Upper-air Charts Research Articles

Cloudburst events observed over Uttarakhand during monsoon season 2017 and their analysis

Cloudburst is an extreme weather event characterised by the occurrence of a large amount of rainfall over a small area within a short span of time with a rainfall of 100 mm or more in one hour. It is responsible for flash flood, inundation of low lying areas and landslides in hills causing extensive damages to life and property. During monsoon season 2017 five number of cloudburst events are observed over Uttarakhand and analysed. Self Recording Rain Gauge (SRRG) and 15 minutes interval data from the newly installed General Packet Radio Service (GPRS) based Automatic Weather Station (AWS) are able to capture the cloudburst events over some areas in Uttarakhand. In this paper, an attempt has been made to find out the significant synoptic and thermodynamic conditions associated with the occurrence of the cloudburst events in Uttarakhand. These 5 cases of cloudburst events that are captured during the month of June, July and August 2017 in Uttarakhand are studied in detail. Synoptically, it is observed that the existence of trough at mean sea level from Punjab to head Bay of Bengal running close to Uttarakhand, the movement of Western Disturbance over north Pakistan and adjoining Jammu & Kashmir and existence of cyclonic circulation over north Rajasthan and neighbourhood are favourable conditions. Also, the presence of strong south-westerly wind flow from the Arabian Sea across West Rajasthan and Haryana on upper air charts are found during these events. Thermodynamically, the Convective Available Potential Energy (CAPE) is found to be high (more than 1100 J/Kg) during most of the cases and vertically integrated precipitable water content (PWC) is more than 55mm. The GPRS based AWS system can help in prediction of the cloud burst event over the specified location with a lead time upto half to one hour in association with radar products.

ТЕОРІЯ І ПРАКТИКА РОЗХОДЖЕННЯ СУДНА З ТАЙФУНОМ

Tropical cyclone, also called typhoon or hurricane, an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain. Drawing energy from the sea surface and maintaining its strength as long as it remains over warm water, a tropical cyclone generates winds that exceed 119 km (74 miles) per hour. In extreme cases winds may exceed 240 km (150 miles) per hour, and gusts may surpass 320 km (200 miles) per hour. Accompanying these strong winds are torrential rains and a devastating phenomenon known as the storm surge, an elevation of the sea surface that can reach 6 metres (20 feet) above normal levels. Such a combination of high winds and water makes cyclones a serious hazard for coastal areas in tropical and subtropical areas of the world. Every year during the late summer months (July-September in the Northern Hemisphere and January-March in the Southern Hemisphere), cyclones strike regions as far apart as the Gulf Coast of North America, northwestern Australia, and eastern India and Bangladesh. Today, the Меtеorologiсal Agency provides ships with information on oсеaniс mеtеorologiсal conditions, such as surfaсе weather charts, upper-air charts, oсеan wavе charts, photographs from weather satellites, and so on. Thеrеforе, for the purpose of providing ships with more aссuratе information on oсеaniс mеtеorologiсal conditions, wеathеr observations and reports will continue to be of vital importance. Seafarers are required not only to dеvеlope their mеtеorologiсal knowledge, but also to sееk to realize safe ship operations by making practical use of this knowledge. The general rules for avoiding tropical сyсlonеs or typhoons are summarized as follows: (a) If the wind сhangеs to сloсkwisе, the ship must be in the dangerous sеmiсirсlе. If possible, the ship should plaсе the wind on the starboard bow (45o relative), hold сoursе and make as much way as possible to get out of the dangerous zone; (b) If the wind backs the ship, the ship is in the navigable sеmiсirсlе. The ship should plaсе the wind on the starboard quarter (135o relative), hold сoursе and make as much way as possible. (This method of avoidanсе is сallеd scudding); (с) If the wind remains steady or nearly steady in terms of dirесtion, the ship should be in the path of the typhoon, ahead of the storm's center. In this сasе, the Master should dесidе in advanсе whether the ship is able to enter the navigable area of the typhoon safely or not. If this action is dееmеd praсtiсablе, the ship should plaсе the wind 2 points on the starboard quarter (about 160o relative), hold сoursе and make as much way as possible. When well within the navigable sеmiсirсlе, scudding is rесommеndеd; (d) If the ship is in the сеntеr, or near the сеntеr of the typhoon, the ship should have to with the wind on the starboard bow.

Investigation of Atmospheric Aerosol Size Distributions from Ground-Based Solar Spectrometer Measurements Synthesized with Satellite Data

Data collected by a ground-based solar spectrometer at Collegeville, MN, was used to generate Aerosol Optical Depths (AODs) throughout the 2017 calendar year. The AOD data was then visualized at 13 selected wavelengths throughout the year and analyzed in comparison to satellite imagery, upper air charts and backwards trajectories of air masses moving towards Central Minnesota in order to determine key dates of interest that correspond to times before (20170615), during (20170729), and at the conclusion of (20170914) forest fires that burned in British Columbia (BC) during the summer of 2017. The data from these specific days were analyzed further by inputting the maximum and minimum AODs for each day into a Parameter Based Particle Swarm Optimization (PBPSO) algorithm in order to generate bimodal lognormal particle size distributions. The bimodal distributions were chosen because they carry more information about the aerosol loads across the entire spectrum of particle radii. The resulting distributions show an increase in number density and decrease in median radius in the Aitken mode during the BC forest fires and a relatively constant (within uncertainty) number density of accumulation mode particles at daily maximum AODs. Comparing the resulting bimodal lognormal distribution for daily minimum AODs (where evaporation and other diurnal effects are at a minimum) shows an increased number density of Aitken mode particles by two orders of magnitude from pre- to post-forest fires. This measured increase in the number density of smaller radii particles due to forest fires illustrates the PBPSO’s capability of distinguishing variations in atmospheric aerosol particle number size distributions in the Aitken mode based on data collected by the Kipp-Zonen PGS-100 solar spectrometer. KEYWORDS: Atmospheric Aerosol; Particle Swarm Optimization; Aerosol Optical Depth; Solar Spectrometer; Size Distributions; Forest Fire; Satellite Imagery; Upper Air Charts; Backward Trajectory

Marine Oil Spill Simulation: A Scenario-Based Classroom Application of Meteorology and Oceanography to Environmental Protection

Predicting oil spill impacts and designing an effective response requires knowledge from several disciplines, including environmental chemistry, meteorology, oceanography, and marine ecology. In this poster, we describe an interactive computer modeling exercise that expands student understanding of principles in the natural sciences by applying them to an oil spill response scenario. The exercise is based on the software package, GNOME v.1.3.7, available from the National Oceanic and Atmospheric Administration (NOAA). Students begin by selecting one of numerous coastal locations in the United States and an oil product to be spilled (e.g., medium crude, diesel fuel, No. 6 fuel oil). They predict oil drift trajectories by accessing surface weather analysis charts, upper air charts, and marine forecasts produced by the National Weather Service as well as real-time oceanographic data available from NOAA's Data Buoy Center and the Tides and Currents database. Students consult the Atlas of Pilot Charts from the National Geospatial Intelligence Agency to evaluate any influence of large-scale currents. Drawing from knowledge of the chemical properties of oil, weathering processes, leeway, Ekman dynamics, tides, and geostrophic flow, students forecast the amount and location of oil remaining after 48 hours. Predictions are tested in GNOME, which simulates an oil spill with the chosen characteristics, at the chosen location, under the same environmental conditions. Based on the model results, students evaluate environmental impacts by referring to Environmental Sensitivity Index (ESI) maps for affected coastlines. These maps are available from NOAA's Office of Prevention and Response and contain site-specific information on shoreline habitat sensitivity, conservation status of biological populations, and location of vulnerable coastal infrastructure. Students prioritize areas for protection and design a response plan with appropriate clean-up countermeasures. Response plans are communicated to the instructor in the form of a recommendation addressed to the Captain of the Port. This exercise has been successfully incorporated into several courses at the Coast Guard Academy, with modifications to accommodate various audiences and learning objectives. All versions include multidisciplinary and collaborative learning techniques, higher-level cognitive thinking, and communication requirements. Data and software packages for this exercise are freely available from federal government websites, making possible its widespread use at other colleges and agencies seeking to provide students with hands-on opportunities to explore scientific concepts in the context of environmental protection.

A Climatology of Synoptic Conditions Associated with Significant Tornadoes across the Southern Appalachian Region

Abstract A 54-yr climatology (1950–2003) of synoptic conditions associated with significant (F2 or greater) tornado events in the southern Appalachian region was compiled to 1) investigate the observed relative minimum of tornadoes in the Great Tennessee Valley, 2) test a hypothesis concerning northwest versus southwest 500-hPa flow events across the Great Tennessee Valley and Cumberland Plateau, 3) examine common operational forecasting techniques often used with synoptic-scale data to determine potentially tornadic environments, and 4) compare the patterns associated with significant, outbreak, and weak tornado events. Individual surface and upper-air charts along with composite charts closest to the time of significant tornado occurrences were used in this investigation. It was found that significant tornado events that occurred with prefrontal troughs (the most common surface boundary in the study) produced significant tornadoes almost exclusively over the Cumberland Plateau and southern Appalachian Mountains, with very few prefrontal trough events producing significant tornadoes in the Great Tennessee Valley of eastern Tennessee. Only four northwest 500-hPa flow events (which produced significant tornadoes almost exclusively in the southern Appalachian Mountains and during the summer) were found in this study, which refuted the initial hypothesis that northwest 500-hPa flow may produce tornadoes mainly in the Great Tennessee Valley with southwest 500-hPa flow producing tornadoes mainly across the Cumberland Plateau. Most significant tornado events in this study were associated with southwest 500-hPa flow ahead of a neutral-tilted trough, which revealed that the particular tilt of a 500-hPa trough does not necessarily enhance the formation of significant tornadoes in the southern Appalachian region. However, outbreak events (with five or more significant tornadoes) in the southern Appalachian region were typically associated with positive-tilted troughs. At 300 or 250 hPa, the southern Appalachian region was frequently located on the right side of a jet streak, with an even split between the entrance and exit regions. This finding indicated that significant tornado events in the southern Appalachian region did not necessarily favor the right-entrance or left-exit regions of a jet streak where rising motion is expected to be most intense (with straight jet streaks). A comparison of the composites of weak, significant, and outbreak tornado events revealed that wind dynamics were more important than instability in the distinction between weak and significant tornado events across the southern Appalachian region.

The hurricane‐like Mediterranean cyclone of January 1995

AbstractThe development of a hurricane‐like vortex over the Mediterranean Sea was studied using (mainly) the UK Met. Office Unified Model. The Mediterranean cyclone formed in the morning of 15 January 1995 over the sea between Greece and Sicily. Strong convection was observed prior to its genesis. During the longest part of the cyclone's lifetime, strong surface fluxes and, as a result, deep convection existed in its vicinity. Its track was influenced by the surface fluxes and the flow in the wider region. The forecast of the mesoscale and limited‐area models reproduced the general characteristics of the actual system as they appeared at the surface and upper‐air charts and at the satellite imagery. The investigation of the cyclone's characteristics gave strong evidence (including an ‘eye’ and a warm core) to support the initial assertion that it was similar to tropical cyclones and some polar lows. Baroclinic instability does not seem particularly important, although the cyclone formed at the edge of a baroclinic zone. A numerical experiment showed the vortex did not develop in the absence of surface heat and moisture fluxes. Another experiment showed that sensible and latent heat fluxes were equally important in its development. Copyright © 2000 Royal Meteorological Society

A Preliminary Investigation and Diagnosis of Weak Shear Summertime Convective Initiation for Extreme Southwest Alabama

The initiation and location of summer season convective activity, occurring between 1500 and 1800 UTC within a 100-km radius of the Mobile, Alabama, National Weather Service WSR-88D radar site, was examined on days when weak vertical wind shear environments existed. Data were collected during June and July of 1996 based on 1200 UTC analyses of upper-air charts, radar, and GOES-8 satellite imagery. Thirteen case days were selected for detailed analysis. The precise location of initiation was found to be a function of both the 0‐1-km base-state flow and the extent of the flow’s interaction with physiographic features and local sea- and bay-breeze circulations. The modified mean 1800 UTC sounding for case days was characterized by a well-mixed boundary layer, a deep moistadiabatic lapse rate, and an overall decrease in relative humidity with height. For all case days, the surface parcel was found to be the most unstable air parcel within the mixed layer. A distinct bimodal distribution was found to exist in the 0‐1-km base-state wind flow pattern with flow predominantly east-southeast or westsouthwest. Thunderstorms were observed to initiate in a ‘‘mirror image’’ pattern on either side of Mobile Bay and were focused near elevation peaks, along the sea breeze, and at or near the orthogonal intersection of the sea- and bay-breeze circulations on either side of the bay.

History of Pressure Pattern Navigation

Inflight pressure pattern navigation was initiated in 1943 when readings of an aircratYs pressure and radar altimeters were first utilized to determine the socalled “Bellamy Drift” and/or Pressure Lines of Position. This led to preflight planning of Single Heading Flights and Optimum Flight Planning based on the patterns of the contours of constant pressure upper air charts. The manually constructed “4D” charts for such manual flight planning have since been replaced by numerical weather predictions that, are used in computerized flight planning.. Such flight planning is complicated by a lack of coordination between the ways with which vertical positions are coordinated in aeronautical and meteoro- logical practice that might well be alleviated by tailoring prognostic pressure pattern data for aeronautical use.

Winds over Japan

Before World War II, weather forecasters had little knowledge of upper-air wind patterns above 20 000 feet. Data were seldom available at these heights, and the need was not great because commercial aircraft seldom flew at these altitudes. The war in the Pacific changed all that. Wind forecasts for 30 000 feet plus became urgent to support the XXI Bomber Command in its bombing mission over Japan. The U.S. Army Air Force Pacific Ocean Area (AAFPOA) placed a Weather Central in the Marianas Islands in 1944 (Saipan in 1944 and Guam in 1945) to provide forecasting support for this mission. A forecasting procedure was put into operation that combined the elements known as “single-station forecasting” and an advanced procedure that used “altimeter corrections” to analyze upper-air data and make prognoses. Upper-air charts were drawn for constant pressure surfaces rather than constant height surfaces. The constant pressure surfaces were tied together by means of the atmospheric temperature field represented by specific temperature anomalies between pressure surfaces. Wind forecasts over the Marianas-Japan route made use of space cross sections that provided the data to forecast winds at each 5000-ft level to 35 000 ft along the mission flight path. The new procedures allowed the forecaster to construct internally consistent meteorological charts in three dimensions in regions of sparse data. Army air force pilots and their crews from the Marianas were among the first to experience the extreme wind conditions now known as the “jet stream.” Air force forecasters demonstrated that, with experience, such winds could reasonably be forecast under difficult operational conditions.

Onset of the summer monsoon over White Sands Missile Range, New Mexico, as seen by VHF radar

A case study is presented of the onset of the seasonal transition from the dry conditions characteristic of early summer over southern New Mexico to the more humid conditions of late summer. Observations of Cn2 from the VHF radar wind profiler at White Sands Missile Range, New Mexico, are used as proxy indicators of humidity in the troposphere. The observations are made each 3 min at heights from about 5 to 20 km and are presented as hourly means. During June 1991, a sudden shift in the mean value of Cn2 of about 10 dB took place throughout the troposphere, in a time span of only a few hours. Surface and upper air charts, local weather observations, weather surveillance radar, and satellite imagery are used to establish the synoptic events associated with this shift. No distinct feature changed in the flow patterns aloft or in the analyzed air mass boundaries. The shift in moisture observed by the VHF radar is found to persist on time scales of a month or more from inspection of time series of precipitable water from radiosonde data at nearby El Paso, Texas.

A numerical frontal analysis scheme for operational interpretations of satellite pictures

A numerical analysis of fronts near the surface is obtained by using the calculus of front-parallel components and the external baroclinicity parameter following Wippermann. In the presented case study this analysis is applied to a case of convective developments at a frontal system and compared with a satellite picture (NOAA-9). Using numerically analyzed upper air charts, interactions between upper tropospheric motion and areal distribution of precipitation are presented.

Atmospheric dispersal and deposition of radioactive material from Chernobyl

This paper reports on the results of studies undertaken in the wake of the fire at the Chernobyl nuclear power station. Published upper air charts and the findings of scientists engaged in monitoring the fallout are used to reconstruct the clouds' trajectories. The results reveal the role of the various features of weather systems in determining the dispersal, transportation and ultimate fallout of radioactive matter. Most importantly, the situation over Europe at the time of the fire was such as to disperse the radioactive clouds northwards to Scandinavia and later westwards to Britain; directions counter to the dominant westerlies of these latitudes. However, eastwards global dispersal took place rapidly in the weeks following the fire. The paper also emphasizes the importance of rainfall in explaining the geographical variation in the deposition of radioactive material.

On the use and significance of isentropic potential vorticity maps

AbstractThe two main principles underlying the use of isentropic maps of potential vorticity to represent dynamical processes in the atmosphere are reviewed, including the extension of those principles to take the lower boundary condition into account. the first is the familiar Lagrangian conservation principle, for potential vorticity (PV) and potential temperature, which holds approximately when advective processes dominate frictional and diabatic ones. the second is the principle of ‘invertibility’ of the PV distribution, which holds whether or not diabatic and frictional processes are important. the invertibility principle states that if the total mass under each isentropic surface is specified, then a knowledge of the global distribution of PV on each isentropic surface and of potential temperature at the lower boundary (which within certain limitations can be considered to be part of the PV distribution) is sufficient to deduce, diagnostically, all the other dynamical fields, such as winds, temperatures, geopotential heights, static stabilities, and vertical velocities, under a suitable balance condition. the statement that vertical velocities can be deduced is related to the well‐known omega equation principle, and depends on having sufficient information about diabatic and frictional processes. Quasi‐geostrophic, semigeostrophic, and ‘nonlinear normal mode initialization’ realizations of the balance condition are discussed. an important constraint on the mass‐weighted integral of PV over a material volume and on its possible diabatic and frictional change is noted.Some basic examples are given, both from operational weather analyses and from idealized theoretical models, to illustrate the insights that can be gained from this approach and to indicate its relation to classical synoptic and air‐mass concepts. Included are discussions of (a) the structure, origin and persistence of cutoff cyclones and blocking anticyclones, (b) the physical mechanisms of Rossby wave propagation, baroclinic instability, and barotropic instability, and (c) the spatially and temporally nonuniform way in which such waves and instabilities may become strongly nonlinear, as in an occluding cyclone or in the formation of an upper air shear line. Connections with principles derived from synoptic experience are indicated, such as the ‘PVA rule’ concerning positive vorticity advection on upper air charts, and the role of disturbances of upper air origin, in combination with low‐level warm advection, in triggering latent heat release to produce explosive cyclonic development. In all cases it is found that time sequences of isentropic potential vorticity and surface potential temperature charts—which succinctly summarize the combined effects of vorticity advection, thermal advection, and vertical motion without requiring explicit knowledge of the vertical motion field—lead to a very clear and complete picture of the dynamics. This picture is remarkably simple in many cases of real meteorological interest. It involves, in principle, no sacrifices in quantitative accuracy beyond what is inherent in theconceptof balance, as used for instance in the initialization of numerical weather forecasts.

Hawaiian Winter Rainfall and its Relation to the Southern Oscillation

Abstract Regression analyses revealed significant variability during the winter months in the relationship between Hawaiian winter rainfall and the Southern Oscillation. Examination of daily surface and upper air charts indicated that the variability during winter is a consequence of a marked change from December to January in the upper tropospheric circulation pattern over the central subtropical North Pacific. In January and February, positive 200 mb geopotential height anomalies over the Hawaiian Islands are indicative of an intensification and eastward propagation of the western North Pacific subtropical ridge. Consequently, the storm track is north and cast of Hawaii and such months are dry in the Hawaiian Islands. However, in December, positive 200 mb geopotential height anomalies over Hawaii are not necessarily indicative of such an upper tropospheric circulation and such Decembers need not be dry. Therefore, even though the December through February Southern Oscillation Index is significantly corr...

CLOUD BAND MORPHOMETRY: AN ALTERNATIVE APPROACH TO SATELLITE IMAGE ANALYSIS

This research assesses the use of Cold Front Cloud Band (CFCB) morphometry as an indicator of the characteristics of air masses at cold fronts. Measurements of the configuration of the CFCB (i.e., length, width, length/width ratio, and radius of curvature) are made using GOES/SMS satellite imagery. CFCB height and air mass characteristics of temperature, specific humidity, 500 mb wind velocity, and 500 mb vorticity are derived from NWS surface and upper air charts. Nonparametric correlations are utilized to relate CFCB morphometric variables to the selected characteristics of maritime tropical (mT) and continental polar (cP) air masses as they meet to form cold fronts over the eastern United States. CFCB-Air Mass relationships resulting in higher correlations are examined through two series of interpretive tests. The stronger correlations imply a direct relationship between CFCB height and 500 mb vorticity and between CFCB length and cP specific humidity; and inverse relationships between both the CFCB le...

Transmission of sulfur dioxide on local, regional and continental scale

The transport, dispersion, transformation and removal i.e. the transmission of sulfur dioxide, depends on the scale of the pollution process and on the type of the source, too. To take these considerations into account, working formulas were developed to simulate the transmission on different scales. The overall decay and transformation rates were separated into terms of dry deposition, transformation during low (r.h. less than 90%) and high (r.h. more than 90%) humidity conditions and wet deposition, together with the respective time intervals during which the separate mechanisms were effective. The intervals were evaluated along the trajectories on surface and upper air charts. To simulate the transmission for continental scale pollution processes, 72 h, 8SO mb, isobaric, backward trajectories were constructed. For regional and local scale pollution processes trajectories were constructed on the basis of the surface wind pattern. The dispersion of the sulfur dioxide for the larger scale processes was taken into account by air trajectory box models, for the local process by Gaussian model. The removal processes were taken into account by using scale-dependent rate constants from the available current literature. By applying the transmission model presented here, four case studies showed good agreement between the measured (63 and l μg m −3) and calculated (63 and 7 μg m −3) sulfur dioxide concentrations, respectively and between measured turbidity parameters ( B = 0.308 and 0.072) and calculated paniculate sulfate concentrations (22 and 4μg m −3) respectively.

A study of active monsoon over India using satellite radiation data

Tiros VH radiation data in the 8-12 micron channel for the period 5-8 July 1963 has been analysed. This was a period of good monsoon activity in the Peninsula and central India, The I.R. analysis is compared with surface synoptic and upper air charts. The results indicate that the general height of tops of monsoon clouds is about 7.8 km and these clouds presumably do not extend much into the upper tropospheric easterlies. However, in the areas of localised heavy monsoon activity. the clouds extend at least as high as 12 km. The average size of such thick cloud clusters is of the order of 3 to 5 degrees of Lat/Long, across and !n some cases even more.

Some case studies of cirriform clouds over India during the winter period

A few cases of extensive formations of upper tropospheric clouds over north and central India during the winter of 1969- 70 were studied utilizing satellite pictures in conjunction with synoptic and upper air charts as well as aircraft reports and hourly observations from airport stations. The ground-observed cloud reports are compared with satellite pictures. The clouds were found to be associated with the jet stream and formed when large amplitude troughs extended into India and neighbourhood. The clouds were also organised in transverse as well as parallel modes; prevailing lapse rates and vertical wind shears have been found to be different in the two modes of organizations.

Synoptic flow perturbations over West Africa

Utilising wind data for the significant levels: 2 000 feet, 850, 700, 500, and 300 mbs, detailed analyses of West African upper-air charts reveal distinct features of the atmospheric flow, especially in connection with mid-tropospheric easterly wave activity over the area. The history of a semi-vortical perturbation whose motion was in rhythm with the propagation of a 700 mb easterly wave is described. It is concluded that an easterly wave model incorporating the 700 mb trough (and ridge) as integral feature(s) of the flow describes best the majority of significant weather zones and puts on a firmer basis the existence of westwards moving semi-vortical lines of thunderstorms frequently traversing the heart of West Africa during the rainy seasons. DOI: 10.1111/j.2153-3490.1970.tb00535.x

A computation of the evaporation in Southern Sweden during 1957

The monthly evaporation during 1957 from a region in Southern Sweden has been computed by means of studies of the precipitation and the net influx of water vapour into the area. Upper air charts have been used and from the geostrophic winds and humidity values the net flux has been computed twice a day. Various sources of error have been discussed, among them the effect of the ageostrophic component of the wind which for various reasons had to be neglected. No definite conclusion as to the importance of the ageostrophic component has been reached, but it seems likely that the errors caused are not very large in this area.The method seems useful even over the rather small area studied, but an improved network with denser observations is desirable. The evaporation was largest during July and August and smallest during the winter months. The contribution to the run-off was largest during July-October. During April and May the evaporation was even larger than the precipitation.The yearly value of evaporation agreed well with estimates from hydrologic studies.