Number Of Precipitation Days Research Articles

Spatial and temporal characteristics of summer precipitation events spanning different numbers of days over Asia

ABSTRACTConsidering the physical connections with circulation systems of different life cycles, precipitation events are classified based on their durations (the number of consecutive days with significant precipitation). By analysing spatial and temporal characteristics of summer precipitation events of different types over Asia, the present study indicates that weather systems with different life cycles predominate over different regions of Asia and control the occurrence of precipitation events of different types and their respective contributions to precipitation days and amount. Mid‐high latitude blockings govern the North Asian region and result in more long duration (over‐8‐day) events contributing a non‐negligible part to total number of precipitation days (NOPDs) and precipitation amount. Synoptic weather processes induce more short duration events and increase the fractional contribution of short duration events over the central Asian region. Persistent Asian monsoon‐related circulations and intermittent intrusions of cold air flows from the north produce long (over‐14‐day) and short (3‐to 5‐day) duration events, respectively, which contribute a high percentage over southern China. The Indian summer monsoon and the topographic effect jointly cause more over‐14‐day events and make a larger contribution over the west coast of the Indian Peninsula. The mean intensity of different events, as well as intense precipitation events, has obvious regional dependence and is affected by different weather systems and topographic effects. The interdecadal changes in total NOPDs and the regrouping of events with different durations and intensities are both responsible for the interdecadal increases in total precipitation amount over Northeast China and the upper reaches of the Yangtze River valley around the late 1970s and that over southern China around 1993.The interdecadal decrease in precipitation over southern China around the late 1970s is primarily attributed to the regrouping of different events rather than the changing NOPDs.

Changes in precipitation extremes in Romania

Changes in daily extreme precipitation have been identified in many studies conducted at local, regional, or global scales. In Romania, little research on this issue has been done. The present study focuses on the analysis of the trends in daily extreme precipitation indices over a period of 53 years (1961–2013). Data sets of daily precipitation recorded in 34 weather stations were analyzed. Among them, three are located in the Carpathians and four on the Black Sea Coast. The main goal was to find out changes in extreme daily precipitation using a set of 13 indices adopted from the core indices developed by ETCCDMI adapted to suit to the studied area. The series of indices and their trends were generated using RClimDex software. The trends have been calculated by employing modified Mann–Kendall test and Sen's slope. Generally, the climate of Romania has become wetter over the 53-yr period considered, especially in the northern regions, although the spatial distribution of the significant trend slopes in the area is extremely irregular. Based on fixed threshold indices analysis, extreme precipitation events are characterized by a decreasing in the total number of precipitation days (R0.1), and a dominant increasing trend for the number of isolated days with moderate and heavy precipitation (R5, R10).

Analyzing Precipitation Using Concentration Indices for North Gujarat Agro Climatic Zone, India

The climate of India defies easy generalisation, comprising a wide range of weather conditions across a large geographic extent and varied topography. India's unique geography and geology strongly influence its climate; this is particularly true of the Himalayas in the north and the Thar Desert in the northwest. As in much of the tropics, monsoonal and other weather conditions in India are unstable: major droughts, floods, cyclones and other natural disasters are sporadic, but have killed or displaced millions. India's long-term climatic stability is further threatened by global warming. Climatic diversity in India makes the analysis of these issues complex. Gujarat is divided into eight agroclimatic zones. For the present study north Gujarat agroclimatic zone is considered. The major objectives of present study are to investigate the climate characteristics in the area. For the present study daily precipitation data from 167 raingauge stations for 48 years (1961–2008). The present study methodologically attempts to determine the structure of the accumulated precipitation amounts contributed by the accumulated number of precipitation days using concentration index, COIN, to represent the distribution and intensity of the precipitation. The COIN values are ranging from 0.54 to 0.66 with an average value of 0.60. It can be concluded that a concentration index, defined on the basis of the exponential curves, enables the evaluation of contrast or concentration of the different daily amounts of the precipitation by regionalizing the study area into lower and higher variability.

Changes of precipitation intensity spectra in different regions of mainland China during 1961–2006

The spectral characteristics of precipitation intensity during warm and cold years are compared in six regions of China based on precipitation data at 404 meteorological stations during 1961–2006. In all of the studied regions except North China, with the increasing temperature, a decreasing trend is observed in light precipitation and the number of light precipitation days, while an increasing trend appears in heavy precipitation and the heavy precipitation days. Although changes in precipitation days in North China are similar to the changes in the other five regions, heavy precipitation decreases with the increasing temperature in this region. These results indicate that in most parts of China, the amount of precipitation and number of precipitation days have shifted towards heavy precipitation under the background of a warming climate; however, the responses of precipitation distributions to global warming differ from place to place. The number of light precipitation days decreases in the warm and humid regions of China (Jianghuai region, South China, and Southwest China), while the increasing amplitude of heavy precipitation and the number of heavy precipitation days are greater in the warm and humid regions of China than that in the northern regions (North China, Northwest China, and Northeast China). In addition, changes are much more obvious in winter than in summer, indicating that the changes in the precipitation frequency are more affected by the increasing temperature during winter than summer. The shape and scale parameters of the Γ distribution of daily precipitation at most stations of China have increased under the background of global warming. The scale parameter changes are smaller than the shape parameter changes in all regions except Northwest China. This suggests that daily precipitation shifts toward heavy precipitation in China under the warming climate. The number of extreme precipitation events increases slightly, indicating that changes in the Γ distribution fitting parameters reflect changes in the regional precipitation distribution structure.

An investigation of some unexpected frost day increases in southern Australia

Understanding changes in frost events is vital given their impacts on crops. This study examines monthly frost day trends in southern Australia, using Australian homogeneous temperature stations. Century-scale annual frost day trends show decreases consistent with expectations in a warming climate. The past 32 years however exhibit more complex and seemingly contradictory changes. At some locations increases in annual number of frost days are observed, while other lo- cations show decreases more consistent with the longer term trend. Assessing monthly trends, we nd a consistent increase in frost days at all stations in south- east Australia in late autumn (May). The trends are downwards during the winter months (June, July and August) indicating a decrease in the number of frost days. In early spring (August and September), the sign of the trend varies substantially between stations. Similarly, southwest Western Australia has experienced in- creases in the monthly number of frost days. However, in contrast to southeast Australia, the increases are observed throughout the second half of the cold sea- son. We examine the relationship with the concurrent recent drying since the 1990s in southeast Australia and since the 1970s in southwest Western Australia. In dry periods during the winter half year, clear-sky conditions are expected to occur more frequently, leading to larger diurnal temperature ranges and colder night-time tem- peratures. This study provides further evidence that southeastern Australian frost day increases are linked to concurrent rainfall declines by analysing the relationship between number of frost days and number of precipitation days.

Projected changes in precipitation intensity and frequency in Switzerland: a multi‐model perspective

ABSTRACTFundamental changes in the hydrological cycle are to be expected in a future warmer climate. For Switzerland, recent climate change assessments based on the ENSEMBLES regional climate models project for the A1B emission scenario summer mean precipitation to significantly decrease by the end of this century, whereas winter mean precipitation tend to rise in Southern Switzerland. From an end‐user perspective, projected changes in seasonal means are often insufficient to adequately address the multifaceted challenges of climate change adaptation. In this study, we investigate the projected changes in seasonal precipitation by considering changes in frequency and intensity, precipitation type (convective vs stratiform) and temporal structure (wet and dry spells) over Switzerland. As proxies for rain‐type changes, we rely on the parameterized convective and large‐scale precipitation components simulated by the models. The study reveals that the projected summer drying over Switzerland at the end of the century is mainly driven by a widespread reduction in the number of precipitation days. Thereby, the drying evolves altitude‐specific: over low‐land regions it is associated with a decrease in both convective and large‐scale precipitation. Over elevated regions it is primarily associated with a decline in large‐scale precipitation only, whereas convective precipitation remains at current levels. As a consequence, almost all the models project an increase in convective fraction at elevated altitudes. The decrease in the number of wet days during summer is accompanied by decreases (increases) in the number of multi‐day wet (dry) spells. This future shift in multi‐day episodes also lowers down the likelihood of short dry spell occurrence in all of the models. The models further project a higher mean precipitation intensity in spring and autumn north of the Alps, whereas a similar tendency is expected for the winter season over most of Switzerland.

The year-long unprecedented European heat and drought of 1540 – a worst case

The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring–summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km2, we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models.

Greenland precipitation trends in a long‐term instrumental climate context (1890–2012): evaluation of coastal and ice core records

ABSTRACTHere, we present an analysis of monthly, seasonal, and annual long‐term precipitation time‐series compiled from coastal meteorological stations in Greenland and Greenland Ice Sheet (GrIS) ice cores (including three new ice core records from ACT11D, Tunu2013, and Summit2010). The dataset covers the period from 1890 to 2012, a period of climate warming. For approximately the first decade of the new millennium (2001–2012) minimum and maximum mean annual precipitation conditions are found in Northeast Greenland (Tunu2013 c. 120 mm water equivalent (w.e.) year−1) and South Greenland (Ikerasassuaq: c. 2300 mm w.e. year−1), respectively. The coastal meteorological stations showed on average increasing trends for 1890–2012 (3.5 mm w.e. year−2) and 1961–2012 (1.3 mm w.e. year−2). Years with high coastal annual precipitation also had a: (1) significant high number of precipitation days (r2 = 0.59); and (2) high precipitation intensity measured as 24‐h precipitation (r2 = 0.54). For the GrIS the precipitation estimated from ice cores increased on average by 0.1 mm w.e. year−2 (1890–2000), showing an antiphase variability in precipitation trends between the GrIS and the coastal regions. Around 1960 a major shift occurred in the precipitation pattern towards wetter precipitation conditions for coastal Greenland, while drier conditions became more prevalent on the GrIS. Differences in precipitation trends indicate a heterogeneous spatial distribution of precipitation in Greenland. An Empirical Orthogonal Function analysis reveals a spatiotemporal cycle of precipitation that is linked instantaneously to the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation and with an ∼6 years lag time response to the Greenland Blocking Index.

Spatial and temporal variability of winter snow and precipitation days in the western and central Spanish Pyrenees

ABSTRACTIn this study we analysed the spatial distribution of the long‐term average and interannual variability of the number of snow days (NSD) and the number of precipitation days (NPD) in winter (DJFM) in the Spanish Pyrenees, using data from 38 meteorological stations for the period 1981–2010. The interannual variability of the NSD and the NPD in winter was related to the frequency of weather types over the Iberian Peninsula. Data from six stations were also used to analyse a longer time period (1961–2013) to confirm the consistency of the results obtained during the main study period (1981–2010).The results indicated that the NPD is only influenced by the distance to sea whereas the NSD is determined by elevation and distance to the sea. A high frequency of west (W), northwest (NW) and cyclonic (C) weather systems led to a high NPD in winter across the entire study area, whereas the frequency of north (N) weather types was only correlated with the NPD at the most westerly stations. For the NSD there was a gradient from the Western Pyrenees to eastern areas, mainly explained by the frequency of N weather types in the former area, and high frequencies of NW and W weather types associated with the latter. For most stations there was no significant trend found in the NPD or the NSD for the 1981–2010 period. However, a slight decrease was found for stations strongly correlated with NW weather types, and a slight increase was found for stations strongly correlated with the C weather type, which was related to a decreasing (increasing) frequency of NW (C) weather types during the same period. Analysis of the 1961–2013 and 1971–2000 time slices using a smaller subset of stations revealed a similar relationship between weather types and the NSD. This indicates that the 1981–2010 period is sufficiently representative to describe the relationship of the NSD and the NPD to weather type frequency. However, the study period chosen can markedly influence the trends observed, as the results showed a statistically significant decrease in the NSD for the 1971–2000 period, but no significant trends for the 1961–2013 and 1980–2010 periods.

Long-term variability and changes of the precipitation regime in Pakistan

This paper presents an examination of precipitation amounts in Pakistan. For this purpose, the annual precipitation and the annual number of precipitation days have been calculated, and a study aimed at investigating precipitation intensity and decadal changes was conducted. Precipitation trends have been calculated using a simple linear regression method and Kendall’s tau-based test. To assess stability and differences, a 10-year span was determined for each precipitation region for the period of 1951–2010. This study focused on the three CLINO (Climatological Normal) periods, namely 1961–1990, 1971–2000, and 1981–2010 (the latest global standard normal period). Results confirm the gradual increase of annual precipitation in southwestern coastal areas of Pakistan and Cholistan desert. With regard to annual number of precipitation days, in the central part of the country negative trends were evident for wet days (with precipitation ≧ 0.1 mm), while the number of rainy days (with precipitation ≧ 1 mm) displayed a prominent positive trend. The series of the precipitation intensity gives evidence of a minor decrease in the Baluchistan Plateau, sub-Himalayas, and Potwar Plateau during the study period. Examination of secular trends evidenced that the Murree hills, the upper Indus plain, and the northwestern Baluchistan plateau have had shifts in their precipitation regime towards drier conditions, while the central plain, the northwestern mountains, and the southern part of the country are shifting in their precipitation regime towards wetter conditions. Description among the means of precipitation amounts suggests that “normal” precipitation data for various national projects should be calculated for the last 30 years.

The precipitation change in Eastern Forest Regions of China in recent 50 years

The Eastern Forest Region is of importance for its economic timber forest and water and soil conservation in China. It provides basic information and response to climate change by analysis on the precipitation change of the Eastern Forest Region. In this study, the missing daily precipitation data was interpolated by spatial correlation and stepwise regression methods, and the Standard Normal Homogeneity Test (SNHT) was used to examine the homogeneity of the data serial with the interpolated value(s) on all individual discontinuous points among the entire annual data serial, to obtain the interpolated value of any missed data by passing the STHT test. Finally, the full precipitation data set with a full annual series of 853 Observation Stations in the Region was completely obtained. Based upon that precipitation data set from 1961 to 2010, the long-term change trend of the annual precipitation, numbers of precipitation days, seasonal precipitation and extreme precipitation were analyzed. The results revealed that the annual precipitation increased insignificantly with a tendency of 5.58mm/10a, but with an obvious decadal fluctuation; however, the spatial distribution of precipitation is not uniform, with decreasing trends in northern part, but increasing trends in the southern part of the Eastern Forest Region. Annual number of precipitation days had a significance reduce; showing a consistent decreasing trend in many stations in the Eastern Forest Region. The proportion of the annual amount of light rain (0.1–9.9mm/d) and moderate rain (10.0–24.9mm/d) to the annual precipitation and the annual number of the light rain and moderate rain days were significantly decreasing in recent 50years. Both the percentage of annual extreme precipitation and percentage of annual extreme precipitation days had a significant tendency of increase, both intensity and frequency of extreme precipitation events have contributed to the rising of the extreme precipitation amount, extreme precipitation events which were tending to become frequencies and intensified, it might have increased the risk of severe floods in the Eastern Forest Region. In the recent 50years, the trends of amount and days of the rainstorms (50.0–99.9mm/d) and the heavy rainstorms (⩾100mm/d) in the region increased significantly, with the values 5.59mm/10a, 0.07d/10a and 4.27mm/10a, 0.03d/10a respectively. The Mann-Kendall abrupt change test was conducted on the two different intensity rains, and the results showed the amount and days of both rainstorms and heavy rainstorms exhibited an abrupt change, the amount and days had significant increasing shift. While the remarkable increase of both the amount and days of the rainstorms presented since the middle 1980s, the heavy rainstorms since 1990s. The basic characteristics of seasonal precipitation in the Eastern Forest Region during the recent 50years are investigated. For the seasonal precipitation in June to August and December to next February had an increasing tendency, with linear trends of 11.22mm/10a and 5.91mm/10a, respectively; while the decreasing tendencies in March to May and September to November in the Region, with linear trends of −2.59mm/10a and −8.96mm/10a, respectively.

Understanding effects of global change on water quantity and quality in river basins- The SCARCE Project

The increasing anthropogenic manipulation of the hydrological cycle, as well as the exacerbation of climate change forcing, result in resource pressures that translate in even larger uncertainties in sensitive geographical areas. In particular, the Mediterranean region is undergoing severe alterations in water availability because of a decrease in the number of precipitation days but also in an increase of heavy rain events. An imbalance between water availability and its use is obvious in these water-thirsty regions, and clearly impacts the sustainability of water resources. The consequences are multiple, and include direct impacts on economic sectors that use and depend upon water availability, such as agriculture, tourism or industry. Ultimately, however, these consequences are the basis for a conflict between natural ecosystems and human needs, where ecosystems are those most challenged and their services remain at risk. The effects of water scarcity on river basins extend from its associated hydrological irregularity to the chemical quality of available water systems. Higher nutrient and pollutant concentrations are expected under lower water flows, both as an effect of direct human inflows as well as a simple effect of lower water dilution. This is especially relevant in many arid and semi-arid river systems, where flowing waters under scarcity mostly consists of treated sewage effluents. Wastewaters are being reused for drinking purposes and agriculture; some chemical compounds may eventually be transported from the waste water treatment plants (WWTPs) to river waters, and affect the chemical and biological quality of those waters. In these situations, potential water quality problems extend to the higher concentration of emerging pollutants, presence of pathogenic organisms, and multiple effects on the biota dwelling within the river systems. Biological communities respond to harsher environmental conditions imposed by scarcity with lower diversity, arrival of invasive species, as well as with lower efficiency of biological processes, some involving water quality as a return. The increased pressure on water resources will cause additional effects on aquatic ecosystems, in which the stress being produced by scarcity may sum up others physical or chemical stressors. Groundwater quality may be also affected by farming, or after leakage of industrial and domestic pollutants, making the use of these resources much more tenuous. This special issue is a collection of key articles presented at the 1st Annual Conference of the SCARCE-CONSOLIDER Responsible editor: Philippe Garrigues

Precipitation variations in Beijing during 1860–1897 AD revealed by daily weather records from the Weng Tong‐He Diary

AbstractDaily weather records from a historical private diary provide important data for studying historical climate change. We compiled daily weather records from the Weng Tong‐He Diary and counted the number of monthly precipitation days during 1860‐1897 AD for Beijing; then, using the number of monthly precipitation days, we reconstructed the seasonal precipitation using regression models relating the precipitation and precipitation days. The findings show that the monthly mean number of precipitation days for 1860‐1897 was greater than that for 1951‐2009 by about 1 d month−1 and that the summer (June to August, JJA) precipitation for 1860‐1897 was 471.8 mm greater than that for 1951‐2009 by about 15.5%. The JJA precipitation of 1860‐1897 had not only inter‐annual variations but also inter‐decadal variations that were characterized by less precipitation before 1886 (about 421.9 mm) and more precipitation thereafter (about 550.7 mm). As a consequence, the JJA precipitation of 1860‐1897 showed an evident positive trend with a rate of about 57.9 mm per decade. These precipitation variations were confirmed by other datasets. However, it is worth noting that our reconstruction underestimates the historical precipitation values (by about 22.5%) because of rainfall/snowfall events missed in Weng's diary and the poor ability of the regression models to capture extreme years. In the future, new methods of reconstructing precipitation with the consideration of missed rainfall/snowfall events are needed. Copyright © 2012 Royal Meteorological Society

1956-2009年内蒙古苏尼特左旗荒漠草原的降水格局

At present,precipitation pattern has taken significantly change under the effect of global change.To find out how precipitation pattern changes in different regions is very important to understand climate change and its consequences.The change of precipitation pattern includes variations of precipitation amounts,precipitation days,inter-precipitation periods and precipitation intensity.Desert steppe was the typical vegetation type in temperate arid and semi-arid regions,which was very sensitive to climate change,especially precipitation pattern changes.Precipitation was the main limiting factor in desert steppe ecosystem,whose variability determined the basic functions of this ecosystem.So it was in urgent need to find precipitation pattern variations in Chinese desert steppe under global change background. In this study,precipitation data from 1956 to 2009 in typical desert steppe of Sunite Left Banner in Inner Mongolia were collected and precipitation amounts,precipitation days,inter-precipitation periods and precipitation intensity were analyzed.Among them,Mann-Kendall method was used to analyze precipitation tendency and test significance,least square method was used to calculate the tendency values.The result showed that(1) from 1956 to 2009,the whole tendency of the annual precipitation amount and growing season precipitation amount were decreased,but the change tendency was different with the time.Among them,precipitation increased in 1970s but decreased in 1960s,1980s and 1990s,then increased in 2000s.Annual mean precipitation amount was 191.9 mm,the range value was 100—250 mm,and the tendency value was-8.5 mm/10a.Amount of precipitation in the growing season accounted for 85% of the whole year′s,which mainly occurred from June to August,and the variation coefficient of each month was above 50%.(2) Both mean annual precipitation days and short inter-precipitation period decreased but long inter-precipitation period increased from 1956 to 2009.Annual mean precipitation days were 63.8 days,the range value was 50—80 d,the tendency value was-2.5 d/10a and its variation coefficient was 16.9%.Number of precipitation days in the growing season accounted for 63% of the whole year′s,and the variability of each month was above 28%,and tendency value was-3 d/10a.(3) Precipitation intensity was distinguished as six different types: light,relatively light,moderate,relatively heavy,heavy and extremely heavy.Precipitation events were dominated by moderate precipitation amounts and light rainfall days,and there were few events above moderate precipitation level,no matter in the whole year or each month of the growing season.Moderate precipitation accounted for 32% of annual precipitation amounts,and light precipitation accounted for 68% of the annual precipitation days.Precipitation decrease in the whole year mainly resulted from moderate precipitation events,while the decrease in precipitation during the growing season was primarily due to light precipitation events.In generally,from 1956 to 2009,mean annual precipitation amounts,precipitation days and the different precipitation types in the whole year and the growing season all decreased,particularly there was a consistent decline of annual precipitation days since 1990s. Decreasing annual precipitation would affect soil moisture and plant reviving,while decreasing precipitation in the growing season would directly affect carbon sequestration in the grasslands.Under the scenarios of climate change,reduced precipitation in the whole year and growing season would further exacerbate the degree of drought in this region and affect plant growth and development,and thereby to threat the development of grassland animal husbandry.

An analysis of precipitation data from the Antarctic base Faraday/Vernadsky

AbstractA recent study on cloud observations reports an increase in total cloud cover at Faraday/Vernadsky since 1960 in the annual and wintertime data. The aim of this present study is to investigate whether this increase in total cloud cover has influenced the precipitation in this region. For this purpose, precipitation observations at the Antarctic base Faraday/Vernadsky between 1960 and 1999 were analysed. A positive trend, significant at the 5% level, was found in the number of precipitation events recorded during winter, showing an increase of 13 events per decade. The annual number of precipitation days has increased by 5.7 per decade during the period of investigation, with highest increase rates being observed in winter and autumn. The characteristics of these findings confirm that results previously published though trends presented here are ∼50% smaller due to a more thorough data quality control of the observational data. These results indicate that an increase in total cloud cover at Faraday/Vernadsky observed since 1960 in the annual and wintertime data is reflected in higher numbers of precipitation events and days. Analyses of the precipitation type found an increase in the proportion of events of non‐frozen precipitation, which is significant (1% level) on an annual basis as well as in spring and autumn (both significant at 5% level). This is a clear manifestation of the year round temperature increase observed over the Antarctic Peninsula. The increase in non‐frozen precipitation will have reduced the albedo in the region and will thus have contributed to the temperature‐albedo feedback. To refreeze rain that is draining through glaciers energy is extracted from the surrounding ice, thereby physically corroding the ice. This will have contributed to the observed retreat of glaciers around the Antarctic Peninsula. As non‐frozen precipitation falling on frozen ground cannot be stored but instead runs off, less water will be available for the ecosystem. Copyright © 2010 Royal Meteorological Society

Selecting a binary Markov model for a precipitation process

This paper uses rth-order categorical Markov chains to model the probability of precipitation. Several stationary and non-stationary high-order Markov models are proposed and compared using BIC. The number of parameters increases exponentially by adding the Markov order. Several classes of high-order Markov models are proposed which their increase of number of parameters are modest. For example models that use the number of precipitation days in a period prior to date, temperature of the previous day and sines/cosines periodic functions (to model the seasonality) are considered. The theory of partial likelihood is used to estimate the parameters. Parsimonious non-stationary first order Markov models with few seasonal terms are found optimal using BIC and temperature does not turn out to be a useful covariate. However BIC seems to underestimate the number of seasonal terms. We have also compared the results with AIC in some cases which tends to pick parsimonious models with more seasonal terms and higher order. We also show that ignoring seasonal terms result in picking higher order Markov chains. Finally we apply the methods to build confidence intervals for the probability of periods with no precipitation or low number of precipitation days in Calgary using historical data from 1980 to 2000.

Comparison of long‐term monitoring of temperature and precipitation between wetland and other ecosystems

AbstractAir temperature and precipitation changes in the decades 1961–2006 at Wet Meadows wetland ecosystem near Třeboň, South Bohemia were compared with the changes in these characteristics at other stations in the Czech Republic. Mean daily maximum air temperature measured during the vegetation growing season at wetland station Wet Meadows rose from 19·7 °C during the period 1961–1970 to 21·5 °C in the period 2001–2006 (i.e. 1·8 °C during 40 years). At Churáňov, a mountain forest station, this increase was from 14·7 to 15·8 °C (1·1 °C) and at Praha Ruzyně, a city station, the increase was from 20·0 to 20·7 °C (0·7 °C) during the same time. Mean number of precipitation days changed at Wet Meadows from 94·5 to 80·7 days per vegetation season, at Churáňov from 101·2 to 105·0 days per vegetation season and at Praha Ruzyně from 83·9 to 83·0 days per vegetation season during this time. We attribute the rise in temperature at Wet Meadows to a combined effect of climate change and a local change of the hydrological cycle. The disturbances in the short water cycle are attributed to the decrease in vegetation cover and the lack of water in the landscape. The consequent increase in the incoming direct solar radiation along with the rise in the heat coming into the area via precipitation as well as a decrease in and redistribution of precipitation events are considered major drivers of the meteorological changes that have resulted in the observed warming at Wet Meadows. Copyright © 2010 John Wiley & Sons, Ltd.

Evidence of Warming and Wetting Climate over the Qinghai-Tibet Plateau

In this study, we apply temperature, precipitation, and other data from 66 Chinese meteorological stations including Xining and Lhasa to analyze the extreme climate events and their impacting factors over the Qinghai-Tibet Plateau during the period 1961–2007. We focus on the spatial and temporal features of extreme climate events and their long-term changes over five climate zones of alpine grassland, meadow, and desert areas.Results show that, during the past decades, the changes in climate over the Qinghai-Tibet Plateau present trends towards warm and wet conditions. These changes in temperature and precipitation are evident in both seasonal means and extreme events, and the changes in precipitation are apparent in both precipitation amount and number of precipitation days. Clearly, warm and wet events increase, but cold and dry events decrease over the plateau region. Features of the warming climate are relatively consistent in spatial and seasonal distributions, with the most significant changes in winter and autumn and at nighttime. Northern Qinghai exhibits the greatest and most significant decrease in the frequency of extremely low-temperature events. However, the wetting trend shows more distinctive spatial features and is more seasonally dependent. While the trends in both precipitation amount and the number of precipitation days are positive in all climate zones for winter and spring, both positive and insignificant negative trends appear in summer and autumn. The largest decrease in the frequency of severely dry events is found over southeastern Tibet and western Sichuan.

Simulating low‐probability peak discharges for the Rhine basin using resampled climate modeling data

Climate change will increase winter precipitation, and in combination with earlier snowmelt it will cause a shift in peak discharge in the Rhine basin from spring to winter. This will probably lead to an increase in the frequency and magnitude of extreme floods. In this paper we aim to enhance the simulation of future low‐probability flood peak events in the Rhine basin using different climate change scenarios, and downscaling methods. We use the output of a regional climate model (RCM) and a weather generator to create long, resampled time series (1000 years) of climate change scenarios as input for hydrological (daily) and hydrodynamic (hourly) modeling. We applied this approach to three parallel modeling chains, where the transformation method from different resampled RCM outputs to the hydrological model varied (delta change approach, direct output, and bias‐corrected output). On the basis of numerous 1000 year model simulations, the results indicate a basin‐wide increase in peak discharge in 2050 of 8%–17% for probabilities between 1/10 and 1/1250 years. Furthermore, the results show that increasing the length of the climate data series using a weather generator reduced the statistical uncertainty when estimating low‐probability flood peak events from 13% to 3%. We further conclude that bias‐corrected direct RCM output is to be preferred over the delta change approach because it provides insight into geographical differences in discharge projections under climate change. Also, bias‐corrected RCM output can simulate changes in the variance of temperature and rainfall and in the number of precipitation days, as changes in temporal structure are expected under climate change. These added values are of major importance when identifying future problem areas due to climate change and when planning potential adaptation measures.

TREE-RING WIDTH AND STABLE CARBON ISOTOPE COMPOSITION OF JAPANESE CYPRESS IN THE LAKE BIWA AREA, CENTRAL JAPAN, AND THEIR HYDROLOGIC AND CLIMATIC IMPLICATIONS

Chronologies of tree-ring width and stable carbon isotope composition of Japanese cypress were developed to help reconstruct a 300-year record of past hydrologic and climatic environments in the Lake Biwa area, central Japan. Site chronologies were built with 37 trees for ring width and four trees for carbon isotope composition, respectively. Correlation analysis with monthly climatic data revealed that radial growth of the trees is related to temperature in early spring, precipitation (or number of precipitation days) in early summer and precipitation in previous-year summer to autumn. Tree-ring cellulose carbon isotopic composition is correlated most significantly with the number of precipitation days in early summer months. Consequently, a chronology of the number of precipitation days in May was reconstructed by multiple regression analysis with ring-width and carbon-isotope predictors and was validated by comparison with the recent observed record.