Extreme daily precipitation: the case of Serbia in 2014

The extreme daily precipitation in Serbia was examined at 16 stations during the period 1961–2014. Two synoptic situations in May and September of 2014 were analysed, when extreme precipitation was recorded in western and eastern Serbia, respectively. The synoptic situation from 14 to 16 May 2014 remained nearly stationary over the western and central Serbia for the entire period. On 15 May 2014, the daily rainfall broke previous historical records in Belgrade (109.8 mm), Valjevo (108.2 mm) and Loznica (110 mm). Precipitation exceeded 200 mm in 72 h, producing the most catastrophic floods in the recent history of Serbia. In Negotin (eastern Serbia), daily precipitation of 161.3 mm was registered on 16 September 2014, which was the maximum value recorded during the period 1961–2014. The daily maximum in 2014 was registered at 6 out of 16 stations. The total annual precipitation for 2014 was the highest for the period 1961–2014 at almost all stations in Serbia. A non-significant positive trend was found for all precipitation indices: annual daily maximum precipitation, the total precipitation in consecutive 3 and 5 days, the total annual precipitation, and number of days with at least 10 and 20 mm of precipitation. The generalised extreme value distribution was fitted to the annual daily maximum precipitation. The estimated 100-year return levels were 123.4 and 147.4 mm for the annual daily maximum precipitation in Belgrade and Negotin, respectively.

     

A Model to Interpolate Monthly Mean Climatological Data at Bavarian Forest Climate Stations

Summary  Six methods were used to interpolate the monthly mean climatological data from German climate stations to three Bavarian forest climate stations. The observed forest climatological data at the Bavarian forest climate stations were used as the reference data to which the interpolated data were compared. The results show that, for monthly mean daily maximum temperature at valley and plain forest climate stations, each of the six interpolation methods can give accurate estimates. For monthly mean daily maximum temperature, minimum temperature, air temperature and water vapor pressure at mountain forest climate stations, topographically aided interpolation can give the most accurate estimates. Barnes interpolation combined with empirical transfer functions can give accurate estimates forall climate variables at the plain and valley forest climate stations, and it can also give accurate estimates for monthly mean wind speed and monthly precipitation at the mountain forest climate station. The empirical transfer functions are very important for estimating the forest climatological data. These transfer functions will be used for reconstruction of long-term forest climatological data in Bavaria. Received September 9, 1998 Revised May 21, 1999     

Trends of Minimum and Maximum Daily Temperatures in Italy from 1865 to 1996

Summary Annual and seasonal changes in maximum and minimum temperatures (Tmax and Tmin) and in daily temperature range (DTR) in Italy are investigated. Monthly average series for northern and southern Italy are analysed for evidence of trend. Tmax and Tmin show a positive trend over the period 1865–1996 which is greater in southern Italy than in northern Italy. DTR shows a positive trend, but greater in the North than in the South. There is a positive correlation between DTR and mean monthly temperature especially in spring and in summer, while there is a high significant negative correlation between DTR and monthly precipitation. Analysis of temperature, precipitation and DTR during the period 1865–1996 suggests that a general relationship between the very warm last 15–20 years and an increase in the frequency of sub-tropical anticyclones over the Central-Western Mediterranean. This relationship is based on the hypothesis that in Italy more frequent sub-tropical anticyclones could have been the most characteristic feature of the warm periods during the last 130 years. Received June 4, 1999 Revised November 2, 1999     

Analysis of precipitation series for Belgrade

Summary Precipitation is a very variable climatic element. It is highly variable, both spatially and temporally at different scales (interannual and intra-annual). The search for cyclicity in the climatic record can resolve some of the complexities of the atmospheric system. This paper takes the example of the Belgrade precipitation series (1889–2000) to illustrate how trend and spectral analysis can provide information on climate variability as expressed through this particular variable.The annual, seasonal and monthly precipitation series of the Belgrade-Observatory station were analyzed by means of the Mann-Kendall test and the spectral analysis. The power spectra were calculated using the autocorrelation spectral analysis, the maximum entropy spectral analysis and the multitaper method.The influence of large-scale phenomena such as the El-Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) on the Belgrade precipitation series was investigated.     

BALTEX 1/6-degree daily precipitation climatology 1996–1998

Summary A precipitation correction and analysis (PCA) model has been designed and tested during the preparation phase of the BALTEX main experiment BRIDGE. The PCA model consists of a dynamical bias correction module and a geostatistical module. The bias correction reduces the systematic undercatch of the rain gauges due to wind-induced, evaporation and wetting losses by taking instrument-specific properties plus additional information from synoptic observations into account; the mean correction factor is maximum in February (1.25–1.50) and minimum in August (1.02–1.05). The geostatistical module is an ordinary block kriging algorithm; it yields gridded daily precipitation values plus error estimates on the 1/6-degree resolution of the meso-scale BALTEX models. Here we use 3 years (1996–1998) of 4000 rain gauge observations collected by the BALTEX Meteorological Data Centre for a preliminary high-resolution climatology of the BALTEX catchment. It comprises: Time-series of area-averaged daily precipitation; and area distributions of monthly and annual precipitation. Largely independent is the worldwide monthly GPCP data set which includes also satellite data and is available from 1979 on. GPCP yields, for the years 1996–1998, an average of 2.10 mm/day while our evaluation yields 2.01 mm/day. The maximum difference (22%) occurs in January; during the summer months the values are about equal. Received September 27, 2000 Revised February 6, 2001     

Deficit and surplus of precipitation as a continuous function of time

The quantitative measure of drought is a complex problem. A common factor in all types of drought is that they originate from a deficiency of precipitation. The difference between the real and potentially expected daily precipitation amount is what we have used to define the continuous function of daily deficit and surplus of precipitation (DSP). We have also defined the monthly and yearly DSP. We tested the precipitation data series for the normal climatic period 1961–1990 observed at the Meteorological Observatory of Belgrade. The DSP considers that the intensity of drought during the current period is dependent upon the current precipitation plus the cumulative precipitation of the previous period. When applied to longer periods, this function denotes dry and wet periods.     

Experimental Simulations of Extreme Precipitation Based on the Multi-Status Markov Chain Model

A multi-status Markov chain model is proposed to produce daily rainfall, and based on which extreme rainfall is simulated with the generalized Pareto distribution (GPD). The simulated daily rainfall shows high precision at most stations, especially in pluvial regions of East China. The analysis reveals that the multistatus Markov chain model excels the bi-status Markov chain model in simulating climatic features of extreme rainfall. Results from the selected six stations demonstrate excellent simulations in the following aspects:standard deviation of monthly precipitation,daily maximum precipitation,the monthly mean rainfall days,standard deviation of daily precipitation and mean daily precipitation, which are proved to be consistent with the observations. A comparative study involving 78 stations in East China also reveals good consistency in monthly mean rainfall days and mean daily maximum rainfall, except mean daily rainfall. Simulation results at the above 6 stations have shown satisfactory fitting capability of the extreme precipitation GPD method. Good analogy is also found between simulation and observation in threshold and return values. As the errors of the threshold decrease, so do the di?erences between the return and real values. All the above demonstrates the applicability of the Markov chain model to extreme rainfall simulations.     

The Characteristics of Cold Air Outbreaks over the Eastern Highlands of Kenya

Summary Climatological statistics of extreme temperature events over Kenya are established from the analysis of daily and monthly maximum temperatures for a representative station (Nairobi Dagoretti Corner) over the period 1956–1997. The months of June to August were shown to be the coldest with a mean monthly maximum temperature of less than 22 °C. Seasonal (June to August) mean maximum temperature was 21.5 °C. Using this seasonal mean temperature for the period 1967–1997 delineated 1968 as the coldest year in this series and 1983 as the warmest year. Spectral analysis of the seasonal data, for both the coldest and the warmest years, revealed that the major periods were the quasi-biweekly (10 days) and the Intraseasonal Oscillations (23 days). Secondary peaks occurred at periods of 4–6 and 2.5–3.5 days. A temperature threshold of 16.7 °C during July was used to define cold air outbreaks over Nairobi. This threshold temperature of 16.7 °C was obtained from the mean July maximum temperature (20.9 °C) minus two standard deviations. Notable trends include a decrease in the frequency of station-days, between 1956 and 1997, with temperatures less than 16.7 °C during July. Surface pressure patterns indicate that the origin of the cold air is near latitude 25° S and to the east of mainland South Africa. The cold air near 25° S is advected northwards ahead of the surface pressure ridge. Received July 19, 1999 Revised January 11, 2000     

Spatial analysis of monthly precipitation in Turkey

Summary  The principal objectives of this paper are to develop and validate an optimum interpolation method for the spatial analysis of monthly precipitation in Turkey. A two-dimensional optimum interpolation objective analysis scheme has been developed for the spatial analysis of precipitation. The model is developed for generating statistically optimum interpolation based on the irregular distribution of meteorological stations. One question that affects the optimum interpolation method and, indeed, all such techniques, is how many observations should be allowed to influence a given grid point? The method developed in this paper addresses this question. For the implementation of the method, 52 stations are considered for Turkey, with 30 years of monthly data at each point. It is observed that each monthly average spatial correlation function shows a monotonically decreasing pattern based on 15 km interval averages. The method provides high estimation accuracy in dense station locations such as in northwestern Turkey. Precipitation contour maps obtained by the optimum interpolation method indicate two spatial trends over Turkey which have not been identified in any previous study. Received June 24, 1999/Revised April 26, 2000     

The frequency, intensity, and diurnal cycle of precipitation in surface and satellite observations over low- and mid-latitudes

Global precipitation data sets with high spatial and temporal resolution are needed for many applications, but they were unavailable before the recent creation of several such satellite products. Here, we evaluate four different satellite data sets of hourly or 3-hourly precipitation (namely CMORPH, PERSIANN, TRMM 3B42 and a microwave-only product referred to as MI) by comparing the spatial patterns in seasonal mean precipitation amount, daily precipitation frequency and intensity, and the diurnal and semidiurnal cycles among them and with surface synoptic weather reports. We found that these high-resolution products show spatial patterns in seasonal mean precipitation amount comparable to other monthly products for the low- and mid-latitudes, and the mean daily precipitation frequency and intensity maps are similar among these pure satellite-based precipitation data sets and consistent with the frequency derived using weather reports over land. The satellite data show that spatial variations in mean precipitation amount come largely from precipitation frequency rather than intensity, and that the use of satellite infrared (IR) observations to improve sampling does not change the mean frequency, intensity and the diurnal cycle significantly. Consistent with previous studies, the satellite data show that sub-daily variations in precipitation are dominated by the 24-h cycle, which has an afternoon–evening maximum and mean-to-peak amplitude of 30–100% of the daily mean in precipitation amount over most land areas during summer. Over most oceans, the 24-h harmonic has a peak from midnight to early morning with an amplitude of 10–30% during both winter and summer. These diurnal results are broadly consistent with those based on the weather reports, although the time of maximum in the satellite precipitation is a few hours later (especially for TRMM and PERSIANN) than that in the surface observations over most land and ocean, and it is closer to the phase of showery precipitation from the weather reports. The TRMM and PERSIANN precipitation shows a spatially coherent time of maximum around 0300–0600 local solar time (LST) for a weak (amplitude <20%) semi-diurnal (12-h) cycle over most mid- to high-latitudes, comparable to 0400–0600 LST in the surface data. The satellite data also confirm the notion that the diurnal cycle of precipitation amount comes mostly from its frequency rather than its intensity over most low and mid-latitudes, with the intensity has only about half of the strength of the diurnal cycle in the frequency and amount. The results suggest that these relatively new precipitation products can be useful for many applications.     

Monthly and daily precipitation trends in the Mediterranean (1950–2000)

Summary The aim of the paper lies in the identification of possible significant linear trends at monthly, seasonal and annual timescales in the Mediterranean during the second half of the 20th century. Monthly and daily records of 63 stations have been used to elaborate several precipitation indices: sum of daily precipitation (SDP) for rainfall >0.1 mm, >10 mm and >95^th percentile, of number of rainy days (RD) >0.1 mm and >10 mm and of mean daily precipitation (MDP) >0.1 mm and >10 mm. For each index the stations have been gathered together by Rotated Principal Component Analyses to determine 8 sub-areas which can be considered as identical for all the timescales at the spatial scale of the research. Trends have been estimated from the scores of each eigenvector retained in all RPCAs. They are mainly non existant or non significant decreasing, even if a few monthly trends appear to be significantly diminishing, primarily during winter months, March in the Atlantic region, October in the Mediterranean Spain, December in the Lions and Genoa Gulfs, January, winter and the year in Greece, winter and the year in Italy and winter in the Near East and increasing in April in the two gulfs. Correlation coefficients between SDP>0.1 mm and other indices have been computed: the significant trends seem mainly related to RD>10 mm, which represents a high percentage of the total rainfall amount. Greece is remarkable: SDP>0.1 mm and >10 mm decrease significantly during January, winter, the rainy season and the entire year whereas SDP>95^th percentile increases significantly, in accordance with the climatic change scenarios for the end of this century as does the decreasing of the total monthly and seasonal rainfall.     

Some annual variation characteristics for the Northern Hemispheric monthly mean precipitation fields

By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the “World Survey of climatology, Vol. 1-15, the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types (continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east- and-west shift.     

天山山区大气水分循环特征

将自然正交分解(EOF)和水平空间分辨率30"的地理信息数字高程(DEM)相结合,利用1961~2010年天山山区及其周边79个气象站月降水量应用梯度距离平方反比法计算面雨量,应用2000~2010年NCEP/NCAR逐日4次再分析1°(纬度)×1°(经度)资料计算水汽输送,研究了天山山区面雨量时空分布、水汽输送和外部水汽的降水转化率特征,以及降水转化率异常的初步成因。结果表明:1)天山西部和中部降水量平均在450 mm以上,东天山和天山西南端为150 mm左右。春季、夏季、秋季、冬季的面雨量分别为291.4×108 m3、625.9×108m3、218.1×108 m3和73.6×108m3,降水量分别为108.2 mm、232.4 mm、81.0 mm和27.4 mm,年降水量为449.0 mm。2)月水汽输送量呈正态单峰型分布,7月最大、1月最小,夏季水汽输送量为全年的41.3%,冬季为11.9%,春季、秋季分别为24.5%和22.3%。3)春季、夏季、秋季、冬季和年外部水汽的降水转化率分别为10.3%、12.6%、8.5%、5.4%和9.2%,降水转化率的大小与伊朗副热带高压、贝加尔湖高压脊和西亚副热带西风急流的位置和强度配置有关。     

Surface energy balance complexity in GCM land surface models. Part II: coupled simulations

 Global coupled simulations with the Bureau of Meteorology Research Centre climate model and the CHAmeleon Surface Model (CHASM) are used to examine how four general extensions to the representation of the basic land surface energy balance affect simulated land-atmosphere interface variables: evaporation, precipitation, skin temperature and air temperature. The impacts of including separate surface energy balance calculations for: vegetated and non-vegetated portions of the land surface; an explicit parametrisation of canopy resistance; explicit bare ground evaporation; and explicit canopy interception are isolated and quantified. The hypothesis that these aspects of surface energy balance parametrisation do not contain substantial information at the monthly time scale (and are therefore not important to consider in a land surface model) is shown to be false. Considerable sensitivity to each of the four general surface energy balance extensions is identified in average pointwise monthly changes for important land-atmosphere interface variables. Average pointwise changes in monthly precipitation and land evaporation are equal to about 40 and 31–37% of the global-average precipitation and land evaporation respectively. Average pointwise changes for land surface skin temperature and lowest model layer air temperature are about 2 and 0.9 K respectively. The average pointwise change and average pointwise biases are statistically significant at 95% in all cases. Substantial changes to zonally average variables are also identified. We demonstrate how the globally averaged surface resistance parameter can vary from 150 to 25 s/m depending on which aspects of the surface energy balance are treated implicitly. We also show that if interception is treated implicitly, the effective surface resistance must vary geographically in order to capture the behaviour of a model which treats this process explicitly. The implication of these results for the design of land surface models is discussed. Received: 8 July 1999 / Accepted: 1 September 2000     

Extreme daily precipitation in Belgrade and their links with the prevailing directions of the air trajectories

The main goal of this study was to present the statistical analysis of the daily precipitation exceeding 20 mm in Belgrade and their links with the prevailing directions of the air trajectories at 500, 1,500 and 5,000 m. For the extreme precipitation analysis, the generalised extreme value (GEV) distribution and generalised Pareto distribution (GPD) were used. The estimated return levels for 100- and 10-year return periods using GEV and GPD were obtained. Four-day backward trajectory simulations were conducted for days with precipitation exceeding 20 mm to investigate the regional transport of the air moisture towards Belgrade using the hybrid single-particle Lagrangian integrated trajectory model. The air trajectories were classified into 13 trajectory categories by the origin and direction of their approach to Belgrade. Three of the most frequent categories of air flow from south-west, south-east and north-west contributed to more than a half of the observed precipitation. Almost 74.5 % of precipitation totals in Belgrade fell during the warmer part of the year. These were directly connected with the intensive convection of colder and humid, usually maritime, air masses.     

Self-similarity patterns of precipitation in the Iberian Peninsula

Summary An objective classification of the precipitation field over the Iberian Peninsula and the Balearic Islands is obtained. Data are derived from a high-resolution daily precipitation dataset obtained from in-situ measurements. The dataset, Iberian monthly Precipitation Dataset (IPD), consists of monthly precipitation data over a 25 km × 25 km grid from 1^st January 1961 to 31^st December 2003. Therefore, 960 data series over the Iberian Peninsula and the Balearic Islands are disposed over the grid for 43-year period. Multi-resolution wavelet analysis is used to extract similar information in the precipitation field at different timescales. An objective classification of the obtained wavelet coefficient series is carried out by means of the Kohonen’s neural network, also named Self-Organizing Map (SOM). SOM is formed by an unsupervised learning algorithm that may be used to find clusters of similar events in the input data and is able to identify some underlying dynamic structures of the multi-dimensional datasets. SOM is applied to the wavelet coefficients for intramonthly, intermonthly and interannual oscillations, obtaining self-organised maps which objectively identify similar zones of precipitation behaviour over the Iberian Peninsula. The homogeneity of the patterns is also studied by means of non-parametric correlations, energy scalograms and tests of significance. The intramonthly, intermonthly and interannual waves resulted in seven, five and three SOM patterns, respectively. As timescale increases, the wavelet series coefficients tend to be highly clustered. The results indicate that as the oscillation frequencies decrease, the Iberian precipitation behaves more linearly.     

The Reconstruction of Paleovegetation and Paleoclimate in the Late Pliocene of West Yunnan, China

The Eryuan palynoflora from the Late Pliocene of western Yunnan, China is described in this paper, and is compared with two contemporary palynofloras from Yangyi and Longling. The palynological data of the three locations are analyzed to reconstruct the climatic parameters of these areas at that time by using the Coexistence Approach. The Late Pliocene climatic parameters of Eryuan are estimated, i.e., the mean annual temperature ranged from 13.3 to 18.6^∘C, the mean temperature of the warmest month from 24.6 to 27.5^∘C, the mean temperature of the coldest month from 1.9 to 12.1^∘C, the difference in temperatures of coldest and warmest month from 14.2 to 16.6^∘C, the mean annual precipitation from 619.9 to 1484.3 mm, the mean maximum monthly precipitation from 143.8 to 245.6 mm, and the mean minimum monthly precipitation from 12.7 to 16.4 mm. Both paleovegetation and paleoclimate of the three localities are compared with the modern data at each location. The present study suggests a MAT decrease accompanied by a doubling of the MAP in the Longling area between the Late Pliocene and the present. This seems to be related to the uplift of Gaoligong Mountain in Longling which is now part of the eastern portion (Western Yunnan) of the Tibetan Plateau.     

Climatology of Precipitation of Different Genesis in Northern Eurasia

A method for discriminating among different types of precipitation is presented. The method is based on surface observations of precipitation, present and past weather, and the morphological types of clouds. The climatology of showery, nonshowery, and drizzle precipitation in Northern Eurasia is studied using the data of 529 Russian weather stations for the period of 1966–2014. Showery precipitation dominates in Northern Eurasia. In general, showery precipitation has greater temporal (monthly and diurnal) and spatial variability than nonshowery precipitation. The majority of showers are registered in summer (the maximum is in July), whereas the high est total monthly nonshowery precipitation is observed in autumn (the maximum is in October). The daily intensity values of showery and nonshowery precipitation are generally close, the maximum intensity is recorded in July–August. For three-hour in tervals, the shower in tensity is by 1.1–1.5 times higher. The drawbacks of the presented methodology are discussed.     

A statistical analysis of the daily precipitation over Serbia: trends and indices

A statistical analysis of the daily maximum and mean monthly precipitation measured at ten meteorological stations in Serbia during the period 1949?C2007 is presented. Although the means of the daily maximum and monthly precipitation varied throughout the year, their ratio was almost uniform, with an average value of 32.6% for Serbia. The precipitation events within each year were ranked and then the trends on the ten wettest days of the year were assessed. Averaged across Serbia, the wettest day of the year produces 41.3?mm of precipitation and accounted for 6.3% of the total annual precipitation. Taken together, 35.5% (232.0?mm) of the total annual precipitation fell during the ten wettest days of the year. Over the course of the twentieth century, the average annual precipitation on the wettest day across Serbia increased by nearly 9%. Also, averaged across Serbia, statistically insignificant increasing trends were found on each of the ten wettest days of the year. Furthermore, four climate indices were analysed. Heavy precipitation indices (i.e., RR20 and R95T) increased in Serbia at the end of the twentieth century and thereafter.     

近50a中国降水格点数据集的建立及质量评估

基于2012年6月更新的高质量2 400个台站降水资料,采用薄盘样条法,制定了采用3个自变量(经度、纬度、海拔高度)、降水量开平方预处理、3次样条的插值方案,并引入数字高程资料,以减弱中国独特地形条件下高程对降水空间插值精度的影响,并对1961—2010年中国区域地面降水站点资料进行了空间内插,得到了中国地面降水0.5°×0.5°格点数据集。经数据集的质量评估结果表明:分析值与站点观测值均方根误差平均为0.49 mm,相关系数平均达0.93(通过0.01的显著性检验),夏季插值误差高于冬季,东南地区误差普遍高于其他地区。冬、春、夏、秋季绝大多数台站绝对误差在±10 mm/月以内。冬、春、夏、秋季分别有60%、82%、54%、77%的台站相对误差在±10%之间。插值后的格点化降水资料能够比较细致、准确地描述中国大陆年平均降水场的东南多、西北少的主要空间特征,但也平滑掉了范围很小的降水极值中心。台站分布越密集的地方,插值效果越好,并且最近距离小于40 km的台站插值精度较高,大于40 km插值精度衰减较快。