IR Brightness Research Articles

An Examination of the Diurnal Cycle in Oceanic Tropical Rainfall Using Satellite and In Situ Data

Abstract Diurnal variations in tropical cold cloudiness are examined for the period 1986–90 for each 2.5° latitude–longitude area in the global Tropics. The fractional coverage of cold cloudiness, as determined from various IR brightness temperature thresholds, has been used as a proxy for tropical convective precipitation, as direct observations of rainfall are unavailable for much of the earth, especially over the oceans. Variations in fractional coverage of cold cloud for three different temperature thresholds are examined: 235.225, and 215 K. The results of this study indicate that cold cloud is most frequently observed over land between 1800 and 2100 local time and is independent of the temperature threshold used. Over the tropical oceans, however, the time of maximum occurrence of cold cloud varies substantially with the temperature threshold employed. Coldest cloud-top temperatures (< 215 K) are found to occur much earlier in the day than warmer cloud tops and peak between 0300 and 0600 local time,...

IR Observations of the Symbiotic Nova HM Sagittae

The infrared photometry of the symbiotic nova HM Sge, with a Mira variable as a cool component, shows that since 1983 its mean IR brightness began to decrease from the previous post-outburst level (Figure 1). In 1988 the mean J magnitude was already about 1 mag fainter than it had been until 1983.An analysis of the photometric observations shows that the decrease in the mean IR light level of HM Sge may be understood in the framework of the commonly accepted model of this binary stellar system (Taranova and Yudin 1983), if we suggest that the Mira variable and the inner parts of its circumstellar envelope (RMira envolope~ 3×l014 cm; τdust ≲ 1 at 1.25 µm until 1983) were gradually obscured by the dust originated between them and the observer.

Infrared reflectance spectra of Na 2S with contaminant Na 2CO 3: Effects of adsorbed H 2O and CO 2 and relation to studies of Io

A previously published IR reflectance spectrum of Na 2S, a candidate surface component on Jupiter's satellite Io, showed a weak but distinct band at approximately 4.04 μm that was interpreted as due to chemisorbed H 2S or SO 2. New spectra have been obtained on Na 2S powder showing that this 4-μm band is not due to H 2S or SO 2, but rather Na 2CO 3, a contaminant present in the original material. The carbonate is spectrally masked by the presence of contaminant adsorbed H 2O. Thermal drying of the sample diminishes the strength of the water bands, revealing the carbonate bands which become very strong due to reaction of the Na 2S with adsorbed atmospheric H 2O and CO 2 in the spectrometer sample chamber while heated by the hot IR source. Because of the extreme hygroscopic nature of Na 2S, a reflectance spectrum of pure Na 2S is not yet available. But the apparent high IR brightness of Na 2S and the spectral neutrality in the range 1–5 μm suggest that it could be a component on Io's surface.

Infrared radiances over the Tibetan plateau as measured by INSAT -IA VHRR In an active monsoon situation

INSAT-1A VHRR data have been used for a typical active monsoon situation over India which prevailed on 12/13 August 1982, to map the1emperature pattern over the Tibetan plateau region.. Gray shade and IR brightness values are analysed over the plateau and surrounding areas spatial and diurnal variations in the extent of the warm area and cloudiness are discussed. The plateau region is shown to be warmer than the surrounding which lends support to earlier theoretical and simulation studies.

Infrared radiation from compact X-ray sources

Observations of the X-ray binaries 4U 0115+634 and A 0535+262 performed in 1981 – 1982 revealed significant IR variabilities of these sources. 4U 0115+634 was observed twice, in the state close to X-ray activity, and in the state of low activity, thus changing from K = 7 m.75 to K > 9 m. A 0535+262 shows the temporal variations ranged from tens minutes to some days. The regular variations of IR brightness are suspected with teh period close to 104 s that corresponds to the period of axial rotation of neutron star in A 0535+262. The results obtained present arguments in favour of hypothesis that IR radiation is generated near the accreting neutron star and is possibly of maser nature.

Thunderstorm Top Structure Observed by Aircraft Overflights with an Infrared Radiometer

Thunderstorm top structure is examined with high spatial resolution radiometric data (visible and infrared) from aircraft overflights together with other storm views, including geosynchronous satellite observations. Results show that overshooting cumuliform towers appear as distinct cold areas in the high resolution, 11-micron IR aircraft images, but that the geosynchronous satellite observations significantly overestimate the thunderstorm-top IR brightness temperature, T(B), due to field of view effects. Profiles of cloud top height and T(B) across overshooting features indicate an adiabatic cloud surface lapse rate. However, one-dimensional cloud model results indicate that when comparing thunderstorm top temperature and height at different times or different storms, a temperature-to-height conversion of about 7 K/km is appropriate. Examination of mature storm evolution indicates that, during periods when the updraft is relatively intense, the satellite IR 'cold point' is aligned with the low-level radar reflectivity maximum, but during periods of updraft weakening and lowering cloud top heights, the satellite T(B) minimum occurs downwind with cirrus anvil debris. The growth period of a relatively weak cumulonimbus cluster is also examined with aircraft and satellite data.

Present state of the study of 160-minutes solar oscillation

Global oscillation of the Sun with a period of 160 rain were first discovered in 1974 and since observed in Crimea during the last 6 years; they were confirmed, in 1976–1979, by Doppler measurements at Stanford (Scherrer et al., 1980) and quite recently by observations of Fossat and Grec at the south geographic pole. The average amplitude of the oscillation is about 0.5 m s-1. The phase shows remarkable stability at the period 160.010 min and good agreement between different sites on the Earth; therefore, this oscillation should now be recognized as definitely of solar origin. It is probably accompanied by synchronous fluctuations in the IR brightness and radio-emission of the Sun, and exhibits a dependence of the amplitude on the phase of solar rotation (with a peak of power at 27.2 days).

Titan's atmosphere: temperature and dynamics

In the lower atmosphere of Titan IR brightness temperatures exhibit meridional contrast ≲3 K. Seasonal variations are absent because of the large radiative time constant. In the upper stratosphere meridional contrasts are ∼20 K, consistent with 100 m s−1 cyclostrophic zonal winds, and the radiative time constant is short, implying a large seasonal variation in the temperature and wind field. The absence of longitudinal thermal structure implies that zonally symmetric flows effect the meridional transport of heat. A simple model yields meridional velocities ∼0.04 cm s−1 and vertical eddy viscosities ∼103 cm2 s−1 in the lower troposphere, and meridional velocities ∼5 cm s−1 in the upper stratosphere.

An attempt for objective analysis of TIROS-N images

An attempt for digital processing of analog images taken in the infrared channel (10.5–11.5 μm) from TIROS-N is presented. The data digitized to 8-bits are normalized by using SR Data Manipulator. The investigated period is November 3–4, 1979. The geographic rectification moves the data into a polar stereographic map. To estimate the cloud heights empirical relationships are applied. The following characteristics of the cloud field are produced: the cloud amount, the dominant cloud-type, the daily variation of IR brightness temperature and the cloud texture. The results are visualized on a colour display.

IR brightness and eclipse cooling of Saturn's rings

Equatorial scans of Saturn at 20 µm wavelength, obtained with the Mayall 4-m telescope in 1978–79, show a continuing decrease in the specific brightness of the A and B rings as the ring plane projection approaches an edge-on apparition. The decreased brightness of the previously dominant B ring reveals more clearly a large (∼30%) difference in brightness between the east and west ansa portions of the C ring, in contrast to a barely discernible difference for the other ring ansae. The amount of eclipse cooling is compatible with a C ring particle size of ∼1 cm. We propose here that the B ring brightness variation could partially result from a decrease of absorbed insolation by a modest amount of visible scattering.

Selection of capillary discharge mode for IR brightness standard

Selection of capillary discharge mode for IR brightness standard

Radio Observations of IR/OH/H2O Stars

A small percentage of infrared stars, selected on the basis of their IR brightness at 2.2 µm and their redness (I–K colour index), show 18 cm OH emission, and some exhibit 1.35 cm H2O emission; further investigations identify some of these objects as M-type supergiants and the remainder as M-type giant long-period variable stars.For the strongest 1612 MHz OH emitters, long-baseline interferometry shows that the emission arises from a large number of small-diameter features distributed over a much larger, approximately elliptical region corresponding to a circumstellar cloud. Models for the geometry of the emitting regions are discussed.The OH characteristics with respect to the ratios of line intensities for different transitions and the velocity structure are distinctive, not being found in other types of OH source; consequently a large number of new OH emitters can be recognized as probably IR/OH objects despite the absence of IR or optical data; the precise classification of these sources is considered together with their relevance in understanding the identified sources.