경포호에서 수 질변수들의 장기적인 변화

곽성진,발데브,최광순,허우명 한국하천호수학회 2015 생태와 환경 Vol.48 No.2

경포호에서 수질 변수들의 장기적인 경향을 파악하기 위하여 1998년부터 2013년까지 매년 3월부터 11월까지 2개월에 1회씩 3개 지점에서 조사된 15가지 수질변수들과 강우량자료를 이용하였으며, Mann-Kendall test, Sen’s slope estimator 및 linear regression을 적용 분석하였다. 계절 변화 분석에는 Mann-Kendall test 및 Sen’s slope estimator만 이용하였다. 분석결과 염분, 투명도 및 영양염류 (총인, 용존무기인, 총질소, 질산성 질소, 암모니아성 질소)의 변수들만 통계학적으로 유의적인 경향을 보였다. 선형회귀 분석에서는 염분 (표층과 심층의 전 지점)과 투명도 (지점 1)만이 통계학적으로 유의적인 증가 경향을 나타냈으나, 비모수법에 의한 분석에서는 염분과 투명도 모두 전 지점에서 통계학적으로 유의적인 증가 경향을 보였다. 통계학적으로 유의적인 감소 경향을 보인 수질변수들은 선형회귀 분석에서는 용존산소 (표층 지점 1, 심층 지점 2와 3), 총인(지점 1과 2), 용존무기인, 총질소, 질산성 질소 및 암모니아성 질소, 비모수법에 의한 분석에서는 용존산소 (심층 전 지점), 총인, 용존무기인, 총질소, 질산성 질소 및 암모니아성 질소였다. 계절적인 경향을 분석한 결과 봄에는 염분, 탁도, 투명도 및 부유물질 (SS), 여름에는 염분, 투명도, 질산성 질소 및 부유물질, 가을에는 수온, 염분, 투명도 및 부유물질 만이 증가하는 경향을 보였으며 이들 변수들이 계절에 따라 다소 차이를 보이는 것으로 나타났다. 특히 봄과 여름에 비해서 가을철에 Mann-Kendall test 및 Sen’s Slope estimator에 의해 유의적인 경향을 나타낸 수질변수들이 많았다. 가장 강한 증가 경향을 보인 것은 염분이었으며 봄보다는 여름과 가을에 뚜렷하였다. 투명도도 염분과 유사한 특성을 보였다. 강우량은 조사기간 동안 전체적으로 감소하는 경향을 보였다. 경포호에서 영양염류의 유의적인 감소경향은 그동안 강릉시에서 추진해온 석호 복원사업 및 해수유통 (수중 보 철거) 등과 관련이 있는 것으로 판단되나 정확한 원인 규명을 위해서는 보다 면밀한 조사가 수반되어야 할 것으로 사료된다. In order to identify long-term trends of water quality parameters in Lake Kyeongpo, Mann-Kendall test, Sen’s slope estimator and linear regression were applied on data, with 15 parameters from three different sites and rainfall, monitored once in every two months from March to November during 1998~2013. Seasonal variation analysis only used Mann-Kendall test and Sen’s slope estimator. Analysis result showed that salinity, transparency and nutrient variables (total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen, ammonia nitrogen) were only parameters having statistically significant trend. In linear regression analysis, salinity (surface and bottom layer of all sites) and transparency (only at site 1), were figured out with statistically significant increasing trend, while in non-parametric statistical method, salinity and transparency in all sites (surface, middle, deep) were figured out with statistically significant increasing trend. Water quality parameters showing statistically significant decreasing trends were dissolved oxygen (surface layer of site 1 and bottom layer of sites 2 and 3), total phosphorus (sites 1 and 2), dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the linear regression analysis and, dissolved oxygen (bottom layer of all sites), total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the non-parametric method. Seasonal trend analysis result showed that salinity, turbidity, transparency and suspended solids in spring, salinity, transparency, nitrate nitrogen and suspended solids in summer and temperature, salinity, transparency and suspended solids in fall were the variables depending on the season with increasing trends. In general, rainfall during the research period showed decreasing trend. The significant reduction trends of nutrients in Lake Kyeongpo were believed to be related to lagoon restoration and water management project run by Gangneung city and under-water wear removal, but further detailed studies are needed to know the exact causes.

Spatio-temporal trend and change point detection of winter temperature of North Bengal, India

Jayanta Das,Tapash Mandal,Piu Saha 대한공간정보학회 2019 Spatial Information Research Vol.27 No.4

The trend of temperature and homogeneity are the most significant issue for climate change allied research. This research aims to identify the long-term trend and change point detection of winter maximum (tmax), minimum (tmin) and average (tmean) temperature of six meteorological stations of North Bengal, India using 102 years’ time series data (1915–2016). To detect the monotonic trend and the rate of change, non-parametric Mann–Kendall (MK) test and Sen’s slope estimator were used. Homogeneity of winter temperature was studied using Buishand’s range test (B test) and Pettit’s test (P test). From the results, it was observed that most of the stations were showed significant (P\0.05) warming trend in winter season. The rate of increasing was highest at station English Bazar in the month of December. On the other hand, significant changed of winter tmax and tmean occurred in around 1959 and 1952 respectively, while for tmin it was quite late, occurred in the year 1988. The populations of North Bengal who are dependent on temperature- related primary economic activities are getting benefitted from this study. In addition, these analyses will be helpful for policymakers and scientist to focus on microlevel planning and sustainable Rabi crops management in this region.

21년간 한국의 서리발생 시⋅공간 분포 특성과 경향

조은수,김해민,신주영,김규랑,이용희,지준범 한국농림기상학회 2022 한국농림기상학회지 Vol.24 No.2

In order to actively prepare to frost damage that occurs in the process of growing crops, the spatial and temporal distribution of frost occurrence in South Korea was derived using frost observation data from 20 regions over the past 21 years (2000∼2020). The main products are the number of frost days, first frost day, and last frost day by region. And the climatic trends of these results were identified by performing the Mann-Kendall trend test and Sen’s slope estimator. In South Korea, a lot of frost occurs in the inland area to the west of the Taebaek and Sobaek Mountains. Relatively closer to the coastal area, the number of frost days is small, the first frost day is slow, and the last frost day is early. The east coast region has fewer frost days, the first frost day is later, and the last frost day is earlier than the west coast region. The southern sea, the southeastern sea region, and the island region rarely experience frost. As a result of the annual time series trend analysis, although South Korea is a country where climate warming is progressing, there was no trend in reducing the number of frost days and slowing the first frost day, and it was found that the last frost day is delayed by 0.5 days per year. 농작물 생육 과정에서 서리에 의한 동상해 피해에 능동적으로 대비하기 위해, 지난 21년간(2000∼2020) 20개 지역의 서리관측 자료를 이용하여 한국 서리발생의 시공간적 분포 특성을 살폈다. 지역별 서리분포 특성은 서리일수, 첫 서리일, 끝 서리일로 표현하였다. 그리고 이러한 결과의 기후 경향은 Mann-Kendall trend test와 Sen’s slope estimator를 수행하여 확인하였다. 한국에서 대부분의 서리는 태백산맥과 소백산맥 서쪽 내륙지방에서 발생한다. 상대적으로 해안지역에 가까울수록 서리 발생일이 적고 첫서리일이 느리며 끝 서리일이 빠르다. 동해안지역은 서해안지역보다 서리일수가 적고 첫서리일이 느리며 끝서리일이 빠르다. 남해, 남동해, 도서지역은 거의 서리가 발생하지 않는다. 연간 시계열 추이 분석결과 한국은 기후온난화가 진행됨에도 불구하고, 서리일수가 줄어들거나 첫서리일이 늦춰지는 경향은 나타나지 않았으며, 끝서리일은 1년에 0.5일씩 늦춰지는 것으로 나타났다.

도암호에서 하절기 수질의 장기적인 경향

곽성진,발데브,이창근,허우명 한국하천호수학회(구 한국육수학회) 2013 생태와 환경 Vol.46 No.1

In the summer season (June~August) during the study period of Lake Doam, average concentrations of major water quality parameters, COD, SS, TN, and TP were 4.0, 16.2, 3.129 and 0.077 mg L-1, respectively, and Chl-a was 11.8 mg m-3. The result has indicated that Lake Doam was a meso-eutrotrophic lake. Lake Doam data from the summer season (June~August), precipitation from 2001 to 2012, and water quality (COD, SS, TN, TP, Chl-a etc.) of seven years (2001, 2002, 2004 and 2009~2012), were statistically analyzed for long-term trends by Mann-Kendall test and Sen`s slope estimator methods. The statistical results showed that precipitation, SD, COD, TN, NO3-N, NH3-N and Chl-a had decreasing trends, and EC, turbidity, SS, TP and DIP had increasing trends. Suspended solids and total phosphorus were directly affected by precipitation. In the case of suspended solids, more aggressive and constructive plans need to be implemented than the current turbidity reduction project to achieve the targeted water quality (5 mg L-1 of SS) in Lake Doam. In particular, we need to specify a project that considers the steep topographic characteristics of high, land farming areas and precipitation conditions of the Lake Doam watershed, which can increase the efficiency of a turbidity reduction project.

경포호에서 수질변수들의 장기적인 변화

곽성진 ( Sungjin Kwak ),발데브 ( Bal Dev Bhattrai ),최광순 ( Kwansoon Choi ),허우명 ( Woomyung Heo ) 한국하천호수학회(구 한국육수학회) 2015 생태와 환경 Vol.48 No.2

In order to identify long-term trends of water quality parameters in Lake Kyeongpo, Mann- Kendall test, Sen``s slope estimator and linear regression were applied on data, with 15 parameters from three different sites and rainfall, monitored once in every two months from March to November during 1998~2013. Seasonal variation analysis only used Mann-Kendall test and Sen``s slope estimator. Analysis result showed that salinity, transparency and nutrient variables (total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen, ammonia nitrogen) were only parameters having statistically significant trend. In linear regression analysis, salinity (surface and bottom layer of all sites) and transparency (only at site 1), were figured out with statistically significant increasing trend, while in non-parametric statistical method, salinity and transparency in all sites (surface, middle, deep) were figured out with statistically significant increasing trend. Water quality parameters showing statistically significant decreasing trends were dissolved oxygen (surface layer of site 1 and bottom layer of sites 2 and 3), total phosphorus (sites 1 and 2), dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the linear regression analysis and, dissolved oxygen (bottom layer of all sites), total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the non-parametric method. Seasonal trend analysis result showed that salinity, turbidity, transparency and suspended solids in spring, salinity, transparency, nitrate nitrogen and suspended solids in summer and temperature, salinity, transparency and suspended solids in fall were the variables depending on the season with increasing trends. In general, rainfall during the research period showed decreasing trend. The significant reduction trends of nutrients in Lake Kyeongpo were believed to be related to lagoon restoration and water management project run by Gangneung city and under-water wear removal, but further detailed studies are needed to know the exact causes.

Exploring spatial and temporal trends of diurnal temperature range in the region of the Subarnarekha river basin India

Shree Shashank,Kumar Manoj,Singh Ajai 대한공간정보학회 2021 Spatial Information Research Vol.29 No.2

This study analyzed the spatial and temporal trends of diurnal temperature range (DTR) for 35-years (1983–2017) in the region of the Subarnarekha river basin of Jharkhand, India. The daily data of maximum temperature (Tmax) and minimum temperature (Tmin) were habituated to compute the DTR, whereas rainfall data is used to measure its relationship with DTR, on a monthly annual and seasonal basis. Mann–Kendall test and Sen’s slope method has been used to detect the increasing or decreasing trends in climatic data with their statistical significance. The annual mean DTR of the basin is 11.97 C With a maximum in pre-monsoon (16.36 C) and minimum in monsoon (6.94 C). A significant negative trend (- 0.31 C/decade) was observed in annual DTR over the basin. On a seasonal basis, all four seasons show a negative trend in DTR with the largest significant decreasing trend in the pre-monsoon season (- 0.49 C/decade). On an annual and seasonal basis, a significant negative correlation between DTR and rainfall is found, indicating that rainfall has a significant impact on the variation of DTR in this basin. A concomitant increase in rainfall might be one of the possible causes of the decreases in DTR in the basin.

Trend analysis of long-term climatic parameters in Dinhata of Koch Bihar district, West Bengal

Jayanta Das,Sudip Kumar Bhattacharya 대한공간정보학회 2018 Spatial Information Research Vol.26 No.3

The monthly, seasonal and annual trends for five climatic parameters, such as rainfall, rainy days, temperature, relative humidity and sunshine hours were analyzed for the period of 1980–2015. The objective of this study was to detect the long term trend of climatic parameters of the study area. The non-parametric Mann–Kendall test and Sen’s slope estimators methods were used to determine whether there was a positive or negative trend in weather data with their statistical significance. The study area is characterized by high rainfall, receives an annual average rainfall of 3005 ± 820 mm, with an inter-annual variation 27% but analysis of long-term trends in the annual rainfall indicates a decreasing trend (- 14.31 mm year-1) and annual rainy days also significantly decreased (- 0.63 days year-1). In terms of seasonal rainfall, the pre-monsoon and monsoon months exhibited non-significant declining trends, while post monsoon months marginally increased. The result showed significant (P\0.05) warming trend in annual minimum and mean temperature at the rate of 0.14 and 0.05 C year-1 respectively and also showed similar significant (P\0.05) increasing trend in summer (0.05 C year-1) and winter (0.07 C year-1) mean temperature. Decrease in maximum temperature during all the months except September and annual maximum temperature (- 0.04 C year-1) is evident. The study area is experiencing a significant increasing trend in maximum (0.36% year-1), minimum (0.52% year-1) and mean relative humidity (0.13% year-1), with a significant decreasing trend of sunshine hours in pre monsoon (- 0.03 h day-1), post monsoon (- 0.04 h day-1) and mean (- 0.03 h day-1).

Analysis of long-term seasonal and annual temperature trends in North Bengal, India

Pritha Datta,Soumik Das 대한공간정보학회 2019 Spatial Information Research Vol.27 No.4

In the recent past, scientific modeling of climatic elements, in particular, temperature data has attained considerable importance as it affects many aspects of the environment and also indicates a clear sign of climate change. The temperature warming is mainly associated with the increasing concentration of greenhouse gases triggered by the land use and land cover changes. In the last century, exploitation of forest resource, population influx, and expansion of agricultural land has changed the natural landscape of North Bengal to a great extent. Thus the present study intends to find out long-term changes in maximum and minimum temperature for six northern districts of the state of West Bengal, popularly known as North Bengal. The non-parametric Mann–Kendall test and Theil-Sen’s slope estimator reveals the presence of warming trends in both maximum and minimum temperature. Annual temperature is rising 0.006 C per year and 0.007 C per year at most of the districts for the maximum and minimum temperature respectively. However, the seasonal analysis of trend exposes that post-monsoon and winter temperature rise are predominantly contributing to the upward annual trend. The highest increasing trend in maximum and minimum temperature is observed at Malda (0.013 C per year) in the post-monsoon and winter season respectively. Except the post-monsoon season, the minimum temperature is rising rapidly than maximum temperature across the region. Additionally, Sequential Mann–Kendall test exhibits the periodic fluctuation of trends, which are more prominent in pre-monsoon and monsoon season.