Monitoring and Predicting Agricultural Drought, 2005
South Korea (hereinafter referred to as Korea) lies in the middle latitudes of the Northern Hemis... more South Korea (hereinafter referred to as Korea) lies in the middle latitudes of the Northern Hemisphere. Until the 1960s, Korea was a typical agrarian country, with agriculture generating roughly half of its gross national product (GNP) and employing more than half of the labor force. Agriculture still plays an important role in the Korean national economy, but it accounts for a relatively much lower share of the GNP (5.3% in 1997) and engages much less of the population (11.0%). The agricultural share of the national economy is declining continuously. Farms in Korea, as in many other Asian countries, have traditionally been small. Average farm size has been growing slowly from 0.86 ha in 1960 to 1.39 ha in 2001, despite a significant reduction in the average number of persons per household engaged in farming—from 6.20 persons to 2.91 persons. As a result, agriculture has become more intensive. The country has four distinct seasons: summer, fall, winter, and spring. Summer and winter...
최근 30년간(1979-2008년) 한반도 주변(32-36 N, 122-132 E)에서 태풍이 약화될 때 한국에서 나타나는 시공간적 강수 특징을 분석하였다. 약화 유형은 온대... more 최근 30년간(1979-2008년) 한반도 주변(32-36 N, 122-132 E)에서 태풍이 약화될 때 한국에서 나타나는 시공간적 강수 특징을 분석하였다. 약화 유형은 온대저기압으로 약화되는 태풍(Weakened to Extratropical Cyclone, WEC)과 열대성 저압부로 약화되는 태풍(Weakened to Tropical Depression, WTD)으로 구분하였다. WEC의 경우, 강수량은 전국에 걸쳐 골고루 분포하였으며 남해안에서 가장 많았다. WTD의 경우, 강수량은 남해안에서 가장 많았지만 중부 및 내륙지역은 적었다. 두 경우의 강수량 차이는 Region 2(전라남도, 경상남도, 경상북도 남동부 지역, 제주도)에서는 거의 없었으며, Region 1(중부지방, 전라북도, 경상북도 내륙)에서는 WTD보다 WEC일 때 강수량이 더 많았다. 태풍이 한반도로 접근 할 때 WEC의 경우 태풍의 북서쪽에는 상층의 발달된 잠재소용돌이도와 하층의 온도골이 위치하고 있었으며, 태풍의 북동쪽에는 상층 제트 및 강한 상층 발산역이 위치하였다. 이는 태풍 전면에 경압교란과 비단열 과정을 발달시켰고 이로 인해 강수영역이 넓게 형성된 것으로 추측되었다. 그러나 WTD의 경우에서는 강한 잠재소용돌이도나 온도골, 상층제트가 태풍 주변에 나타나지 않았으며, 이로 인해 강수영역이 좁게 형성되었다.
Bangladesh, located in the Bay of Bengal, is a developing nation that is prone to devastating flo... more Bangladesh, located in the Bay of Bengal, is a developing nation that is prone to devastating flood events that cause loss of lives and several other forms of humanatarian disasters. Identifying, developing and validating new scientific techniques that can be used for flood-risk warning and regular monitoring, including flood risk mitigation and adaptation, can help reduce the catastrophic effect of floods in Bangladesh and other developing countries. In this study, a daily Flood Index (I F ) based on daily effective precipitation (P E ) is utilized for quantifying floods for two cites in Bangladesh: Dhaka (23.7°N, 90.38°E) and Bogra (24.51°N; 89.22°E), where flooding is a common phenomenon. Based on total daily precipitation (P) data, in this study the I F is determined by calculating the P E using an exponentially decaying time-reduction function, which considers the gradual depletion of water resources over time. P E per day is normalized and compared with the average and standard deviation of yearly maximums, within the considered hydrological period. The start of a flood event is identified for I F ≥ 0. Subsequently, the I F severity (I acc F ) as consecutively positive I F , duration (D F ) as number of days with positive I F , and peak danger (I max F ) as maximum I F are estimated for identified flood events, using the run-sum theory. The analysis carried out has accurately identified historical flood events at Dhaka station in 1984 and 2007 as having the largest I acc F value (i.e., greatest severity). Flood severity (I acc F ) and peak danger (I max F ) parameters have been verified by accumulated precipitation corresponding to the same period. For Bogra station, the 1998 and 1979 events were found to be the most intense. Seasonality analysis of the flood index shows most floods happened during the summer monsoon, although for the Dhaka station, flood events occurred between early June and November, and in Bogra, from late June to October. A rational study of effective precipitation provides a useful severity and danger indicator. The results indicate the practicality of daily I F for flood-risk assessments where the severity, peak danger, and duration need to be considered as a unified index for flood-risk monitoring. The proposed daily flood index can be useful for hydrologists for the purpose of daily operational flood monitoring in high flood-risk nations.
Asia-Pacific Journal of Atmospheric Sciences, 2016
This study aims to improve the forecasting skill for freezing precipitation. A total of 102 freez... more 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.
The spatiotemporal distributions of latest frost dates (LFDs) on the Korean Peninsula and the atm... more The spatiotemporal distributions of latest frost dates (LFDs) on the Korean Peninsula and the atmospheric circulation patterns that resulted in the latest frosts (LFs) were investigated through the use of historical records and modern weather observation data. During the modern observation period since 1904, the most recent record of LF was April 28, 2013 at Daegwallyeong. On average, the LF occurred in Korea between March 17 (at Wando) and May 10 (at Daegwallyeong). Positive correlations were found between LFD and altitude and latitude. Additionally, interannual variation of LFD showed a trend of progressively earlier dates at 32 of the 48 stations at which data were available. The historic data set consists of the following: 39 records of frosts during the Three-States Period (57 BC-998 AD): 34 records during the Goryeo Dynasty (998-1391), among which the latest record was in July of the lunar calendar: and 498 during the Joseon Dynasty (1392-1928) with one LF dated August 31, 1417 on the solar calendar. Regarding LFD from The Annals of the Joseon Dynasty, April has 11 records, May has 55, June has 46, July has 21, and August has 5 LFD records. Various meteorological causes of the latest LF were then established. Firstly, a cold and humid north-easterly current that originates from high latitudes of more than 50°N and passes through the East Sea is considered one of the dominant causes of LF. Secondly, strong radiative cooling under clear skies is suspected as another important cause. Thirdly, a specific pressure pattern, called the 'inverted-S contour' or 'North High and South Low (NHSL) pattern' was found to be a favorable condition for LF. Finally the latest LF was not found to be related to monthly or longerterm cold climate, but are instead linked to the abrupt development of a strong ridge over inland Asia and the unusual southward movement of the tall polar cyclone over the North Pacific Ocean.
The weather charts made at November 1, 1905 that were supposed to be the first daily weather char... more The weather charts made at November 1, 1905 that were supposed to be the first daily weather chart in Korea were found and the contents of them were described and investigated. They were consisted of three sheets of paper. The first sheet consists of 2 kinds of weather charts. The second one does 6 kinds, and the third one is a table where 51 stations' records are in it. The diagnosing method and the historical background of the charts were explained. Although it is slim, the possibilities of the other earlier charts than these are explained also.
ABSTRACT Heat stress accumulates in the human body when a person is exposed to a thermal conditio... more ABSTRACT Heat stress accumulates in the human body when a person is exposed to a thermal condition for a long time. Considering this fact, we have defined the accumulated heat stress (AH) and have developed the accumulated heat stress index (AHI) to quantify the strength of heat stress. AH represents the heat stress accumulated in a 72-h period calculated by the use of a time-weighted function, and the AHI is a standardized index developed by the use of an equiprobability transformation (from a fitted Weibull distribution to the standard normal distribution). To verify the advantage offered by the AHI, it was compared with four thermal indices the humidex, the heat index, the wet-bulb globe temperature, and the perceived temperature used by national governments. AH and the AHI were found to provide better detection of thermal danger and were more useful than other indices. In particular, AH and the AHI detect deaths that were caused not only by extremely hot and humid weather, but also by the persistence of moderately hot and humid weather (for example, consecutive daily maximum temperatures of 28-32 °C), which the other indices fail to detect.
In this study, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12- and ... more In this study, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12- and 24- month Standardized Precipitation Indices (SPIs) were compared for drought monitoring data accumulated over 200-year period from 1807 to 2006 for Seoul, Korea. The results confirmed that the EDI was more efficient than the SPIs in assessing both short and long-term droughts.
ABSTRACT Springtime droughts in Korea were investigated to examine their characteristics and main... more ABSTRACT Springtime droughts in Korea were investigated to examine their characteristics and main causes using the Effective Drought Index (EDI). Data collected over a 96-year period (1910-2005) showed that May drought was milder than June drought and tended to continue into June. Regime shift analysis showed that 1931-1951 was a period of severe May drought. To analyze the general characteristics of May drought occurrence, we utilized empirical orthogonal function (EOF) analysis to select 12 drought years having a particular pattern of north-positive and south-negative (N+S-) anoma- lies for sea surface temperature in the North Pacific out of 21 occurrences of May drought in Korea over 56 years (1950-2005). The selected N+S- years were also found to have strong anomalies in themeteorological fields of temper- ature, geopotential height, and specific humidity due to strong meridional dipole patterns across 45°N in the North Pacific in both the low and mid-troposphere for several months before the droughts occurred. The development of this pattern is believed to cause a decreased Albedo due to a decreased sea ice extent in the Bering Sea and Okhotsk Sea (50°N-70°N, 140°E-160°W). Therefore, the cause of May drought is investigated as it accompanied decreases in the meridional temper- ature and pressure gradients and resulting decreases in the baroclinicity and precipitation in the mid-latitudes. In addition, an enhanced virtual easterly appeared both at the low and mid-troposphere between 35°N and 50°N in the wind anomaly field in the selected drought years. The wind begins in the central North Pacific, flows as a northeasterly into the Korean region, and outward as awesterly or northwesterly. Consequently, May drought in Korea was investigated and was found to be caused primarily by a decrease in precipitation due to the southward movement of a predominant storm track in May.
Monitoring and Predicting Agricultural Drought, 2005
South Korea (hereinafter referred to as Korea) lies in the middle latitudes of the Northern Hemis... more South Korea (hereinafter referred to as Korea) lies in the middle latitudes of the Northern Hemisphere. Until the 1960s, Korea was a typical agrarian country, with agriculture generating roughly half of its gross national product (GNP) and employing more than half of the labor force. Agriculture still plays an important role in the Korean national economy, but it accounts for a relatively much lower share of the GNP (5.3% in 1997) and engages much less of the population (11.0%). The agricultural share of the national economy is declining continuously. Farms in Korea, as in many other Asian countries, have traditionally been small. Average farm size has been growing slowly from 0.86 ha in 1960 to 1.39 ha in 2001, despite a significant reduction in the average number of persons per household engaged in farming—from 6.20 persons to 2.91 persons. As a result, agriculture has become more intensive. The country has four distinct seasons: summer, fall, winter, and spring. Summer and winter...
최근 30년간(1979-2008년) 한반도 주변(32-36 N, 122-132 E)에서 태풍이 약화될 때 한국에서 나타나는 시공간적 강수 특징을 분석하였다. 약화 유형은 온대... more 최근 30년간(1979-2008년) 한반도 주변(32-36 N, 122-132 E)에서 태풍이 약화될 때 한국에서 나타나는 시공간적 강수 특징을 분석하였다. 약화 유형은 온대저기압으로 약화되는 태풍(Weakened to Extratropical Cyclone, WEC)과 열대성 저압부로 약화되는 태풍(Weakened to Tropical Depression, WTD)으로 구분하였다. WEC의 경우, 강수량은 전국에 걸쳐 골고루 분포하였으며 남해안에서 가장 많았다. WTD의 경우, 강수량은 남해안에서 가장 많았지만 중부 및 내륙지역은 적었다. 두 경우의 강수량 차이는 Region 2(전라남도, 경상남도, 경상북도 남동부 지역, 제주도)에서는 거의 없었으며, Region 1(중부지방, 전라북도, 경상북도 내륙)에서는 WTD보다 WEC일 때 강수량이 더 많았다. 태풍이 한반도로 접근 할 때 WEC의 경우 태풍의 북서쪽에는 상층의 발달된 잠재소용돌이도와 하층의 온도골이 위치하고 있었으며, 태풍의 북동쪽에는 상층 제트 및 강한 상층 발산역이 위치하였다. 이는 태풍 전면에 경압교란과 비단열 과정을 발달시켰고 이로 인해 강수영역이 넓게 형성된 것으로 추측되었다. 그러나 WTD의 경우에서는 강한 잠재소용돌이도나 온도골, 상층제트가 태풍 주변에 나타나지 않았으며, 이로 인해 강수영역이 좁게 형성되었다.
Bangladesh, located in the Bay of Bengal, is a developing nation that is prone to devastating flo... more Bangladesh, located in the Bay of Bengal, is a developing nation that is prone to devastating flood events that cause loss of lives and several other forms of humanatarian disasters. Identifying, developing and validating new scientific techniques that can be used for flood-risk warning and regular monitoring, including flood risk mitigation and adaptation, can help reduce the catastrophic effect of floods in Bangladesh and other developing countries. In this study, a daily Flood Index (I F ) based on daily effective precipitation (P E ) is utilized for quantifying floods for two cites in Bangladesh: Dhaka (23.7°N, 90.38°E) and Bogra (24.51°N; 89.22°E), where flooding is a common phenomenon. Based on total daily precipitation (P) data, in this study the I F is determined by calculating the P E using an exponentially decaying time-reduction function, which considers the gradual depletion of water resources over time. P E per day is normalized and compared with the average and standard deviation of yearly maximums, within the considered hydrological period. The start of a flood event is identified for I F ≥ 0. Subsequently, the I F severity (I acc F ) as consecutively positive I F , duration (D F ) as number of days with positive I F , and peak danger (I max F ) as maximum I F are estimated for identified flood events, using the run-sum theory. The analysis carried out has accurately identified historical flood events at Dhaka station in 1984 and 2007 as having the largest I acc F value (i.e., greatest severity). Flood severity (I acc F ) and peak danger (I max F ) parameters have been verified by accumulated precipitation corresponding to the same period. For Bogra station, the 1998 and 1979 events were found to be the most intense. Seasonality analysis of the flood index shows most floods happened during the summer monsoon, although for the Dhaka station, flood events occurred between early June and November, and in Bogra, from late June to October. A rational study of effective precipitation provides a useful severity and danger indicator. The results indicate the practicality of daily I F for flood-risk assessments where the severity, peak danger, and duration need to be considered as a unified index for flood-risk monitoring. The proposed daily flood index can be useful for hydrologists for the purpose of daily operational flood monitoring in high flood-risk nations.
Asia-Pacific Journal of Atmospheric Sciences, 2016
This study aims to improve the forecasting skill for freezing precipitation. A total of 102 freez... more 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.
The spatiotemporal distributions of latest frost dates (LFDs) on the Korean Peninsula and the atm... more The spatiotemporal distributions of latest frost dates (LFDs) on the Korean Peninsula and the atmospheric circulation patterns that resulted in the latest frosts (LFs) were investigated through the use of historical records and modern weather observation data. During the modern observation period since 1904, the most recent record of LF was April 28, 2013 at Daegwallyeong. On average, the LF occurred in Korea between March 17 (at Wando) and May 10 (at Daegwallyeong). Positive correlations were found between LFD and altitude and latitude. Additionally, interannual variation of LFD showed a trend of progressively earlier dates at 32 of the 48 stations at which data were available. The historic data set consists of the following: 39 records of frosts during the Three-States Period (57 BC-998 AD): 34 records during the Goryeo Dynasty (998-1391), among which the latest record was in July of the lunar calendar: and 498 during the Joseon Dynasty (1392-1928) with one LF dated August 31, 1417 on the solar calendar. Regarding LFD from The Annals of the Joseon Dynasty, April has 11 records, May has 55, June has 46, July has 21, and August has 5 LFD records. Various meteorological causes of the latest LF were then established. Firstly, a cold and humid north-easterly current that originates from high latitudes of more than 50°N and passes through the East Sea is considered one of the dominant causes of LF. Secondly, strong radiative cooling under clear skies is suspected as another important cause. Thirdly, a specific pressure pattern, called the 'inverted-S contour' or 'North High and South Low (NHSL) pattern' was found to be a favorable condition for LF. Finally the latest LF was not found to be related to monthly or longerterm cold climate, but are instead linked to the abrupt development of a strong ridge over inland Asia and the unusual southward movement of the tall polar cyclone over the North Pacific Ocean.
The weather charts made at November 1, 1905 that were supposed to be the first daily weather char... more The weather charts made at November 1, 1905 that were supposed to be the first daily weather chart in Korea were found and the contents of them were described and investigated. They were consisted of three sheets of paper. The first sheet consists of 2 kinds of weather charts. The second one does 6 kinds, and the third one is a table where 51 stations' records are in it. The diagnosing method and the historical background of the charts were explained. Although it is slim, the possibilities of the other earlier charts than these are explained also.
ABSTRACT Heat stress accumulates in the human body when a person is exposed to a thermal conditio... more ABSTRACT Heat stress accumulates in the human body when a person is exposed to a thermal condition for a long time. Considering this fact, we have defined the accumulated heat stress (AH) and have developed the accumulated heat stress index (AHI) to quantify the strength of heat stress. AH represents the heat stress accumulated in a 72-h period calculated by the use of a time-weighted function, and the AHI is a standardized index developed by the use of an equiprobability transformation (from a fitted Weibull distribution to the standard normal distribution). To verify the advantage offered by the AHI, it was compared with four thermal indices the humidex, the heat index, the wet-bulb globe temperature, and the perceived temperature used by national governments. AH and the AHI were found to provide better detection of thermal danger and were more useful than other indices. In particular, AH and the AHI detect deaths that were caused not only by extremely hot and humid weather, but also by the persistence of moderately hot and humid weather (for example, consecutive daily maximum temperatures of 28-32 °C), which the other indices fail to detect.
In this study, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12- and ... more In this study, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12- and 24- month Standardized Precipitation Indices (SPIs) were compared for drought monitoring data accumulated over 200-year period from 1807 to 2006 for Seoul, Korea. The results confirmed that the EDI was more efficient than the SPIs in assessing both short and long-term droughts.
ABSTRACT Springtime droughts in Korea were investigated to examine their characteristics and main... more ABSTRACT Springtime droughts in Korea were investigated to examine their characteristics and main causes using the Effective Drought Index (EDI). Data collected over a 96-year period (1910-2005) showed that May drought was milder than June drought and tended to continue into June. Regime shift analysis showed that 1931-1951 was a period of severe May drought. To analyze the general characteristics of May drought occurrence, we utilized empirical orthogonal function (EOF) analysis to select 12 drought years having a particular pattern of north-positive and south-negative (N+S-) anoma- lies for sea surface temperature in the North Pacific out of 21 occurrences of May drought in Korea over 56 years (1950-2005). The selected N+S- years were also found to have strong anomalies in themeteorological fields of temper- ature, geopotential height, and specific humidity due to strong meridional dipole patterns across 45°N in the North Pacific in both the low and mid-troposphere for several months before the droughts occurred. The development of this pattern is believed to cause a decreased Albedo due to a decreased sea ice extent in the Bering Sea and Okhotsk Sea (50°N-70°N, 140°E-160°W). Therefore, the cause of May drought is investigated as it accompanied decreases in the meridional temper- ature and pressure gradients and resulting decreases in the baroclinicity and precipitation in the mid-latitudes. In addition, an enhanced virtual easterly appeared both at the low and mid-troposphere between 35°N and 50°N in the wind anomaly field in the selected drought years. The wind begins in the central North Pacific, flows as a northeasterly into the Korean region, and outward as awesterly or northwesterly. Consequently, May drought in Korea was investigated and was found to be caused primarily by a decrease in precipitation due to the southward movement of a predominant storm track in May.
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