Local wind storm (Hirodo-kaze) in northern Okayama caused by Typhoon 0421 & 0423

In 2004, ten typhoons had landed over Japan and a lot of damages were reported due to heavy rain, storm surge and wind storms. In the north eastern part of Okayama prefecture, local high wind "Hirodo-kaze" caused severe wind damages due to typhoon passage. During Typhoon 0421, high winds were recoreded in the south foot of Mt.Nagi as typical local wind atrom, " Hirodo-kaze". While, during Typhoon 0423, severe wind damages expanded west of the typical Hirodo-kaze srea as well as a new extreme. In the present report, a lot of surface meteorological data were coollected and compared the meteorological fields among two typhoons.

Meteorological and surface heat balance characteristice over different surface condidtions in arid northwest China (HEIFE area)

Surface meteorological and heat balance were analyzed based on various surface conditions over arid region in northwest China (HEIFE area). The different surface conditions were clearly observed in summer rather than in winter. Summer data were selected from the HEIFE database. Significant evening peaks of vapor pressure were also observed in Linze oasis as well as Zhangye oasis. And the peak was accompanied by air temperature dip and relative humidity peak in the lower layer. However, the peak cannot be observed in high wind condition as the mechanical mixing reduces the vertical gradients of air temperature and humidity. The oasis can be characterized by low wind speed due to wind sheltering by plants. In winter, plant activities are reduced and surface conditions are almost similar for desert and oasis, leading to no peak of vapor pressure. Surface heat balances were also analyzed based on 4-component radiation measurement and sensible and latent heat flux measurements by eddy covariance method. Net radiation in the oasis area is about 50% larger than desert area due to the smaller upwelling radiation in oasis. Heat distribution into sensible heat and latent heat was different between oasis and desert. This unbalance of heat can lead to local circulation between oasis and desert as "desart-oasis interaction"

中国寧夏地域における日照時間から日積算日射量の推定

For the estimation of daily solar radiation from sunshine duration, observation data of Yinchuan station in Ningxia, China was used. Using a linear relationship between solar radiation and extraterrestrial radiation including relative sunshine duration and daylength, we obtained local coefficients s a =0.18, s b =0.62 from past five years data(1981-1985). Using the same method, coefficients for Guyuan region were confirmed too as a representative of south part of Ningxia province. Applying the local coefficients and calculation formula of solar radiation, we validated daily solar radiation of two years(1986-1987) of Yinchuan station and four years(1991-1994) of Guyuan station. The results showed high correlation coefficients of R2=0.94 in Yinchuan and R2=0.85 in Guyuan. Error analysis was applied using mean bias error(MBE), mean absolute bias error(MABE), root mean square error(RMSE)，mean absolute percentage error(MAPE) on solar radiation of Yinchuan(1973-2006) and Guyuan(1986-2006) stations. Results showed that mean absolute bias error(MABE) was less than 13% and 17% in Yinchuan station and Guyuan station respectively. Then we have applied this method to the estimation of daily solar radiation at ‘Yongning’ station(near Yinchan) with the sunshine duration data at ‘Yongning’. The estimated values were compared with observed daily solar radiation at Yinchuan as past twelve years data(1989-2000). The results showed good linear relationship with high correlation coefficient of R2= 0.88

中国淮河流域付近の入梅前の時期における大気場や陸面状態の季節進行 (1998年の事例解析)

　Seasonal evolution of atmospheric and land surface conditions around the Huaihe River Basin in China in the pre-Meiyu stage of 1998 were examined, mainly based on the GAME re-analysis data. Around the Huaihe River Basin in China (just to the nront of the Changjiang River Basin), although the air temperature increased rapidly already in early June (the Meuyu front was located to the south of that region), the specific humidity did not increas so much at time. In addition, the latent heat supplied from the ground there decreased from late May to early June, compared to that before early May. The time mean southerly wind component across the low-level baroclinic Zone (although not so strong as in the mature stage of the Meiyu) invaded into Central Cjina during late April to early May. On the other hand, the relatively strong wind region once retreated southward in the middle of May associated with the onset of the Southeast Asian monsoon, and the calm wind region with frequent appearance of the surface high was seen around the Huaihe River Basin from late May to early June. Thus the present study shows that the Huaihe River Basin once experiences the rather drier stage just before the onset stage of the mature Meiyu there

A case study on persistent appearance of the ensemble of precipitation bands in the warm sector of the Baiu front in the western Japan around 19 June 2001

A case study on persistent appearance of the ensemble of precipitation bands in the warm sector of the Baiu front in Kyushu District, the western part of Japan around 19 June 2001 was performed based on the operational observational data. Around 00UTC (09JST) 19 June when the Baiu front on the surface weather map was still located about a few 100kms to the north of Kyushu, the number and the total area of the meso-β or γ-scale line-shaped precipitation bands increased around Kyushu rapidly. These precipitation bands had been sustained there and gradually gathered each other to change into the Baiu frontal precipitation zone extending from the northern Kyushu to Seto-Naikai (Seto Inland Sea) around 09UTC (18JST) 19 June (the intense rainfall zone was still located in the warm sector of the Baiu front). Until ~09UTC (18JST) 19 June, the moist air flow with the latently unstable stratification had been sustained around Kyushu corresponding to the low-level southerly wind toward the surface Baiu front to the north of Kyushu. This large-scale situation would contribute greatly to the maintenance of the ensemble of the line-shaped precipitation bands in the warm sector of the Baiu front

Aerosol observation at Okayama with Skyradiometer and LIDAR

　Aerosol is one of the controlling parameter for the global climate and also effects on local health hazards. The measurement of the aerosol was originally carried out as in-situ sampling and mass weight measurement including chemical analysis. Recently, remote sensing method is applied as satellite remote sensing and surface based remote sensing. Skyradiometer and LIDAR are surface based remote sensing system. Skyradiometer measures solar radiation as direct and scattered solar radiation affected by aerosols. LIDAR emit laser beam upward and it is backscattered by overlying aerosols. The backscattered light is received by a telescope and vertical distributions of the aerosols are obtained. These measurements require atmospheric radiation physics. 　A Skyradiometer and a LIDAR were operated continuously at Okayama University campus and aerosol parameters were obtained from both of the system. Seasonal variations of the AOT (Aerosol Optical Thickness) and Angstrom parameter (α) are evaluated. During some dust events (e.g. yellow sand and PM2.5), time variations of these parameters were identified from both of the measurement system

Increase Rate of fCO2 in the Eastern Equatorial Pacific Ocean

In the Eastern Equatorial Pacific Ocean, increase rates of fCO2 in the air and the ocean were evaluated using the CDIAC data set. The fCO2 in the air was increasing about 1.28μatm/year during 1957-1995. This result is almost same as the rate at the Mauna Loa, Hawaii in Tropical Pacific Ocean. The increase rate of fCO2 in the seawater was estimated as 1.64μatm/year. In this study it is found that the increase rate of fCO2 in the seawater is the almost same as that of fCO2 in the air. This reault supports the result on the snapshot analysis of Takahashi et al. (1983) in thr North Atlantic Ocean during 1958-1982. It is smaller than the result including seasonal variation in the Eastern Subtropical Pacific Ocean. These reault indicated that the anthropogenic CO2 in the air has affected fCO2 in seawater through CO2 gas exchange between the atmosphere and the ocean. It is found that fCO2 in the seawater has increased in the Eastern Equatiorial Pacific Ocean in spite of the large CO2 source region. It suggested that CO2 source potential has not changed in this ocean durung 1957-1995

Storm surge in the Seto Inland Sea accompanied by Typhoons in 2004

In 2004, Seto Inland Sea coast suffered severe damages of storm surge. This area never experienced storm surge damage in recent half century and people were not ready for the storm surge. In two typhoons of T0416 and T0418, surge anomaly were more than 150cm in Bisan-Seto area. Storm surges appeared after the maximum approach of typhoon not only due to surface low pressure but also due to wind stress as westerly. Because of geographical complexity of Seto Inland Sea, the surge process have not been well understood. Therefore, it is necessary to study the effects of the wind and the surface pressure using a numerical model. Atmospheric model MM5 and ocean model POM were used as a numerical experiment, including the astronomical tide model NAO. Aｓ the results of numerical simulation of the storm surge, atmospheric conditions were well simulated but ocean model was rather complex. There are a lot of island in Seto Inland Sea and sea water movement in the model was very much influenced by the topography and wind stress effect appeared much smaller. In the no-island model, storm surge height was a little improved. However the simulated surge height was still less than the observed height. Further improvement of the ocean model application should be considered in future studies

Measurements of CO2 in air and sea over the Western Pacific-MR98-04 Cruise-

It is well known that the ocean plays a very important role in the overall geochemical cycle of CO2. Over the ocean surface, CO2 is equilibrated between partial pressure of CO2 in the seawater (pCO2) and that in the atmosphere(PCO2). The objectives of the present observation are to evaluate the following : (1) Horizontal distribution of pCO2 and PCO2, (2) Sea surface CO2 flux and (3) Vertical distribution of pCO2

Characteristics of typhoon tracks and large-scale atmospheric fields associated with the typhoon approach to the Japan Islands in early summer

The number of typhoons approaching the Japan Islands is much smaller in May and June than in August to September. However, some typhoons abnormally approach to the Japan Islands in May or June as in 2004. The present study investigated the characteristics of the typhoon tracks and the large-scale fields in May and June associated with the approach of typhoons to the Japan Islands. Climatologically speaking, typhoons are generally formed in the lower latitude in May and early June, and tend to turn to ENE-ward before they reach ~ 20N in May by the upper- and middle-level westerly wind. In June, the upper-level easterly wind associated with the Tibetan high seems to prevent typhoons from approaching to the Japan Islands. However, when the cell-type subtropical high and the deep westerly trough in its western side are formed with the SW-ly from the lower to the middle latitude, a favorable situation for the northward invasion of the typhoon can be realized in May. On the other hand, the formation of the barotropic-like subtropical high to the southeast of the Japan Islands seems to enable a typhoon to approach to the Japan Islands by the S-ly wind around the subtropical high