Ocean Dynamic Processes Responsible for the Interannual Variability of the Tropical Indian Ocean SST Associated with ENSO

Kug, Jong-Seong,An, Soon-Il Korean Meteorological Society 2010 大氣 Vol.20 No.2

The interannual variability of the tropical Indian Ocean SST is investigated by analyzing the ocean assimilation data. It is significant that since 1970, ENSO events frequently followed the Indian Ocean Dipole event. The SST tendency due to the dynamical SST advections over the tropical Indian Ocean sufficiently overwhelms that due to other thermodynamic process during the fall and winter of ENSO. Especially, the strong cooling due to the anomalous vertical advection by the mean upwelling and the warming due to the horizontal advection are attributed to the cold SST during the fall and the warm SST during the winter, respectively. The significant warming between winter and spring over the southwestern Indian Ocean turns out to be due to the vertical advection of the mean subsurface temperature by the anomalous upwelling during the winter and the vertical advection of the anomalous subsurface temperature by the mean upwelling from winter to spring. We speculate that when the Indian Ocean Dipole events concurred with the ENSO, the surface wind is so strong enough as to generate the change in the SST dynamically and overwhelm the SST changes associated with other effects.

Prototype for the Weather Monitoring System with Web - Based Data Management - Construction and Operation

Kim, Jinwoo,Kim, Jin-Young,Oh, Jai-Ho,Kim, Do-Yong Korean Meteorological Society 2010 大氣 Vol.20 No.2

In this paper, an attempt has been made to build and test self-configuring weather sensor networks and internet based observation system to gather atmospheric data. The aim is to provide integrated or real-time weather information in standard form using network data access protocol. This system was successfully developed to record weather information both digital as well as visual using sensor network and web-enabled surveillance cameras. These data were transformed by network based data access protocol to access and utilize for public domain. The competed system has been successfully utilized to monitor different types of weather. The results show that this is one of the most useful weather monitoring system.

Comparison of Typhoon Wind Models Based on Storm Surge Heights Induced by Typhoon Maemi

Kwon, Jae-Il,Lee, Jong-Chan,Park, Kwang-Soon,Jun, Ki-Cheon Korean meteorological society 2008 Asia-Pacific Journal of Atmospheric Sciences Vol.44 No.4

For various purposes related to storm surges, typhoon wind models have been developed and calibrated to simulate sea winds and pressures. In this study, we used two typhoon wind models in an ocean model to explore the storm surge heights, a topic rarely examined in the literature. Identical typhoon track and concentric atmospheric pressure distributions for Typhoon Maemi (0314) were applied to an empirical typhoon parametric model and the US Army Corps of Engineers (CE) wind model. The storm surge heights calculated by an ocean model, Korea Ocean Research and Development Institute - Storm surge model (KORDI-S) were compared with a total 11 of observations around the Korean Peninsula. A series of numerical experiments showed that the ocean responses (i.e., local maximum storm surge heights and peak times) were sensitive to the meteorological inputs by typhoon wind models in terms of the radius of maximum wind speed (r<SUB>max</SUB>). Both typhoon wind models, when given proper values of r<SUB>max</SUB>, accurately simulated the maximum surge heights induced by Typhoon Maemi. For the temporal history of storm surges, the CE wind model gave better performance.

Calibration of radar reflectivity measurements from the KMA operational radar network

Park, S. -G.,Lee, Gyuwon Korean meteorological society 2010 Asia-Pacific Journal of Atmospheric Sciences Vol.46 No.3

<P> A systematic procedure for calibrating system gain bias (so-called “calibration error”) of radar reflectivity measurements from the Korea Meteorological Administration (KMA) operational radar network is presented. First, the RJNI radar located at Jindo Island is calibrated by comparing with radar reflectivities simulated theoretically by a scattering algorithm using drop spectra collected by a disdrometer from June 19 to 29, 2009. Once the RJNI radar is calibrated, the reflectivity measurements from nearby radars are compared with the RJNI radar reflectivities to determine existing gain biases of nearby radars. This radar-radar calibration procedure was repeated with the other radars within the network. For isolating a system gain bias, echoes affected by partial beam blockage due to ground clutter and by attenuation due to precipitation were removed. The system gain biases of the RJNI and RPSN radars were -3 and -4.2 dB, respectively, during the experimental period. The RBRI and RDNH radars revealed relatively large biases, above -8 dB. The other radars (RKSN, RGSN, RSSP, RKWK, RGDK, RIIA, and RMYN) revealed biases from -6 to -7 dB. Thus, the reflectivity measurements from all of the KMA radars were severely biased. New R-Z relations of R = 3.350 × 10<SUP>-2</SUP>Z<SUP>0.624</SUP> (Z = 231.1R <SUP>1.6</SUP>) for stratiform and R=1.546 × 10<SUP>-2</SUP> Z<SUP> 0.714</SUP> (Z = 342.4R <SUP>1.4</SUP>) for convective precipitations were derived using disdrometer data. Using these R-Z relations, the radar-derived total rainfall amounts from the reflectivity measurements without calibration produced significant underestimations, compared to gauge measurements at about 80 sites, with a normalized bias of about -56%. On the other hand, after calibrating the above system biases, the radar-derived rainfall amounts corresponded well with the gauge measurements, with a normalized bias of about -3%. In conclusions, the radar reflectivity measurements from the KMA radar network are severely biased and the procedure presented in this study can be used to resolve the system gain biases. </P>

Parameterization for Longwave Scattering Properties of Ice Clouds with Various Habits and Size Distribution for Use in Atmospheric Models

Jee, Joon-Bum,Lee, Kyu-Tae Korean Meteorological Society 2013 大氣 Vol.23 No.1

A parameterization for the scattering of longwave radiation by ice clouds has been developed based on spectral scattering property calculations with shapes and sizes of ice crystals. For this parameterization, the size distribution data by Fu (1996) and by Michell and Arnott (1994) are used. The shapes of ice crystal considered in this study are plate, solid column, hollow column, bullet-rosette, droxtal, aggregate, and spheroid. The properties of longwave scattering by ice crystals are presented as a function of the extinction coefficient, single-scattering albedo, and asymmetry factor. The heating rate and flux by the radiative parameterization model are calculated for wide range of ice crystal sizes, shapes, and optical thickness. The results are compared with the calculated results using a six-stream discrete ordinate scattering algorithm and Chou's method. The new method (with various habits and size distributions) provides a good simulation of the scattering properties and cooling rate in optically thin clouds (optical thickness < 5). Depending on the inclusion of scattering by ice clouds, the errors in the calculation of the cooling rates are significantly different.

Erratum

Shi, Hoyeon,Lee, Sang-Sam,Chun, Hyuong-Wook,Song, Hwan-Jin,Noh, Young-Chan,Sohn, Byung-Ju Korean Meteorological Society 2016 대기 Vol.26 No.3

Variations of the Polar Temperature in the Lower Stratosphere during 1955-2004

Choi, Wookap,Kim, Dongjoon Korean Meteorological Society 2008 大氣 Vol.18 No.4

The lower-stratospheric polar temperature in winter and spring for both hemispheres is investigated based on the NCEP/NCAR 50-year reanalysis data with respect to the strength of the stratospheric eddy heat flux. Both the polar temperature and the eddy heat flux show significant variation on the decadal and year-to-year time scales except during the Southern Hemisphere winter. The year-to-year variation in the polar temperature is mainly determined by the eddy heat flux convergence. The eddy heat flux convergence is compared with the diabatic heating rate obtained from a two-dimensional model. Radiative heating caused by absorption of solar radiation is comparable to the heating caused by the eddy heat flux convergence in the Southern Hemisphere. The effect of ozone depletion on diabatic heating has been found to be secondary in the Northern Hemisphere, even in March 1997 when the record depletion of ozone took place.

Three Cases with the Multiple Occurrences of Freezing Rain in One Day in Korea (12 January 2006; 11 January 2008; and 22 February 2009)

Park, Chang-Kyun,Byun, Hi-Ryong Korean Meteorological Society 2015 대기 Vol.25 No.1

From the hourly data of 75 Korean weather stations over a 12-year period (2001~2012), this study has chosen three cases (January 12, 2006; January 11, 2008; and February 22, 2009) of multiple freezing rains and investigated the atmospheric circulations that seemed to cause the events. As a result, the receding high pressure type (2006), prevailing high pressure type (2008), and warm front type (2009) are confirmed as synoptic patterns. In all three cases, freezing rain was found in regions with a strong ascending current near the end point of a low-level jet that carried the warm humid air from low latitudes. The strong ascending current resulted from lower-level convergence and upper-level divergence. In 2006 and 2009, the melting process was confirmed. In 2008, the supercooled warm rain process (SWRP) was confirmed. In contrast to existing SWRP theory, it was found that the cool air produced at the middle atmosphere and near the earth's surface led to the formation of freezing rain. The sources of this cool air were supposed to be the evaporative latent heat and the cold advection coming from the northeast. On the other hand, a special case was detected, in which the freezing rain occurred when both the soil surface temperature and surface air temperature were above $0^{\circ}C$. The thickness distributions related to freezing rain in Korea were found to be similar to those in North America. A P-type nomogram was considered for freezing rain forecasting; however, it was not relevant enough to Korea, and few modifications were needed.

The Fine Power Spectra of the Southern Oscillation Index and Its Components and their Implication

Lim, G.-H.,Suh, Y.-C. Korean Meteorological Society 2015 大氣 Vol.25 No.3

As is evident from its definition, Southern Oscillation Index variability conformed to a combination of the variations of Darwin and Tahiti pressure. Over the El-$Ni{\tilde{n}}o$ Southern Oscillation spectra, the Darwin pressure shared variations associated with the SSN tendency while the Tahiti had a connection with the stratospheric quasi-biennial oscillation modulating annual cycle. The power peak near the 3.5-year period comprised the third harmonic of the sun and the second of the modulated annual cycle. The derived harmonics came from both sources, so the initiation of El-$Ni{\tilde{n}}o$ could be predicted more successfully when including the effects of the sun and QBO.

Interaction among the East Asian Summer and Winter Monsoons, the Tropical Western Pacific and ENSO Cycle

Huang, Rong-Hui,Lu, Ri-Yu,Chen, Wen,Chen, Ji-Rong Korean Meteorological Society 2003 大氣 Vol.13 No.2

Recent advances in the studies on the interaction between Asian monsoon and ENSO cycle are reviewed in this paper. Through the recent studies, the East Asian summer monsoon circulation system and the East Asian climate system have proposed. Moreover, different responses of the (winter and summer) monsoon circulation and summer rainfall anomalies in East Asia to ENSO cycle during its different stages have been understood further. Recently, the studies on the dynamical effect of East Asian monsoon on the thermal variability of the tropical western Pacific and ENSO cycle have been greatly advanced. These studies demonstrated further that ENSO cycle originates from the tropical western Pacific, and pointed out that the dynamical effect of East Asian winter and summer monsoons on ENSO cycle may be through the atmospheric circulation and zonal wind anomalies over the tropical western Pacific, which can excite the oceanic Kelvin wave and Rossby waves in the equatorial Pacific. Besides, the scientific problems in the interaction between Asian monsoon and ENSO cycle, which should be studied further in the near future, are also pointed out in this paper.