six teachers were among 91 IISME Teacher Fellows working at various corporate, government agency, and university sites throughout the San Francisco Bay Area. These NASA-Ames fellowship positions are described in brief. One requirement of the IISME Summer Fellowship program is that teachers develop a personal Action Plan for classroom transfer. These Action Plans are published in abstract form in an annual catalog. I have also attached the abstracts of NASA-Ames teachers.

1998-01-01

353

Radial transport of storm time ring current ions  

NASA Technical Reports Server (NTRS)

Radial transport of energetic ions for the development of the main phase of geomagnetic storms is investigated with data from the medium energy particle analyzer (MEPA) on the Charge Composition Explorer spacecraft, which monitored protons, helium ions, and the carbon-nitrogen-oxygen group, which is mostly dominated by oxygen ions. From a study of four geomagnetic storms, we show that the flux increase of these ions in the inner ring current region can be accounted for by an inward displacement of the ring current population by 0.5 to 3.5 R(E). There is a general trend that a larger inward displacement occurs at higher L shells than at lower ones. These results are in agreement with previous findings. The radially injected population consists of the prestorm population modified by substorm injections which occur on a much shorter time scale than that for a storm main phase. It is also found that the inward displacement is relatively independent of ion mass and energy, suggesting that the radial transport of these energetic ions is effected primarily by convective motion from a large electric field or by diffusion resulting from magnetic field fluctuations.

Lui, A. T. Y.

1993-01-01

354

Ring Current Development and Decay During A Geomagnetic Storm  

NASA Astrophysics Data System (ADS)

The time evolution of H+ flux equatorial 90 deg pitch angle distributions, as observed during a geomagnetic storm occurred on June 4 - 7 1991, is discussed. Proton spectra from CRRES MICS experiment, collected once a minute along the spacecraft orbit in the midnight-dusk quadrant between L = 4 and = 7, are analyzed. The trend of the ion distributions and the storm major effects on a global scale during the whole storm development are reconstructed. This is obtained by modifying some of the parame- ters of the ring current empirical model by Milillo et al. [2001] in order to best fit the experimental data. The convection electric field, monitored by one of the model parameters, increases during the main and early recovery phases. The magnetic field stretch and depolarization are acknowledged by the L-shell shorten and lengthen. The global current density development is reconstructed; a partial ring current is clearly recognizable. The effect of such current on the local magnetic field is calculated. A diffused population rises during the late recovery phase. Losses across the dayside magnetopause and due to the charge exchange processes are analyzed.

Mura, A.; Orsini, S.; Milillo, A.; Korth, Axel; Mouikis, C.; Massetti, S.; de Angelis, E.

355

Estimation of convective mass transfer in solar distillation systems  

Microsoft Academic Search

In this article a thermal model has been developed to determine the convective mass transfer for different Grashof Number range in solar distillatiOn process. The model is based on simple regression analysis. Based on the experimental data obtained from the rigorous outdoor experimentation on passive and active distillation systems for summer climatic conditions, the values of C and n have

Sanjay Kumar; G. N. Tiwari

1996-01-01

356

Ion precipitation in the dawn sector during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Three southward turnings of the IMF during the magnetic storm of 29-31 October 2003 led to ring current intensifications characterized by Dst minima. Defense Meteorological Satellite Program (DMSP) satellites detected low-energy ions precipitating equatorward of auroral electrons in the dawn/morning local time sector. These ion fluxes weakened and/or vanished subsequent to Dst recoveries. A survey of the DMSP database reveals that near-dawn ion precipitation is a main-phase characteristic of all large magnetic storms. DMSP and Combined Release and Radiation Effects Satellite (CRRES) satellites also detected similar ion precipitation during the main phase of the March 1991 magnetic storm. To reconcile these observations with elementary concepts of ion drifts, the data suggest two source populations. The lowest-energy ions were initially energized earthward of the plasma sheet electron boundary in the evening sector then corotated eastward. Higher-energy ions originated in the plasma sheet and drifted close to the Earth under the combined influences of time-varying convective electric fields and azimuthal gradients in the Earth's magnetic field. We developed a modified Volland Stern model to study test-particle trajectories in asymmetric magnetic fields and variable electric fields compatible with CRRES measurements. Ions with magnetic moments ? ? ?c ? 14 eV/nT drift duskward. Ions with ? < ?c are injected to low L shells during a spike in the convective electric field. As the electric field diminishes and shielding increases, these ions drift toward dawn much closer to Earth than any test electron trajectories. Precipitation in the dawn sector results from a combination of pitch-angle scattering by intense ambient waves and the dictates of ion drift paths.

Huang, C. Y.; Burke, W. J.; Lin, C. S.

2005-11-01

357

Keep Kids Safe This Summer  

MedlinePLUS

... Añadir en... Favorites Delicious Digg Google Bookmarks Keep Kids Safe This Summer Help your kids stay safe and healthy while they enjoy summer ... simple health tips at home and at play. Kids like to dive into summer to relax, unwind, ...

358

A kinetic energy study of the meso beta-scale storm environment during AVE-SESAME 5 (20-21 May 1979)  

NASA Technical Reports Server (NTRS)

Kinetic energy of the near storm environment was analyzed by meso beta scale data. It was found that horizontal winds in the 400 to 150 mb layer strengthen rapidly north of the developing convection. Peak values then decrease such that the maximum disappears 6 h later. Southeast of the storms, wind speeds above 300 mb decrease nearly 50% during the 3 h period of most intense thunderstorm activity. When the convection dissipates, wind patterns return to prestorm conditions. The mesoscale storm environment of AVE-SESAME 5 is characterized by large values of cross contour generation of kinetic energy, transfers of energy to nonresolvable scales of motion, and horizontal flux divergence. These processes are maximized within the upper troposphere and are greatest during times of strongest convection. It is shown that patterns agree with observed weather features. The southeast area of the network is examined to determine causes for vertical wind variations.

Printy, M. F.; Fuelberg, H. E.

1984-01-01

359

Summer Success Story.  

ERIC Educational Resources Information Center

Pennsylvania's Beaver Valley Intermediate Unit built a collaborative 2-week summer academy, opening it to students in the other 14 school districts in the county. Cooperation among all the districts provided students opportunities for expanded learning experiences. (MLF)

Matika, Francis W.

1994-01-01

360

Cashing In on Summer.  

ERIC Educational Resources Information Center

Suggests ways teachers can use their talents and expertise to create jobs for themselves that supply extra income during the summer. These "moonlighting" ideas include tutoring, giving guided tours, planning weddings, and starting exercise classes. (SJL)

Instructor, 1980

1980-01-01

361

NCI Summer Curriculum in  

Cancer.gov

This 4-week summer course provides specialized instruction in the principles and practice of cancer prevention and control. It focuses on concepts, methods, issues, and applications related to this field.

362

A kinetic energy analysis of the meso beta-scale severe storm environment  

NASA Technical Reports Server (NTRS)

Analyses are performed of the meso beta-scale (20-200 km wavelengths and several hours to one-day periods) severe storm kinetic energy balance on the fifth day of the AVE SESAME campaign of May 1979. A 24-hr interval covering the antecedent, active and post-convective outbreak activity over Oklahoma are considered. Use is made of the kinetic energy budget equation (KEBE) for a finite volume in an isobaric coordinate system. Rawindsonde data with 75 km resolution were treated. The KEBE model covered changes in kinetic energy due to the cross contour flows, horizontal and vertical components of flux divergence, and volumic mass changes on synoptic and subsynoptic scales. The greatest variability was concentrated above 400 mb height and over the most intense storm activity. Energy was generated at the highest rates in divergence and decreased the most in convection. The meso beta-scale lacked sufficient resolution for analyzing mesoscale activity.

Fuelberg, H. E.; Printy, M. F.

1984-01-01

363

Under Summer Skies  

NSDL National Science Digital Library

Thereâs no better way to celebrate 2009, the International Year of Astronomy, than by curling up with a good book under summer skies. To every civilization, in every age, the skies inspired imagination and scientific inquiry. Thereâs no better place to start your summer reading than under their influence. Here are a few selections identified by NSTA Recommendsâ network of reviewers to help get you started.

Texley, Juliana

2009-07-01

364

National Severe Storms Forecast Center  

NASA Technical Reports Server (NTRS)

The principal mission of the National Severe Storms Forecast Center (NSSFC) is to maintain a continuous watch of weather developments that are capable of producing severe local storms, including tornadoes, and to prepare and issue messages designated as either Weather Outlooks or Tornado or Severe Thunderstorm Watches for dissemination to the public and aviation services. In addition to its assigned responsibility at the national level, the NSSFC is involved in a number of programs at the regional and local levels. Subsequent subsections and paragraphs describe the NSSFC, its users, inputs, outputs, interfaces, capabilities, workload, problem areas, and future plans in more detail.

1977-01-01

365

Space storms as natural hazards  

NASA Astrophysics Data System (ADS)

Eruptive activity of the Sun produces a chain of extreme geophysical events: high-speed solar wind, magnetic field disturbances in the interplanetary space and in the geomagnetic field and also intense fluxes of energetic particles. Space storms can potentially destroy spacecrafts, adversely affect astronauts and airline crew and human health on the Earth, lead to pipeline breaking, melt electricity transformers, and discontinue transmission. In this paper we deal with two consequences of space storms: (i) rise in failures in the operation of railway devices and (ii) rise in myocardial infarction and stroke incidences.

Dorman, L. I.; Ptitsyna, N. G.; Villoresi, G.; Kasinsky, V. V.; Lyakhov, N. N.; Tyasto, M. I.

2008-04-01

366

Mechanisms initiating deep convection over complex terrain during COPS.  

SciTech Connect

Precipitating convection in a mountain region of moderate topography is investigated, with particular emphasis on its initiation in response to boundary-layer and mid- and upper-tropospheric forcing mechanisms. The data used in the study are from COPS (Convective and Orographically-induced Precipitation Study) that took place in southwestern Germany and eastern France in the summer of 2007. It is found that the initiation of precipitating convection can be roughly classified as being due to either: (i) surface heating and low-level flow convergence; (ii) surface heating and moisture supply overcoming convective inhibition during latent and/or potential instability; or (iii) mid-tropospheric dynamical processes due to mesoscale convergence lines and forced mean vertical motion. These phenomena have to be adequately represented in models in order to improve quantitative precipitation forecast. Selected COPS cases are analyzed and classified into these initiation categories. Although only a subset of COPS data (mainly radiosondes, surface weather stations, radar and satellite data) are used here, it is shown that convective systems are captured in considerable detail by sensor synergy. Convergence lines were observed by Doppler radar in the location where deep convection is triggered several hours later. The results suggest that in many situations, observations of the location and timing of convergence lines will facilitate the nowcasting of convection. Further on, forecasting of the initiation of convection is significantly complicated if advection of potentially convective air masses over changing terrain features plays a major role. The passage of a frontal structure over the Vosges - Rhine valley - Black Forest orography was accompanied by an intermediate suppression of convection over the wide Rhine valley. Further downstream, an intensification of convection was observed over the Black Forest due to differential surface heating, a convergence line, and the flow generated by a gust front.

Kottmeier, C.; Kalthoff, N.; Barthlott, C.; Corsmeier, U.; Van Baelen, J.; Coulter, R.; Environmental Science Division; Inst. for Meteorology and Climate Research; Lab. de Meteorologie Physique; Inst. of Physics and Meteorology

2008-12-01

367

The Tropical Convective Spectrum. Part 1; Archetypal Vertical Structures  

NASA Technical Reports Server (NTRS)

A taxonomy of tropical convective and stratiform vertical structures is constructed through cluster analysis of 3 yr of Tropical Rainfall Measuring Mission (TRMM) "warm-season" (surface temperature greater than 10 C) precipitation radar (PR) vertical profiles, their surface rainfall, and associated radar-based classifiers (convective/ stratiform and brightband existence). Twenty-five archetypal profile types are identified, including nine convective types, eight stratiform types, two mixed types, and six anvil/fragment types (nonprecipitating anvils and sheared deep convective profiles). These profile types are then hierarchically clustered into 10 similar families, which can be further combined, providing an objective and physical reduction of the highly multivariate PR data space that retains vertical structure information. The taxonomy allows for description of any storm or local convective spectrum by the profile types or families. The analysis provides a quasi-independent corroboration of the TRMM 2A23 convective/ stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types are presented, demonstrating primary rainfall contribution by midlevel glaciated convection (27%) and similar depth decaying/stratiform stages (28%-31%). Profiles of these types exhibit similar 37- and 85-GHz passive microwave brightness temperatures but differ greatly in their frequency of occurrence and mean rain rates, underscoring the importance to passive microwave rain retrieval of convective/stratiform discrimination by other means, such as polarization or texture techniques, or incorporation of lightning observations. Close correspondence is found between deep convective profile frequency and annualized lightning production, and pixel-level lightning occurrence likelihood directly tracks the estimated mean ice water path within profile types.

Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.

2005-01-01

368

A summary of research on mesoscale energetics of severe storm environments  

NASA Technical Reports Server (NTRS)

The goals of this research were to better understand interactions between areas of intense convection and their surrounding mesoscale environments by using diagnostic budgets of kinetic (KE) and available potential energy (APE). Three cases of intense convection were examined in detail. 1) Atmospheric Variability Experiments (AVE) carried out on 24 to 25 April 1975 were studied. Synoptic scale data at 3 to 6 hour intervals, contained two mesoscale convective complexes (MCCs). Analyses included total KE budgets and budgets of divergent and rotational components of KE. 2) AVE-Severe Environmental Storms and Mesoscale Experiments (SESAME)-4 carried out on 10 to 11 April 1979 were studied. Synotpic and meso alpha-scale data (250 km spacing, 3 hour intervals), contained the Red River Valley tornado outbreak. Analyses included total KE budgets (separate synoptic and mesoscale version), budgets for the divergent and rotational components, and the generation of APE by diabatic processes. 3) AVE-SESAME 5 studies were carried out on 20 to 31 May 1979. Synoptic and meso beta-scale data (75 km spacing, 1 1/2 to 3 hour intervals), contained a small MCC. Analyses include separate KE budgets for the synotic and meso beta-scales and a water vapor budget. Major findings of these investigations are: (1) The synoptic scale storm environment contains energy conversions and transports that are comparable to those of mature midlatitude cyclones. (2) Energetic in the mesoscale storm environment are often an order of magnitude larger than those in an undisturbed region. (3) Mesoscale wind maxima form in the upper troposphere on the poleward sides of convective areas, whereas speeds decrease south of storm regions.

Fuelberg, H. E.

1985-01-01

369

Deep Convective Clouds  

NSDL National Science Digital Library

Convective clouds are clouds that develop vertically appearing like big stacks of clouds. One very common example is cumulonimbus clouds. Convective clouds are commonly connected to stormy weather. Monthly Cloud Coverage for Deep Convective Cloud data can be used to predict patterns in weather. The specific pattern associated with this data is tracking and predicting thunderstorms. In this lesson, the students will take a look at the Monthly Cloud Coverage for Deep Convective Cloud data, and name one month of the year 'Thunderstorm Season' for their continent.

370

A coordinated study of a storm system over the South American continent. I. Weather information and quasi-dc stratospheric electric field data  

SciTech Connect

A coordinated campaign conducted in Brazil on 13 December 1989, to study the electrical signals associated with a large storm system over the South American continent is presented. Within the storm, large convective cells developed extending up to the tropopause, as observed from meteorological balloon soundings. The analysis of IR imagery supports the general tendency for lightning strikes to be close to but not exactly beneath the coldest cloud tops. 35 refs.

Pinto, O. Jr.; Pinto, I.R.C.A.; Gin, R.B.B.; Mendes, O. Jr. (INPE, Sao Jose dos Campos (Brazil))

1992-11-01

371

A coordinated study of a storm system over the South American continent. 1. Weather information and quasi-DC stratospheric electric field data  

Microsoft Academic Search

This paper reports on a coordinated campaign conducted in Brazil, December 13, 1989, to study the electrical signatures associated with a large storm system over the South American continent. Inside the storm, large convective cells developed extending up to the tropopause, as revealed from meteorological balloon soundings. Quasi-DC vertical electric field and temperature were measured by zero-pressure balloon-borne payload launched

O. Jr. Pinto; I. R. C. A. Pinto; R. B. B. Gin; O. Jr. Mendes

1992-01-01

372

RECOVERY OF MONTEREY BAY BEACHES AFTER THE WINTER STORMS OF 1982-83.  

USGS Publications Warehouse

The El Nino conditions of 1982 and 1983 produced unusually frequent and intense storms along the central California coast. These storms produced much greater than normal beach erosion in Monterey Bay, causing extensive damage to coastal structures, erosion of coastal cliffs, and loss of sand from coastal dunes. The beaches accreted during the summer of 1983 and eroded again the next winter. Every beach, however, showed its own pattern of rebuilding; the eigenfunction analysis showed that the beaches did not all reach either their maximum or minimum volumes at the same time.

Dingler, John, R.; Anima, Roberto, J.; Clifton, H. Edward

1985-01-01

373

Seasonal march of Asian summer monsoon  

NASA Astrophysics Data System (ADS)

This paper investigates the seasonal march of the summer monsoon through several different sub-divisions of the Asian monsoon region. Five data sets, the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), the upper-tropospheric water vapour band Brightness Temperature (BT), the Outgoing Longwave Radiation (OLR), the lower tropospheric wind and Korean daily rainfall for 1980-1995, are used.Analysis shows that the largest area of deep convection in the global atmosphere is located over the tropical Indian Ocean-equatorial western Pacific; its centre being positioned 110°E along the equator in boreal winter and then moves northwestward to 80°E at 5°N in late July. In late April, the area of deep convection first extends northward into the Indo-China Peninsula (ICP). In mid-May it abruptly covers over the central South China Sea (SCS) region. After the onset of SCS monsoon, deep convection starts to develop northward along the eastern coast of China, East Tibet Plateau (ETP) and Indian sub-continent, simultaneously. Based on the analysis of BT and lower-tropospheric circulation, Asian summer monsoon can be divided into six inter-linked sub-regional monsoons. They are Indo-China Peninsula monsoon, SCS monsoon, South Asian (Indian) monsoon, ETP monsoon, East Asian (south China, lower Yangtze River and Japan) monsoon and Northeast Asian (north China and Korea) monsoon. In seasonal course, their onset periods take place in late April-mid-May, mid-May, mid-May-late July, mid-May-early June, mid-May-late June and late June-mid-July, respectively.

Qian, Weihong; Lee, Dong-Kyou

2000-09-01

374

Suggested severe local storm operational scenario for GOES I-M  

NASA Technical Reports Server (NTRS)

The GOES I-M satellite system is expected to provide continuous high resolution estimates of temperature and moisture profiles, winds from cloud motions, surface temperature, cloud properties, and precipitation for severe local storm and tropical cyclone events. The suggested operational schedule for the GOES I-M satellite emphasizes the observation frequencies, spatial coverage, spectral bands, etc. for the GOES I-M imager and sounder instruments that are expected to optimize the determination of the relevant meteorological parameters. During severe local storm events, the imager would be programmed to perform high frequency imaging (less than or= 3.5 min) for determining winds from cloud motions and for monitoring severe convection. In addition, the sounder would provide temperature and moisture profiles every hour over a 3000 X 3000 km domain during the antecedent stage or over a 1000 X 1000 km area every 10 minutes during the mature storm stage.

Shenk, William E.; Mosher, Fredrick

1987-01-01

375

Effects of Tropospheric Wind Shear on the Spectrum of Convectively Generated Gravity Waves.  

NASA Astrophysics Data System (ADS)

The authors examine the effects of tropospheric wind shear on the phase speed spectrum of gravity waves generated by tropical convection. A two-dimensional cloud-resolving model is used to perform numerous squall line simulations with the vertical shear of the horizontal wind varied in three layers of the troposphere. Several simplified simulations using prescribed heating are also performed to elucidate the interactions of wind shear with thermal forcing. It is found that the dominant phase speed range of convectively generated stratospheric gravity waves is primarily determined by the vertical scale of the tropospheric heating and is then modified by the tropospheric wind. The gravity wave spectrum is especially sensitive to shear in the upper troposphere. Through a mechanism similar to critical level filtering, such shear acts to reduce the momentum flux of waves propagating in the same direction as the storm-relative mean wind. Through interaction with convective turrets, shear in the upper troposphere increases the momentum flux of waves propagating opposite to the storm-relative mean wind (the `obstacle effect'). The resulting spectrum of momentum fluxes produced by convectively generated gravity waves is generally not symmetric in the east and west directions; the east-west asymmetry depends primarily on the difference between the wind above the storm and the storm's motion. Thus, it is important that the effects of tropospheric wind shear be included in any attempt to parameterize the effects of gravity wave stress and turbulence in general circulation models.

Beres, Jadwiga H.; Alexander, M. Joan; Holton, James R.

2002-06-01

376

Evaluation of the model representation of the evolution of convective systems using satellite observations of outgoing longwave radiation  

NASA Astrophysics Data System (ADS)

We introduce a technique for assessing the diurnal development of convective storm systems based on outgoing longwave radiation fields. Using the size distribution of the storms measured from a series of images, we generate an array in the length scale-time domain based on the standard score statistic. It demonstrates succinctly the size evolution of storms as well as the dissipation kinematics. It also provides evidence related to the temperature evolution of the cloud tops. We apply this approach to a test case comparing observations made by the Geostationary Earth Radiation Budget instrument to output from the Met Office Unified Model run at two resolutions. The 12 km resolution model produces peak convective activity on all length scales significantly earlier in the day than shown by the observations and no evidence for storms growing in size. The 4 km resolution model shows realistic timing and growth evolution, although the dissipation mechanism still differs from the observed data.

Pearson, K. J.; Hogan, R. J.; Allan, R. P.; Lister, G. M. S.; Holloway, C. E.

2010-10-01

377

Military Review: Desert Shield/Desert Storm.  

National Technical Information Service (NTIS)

CONTENTS: CASCOM Support for DESERT SHIELD/DESERT STORM; Total Army CSS: Providing the Means for Victory; Logistics Automation Support for Desert Storm; Building the DESERT Logistics force; Depot operations Supporting DESERT SHIELD; The Readiness Group's ...

1991-01-01

378

Satellite View of 2 Trop. Storms  

NASA Video Gallery

System 98L exploded into Tropical Storm Irene on Saturday, August 20. This GOES-13 Video shows Tropical Storm Harvey making landfall in Belize (just beneath the Yucatan Peninsula) and moving into t...

379

Tropical Storm Debby Moves into Atlantic  

NASA Video Gallery

An animation of satellite observations shows the progression of Tropical Storm Debby from June 25-27, 2012. The animation shows that Tropical Storm Debby's center move from the northeastern Gulf of...

380

Multi-Sensor Analysis of Overshooting Tops in Tornadic Storms  

NASA Astrophysics Data System (ADS)

The disastrous 2011 tornado season focused much attention on the ~75% false alarm rate for NWS-issued tornado warnings. Warnings are correctly issued on ~80% of verified tornados, but the false alarm rate has plateaued at near 75%. Any additional clues that may signal tornadogenesis would be of great benefit to the public welfare. We have performed statistical analyses of the structure and time-evolution of convective overshooting tops for tornadic storms occurring in the continental United States since 2006. An amalgam of case studies and theory has long suggested that overshooting tops may often collapse just prior to the onset of tornado touchdown. Our new results suggest that this view is supported by a broad set of new statistical evidence. Our approach to the analysis makes use of a high resolution, multi-sensor data set, and seeks to gather statistics on a large set of storms. Records of 88-D NEXRAD radar Enhanced-Resolution Echo Tops (product available since 2009) have been analyzed for an hour prior to and following touchdown of all EF1 and stronger storms. In addition, a coincidence search has been performed for the NASA A-Train satellite suite and tornadic events since 2006. Although the paths of the polar-orbiting satellites do not aid in analyses of temporal storm-top evolution, Aqua-MODIS, CALIPSO, and Cloud-Sat have provided a detailed structural picture of overshooting tops in tornadic and non-tornadic supercell thunderstorms. 250 m resolution AQUA-MODIS image at 1950Z on 4/27/2011, color-enhanced to emphasize overshooting tops during tornado outbreak.

Magee, N. B.; Goldberg, R.; Hartline, M.

2012-12-01

381

Is Titan's dune orientation controlled by tropical methane storms?  

NASA Astrophysics Data System (ADS)

Titan's equatorial regions are covered by eastward oriented linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs) at these latitudes, oriented westward as trade winds on Earth [1, 2]. Here, we propose that Titan's dune orientation is actually determined by equinoctial tropical methane storms. Using meso-scale simulations of convective methane clouds [3, 4] with a GCM wind profile featuring the super-rotation [5, 6], we show that Titan's storms should produce fast eastward gust fronts above the surface (see Figure 1). Such gusts dominate the aeolian transport. Using GCM wind roses and analogies with terrestrial dune fields as the Rub' al-Khali desert, we show that under these conditions Titan's dune growth occurs eastward (see Figure 2). Moreover, we explain other features of Titan's dunes (i.e. divergence from the equator, size and spacing). This analysis therefore reveals an unexpected coupling between super-rotation, tropical storms and dune formation on Titan, and has implications for the understanding of terrestrial dunes. References: [1] Lorenz et al. (2006) Science [2] Lorenz & Radebaugh (2009) Geophysical Research Letter [3] Barth & Rafkin (2007) Geophysical Research Letter [4] Barth & Rafkin (2010) Icarus [5] Charnay & Lebonnois (2012) Nature Geoscience [6] Lebonnois et al. (2012) Icarus Development of a methane storm with formation of a gust front. Colorbar corresponds to the mixing ratio of condensed methane (in g/kg) Resultant drift direction obtained by combining the GCM sand flux roses with the impact of one gust front every equinox at any location.

Charnay, B.; Barth, E. L.; Rafkin, S. C.; Narteau, C.; Lebonnois, S.; Rodriguez, S.

2013-12-01

382

Auroral Zone E-Region Electron Density Geomagnetic Storm Enhancements Predicted by the Empirical STORM-E Model  

NASA Astrophysics Data System (ADS)

Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E. The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) volume emission rates (VER) derived from the TIMED/SABER 4.3 um channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 um VER is most sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 um VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. In this paper, the development of the E-region electron density storm-time correction factor is described. The STORM-E storm-time correction factor is fit to a single geomagnetic index. There are four versions of the STORM-E model. Each version is fit to one of the following indices: HP-, AE-, Ap-, or Dst. High-latitude incoherent scatter radar (ISR) E-region electron density measurements are compared to STORM-E predictions for various geomagnetic storm periods during solar cycle 23. These comparisons show that STORM-E significantly improves the prediction of E-region electron density enhancements due to auroral particle precipitation, in comparison to the nominal International Reference Ionosphere (IRI) model or to the quiet-time baseline electron density concentrations measured by ISR. The version of the STORM-E model based on the fit to the Ap-index is now incorporated into the 2012 release of the IRI.

Mertens, Christopher; Bilitza, Dieter; Xu, Xiaojing

2012-07-01

383

Making Summer Count: How Summer Programs Can Boost Children's Learning  

ERIC Educational Resources Information Center

During summer vacation, many students lose knowledge and skills. By the end of summer, students perform, on average, one month behind where they left off in the spring. Participation in summer learning programs should mitigate learning loss and could even produce achievement gains. Indeed, educators and policymakers increasingly promote summer

McCombs, Jennifer Sloan; Augustine, Catherine; Schwartz, Heather; Bodilly, Susan; McInnis, Brian; Lichter, Dahlia; Cross, Amanda Brown

2012-01-01

384

Overshooting Convection from High-Resolution NEXRAD Observations  

NASA Astrophysics Data System (ADS)

Convection can rapidly and irreversibly transport tropospheric air into the upper troposphere and, in some cases, through the tropopause into the lower stratosphere. Previous studies have shown that stratosphere-troposphere exchange of any kind can have a significant impact on the composition of the upper troposphere and lower stratosphere. This will in turn affect the climate, chemistry, and radiation budget of the atmosphere. In order to understand the importance of convective transport on the composition of the lower stratosphere, it is necessary to know the frequency, magnitude, and location of overshooting convection events. A new method that combines radar reflectivities from individual radars into a three-dimensional composite with high vertical resolution is used to obtain storm top altitudes. Analyses of background atmospheric conditions and the tropopause height are done using the ERA-Interim reanalysis. We compute a 1-year analysis of overshooting convection at six-hour intervals for 2004 for the continental U.S. east of the Rocky Mountains. Overshooting convection is most common over the high plains. There is a pronounced seasonal cycle with the majority of overshooting systems occurring during the warm season. We will also discuss the diurnal pattern of overshooting convection and estimate the mass flux of tropospheric air into the lower stratosphere as a function of altitude above the tropopause.

Solomon, D.; Bowman, K. P.; Homeyer, C. R.

2013-12-01

385

Regional variation of morphology of organized convection in the tropics and subtropics  

NASA Astrophysics Data System (ADS)

Properties of organized convection with large horizontal area (> 1000 km2) and with different horizontal structures in the tropics and subtropics are investigated by using 14 years of Tropical Rainfall Measuring Mission observations. First, the convective features (CFs) are defined as contiguous areas of convective precipitation detected by the Tropical Rainfall Measuring Mission precipitation radar. Using the minor and major axes of fitted ellipses, the morphology of the CFs are described as closer to a circular or a line shape. Regional variations and the properties of organized convection are examined with CFs with area > 1000 km2 after categorizing them by their shapes. Organized convection tends to have larger extent and a higher fraction of near-circular shapes over land than over ocean. Shallow organized convection with maximum radar echo top height below 4.5 km is found mainly over ocean and some coastal regions. Of all tropical oceans, most shallow organized convection is found over the east Pacific. The fraction of line shaped organized convection is higher over the ocean than over land, and is higher in the subtropics than in the tropics. More convective lines are found in winter than in summer over oceans, but more in summer over land. Organized convective lines are slightly less convectively intense indicated by lower 30 dBZ echo top heights and warmer 37 GHz brightness temperatures than those with near-circular shapes. Orientations of organized convective lines are often aligned with fronts, dry lines, warm ocean currents, coastlines, and mountain slopes. Over the subtropics, organized convective lines are tilted more east-west over land, and more north-south over oceans. The largest and the most intense convective lines are found over central Africa, Argentina, and southeast U.S. over land, and over several warm currents in subtropical oceans.

Liu, Chuntao; Zipser, Edward

2013-01-01

386

Radar reflectivities and satellite imagery of severe storms 20 May 1977  

NASA Technical Reports Server (NTRS)

Storms on 20 May 1977 generated a vast cirrus deck. Disturbed areas at storm top had equivalent black-body temperatures (T sub BB) much lower than the tropopause temperature, indicative of overshooting tops. The area of T sub BB not greater than -71 C represents the area of convective activity penetrating 2 km above the tropopause. This area was relatively large after cloud tops and radar reflectivities reached their maximum heights. It became much smaller during tornadoes when reflectivities were decreasing. T sub BB was at a minimum at the time of mesocyclone formation. The Del City storm had two periods of growth, as indicated both by reflectivities and the T sub BB areas. The mesocyclone was first detected during the second less intense period of growth; the tornado occurred during decreasing reflectivities. The maintenance of large areas of relatively low T sub BB after tornado dissipation is ascribed to continued convection on the flanks of the storm and to residual updrafts in a thick anvil cloud.

Wexler, R.; Blackmer, R. H., Jr.

1982-01-01

387

The Role of Surface Wet Bulb Temperature For Subsequent Convective Rainfall In Midlatitudes  

NASA Astrophysics Data System (ADS)

Previous research suggests that in the tropics there is a relation between convec- tive available potential energy (CAPE) and the amount of (convective) precipitation. CAPE, in turn, is related to the wet bulb temperature in the boundary layer. The present work tries to find out whether similar relations hold in midlatidues regarding summer- time convective precipitation, focussing on the Alpine regione in a first step. To this end standard meteorological observations from Austria are analyzed. From hourly measurements of relative humidity, air pressure and temperature the wet bulb temperature is computed and related to the observed rainfall. The time series encom- passes the summer month between 1990 and 2001. Comparison between convective and non-convective precipitation events allows one to quantify the extent to which high values of surface wet bulb temperature leads to enhanced convective precipita- tion.

Früh, B.; Wirth, V.

388

Distribution of auroral precipitation at midnight during a magnetic storm  

SciTech Connect

On the night of November 4, 1986, a very complex precipitation pattern was observed by Viking in the magnetic midnight sector over Scandinavia and Svalbard. The pass took place during a magnetic storm, and during substorm recovery phase. Going from north to south, the satellite first encountered a plasma region of BPS-type (name derived from boundary plasma sheet) and then a region of CPS type (derived from central plasma sheet). Then, however, a new region of BPS-type was traversed. The quite intense, most equatorward aurora corresponded to a plasma region which was not of ordinary CPS type but contained sharp quasi-monoenergetic peaks. The high-latitude midnight sector was totally dominated by eastward convection. The Harang discontinuity had passed northern Scandinavia the first time as early as 17 to 20 MLT, more than three house before the Viking pass. It is suggested that the particle precipitation pattern and the general shape of the aurora as observed by the Viking imager can be explained in a natural way by the convection pattern. The northernmost BPS- and CPS-type regions originated in the morningside convection cell, while the more equatorward population of BPS type had drifted in from the eveningside. The interpretation is supported by ground-based measurements by EISCAT and magnetometers.

Sandahl, I.; Eliasson, L.; Pellinen-Wannberg, A. (Swedish Inst. of Space Physics, Kiruna (Sweden)); Rostoker, G. (Univ. of Alberta, Edmonton (Canada)); Block, L.P. (Royal Inst. of Tech., Stockholm (Sweden)); Erlandson, R.E. (Johns Hopkins Univ., Laurel, MD (United States)); Friis-Christensen, E. (Danish Meteorological Inst., Copenhagen (Denmark)); Jacobsen, B. (Univ. of Oslo (Norway)); Luehr, H. (Technischen Univ., Braunschweig (West Germany)); Murphree, J.S. (Univ. of Calgary, Alberta (Canada))

1990-05-01

389