GOES Satellite Imagery Research Articles

A 4D feature‐tracking algorithm: A multidimensional view of cyclone systems

An objective four‐dimensional (4D) algorithm developed to track extratropical relative vorticity anomaly 3D structure over time is introduced and validated. The STACKER algorithm, structured with the TRACKER single‐level tracking algorithm as source of the single‐level raw tracks, objectively combines tracks from various levels to determine the 3D structure of the cyclone (or anticyclone) events throughout their life cycle. STACKER works progressively, beginning with two initial levels and then adding additional levels to the stack in a bottom‐up and/or top‐down approach. This allows an iterative stacking approach, adding one level at a time, resulting in an optimized 4D determination of relative vorticity anomaly events.A two‐stage validation process is carried out with the ECMWF reanalysis ERA‐Interim dataset for the 2015 austral winter. First the overall tracking capability during an austral winter, taking into account a set of climate indicators and their impacts on Southern Hemisphere circulation, was compared to previous climatologies, in order to verify the density and distribution of the cyclone events detected by STACKER. Results show the cyclone density distribution is in very good agreement with previous climatologies, after taking into account potential differences due to climate variability and different tracking methodologies. The second stage focuses on three different long‐lived events over the Southern Hemisphere during the winter of 2015, spanning seven different pressure levels. Both GOES satellite imagery, infrared and water vapour channels, and ERA‐Interim cloud cover products are used in order to validate the tracks obtained as well as the algorithm's capability and reliability. The observed 3D cyclone structures and their time evolution are consistent with current understanding of cyclone system development. Thus, the two‐stage validation confirms that the algorithm is suitable to track multilevel events, and can follow and analyse their 3D life cycle and develop full 3D climatologies and climate variability studies.

Prototype of the Mexican spatial data infrastructure for climate raster models and satellite imagery (“VISTA-C”)

In the face of climatic uncertainty and its impacts on agriculture yields, there is a growing need for public institutions of subtropical countries to access as reliable as possible meteorological models and transmit a representation of their results in an effective way to stakeholders in agriculture. In many of these countries however, broad climatic regions and point-based statistics remain the core of these representations. The use of satellite imagery is largely limited to visual assessment, although it could serve as complementary data to meteorological raster models and the basis for spatially consistent quantitative impact assessments of meteorological events. In view of this situation in Mexico, a project developed by the Institute of Geography at UNAM university, and promoted by the National Institute of Geography and Statistics, consisted in the development of a climate monitoring system, which includes three main features: 1) a modular array storage system containing NOAA and GOES satellite imagery acquired though a receiving station (ERISA), 2) a climate modeling squeme based on successive error corrections of climate raster maps and associated models using the above mentioned imagery, and 3) an online, dynamic geovisualization of the results of the models. We discuss the implemented technologies and illustrate the VISTA-C prototype which has been released.

Very low frequency subionospheric remote sensing of thunderstorm‐driven acoustic waves in the lower ionosphere

AbstractWe present observations of narrowband subionospheric VLF transmitter signals on 20 March 2001, exhibiting coherent fluctuations of over 1 dB peak to peak. Spectral analysis shows that the fluctuations have periods of 1–4min and are largely coherent. The subionospheric propagation path of the signal from Puerto Rico to Colorado passes over two regions of convective and lightning activity, as observed by GOES satellite imagery and National Lightning Detection Network lightning data. We suggest that these fluctuations are evidence of acoustic waves launched by the convective activity below, observed in the 80–90 km altitude range to which nighttime VLF subionospheric remote sensing is sensitive. These observations show that VLF subionospheric remote sensing may provide a unique, 24h remote sensing technique for acoustic and gravity wave activity. We reproduce this event in simulations using a fluid model of gravity and acoustic wave propagation to calculate the ionospheric disturbance, followed by an electromagnetic propagation model to calculate the perturbation amplitude at the location of the VLF receiver. Simulation results show that a very large and coherent convective source is required to produce these amplitude perturbations.

The Role of GOES Satellite Imagery in Tracking Low-Level Moisture

Abstract This note provides examples of how geostationary satellite data can be applied to augment other data sources in tracking warm, moist air masses as they move northward from the Gulf of Mexico. These so-called returning air masses are often a key ingredient in bringing about severe weather outbreaks in the central and southeastern United States. The newer NOAA–GOES imagery provides high spatial and temporal resolution. Together, surface observations, upper-air soundings, and high-resolution satellite imagery provide a comprehensive picture of the returning moist air mass.

Applications of MODIS satellite data and products for monitoring air quality in the state of Texas

The Center for Space Research (CSR), in conjunction with the Monitoring Operations Division (MOD) of the Texas Commission on Environmental Quality (TCEQ), is evaluating the use of remotely sensed satellite data to assist in monitoring and predicting air quality in Texas. The challenges of meeting air quality standards established by the US Environmental Protection Agency (US EPA) are impacted by the transport of pollution into Texas that originates from outside our borders and are cumulative with those generated by local sources. In an attempt to quantify the concentrations of all pollution sources, MOD has installed ground-based monitoring stations in rural regions along the Texas geographic boundaries including the Gulf coast, as well as urban regions that are the predominant sources of domestic pollution. However, analysis of time-lapse GOES satellite imagery at MOD, clearly demonstrates the shortcomings of using only ground-based observations for monitoring air quality across Texas. These shortcomings include the vastness of State borders, that can only be monitored with a large number of ground-based sensors, and gradients in pollution concentration that depend upon the location of the point source, the meteorology governing its transport to Texas, and its diffusion across the region. With the launch of NASA's MODerate resolution Imaging Spectroradiometer (MODIS), the transport of aerosol-borne pollutants can now be monitored over land and ocean surfaces. Thus, CSR and MOD personnel have applied MODIS data to several classes of pollution that routinely impact Texas air quality. Results demonstrate MODIS data and products can detect and track the migration of pollutants. This paper presents one case study in which continental haze from the northeast moved into the region and subsequently required health advisories to be issued for 150 counties in Texas. It is concluded that MODIS provides the basis for developing advanced data products that will, when used in conjunction with ground-based observations, create a cost-effective and accurate pollution monitoring system for the entire state of Texas.

GOES imagery fills gaps in Montserrat volcanic cloud observations

GOES satellite imagery offers great potential to lessen the risk of volcanic ash clouds to aviation, and the situation at Montserrat in the Caribbean is providing the proof. Many transatlantic, commercial, and private aircraft use airspace around Montserrat, where the Soufriere Hills Volcano has been erupting since 1995.Worldwide over the last 15 years, more than 80 airplanes have reported encountering volcanic ash along flight paths. Encounters cannot be avoided because onboard radar cannot detect fine‐grained ash particles—those with a radius of 15 microns or less. In recent years volcanic cloud encounters are estimated to have caused hundreds of millions of dollars worth of damage and in a few cases have caused in‐flight engine failure [Casadevall et al., 1996].

Clustering, randomness, and regularity in cloud fields: 5. The nature of regular cumulus cloud fields

This study focuses on the nature of regularity in cumulus cloud fields at the spatial scales suggested by Weger et al. [1993]. We analyzed cumulus cloud fields from Landsat, advanced very high resolution radiometer, and GOES satellite imagery for regularity, using nearest‐neighbor cumulative distribution statistics. We found that the spatial scales over which regularity is observed vary from 20 km to 150 km in diameter. Clouds involved in regularity range in radius from about 300 m to 1.5 km. For the cases analyzed, we observed regularity in about 20% of the scenes, while randomness was the dominant spatial distribution for cumulus cloud fields; in addition, we frequently observed a tendency toward regularity. For regions in which we observed either regularity or randomness with a tendency toward regularity, small clouds were inhibited up to a distance of 3 cloud radii from the center of the large cloud. We also determined the size distributions of clouds, using a power law. For clouds larger than 1.5 km radius the exponent of the power law was correlated to the type of spatial distribution of the clouds. The exponent has largest values for regular spatial distributions, smallest values for clustered distributions, and in‐between values for random spatial distributions. Analysis of GOES scenes shows that the spatial distribution tends to be clustered in the early stages of the cloud field. During the mature phase it becomes either random, regular, or random with tendency toward regularity. During the later stages of cloud field development the spatial distribution once again becomes clustered.

The Influence of the Rocky Mountains on the 13–14 April 1986 Severe Weather Outbreak. Part II: Evolution of a Prefrontal Bore and Its Role in Triggering a Squall Line

Abstract In this paper, Part II of a series, the evolution of a prefrontal bore on the leeside of the Rockies and its subsequent propagation and initiation of convection farther downstream over eastern Colorado and western Nebraska are investigated. The observational evidence for this sequence of events was obtained from combined analyses of high-resolution GOES satellite imagery and Program for Regional Observing and Forecasting Services mesonetwork data over the Colorado region for the severe weather event that occurred during 13–14 April 1986. A 2D nonhydrostatic numerical model is used to further understand the initiation of the bore and its ability to propagate farther downstream and trigger convection. Analysis of satellite imagery and mesonet data indicated that an internal bore (ahead of a cold front), a moderate downslope windstorm, and a quasi-stationary hydraulic jump were generated within a few hours along the Iceslope as a Pacific cold front and its attendant upper-level jet streak advanced o...

Mesoscale Numerical Simulation of Cirrus Clouds—FIRE Case Study and Sensitivity Analysis

The 28 October 1986 First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) case was simulated using the Regional Atmospheric Modeling System developed at Colorado State University. This three-dimensional mesoscale model was applied in nonhydrostatic and nested-grid mode, using explicit, bulk microphysics and radiation. The simulation resulted in very good agreement between observed and model-predicted dynamic and cloud fields. Cloud height, thickness, areal extent, and microphysical composition were verified against GOES satellite imagery, lidar, and aircraft measurements taken during the FIRE cirrus intensive field observation. Cloud-top generation zones and layering were simulated. Sensitivity simulations were run to determine long- and shortwave radiative forcing. Also, a simulation was run with no condensate to examine cloud feedbacks on the environment. Longwave radiation appeared to be instrumental in developing weak convective-like activity, thereby increasing the cloud's optical depth.

A comparison of satellite winds and surface buoy winds in the northeast Pacific: Research note

Abstract Cloud‐motion winds measured from organized and disorganized cumulus cloud fields are compared with winds measured at collocated buoys in the northeast Pacific Ocean. Findings suggest that an automated tracking algorithm using GOES satellite imagery can measure cloud‐level winds at these latitudes. Comparisons with buoy wind measurements show that the influence of boundary‐layer stability should be included in estimates of surface winds from cloud‐motion data.

Operational Use of Profiler Data and Satellite Imagery to Evaluate the NMC Numerical Models in Predicting Heavy Snow

Abstract Near real-time wind profiler data from Stapleton International Airport at Denver, Colorado were used to confirm the existence of a midtropospheric closed low and vorticity maximum which were initially detected in satellite imagery over the High Plains of the United States. The initial development of the winter storm occurred between the conventional upper-air rawinsonde sites and differed, in several important aspects, from the guidance indicated by the three National Meteorological Center (NMC) operational numerical models: the nested grid (NGM), the limited-area fine-mesh (LFM), and the spectral in the aviation forecast run (AVN). Comparisons were made between hourly changes in the profiler winds, GOES satellite imagery and the location of heavy snow and the expected area of heavy snow derived by applying synoptic-climatological techniques to the three numerical models’ initial and predicted positions of the vorticity maximum. The NGM forecast trends appeared to relate best to the changes in sa...

An observational case study of a continental mesoscale vortex

An observational case study of a continental mesoscale vortex embedded in a polar air stream has been conducted, with emphasis on observed vortex features and their possible relationship to the polar-low phenomena and accompanying synoptic scale features at the 850 mb, 700 mb and 500 mb levels. The path of this 14–16 December 1983 event (determined from GOES satellite imagery) was over the relatively data-rich region of the midwestern United States, with the mesoscale vortex rotating cyclonically around and to the south of an occluded synoptic-scale surface low pressure system (and 500 mb low). This case study exhibited features common to the polar low with its convective cloud mass, although a distinct surface signature never developed. The mesoscale vortex formed and remained within a strong cyclonic shear region (4 times 10 -5 s -1 ) at the 850 mb level, but was supported by the evolution of a baroclinic pattern as well. Spatial and temporal cross-sections (both horizontal and vertical) revealed a weak low-level warm core capped by a strong cold dome, most pronounced at the 700 mb level and distinctly separate from the synoptic scale low in the surface map and 500 mb height field. This low static stability mesoscale system occurred entirely beneath the 500 mb level with cloud tops near 600 mb, and was associated with a weakly defined 600 km wave at the 700 mb level. The pure CISK model results for wavelength growth by Bratseth and the combined moist baroclinicity and CISK studies by Sardie and Warner correspond best to this continental event. It is suggested that both barotropic and baroclinic instability mechanisms (combined with CISK) can exist cooperatively in support of the development and maintenance of both continental and maritime polar low events. DOI: 10.1111/j.1600-0870.1989.tb00378.x

The Relationship between Satellite-Inferred Frontogenesis and Squall Line Formation

A study of three years of GOES satellite imagery has been conducted to determine whether synthesis of the imagery with surface diagnostic analyses may prove useful for predicting the precise location and time of formation of squall lines generated by a particular type of frontal circulation transverse to surface cold fronts. Existence of this circulation is inferred from the development of a thin Line of shallow Convection clouds (LC) along the front simultaneously with that of a mesoscale (<100 km wide) Clear Zone (CZ) immediately behind the front and at the leading edge of a large area of stratus clouds. The observations suggest that a thermally direct circulation transverse to the surface cold front generated the line convection and clear zone (in the upward and downward branches of the circulation, respectively) in all 15 cases which met the strict criteria for an LC/CZ. Squall lines were observed to form from the LC in 10 of the 15 cases examined, and nearly always within 90 min following the time when the CZ reached its maximum width. In addition, initial cumulonimbus development always occurred within 100 km of the diagnosed frontogenesis center at the LC. Therefore, this study suggests that both the timing and location of such squall lines should be predictable with very high accuracy. It is also shown that thermodynamic instability was insufficient for the formation of deep convection in the five non-thunderstorm cases. Our results also strongly support the hypothesis of Koch (1984) that this mesoscale circulation was generated by differential sensible heating acting in conjunction with geostrophic deformation effects. The contrast of cloudy skies behind the front (prior to CZ formation) with nearly clear skies ahead of the front is largely responsible for creation of the differential heating pattern. This suggests that forecasters should watch for such cloud patterns near cold fronts. Synoptic climatological conditions favoring the occurrence of this relatively rare phenomenon are also identified. The LC/CZ appears during the afternoon almost solely over the Great Plains states during spring and autumn. The line convection was found in all but one case to be parallel to, and either along or on the cyclonic side of, a prefrontal 850 mb jet. Although the LC/CZ is usually found on the anticyclonic side of upper-level jet streaks, it does not seem to prefer any particular jet quadrant. Diagnosis of the Sawyer-Eliassen equation for one case suggested that the mesoscale circulation was linked to a thermally direct circulation cell associated with the upper-level frontal zone. The information provided in this paper should be valuable to the operational forecaster concerned with having some guidance about specific mesoscale trigger mechanisms for squall lines. This phenomenon can be isolated with conventional surface and satellite data in real time to provide accurate and timely forecasts of the formation of squall line activity.

The Impact of Mesoscale Convective Systems on Regional Visibility and Oxidant Distributions during Persistent Elevated Pollution Episodes

It is generally accepted that atmospheric pollutants can be transported over distances described as synoptic in scale. However, the redistribution and removal of the various pollutant species may be significantly influenced, often in a highly episodic way, by phenomena which are inherently mesoscale in nature. Detailed mesoanalyses over a 31 hour period reveal the dramatic influence of several types of mesoscale convective systems on regional ozone and visibility. In the impacted air mass, afternoon ozone was significantly depleted (20–40 ppb vs 100–120 ppb in the polluted regional air mass). Visibilities, which prior to the wind shift/rain had typically been 4–13 km rose in a matter of a few hours to 27–80 km at many locations. This convective aerosol removal event covered Virginia, northern North Carolina, Delmarva, and more than 500 km into the Atlantic, as clearly evidenced by GOES satellite imagery. Assuming a relationship between visibility and surface aerosol mass concentrations, it is speculated that approximately 30 × 106 kg of sulfate were removed from the planetary boundary layer (PBL). The removal was not due solely to wet deposition. Rather, consideration of thunderstorm dynamics suggests that perhaps two-thirds of the removal from the PBL could have been due to convective displacement into the free atmosphere, perhaps to altitudes as high as the tropopause.

Ability of a Regional-Scale Model to Predict the Genesis of Intense Mesoscale Convective Systems

The mesoscale part of a two-part evaluation of 30 forecasts by a mesoscale numerical weather prediction model (MASS 2.0) is presented. Unfiltered fields are combined into convective predictor fields, the loci of which are then related at two-hour intervals to the loci of strong mesoscale convective systems identifiable in national radar summary plots and GOES satellite imagery. Examples of model 'forecasts' of intense convective storm clusters, a severe squall line triggered along a dryline, orographically induced hailstorms, and sea breeze thunderstorms are provided.

NEW APPROACH TO ESTIMATING SOLAR RADIATION FROM SATELLITE IMAGERY∗

A significantly less expensive but comparatively accurate means of estimating solar radiation from satellite imagery is demonstrated. Opaque cloud cover is visually extracted from nondigitized, photographic forms of GOES satellite imagery and solar radiation is estimated using this information as input into a relatively simple solar model. Daily root mean square, mean absolute and mean bias errors were 13.2, 8.6 and 1.1 percent, respectively. Maps of the spatial distribution of solar radiation for Arizona are included.