The Air Force Global Weather Central operational boundary-layer model

A limited-area seven-layer physical-numerical model for the lower tropospheric region (surface - 1600m) is described. The grid interval, approximately 190km, is half that of the standard numerical weather-prediction grid used in the hemispheric free atmospheric operational model at the Air Force Global Weather Central (AFGWC). This model is an integral part of the complete AFGWC meso-scale (sub-synoptic) numerical analysis and prediction system and is used to provide greater horizontal and vertical resolution in both numerical analyses and forecasts.Important features of this boundary-layer model include: a completely automated objective analysis of input data; the transport of heat and moisture by three-dimensional wind flow; latent heat exchange in water substance phase changes; and eddy fluxes of heat and water vapor.Input data are conventional synoptic surface and upper air reports. Other operational AFGWC prediction models provide input in the form of horizontal wind components at the upper boundary and an estimate of cloudiness above the boundary layer. Forecasts for the lower boundary and surface layer are empirically derived. Despite some approximations which broadly simplify the real planetary boundary-layer processes, operational use for highly weather-sensitive Air Weather Service support indicates that the model is capable of producing accurate detailed forecasts for periods of up to 24h.A modified version of this paper was presented at the IUGG-IAMAP-AMS conference on Planetary Boundary Layers at Boulder, Colo., 18–21 March, 1970, and at the 5th annual Congress of the Canadian Meteorological Society, at Macdonald College, 12–14 May, 1971.     

Stratospheric in situ measurements of H2SO4 and HSO3 vapors during a volcanically active period

In situ measurements of stratospheric H₂SO₄ and HSO₃vapors using passive chemical ionization mass spectrometry were made in October 1982 after the eruption of volcano El Chichon. Data were obtained between about 20 and 41 km showing [H₂SO₄ + HSO₃] sum concentrations between about 10⁴ and 2 × 10⁵ cm^?3 below 29 km and a steep rise above this altitude. Maximum [H₂SO₄ + HSO₃] values of about 3 × 10⁶ cm^?3 are reached above 35 km.Partial [HSO₃] concentrations increase above 34 km reaching about $\text{4 × 10}{}^5\text{cm}{}^{\mathrm{?3}}$ around 40 km. From the measurements it is concluded that H₂SO₄ and probably HSO₃photolysis have an important influence above 34 km leading to the observed increase of [HSO₃] and a depletion of H₂SO₄vapor.It also seems that the data support the view of heterogeneous HSO₃ removal. If correct, this would imply that stratospheric aerosols are formed primarily from HSO₃ rather than H₂SO₄vapor.     

NOAA AR 8210: EVOLUTION AND FLARES FROM MULTIBAND DIAGNOSTICS

NOAA 8210 has been a region showing a remarkable level of activity well before solar maximum. Dominated by a large, rapidly rotating spot, it produced several intense flares during its disk passage at the end of April–beginning of May 1998. We examine the development of AR 8210 in H and white light (WL) and study the evolution of its complex magnetic topology. While the other principal flares are briefly reviewed, the great X1.1/3B flare of 2 May, which was observed at Kanzelhöhe Solar Observatory during a SOHO/UVCS ground support campaign, is studied in detail. This event has been documented in full-disk H and Na-D intensitygrams, Dopplergrams, and magnetograms, with a time cadence of one minute each. The flare was associated with a CME and produced significant geomagnetic effects. Furthermore, we point out the perspectives for our planned Flare Monitoring and Alerting System, since the two new instruments (Magneto-Optical Filter and Digital H camera), which made their first operational run with the campaign, are crucial components for this program.     

Dating alluvial deposits with optically stimulated luminescence, AMS C and cosmogenic techniques, western Transverse Ranges, California, USA

In an effort to better understand chronology of alluvial episodes in Cuyama Valley in the western Transverse Ranges of California, USA, we employed optically stimulated luminescence, radiocarbon and cosmogenic radionuclide surface exposure dating methods. Twenty-one optical dates ranging from 0.01 to 27 ka were obtained from exposures of late-Holocene axial-fluvial deposits, Pleistocene–Holocene alluvial-fan deposits, and axial-fluvial sands interbedded within a late Pleistocene alluvial fan. These were cross-checked with 37 AMS radiocarbon dates from charcoal and wood from within a and five ¹⁰Be surface exposure dates from boulders on alluvial-fan surfaces. The OSL results show generally good stratigraphic consistency, logical comparison with the radiocarbon and cosmogenic data, and appear to be the best method for accurate dating within deposits of this nature because suitable material is fairly easy to find in these environments. The radiocarbon data contained numerous “detrital ages”, but well-bedded lenses of apparently in situ or minimally transported charcoal provide reliable age estimates for the associated alluvium. Radiocarbon dating of detrital charcoal in the older alluvial fan deposits was problematic. Our cosmogenic surface-exposure dating was consistent stratigraphically and with our other data, but we were unable to determine its accuracy due to the limited number of samples and the possibility of inherited radionuclides and post-depositional erosion. In light of our results, we suggest that OSL dating using the latest analytical techniques combined with rigorous methods for estimation of paleodase is reliable and of increasing utility in otherwise difficult-to-date coarse alluvial environments in the southwestern United States and elsewhere.     

基于高光谱遥感数据提取森林结构参数的研究

以位于三峡库区的龙门河森林自然保护区为研究区,综合利用线性光谱混合模型和几何光学模型,基于高光谱遥感数据提取森林结构参数是本文研究的重点。在研究区地面调查数据的基础上,通过高光谱数据和混合光谱分解法,获得反演几何光学模型所需的四分量参数,根据背景光照分量与森林植被冠层各参数间的关系,反演得到森林冠层郁闭度及平均冠幅的定量分布图,并利用37个野外实测样本进行结果验证。     

Holocene alluvial stratigraphy in the upper Susquehanna River Basin, New York

Two alluvial terraces and the present flood plain were studied at two locations along the Susquehanna and Unadilla Rivers in south-central New York state. They have formed since deglaciation and incision of the stream channels into the valley train deposits. The higher terrace has noncumulative soil profiles with well-developed color B horizons predominantly of silt loam and very fine sandy loam. The terrace is weathered to a degree similar to nearby glacial outwash terraces that have caps of similarly textured sediments. Incision that produced the terrace occurred before 9705 ± 130 yr B.P. The lower terrace is characterized by relatively thick, vertical-accretion deposits of silt loam that contain sequences of thin, buried A, color B, and C horizons. They were formed between about 3240 ± 110 (¹⁴C data of soil humin) and 235 ± 80 yr B.P. Deposits above the 235 ± 80 yr B.P. stratum are unweathered. The soil stratigraphy and ¹⁴C dates of soil humin from buried A horizons are surprisingly well correlated between sites. Most sediments of the present flood plain have been deposited since 1120 ± 80 yr B.P. Incipient A horizons and oxidation of inherited organic matter in the subsoil are the only evidence of pedogenesis in the flood-plain deposits that are older than 275 ± 80 yr B.P. The most recent flood-plain fill deposited since then is unaltered. These youngest sediments of the flood plain along with the youngest veneer of vertical-accretion deposits on the lowest terrace are associated with an increased rate of deposition largely attributable to clearing of the forests by settlers, beginning in the late 1700s. Comparison of the alluvial stratigraphy with the radiocarbon-dated pollen stratigraphy of southwestern New York (Miller 1973) reveals some apparent time correlations between alluvial events and vegetation changes. This gives reason to speculate that climatic change or forest catastrophes such as disease or drought are causes of some of the alluvial events.     

Cosmic-ray-produced36Cl and53Mn in Allan Hills-77 meteorites

Cosmic-ray-produced⁵³Mn (t_1/2 = 3.7 × 10⁶years) has been determined by neutron activation in nine Allan Hills-77 meteorites. Additionally,³⁶Cl (_1/2 = 3.0 × 10⁵years) has been measured in seven of these objects using tandem accelerator mass spectrometry. These results, along with¹⁴C (t_1/2 = 5740years) and²⁶Al (7.2 × 10⁵ years) concentrations determined elsewhere, yield terrestrial ages ranging from 0.1 × 10⁵ to 7 × 10⁵ years. Weathering was not found to result in⁵³Mn loss.     

Hallimond tube flotation of scheelite and calcite with amines

Hallimond tube flotation experiments have been carried out on the two calcium minerals scheelite and calcite using dodecylammonium chloride as collector. The main variables studied were the calcium ion concentration and the pH.In the case of scheelite, addition of calcium chloride markedly lowered the flotation recovery. Recovery was also lowered when the pH was reduced below about 10. Since it is known that the zeta potential of scheelite is almost independent of pH this confirms that co-adsorption of un-ionized amine is necessary for good flotation. Other un-ionized long-chain molecules can replace the amine; thus it was shown that excellent flotation can be obtained event at about pH 7 by adding dodecanol together with dodecylammonium chloride. With the completely ionic trimethyldodecylammonium chloride recoveries were poor and were independent of pH.In the case of calcite, calcium chloride had no immediate effect on flotation recovery, but at low collector concentrations marked depression occurred after many hours standing in the presence of calcium ions. The effect of pH on flotation of calcite was anomalous and there appear to be two pH regions in which recoveries are high.The results are discussed and attention is drawn to the need for more thorough studies of the calcium carbonate/water interface.