On the freezing precipitation in korea and the basic schemes for its potential prediction

This study aims to improve the forecasting skill for freezing precipitation. A total of 102 freezing precipitation cases were collected in South and North Korea from 2001 onwards. Temperature fields on the ground and in the atmosphere, vertical temperature profiles, geopotential fields, thickness fields and their spatiotemporal variations, and their combinations using the predominant precipitation-type nomograms (P-type nomograms) were classified and investigated to determine whether or not these data could be used as predictors. Results show that 1) the combination of the thicknesses of 1000-850 hPa and 850-700 hPa is recommended for the P-type nomograms for Korea, which is different from that used in the United States in threshold values; 2) 35 out of 72 synoptic situations are possible conditions for freezing precipitation; and 3) 3 groups out of those 35 situations, i.e., the 1000 hPa warmfront group, the mid-level southerly category of 850 hPa, and the mid-layer warm type in the vertical temperature profile, show the greatest frequency. Freezing precipitation occurs only in a small part of a possible area. Therefore, despite the increasing observations in the year-on-year trend, only a few of the cases have been detected. The possibility of observation errors is also one of the biggest problems. Therefore, the need for new equipment, such as a freezing rain detector (FRAD), to detect the phenomenon automatically is required and proposed. A denser observing system of FRADs and an ultra-fine gridded numerical model are suggested as a solution for the prediction of freezing precipitation.     

Quantitative definition and spatiotemporal distribution of little water season (LIWAS) in Korea

Like other continental climatic regions Korea has a period around the spring when agricultural activities are interrupted frequently by a shortage of available water resources during the season. This season, which is termed the Little Water Season (LIWAS) in this study, has important implications for many socio-economic activities but the scientific definition of this season remains vague. In this study, the onset and termination dates, as well as the characteristics of the LIWAS have been defined based on the Available Water Resources Index (AWRI). Based on the proposed definition of LIWAS, the implications on hydrological conditions over a range of geographic scales and their inter-annual variations on the water resource environments in Korea have been assessed. To develop an appropriate index for LIWAS based on AWRI, the criterion value (CV) for LIWAS was set as the lowest 25th percentile of the AWRI values averaged for 30 years (1981-2010). Therefore, the Little Water Season for Korea (LIWAS_K) was considered as the period when the daily averaged AWRIs were successively lower than the CV (143.7 mm). Based on this, the mean onset and end date of LIWAS_K, was 9 February and 11 May which also reflected the period in the spring season when the available water resources are expected to the lowest. Moreover, a number of seasonal characteristics of the water availability during the LIWAS, such as the Little Water Intensity (LWI), Water Deficit Amount (WDA) and Water Deficit Intensity (WDI) have been defined for the particular study region. Based on our results, we aver that the proposed season classification of the LIWAS can be better analyzed using the concept of usable water resources as a classification of dry period instead of using temperature and raw rainfall datasets.     

Acidification at the Surface in the East Sea: A Coupled Climate-carbon Cycle Model Study

This modeling study investigates the impacts of increasing atmospheric CO₂ concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO₂ concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO₂ uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO₂ increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO₂ decreased.     

TAOS: The Taiwanese–American Occultation Survey

The Taiwanese–American Occultation Survey (TAOS) seeks to determinethe number and size spectrum for small (～3 km) bodies in the KuiperBelt. This will be accomplished by searching for the brief occultations of brightstars (R～14) by these objects. We have designed and built a specialpurpose photometric monitoring system for this purpose. TAOS comprisesfour 50 cm telescopes, each equipped with a 2048×2048 pixel CCDcamera, in a compact array located in the central highlands of Taiwan. TAOSwill monitor up to 3,000 stars at 5 Hz. The system will go into scientificoperation at the end of 003.     

Effects of El Ni?o Modoki on winter precipitation in Korea

This study compares the impacts of El Ni?o Modoki and El Ni?o on precipitation over Korea during the boreal winters from 1954 to 2009. Precipitation in Korea tends to be equal to or greater than the normal level during an El Ni?o Modoki winter, whereas there is no significant change during an El Ni?o winter. Greater than normal precipitation during El Ni?o Modoki was also found over the lower reaches of the Yangtze River, China and much of southern Japan. The latitudes of these regions are 5–10° further north than in southern China, where precipitation increases during El Ni?o. The following two anomalous atmospheric circulations were found to be causes that led to different precipitation distributions over East Asia. First, an atmospheric wave train in the lower troposphere, which propagated from the central tropical Pacific (cyclonic) through the southern Philippine Sea (anticyclonic) to East Asia (cyclonic), reached the southern China and northern Philippine Sea during El Ni?o, whereas it reached Korea and southern Japan during El Ni?o Modoki. Second, an anomalous local meridional circulation, which consists of air sinking in the tropics, flowing poleward in the lower troposphere, and rising in the subtropics, developed between the southern Philippine Sea and northern Philippine Sea during El Ni?o. During El Ni?o Modoki, however, this circulation expanded further to the north and was formed between the southern Philippine Sea and regions of Korea and southern Japan.     

Seasonal variations in the low-salinity intermediate water in the region south of sub-polar front of the East Sea (Sea of Japan)

Seasonal variations in the low-salinity intermediate water (ESIW) in the region south of the sub-polar front of the East Sea were investigated by using historical hydrographic data. The salinity of the representative density (sigma-0=27.2) of the ESIW was minimal in summer and maximal in winter in the region south of the sub-polar front. The selected four subregions showed different salinity variations. In the west of Oki Spur and the Yamato Basin, salinity fluctuated similarly, with a minimum during summer. In the Ulleung Basin and northwest of Sado Island, however, variations in salinity showed two minima, one is in winter and the other is in summer. These results imply differences in the flow path of the ESIW into the region south of the sub-polar front over time.     

Development of Control Softwares for the SRAO 6-Meter Telescope Based on PCs Running Linux

We have developed a control system for the Seoul Radio Astronomy Observatory (SRAO) 6-meter telescope operating in the 85–115 Ghz frequency range. Four PCs running the Linux operating system control source tracking, take data, execute observations and handle user interface. The control system utilizes a modular and multiprocessing structure to facilitate easy upgrading and troubleshooting. Communication between the processes relies on the interprocess communication (IPC) resources on Linux such as shared memory, message queues, and TCP/IP sockets. Communication between PCs is made via an Ethernet link. We also use digital I/O lines for some status signals which require a short delay. The control system supports scheduling observations, updates observation logs automatically and also supports graphical user interfaces. These all makes the operation easy. By using a commercially available motion control card with an embedded microcomputer for antenna control, we achieved a tracking accuracy to better than 1 arcsec. This revised version was published online in July 2006 with corrections to the Cover Date.