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With projected climate change, it is increasingly important to understand the current role of weather in everyday life and how it may change in the future. This paper evaluates two qualitative research approaches for their ability to generate insight into weather-related experiences and everyday practices. As these mundane day-to-day weather interactions often escape memory over time, the paper calls into question the ability of conventional methodological approaches that rely on recall to accurately excavate these events. The research examined serial one-on-one, semi-structured interviews with an adapted short-term focus, and daily diary-photographs. Each approach was applied to one of two Australian cities with sharply contrasting climates - Melbourne and Darwin. Both approaches were able to generate insight into weather-related experiences and practices. However, both presented problems. In interviews, these problems related to retrospective accounts beyond 'yesterday', where physical experience recollections became limited. For diary-photographs, inspiring participants to continually complete and submit contributions proved problematic. I argue that interviews are better for documenting routine practice and generalised experiences, while diary-photographs are better at showing fine-grained detail of physical experiences. Where both aspects are sought, as in this study, a combination is possible. However, using dual methods increases the risk of participant fatigue. [ABSTRACT FROM AUTHOR]

Microbursts are meteorological phenomena in the lower troposphere which can produce damaging surface winds and pose a severe risk to aircraft flying close to the ground. As these events usually span less than 4 km and 15 min, the spatiotemporal resolution is a challenge for numerical simulations. Although research of microburst using operative mesoscale models is scarce, the Weather Research and Forecasting (WRF) model has been used in the diagnosis of this phenomenon. In this paper, such model is used to simulate several microburst conducive days using two different boundary conditions. The energy spectra of the simulations are computed to evaluate the effective resolution of the model. The results are in line with previous studies and produce no notable differences among the boundary conditions. Nonetheless, the energy spectra show an overenergetic troposphere at microscale resolutions, rendering the effective resolution inadequate for microburst forecasting using the simulated physics variables. Thus, mesoscale indices are analyzed as a prognostic tool. The wind index, the wet microburst severity index and the microburst windspeed potential index do not show high forecasting performances, even though improving the results of climatology. Also, notable differences among the boundary conditions can be seen. The most consistent results are achieved by the wet microburst severity index. Key Points: The WRF model shows an unrealistic energy spectrum when microscale spatial resolutions are usedThe effective resolution of the simulations casts doubts over the ability to forecast microburstsWINDEX, WMSI, and MWPI microburst indices show better forecasting performance than climatology, despite being suboptimal in general terms [ABSTRACT FROM AUTHOR]

The Amazon River, its huge basin, and the changes in biological processes that are rapidly occurring in this region are unquestionably of global significance. Hence, Global Change Biology is delighted to host a special thematic issue devoted to the Large-scale Biosphere-Atmosphere Experiment in Amazônia (LBA), which is a multinational, interdisciplinary research program led by Brazil. The goal of LBA is no less modest than its subject: to understand how Amazônia functions as a regional entity in the Earth system and how these functions are changing as a result of ongoing changes in land use. This compilation of 26 papers resulting from LBA-related research covers a broad range of topics: forest stocks of carbon (C) and nitrogen (N); fluxes of greenhouse gases and volatile organic compounds from vegetation, soils and wetlands; mapping and modeling land-use change, fire risk, and soil properties; measuring changes caused by logging, pasturing and cultivating; and new research approaches in meteorology to estimate nocturnal fluxes of C from forests and pastures. Some important new synthesis can be derived from these and other studies. The aboveground biomass of intact Amazonian forests appears to be a sink for atmospheric carbon dioxide (CO2), while the wetlands and soils are a net source of atmospheric methane (CH4) and nitrous oxide (N2O), respectively. Land-use change has, so far, had only a minor effect on basin-wide emissions of CH4 and N2O, but the net effect of deforestation and reforestation appears to be a significant net release of CO2 to the atmosphere. The sum of the 100-year global warming potentials (GWP) of these annual sources and sinks of CH4, N2O, and CO2 indicate that the Amazonian forest-river system currently may be nearly balanced in terms of the net GWP of these biogenic atmospheric gases. Of course, large uncertainties remain for these estimates, but the papers published here demonstrate tremendous progress, and also large remaining hurdles, in narrowing these uncertainties in our understanding of how Amazônia functions as a regional entity in the Earth system. [ABSTRACT FROM AUTHOR]

The frequency and magnitude of extreme meteorological or hydrological events such as floods and droughts in China have been influenced by global climate change. The water problem due to increasing frequency and magnitude of extreme events in the humid areas has gained great attention in recent years. However, the main challenge in the evaluation of climate change impact on extreme events is that large uncertainty could exist. Therefore, this paper first aims to model possible impacts of climate change on regional extreme precipitation (indicated by 24-h design rainfall depth) at seven rainfall gauge stations in the Qiantang River Basin, East China. The Long Ashton Research Station-Weather Generator is adopted to downscale the global projections obtained from general circulation models (GCMs) to regional climate data at site scale. The weather generator is also checked for its performance through three approaches, namely Kolmogorov-Smirnov test, comparison of L-moment statistics and 24-h design rainfall depths. Future 24-h design rainfall depths at seven stations are estimated using Pearson Type III distribution and L-moment approach. Second, uncertainty caused by three GCMs under various greenhouse gas emission scenarios for the future periods 2020s (2011-2030), 2055s (2046-2065) and 2090s (2080-2099) is investigated. The final results show that 24-h design rainfall depth increases in most stations under the three GCMs and emission scenarios. However, there are large uncertainties involved in the estimations of 24-h design rainfall depths at seven stations because of GCM, emission scenario and other uncertainty sources. At Hangzhou Station, a relative change of −16% to 113% can be observed in 100y design rainfall depths. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding of how best to support those most vulnerable to climate stress is imperative given expected changes in climate variability. This paper investigates local adaptation strategies to climate variability, focusing on agricultural decision-making in a communal irrigation scheme in Vhembe District, Limpopo Province, South Africa. Research done through interviews, surveys and participatory methods demonstrates that adaptation strategies within a community are socially differentiated and present differing objectives and priorities. These results highlight the need for intervention and policy that support a heterogeneous response to a wide range of stresses. Evidence for climate change is clear and the need for adaptation is urgent. However, adaptation measures have to be sensitively integrated with ongoing development pathways to ensure they are sustainable and relevant to local priorities. [ABSTRACT FROM AUTHOR]

Downscaled regional climate simulations for Fiji and Federated States of Micronesia (FSM) from Coupled Model Intercomparison Project 3 (CMIP3) Global Coupled Models (GCMs) are carried out as part of the Pacific Climate Change Science Program (PCCSP) using the CSIRO stretched-grid Conformal Cubic Atmospheric Model (CCAM) for the period 1980-2000. The model simulations are performed at 60 km and at 8 km horizontal resolutions. The higher resolution is chosen to partly resolve the detailed orography of the countries selected, providing insight into the spatial distribution of temperature and precipitation for an individual island that GCMs are unable to represent. The downscaling is carried out in two steps. First, CCAM simulations are run on a global 60 km grid using bias-corrected sea surface temperatures (SST) and sea ice from six CMIP3 GCMs. Three of these 60 km simulations are then further downscaled to 8 km resolution over the two countries. The focus of this paper is validation of these high-resolution simulations against gridded analyses, satellite rainfall climatologies and available station data for rainfall and temperature for the period 1980-2000. The results show that high resolution orography plays an important role in capturing the current climate. The validation demonstrates that the 8 km simulations are capable of realistically depicting the current climate when the topography influences the wind flow and rainfall (Fiji), performing better than both the GCMs and the 60 km downscaled simulations. However, the performance of the 8 km simulations is similar to the GCM and 60 km simulations when topographical features are not present (FSM). [ABSTRACT FROM AUTHOR]

This paper presents an approach to model the expected impacts of climate change on irrigation water demand in a reservoir command area. A statistical downscaling model and an evapotranspiration model are used with a general circulation model (GCM) output to predict the anticipated change in the monthly irrigation water requirement of a crop. Specifically, we quantify the likely changes in irrigation water demands at a location in the command area, as a response to the projected changes in precipitation and evapotranspiration at that location. Statistical downscaling with a canonical correlation analysis is carried out to develop the future scenarios of meteorological variables (rainfall, relative humidity (RH), wind speed ( U2), radiation, maximum (Tmax) and minimum (Tmin) temperatures) starting with simulations provided by a GCM for a specified emission scenario. The medium resolution Model for Interdisciplinary Research on Climate GCM is used with the A1B scenario, to assess the likely changes in irrigation demands for paddy, sugarcane, permanent garden and semidry crops over the command area of Bhadra reservoir, India. Results from the downscaling model suggest that the monthly rainfall is likely to increase in the reservoir command area. RH, Tmax and Tmin are also projected to increase with small changes in U2. Consequently, the reference evapotranspiration, modeled by the Penman-Monteith equation, is predicted to increase. The irrigation requirements are assessed on monthly scale at nine selected locations encompassing the Bhadra reservoir command area. The irrigation requirements are projected to increase, in most cases, suggesting that the effect of projected increase in rainfall on the irrigation demands is offset by the effect due to projected increase/change in other meteorological variables (viz., Tmax and Tmin, solar radiation, RH and U2). The irrigation demand assessment study carried out at a river basin will be useful for future irrigation management systems. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding changes in evaporation rates is expected to be of great importance for water resource planning and management. This paper examines pan evaporation data as an example of the detection and attribution of trends in climate variables. Records of pan evaporation ( Epan), rainfall ( R), radiation ( SR), wind speed ( WS), temperature ( Ta) and humidity ( RH) for the period 1973-2008 were collected from the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. Mann-Kendall trend and Sen's slope tests were performed on the respective meteorological variables and a variability index (VI) was also computed for these. The results showed that annually Epan, SR and WS significantly decrease ( P < 0.001) while R, Ta, and RH showed insignificant increasing trends in the last four decades. Epan and SR decrease at the rate of 8.3 mm year−2 and 37.8 MJ m−2 year−1, respectively. Similar to Epan, SR decreased significantly in all the months ( P < 0.01) and the reduction ranged from 5.1% per decade in March to 9.3% per decade in August. The result of VI showed that the decrease in Epan and other explanatory variables is rather recent. Regression between Epan and other variables indicates that about 30, 15 and 6% of its variance can be explained by SR, WS and VPD (vapour pressure deficit), respectively. The possible roles of dust-haze known as 'harmattan' winds and monsoon clouds in attenuating SR and hence reducing Epan are discussed. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This paper traces the history of the use of ships' logbooks in climatological studies from the earliest days of the 17th century to the present day. Although early theories concerning global air circulations by Halley and Hadley were based on information gathered by mariners and recorded in their logbooks, it has only been in the last two decades that interest has returned to this important, but long-overlooked, source of climatic information. Attention is drawn to the many advantages offered by logbooks, in particular the long period of time that they collectively cover, their near-global geographic range, the large number of such documents that have survived, and the degree of detailed and reliable record that they provide. Before the mid-19th century, much of the recorded information is noninstrumental in character but its scientific potential is reflected in the variety of approaches and methods that have been used in its analysis and in the equally wide range of outcomes, from databases to synoptic charts and long-time series indices that have emerged from the most recent research. Attention is also drawn to the benefits to be derived from old and more recent instrumental logbook data. As only a small percentage of the tens of thousands of logbooks that have been preserved have thus far been examined, the potential for yet further development is enormous. [ABSTRACT FROM AUTHOR]

Cut-off low pressure systems (COLs) are defined as closed lows in the upper troposphere that have become completely detached from the main westerly current. These slow-moving systems often affect the weather conditions at the earth's surface and also work as a mechanism of mass transfer between the stratosphere and the troposphere, playing a significant role in the net flow of tropospheric ozone. In the first part of this work we provide a comprehensive summary of results obtained in previous studies of COLs. Following this, we present three long-term climatologies of COLs. The first two climatologies are based on the conceptual model of a COL, using European Centre for Medium-range Weather Forecasts (ECMWF) analyses (1958–2002) and National Centers for Environmental Prediction–National Center for Atmospheric Research (1948–2006) reanalysis data sets. The third climatology uses a different method of detection, which is based on using potential vorticity as the physical parameter of diagnosis. This approach was applied only to the ECMWF reanalysis data. The final part of the paper is devoted to comparing results obtained by these different climatologies in terms of areas of preferential occurrence, life span, and seasonal cycle. Despite some key differences, the three climatologies agree in terms of the main areas of COL occurrence, namely (1) southwestern Europe, (2) the eastern north Pacific coast, and (3) the north China–Siberian region. However, it is also shown that the detection of these areas of main COL occurrence, as obtained using the potential vorticity approach, depends on the level of isentropic analysis used. [ABSTRACT FROM AUTHOR]

This month’s issue focuses on the meteorological effects of solar eclipses using data collected in the UK on 20 March 2015 and the USA on 21 August 2017. We begin with Edward Hanna’s examination of data from stations run by amateur enthusiasts, most of them in the Climatological Observers’ Link network. ‘Meteorological effects of the 20 March 2015 solar eclipse over the United Kingdom’ on p. 71 builds on the observations made at Met Office stations, published in Clark ( ) and Hanna et al. ( ). The observations show a high degree of consistency and the reduction in solar radiation had a strong signal in all parts of the UK, even where there were cloudy skies in most southern, as well as many northern and eastern areas. It also adds to the effects reported in this journal, following the eclipse of 11 August 1999 (Hanna, ). Bob Bourton’s short contribution ‘The thermal effects noticed at Heathrow Airport during the partial solar eclipse of 20 March 2015 ‘on p. 81 looks at the effects of the 2015 eclipse at Heathrow Airport. The range of instruments available across the airport and in roads leading to it gives further insight into the temperature and radiation changes during the obscuration of 85% of the sun’s disk in the west of London. On p. 90, we move to the observations made in the USA under the swathe of total or near‐total eclipse on 21 August 2017 in ‘Meteorological impacts of the total solar eclipse of 21 August 2017’, as reported by Stephen Burt. The data from sites run by the National Oceanic and Atmospheric Administration (NOAA, ) are supplemented by observations made by Stephen Burt near Jackson, Wyoming. Because the path of this eclipse crossed much of the USA and could be observed at least partially in all parts of the country, this was probably the best observed eclipse in history. Under clear skies, falls of about 5 degC were seen, accompanied by a fall in wind speed, now known from observations on both sides of the Atlantic to be a significant effect of this short‐duration phenomenon. We also include a seasonally‐appropriate look at the effects of year‐to‐year weather on plants and animals on p. 86. Ian Strangeways’ paper ‘Phenology: plants and animals as meteorological sensors’, gives us an overview of this subject, which used to be one of the activities of the Royal Meteorological Society. He includes the history of its development in the UK, as well as its value in weather science and our knowledge of the effects of changing climate. [ABSTRACT FROM AUTHOR]

In the first part of this paper existing evidence (mostly from earth and atmospheric sciences) on global climatic changes and their dependence (and effect) upon human action is briefly reviewed. Reference is made to existing major international programmes of research focusing on these climatic changes. The main part of the paper concentrates on the study of global change within the framework of the social sciences. Five psychological characteristics of global environmental change are explained which would account for the human inability to respond adequately without the supportive means of information presentation and processing. Future research on psychological dimensions of global change should explore these in greater detail and study modes of social communication that will become instrumental in implementing such support systems. [ABSTRACT FROM AUTHOR]

We assess the Asian summer monsoon anticyclone (ASMA) in Coupled Model Intercomparison Project Phase 6 (CMIP6) models for the historical period (1850–2014). The ASMA is a quasi‐stationary warm anticyclone during the boreal summer monsoon season, centred around Tibet. It is a prominent circulation feature that affects trace species transport, stratosphere–troposphere exchange, along with strong feedbacks to weather and climate. The study is a novel attempt to quantify the performance of models participating in the CMIP6 consortium and understand long‐term variability and teleconnections of the ASMA. We note that CMIP6 models capture the mean ASMA features reasonably well, albeit with some differences around the edges. For most of the models, interannual variations are not in phase with the reanalysis and show sharper increasing trend in the ASMA strength. There is about a twofold increase in the trends during the recent period (1980–2014) as compared to the 1950–2014 period. A multimodel mean (MME) chosen based upon the statistical metrics (mean, standard deviation, mean absolute error and root‐mean‐square error), target diagram, and density distributions is further used to examine the prominent modes of variability. Our results suggest that the signals of significant periodicity, particularly the 2–4 years signal, and the SST correlations in MME are inconsistent with observations. In CMIP6 models, we note stronger upper level divergence over the western and eastern Pacific but convergence over the Indian ocean, South Asia and the central Pacific. The streamfunction and rotational winds also show strong highs north of 20°N. Overall, it is seen that basic features such as spatial extent and evolution of ASMA are reasonably captured, but the strength and interannual variations are dissonant across the CMIP6 models. These findings are useful for studies focusing on regional meteorology, transportation of atmospheric tracers and climate change projections over the region involving the ASMA. [ABSTRACT FROM AUTHOR]

Ships' logbooks have been preserved in archives of different European countries. This paper reviews how their records provide reliable information relevant to meteorology and climatology, extending the observational record back to at least the early 18th century. This allows describing weather during historical events, improving the knowledge on hurricanes or unveiling multidecadal variability previously unsuspected, such as the steady enhancement of the Australian monsoon, the high variability of the atmospheric circulation over the Euro‐Atlantic region during the Late Maunder Minimum or the relationship between the Western North Pacific Summer Monsoon and the El Niño—Southern Oscillation. Observations from ships can feed long‐term reanalysis projects and contribute to reduce their uncertainties over the oceans. The extended record of observations also aids the search of analogues before the human fingerprint, thus improving the detection and attribution of climate change. The integration with paleoclimate proxies is a complex task that requires merging heterogeneous records with a wide range of time resolutions, spatial density, and responses to the climate system. However, recent international efforts open the field to new opportunities. Summing up, logbooks are a consistent, but underexploited, source of relevant climatic data that will widen our knowledge of the past climate. This in turn provides a way to better understand present climatic variations and predict future changes. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change Ships' logbooks help to understand climate variability of the last 300 years. [ABSTRACT FROM AUTHOR]

Understanding past changes in precipitation extremes could help us predict their future dynamics. We present a novel approach for analyzing trends in extremes and attributing them to changes in the local precipitation regime. The approach relies on the separation between intensity and occurrence of storms. We examine the relevant case of the Eastern Italian Alps, where significant trends in extreme precipitation were reported. The model is able to reproduce the observed trends at all durations between 15 min and 24 hr, and allows us to quantify trends in extreme return levels. Despite the significant increase in storm occurrence and typical intensity, the observed trends can be only explained considering changes in the tail heaviness of the intensity distribution, that is the proportion between heavy and mild events. Our results suggest that the observed changes are caused by an increased proportion of summer convective storms. Plain Language Summary: Quantifying past trends in extreme rainfall is important because it can help us understand future changes caused by global warming. Climate scientists and hydrologists use specific statistical models to do so, but interpreting the results is complicated because extremes are rare and the structure of the models is not linked to the local meteorology. We use a new statistical model that allows to better understand the mechanisms behind the trends we detect. We find that rainfall extremes in the Eastern Italian Alps increased over the past decades and we associate this change to an increased proportion of summer thunderstorms. Key Points: We present a method for analyzing extreme precipitation trends based on the separation of storm intensity and occurrence frequencyOur approach reproduces observed trends in annual maxima and allows to quantify trends on rare return levelsObserved trends in the Eastern Italian Alps are explained by an increased proportion of heavy convective storms in the summer [ABSTRACT FROM AUTHOR]

The article presents a study on the climatic fluctuation during the early 20th century. It states that study was guided by review of papers from scientists investigated the climatic fluctuation and its relevance to the continuous climate change. Results show anomaly patterns in the surface air temperature (SAT), sea surface temperature (SST) and related ecosystem that causes anthropogenic climate disturbance attributed to atmospheric circulation.

Recently, the search for evidence of climate‐change impacts has been intense. Long‐term and not so very long‐term data are being examined for evidence of climatic response. Three commonly used methods involve (i) correlation with an ever‐increasing number of climatic variables, (ii) examining trends through time and (iii) a comparison between two points in time. In this paper we provide examples designed to emphasize the need for impassionate and critical examination of findings, the so‐called ‘eclectic’ approach, involving a combination of empirical and conceptual evidence. Copyright © 2005 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

In recent years, Kilimanjaro and its vanishing glaciers have become an ‘icon’ of global warming, attracting broad interest. In this paper, a synopsis of (a) field observations made by the authors and (b) climatic data as reported in the literature (proxy and long-term instrumental data) is presented to develop a new concept for investigating the retreat of Kilimanjaro's glaciers, based on the physical understanding of glacier–climate interactions. The concept considers the peculiarities of the mountain and implies that climatological processes other than air temperature control the ice recession in a direct manner. A drastic drop in atmospheric moisture at the end of the 19th century and the ensuing drier climatic conditions are likely forcing glacier retreat on Kilimanjaro. Future investigations using the concept as a governing hypothesis will require research at different climatological scales. Copyright © 2004 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This paper reviews our understanding of how the effects of the El Niño–southern oscillation (ENSO) might be transmitted from the tropical Pacific Ocean to the Antarctic, and examines the evidence for such signals in the Antarctic meteorological, sea ice, ice core and biological records. Many scientific disciples concerned with the Antarctic require an understanding of how the climatic conditions in the tropical and mid-latitude regions affect the Antarctic, and it is hoped that this review will aid their work. The most pronounced signals of ENSO are found over the southeast Pacific as a result of a climatological Rossby wave train that gives positive (negative) height anomalies over the Amundsen–Bellingshausen Sea during El Niño (La Niña) events. However, the extra-tropical signature can sometimes show a high degree of variability between events in this area. In West Antarctica, links between ENSO and precipitation have shown variability on the decadal time scale. Across the continent itself, it is even more difficult to relate meteorological conditions to ENSO, yet analyses of the long meteorological records from the stations do indicate a distinct switch in sign of the pressure anomalies from positive to negative across the minimum in the southern oscillation index. The oceanic signals of ENSO around the Antarctic are less clear, but it has been suggested that the Antarctic circumpolar wave could be forced by the phenomenon. Ice-core data offer the potential to help in understanding the long-term relationship between ENSO and the climate of the Antarctic, but there are difficulties because of the need to smooth the ice-core data to overcome the mixing of snow on the surface. Nevertheless, analysis of methylsulphonic acid in a South Pole core has shown high variability on ENSO time scales. It is clear that some evidence of ENSO can be found in the Antarctic meteorological and ice-core records; however, many of the relationships tend not to be stable with time, and we currently have a poor understanding of the transfer functions by which such signals arrive at the Antarctic from the tropical Pacific. Copyright © 2004 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

We analyse seasonal and annual trends of extreme indices of air temperature and precipitation over Brazil during the period 1961–2018. The main goal is to investigate whether the climate is changing and if so, to explore if there is any marked seasonality in such changes. The daily observed datasets of maximum and minimum temperatures, and precipitation, are provided by the Brazilian National Institute of Meteorology and National Water Agency. We use the Sen Curvature and Mann‐Kendall statistical tests to compute the magnitudes and to evaluate the statistical significance of climate extremes trends, respectively. The results show that the warm extremes frequency of occurrence is increasing significantly while the opposite occurs for cold extremes, which reveals a very consistent and widespread warming over Brazil. The highest increases in warm extremes occur during austral spring and summer while for the cold extremes the greatest decreases are observed during austral winter. Unlike temperature, precipitation extremes show heterogeneous signals for most of the country. In Northeast Brazil, there are changes towards a drier climate, especially in summer and autumn. In the Southern region, the climate is becoming wetter, with a reduction in consecutive dry days, especially in spring. For the other regions, there is no strong clear change sign, but both positive and negative precipitation extreme trends, without statistical significance (mostly in Southeast Region). [ABSTRACT FROM AUTHOR]

This paper presents work from a geomorphological investigation carried out in the Aradena Gorge, southwestern Crete, Greece. The gorge is typical of many steepland fluvial systems in the Mediterranean, with steep relief, coarse-gravel sediments and high rates of sedimentation generated during intense winter storm events. Hillslope deposits and coarse-gravel flood units within a 5 km section of the gorge have been mapped, dated (using lichenometry and dendrochronology), and their sedimentological characteristics recorded to establish a c. 200-year record of flood frequency/magnitude and hillslope/channel sediment supply variability. This record has been compared with instrumented and previously published records of climate change from Crete and the Mediterranean region and used to establish the major controls on flooding and sediment dynamics within the Aradena Gorge. Rates of colluviation and sediment delivery to the channel appear to have been greater than the present sometime before c. AD 1800 and may be related to cooler climates with a more seasonal precipitation regime during the Little Ice Age (c. AD 1450 to 1850). In gorge sections where the present rate of sediment supply from hillslope colluvium is very low, the channel has incised into older alluvial and colluvial deposits. Conversely, in the few sections where sediment supply is currently very high, the channel is aggrading with a braided pattern. Major rock-fall deposits at certain locations in the gorge have restricted any major downstream sediment transfer. Twelve periods of increased flooding during the last 150 years have been identified and these correlate quite well with negative or declining phases of the North Atlantic Oscillation (NAO). Analysis of daily precipitation data from Crete suggests negative phases of the winter NAO are characterized by an increase in the number of long-duration, high-intensity storms. These storms, particularly those with five-day and greater duration, appear to be significant in triggering major floods in the Aradena Gorge. During the last 40 years the NAO index has been increasing and become locked into a positive phase. As a consequence of this, major flooding appears to have declined during the same period. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

One of the most significant forecasting problems facing meteorologists in the Sydney office of the Australian Bureau of Meteorology is the prediction of the heavy to extreme rainfall amounts that occur on the subtropical north coast of New South Wales (NSW). The significance of the problem lies in the great intensity of the rainfall, the difficulty in predicting the formation, location and duration of the rainfall, and the impacts of flooding on both cities and communities. The forecasting difficulties arise because of the small scales often involved, the range of physical mechanisms responsible and the challenge involved in forecasting events of such short duration. In the case of flash floods, the intense rainfall is typically less than 6 h in duration. Operational numerical weather prediction (NWP) has not shown much success, mainly because of the reasons mentioned above, especially given that computational limitations restrict its model resolutions. In this paper, the synoptic situation is presented for the most severe flash flood on record to affect Coffs Harbour, a city which is located on the NSW mid-north coast. The event, which occurred on the evening of 23 November 1996, is rated approximately as a 1 in a 100-year intensity/duration event. A 25-year climatology subset of flood-producing systems that have affected Coffs Harbour is then presented, and is correlated with the Southern Oscillation Index (SOI). Finally, details are given for a numerical modelling case study of the flash flood. The model results reveal that a very accurate prediction of the amount and the spatial distribution of rainfall amounts can be made for an event of this type. The rainfall totals of over 500 mm in 24 h were accurately forecast using coarse resolution archived operational initial analyses. The success of the predictions is most likely owing to the dominance of large-scale dynamical processes, which were further focused by the steep topography. Copyright © 2000 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Interest in climatic change has never been greater and it is inevitable that the search for periodicities in the climatic record should be a popular means of attempting to unravel at least some of the complexities of the atmospheric system. This paper reviews aspects of the methodologies of spectral analysis and takes the example of the Barcelona precipitation series (1850–1991) to illustrate how both spectral analysis and other statistical analyses can provide information on climatic evolution as expressed through the medium of this one variable. Copyright © 1999 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Active layer probing in northern Sweden, northeast Greenland, and central Svalbard indicates active layer thickening has occurred at Circumpolar Active Layer Monitoring (CALM) sites with long‐term, continuous observations, since the sites were established at these locations in 1978, 1996, and 2000, respectively. The study areas exhibit a reverse latitudinal gradient in average active layer thickness (ALT), which is explained by site geomorphology and climate. Specifically, Svalbard has a more maritime climate and thus the thickest active layer of the study areas (average ALT = 99 cm, 2000–2018). The active layer is thinnest at the northern Sweden sites because it is primarily confined to superficial peat. Interannual variability in ALT is not synchronous across this Nordic Arctic region, but study sites in the same area respond similarly to local meteorology. ALT correlates positively with thawing degree days in Sweden and Greenland, as has been observed in other Arctic regions. However, ALT in Svalbard correlates with freezing degree days, where the maritime Arctic climate results in relatively high and variable winter air temperatures. The difference in annual ALT at adjacent sites is attributed to differences in snow cover and geomorphology. From 2000 to 2018, the average rate of active layer thickening at the Nordic Arctic CALM probing sites was 0.5 cm/yr. The average rate was 1 cm/yr for Nordic Arctic CALM database sites with significant trends, which includes a borehole in addition to probing sites. This range is in line with the circum‐Arctic average of 0.8 cm/yr from 2000 to 2018. [ABSTRACT FROM AUTHOR]

There have been speculations that the severe air pollution experienced in North China was the act of meteorological change in general and a decreasing northerly wind in particular. We conduct a retrospective analysis on 1979–2016 reanalysis data from ERA‐Interim of European Centre for Medium‐Range Weather Forecasts over a region in North China to detect meteorological changes over the 38 years. No significant reduction in the northerly wind within the mixing layer is detected. Statistically significant increases are detected in the surface temperature, boundary layer height and dissipation, and significant decreases in relative humidity in the region between the first and second 19‐year periods from 1979 to 2016. We build regression models of PM2.5 on the meteorological variables using data in 2014, 2015, and 2016 to quantify effects of the meteorological changes between the two 19‐year periods on PM2.5 under the emission scenarios of 2014–2016. It is found that despite the warming, dew point temperature had been largely kept under control as the region had gotten dryer. This made the effects of temperature warming largely favorable to PM2.5 reduction as it enhances boundary layer height and dissipation. It is found that the meteorological changes would lead to 1.29% to 2.76% reduction in annual PM2.5 averages with January, March, and December having more than 4% reduction in the 3 years. Thus, the meteorological change in North China had helped alleviate PM2.5 to certain extent and should not be held responsible for the regional air pollution problem. Key Points: Meteorological changes led to 1.9% to 2.7 percent% reduction in annual PM2.5 averages over North China 2014 to 2016 driven by temperature warmingSignificant increases are detected in the surface temperature, boundary layer height, and dissipation and decreases in relative humidityThe meteorological change should not be held responsible for the regional air pollution problem in North China [ABSTRACT FROM AUTHOR]

Quantifying the influence of sea spray on air‐sea fluxes under high‐wind conditions is challenging due to a variety of factors. Among existing models, the so‐called bulk air‐sea flux model is commonly used in meteorological applications due to its simplicity, which often involves strong but untested assumptions on spray‐mediated heat fluxes and feedback effects. For example, a common assumption is to treat each droplet size as an independent contribution; that is, it does not interact with other sizes. Thus, the interactions between different size classes of spray are often neglected. In this study, we focus on the polydispersity of the spray size distribution and investigate the appropriateness of assuming an independent contribution from different spray size classes. We implement direct numerical simulations (DNS) with Lagrangian tracking of spray droplets. Based on DNS results, the bulk spray model fails to capture the interactions between different sizes that are observed directly from the droplet and feedback statistics in DNS. Thus, assuming independent contributions from spray droplets results in significant overestimates on the total heat fluxes. We further test different representative sizes of a spray size distribution. We find that the volume‐weighted representative size is capable of predicting the droplet‐modified temperature and humidity fields and generally captures the vertical profiles of spray‐mediated and interfacial heat fluxes. The results indicate that the computation of spray‐mediated fluxes can be simplified in large‐scale parameterizations. Key Points: Directly adding all contributions from spray droplets in bulk models may introduce overestimates on spray‐mediated heat fluxesWe improved the overestimation issue in bulk model for the total heat flux by considering the effects of spray time scalesUsing the volume‐weighted mean size as a representative size could simplify the quantifying of air‐sea fluxes in an Eulerian framework [ABSTRACT FROM AUTHOR]

Variable‐resolution global climate models (VRGCMs) are a dynamical downscaling method that can reach spatiotemporal scales needed for regional climate assessments. Over the years, several users of VRGCMs have assumed where the location and extent of the refinement domain should be based on knowledge of the prevailing storm tracks and resolution dependence of important regional climate processes (e.g., atmospheric rivers [ARs] and orographic uplift), but the effect of high‐resolution domain size and extent on the simulation of downstream hydroclimatic phenomena has not been systematically evaluated. Here, we use variable resolution in the Community Earth System Model (VR‐CESM) to perform such a test. To do this, three VR‐CESM grids were generated that span the entire, two thirds, and one third of the North Pacific and evaluated for a 30‐year climatology using Atmospheric Model Intercomparison Project protocols. Simulations are compared with reanalysis products offshore (fifth‐generation of the European Centre for Medium‐Range Weather Forecasts atmospheric reanalysis [ERA5]) and onshore (Livneh, 2015, https://doi.org/10.1038/sdata.2015.42, and Parameter‐elevation Regressions on Independent Slopes Model [PRISM]) of the western United States. The westward expansion of refinement domain influenced integrated vapor transport (IVT), which was generally high biased but minimally impacted AR characteristics. Due to slight differences in landfalling AR counts in the western United States, California winter precipitation generally improved with westward expansion of the refinement domain. Western U.S. mountain snowpack and surface temperatures were insensitive to refinement domain size and were more influenced by changes in topographic resolution and/or land surface model version. Given minimal dependence of simulated western U.S. hydroclimate on refinement domain size over the North Pacific, we advise future VR‐CESM studies to focus grid resolution on better resolving land surface heterogeneity. Key Points: Three variable‐resolution Community Earth System Model simulations are assessed for sensitivities to refinement domain sizeMore extensive refinement of the western Pacific reduces the integrated water vapor transport bias to the western United StatesTopographic resolution and land surface model have greater influences on simulated hydroclimatology than refinement domain extent [ABSTRACT FROM AUTHOR]

Hygroscopicity of aerosol (κchem) is a key factor affecting its direct and indirect climate effects, however, long‐term observation in Delhi is absent. Here we demonstrate an approach to derive κchem from publicly available data sets and validate it (bias of 5%–30%) with long‐term observations in Beijing. Using this approach, we report the first estimation of κchem in Delhi and discuss its climate implications. The bulk‐averaged κchem of aerosols in Delhi is estimated to be 0.42 ± 0.07 during 2016–2018, implying a higher activation ability as cloud condensation nuclei in Delhi compared with Beijing and continental averages worldwide. To activate a 0.1‐μm particle, it averagely requires just a supersaturation of ~0.18% ± 0.015% in Delhi but ~0.3% (Beijing), 0.28%–0.31% (Asia, Africa, and South America) and ~0.22% (Europe and North America). Our results imply that representing κchem of Delhi using Asian/Beijing average may result in a significant underestimation of aerosol climate effects. Plain Language Summary: Hygroscopic water uptake of aerosols can enhance its light extinction and cloud activation. Therefore, hygroscopicity of aerosol (κchem) is a key factor affecting its direct and indirect climate effects; however, long‐term observation of κchem in Delhi is absent. Here we demonstrate an approach to retrieve κchem from publicly available data sets of PM2.5 and meteorology and report the first long‐term estimation of κchem in Delhi is 0.42 ± 0.07 during 2016–2018. This value indicates only a supersaturation of ~0.18% ± 0.015% is required to activate a particle with 0.1‐μm diameter in Delhi, in contrast to ~0.3% supersaturation is required for Beijing and Asian average. It implies a higher water uptake and cloud activation ability for Delhi aerosols. Therefore, using Asian/Beijing averaged κchem to represent Delhi aerosols would lead to a significant underestimation of aerosol climate effects. Key Points: For the first time, we estimate the hygroscopicity of aerosols in Delhi (κ = 0.42 ± 0.07), based on 3‐year (2016‐2018) ground observationsHygroscopicity of aerosols in Delhi is much higher than Beijing and Asian average, therefore leading to remarkable climate effectsWe demonstrate a valuable method for deriving bulk‐averaged hygroscopicity of aerosol based on publicly available data sets [ABSTRACT FROM AUTHOR]

A nonlinear method has been developed to estimate climate feedbacks based on the Neural Network (NN) taking advantage of its self‐learning skills. The NN model developed here is trained using a reanalysis data set and predicts radiation flux globally from atmospheric and surface variables. The radiative feedbacks of temperature, water vapor, surface albedo, and cloud in the interannual climate variations estimated from the NN method are in agreement with those from a broadly used kernel method. However, the NN method demonstrates significant advantages: (1) it withdraws the linearity assumption of the kernel method and accounts for the nonlinear effects of the feedbacks. In the case of large climate perturbations, such as that in the Arctic caused by sea ice melt, the NN method achieves better radiation closure. (2) The method can directly calculate the radiative feedback of cloud and its components. We find that the high, middle, and low cloud feedback components analyzed from the NN method are linearly additive in the interannual climate variations, although there is a considerable nonlinear effect arising from the interactions between cloud and noncloud variables. Key Points: A nonlinear Neural Network (NN) method has been developed to estimate climate feedbacksThe NN method accounts for the nonlinear effects of the feedbacks and achieves good radiation closureThe NN method can directly calculate the radiative feedback of cloud and its components [ABSTRACT FROM AUTHOR]

Birds are sensitive to climate variability and change. This pilot study explores variations in bird communities in India under contrasting phases of the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Statistical analyses were performed using monthly bird data for the years 1990–2015 in Goa and Tamil Nadu. Monthly precipitation, temperature, the Oceanic Niño Index and the Dipole Mode Index were used as explanatory variables for species richness and counts of three marker species (Brahminy Kite, Indian Pond Heron and Lesser Whistling Duck). Due to highly autocorrelated series, small sample sizes and many test permutations, there is greater likelihood of Type I errors when interpreting correlation results. However, pooling bird data by climate mode and state revealed that species richness was generally greater under El Niño or negative IOD (locally wet conditions) than under La Niña or positive IOD (locally dry conditions). In Goa, the Brahminy Kite, Indian Pond Heron and Lesser Whistling Duck had significantly higher counts during El Niño than La Niña events. In Tamil Nadu, there were significantly more Kites under negative than positive IOD phases. Regional variations in sensitivity may reflect species‐dependent factors such as food availability and security of nesting sites. Further research is needed to establish causal mechanisms between climate mode and species richness as well as into the combined effects of ENSO and IOD on bird communities across South Asia. [ABSTRACT FROM AUTHOR]

ABSTRACT: The northeast monsoon (NEM) over south India plays a vital role in producing light and moderate rainfall events during October through December. Excess NEM rainfall is mainly due to the intensified tropical cyclones and easterly waves from the Pacific east–west troughs over the Bay of Bengal. The main heat source and sink regions of this monsoon season are the western Pacific high and the Siberian high, respectively. Relative variations in the areal extent and intensity of these source and sink regions influence the NEM season by excess or deficient rainfall. Hence, the aim of the present study was to observe the impact of the Siberian high and the western Pacific high on the NEM rainfall in excess and deficient years. For this purpose, dynamic and thermodynamic parameters, the zonal and meridional winds, the velocity potential, the sea surface temperature and the relative humidity of the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalysis data were used for the period 1951–2014. Analysis of these variables revealed the importance of the source and sink regions for the enhancement/reduction of NEM rainfall during excess/deficient years. [ABSTRACT FROM AUTHOR]

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ABSTRACT: Current changes in global climate are likely to be evident at both the regional and the local scale. This study presents an investigation in climatic trends in the KwaZulu‐Natal (KZN) midlands, South Africa and seeks to assess the level of change in the microclimate and more specifically, the influence of a changing climate on fire danger. To this end, long‐term (1953–2015), historical daily meteorological data from the KZN midlands were analysed, using multitemporal regression analysis as well as time‐series analysis. Analysis indicated significant trends, to varying rates of change, across all sites. Over the last two decades, annual average air temperature was found to be increasing at a rate of between 1 and 3 °C century−1. Atmospheric water vapour pressure across the three sites also experienced significant levels of change. Decreases in total rainfall over the last two decades are of concern. Fire danger, calculated using the Lowveld fire danger index (LFDI), displayed significant rates of change. At two sites, annual average fire danger, over the last two decades, was found to be decreasing at a rate between roughly 5 and 10 FDI units century−1. The onset and length of the KZN midlands fire season has also undergone significant changes, as a response to changes in the microclimate. Sites experienced an overall decreasing trend in the onset of the fire season – indicative of an earlier start to the fire season, as well as an increase in fire season length. Results indicate that while the microclimate of the KZN midlands is changing, the rate of change differs from that of global and continental estimates. [ABSTRACT FROM AUTHOR]

ABSTRACT Based on the daily mean air temperature at 1863 meteorological stations over China from 1961 to 2015, the temporal and spatial tendencies in the growing season parameters (the start date of the growing season, GSS; the end date of the growing season, GSE; and the length of the growing season, GSL) for 0, 3, 5 and 10 °C temperature thresholds were investigated; the results showed that in the past 55 years GSL exhibited a significant extending trend at speeds of 1.5-5.0 days per 10 years in most areas of northwest China ( NWC), north China ( NC), northeast China ( NEC) and western southwest China ( SWC). The extension of GSL was attributed to an earlier GSS at a rate of 1.5-3.0 days per 10 years in most areas of NEC and NC and some parts of NWC and SWC, and a later GSE at speeds of 1.0-2.0 days per 10 years in most of NWC and northern SWC and some parts of NEC and northwestern NC. The extending trend of the GSL was prominent in northern and western China relative to southern China. The temporal variations in the regional average growing season parameters were different for four temperature thresholds and in six regions. In general, the regional GSL ( GSS, GSE) was extended (advanced, delayed) continuously during 1961-2015 or had no significant trend before about 1980 and then extended (advanced, delayed) continuously. The temporal variations of the GSE were weaker than those of the GSS in most regions. [ABSTRACT FROM AUTHOR]

ABSTRACT Future changes in extreme rainfall arising from climate change may have a significant influence on flood and water erosion control and management strategies to a great extent. The maximum daily rainfall time series were projected for 2020-2049 using six general climate models and two scenarios through artificial neural networks for 22 stations across the north of Iran. The results indicate a reduction of between −3.0 and −0.2% in maximum rainfall for the selected stations and five out of six of the general climate models. The changes in the frequency and magnitude of extreme rainfall were then investigated by fitting a generalized extreme value distribution to the historical (from 1981 to 2010) and projected maximum rainfall. The location parameter of the generalized extreme value distribution fitted to the projected maximum rainfall does not show a significant change while the scale and shape parameters exhibit significant changes compared to the historical period. Estimating the 2, 50 and 100 year return periods showed that the maximum rainfall will have a reduction in the probability of large amounts across the region compared with the base period while the number of extraordinary extreme events may show growth. As a region vulnerable to flash floods and water erosion due to rainfall characteristics and land use change from forest to agriculture, the results may send an alarm to define long term and effective strategies for future flood control management in the region. [ABSTRACT FROM AUTHOR]

For water-resource planning, sensitivity of freshwater availability to anthropogenic climate change ( ACC) often is analyzed with 'offline' hydrologic models that use precipitation and potential evapotranspiration ( Ep) as inputs. Because Ep is not a climate-model output, an intermediary model of Ep must be introduced to connect the climate model to the hydrologic model. Several Ep methods are used. The suitability of each can be assessed by noting a credible Ep method for offline analyses should be able to reproduce climate models' ACC-driven changes in actual evapotranspiration in regions and seasons of negligible water stress ( Ew). We quantified this ability for seven commonly used Ep methods and for a simple proportionality with available energy ('energy-only' method). With the exception of the energy-only method, all methods tend to overestimate substantially the increase in Ep associated with ACC. In an offline hydrologic model, the Ep-change biases produce excessive increases in actual evapotranspiration ( E), whether the system experiences water stress or not, and thence strong negative biases in runoff change, as compared to hydrologic fluxes in the driving climate models. The runoff biases are comparable in magnitude to the ACC-induced runoff changes themselves. These results suggest future hydrologic drying (wetting) trends likely are being systematically and substantially overestimated (underestimated) in many water-resource impact analyses. [ABSTRACT FROM AUTHOR]

ABSTRACT Accurate forecasts of fog and visibility are important for many applications; while prolonged fog can adversely affect many crops, even a short duration of dense fog can lead to disruption of air and highway traffic. The genesis and dynamics of fog are a result of many processes; accurate forecasting of fog thus continues to be a challenge. A forecast model of the occurrence of fog, measured in terms of visibility, is presented. The model is formulated as an analogue model; thus the merit of the model is primarily based on its validation against observation. Two forecasts using two sets of meteorological fields are considered: one as the benchmark forecasts with visibility calculated from observed meteorological fields and the other based on meteorological forecasts from an atmospheric mesoscale model ( Weather Research and Forecasting). While the benchmark (perfect) forecasts from observed meteorological fields provide the potential skill of the model, the mesoscale forecasts provide an assessment of realizable skill in an operational setting. The validation was carried out against hourly visibility data recorded at Indira Gandhi International Airport over Delhi during the winter months ( December and January) for the period 2009-2012. Error statistics show that the analogue fog model can capture a significant part of the observed variability of fog. The forecasts have more success in forecasting intense (visibility < 500 m) and persistent (duration > 4 h) fog events. The model provides a useful forecasting tool, as shown by measures such as average error, number of false warnings and the number of misses. [ABSTRACT FROM AUTHOR]

One major challenge in climate-related issues is the lack of accurate high-resolution precipitation data on the part of observations and climate model simulations, imposing profound constraints on various impact studies, for instance in the fields of hydrology, glaciology, agronomy and hazard assessment. Here, we present a physical model approach for orographic precipitation based on linear theory and combined with a stochastic weather generator which takes an intermediate position between computationally expensive high-resolution regional climate models and purely statistical downscaling techniques. The model is applied to a mountainous region in central Germany and run over a decade in a 0.005° resolution (≈500 m). The resulting precipitation fields are spatially and temporally compared with station data from a very dense meteorological network and with a 6 km regional reanalysis. The spatial correlation between local station data and corresponding model grid boxes is between 0.72 and 0.80. The presented linear model also agrees well with the observed spatial pattern of day-to-day variability, mean intensity, weak and extreme precipitation events. It is close to the performance of the high-resolution regional reanalysis COSMO-REA6, yet computationally far more efficient. Combined with the weather generator, the linear model matches the statistical properties of the station data almost perfectly and offers a consistent precipitation dataset at 0.005° resolution. The model can be applied to any larger-scale model or observational dataset, including climate change projections. [ABSTRACT FROM AUTHOR]

ABSTRACT The scientific debate on the impact of climate change on hurricane intensity/strength continues. Regardless of its causes, the consequence of increasing hurricane intensity is undeniably immense among coastal residents. In this study, we investigate how various objective measures of hurricane strength affect people's perception of changing hurricane strength over time. We utilize original survey data to examine the relationship between perceived and actual shift in hurricane strength. In this article, hurricane strength is indicated as maximum wind speed at landfall, storm surge, and economic damage. We find that the characteristics of hurricane strength associated with the most recent landfall are much more closely associated with perceptions of changing hurricane strength than objectively measured trends. This result is consistent with availability bias, suggesting that perceptions are associated with most accessible and retrievable events. We also find that people's belief in climate change play a powerful role in one's perception of changing hurricane strength. Political predispositions are found to affect one's perceptions of changing hurricane strength. Compared to Democrats and Independents, Republicans are far less likely to believe that climate is changing and thus they tend to not believe that hurricanes are becoming stronger. Given that this study focuses on how physical characteristics of past hurricane events influence individual perceptions of hurricane strength shift, future research should focus on how expectations of future climate and weather-related events influence individual attitudes and behaviours. [ABSTRACT FROM AUTHOR]

Changes in the character of rainfall are assessed using a holistic set of statistics based on rainfall frequency and amount distributions in climate change experiments with three conventional and superparameterized versions of the Community Atmosphere Model (CAM and SPCAM). Previous work has shown that high-order statistics of present-day rainfall intensity are significantly improved with superparameterization, especially in regions of tropical convection. Globally, the two modeling approaches project a similar future increase in mean rainfall, especially across the Inter-Tropical Convergence Zone (ITCZ) and at high latitudes, but over land, SPCAM predicts a smaller mean change than CAM. Changes in high-order statistics are similar at high latitudes in the two models but diverge at lower latitudes. In the tropics, SPCAM projects a large intensification of moderate and extreme rain rates in regions of organized convection associated with the Madden Julian Oscillation, ITCZ, monsoons, and tropical waves. In contrast, this signal is missing in all versions of CAM, which are found to be prone to predicting increases in the amount but not intensity of moderate rates. Predictions from SPCAM exhibit a scale-insensitive behavior with little dependence on horizontal resolution for extreme rates, while lower resolution (∼2°) versions of CAM are not able to capture the response simulated with higher resolution (∼1°). Moderate rain rates analyzed by the 'amount mode' and 'amount median' are found to be especially telling as a diagnostic for evaluating climate model performance and tracing future changes in rainfall statistics to tropical wave modes in SPCAM. [ABSTRACT FROM AUTHOR]

In this study, the stochastic deep convection parameterization of Plant and Craig (PC) is implemented in the Community Atmospheric Model version 5 (CAM5) to incorporate the stochastic processes of convection into the Zhang-McFarlane (ZM) deterministic deep convective scheme. Its impacts on deep convection, shallow convection, large-scale precipitation and associated dynamic and thermodynamic fields are investigated. Results show that with the introduction of the PC stochastic parameterization, deep convection is decreased while shallow convection is enhanced. The decrease in deep convection is mainly caused by the stochastic process and the spatial averaging of input quantities for the PC scheme. More detrained liquid water associated with more shallow convection leads to significant increase in liquid water and ice water paths, which increases large-scale precipitation in tropical regions. Specific humidity, relative humidity, zonal wind in the tropics, and precipitable water are all improved. The simulation of shortwave cloud forcing (SWCF) is also improved. The PC stochastic parameterization decreases the global mean SWCF from −52.25 W/m2 in the standard CAM5 to −48.86 W/m2, close to −47.16 W/m2 in observations. The improvement in SWCF over the tropics is due to decreased low cloud fraction simulated by the stochastic scheme. Sensitivity tests of tuning parameters are also performed to investigate the sensitivity of simulated climatology to uncertain parameters in the stochastic deep convection scheme. [ABSTRACT FROM AUTHOR]

ABSTRACT Quantifying precipitation variability and trends is difficult and merits regular reassessment. In the present study, the seasonal homogenized precipitation series in Switzerland is investigated for the period 1901-2013 in terms of trends, inter-annual variability and the influence of large-scale flow. An objective clustering is applied, resulting in 32 distinct precipitation regions. Trends are analysed for all 32 regions with moving trend windows, and statistical significance ( p < 0.05) is assessed with Theil-Sen trend estimates and nonparametric Mann-Kendall trend tests. Inter-annual precipitation varies considerably regionally and seasonally. Of 2720 analysed trend windows of 33-113 years in length, 194 (7.1%) show a significantly positive trend and 10 (0.4%) a significantly negative trend. Most of the significantly positive trends are found for 50+ year series for winter, autumn and the year. 81% of the annual and 72% of the winter series show positive trends (0-3% per decade) for the 1901-2013 period. The trends are significant for 34% (22%) of the annual (winter) series. Long-term trends are generally in line with earlier estimates in literature considering somewhat shorter time periods. Significantly negative trends are only found for winter in the most recent decades. No significant trends are found for inter-annual variability and changes in the 10th and 90th percentile seasonal extreme precipitation thresholds. The influence of large-scale flow on precipitation variability is strongest in winter. The leading pattern for northern Switzerland ( nS) is the Euro-Atlantic blocking pattern. For southern Switzerland ( sS), the Eastern Atlantic (Scandinavian) pattern is dominant in winter (autumn). In nS, wet (dry) seasons are linked to south-westerly (north-easterly) flow. In sS, wet (dry) seasons are linked to southerly (northerly) flow. Strong evidence for imprints of atmospheric blocking on seasonal precipitation variability is found in winter and autumn. In spring, a high pressure anomaly stretching from the mid-Atlantic to central Europe is indicative of dryness in nS. [ABSTRACT FROM AUTHOR]

This study evaluates several important statistics of daily rainfall based on frequency and amount distributions as simulated by a global climate model whose precipitation does not depend on convective parameterization-Super-Parameterized Community Atmosphere Model (SPCAM). Three superparameterized and conventional versions of CAM, coupled within the Community Earth System Model (CESM1 and CCSM4), are compared against two modern rainfall products (GPCP 1DD and TRMM 3B42) to discriminate robust effects of superparameterization that emerge across multiple versions. The geographic pattern of annual-mean rainfall is mostly insensitive to superparameterization, with only slight improvements in the double-ITCZ bias. However, unfolding intensity distributions reveal several improvements in the character of rainfall simulated by SPCAM. The rainfall rate that delivers the most accumulated rain (i.e., amount mode) is systematically too weak in all versions of CAM relative to TRMM 3B42 and does not improve with horizontal resolution. It is improved by superparameterization though, with higher modes in regions of tropical wave, Madden-Julian Oscillation, and monsoon activity. Superparameterization produces better representations of extreme rates compared to TRMM 3B42, without sensitivity to horizontal resolution seen in CAM. SPCAM produces more dry days over land and fewer over the ocean. Updates to CAM's low cloud parameterizations have narrowed the frequency peak of light rain, converging toward SPCAM. Poleward of 50°, where more rainfall is produced by resolved-scale processes in CAM, few differences discriminate the rainfall properties of the two models. These results are discussed in light of their implication for future rainfall changes in response to climate forcing. [ABSTRACT FROM AUTHOR]

ABSTRACT This article addresses the regional impacts of climate change on precipitation and meteorological drought over Southern South America ( SSA) through a CMIP5 multi-model ensemble based on 15 General Circulation Models ( GCMs) forced under two different greenhouse gas concentration pathways ( RCP4.5 and RCP8.5). An assessment of the biases in the representation of the precipitation annual cycle was performed over the 1979-2008 period over five regions within SSA, based on a comparison between the GCMs precipitation outputs with the Global Precipitation Climatology Centre ( GPCC) dataset. The multi-model ensemble well reproduces the shape of the annual cycle of precipitation over most of SSA, although the monthly totals were overestimated (underestimated) over the North-West and South (North-East and Central-East) regions. Changes in precipitation and meteorological drought characteristics were identified by the difference for early (2011-2040) and late (2071-2100) 21st century values with respect to the 1979-2008 baseline, using the standardized precipitation index as a short- and long-term drought indicator. Future climate conditions are expected to modify the regional characteristics of meteorological droughts over SSA, but the range of uncertainty in the expected changes is high. A significant increase in the number of drought events in all the regions for most of the 21st century sub-periods is projected for the multi-model ensemble. The mean duration of drought events will be shorter, with no significant changes in the severity of droughts and the occurrence of multi-decadal changes in the number of critical dry months is likely, although the significance in the changes depends on the region, future time horizon and greenhouse gas concentration pathways. These results overlap with a projected increase in precipitation over most of the regions, which has a strong seasonality and, therefore, will have some implications upon the future meteorological drought developments and the agricultural and hydrological practices in SSA. [ABSTRACT FROM AUTHOR]

We present a comprehensive analysis of temperature-related extreme events in Ny-Ålesund (78.9°N, 11.9°E) using data from three meteorological stations. The results show that annual mean temperatures in Ny-Ålesund increase at a rate that is four times faster than the global mean from 1975 to 2014 with no 'hiatus' in recent decades. The annual diurnal temperature range shows a negative trend as minimum daily temperature increases at a faster rate than maximum daily temperature. A negative trend in cold extremes and a positive trend in warm extremes are observed. This asymmetry hints at potential changes in the probability distribution of temperatures in Ny-Ålesund. [ABSTRACT FROM AUTHOR]

National security agencies and other interested parties now often regard conflict as the inevitable consequence of climate change. This inclination to reduce war to the vicissitudes of climate is not new however. Here, I examine some of the earlier ways in which violence was attributed to climatic conditions, particularly in the United States, and trace links between these older advocates of climatic determinism and the recent writings of those insisting that climate change will usher in a grim world of chronic warfare. It ends by drawing attention to the writings of some critics who are troubled by the ease with which climatic reductionism is capturing the public imagination. WIREs Clim Change 2015, 6:437-444. doi: 10.1002/wcc.352 For further resources related to this article, please visit the . [ABSTRACT FROM AUTHOR]

ABSTRACT An international programme dedicated to the study of the Third Pole Environment ( TPE) is now developing. The TPE region is centred on the Tibetan Plateau and concerns the interests of the surrounding countries and regions. To improve input for hydrological research, we collected precipitation data on 241 meteorological stations across the TPE region; these data were obtained from various countries, thus including various types of gauges. Employing the procedure recommended by the World Meteorological Organization ( WMO), a full version of bias adjustment was applied to the data, including adjustments for wind-induced error, wetting loss, evaporation loss and trace amount for each station. The results reveal that the average annual precipitation has increased considerably from a minimum of 4 mm to a maximum of 409 mm with an overall mean of 27% from the adjustment, the largest bias being found in the Chinese standard precipitation gauge ( CSPG) which was used in the central TPE region. In addition, the bias shows variable spatial and temporal patterns in different climate zones throughout this area. It is expected that this study and its results will be beneficial for hydrological and climatic studies over the TPE region. [ABSTRACT FROM AUTHOR]

The study of the multiannual thermal dynamics of Lake Iseo, a deep lake in the Italian pre-alpine area, is presented. Interflow was found to be the dominant river entrance mode, suggesting future susceptibility of the lake thermal structure to the overall effects of climate change expected in the upstream alpine watershed. A lake model employed the results of a long-term hydrologic model to simulate the effects of a climate change scenario on the lake's thermal evolution for the period 2012-2050. The model predicts an overall average increase in the lake water temperature of 0.012 °C/year and a reinforced Schmidt thermal stability of the water column in the winter up to 800 J/m2. Both these effects may further hinder the deep circulation process, which is vital for the oxygenation of deep water. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The surface and tropospheric temperature trends have been evaluated over Armenia. A very clear signal of warming is detected at most stations of Armenia for spring, summer and autumn seasons for the period 1979-2012 compared to 1961-1994. Overall, the observed data and the reanalyses products ( ERA-40 and ERA-Interim) provide a generally consistent picture for tropospheric temperature trends over Armenia. The trends obtained from the three sources of data show significantly faster warming at the near-surface troposphere (at 850 hPa) for the period 1979-2012 compared to 1961-1994. However, temperature trends at 850 hPa are underestimated by the reanalysis products relative to the observed data. The warming rates decrease with height, and negative and nearly zero trends are observed in the middle and upper troposphere in most cases. [ABSTRACT FROM AUTHOR]