Plume Cloud Research Articles

MCC’s First-Ever Observation of a High-Altitude Plume Cloud on Mars: Linkages with Space Weather?

MCC’s First-Ever Observation of a High-Altitude Plume Cloud on Mars: Linkages with Space Weather?

Deep Convolutional Neural Network for Plume Rise Measurements in Industrial Environments

Determining the height of plume clouds is crucial for various applications, including global climate models. Smokestack plume rise refers to the altitude at which the plume cloud travels downwind until its momentum dissipates and the temperatures of the plume cloud and its surroundings become equal. While most air-quality models employ different parameterizations to forecast plume rise, they have not been effective in accurately estimating it. This paper introduces a novel framework that utilizes Deep Convolutional Neural Networks (DCNNs) to monitor smokestack plume clouds and make real-time, long-term measurements of plume rise. The framework comprises three stages. In the first stage, the plume cloud is identified using an enhanced Mask R-CNN, known as the Deep Plume Rise Network (DPRNet). Next, image processing analysis and least squares theory are applied to determine the plume cloud’s boundaries and fit an asymptotic model to its centerlines. The z-coordinate of the critical point of this model represents the plume rise. Finally, a geometric transformation phase converts image measurements into real-world values. This study’s findings indicate that the DPRNet outperforms conventional smoke border detection and recognition networks. In quantitative terms, the proposed approach yielded a 22% enhancement in the F1 score, compared to its closest competitor, DeepLabv3.

Two Extratropical Pathways to Forcing Tropical Convective Disturbances

Abstract Observational evidence of two extratropical pathways to forcing tropical convective disturbances is documented through a statistical analysis of satellite-derived OLR and ERA5 reanalysis. The forcing mechanism and the resulting disturbances are found to strongly depend on the structure of the background zonal wind. Although Rossby wave propagation is prohibited in easterlies, modeling studies have shown that extratropical forcing can still excite equatorial waves through resonance between the tropics and extratropics. Here this “remote” forcing pathway is investigated for the first time in the context of convectively coupled Kelvin waves over the tropical Pacific during northern summer. The extratropical forcing is manifested by eddy momentum flux convergence that arises when extratropical eddies propagate into the subtropics and encounter their critical line. This nonlinear forcing has similar wavenumbers and frequencies with Kelvin waves and excites them by projecting onto their meridional eigenstructure in zonal wind, as a form of resonance. This resonance is also evidenced by a momentum budget analysis, which reveals the nonlinear forcing term is essential for maintenance of the waves, while the remaining linear terms are essential for propagation. In contrast, the “local” pathway of extratropical forcing entails the presence of a westerly duct during northern winter that permits Rossby waves to propagate into the equatorial east Pacific, while precluding any sort of resonance with Kelvin waves due to Doppler shifting effects. The intruding disturbances primarily excite tropical “cloud plumes” through quasigeostrophic forcing, while maintaining their extratropical nature. This study demonstrates the multiple roles of the extratropics in forcing in tropical circulations and illuminates how tropical–extratropical interactions and extratropical basic states can provide be a source of predictability at the S2S time scale. Significance Statement This study seeks to understand how circulations in the midlatitudes excite the weather systems in the tropics. Results show that the mechanisms, as well as the types of tropical weather systems excited, are strongly dependent on the mean large-scale wind structure. In particular, when the large-scale wind blows from east to west, a special type of eastward-moving tropical weather system, the Kelvin wave, is excited owing to its resonance with remote eastward-moving weather systems in the extratropics. On the contrary, when the average wind blows from west to east, midlatitude systems are observed to intrude into the lower latitudes and directly force tropical convection, the cloud plumes, while maintaining their extratropical nature. These results speak to how the midlatitudes can excite distinct types of tropical weather systems under different climatological wind regimes. Understanding these tropical weather systems and their interactions with the midlatitudes may ultimately help to improve predictions of weather beyond 2 weeks.

Reconstruction of a leaking gas cloud from a passive FTIR scanning remote-sensing imaging system.

The concentration-path-length product (CL) image of the leaking gas cloud measured by the passive Fourier transform infrared (FTIR) scanning remote-sensing imaging system has a low resolution. Gas cloud diffusion is affected by wind speed and direction, which makes it difficult to trace the source of a leakage. Therefore, we propose a method to reconstruct the CL image of the leaking gas cloud applied to the passive FTIR scanning remote-sensing imaging system. First, bicubic interpolation is employed to upsample the low-resolution CL image of gas clouds. Second, the maximum noise-equivalent concentration-path-length (NECL) product is used as a threshold to segment the high-resolution gas cloud image. Third, image morphology processing and the evaluation criteria of the leaking gas cloud are applied to detect the leaking gas cloud. Finally, the high-resolution CL image of the leaking gas cloud is superimposed onto the background image. The effectiveness of the reconstruction method is proven by the SF6 remote-sensing experiment and simulation. The results show that the proposed method should be effectively implemented to reconstruct the high-resolution CL image of the leaking gas cloud. The reconstructed leaking gas cloud plume, as well as the location of the leakage source, are quite obvious. The reconstruction method has been successfully applied to passive FTIR scanning remote-sensing imaging systems, with high accuracy, in real time, and with robustness.

Plume Height Time-Series Retrieval Using Shadow in Single Spatial Resolution Satellite Images

Volcanic plume height is a key parameter in retrieving plume ascent and dispersal dynamics, as well as eruption intensity; all of which are crucial for assessing hazards to aircraft operations. One way to retrieve cloud height is the shadow technique. This uses shadows cast on the ground and the sun geometry to calculate cloud height. This technique has, however, not been frequently used, especially not with high-spatial resolution (30 m pixel) satellite data. On 26 October 2013, Mt Etna (Sicily, Italy) produced a lava fountain feeding an ash plume that drifted SW and through the approach routes to Catania international airport. We compared the proximal plume height time-series obtained from fixed monitoring cameras with data retrieved from a Landsat-8 Operational Land Imager image, with results being in good agreement. The application of the shadow technique to a single high-spatial resolution image allowed us to fully document the ascent and dispersion history of the plume–cloud system. We managed to do this over a distance of 60 km and a time period of 50 min, with a precision of a few seconds and vertical error on plume altitude of ±200 m. We converted height with distance to height with time using the plume dispersion velocity, defining a bent-over plume that settled to a neutral buoyancy level with distance. Potentially, the shadow technique defined here allows downwind plume height profiles and mass discharge rate time series to be built over distances of up to 260 km and periods of 24 h, depending on vent location in the image, wind speed, and direction.

Electric discharge evidence found in a new class of material in the Chicxulub ejecta

Chicxulub impact (66 Ma) event resulted in deposition of spheroids and melt glass, followed by deposition of diamectite and carbonate ejecta represented by large polished striated rounded pebbles and cobbles, henceforth, called Albion Formation1 Pook’s Pebbles, name given from the first site identified in central Belize, Cayo District. Here we report that magnetic analysis of the Pook’s Pebbles samples revealed unique electric discharge signatures. Sectioning of Pook’s Pebbles from the Chicxulub ejecta from the Albion Formation at Belize showed that different parts of Pook’s Pebbles had not only contrasting magnetization directions, but also sharply different level of magnetizations. Such behavior is indicative of electric discharge taking place sometimes during the formation of the Chicxulub ejecta blanket. In addition, some of the Pook’s Pebbles’ surface had recrystallized down to 0.2 mm depth. This is evidence of localized extreme pressures and temperatures during the fluidized ejecta formation which was imprinted in the outer layer of Pook’s Pebbles. Recrystallization caused formation of nanophase iron along the surface, which was revealed by mapping of both natural remanent magnetization and of saturation remanence magnetization signatures. While the spheroids’ magnetization orientation is consistent with reversed magnetic field at the time of impact, the study of the Pook’s Pebbles provided, in addition, new evidence of electric charging during the vapor plume cloud processes.

Research on a Sudden Explosion and its Environmental Impact

A sudden blast was chosen as the studied topic. Also, one computer based virtual experimentation was used to estimate the dimensional impact of initial pollutant plume from blasts. Self-made method using Mathcad code was used to generate the output for the period of the first tenth of a second (1deci-second) to 1minute (60s) of the blast at the point source. It also depicted long-range air pollution travel within the first 1 to 10 minutes. In the case study, it assumed an average directional diffusivity of 1720 m2s-1 which is about 25 per cent of the average generated speed of common explosives. The newly developed model revealed a plume cloud impact of 6.8×107µgm-3 in the first 1millisecond (0.01s) which decayed suddenly to a value of 1.7×107µgm-3 in the first 1decisecond (0.1s). The impact concentration at the point source by the end of the first second (1.0s) was 3.2×105µgm-3 which implied a 99.5% sudden decay when compared to 0.01s concentration value at the emission point source. Computerized experiments observed that air pollutants release from explosives/blasts were dispersed into the atmosphere in the first few seconds by forceful injection instead of by gradual dispersion as is the case with normal air pollutants plume releases.

A new approach to investigate an eruptive paroxysmal sequence using camera and strainmeter networks: Lessons from the 3–5 December 2015 activity at Etna volcano

Explosive sequences are quite common at basaltic and andesitic volcanoes worldwide. Studies aimed at short-term forecasting are usually based on seismic and ground deformation measurements, which can be used to constrain the source region and quantify the magma volume involved in the eruptive process. However, during single episodes of explosive sequences, integration of camera remote sensing and geophysical data are scant in literature, and the total volume of pyroclastic products is not determined. In this study, we calculate eruption parameters for four powerful lava fountains occurring at the main and oldest Mt. Etna summit crater, Voragine, between 3 and 5 December 2015. These episodes produced impressive eruptive columns and plume clouds, causing lapilli and ash fallout to more than 100 km away. We analyse these paroxysmal events by integrating the images recorded by a network of monitoring cameras and the signals from three high-precision borehole strainmeters. From the camera images we calculated the total erupted volume of fluids (gas plus pyroclastics), inferring amounts from 1.9×109 m3 (first event) to 0.86×109 m3 (third event). Strain changes recorded during the first and most powerful event were used to constrain the depth of the source. The ratios of strain changes recorded at two stations during the four lava fountains were used to constrain the pyroclastic fraction for each eruptive event. The results revealed that the explosive sequence was characterized by a decreasing trend of erupted pyroclastics with time, going from 41% (first event) to 13% (fourth event) of the total erupted pyroclastic volume. Moreover, the volume ratio fluid/pyroclastic decreased markedly in the fourth and last event. To the best of our knowledge, this is the first time ever that erupted volumes of both fluid and pyroclastics have been estimated for an explosive sequence from a monitoring system using permanent cameras and high precision strainmeters. During future explosive paroxysmal sequences this new approach might help in monitoring their evolution also to understand when/if they are going to finish. Knowledge of the total gas and pyroclastic fractions erupted during each lava fountain episode would improve our understanding of their processes and eruptive behaviour.

Modelling and simulation of continuous dense gas leakage for emergency response application

This paper aims to provide a solution for the simulation of continuous dense gas leak dispersion especially in emergency response applications. In the proposed solution, a modified plate model is presented and a dynamic simulation method is developed. To validate the performance of the modified model, its predicted concentrations are compared with both the original plate model and 19 sample concentrations from 6 trials of the publicly available Burro and Coyote field experiments. The results show that the modified model has better results than the original plate model, and could satisfactorily simulate the measured concentrations with 89.5% of the predictions within a factor of 2.5 of the observations and 94.7% within a factor of 5. Finally, a case study of a hydrogen sulfide leak accident is performed and the cloud plumes at different times (5 min, 10 min, 20 min, 30 min, 40 min) after the leakage are successfully obtained. It is very important for the real engineering application that each simulation process is very quick and take only a few seconds. In addition, the simulation results are visualized on Google Earth for a better user experience.

Conversion of simulated radioactive pollutant gas concentrations for a complex building array into radiation dose

Methods used to convert wind tunnel and ADMS concentration field data for a complex building array into effective radiation dose were developed based on simulations of a site in central London. Pollutant source terms were from positron emitting gases released from a cyclotron and clinical PET radiotracer facility. Five years of meteorological data were analysed to determine the probability distribution of wind direction and speed. A hemispherical plume cloud model (both static and moving) was developed which enabled an expression of gamma-ray dose, taking into account build-up factors in air, in terms of analytic functions in this geometry. The standard building wake model is presented, but this is extended and developed in a new model to cover the concentration field in the vicinity of a roof top structure recirculation zone, which is then related to the concentration in the main building wake zone. For all models presented the effective dose was determined from inhalation, positron cloud immersion and gamma ray plume contributions. Results of applying these models for determination of radiation dose for a particular site are presented elsewhere.

Virtual Assessment of air Pollution Dispersion from Anthropogenic Sudden Explosion

The control of air pollutants from anthropogenic sources seems almost impossible due to numerous influencing factors present in the atmosphere. In this study, we carried out a virtual mathematical experimentation using Math CAD, Mat lab and analytical approximation to estimate the dimensional impact of initial pollutant plume cloud from a sudden volcanic blast and the dynamics of its wind field. The high point of the experimentation is the period of the first one-tenth of a second (1 decisecond) to 1 min (60 s) of the blast at the point source. We also assessed the long range air pollution dispersion within the first 1 to 10 min of plume cloud released under practical assumptions. The model revealed a plume cloud impact of 6.8×107 μgm−3 in the first 1 millisecond (0.01 s) which decayed suddenly to a value of 1.7×107 μgm−3 in the first 1 deci-second (0.1 s). The impact concentration at the point source by the end of the first second (1.0 s) was 3.2×105 μgm−3 which implied a 99.5% sudden decay when compared with 0.01 s concentration value at the emission point source. It is observed that air pollutants released from explosives/blasts get transported into the atmosphere in the first few seconds by forceful injection instead of by gradual dispersion as is the case with normal air pollutants plume releases. A mathematical control process was propounded (which is still subject to further research) to reduce the quick flow of air pollutants

Cloud Trails Past the Lesser Antilles

Abstract Observations and cloud-resolving simulations of elongated cloud plumes (or “cloud trails”) past the Lesser Antilles islands in the Caribbean Sea are presented. Analysis of one year of visible satellite images reveals that each island forms cloud trails on 30%–40% of days, typically in the afternoon in response to diurnal island heating. On around 10% of days the cloud bands are very well organized, with lengths of and durations of min. Radiosonde analysis suggests that the well-organized events are favored by moderate-to-strong trade winds (6–10 m s−1) and stronger trade inversions. The simulated cloud trails, which are consistent with observations in their morphology and diurnal cycle, are organized by quasi-linear bands of thermally forced convergence within the heated island wake. They are sensitive to overland surface fluxes, inversion strength and height, terrain height, and trade-wind speed. While surface fluxes control the strength of the wake thermal circulations, the inversion controls precipitation and the disruption of cloud trails by subcloud cold pools. The impacts of terrain height and wind speed are multifaceted, including control over (i) the mechanical flow regime, (ii) the intensity of wake turbulence, (iii) the cloud-trail length, (iv) the wake thermal anomaly, and (v) elevated-heating effects (which strengthen the thermal convergence). Dimensional analysis is used to develop empirical scalings for the wake thermal circulation, which describe the suite of numerical sensitivity tests reasonably well.

Vertical velocity in shallow convection for different plume types

AbstractThis study investigates the bulk budgets of the vertical velocity and its parameterization in convective cores, convective updrafts, and clouds by using large‐eddy simulation (LES) of four shallow convection cases in the Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) programs. The relative magnitudes of the dominant momentum budget terms for the three types of plumes are presented. For all shallow cumulus except stratocumulus, the buoyancy force and the subplume transport in the core plume are the momentum source that offset the pressure gradient force. In the cloud updraft and cloud plumes, the buoyancy source is dominant in the lower and middle parts of the clouds, while the subgrid transport is a dominant source in the upper part, and the entrainment term is also a momentum source. For the stratocumulus, the subplume transport is a sink almost in the whole convective layer. For all types of plumes, the Simpson and Wiggert (1969) equation is found to be good paramaterization of the mean plume vertical velocity when appropriate scaling coefficients to buoyancy and entrainment terms are used. Optimal forms of the Simpson and Wiggert equation are given for convective cores, convective updrafts, and convective clouds. Results are compared with other studies published in the literature.

The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis

Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

Modification of the Atmospheric Boundary Layer by a Small Island: Observations from Nauru

Abstract Nauru, a small island in the tropical Pacific, generates cloud plumes that may grow to over 100-km lengths. This study uses observations to examine the mesoscale disturbance of the marine atmospheric boundary layer by the island that produces these cloud plumes. Observations of the surface layer were made from two ships in the vicinity of Nauru and from instruments on the island. The structure of the atmospheric boundary layer over the island was investigated using aircraft flights. Cloud production over Nauru was examined using remote sensing instruments. The diurnal cycles of surface meteorology and radiation are characterized at a point near the west (downwind) coast of Nauru. The spatial variation of surface meteorology and radiation are also examined using surface and aircraft measurements. During the day, the island surface layer is warmer than the marine surface layer and wind speed is lower than over the ocean. Surface heating forces the growth of a thermal internal boundary layer, within which a plume of cumulus clouds forms. Cloud production begins early in the morning over the ocean near the island’s lee shore; as heating intensifies during the day, cloud production moves upwind over Nauru. These clouds form a plume that may extend over 100 km downwind of Nauru. Aircraft observations showed that a plume of warm, dry air develops over the island that extends 15–20 km downwind before dissipating. Limited observations suggest that the cloud plume may be sustained farther downwind of Nauru by a pair of convective rolls. Suggestions for further investigation of the cloud plume are made.

Electrical Activity During the 2006 Mount St. Augustine Volcanic Eruptions

By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms.

A Pacific Moisture Conveyor Belt and Its Relationship to a Significant Precipitation Event in the Semiarid Southwestern United States

Abstract In this study the term moisture conveyor belt (MCB) is defined as an elongated band of enhanced poleward water vapor fluxes (WVFs) above the PBL that is rooted in the Tropics. This new terminology is illustrated through an exemplary detailed case study of an MCB over the northeastern Pacific during 9–13 November 2003 that provides the moisture for a significant precipitation event in the dry southwestern United States. The analysis of the involved moisture transports and dynamics comprises both Eulerian and Lagrangian approaches, and is based upon output from a simulation with the University of Wisconsin-Nonhydrostatic Modeling System, as well as analysis data, surface observations, and satellite images. The formation of the MCB is related to a quasi-stationary upper-level cutoff low (COL) resulting from a wave-breaking event over the North Pacific. A pronounced upper-tropospheric baroclinic zone and a strong, inertially unstable subtropical jet (STJ) are found to the east of the COL, where at later stages an elongated tropical cloud plume developed in association with a marked flare-up of ITCZ convection. Part of the extratropical air that subsides to the west of the COL becomes involved in this convection; another part feeds the so-called dry slot at the base of the COL. The actual MCB consists of midlevel trajectories that curve anticyclonically away from the moist tropical easterlies and cause a northeastward-directed WVF maximum at around 700 hPa over the subtropical northeast Pacific and a marked humidity gradient toward the subsided extratropical air. At late stages, frontogenetic circulations lead to WVF convergence involving air from the midlevel subtropical troposphere. At the surface, cyclogenesis and thermal contrasts are weak, and northeasterly trade winds prevail, which clearly distinguishes this MCB from a classical extratropical warm conveyor belt. Other important differences are the high elevation of the WVF maximum, as well as the quasi-horizontal track and origin above the PBL of most moist trajectories. Three precipitation regions with different influence factors can be distinguished. 1) Close to the COL center, moist tropical air is overrun by the dry slot, resulting in convective instability and extreme hail in the Los Angeles, California, area. 2) To the north and east, quasigeostrophic forcing and midlevel warm frontogenesis generate ascent, where the northern branch of the MCB circulates around the COL. 3) Along the anticyclonic shear side of the STJ, convection forms within potentially unstable MCB air benefiting from the inertial instability at the outflow level. It is suggested that this set of circumstances is quite similar to those that conspire to produce heavy precipitation events in subtropical West Africa.

Topographically Generated Cloud Plumes

Abstract Two topographically generated cirrus plume events have been examined through satellite observations and real-data simulations. On 30 October 2002, an approximately 70-km-wide cirrus plume, revealed by a high-resolution Moderate Resolution Imaging Spectroradiometer (MODIS) image and a series of Geostationary Operational Environmental Satellite (GOES) images, originated from the Sierra Nevada ridge and extended northeastward for more than 400 km. On 5 December 2000, an approximately 400-km-wide cloud plume originated from the Southern Rocky Mountain massif and extended eastward for more than 500 km, the development of which was captured by a series of GOES images. The real-data simulations of the two cirrus plume events successfully capture the presence of these plumes and show reasonable agreement with the MODIS and GOES images in terms of the timing, location, orientation, length, and altitude of these cloud plumes. The synoptic and mesoscale aspects of the plume events, and the dynamics and microphysics relevant to the plume formation, have been discussed. Two common ingredients relevant to the cirrus plume formation have been identified, namely, a relatively deep moist layer aloft with high relative humidity and low temperature (≤−40°C near the cloud top), and strong updrafts over high terrain and slow descent downstream in the upper troposphere associated with terrain-induced inertia–gravity waves. The rapid increase of the relative humidity associated with strong updrafts creates a high number concentration of small ice crystals through homogeneous nucleation. The overpopulated ice crystals decrease the relative humidity, which, in return, inhibits small crystals from growing into large crystals. The small crystals with slow terminal velocities (<0.2 m s−1) can be advected hundreds of kilometers before falling out of the moist layer.

Impact of Island-Induced Clouds on Surface Measurements: Analysis of the ARM Nauru Island Effect Study Data

Abstract An Atmospheric Radiation and Cloud Station (ARCS) was established on the island of Nauru by the Atmospheric Radiation Measurement (ARM) Program. Analysis of the Nauru99 field experiment data indicated that measurements at the ARCS were affected by a cloud plume that was induced by diurnal heating of the island. During the Nauru Island Effects Study, instrumentation was installed at a second site to develop criteria for identifying when the cloud plume occurs and to quantify its effect on ARCS measurements. The plume directional heading and frequency of occurrence are affected by the large-scale tropical circulation. During the present study, in which an El Niño was developing, Nauru was in a region of active convection, and easterly trade winds were not dominant; plumes were observed in 25% of satellite images, and only one-half of the observed plumes were downwind of the ARCS site. Surface wind direction, surface air temperature, and downwelling solar radiation at the two sites were used to identify periods when the cloud plume affected surface measurements. Differences in low-cloud frequency and surface radiation between plume-affected and non-plume-affected periods were examined. Existence of the cloud plume increased the average low-cloud frequency of occurrence from 20% to 35%, decreased the average downwelling shortwave radiation by 50–60 W m−2, and increased the average downwelling longwave radiation by 5–10 W m−2. Installing a suite of surface meteorological instruments and a global shortwave radiometer at a second site will allow for the long-term quantification of the cloud plume effect on the radiation field at the ARCS site.

THE MAP ROOM

OCTOBER 2003 AMERICAN METEOROLOGICAL SOCIETY | ake-effect and ocean-effect clouds and precipitation are well-documented mesoscale phenomena that can significantly impact the weather in coastal regions. The Chesapeake Bay is a large marine estuary that extends from Maryland to southeastern Virginia (Fig. 1), where the mouth opens to the Atlantic Ocean north of Hampton Roads (Newport News to Virginia Beach). Chesapeake Bay is approximately 240 km long and ranges from 15 km wide in Maryland to over 30 km wide near the mouth in southern Virginia. The complex coastline encompasses many smaller bays and expands the lateral coverage of water to over 65 km in the Virginia portion. Cloud and precipitation plumes can develop in the Chesapeake Bay, similar to the mesoscale phenomena observed in the Great Lakes and Atlantic coastal areas. These plumes can impact aviation and marine interests, enhance synoptic rainfall or snowfall, and sometimes produce waterspouts. The effects are very localized, yet can have significant impact on a population of over 1 million people, including a large segment of our nation’s military. Due to the narrow range of thermodynamic and kinematic conditions that support their development, bay plumes occur most frequently from the fall through spring. Plume formation is normally associated with postfrontal strong low-level cold temperature advection. Bay water temperatures are also climatologically warmer than air temperatures during this period. Air–sea temperature differences can support development of bay plumes that affect the Hampton THE MAP ROOM