Atlantic tropical cyclone statistics
Climatology of tropical storms in North Atlantic Caribbean and Gulf of Mexico
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Climatology of tropical storms in North Atlantic Caribbean and Gulf of Mexico
Statistical model for simulating radar echoes from tropical precipitation for ocean surface region using Nimbus 3 satellite infrared data
Atlantic tropical cyclone strike probabilities for selected stations during September
Latent heat convective transport from lower to tropical upper troposphere, noting periodic energy fluctuations from time lapse synchronous satellite cloud photographs
Study of time series of areal cloud coverage over the central Pacific to determine the large-scale variations of tropical disturbance activity for a four-month period in 1967. The persistent and fluctuating components are found to be more prevalent in regions of high and low mean cloudiness, respectively, with major longitudinal variations in activity most evident in the Southern Hemisphere. Normalized power spectra show that the transient activity occurring in the equatorial zone is dominated by shorter periods of about four days, while longer periods are dominant away from the equator. Coherency magnitudes and phases between different locations indicate that propagating cloud systems are most identifiable at lower frequencies in the Southern Hemisphere, and at somewhat higher frequencies in the Northern Hemisphere. Activity with periods in excess of five days consists largely of both westward and eastward propagation on the planetary wave scale. The shorter periods appear to consist of both synoptic-scale and planetary-scale modes, with westward propagation dominant near the equator.
The bulk properties of tropical cloud clusters, as the vertical mass flux, the excess temperature, and moisture and the liquid water content of the clouds, are determined from a combination of the observed large-scale heat and moisture budgets over an area covering the cloud cluster, and a model of a cumulus ensemble which exchanges mass, heat, vapor and liquid water with the environment through entrainment and detrainment. The method also provides an understanding of how the environmental air is heated and moistened by the cumulus convection. An estimate of the average cloud cluster properties and the heat and moisture balance of the environment, obtained from 1956 Marshall Islands data, is presented.
A selected group of 1973 North Pacific Ocean tropical cyclones was studied by using data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR), the Temperature-Humidity Infrared Radiometer (THIR), NOAA-2 and USAF DMSP imageries. From the unique combination of infrared, visible, and microwave data, it was possible during various stages of storm development to differentiate between dense cirrus outflow and rain areas, to identify centers of circulation and areas of low-level moisture, and by the use of a theoretical model to estimate semi-quantitatively areas of light, moderate, and heavy rainfall rates.
Far-ultraviolet imagery of the earth in the wavelength ranges from 1050 to 1600 A and from 1250 to 1600 A was obtained from the lunar surface during the Apollo 16 mission on Apr. 21, 1972. The images have an angular resolution of about 2 arcmin (230-km linear resolution) and have been quantitatively analyzed to obtain absolute intensities and spatial distributions of the polar auroras (both wavelength ranges), the day and night airglow, and tropical airglow belts (1250-A to 1600-A wavelength range). The observations are consistent with previous results obtained from the OGO-4 spacecraft, but they have also provided details on the spatial distributions of the various emissions over an entire hemisphere at a single time. A general night airglow, at least in the Northern Hemisphere, is indicated.
The bulk diagnostic method of Yanai et al. (1973) and a simplified version of the spectral diagnostic method of Nitta (1975) are used for a more quantitative evaluation of the response of various types of cumuliform clouds to large-scale processes, using the same data set in the Marshall Islands area for a 100-day period in 1956. The dependence of the cloud mass flux distribution on radiative cooling, large-scale vertical motion, and evaporation from the sea is examined. It is shown that typical radiative cooling rates in the tropics tend to produce a bimodal distribution of mass spectrum exhibiting deep and shallow clouds. The bimodal distribution is further enhanced when the large-scale vertical motion is upward, and a nearly unimodal distribution of shallow clouds prevails when the relative cooling is compensated by the heating due to the large-scale subsidence. Both deep and shallow clouds are modulated by large-scale disturbances. The primary role of surface evaporation is to maintain the moisture flux at the cloud base.
Low-level, ATS-3 satellite wind estimates are compared with values of wind direction and speed interpolated from analyses based on research aircraft observations of a synoptic tropical wave of moderate intensity on 26 July 1969 during BOMEX. The data were stratified according to whether a satellite estimate was positioned in one of three regions; namely, east or west of the wave trough or north of the disturbance center. When cloud and analysis vector magnitude deviations were computed, regional differences became apparent. These differences are attributed to the physical behavior of the cloud targets tracked under the influence of the surrounding large-scale environment.
Aerial photographic and laser profilometer data of waves generated by tropical storm Amy are presented. The data mission consisted primarily of two legs, one in the direction of the wind waves, and the second along the direction of swell propagation, using Jennette's Pier at Nags Head, North Carolina, as a focal point. At flight time, Amy's center was 512 nmi from shore and had maximum winds of 60 knots. The storm's history is presented, along with a satellite photograph, showing the extent of the storm on the day of the flight. Flight ground tracks are presented along with sample aerial photographs of the wave conditions showing approximate wavelength and direction. Sample wave energy spectra are presented both from the laser profilometer onboard the aircraft, and from the Corps of Engineers Research Center (CERC) shore gauge at Nags Head, North Carolina.
The backscatter ultraviolet instrument on the Atmosphere Explorer-E satellite has acquired a large body of stratospheric and total ozone data in the tropical region. The latitudinal variation of the ozone mixing ratio on constant pressure surfaces shows the transition from chemical domination to transport control between 5 and 10 mb. Spectral analysis of the longitudinal O3 structure reveals large wavenumber 1 and 2 patterns, although considerable activity in wavenumbers 5 through 7 sometimes appears. Longitudinal structure increases with decreasing pressure between 30 and 5 mb. The spatial variability near 5 mb must reflect similar structure in the odd nitrogen distribution which provides the major loss mechanism for ozone at this level.
Analysis of data obtained by the backscatter ultraviolet (BUV) experiment on the Atmosphere Explorer E satellite has provided equatorial ozone mixing ratio profiles for equinox and solstice conditions. The combination of these results with a pure oxygen chemical model yields the rate of odd oxygen loss due to the sum of the odd hydrogen, nitrogen, and chlorine cycles. Use of recent mid-latitude stratospheric measurements of HO(x), NO(x), and ClO(x) with the BUV data provides an independent calculation of the catalytic loss. Below 45 km the agreement between the two sets of loss rates is satisfactory. At higher altitudes the odd hydrogen cycle provides far more O(x) loss than can be tolerated by the BUV measurements if the photodissociation of O2 is the only source and has the currently accepted magnitude. The results suggest either a tropical HO(x) concentration smaller than is now believed or the presence of a very large source of odd oxygen in the upper stratosphere and lower mesosphere.
A regression technique was developed to forecast 24 hour changes of the maximum winds for weak (maximum winds less than or equal to 65 Kt) and strong (maximum winds greater than 65 Kt) tropical cyclones by utilizing satellite measured equivalent blackbody temperatures around the storm alone and together with the changes in maximum winds during the preceding 24 hours and the current maximum winds. Independent testing of these regression equations shows that the mean errors made by the equations are lower than the errors in forecasts made by the peristence techniques.
Data from the Nimbus-5 electrically scanning microwave radiometer (ESMR) were used to calculate total storm latent heat release (LHR) and other precipitation parameters for over 100 satellite observations of Pacific Ocean tropical cyclones. The data are useful in determining the rainfall characteristics of these storms and appear to be potentially useful in monitoring them.
An advanced Man-Interactive image and data processing system (AOIPS) was developed to extract basic meteorological parameters from satellite data and to perform further analyses. The errors in the satellite derived cloud wind fields for tropical cyclones are investigated. The propagation of these errors through the AOIPS system and their effects on the analysis of horizontal divergence and relative vorticity are evaluated.
Warm temperature anomalies over tropical cyclones are sensed by the 55.45 GHz channel of the Nimbus 6 Scanning Microwave Spectrometer. Radial brightness temperature gradients are related to radial surface pressure gradients through the hydrostatic and radiative transfer equations. Surface wind speeds outside of the radius of maximum wind are calculated from the pressure gradients and compared with observations.
Passive microwave observations were made in tropical storm Cora at 19.35 and 94GHz. These observations suggest that 94GHz is appropriate for mapping the extent of rain over either land or ocean backgrounds and that some rainfall intensity measurement is also possible.