Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images

An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 × 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence ±60° in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one‐pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle‐energy protons (low‐energy or high‐energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non‐unique relation between the proton‐associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45–49, 145–154, 297–335, and 390–440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

塔里木盆地中的大气环流及昆仑山北坡的黄土堆积

通过分析塔克拉玛干沙漠风积地貌形态所揭示的风向及盆地边缘25个气象站40 a的盛行风,我们恢复了盆地中沙尘暴形成时的风场。对大气环流分析表明,在暖季（春、夏）由于地面对大气感热加热作用强烈,形成了浅薄的热低压。当冷空气入侵时,在和田—于田—民丰一带形成强大的辐合上升区,使这个地区成为中国沙尘暴发生频率最高的地区,其扬起的粉尘沉降在昆仑山北坡而形成黄土堆积。由于冷空气入侵的强度不同,粉尘的扬升高度也不同,昆仑山北坡黄土厚度表明平均扬升高度在海拔2 900~3 400 m左右,最强的沙尘暴可将粉尘扬升到5 500 m的西风急流区。     

Case studies of spectral atmospheric transmittance in the ultraviolet and visible regions in Athens, Greece: I. Total transmittance

This work accounts for an investigation about the diurnal variation of total spectral transmittance of solar irradiance under dominant wind conditions as case studies. Such a work is carried out in Athens for the first time. The spectral transmittance values estimated were derived using ground-based spectral measurements of beam irradiance in the range 310–575 nm (UV and VIS). The data were recorded by a system consisting of an automatic solar tracker and a spectrometer. All data were recorded under clear-sky conditions in the city center of Athens and the spectral total atmospheric transmittance was estimated towards zenith to avoid optical mass effects. The comparison reveals that the total atmospheric transmittance is higher under the influence of strong Etesian compared to sea-breeze conditions. The influence of low-pressure systems also plays a depollution role in the basin. Various features of diurnal variation are discussed with respect to emission sources, topographic peculiarities and wind pattern.     

Parameterisation of surface radiation flux at an Antarctic site

During the Antarctic summer 1994/95 the values of downward and upward flux densities of both solar and terrestrial radiation were recorded at 1200 m for a period of 1 month on the Reeves Nevè Glacier (lat 74°39′S, long 161°35′E), near the Italian base of Terra Nova Bay. The relations proposed by Swinbank [Swinbank, W.C., 1963. Long-wave radiation from clear skies. Q. J. R. Meteorol. Soc. 89, 339–348], Idso and Jackson [Idso, S.B., Jackson, R.D., 1969. Thermal radiation from the atmosphere. J. Geophys. Res. 74, 5397–5403] and Deacon [Deacon, E.L., 1970. The derivation of Swinbank's long-wave radiation formula. Q. J. R. Meteorol. Soc. 96, 313–319] associating the long-wave atmospheric radiation flux only to the air temperature at screen level were tested in extreme Antarctic climatological condition. A relation between the long-wave radiation flux and both screen air temperature and cloud cover fraction in accordance to the height of the cloud base was defined using the Kasten and Czeplak relationship that relates the solar radiation flux and the cloud cover index. The study of the incoming short-wave radiation flux from the clear sky and that reflected by the surrounding snow cover allowed for highlighting the role of surface geometry on the albedo measurements.     

Potential Atmospheric Transport Pathways for Mercury Measured in the Canadian High Arctic

Large-scale transport pathways for atmospheric gaseous mercury emitted from surrounding source regions to reach the Alert sampling site located at the Northwest Territories of Canada between August 1992 and August 1993 were investigated. The 12-month atmospheric mercury data set comprises blank-corrected total gaseous mercury (TGM) concentrations collected on gold-coated sand traps during one-week long sampling intervals. For TGM concentrations above the 12-month mean TGM level, the analysis reveals regions in Eastern Europe (close to East Germany and Poland), areas on Northeastern America in Canada (Northwest Territories), and central Siberia of the former U.S.S.R. Identification of the physical locations of the emission sources was limited by the temporal resolution of weekly averaged data; however, major atmospheric pathways of mercury transport to the Arctic were successfully resolved. The objective of this note is to demonstrate that the potential source contribution function could be applied to resolve the sources and recover transport pathways of atmospheric mercury over a large scale.     

Numerical simulation of the marine boundary layer characteristics over the Bay of Bengal as revealed by BOBMEX-98 Pilot experiment

An attempt has been made to study the marine boundary layer characteristics over Bay of Bengal using BOBMEX (Bay of Bengal and Monsoon Experiment) pilot experiment data sets, which was conducted between 23rd October and 12th November 1998 on board ORV Sagar Kanya. A one-dimensional multilevel atmospheric boundary layer with TKE-ε closure scheme is employed to study the marine boundary layer characteristics. In this study two synoptic situations are chosen: one represents an active convection case and the other a suppressed convection. In the present article the marine boundary layer characteristics such as temporal evolution of turbulent kinetic energy, height of the boundary layer and the airsea exchange processes such as sensible and latent heat fluxes, drag coefficient for momentum are simulated during both active and suppressed convection. Marine boundary layer height is estimated from the vertical profiles of potential temperature using the stability criterion. The model simulations are compared with the available observations.     

青藏高原及其邻近地区旬感热通量基本气候特征

利用１９７９～１９９５年美国ＮＣＥＰ再分析资料中逐旬感热通量,对高原及其邻近地区旬感热通量季节变化、年际变化特征及冬、夏季感热通量旬异常的年际变化和季节变化进行了分析。结果表明：青藏高原感热通量有明显的季节变化,可分为科季型（１０月下旬～３月上旬）和夏季型（３月中旬～１０月中旬）,感热通量季节变化的明显区在高原北侧的荒原沙漠和南部珠峰一带,高原感热异常多发生在３～１５旬和２６～３６旬。冬季感热通量     

南极近地层大气的热量逆梯度输送现象

根据南极中山站观测结果 ,分析了南极地区近地层热量逆梯度输送的现象。结果表明南极地区在近地层逆温较明显时 ,常会出现热量逆梯度输送的现象 ;同时也探讨了近地层在稳定层结条件下 ,热量逆梯度输送通量的多尺度计算方法。计算结果表明 ,逆梯度输送的感热通量主要是由浮力湍涡的穿越能力决定的 ,而经典的梯度输送公式在该场合下无法使用。     

THE INTERBASIN TRANSPORT OF ATMOSPHERIC MOISTURE EVALUATED FROM NCEP/NCAR REANALYSIS DATA*

With the objective of providing a relatively accurate and complete diagram,the global scale interbasin transport of atmospheric moisture on the basis of the NCEP/NCAR reanalysis data for the period 1980 to 1994 is evaluated.The results show that the net zonal vapor flux for the Pacific,the Atlantic and the Indian Oceans is 0.25 Sv,-0.68 Sv and-0.29 Sv respectively.The marking differences in the zonal moisture budget among individual basins are speculated as the reason that dominates the differences in the salinity between the Pacific and the Atlantic Oceans.Though current evaluation on the net zonal moisture flux for the Atlantic basin is generally in qualitative agreement with the previous estimate,quantitative discrepancy is found to exist.According to current statistics,the tropical easterlies carry water vapor of 0.43 Sv from the Atlantic basin across Central America into the Pacific,and the northern westerliesal low water vapor of 0.25 Sv to escape from the Pacific.Quantitative analyses also reveal that the seasonal variation of net zonal vapor flux for the Pacific and the Indian Oceans is stronger than that for the Atlantic,which may be favorable for the maintenance of high salinity feature of the Atlantic Ocean.     

虚拟合作实验室-利用Internet开展大气科学国际合作研究的可行之路

试图提出一个由中美双方大气科学家参与的虚拟合作实验室的解决方案,实验室包括虚拟资料／信息系统、虚拟模拟系统、虚拟应用分析系统、虚拟培训学校、虚拟图书馆、虚拟可视化实验室和虚拟出版系统等。