Stereoscopic observations from meteorological satellites

The capability of making stereoscopic observations of clouds from meteorological satellites is a new basic analysis tool with a broad spectrum of applications. Stereoscopic observations from satellites were first made using the early vidicon tube weather satellites (e.g., Ondrejka and Conover [1]). However, the only high quality meteorological stereoscopy from low orbit has been done from Apollo and Skylab, (e.g., Shenk $\text{et al.}$ [2] and Black [3], [4]). Stereoscopy from geosynchronous satellites was proposed by Shenk [5] and Bristor and Pichel [6] in 1974 which allowed Minzner $\text{et al.}$ [7] to demonstrate the first quantitative cloud height analysis. In 1978 Bryson [8] and desJardins [9] independently developed digital processing techniques to remap stereo images which made possible precision height measurement and spectacular display of stereograms (Hasler $\text{et al.}$ [10], and Hasler [11]). In 1980 the Japanese Geosynchronous Satellite (GMS) and the U.S. GOES-West satellite were synchronized to obtain stereo over the central Pacific as described by Fujita and Dodge [12] and in this paper. Recently the authors have remapped images from a Low Earth Orbiter (LEO) to the coordinate system of a Geosynchronous Earth Orbiter (GEO) and obtained stereoscopic cloud height measurements which promise to have quality comparable to previous all GEO stereo. It has also been determined that the north-south imaging scan rate of some GEOs can be slowed or reversed. Therefore the feasibility of obtaining stereoscopic observations world wide from combinations of operational GEO and LEO satellites has been demonstrated.Stereoscopy from satellites has many advantages over infrared techniques for the observation of cloud structure because it depends only on basic geometric relationships. Digital remapping of GEO and LEO satellite images is imperative for precision stereo height measurement and high quality displays because of the curvature of the earth and the large angular separation of the two satellites. A general solution for accurate height computation depends on precise navigation of the two satellites. Validation of the geosynchronous satellite stereo using high altitude mountain lakes and vertically pointing aircraft lidar leads to a height accuracy estimate of ± 500 m for typical clouds which have been studied. Applications of the satellite stereo include: 1) cloud top and base height measurements, 2) cloud-wind height assignment, 3) vertical motion estimates for convective clouds (Mack $\text{et al.}$ [13], [14]), 4) temperature vs. height measurements when stereo is used together with infrared observations and 5) cloud emissivity measurements when stereo, infrared and temperature sounding are used together (see Szejwach $\text{et al.}$ [15]).When true satellite stereo image pairs are not available, synthetic stereo may be generated. The combination of multispectral satellite data using computer produced stereo image pairs is a dramatic example of synthetic stereoscopic display. The classic case uses the combination of infrared and visible data as first demonstrated by Pichel $\text{et al.}$ [16]. Hasler $\text{et at.}$ [17], Mosher and Young [18] and Lorenz [19], have expanded this concept to display many channels of data from various radiometers as well as real and simulated data fields.A future system of stereoscopic satellites would be comprised of both low orbiters (as suggested by Lorenz and Schmidt [20], [19]) and a global system of geosynchronous satellites. The low earth orbiters would provide stereo coverage day and night and include the poles. An optimum global system of stereoscopic geosynchronous satellites would require international standarization of scan rate and direction, and scan times (synchronization) and resolution of at least 1 km in all imaging channels. A stereoscopic satellite system as suggested here would make an extremely important contribution to the understanding and prediction of the atmosphere.     

Applications of stereoscopic height computations from dual geosynchronous satellite data/joint NASA-Japan stereo project

Stereoscopic heights of the top of an Oklahoma thunderstorm were computed, finding that high cloud tops are not always characterized by very cold IR temperature. The identical method was also applied to the computation of stereo heights based on GOES West and GMS stereo pairs obtained under the NASA-JAPAN cooperative program. It was found that stereo techniques are extremely useful in understanding the structure of thunderstorms in the United States, as well as that of hurricanes over the South Pacific.     

Tropical storm structure revealed by stereoscopic photographs from Skylab

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 of the storm. This type of supercell convection in tropical storms has recently been correlated with subsequent rapid deepening. The stereo analysis revealed that a circular cloud feature over the storm center was a dome which protruded 3–4 km above the undisturbed cirrus clouds. The center of the dome was capped by smaller scale convective turrets which protruded another 1–2 km above the dome. The existence of shear induced waves in the cloud tops is shown with wave amplitude ranging from 150–300 m and wave lengths ranging from 2–4 km. The existence of gravity waves at the cloud tops is also shown with wave amplitudes of 500–600 m and wavelengths of 10–12 km.     

Stereoscopic imaging from polar orbit and synthetic stereo imaging

The photogrammetric determination of cloud top heights from stereoscopic satellite images seems to be a very good solution to this hitherto unresolved problem. Whereas in the U.S.A., stereoscopic imaging is done by use of geosynchronous weather satellites, in Europe such a system cannot be used because there is only one geosynchronous satellite (METEOSAT). An alternative could be a Stero Line Scanner (SLS) operating on a polar orbiter.SLS would scan twice, forward and backward, producing in this way two image strips for steroscopic viewing and photogrammetric measurements from pole to pole. Because of the cloud motion between the two scans, a SLS needs additional independent height information for reference points, e.g. from a Laser Ranger (LAR). The advantage of this method is that cloud motion, and therefore wind, can also be determined for these reference points. Another solution is a system of two SLS satellites flying one after the other and scanning the same area simultaneously. This allows cloud motion determination across the whole image. The use of infrared channels also allows night operation and provides additional data such as improved seas surface temperatures.The DFVLR is currently studying these problems. Synthetic stereoscopic imaging is being used in a forerunner programm to the SLS project and also for simulation in SLS studies.     

The performance of the GMS (HIMAWARI)

The pserformance of the GMS (HIMAWARI) during the three years since it was launched in the middle of 1977 has been described with emphasis in the measurements of meteorological parameters such as sea surface temperature, cloud vectors and center position of typhoons alluding to their accuracy.     

Ionospheric storm due to solar Coronal mass ejection in September 2017 over the Brazilian and African longitudes

Coronal mass ejection (CME) occurs when there is an abrupt release of a large amount of solar plasma, and this cloud of plasma released by the Sun has an intrinsic magnetic field. In addition, CMEs often follow solar flares (SF). The CME cloud travels outward from the Sun to the interplanetary medium and eventually hits the Earth’s system. One of the most significant aspects of space weather is the ionospheric response due to SF or CME. The direction of the interplanetary magnetic field, solar wind speed, and the number of particles are relevant parameters of the CME when it hits the Earth’s system. A geomagnetic storm is most geo-efficient when the plasma cloud has an interplanetary magnetic field southward and it is accompanied by an increase in the solar wind speed and particle number density. We investigated the ionospheric response (F-region) in the Brazilian and African sectors during a geomagnetic storm event on September 07–10, 2017, using magnetometer and GPS-TEC networks data. Positive ionospheric disturbances are observed in the VTEC during the disturbed period (September 07–08, 2017) over the Brazilian and African sectors. Also, two latitudinal chains of GPS-TEC stations from the equatorial region to low latitudes in the East and West Brazilian sectors and another chain in the East African sector are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA). We noted that the EIA was disturbed in the American and African sectors during the main phase of the geomagnetic storm. Also, the Brazilian sector was more disturbed than the African sector.     

气象卫星在暴雨和强对流天气系统监测和短时天气预报中的应用

简要地介绍了气象卫星,特别是地球静止气象卫星图象资料在强对流风暴(雷雨大风和冰雹)和暴雨两大类灾害性天气系统的监测和短时预报中的作用、地位和应用情况;同时,还扼要地给出了利用卫星资料研究这两类天气系统所取得的部分成果;最后讨论了利用气象卫星监测降水的重要性及其现状。     

Stereoscopic observations of hurricanes and tornadic thunderstorms from geosynchronous satellites

Results are presented to show the application of GOES stereoscopy to the study of hurricanes and tornadic thunderstorms. Stereoscopic cloud top height contour maps were constructed to observe the structural evolution of two hurricanes: Frederic, 12 September 1979 and Allen, 8 August 1980 and a tornadic thunderstorm complex over Oklahoma on 2–3 May 1979. Stereoscopic height contours of Hurricane Allen show a very intense and symmetric storm with a circular shaped Central Dense Overcast (CDO) with an average height of 16.5 km. Height contours of Hurricane Frederic show a preferred region for convection with an explosive exhaust tower reaching a maximum height of 17.8 km. A technique for estimating tropical cyclone intensity using GOES stereoscopic height and infrared temperature information is also presented. Utilizing short interval (3-min) GOES stereoscopic data from 2 May 1979 and 9 May 1979 (SESAME days), cloud top ascent rates were measured and used in determining the intensity of growing convective cells. Results show vertical motions ranging from 4.4 m s^?1 for a moderate storm to 7.7 m s^?1 for an intense storm. These results compare well in magnitude with growth rates determined from simultaneous GOES infrared observations and previous estimates of visual and radar echo top growth rates of other thunderstorms.     

Response of the lower atmosphere to intense geomagnetic storms

In this short paper we examine the possible connection between atmospheric parameters measured at low and middle altitudes and geomagnetic storms occurred in 2000 and 2003. For that, from a chain of stations located near the meridian 60°W we compare the storm time values of temperature and wind speed with their standard deviation 2σ obtained from quiet time values. We observed statistically significant variations at several altitudes during the storm recovery phase and after it, both in neutral wind speed and temperature. The results obtained suggest that atmospheric parameters could be affected by geomagnetic storms.     

Can an impulsive variation of the solar wind plasma pressure trigger a plasma bubble? A case study based on CSES,Swarm and THEMIS data

During the August 25, 2018 geomagnetic storm, the new borne CSES-01 satellite and the Swarm A satellite detected a really large equatorial plasma bubble (EPB) in the post-midnight sector over western Africa. We investigated the features of this deep ionospheric plasma depletion using data from the Langmuir probes on-board CSES-01 and Swarm A satellites, and data from the high-precision magnetometer and the electric field detector instruments on-board CSES-01. Using also plasma and magnetic field data from THEMIS-E satellite we found that, during the passage of the magnetic cloud that drove the geomagnetic storm, an impulsive variation lasting about ten minutes characterized the solar wind (SW) pressure. The analysis of the delay time, between the occurrence of such impulsive variation and the detection of the plasma bubble, suggests a possible link between the SW pressure impulsive variation as identified by THEMIS-E and the generation of the EPB as detected by CSES-01 and Swarm A. We put forward the hypothesis that the SW pressure impulsive variation might have triggered an eastward prompt penetrating electric field that propagated from high to equatorial latitudes, overlapping in the nightside region to the zonal westward electric field, causing either a reduction or an inversion, at the base of the EPB triggering.     

The compatability of cloud tracked winds from the United States,European, and Japanese geostationary satellites

Overlap of coverage of the five geostationary satellites has allowed an intercomparison of the FGGE cloud tracked winds. No attempt was made during FGGE to standardize the cloud tracking techniques. In spite of this potential for differences between data sets, the compatability of the various cloud wind data sets was generally quite good. The vector magnitude differences between nearly co-located vectors showed similar cumulative frequency statistics for all data producers. A study of systematic biases which could affect a global wind analysis of any given synoptic period showed that image alignment errors caused less than 2 m s^?1 bias for all data producers except the NESS high level winds which had an average bias of slightly greater than 3 m s^?1. This appears to be caused by the manual alignment of images in the movie loops. Height bias studies showed the Japanese winds to be higher than other data producers by as much as 100 mb for both the high and low levels winds. Height biases appear to be caused by the differences in cloud wind height assignment procedures.     

Mid-latitude thermospheric wind changes during the St. Patrick’s Day storm of 2015 observed by two Fabry-Perot interferometers in China

In this work, we utilize thermospheric wind observations by the Fabry-Perot interferometers (FPI) from the Kelan (KL) station (38.7°N, 111.6°E, Magnetic Latitude: 28.9°N) and the Xinglong (XL) station (40.2°N, 117.4°E, Magnetic Latitude: 30.5°N) in central China during the St. Patrick’s Day storm (from Mar. 17 to Mar. 19) of 2015 to analyze thermospheric wind disturbances and compare observations with the Horizontal Wind Model 2007 (HWM07). The results reveal that the wind measurements at KL show very similar trends to those at XL. Large enhancements are seen in both the westward and equatorward winds after the severe geomagnetic storm occurred. The westward wind speed increased to a peak value of 75?m/s and the equatorward wind enhanced to a peak value of over 100?m/s. There also exist obvious poleward disturbances in the meridional winds during Mar. 17 to Mar. 19. According to the comparison with HWM07, there exist evident wind speed and temporal differences between FPI-winds and the model outputs in this severe geomagnetic storm. The discrepancies between the observations and HWM07 imply that the empirical model should be used carefully in wind disturbance forecast during large geomagnetic storms and more investigations between measurements and numerical models are necessary in future studies.     

International comparison of satellite winds — An update

Winds obtained from geostationary satellites are compared with each other and with rawinsondes. These comparisons serve as a periodic quality check of satellite cloud motions (or winds) set up by the CGMS (Coordination for Geostationary Meteorological Satellites). Differences are taken between colocated cloud motions observed by adjacent satellites in areas of overlapping coverage (Type 1) and between colocated rawinsondes and cloud motions within the field of view of each individual satellite (Type 2).Among colocated satellite winds (Type 1) RMS vector difference of high clouds rarely exceed 10 mps and of low clouds, 6 mps. But, among colocated cloud and balloon vectors (Type 2), RMS vector differences are large. At high levels, differences range from 12 to 40 mps for GMS (Geostationary Meteorological Satellite) winds and from 10 to 18 mps for GOES (Geostationary Operational Environmental Satellite) winds. The greater disagreement of satellite winds with rawinsonde winds than with each other is attributed in large part to error in the assignment of cloud height especially in the presence of strong vertical shear and to a lesser extent on time differences between cloud and balloon measurements. Both Type 1 and 2 comparisons suffer from separations in distance (tolerated for purposes of establishing “colocation”) between cloud and balloon in the presence of strong horizontal shear. The discrepancy existing between GMS and GOES differences with rawinsondes is attributed primarily to differing techniques of height assignment.At low levels satellite winds departed from balloon winds by a RMS vector difference of about 6 to 9 mps which approached or exceeded the mean wind speed itself. This problem is attributed chiefly to the uncertainty of wind levels controlling the motion of the various low cloud types.     

Wind-field analysis on the basis of METEOSAT images

A method for the determination of cloud motion vectors is proposed by calculating from METEOSAT images the displacement of characteristic formations in the brightness field. The claculations are made for a sector of the Atlantic Ocean (ψ = 48°?38°N, λ = 24°?12°W). The adaptability of the Soebel operator for such calculations is also shown. The calculated wind vectors are in a good agreement with wind data at 850 mb surface.     

新型倒装式旋转电场仪

介绍了一种全新设计的倒装式旋转电场仪，通过测量大气电场强度和极性的变化，对局部地区潜在的雷暴活动及静电电击事故发出报警，可用于气象、航天、航空、石油、电力、工矿及森林防火、露天体育场地等易起静电和易受静电及雷电危害的场所安全监测的预警仪器．     

Remote sensing of clouds

The extraction of information on cloud cover from present-day multispectral satellite images poses a challenge to the remote sensing specialist. When approached one pixel at a time, the derived cloud cover parameters are inherently nonunique. More information is needed than is available in the radiances from each channel of an isolated pixel. The required additional information can be obtained for each scene, however, by analyzing the distribution of pixels in the multi-dimensional space of channel radiances. The cluster patterns in this space yield statistical information that points to the most likely solution for that scene. The geostationary and polar orbiting meteorological satellites all have, at a minimum, a solar reflection channel in the visible spectrum and a thermal infrared channel in the 8–12 micron window. With the information from the cluster patterns and application of the equations of radiative transfer, the measurements in those channels will yield cloud cover fraction, optical thickness, and cloud-top temperature for an assumed microphysical model of the cloud layer. Additional channels, such as the 3.7 micron channel on the AVHRR of the polar orbiting meteorological satellites, will will yield information on the microphysical model—e.g., distinguishing small liquid liquid droplets (typical of low level clouds) from large ice particles (typical of cirrus and the tops of cumulonimbus). New channels to be included in future satellite missions will provide information on cloud height, independent of temperature, and on a particle size and thermodynamic phase, independently of each other. A proposed STS mission using lidar will pave the way for the use of active sensors that will provide more precise information on cloud height and probe the structure of thin cirrus and the top layer of of the thicker cloud.     

The role of space techniques in FGGE

The space-based sub-system of the composite observing system, operated during the Operational Year of the Global Weather Experiment, played an indispensable role in the acquisition of data and in transmitting data from surface-based and airborne observational platforms to data-processing centres. The sub-system comprised both geostationary and near-polar orbiting meteorological satellites and special efforts were undertaken to keep the performance of the system as close as possible to that which had been anticipated during the planning stage of the Experiment.Five geostationary satellites were spaced at approximately uniform intervals around the equator. They were used primarily to derive wind vectors by measuring the displacement of clouds. The satellites also provided communication support for the Aircraft to Satellite Data Relay system, by which flight level meteorological data were automatically transmitted to ground receiving stations.Three polar orbiting satellites provided data simultaneously during the whole Operational Year. Vertical temperature soundings, clear-radiance data, sea-surface temperature and wind speed data, and total atmospheric water vapour data were produced for inclusion in the research data set of the Experiment. Two of these satellites /TIROS-N and NOAA-6/ carried a new data collection and platform location system, a basic component of the Tropical Constant Level Balloon System and the Drifting Buoy System of FGGE.     

The possibilities of polar meteorology,environmental remote sensing,communications and space weather applications from Artificial Lagrange Orbit

The ability to observe meteorological events in the polar regions of the Earth from satellite celebrated an anniversary, with the launch of TIROS-I in a pseudo-polar orbit on 1 April 1960. Yet, after 50 years, polar orbiting satellites are still the best view of the polar regions of the Earth. The luxuries of geostationary satellite orbit including rapid scan operations, feature tracking, and atmospheric motion vectors (or cloud drift winds), are enjoyed only by the middle and tropical latitudes or perhaps only cover the deep polar regions in the case of satellite derived winds from polar orbit. The prospect of a solar sailing satellite system in an Artificial Lagrange Orbit (ALO, also known as “pole sitters”) offers the opportunity for polar environmental remote sensing, communications, forecasting and space weather monitoring. While there are other orbital possibilities to achieve this goal, an ALO satellite system offers one of the best analogs to the geostationary satellite system for routine polar latitude observations.     

Time dependent charging of layer clouds in the global electric circuit

There is much observational data consistent with the hypothesis that the ionosphere-earth current density (J_z) in the global electric circuit, which is modulated by both solar activity and thunderstorm activity, affects atmospheric dynamics and cloud cover. One candidate mechanism involves J_z causing the accumulation of space charge on droplets and aerosol particles, that affects the rate of scavenging of the latter, notably those of Cloud Condensation Nuclei (CCN) and Ice Forming Nuclei (IFN) (  and ). Space charge is the difference, per unit volume, between total positive and total negative electrical charge that is on droplets, aerosol particles (including the CCN and IFN) and air ions. The cumulative effects of the scavenging in stratiform clouds and aerosol layers in an air mass over the lifetime of the aerosol particles of 1–10 days affects the concentration and size distribution of the CCN, so that in subsequent episodes of cloud formation (including deep convective clouds) there can be effects on droplet size distribution, coagulation, precipitation processes, and even storm dynamics.     

Comparison of global MHD simulation results with actual storm and substorm events

Global MHD models hold the promise of providing a physics-based understanding of magnetospheric structure and dynamics. As such models have become more sophisticated, and computing power has increased, it is now possible to model actual events using solar wind data as a boundary condition. In this paper we present some results MHD simulations of actual storm and substorm events. We will demonstrate that not only can the simulations reproduce details of events, they also are reproducing fundamental aspects of energy coupling between the solar wind and the magnetosphere in such a manner that we can distinguish storms and substorms.