Journal of the Meteorological Society of Japan. Ser. II
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Volume 73 , Issue 6
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  • Jong-Jin Baik, Masaaki Takahashi
    Volume 73 (1995) Issue 6 Pages 975-991
    Released: September 15, 2009
    JOURNALS FREE ACCESS
    To examine the sensitivity of the simulated large-scale structures to the Betts-Miller and the Arakawa-Schubert cumulus parameterizations, a series of 6-month integrations are performed using the CCSR/NIES atmospheric general circulation model with a horizontal triangular resolution of 21 and 20 vertical levels. The model results are time-averaged for the last three months, that is, June-July-August mean. Comparisons between the simulations using the Betts-Miller scheme and the Arakawa-Schubert scheme indicate that although the simulated large-scale structures are generally similar to each other, there are some noticeable differences. These include the temperatures in the middle and upper troposphere at mid-latitudes in the northern hemisphere, the location of the maximum convective heating in the tropical deep connective region, the convective heating/cooling in the boundary layer, the precipitation distribution pattern over the tropical western Pacific and the vertical profile of the vertical turbulent heat transport. Sensitivity experiments with different adjustment parameters in the Betts-Miller scheme show that the precipitation distribution pattern over the tropical western Pacific is very sensitive to the adjustment time scale and stability weight as well as the saturation pressure departure. It is also shown that the partition between the convective precipitation and the large-scale precipitation is most sensitive to the saturation pressure departure.
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  • N. Mannoji
    Volume 73 (1995) Issue 6 Pages 993-1009
    Released: September 15, 2009
    JOURNALS FREE ACCESS
    An explicit cloud predicting scheme is developed for the Florida State University Global Spectral Model (FSU-GSM). Both cloud water and cloud cover are prognostic variables in the scheme, but they are not advected in the current version. Cloud liquid water and cloud ice are distinguished by a prescribed function of temperature. Source terms are considered for convective cloud as well as stratiform cloud. The predicted cloud water content and cloud cover are provided to the radiation scheme.
    The model produces reasonable amounts of cloud cover and cloud water. Clouds originating from convection are important for cloud cover and cloud water except for the polar region. In the tropics, clouds originating from convection account for approximately half of the total cloud cover, and the majority of the high cloud coverage. They also produce half of the cloud water in the mid-latitudes, and are an essential source of the cloud water in the tropics.
    The outgoing longwave radiation in the tropics is improved by the explicit scheme, because the scheme includes the clouds originating from the convection. High clouds from convection are essential in the tropics, and have a large influence on the outgoing longwave radiation.
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  • Masaaki Takahashi, Toshiro Kumakura
    Volume 73 (1995) Issue 6 Pages 1011-1027
    Released: September 15, 2009
    JOURNALS FREE ACCESS
    Equatorial waves in a three-dimensional sector (1/5) model with moist convective adjustment are examined. The model is derived from a preliminary version of the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) general circulation model. The model produces a QBO-like oscillation in the equatorial upper stratosphere (Takahashi and Shiobara, 1995).
    There is a strong signal in the zonal wavenumber s=1 (global zonal wavenumber 5, since the model is a 1/5 sector), meridional mode number n=1 having a period of 2.5 days, corresponding to a westward-propagating equatorial gravity wave. The wave produces the dominant easterly phase of the QBO-like oscillation. The signal is also clearly seen in the precipitation. The eastward-propagating waves which produce the westerlies in the QBO-like oscillation are rather complicated. The signals are difficult to identify with equatorial waves, for example the Kelvin wave or n=1 equatorial gravity wave. The wave structures are like an ensemble of random gravity waves. These gravity waves produce the QBO-like oscillation in the sector model.
    A lower horizontal resolution experiment, using the T21 global model, is also performed to compare equatorial wave behavior. Kelvin and Rossby-gravity waves are simulated in the T21 general circulation model. Simulated gravity waves are, however, weak and as a result, the T21 model does not produce a QBO-like oscillation, but rather a steady state of easterlies in the equatorial upper stratosphere with westerlies in the middle stratosphere.
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  • Mitsuo Mizuma
    Volume 73 (1995) Issue 6 Pages 1029-1040
    Released: September 15, 2009
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    The general aspects of land and sea breezes in the Osaka Bay area and its environment are revealed from an analysis of the wind data obtained by the AMeDAS. The study area consists of a complex land-sea configuration and a complex topography which includes plains, hilly terrain, and mountainous regions. The land and sea breezes are classified into five types according to the behavior of the sea breeze at several locations in the study area.
    The most frequently occurring type is characterized in the following. Along the southern coast of Osaka Bay, the sea breeze from Osaka Bay changes with time into that from the Kii Channel. At the same time, along the coast of the Seto Inland Sea the sea breeze contains a predominant easterly component. For this type, several interesting features are further elucidated: (1) the simultaneous onset of the coastal sea breeze and the valley or upslope wind in the mountainous region is clearly seen, especially in the eastern Chugoku area, (2) the meeting of the southerly sea breeze from the Seto Inland Sea and the northerly breeze from the Sea of Japan occurs around the region of the mountain ridges in eastern Chugoku, (3) the alternation of converging sea breezes from surrounding seas forms a uniform southerly sea breeze from the Kii Channel at Awaji Island, (4) the southerly sea breeze continues until the late afternoon in the coastal area of the Kii Channel and Osaka Bay.
    Other types are discussed and compared with the above type for the mature stage of the sea breeze. The relationships between the occurrence of the land and sea breeze and general meteorological conditions are also analyzed.
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  • Yukitomo Tsutsumi, Yukio Makino
    Volume 73 (1995) Issue 6 Pages 1041-1058
    Released: September 15, 2009
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    Vertical distributions of the tropospheric ozone over Wakasa Bay, Enshu-nada and some other places in Japan were measured by a series of aircraft measurements during 1987-1991. The backward trajectories of air parcels with the ozone peaks and potential vorticity distributions around them were then analyzed to study their origin. This result showed that the ozone peaks over Japan sometimes originated from the tropopause folding which occurred in the west of Japan. Two ozone peaks had different altitudes and concentrations over Enshu-nada on 21 January 1989 which originated from different tropopause foldings. They seemed to diffuse during the transport which resulted in a stratified structure forming over Japan. The two similar ozone peaks, which originated from the identical tropopause folding and were observed 300km away on 21 January 1989, belonged to the identical ozone layer based on the potential temperature inclination. Two different types of air masses were simultaneously observed at different points over Japan on 8 August 1990. One was the continental air mass which showed a high ozone and a low water vapor concentration being transported from the northeast of China. The other was the maritime air mass which showed a low ozone and a high water vapor concentration staying over the sea for a few days that didn't come across the stratospheric air mass and pass over the metropolitan area. However, the ozone and water vapor showed a positive correlation even when the maritime air mass passed over the metropolitan or industrial areas, thus showing that the concentrations of the ozone and vapor were both high. The vertical distribution of ozone on 27 April 1991 over Tsukuba was almost uniform and the concentration was approximately 70ppbv. This suggested that the air masses came from the folding area whose vertical inclination of potential vorticity was small and was transported shortly after this event. Not only intrusion from the stratosphere but diffusion during the transport was also important for the ozone distribution over Japan based on the relationship between the concentration of ozone and the distance of transport.
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  • Masaki Satoh
    Volume 73 (1995) Issue 6 Pages 1059-1078
    Released: September 15, 2009
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    As a tool for understanding the meridional circulation of the atmosphere, a two-dimensional (latitude-height) numerical model is used to clarify the relationship between the Hadley circulation and large-scale motions associated with moist convection. The model is based on the primitive equations including the moist process, and two kinds of coordinates are used: the spherical coordinate and the Cartesian coordinate with a uniform rotation. The surface temperature is externally fixed and the troposphere is cooled by the radiation; unstable stratification generates large-scale convective motions.
    Dependencies on the surface temperature difference from north to south ΔTs are investigated. The numerical results show that a systematic multi-cell structure exists in every experiment. If the surface temperature is constant (ΔTs=0), connective motions are organized on the scale of the Rossby deformation radius and their precipitation patterns have a periodicity of the advective time τD. As ΔTs becomes larger, the organized convective system tends to propagate toward warmer regions. The convective cells calculated in the Cartesian coordinate model are very similar to those of the mid-latitudes in the spherical coordinate model. As the convective cells approach the equator, their cell scales become larger. In particular, in the case of the symmetric condition about the equator, the Hadley cell can be regarded as one of the convective cells which exists at the equator.
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  • Katsumi Tamaki, Kazuo Ukaji
    Volume 73 (1995) Issue 6 Pages 1079-1085
    Released: September 15, 2009
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    Baroclinic flows in an open cylinder with rim heating and center cooling are studied by laboratory experiments. The experiments have been carried out at room temperature, kept as close as possible to the rim temperature, without any additional heating such as the internal heating due to incandescent lights employed by Spence and Fultz (1977).
    Visual observations and temperature measurements of the top-surface have shown that axisymmetric time-independent flows, steady waves and regular periodic vacillations occur, in addition to irregular wavy flows. A régime diagram for these flows is presented with the fluid depth as ordinate and the angular speed as abscissa. Flow characteristics revealed by the temperature measurements are also described.
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  • Ryuichi Kawamura, Takio Murakami
    Volume 73 (1995) Issue 6 Pages 1087-1114
    Released: September 15, 2009
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    The influence of the low-level mean summer monsoon flow on 45-day transient eddies through barotropic interaction is diagnosed by a scalar product between the horizontal shear vector and Eliassen-Palm (E-P) flux, while the dry (moist) baroclinic interaction is measured by a vector product between the vertical wind shear and the eddy sensible (latent) heat transport, which represents the vertical component of E-P fluxes. Activity of 45-day transient eddies was monitored by the evolution of kinetic energy during the 9-year period of 1985-1993.
    The 45-day wave activity is relatively weak over the SEAM (Southeast Asian monsoon) domain. Absence of geographically fixed forcing makes the WNPM (western North Pacific monsoon) more violent, with the peak 45-day wave activity occurring in late August, the time of frequent development of vigorous tropical cyclones. Near the WNPM updraft center (15°N, 140°-150°E), the E-P wave energy fluxes are oriented in a direction which causes weakening of the sheared mean zonal and meridional winds, implying barotropic amplification of 45-day waves. The weak mean temperature gradient relegates the dry baroclinic instability to that of secondary importance over the WNPM domain. This is contrasted with the significant moist baroclinic process due to an approximate perpendicular relationship between the eddy moisture transport and the strong vertical shear of the monsoon flow.
    Curiously, 45-day waves are quite active near Japan even during August's dry, hot climate. Neither barotropic nor dry (moist) baroclinic instability can account for late-summer disturbance activity. Evidence is presented that 45-day convective oscillations occuring over the WNPM domain induce a strong 45-day response near Japan and further eastward, possibly indicating an intraseasonal Rossby wave dispersion along the westerly jet stream. Near the Aleutian Islands, a pronounced poleward eddy sensible heat flux is directed down the mean temperature gradient, resulting in dry baroclinic amplification of mid-latitude 45-day waves via action of the Coriolis torque. An import of moisture from the WNPM source region brings about a moist baroclinic instability of extratropical 45-day waves poleward of the Pacific High.
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  • Hakaru Mizuno, Norihiko Fukuta
    Volume 73 (1995) Issue 6 Pages 1115-1122
    Released: September 15, 2009
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    To understand ice nucleation under high supersaturation in clouds, measurements of natural ice nuclei for supersaturation with respect to water (Sw) up to 10% from -20 to -24°C were carried out using a horizontal gradient, continuous flow, ice thermal diffusion chamber after solving the spurious count problem due to ice crystal protrusion on the bottom plate with the addition of a small amount of ethylene glycol. The measurements were made with continental air masses in early summer of 1993 at Salt Lake City, Utah in the United States of America.
    The measured ice nucleus concentration under the condition of -20°C and Sw 5% showed a daily variation. The ice nucleus concentration changed from about 10l-1 in a warm air mass to about 1l-1 in a cold air mass, respectively, before and after the passage of a cold front in the synoptic scale. It was inferred that the instability of the warm air mass helps raise the particulates from or near the ground to increase the ice nucleus concentration. In order to pick out the supersaturation dependence at the various temperatures, the ratio of the ice nucleus concentration (N) to that at water saturation (No) was estimated. On average, Sw increases of 5 and 10% raised the N/No ratio by as much as a factor of two or more, respectively. It was found that a general relationship exists between N/No and Sw, and the slope further steepens above water saturation.
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  • Ryoichi Imasu, Atsuo Suga, Taroh Matsuno
    Volume 73 (1995) Issue 6 Pages 1123-1136
    Released: September 15, 2009
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    Instantaneous radiative forcing was calculated for 5 fluoroalcohols, 21 fluoroethers, and 5 fluoroamines which had been proposed as the replacement compounds for the currently used chlorofluorcarbons (CFCs) in refrigeration. Theatmospheric lifetimes of the compounds were also estimated from highest-occupied molecular orbital (HOMO) energy. Based on the radiative forcing and atmospheric lifetimes, halocarbon global warming potentials (HGWPs) were evaluated for the replacement compounds. Most of the HGWP values were smaller than 0.1 owing to their shorter lifetimes, and the results indicate that these compounds could be valid candidates as replacements for currently used CFCs from the point of view of HGWP.
    The spectral cooling rate profiles were calculated for the replacement compounds in order to study the vertical structure of their radiative effects. It was found that overlapping of the absorption bands of a compound with those of ozone causes a significant cooling in the stratosphere, even if the compound does not exist in the stratosphere. This cooling does not directly relate to the HGWP value and the cooling rate profile in the troposphere. Therefore, it can be said that the vertical structure of the radiative effects caused by the compounds should be taken into consideration as well as HGWP or GWP values when we assess the environmental effects due to replacement compounds. In this study, one parameter, defined as the ratio of the cooling rate at 30km and the tropopause, was proposed as a measure of the cooling in the stratosphere.
    Spectral-resolution dependency of the calculated radiative effects was also studied. The results show that the resolution should be finer than about 50cm-1 to calculate the radiative forcing and cooling rate precisely.
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  • Yutaka Ishizaka, Yoshinobu Kurahashi, Haruo Tsuruta
    Volume 73 (1995) Issue 6 Pages 1137-1151
    Released: September 15, 2009
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    Microphysical properties of stratiform clouds were observed over the Southwest Islands Area as a part of intensive field observations of Western North-Pacific Cloud-Radiation Experiments (WENPEX). The observation was made under the weak outbreak of cold airmass in January 1991. The observed clouds were mainly stratocumulus clouds, whose cloud depths were about 0.5 to 1.2Km. A strong temperature inversion was always observed near the cloud tops, above which there was a stable dry layer. The air temperature near cloud tops reached values lower than 0°C for some clouds (minimum temperature: -5°C). The clouds consisted mainly of cloud droplets and they were non-precipitating clouds. The clouds showed considerable horizontal inhomogeneity and vertical changes. The number concentration of cloud droplets in the central parts of clouds showed a tendency to be constant with height. The mean concentration reached approximately 500 to 800cm-3 as a result of a high CCN concentration. Mean droplet radius rose from about 3μm near cloud base to 7μm near cloud top. The vertical profiles of liquid water content (LWC) indicated that the values increased with height as a result of an increase in droplet size rather than concentration. The peak LWC reached about 1.0g/m3 in the thick clouds. The envelope of maximum LWC was generally smaller than the adiabatic values. Effective radius changed from about 3μm near cloud base to 6μm near cloud top. The characteristics of the stratocumulus clouds over the Southwest Islands Area in Japan is discussed from the microphysical standpoint, as compared with the stratiform clouds observed in geographically different areas.
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  • Koichi Watanabe, Yutaka Ishizaka, Hiroshi Tanaka
    Volume 73 (1995) Issue 6 Pages 1153-1160
    Released: September 15, 2009
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    Concentrations of gaseous peroxides and other trace gases (O3, SO2) have been measured near the summit of Mt. Norikura (altitude, 2770m) in central Japan, during summer and early autumn. Hydrogen peroxide (H2O2) and O3 reached the maximum concentrations at midnight and the minimum at midday. The maximum concentrations of H2O2 and O3 appearing at midnight are likely to be caused by subsidence from a higher atmospheric level. This tendency is quite opposite to that appearing in the low-altitude flat areas. The ratio of [H2O2]/[SO2], which is a useful indicator of the oxidizing capacity from SO2(S(IV)) to H2SO4(S(VI)), was almost larger than 1 during summer. This means that oxidant of SO2 is plentiful in the summer season and is likely to accelerate the heterogeneous oxidation in atmospheric water droplets.
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  • Hirotada Kanehisa
    Volume 73 (1995) Issue 6 Pages 1161-1166
    Released: September 15, 2009
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    Gravity waves associated with the density current in a stably stratified environmental flow are considered employing a 2-dimensional steady adiabatic Boussinesq system, confined to a region between 2 horizontal planes separated by a height H. The consideration is restricted to gravity waves which are stationary relative to the density current. The system consists of warm and cold air masses, the buoyancy frequency of the former is N, and the propagation speed of the latter is U. The following results are obtained. If the stratification within the warm air mass is sufficiently weak compared with that between the warm and cold air masses, then far upstream or downstream gravity waves do not emerge. On the other hand, if the stratification is so strong that NH/π>U, then far upstream and/or downstream gravity waves do necessarily emerge.
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  • Hiroshi Matsuyama, Taikan Oki, Kooiti Masuda
    Volume 73 (1995) Issue 6 Pages 1167-1174
    Released: September 15, 2009
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    A diagnostic study was conducted to evaluate the applicability of ECMWF's global analysis data to the quantitative analysis of the interannual variability of the water budget of the Mississippi river basin. Vertically integrated vapor flux convergence over the entire basin was compared to monthly precipitation minus evapotranspiration (P-E) from 1985 to 1988. Evapotranspiration was calculated from Thornthwaite's formulation. Comparison with the annual run-off near the river mouth was also made for the years 1985 to 1992.
    The absolute values of the monthly vapor flux convergence were found to be less than the values of P-E from September 1986 to the end of 1988. Natural variability was insufficient to explain the discrepancy between P-E and the vapor flux convergence. We believe changes in the 4DDA system were largely responsible for the discrepancy. We also believe the initialization used in the ECMWF analysis weakens the divergent part of the wind field.
    With respect to the study conducted with the presently available ECMWF data, the interannual variability of the water budget should not be discussed quantitatively, even for the Mississippi river basin, where many radiosonde stations are in operation.
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  • Isamu Hirota, Kazutaka Yamada, Kaoru Sato
    Volume 73 (1995) Issue 6 Pages 1175-1179
    Released: September 15, 2009
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    An analysis is made, with the aid of ECMWF operational data, of medium-scale, eastward-traveling waves in the mid-latitude upper troposphere over the north Atlantic area as a counterpart of the similar analysis of Sato et al. (1993) for the medium-scale waves over Japan.
    It is shown that the waves dominate in wintertime (January and February of 1990) over the north Atlantic centered around 50°N, with the typical wavelength of 2400km, a period of 33 hours, and hence an eastward phase velocity of about 20ms-1.
    In view of their vertical structure and relationship to the background zonal flow, it is concluded that the wave character obtained in this analysis is the same in essence as that shown by Sato et al. (1993).
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  • Yoshihisa Matsuda
    Volume 73 (1995) Issue 6 Pages 1181-1189
    Released: September 15, 2009
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    The three-dimensional response of a slowly-rotating atmosphere to mobile heating is investigated by using linearized primitive equations. The primitive equations are separated into the horizontal and vertical structure equations. The Hough functions are used in the numerical treatment of the horizontal equations.
    The velocity of planetary rotation and that of solar heating are fixed at the values for Venus. The responses are obtained for various values of the atmospheric stability and damping rate. For the large damping rate, a direct circulation between the day and night sides is obtained, while for small damping rates the zonal winds predominate and the geostrophic relation is established in the extratropics.
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  • Tsutomu Takahashi, Kenji Suzuki, Caiwei Wang, Changming Guo
    Volume 73 (1995) Issue 6 Pages 1191-1211
    Released: September 15, 2009
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    Precipitation mechanisms were investigated in summer rainfall in the semi-arid region of Pingliang, China as part of the Heihe River Field Experiment (HEIFE). Evolution of precipitation particles was investigated using videosonde images. Radar, surface electric field and balloon ascent rates were also referred for the study.
    The most noteworthy result was finding two completely different rain systems in the area, one in locally developed thunderstorms and the other in rain systems associated with the Baiu front. In the electrically active local thunderstorms, rain is formed through graupel formation. Snowflakes are the primary precipitation particles in Baiu frontal cloud systems. The concept of generation cell involvement in rain formation may not be applicable in Baiu frontal systems.
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  • Ken Sahashi
    Volume 73 (1995) Issue 6 Pages 1213-1217
    Released: September 15, 2009
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    In the HEIFE area at the northern foot of the Tibetan Plateau, a marked wet period which seems to be accompanied by a monsoon from the Indian Ocean was found in summer. The wet period was often accompanied by precipitation. An noticeable phenomenon is that the precipitation area moves in association with an anticyclone.
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  • Kuranoshin Kato, Jun Matsumoto, Hiroyuki Iwasaki
    Volume 73 (1995) Issue 6 Pages 1219-1234
    Released: September 15, 2009
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    The appearance frequency of Cb-clusters and its diurnal variation were examined in relation to large-scale conditions based on the observational data from June to August 1979. The analysis was applied to the three stages in the seasonal march in that year, i. e., “Pre-Meiyu” (1-17 June), “Meiyu” (20 June-22 July) and “Mid-summer” (23 July-17 August). The main results are as follows.
    (1) The Cb-clusters appeared frequently not only in the Baiu frontal zone but also in North to Northeast China (Area N1) in “Meiyu”, and in Central China (Area C2) in “Mid-summer”. A remarkable diurnal variation of appearance frequency of the Cb-clusters with an evening maximum was observed in Area N1 in “Meiyu” and Area C2 in “Mid-summer”. The daily maximum of ground surface temperature in these two cases was very high.
    (2) In Area N1 in “Meiyu”, the Cb-clusters with diurnal variation were mainly embedded in large-scale cloud systems corresponding to slow-moving upper-level lows or troughs. The specific humidity in the lower layer increased from “Pre-Meiyu” to “Meiyu”. These two factors, as well as the strong surface heating, would provide a favorable condition for the frequent appearance of Cb-clusters due to the increase of convective instability. The large-scale horizontal convergence in the lower layer was stronger at 12 UTC (20 BST) than at 00 UTC (08 BST), which would lead to the development of Cb-clusters in the evening.
    (3) Area C2 was covered by the subtropical high, and the low-level divergence was generally stronger at 12 UTC than at 00 UTC. In spite of these conditions, the isolated Cb-clusters developed very frequently in the evening. The very strong surface heating in the daytime could contribute to release of the strong convective instability by generating meso-scale upward motion as a trigger.
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  • Jiemin Wang, Yaoming Ma, Massimo Menenti, Wim Bastiaanssen, Yasushi Mi ...
    Volume 73 (1995) Issue 6 Pages 1235-1244
    Released: September 15, 2009
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    To improve understanding of the processes of land surface-atmosphere interaction at a scale of 104km2 in HEIFE, the utilization of satellite remote sensing is indispensable. Landsat TM observation, because of its high spatial resolution, can be compared directly with surface measurements and be used for this purpose. The relevant data set as well as a state-of-the-art data processing methodology are discussed. A summer scene of TM was used to produce a set of maps of surface albedo, vegetation index, surface temperature, net radiation and other basic energy balance components of the whole area. Statistical analysis based on these maps revealed some quantitative significant land surface parameters. Future developments were discussed.
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  • J. Y. Chen
    Volume 73 (1995) Issue 6 Pages 1245-1261
    Released: September 15, 2009
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    Simultaneous wind data collected from micrometeorological tower stations and automatic weather stations have been used to investigate the principal features and seasonal variations of the wind fields in the HEIFE experimental area. Besides wind statistics from a less modified data set, a MASCON wind model was adopted in an objective investigation of the three-dimensional atmospheric boundary layer flow during IOP-2 and IOP-3. The results have shown that synoptic scale, mesoscale and sub-mesoscale motions play different roles in different places. Under strong wind conditions, a northwesterly wind is predominant in the area with significant features of mechanical constraint by the mesoscale topography. On fair weather days, the flow patterns exhibit strong diurnal and spatial variations. In the sites adjacent to the north slope of Qilian Mountain and along the valley axis, flows featuring thermal forcing by mesoscale terrain are apparent, but daytime flows show significant seasonal shifts due to the link with the synoptic winds. Around the northern part of the experimental area, diurnal variations of the flows show a more complicated site-dependent behavior, which is caused by the simultaneous influences of synoptic-scale wind and the flows induced by small-scale topography.
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  • Lixin Ren, Wenfang Lei, Weixiu Lu, Wen Zhang, Guanghua Zhu
    Volume 73 (1995) Issue 6 Pages 1263-1268
    Released: September 15, 2009
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    Measurements of the physical and chemical characteristics of desert aerosols in the Heihe region (Northwestern China) were conducted during the periods of April 13-30 and October 3-14, 1991. It was found that both the number and elemental concentrations of desert aerosols showed seasonal differences: higher in April and lower in October. While fine particles remained dominant in desert aerosols, blowing dust remarkably enhanced the proportion of coarse particles. The desert aerosol size spectra were characterized by 2-modes and they could be fitted very well to log-normal distributions. Besides an abundance of crustal elements, the desert aerosols also contained abundant Mg and Cl, which may originate from the saline-alkali soil, and S was probably contributed comparably from the soil and secondary particles.
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  • Yasushi Mitsuta, Taiichi Hayashi, Tetsuya Takemi, Yinqiao Hu, Jiemin W ...
    Volume 73 (1995) Issue 6 Pages 1269-1284
    Released: September 15, 2009
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    During the observation period of the project HEIFE, two severe storms were observed. The structure of these storms in the arid area are analyzed. The scales of the two storms were different from each other. One was of the order of 10km and the other of the order of 100km; however both storms were characterised by a strong downdraft within the well developed convective cloud: a squall line and a single cumulonimbus cloud, respectively. In the squall line case, strong winds with uniform wind direction continued for about three hours, which was caused by the widening of the squall line. In the case of the single cumulonimbus cloud, the wind field was divergent owing to the downdraft at the surface. These severe storms are similar phenomena in nature to those observed all over the world.
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  • Qiang Wang, Ping Zhu, Bangzhong Wang, Ruibin Jiang
    Volume 73 (1995) Issue 6 Pages 1285-1291
    Released: September 15, 2009
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    When the influence of a synoptic system is weak, nighttime drainage wind often occurs along the front range of the Qilian Mountains, the southwest fringe of the Hexi Corridor, which blows to the gobi (rock desert). The features of the drainage wind were analyzed using the data from two meteorological stations at the foot of the Qilian Mountains. The maximum wind was found at the 8m level and the depth of the flow was shallow. The flow dissipated quickly over the oasis. A sudden decrease in air temperature was observed below the 10m level, associated with the passage of the leading edge of the drainage flow. The upward momentum flux and the downward heat flux due to the turbulence increased just when the leading edge of the flow was passing.
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  • Makoto Taniguchi, Ichirow Kaihotsu, Kazuo Kotoda
    Volume 73 (1995) Issue 6 Pages 1293-1299
    Released: September 15, 2009
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    Stable isotopes (deuterium and oxygen-18) were used for determining the origin of water and interactions between groundwater and river water, and clarifying the relationship between groundwater salinity and changes in the isotopic components of groundwater in the HEIFE area, northwestern China. An indication that active mixing of groundwater and river water occurred from October to March, was recognized from seasonal changes in their isotopic components. The relationship between electrical conductivity and isotopic components of groundwater shows that there are two groups of sites. Groundwater in one group has the characteristic of increasing δD with increasing electrical conductivity (caused by evaporation), while the electrical conductivity of the groundwater in a second group does not change with changing isotope composition, and is identified as water of mountain origin.
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  • Zhibao Shen, Osamu Tsukamoto, Jilling Zou
    Volume 73 (1995) Issue 6 Pages 1301-1307
    Released: September 15, 2009
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    The characteristics of the surface radiation balance over desert and oasis in the HEIFE area were analysed and compared by use of the data observed at the Desert and Zhangye stations. The results show that ground surface plays an important role in the surface radiative energy budget, the non-uniform ground surface leads to a remarkable spatial variation of surface net radiation in the HEIFE area. Under a clear sky condition, the instantaneous fluxes of downward short-wave and long-wave radiations reaching the ground surface and their diurnal variations are nearly the same over desert and oasis in summer and winter. In summer, the difference of net radiation between desert and oasis (larger in the oasis by 11.2 MJ/m2 ·day than the desert) is caused by the differences of surface albedo and upward long-wave radiation in the day-time, but upward long-wave radiation has a more significant influence. In winter, the thermodynamic conditions of the ground surface in the HEIFE area are nearly the same, and the upward long-wave radiation at both stations is nearly the same. As a result, the difference of net radiation between oasis and desert. (larger in the oasis by 1.43 MJ/m2·day) is mainly caused by the difference in the albedo.
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  • Volume 73 (1995) Issue 6 Pages 1320
    Released: September 15, 2009
    JOURNALS FREE ACCESS
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