An examination of the humidity correction by Vaisala RS80-A radiosondes for experiments and measurements at an inland Antarctic station

The present paper examines the correction of humidity measurements by the Vaisala RS80-A radiosonde using data obtained at Dome Fuji Station, inland Antarctica. The correction method is based upon a procedure developed by L.M. Miloshevich et al.(J. Atmos. Oceanic Technol., 18, 135, 2001). In the present study, experiments in a snow cave below ground, where a state of ice saturation is assumed, show that Miloshevich\u27s coefficient is appropriate for temperatures warmer than -45 °C because the corrected humidity reflects the state of ice saturation. Below these temperatures a correction coefficient is needed. At -55 °C , for example, a factor of 1.2 is needed. An examination using surface humidity data obtained from a routine aerological observation concluded that the correction coefficient is larger than Miloshevich\u27s at temperatures colder than -50 °C , so that the multiplication factor(0.185968×exp((-0.0339)×T); T=temperature) is needed to apply Miloshevich\u27s coefficient. After the correction is performed, the relative humidity with respect to ice becomes 150 on average in the lower temperature range. Perpetual falling of ice crystals indicates at least an occurrence of ice saturation; this condition of high relative humidity is supported by downwelling of a large amount of water vapor in an intense temperature inversion layer and an extremely small number of ice nuclei, suggested by in-situ data. An improved correction applied to a vertical profile in the temperature inversion layer reveals that supersaturation with respect to ice appears at all levels. In the lowest layer, humidity increases with decreasing height, although observed data show steep dryness with decreasing height. This is considered a measurement error

Temperature dependence of brightness temperature difference of AVHRR infrared split window channels in the Antarctic

One method to identify clouds from NOAA/AVHRR data is to use the difference in brightness temperature of infrared split window channels in the 10μm region. Under the low temperature over the Antarctic continent in winter, it is necessary to detect a slight difference in brightness temperature. In this paper, we investigate the temperature dependence of the brightness temperature difference of channel 4 (10.8μm) brightness temperature (T4), and channel 5 (12 μm) brightness temperature (T5) (T4-T5) of a cloud free scene. T4-T5 is about 0°C at low temperature around -80°C, and gradually increases up to a high of 1°C at high temperature around 0°C. The rates of increase in T4-T5 were almost constant for T4 lower than -40°C. For T4 higher than -30°C, T4-T5 remains almost unchanged. For T4 between -40°C and -30°C, T4-T5 increases rapidly. In order to explain this temperature dependence, the contribution of water vapor and surface emissivity to the difference in brightness temperature was calculated from in situ data using the radiation code MODTRAN. The result is shown below. About the contribution of water vapor, at T4 lower than -25°C, T4-T5 was nearly zero. From about -25°C to 0°C of T4, T4-T5 increases up to near 0.6°C. On the other hand, when the surface emissivity difference between CH4 and CH5 was set to 0.01, T4-T5 increased in all temperature ranges. The rate of increase was almost constant. In the temperature range lower than -40°C, T4-T5 conformed to T4-T5 of satellite data

L-Glutamate production by lysozyme-sensitive Corynebacterium glutamicum ltsA mutant strains

BACKGROUND: A non-pathogenic species of coryneform bacteria, Corynebacterium glutamicum, was originally isolated as an L-glutamate producing bacterium and is now used for fermentative production of various amino acids. A mutation in the C. glutamicum ltsA gene caused susceptibility to lysozyme, temperature-sensitive growth, and L-glutamate production. RESULTS: The characteristics of eight lysozyme-sensitive mutants which had been isolated after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis were examined. Complementation analysis with the cloned wild-type ltsA gene and DNA sequencing of the ItsA region revealed that four mutants had a mutation in the ltsA gene. Among them, two mutants showed temperature-sensitive growth and overproduced L-glutamate at higher temperatures, as well as the previously reported ltsA mutant. Other two showed temperature-resistant growth: one missense mutant produced L-glutamate to some extent but the other nonsense mutant did not. These two mutants remained temperature-resistant in spite of introduction of ltsA::kan mutation that causes temperature-sensitive growth in the wild-type background. CONCLUSIONS: These results indicate that a defect caused by the ltsA mutations is responsible for temperature-sensitive growth and L-glutamate overproduction by C. glutamicum. The two temperature-resistant mutants seem to carry suppressor mutations that rendered cells temperature-resistance and abolished L-glutamate overproduction

Seasonal variation of air transport in the Antarctic and Atmospheric Circulation in 1997

To better understand how present and past climates at Syowa Station, Antarctica relate to climate elsewhere, we analyzed the tropospheric air transport to Syowa Station for the year 1997 using a dataset from the European Centre for Medium Range Weather Forecasts(ECMWF). The five-day trajectories of the air parcels were estimated and analyzed. In the middle troposphere in winter, air parcels were usually from the lower troposphere over the Atlantic. However, in January, most of the air parcels came from latitudes higher than 60°S . The trajectories had little vertical motion and were associated with a low pressure system that forms along the coastal region of Antarctica only in summer. In the lower troposphere, trajectories could be classified as originating in one of three regions: the Southern Ocean, the continental interior, and the east coast. In contrast to the middle troposphere, air parcels from the Southern Ocean had the lowest frequency, irrespective of the time of year. This is partially due to a low pressure system that blocks air parcels from outside the continent. Most trajectories are affected by the drainage flow. An amplified quasi-stationary planetary wave for September to November and a blocking circulation in June make trajectories pass over Antarctica

Meteorological characteristics of Antarctic inland station, Dome Fuji (scientific paper)

Surface meteorological observations were carried out during 1995 and 1997, and extended atmospheric science observations were carried out in 1997 as a sub program of "Atmospheric Circulation and Material Cycle in the Antarctic (1997-2001)" at Dome Fuji Station (77°19\u27S, 39°42\u27E) where deep ice core drilling was done. The annual mean surface air temperature was -54.4°C with the lowest record of -79.7°C. The mean wind speed was 5.8 m/s with no clear prevailing wind direction. From aerological soundings, temperature profiles are described; they are characterized by a strong surface inversion such as 25°C, on a normal winter day. Abrupt warming occurred several times a year; the largest showed 40 degree temperature increase within two days between 17 and 19 July 1997. The event was associated with the intrusion of an anticyclone, "a blocking high", and many drastic phenomena such as large accumulation of snow followed this event