Heavy Rainy Days Research Articles

Long-term change of wet and dry climatic conditions in the southwest karst area of China

Using the daily precipitation and temperature data at 153 stations in the karst area of Southwest China from 1959 to 2009, the long-term change characteristics of wet and dry climatic conditions are analyzed by the Mann–Kendall test. This study shows that: 1) the annual average temperature has increased at 88% of the stations with an average rate of +0.16°C/10-year. This increase rate is greater than +0.30°C/10-year in the southeastern, northeastern, and western parts of the study region. Very warm days and abnormally warm days were seen increased at 47% and 63% of the stations, respectively. Very cool days and abnormally cool days in a year have reduced at respectively 94% and 95% of the stations; 2) no clear change trend was found for average annual precipitation over the entire area as a whole, but regional and seasonal changes were quite obvious. The annual total precipitation has decreased by −22.5mm/10-year in the central part but increased by +8.9mm/10-year in the western part of the region, and summer and winter seemed to become wetter while spring and autumn became drier. Although the number of rainy days in a year has decreased at almost 53% of the total stations with an average rate of −3.9days/10-year over the entire area, the number of extremely heavy rainy days has increased by +0.2, +0.4 and +0.4days/10-year in the southern Sichuan Province, the central part of Yunnan Province, and the northeastern Hubei Province, respectively; and 3) the extreme drought became more serious. The consecutive dry days has increased significantly at nearly 46% of the stations, especially in the western Guangxi Autonomous Region, the southern Guizhou Province, and the eastern Chongqing Municipality. The extreme drought remained at a high frequency at the beginning of the 21st century. It has shifted gradually from the eastern and western parts to the south-central part which is characterized by medium-high rocky desertification. Hopefully findings from this study will help for a better understanding of the impacts to some eminent geological hazards such as rocky desertification, increased frequency of drought and storms, and landslides in recent years.

Trend analysis of rainfall and frequency of rainy days over Coimbatore

Rainfall is very crucial for the economic development, disaster management, hydrological planning for the country. In the context of climate change, it is pertinent to ascertain whether the characteristic of Indian rainfall is also changing. Using daily rainfall data for the period of 1907-2012 analysis were carried out, to find out the change in rainfall and frequency of rainfall intensity. Results indicated that the annual rainfall is not dependable. Contribution of NEM to the total rainfall is 50.3 percent which was followed by SWM (26.3%). Contribution of NEM during every 30 years of periods was constantly increasing and the increasing trend was statistically significant at 95% confidence level. Total number of rainy days (very light, light, moderate, rather heavy, heavy, very heavy rainy days) during the study period was 80.2 days, in which the frequency of very light rainy days (35.0 days) was highest followed by light (20.7 days) and moderate rainy days (20.8 days). Trend analysis was done for all categories of rainfall to find out the presence of increasing or decreasing trend. Total number of rainy days slightly gets decreasing in all the seasons except NEM where the rainy days are increasing but the changes were not statistically significant. The results showed that there is no change in long term of monthly, seasonal, annual rainfall and frequency of rainy days. Hence, it can be concluded that there is no climate change observed over Coimbatore.

The Recent Increasing Trends of Exceedance Rainfall Thresholds over the Korean Major Cities

본 연구에서는 전국의 8개 주요 도시지점 강우관측 자료를 대상으로 다양한 분류 기준을 적용하여 Quantile Regression (QR)에 의한 기준강수량 초과 강우의 선형추세분석과 Mann-Kendall, Sen 검정을 실시하였다. 분석결과 봄철과 여름철 강수의 뚜렷한 증가경향이 있으며, 가을철과 겨울철 강수는 감소하는 경향이 있음을 확인하였고, 폭우 사상은 최근 30년 평균 3.1~15% 증가 하였다. 또한, 연도별 발생강우의 Ranking에 따른 Top <TEX>$10^{th}$</TEX> 백분위 강수의 3IQR (inter quartile range)의 최근증가경향을 분석한 결과, 대부분 지점에서 강수의 증가경향을 확인하였으며, Quantile 90%의 평균 백분위 강수량은 43.5mm, 증가경향은 0.1412mm/yr, Quantile 99%의 평균 백분위 강수량은 68.0mm, 증가경향은 0.1314mm/yr로 분석되었다. 본 연구의 결과는 매년 발생한 연최대치계열에 대한 분석뿐만 아니라 기준값 이상의 수문 사상정보에 대한 반영과 최근 변화하는 기후의 증가경향을 반영한 수공구조물 설계의 기초자료로 활용이 가능할 것으로 사료된다. In this study, we analysed impacts of the recent increasing trend of exceedance rainfall thresholds for separation of data set and different research periods using Quantile Regression (QR) approach. And also we performed significant test for time series data using linear regression, Mann-Kendall test and Sen test over the Korean major 8-city. Spring and summer precipitation was tend to significant increase, fall and winter precipitation was tend to decrease, and heavy rainy days in last 30 years have increased from 3.1 to 15 percent average. In addition, according to the annual ranking of rainfall occurs Top <TEX>$10^{th}$</TEX> percentile of precipitation for 3IQR (inter quartile range) of the increasing trend, most of the precipitation at the point of increasing trend was confirmed. Quantile 90% percentile of the average rainfall 43.5mm, the increasing trend 0.1412mm/yr, Quantile 99% percentile of the average rainfall 68.0mm, the increasing trend in the 0.1314mm/yr were analyzed. The results can be used to analyze the recent increasing trend for the annual maximum value series information and the threshold extreme hydrologic information. And also can be used as a basis data for hydraulic structures design on reflect recent changes in climate characteristics.

A Study on Typhoon Impacts in the Nakdong River Basin Associated with Decaying Phases of Central-Pacific El Niño

본 연구에서는 중앙태평양 지역의 비정상적인 해수면 온도변화를 3가지 진화패턴(Prolonged-decaying, Abrupt-decaying, Symmetric-decaying)에 따라 분류하였으며, 이에 따른 한반도 영향 태풍을 중심으로 태풍의 발생지점 및 경로, 중심기압의 특성변화와 낙동강유역의 태풍 강우량 및 중호우사상의 발생빈도에 대한 특성변화를 분석하였다. 분석결과, Prolonged-decaying 해와 Symmetric-decaying 해의 경우, 낙동강 유역의 태풍에 의한 여름철 강우량 및 중호우사상의 발생빈도가 평년보다 크게 나타났다. 그러나, Abrupt-decaying 해의 경우, 태풍강우는 대체로 감소하는 패턴을 보이는 것으로 분석되었으며, 이는 태풍의 발생지점이 비교적 한반도에 근접하게 위치하며 태풍의 중심기압이 높고 태풍의 경로가 대체로 일본으로 이동하기 때문인 것으로 나타났다. 본 연구의 성과는 중앙태평양 엘니뇨의 진화패턴별 태풍활동특성 및 지역적 태풍강우 특성 분석을 통하여 침수피해를 저감하고 기후변화에 대비한 적응방안 수립에 유용한 기초자료로 활용될 수 있을 것으로 기대된다. This study classified abnormal sea surface temperature changes of the central pacific region according to three evolution patterns. Focusing on typhoons that affect the Korean Peninsula, the research analyzed typhoon's occurrence spot and track, change in the central pressure characteristics, and the characteristics of change in typhoon precipitation and the number of occurrences of heavy rainfall in the Nakdong River Basin. As a result of analysis, in case of prolonged-decaying years and symmetric-decaying years, typhoon-related summer rainfall and heavy rainy days appeared to be higher than long-term average. But in case of abrupt-decaying years, the pattern of general decrease appeared. This is because typhoon's occurrence spot is located comparatively near the Korean peninsula, typhoon's central pressure is high, and typhoon's route generally moves to Japan. As the outcome, this study is expected to reduce flood damage through analyzing the characteristics of typhoon's activity according to CP El Ni<TEX>$\tilde{n}$</TEX>o evolution patterns and the characteristics of local typhoon rainfall. In addition, it is expected to provide useful information for establishing adaptation and mitigation to climate change.

Projected changes in mean and extreme precipitation indices over India using PRECIS

The impact of global warming on the characteristics of mean and extremes of rainfall over India is investigated using a high resolution regional climate model PRECIS developed by Hadley Centre, UK. Five simulations of PRECIS made using the lateral boundary conditions from a suite of Perturbed Physics Ensembles (PPE) generated using Hadley Center Coupled Model (HadCM3) for Quantifying Uncertainty in Model Predictions (QUMP) project corresponding to IPCC A1B emission scenario have been analyzed here for this purpose. The projected changes depict seasonally dependent fine scale structure in response to the topographic forcing and changes in circulation, especially along the west coast and North East (NE) region of India towards the end of the 21st century i.e. 2080s (2071–2098). Analysis of the extreme precipitation indices indicates an increase in the intensity of rainfall on wet days towards 2080s under A1B scenario. Changes in extreme precipitation events and dry spells suggest not only shifts, but also a substantial increase in the spread of the precipitation distribution, with an increased probability of the occurrence of events conducive to both floods and droughts. The projected changes in various precipitation extremes show a large regional variability. Total rainfall on very heavy rainy days (R95p) is projected to increase by around 40–50% over the central parts of the country. The number of rainy days >10mm (R10) may increase by 10–20% over west coast, east central India and northeastern parts while over northwest and rain shadow region they may increase by 40–50%. The consecutive dry days (CDDs) may decrease by 10–20% over Indo-Gangetic plain, however over west coast there may not be any significant change. The CDDs are projected to rise by 10–20% over west central and peninsular India. The precipitation per wet day (SDII) may be more intense by 10–40% over the entire land mass, however there may not be any significant change over south peninsular India.

서로 다른 형태의 엘니뇨에 따른 한강유역의 여름철 강우량과 극치강우의 변동특성 분석

본 연구에서는 전형적인 엘니뇨와 새로운 형태의 엘니뇨 Modoki에 따른 한강유역의 여름철(6~9월) 강우량의 특성 변화를 분석하였다. 전형적인 엘니뇨 시기에는 대체로 여름철 강우량이 감소하였으며, 강우의 변동성도 비교적 크게 나타났다(CV=0.40). 반면에 엘니뇨 Modoki 시기에는 한강 대부분 유역에서 평년보다 강우가 증가하는 경향을 보였으며, 여름철 강우의 변동성은 작은 것으로 분석되었다(CV=0.23). 엘니뇨 Modoki 시기에는 한강 남부의 11개 중권역에서 통계적으로 유의한 강우의 증가를 보였고, 30mm/day와 50mm/day를 초과하는 중호우의 강우발생일은 각각 9.9일과 5.4일로 나타났으며, 전형적인 엘니뇨 시기보다 백분위 편차가 각각 17.74%, 50.94% 큰 것으로 분석되었다. 본 연구에서는 새로운 형태의 엘니뇨 Modoki가 전형적인 패턴의 엘니뇨보다 한강유역의 여름철 수자원 변동에 민감하게 영향을 주고 있음을 확인하였으며, 향후 수자원의 계절적 변동과 불확실성이 큰 지역에서 안정적인 수자원 확보를 위한 기초자료로 활용이 가능하리라 사료된다. This study investigated impacts of the two different types of El Ni<TEX>$\tilde{n}$</TEX>o on summer rainfall (June-September) in the Han River and its sub-basins. The patterns of rainfall anomalies show a remarkable difference between conventional El Ni<TEX>$\tilde{n}$</TEX>o and El Ni<TEX>$\tilde{n}$</TEX>o Modoki years. During conventional El Ni<TEX>$\tilde{n}$</TEX>o years, it was found that the Han River basins show decreases in the seasonal rainfall totals with high variations (CV=0.4). In contrast, during El Ni<TEX>$\tilde{n}$</TEX>o Modoki years, distinct positive anomalies appear in the Han River basin with a relatively small variation (CV=0.23). In addition, 11 out of 30 sub-basins show significant above-normal rainfall in southern part of the Han River Basin. For El Ni<TEX>$\tilde{n}$</TEX>o Modoki years, the number of heavy rainy days exceeding 30 mm/day and 50 mm/day were 9.9-day and 5.4-day, respectively. Consequently, this diagnostic study confirmed that El Ni<TEX>$\tilde{n}$</TEX>o Modoki has significant impacts on the variability of summer rainfall over the Han River Basin. We expect the results presented here provide useful information for the stability of the regional water supply system, especially for basins like the Han River Basin showing relatively high variability in seasonal rainfall.