Development of design storm hyetographs in hyper-arid and arid regions: case study of Sultanate of Oman

The temporal distribution of the design storm is an important input in hydrological models. This research aims to develop design storm profiles representative of arid and hyper-arid areas based on actual storm recordings. Two hundred thirty-six rainfall storms were collected from seventeen rainfall gauges that cover the coastal zone of Oman for the period from 1993 to 2007. Storms were classified into four categories according to their total durations. Design storm hyetographs were derived from raw rainfall records for all four categories using the Alternating Block Method (ABM) and were also computed by ABM applied on the Intensity-Duration-Frequency (IDF) curves. Both design storm profiles were compared and it was found that the ABM_IDF storm profiles were equivalent to the four ABM_Storms profiles from a practical point of view as they produce similar peak discharges. The storm profiles developed in the current research were also compared to the commonly used Soil Conservation Service (SCS) dimensionless distributions and the UK50 storm profiles. The results showed that the most conservative commonly used SCS type II and the UK50 summer profiles are not safe to be used in design purposes in arid and hyper arid regions, despite their wide utilization in many codes of practice in these regions. The study recommends using the newly developed dimensionless storm profiles derived from the actual records.     

Sensitivity analysis of runoff hydrographs due to temporal rainfall patterns in Makkah Al-Mukkramah region,Saudi Arabia

Runoff peak and volume in flood studies are estimated relying on temporal rainfall distribution from various storm patterns. Usually, SCS distributions types (I, II, III, IA) are commonly used. Using these distributions in runoff calculations assume that the in situ temporal rainfall pattern typically behaves as the one described by the SCS-type distribution, which is due to cyclonic frontal storms and actually developed in temperate environment. To what extent such assumption is valid in the arid environment? How much the impacts of rainfall temporal patterns are reflected in runoff volumes and peaks? The aim objectives of the current study are to answer the above two questions and clarify the validity of aforementioned assumption and exemplify such effect. Real rainfall data collected from rain gauges of Makkah Al-Mukkramah region over a period of more than 20 years are utilized. Temporal rainfall patterns and their parameters are deduced. Many hydrological simulations are performed and comparisons, in terms of runoff volume and peak flows, are made to show the effects of the common rainfall storm patterns and the developed rainfall storm patterns in the region based on the current study. Results indicate that major bursts of the design rainfall storm pattern are located in the first time of the storm period in the two quartiles which is mainly due to convective rainfall type in thunderstorms unlike the commonly used by SCS types relying on frontal cyclonic storms. Makkah Al-Mukkramah temporal rainfall pattern does not behave as the “typical pattern” assumed by SCS distributions that are deduced from different environments. The impacts of the temporal pattern reflected as an overestimate in the runoff peak reached to 68 %. The developed hyetographs and tables presented in the current study are recommended to enhance economical and rational design practice in watersheds of Makkah Al-Mukkramah region.     

Synoptic analysis of dust storm over Arabian Peninsula: a case study on February 28, 2009

Sand and dust storms are causing hazards and problems in aviation as well as the dangers and distresses they cause on living things. The low meteorological visibility, the presence of strong winds with gust, and the transport of dust and sand particles by the wind are dangerous on landing and departure of aircrafts, and even on planes that are parked. The main aim of the study is to examine the meteorological conditions causing the dust storm that took place in the Arabian Peninsula on February 28, 2009, and to determine the source of dust caused dust storm, sand storm, blown sand, and blown dust at the airports. Within the scope of the study, aviation routine weather report (METAR) and aviation selected special weather report (SPECI) reports have been assessed at many airports over Arabian Peninsula (AP), the northern part of the AP and North Africa. As model outputs; NCEP–DOE Reanalysis 2 data, BSC–DREAM8B, and HYSPLIT model were used. In the satellite images; METEOSAT MSG dust RGB images, MODIS, and Kalpana-1 data were used. According to obtained results, dust storms were detected in Bahrain, Kuwait, Saudi Arabia, and United Arab Emirates (UAE). At Al-Ahsa Airport in Saudi Arabia, the lowest visibility measured on February 28, 2009, dropping to 200 m, which was dominated by blowing sand. The source region of the dust observed at Dubai Airport in UAE is the eastern regions of the Rub’al Khali Desert located between Saudi Arabia, Oman, and UAE.     

Assessing the impacts of rainfall intensity and urbanization on storm runoff in an arid catchment

In the past few decades, rapid urbanization has occurred in many regions of the Kingdom of Saudi Arabia due to increasing population and urban development. Additionally, the effects of global warming on rainfall characteristics have been observed. This rapid change in urbanization and climate change has cause significant changes in the nature of land surfaces and rainfall patterns, which affect the runoff process and the amount of surface runoff during floods. This study investigated the effect of urbanization and rainfall intensity for Hafr Al-Batin watershed located in Saudi Arabia. For this purpose, a hydrologic model, HEC-HMS, was adopted to simulate the flow of different rainfall intesities and urbanization levels. Simulated results showed that for a 100-year storm, a 24-h duration, and an urbanization level of 80%, the peak flow was 213% higher than the estimated current peak and the runoff volume was 112% higher than the current runoff volume. These results show a strong linear correlation between the level of urbanization and both peak discharge and runoff volume. Furthermore, the results indicate that for short return periods, the peak flow is more sensitive to the level of urbanization compared to long periods.     

Inconsistency in rainfall characteristics estimated from records of different rain gauges

The goal of this work is to assess the effect of utilizing different types of tipping bucket rain gauges in investigating rainfall characteristics. A dual tipping bucket (TB) rain gauge station is installed in the upper catchment of Numan basin in Saudi Arabia. The main difference between the two gauges is that the Hydrological Services (HS) gauge is equipped with a siphon tube which reduces undercatchment particularly during heavy rainfall. Records of both gauges for the period 2006 to 2013 are collected, analyzed, and compared, focusing on the characteristics of rainfall events as well as rainfall temporal variability. The HS gauge recorded higher values of total rainfall depth compared to the Texas Electronics (TEMM) gauge. For the individual storms as well as the 5-min rainfall, HS gauge also reported higher mean rainfall depths. Regarding temporal characteristics of reported rainfall, no significant variations are observed between the values of storm duration of the two gauges. The TEMM gauge has the advantage of recoding more storms with depth less than 1 mm. The current study suggests the use of a corrective factor for rainfall record of the TEMM gauge.     

设计暴雨雨型对城市内涝影响数值模拟

为分析设计暴雨雨型对城市内涝的影响,应用耦合了水文和水动力过程的数值模型,以陕西省西咸新区为研究区域,对不同重现期及峰值比例设计暴雨条件下的内涝过程进行模拟,并对内涝积水总量、不同积水深度内涝面积等量值进行对比分析。结果表明:设计暴雨重现期短于20年时,峰值比例较小的设计暴雨内涝积水总量较大,而重现期长于20年时,规律相反;除2年一遇设计暴雨外,峰值比例较大的设计暴雨致涝总面积较大,但其中影响严重的Ⅳ级致涝面积较小;设计暴雨峰值比例越小,重现期越长,积水总量峰值时刻相对于暴雨峰值时刻的迟滞时间越长。揭示了暴雨雨型与内涝积水程度的量化规律,对更合理地开展城市雨洪管理工作具有指导意义。     

The influence of dust storms on solar radiation data,aerosol properties and meteorological variables in Central Arabian Peninsula

Dust storms are one of the natural sources for aerosol particles, especially in desert regions. The arid and semi-arid regions around Saudi Arabia are some of the most important sources of global dust. In this paper, we have quantitatively studied the influence of several dust storms on solar radiation components and meteorological variables. Global, direct and diffuse solar radiation data, in addition to measurements of relative humidity, air temperature, precipitable water vapor, aerosol optical depth and an Angstrom exponent for the period between 1999 and 2002, were used for the purpose of this study. During this period, 34 dusty events were selected, and their effects on these parameters were characterized. We have found that, dust storms significantly increase aerosol optical depth and the diffuse radiation and decrease the global and direct solar radiation components and Angstrom exponent. On the other hand, dusty events affect air temperature, relative humidity and precipitable water vapor differently. They intensify these variables in some events and reduce them in others. We have found that the amount of changes in these variables varies from one event to another. Several possibilities, such as the source of the dust storm and the season in which it occurred, have been suggested to explain these variations.     

中国降雨过程时程分型特征

为研究降雨过程雨强随历时的变化关系,利用中国14个气象站近40年逐分钟降雨资料,采用动态K均值聚类法并根据雨峰在降雨过程中出现的位置,将中国10256次降雨过程分为4种类型,即降雨前期集中型（Ⅰ型）、降雨中期集中型（Ⅱ型）、降雨后期集中型（Ⅲ型）和降雨均匀分布型（IV型）。结果表明:中国Ⅰ型降雨出现频次最高,占47.1%;Ⅱ型次之,占21.2%;Ⅲ型和IV型出现频次相当,分别占15.3%和16.4%。夏季Ⅰ型降雨发生频次占绝对优势,为夏季总降水过程的52.2%;冬季各类雨型发生频次相差不大。Ⅰ型多为短历时高强度降雨,而IV型多为长历时低强度降雨,Ⅱ型和Ⅲ型居中。历时越短时,Ⅰ型降雨的比重越大;随着降雨历时的增加,Ⅰ型降雨的比重明显下降,IV型降雨的比重增加。     

Adaptation of climate variability/extreme in arid environment of the Arabian peninsula by rainwater harvesting and management

Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. The rainfall and temperature records of the Saudi meteorological data for more than three decades were analyzed for policy suggestions in water sectors based on the changing rainfall patterns. The trends in the annual aridity and rain indices were also examined to define the changing climate conditions and for determining the dry months in different cities of the Kingdom. An increased annual and maximum rainfall was observed for six cities while a decreasing trend in both annual and maximum rainfall was observed for the same number of cities highlighting the variability of rainfall in the whole region. An increasing maximum rainfall with decreasing annual rainfall was observed for the rest of the cities signifying the more extreme rainfall evens and resulting floods of short durations. The changing rainfall trends were also observed for different months during 31 years of the recorded period in addition to the varying climate pattern for different cities within the same district. Finally, these preliminary assessments of any systematic changes in view of the increased rain intensities and extreme climate events are viewed to demonstrate the value rainwater harvesting and management as a local adaptation to the climate variability and extreme in the Kingdom.     

Regional modeling of dust storm of February 8, 2015 in the southwest of Iran

According to World Meteorological Organization report in 2015, the southwest of Iran has become one of the dust sources in the region. And the objective of this research is to study the dust storms originating in this region. For this purpose, based on the weather data of 14 stations, the dust storms of the region were investigated, and the dust storm of February 7, 2015, was selected due to its very high concentration of dust particles (66 times the normal values). For the analysis of source areas and storm paths, the FNL data was used. The regional models of Navy Aerosol Analysis and Prediction System (NAAPS), Barcelona Supercomputing Centre-Dust Regional Atmospheric Model 8b (DREAM 8b), Non-hydrostatic Multiscale Model Barcelona Supercomputing Center (NMMB/BSC), and hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) were used to study and analyze the selected storm. The results showed that the dust event in February 8, 2016, has been the result of the polar front jet stream (PJF) caused by western immigrant system that had been over the Sahara in Africa, the deserts of Iraq, Syria, Saudi Arabia, and finally southwest of Iran in making the extreme dust event. According to the Moderate Resolution Imaging Spectroradiometer data and point models of NAAPS, optical depth was very high. The DREAM 8b and NMMB/BSC models confirmed the impact of the local factors and closeness to the dust source regions. The backward tracking of the model with the HYSPLIT model showed three tracks transporting the dust particles to the region. This software also showed that the dust particles occupied an atmospheric tunnel of 1.5 km in diameter.     

基于随机暴雨移置方法的城市设计暴雨分析

城市地区暴雨洪灾发生频繁，合理计算设计暴雨是解决城市洪涝的重要前提。采用随机暴雨移置方法（Stochastic Storm Transposition，SST），设定暴雨移置区并提取出暴雨目录，通过区域性概率重采样与暴雨空间变换相结合的方式进行降雨频率分析，估计本地化的极端暴雨频率。以上海地区为例，研究发现暴雨移置区内暴雨分布具有空间异质性，暴雨随机移置概率不均，计算得到的设计暴雨方案包含了降雨时空分布信息，在不同重现期下设计暴雨的时空结构存在变异性，说明传统方法中采用的简化雨型和均一化空间分布假设会增加设计暴雨的不确定性。     

基于随机暴雨移置方法的城市设计暴雨分析

城市地区暴雨洪灾发生频繁，合理计算设计暴雨是解决城市洪涝的重要前提。采用随机暴雨移置方法（Stochastic Storm Transposition，SST），设定暴雨移置区并提取出暴雨目录，通过区域性概率重采样与暴雨空间变换相结合的方式进行降雨频率分析，估计本地化的极端暴雨频率。以上海地区为例，研究发现暴雨移置区内暴雨分布具有空间异质性，暴雨随机移置概率不均，计算得到的设计暴雨方案包含了降雨时空分布信息，在不同重现期下设计暴雨的时空结构存在变异性，说明传统方法中采用的简化雨型和均一化空间分布假设会增加设计暴雨的不确定性。     

Rainfall threshold determination for flash flood warning in mountainous catchments with consideration of antecedent soil moisture and rainfall pattern

Flash flood disaster is a prominent issue threatening public safety and social development throughout the world, especially in mountainous regions. Rainfall threshold is a widely accepted alternative to hydrological forecasting for flash flood warning due to the short response time and limited observations of flash flood events. However, determination of rainfall threshold is still very complicated due to multiple impact factors, particular for antecedent soil moisture and rainfall patterns. In this study, hydrological simulation approach (i.e., China Flash Flood-Hydrological Modeling System: CNFF-HMS) was adopted to capture the flash flood processes. Multiple scenarios were further designed with consideration of antecedent soil moisture and rainfall temporal patterns to determine the possible assemble of rainfall thresholds by driving the CNFF-HMS. Moreover, their effects on rainfall thresholds were investigated. Three mountainous catchments (Zhong, Balisi and Yu villages) in southern China were selected for case study. Results showed that the model performance of CNFF-HMS was very satisfactory for flash flood simulations in all these catchments, especially for multimodal flood events. Specifically, the relative errors of runoff and peak flow were within?±?20%, the error of time to peak flow was within?±?2 h and the Nash–Sutcliffe efficiency was greater than 0.90 for over 90% of the flash flood events. The rainfall thresholds varied between 93 and 334 mm at Zhong village, between 77 and 246 mm at Balisi village and between 111 and 420 mm at Yu village. Both antecedent soil moistures and rainfall temporal pattern significantly affected the variations of rainfall threshold. Rainfall threshold decreased by 8–38 and 0–42% as soil saturation increased from 0.20 to 0.50 and from 0.20 to 0.80, respectively. The effect of rainfall threshold was the minimum for the decreasing hyetograph (advanced pattern) and the maximum for the increasing hyetograph (delayed pattern), while it was similar for the design hyetograph and triangular hyetograph (intermediate patterns). Moreover, rainfall thresholds with short time spans were more suitable for early flood warning, especially in small rural catchments with humid climatic characteristics. This study was expected to provide insights into flash flood disaster forecasting and early warning in mountainous regions, and scientific references for the implementation of flash flood disaster prevention in China.     

地区线性矩法在太湖流域暴雨频率分析中的应用

介绍了基于水文气象途径的地区线性矩法的概念,通过基于次序统计量的线性矩进行参数估计与基于水文气象一致区的地区分析法相结合,以太湖流域1d时段的年极值降雨资料为例,进行暴雨频率分析。应用水文气象一致区的判别准则,将太湖流域划分为8个水文气象一致区;综合考虑三种拟合优度检测方法,选择1~8区的最优分布线型分别为:GEV、GLO、GEV、GEV、GNO、GNO、GEV、GNO;根据地区分析法原理,估算各雨量站的暴雨频率设计值。分析表明:太湖流域各重现期下的年极值降雨空间分布形态基本一致,西南山区是太湖流域的暴雨高风险区,应该在地区防洪规划中引起重视。结果表明:地区线性矩法具有很高的学术和实用价值,建议在全国范围内推广,作为防洪规划的顶层设计和基础工作,以满足工程防洪设计、地区防洪规划、山洪预警和城市防涝防洪规划等方面的需求。     

Quantitative indices for medical & personnel facilities

The status of medical facilities and personnel in the Kingdom of Saudi Arabia, at the end of the fourth five-year plan (1985–1990) was reviewed and analyzed regarding the standards of services and workload of health personnel for the different regions and urban/rural areas in the Kingdom. Innovative indices for the quantitative analysis of medical facilities were developed. The analysis of health facilities in Saudi Arabia shows that the Kingdom enjoys a high standard of medical facilities. However, there are maldistribution of clinical resources and personnel between regions and between urban/rural areas. Utilization of these indices for the reallocation of medical facilities and personnel to ensure even distribution of services for all inhabitants of the Kingdom was illustrated. In addition, indices give a guideline for the future planning and the rate of increase of these facilities that keeps the standard of medical services in the proper class desired with minimum resources wastage.     

Recent trends of temperature and precipitation proxies in Saudi Arabia: implications for climate change

The objective of the present study was to reconstruct a short-term (12–14 years) trend of surface temperature and precipitation patterns using their surrogates as provided by satellite images for selected locations along the Red Sea mountains in Saudi Arabia. Time series land surface temperature (LST) and normalized difference vegetation index (NDVI) data acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite were temporally plotted to delineate the trend and the decadal rates of change of both parameters. Results showed that real climate change is reported in the study area during the study period. There is a net increasing in the surface temperatures by 0.45 to 1.2 °C/decade and a net decrease in annual rainfall between 2001 and 2014. Findings of the present study show that the region is under a warming of the climate and a declining of wetness, which coincide with the air temperature and rainfall trends obtained from meteorological stations.     

Diagnostic study of spring dusty days over the southwest region of the Kingdom of Saudi Arabia

Arabian Journal of Geosciences - Three classes of dust over the southwest region of the Kingdom of Saudi Arabia were classified based on both the values and distribution of the TOMS Aerosol Index....     

Statistical distribution of rainy events characteristics and instantaneous hyetographs generation (Merguellil watershed in central Tunisia)

In semi-arid regions, variability of rainfall inputs is high at different time and space scales. Thus, intense and highly variable hydro-meteorological events, which generate both potential resource and hazards, are of major interest. The Merguellil watershed is characterized by a large majority of rainfall in the form of storms, particularly violent in spring and autumn. Storms of summer are short and violent and can be the origin of important floods. Due to the strong rainfall variability, precipitation and hydrological regime are very irregular. This is what led us to think of a detailed study of rainy events. It was founded that two statistical distributions of parameters characterizing events are dominated (log normal, exponential).Thus, our objective consists in studying, in its globality, the collected pluviographic data in order to make a synthesis and analysis which should make it possible the generation of fictitious events to better control the rainfall risk and to study the response of the watershed faces to several types of rainfall. As result, we obtained hyetographs of the height studied rain gauges. These hyetographs show several types of events that are well in conformity with the observed reality. This generation is an advantageous tool in terms of both its robustness and its performance. Its relevance is based on the analysis of the fine time structure of recorded rainfall events. It can be made over several years, and would permit us to avoid being constrained by sample size. Generating rainfall events provides extensive time-related rainfall data that are consistent at all time steps, and can be seen as solution, even partially, of data lack in hydrological study.     

Causes of Land Subsidence in the Kingdom of Saudi Arabia

The occurrence of land subsidence in the Kingdom Saudi Arabia is either natural or man-made. Natural land subsidence occurs due to the development of subterranean voids by a solution of host rocks in carbonate and evaporite terrains, over many areas of Saudi Arabia. Man-induced land subsidence is either due to the removal of groundwater in the agricultural areas or to wetting of unstable soils. Therefore, earth fissures and a lowering of the ground surface in unconsolidated sediments took place in alluvial plains and volcanic vent terrains. Unstable soils include Sabkha soils and loess sediments. These types of soils occur in coastal plains, desert areas and volcanic terrains. When this soil is wetted either during agricultural activities, waste disposal or even during a rain storm, subsidence takes place due to either the removal of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments.