Climatic aspects and vertical structure circulation associated with the severe drought in Northeast Brazil (2012–2016)

Climate Dynamics - This study provides an updated dynamical analysis of the observed climate conditions during the longest, most severe and continuous drought (2012–2016) ever recorded in...     

Trends and variability of storminess in the Northeast Atlantic region, 1874–2007

This article builds on the previous studies on storminess conditions in the northeast North Atlantic–European region. The period of surface pressure data analyzed is extended from 1881–1998 to 1874–2007. The seasonality and regional differences of storminess conditions in this region are also explored in more detail. The results show that storminess conditions in this region have undergone substantial decadal or longer time scale fluctuations, with considerable seasonal and regional differences. The most notable differences are seen between winter and summer, and between the North Sea area and other parts of the region. In particular, winter storminess shows an unprecedented maximum in the early 1990s in the North Sea area and a steady upward trend in the northeastern part of the region, while it appears to have declined in the western part of the region. In summer, storminess appears to have declined in most parts of this region. In the transition seasons, the storminess trend is characterized by increases in the northern part of the region and decreases in the southeastern part, with increases in the north being larger in spring. In particular, the results also show that the earliest storminess maximum occurred in summer (around 1880), while the latest storminess maximum occurred in winter (in the early 1990s). Looking at the annual metrics alone (as in previous studies), one would conclude that the latest storminess maximum is at about the same level as the earliest storminess maximum, without realizing that this is comparing the highest winter storminess level with the highest summer storminess level in the period of record analyzed, while winter and summer storminess conditions have undergone very different long-term variability and trends. Also, storminess conditions in the NE Atlantic region are found to be significantly correlated with the simultaneous NAO index in all seasons but autumn. The higher the NAO index, the rougher the NE Atlantic storminess conditions, especially in winter and spring.     

Persistent Features of Drought Strength in North China and Its Prediction

1. Introduction Drought disasters occur frequently in North China, with droughty extension being the widest, droughty intensity the most serious and lasting time the longest. In particular, the serious drought has threatened agriculture extremely in recent years, as such has influenced economy, ecosystem, and even daily life of people. The drought in North China is not only the vital research subject for meteorologists, but also one of the issues concerned for government. Therefore, finding …     

Regionalisation of global insights into dryland vulnerability: Better reflecting smallholders’ vulnerability in Northeast Brazil

Global analyses of vulnerability reveal generic insights into the relation between socio-ecological systems and the stress impacting upon them including climate and market variability. They thus provide a valuable basis for better understanding and comparing the evolution of socio-ecological systems from a broad perspective. However, even when reflecting sub-national differences, global assessments necessarily aggregate regional variations in the underlying conditions of vulnerability. Refinements are therefore necessary to better accommodate context-specific processes and hence facilitate vulnerability reduction. This study presents a novel methodology to refining global insights into vulnerability at a regional scale. It is based on a spatially explicit link between broad patterns of vulnerability and modelled regional smallholder development. Its application in order to better represent the drylands of Northeast Brazil reveals specific facets of smallholders’ vulnerability at the municipio level, reflecting non-linear dynamics. The results show that smallholders’ vulnerability was widely exacerbated in the most vulnerable areas. One key mechanism causing such a vulnerability increase involved intensifying resource degradation and the related potential for impoverishment as modelled at the regional scale. In addition, by subsequently re-orienting their livelihoods towards off-farm activities, smallholders became more sensitive to fluctuations and competition in the labour market. In contrast to these critical trends, living and environmental conditions improved in only some areas, thus indicating a decrease in vulnerability. Altogether, in differentiating the heterogeneity of resource management and smallholders’ livelihoods, the regional refinement presented in this study indicates necessary adjustments to generic strategies for vulnerability reduction gained at the global scale.     

Drought and water policy in Australia: Challenges for the future illustrated by the issues associated with water trading and climate change adaptation in the Murray–Darling Basin

This paper reviews historical and existing drought and water policy in Australia in order to gain a sense of the strengths and weaknesses in enabling effective adaptation to climate change. In particular, (a) the social, economic, and environmental costs and benefits of water trading and (b) the limitations of using ‘market-based’ instruments (MBIs), like water trading, for adapting to drought and water security related climate change impacts are investigated. It was found that water trading has potential as a climate change adaptation strategy with many benefits experienced in previous and current versions of water trading. However, there are also limitations and those negatively impacted by water trading are hit hard. These social impacts of water trading have not been thoroughly investigated and are not well understood. Significant uncertainty also exists around the impacts of water trading on the environment (e.g. changed hydrological regimes, underestimation of sustainable environmental flows etc.). Proper quantification of these impacts is needed, however, it is a complex task given Australia's large hydroclimatic variability and the current lack of understanding as to how to optimise water needs of the environment, humans, agriculture and other industries. It appears that ‘cap and trade’ quantity-based MBIs such as water trading will eventually do what they are designed to do (i.e. reallocate a resource to ‘high value’ users). However, given that the ‘low value’ users in this case are agriculture and town/urban water supply (not including drinking water) and the ‘high value’ users are mining, manufacturing, and electricity production (i.e. high greenhouse gas emissions), do we really want the water trading MBI to achieve its objective? And, what would the social and environmental ramifications of such a shift in water use within Australia be? These questions, along with the limitations and potential implications of using water trading (and MBIs in general) as a climate change adaptation tool, must be carefully considered if past Australian drought and water policy failures are not to be repeated.     

Rainfall characteristics for periglacial debris flows in the Swiss Alps: past incidences�Cpotential future evolutions

Based on observational meteorological data since A.D. 1864 and tree-ring records of debris-flow activity, this paper assesses changes in rainfall characteristics and their impact on the triggering of geomorphic events in a high-elevation watershed of the Swiss Alps since the end of the Little Ice Age. No trends are visible in the frequency of heavy rainfall events, but we observe a reduced number of heavy, short-lived rainfalls in summer and a concentration of advective storms is recorded in late summer and early fall since the late 1980s. These changes in triggering meteorological conditions resulted in a cluster of debris flows in the early decades of the twentieth century and a lowering of debris-flow activity since the mid 1990s, and may be mirroring the observed changes in persistent high-pressure systems over the Alps. We also observe intra-seasonal differences in debris-flow system response reflecting the state of the permafrost body in the source area of debris flows, allowing for very small debris flows to be released by limited rainfall inputs (<20 mm) in June and July. The same quantities of rain will not trigger debris flows in August or September, when a thick active layer of the permafrost body is capable of absorbing water. With the projected amplitude of climatic change, seasonality, return intervals and volumes of debris flows are likely to be altered. RCM projections based on the IPCC A2 scenario suggest a decrease in heavy summer rainfalls which will most likely result in a (further) reduction of the overall frequency of debris flows, leaving more time for sediment to accumulate in the channel. Such an increase of channel accumulation rates along with the projected destabilization of the steep rock-glacier body is likely, in turn, to exert control ultimately on sediment volumes released from the source areas during future events. Observations from adjacent catchments suggest that extremely large debris flows, beyond historical experience, could occur at the study site and in similar debris-flow systems of the Valais Alps originating from periglacial environments.     

The future of the past—an earth system framework for high resolution paleoclimatology: editorial essay

High-resolution paleoclimatology is the study of climate variability and change on interannual to multi-century time scales. Its primary focus is the past few millennia, a period lacking major shifts in external climate forcing and earth system configuration. Large arrays of proxy climate records derived from natural archives have been used to reconstruct aspects of climate in recent centuries. The main approaches used have been empirical and statistical, albeit informed by prior knowledge both of the physics of the climate, and of the processes imprinting climate information in the natural archives. We propose a new direction, in which emerging tools are used to formalize the combination of process knowledge and proxy climate records to better illuminate past climate variability on these time scales of great relevance to human concerns.     

The Relation between Atmospheric Intraseasonal Oscillation and Summer Severe Flood and Drought in the Changjiang-Huaihe River Basin

The intraseasonal oscillation (ISO) is studied during the severe flood and drought years of the Changjiang-Huaihe River Basin with the NCEP/NCAR reanalysis data and the precipitation data in China. The results show that the upper-level (200 hPa) ISO pattern for severe flood (drought) is charac-terized by an anticyclonic (cyclonic) circulation over the southern Tibetan Plateau and a cyclonic (anti-cyclonic) circulation over the northern Tibetan Plateau. The lower-level (850 hPa) ISO pattern is char-acterized by an anticyclonic (cyclonic) circulation over the area south of the Changjiang River, the South China Sea, and the Western Pacific, and a cyclonic (anticyclonic) circulation from the area north of the Changjiang River to Japan. These low-level ISO circulation patterns are the first modes of the ISO wind field according to the vector EOF expansion with stronger amplitude of the EOF1 time coefficient in se-vere flood years than in severe drought years. The analyses also reveal that at 500 hPa and 200 hPa,the atmospheric ISO activity over the Changjiang-Huaihe River basin, North China, and the middle-high latitudes north of China is stronger for severe flood than for severe drought. The ISO meridional wind over the middle-high latitude regions can propagate southwards and meet with the northward propagating ISO meridional wind from lower latitude regions over the Changjiang-Huaihe River Basin during severe flood years, but not during severe drought years.     

Land–sea contrast,soil-atmosphere and cloud-temperature interactions: interplays and roles in future summer European climate change

Europe and in particular its southern part are expected to undergo serious climate changes during summer in response to anthropogenic forcing, with large surface warming and decrease in precipitation. Yet, serious uncertainties remain, especially over central and western Europe. Several mechanisms have been suggested to be important in that context but their relative importance and possible interplays are still not well understood. In this paper, the role of soil-atmosphere interactions, cloud-temperature interactions and land–sea warming contrast in summer European climate change and how they interact are analyzed. Models for which evapotranspiration is strongly limited by soil moisture in the present climate are found to tend to simulate larger future decrease in evapotranspiration. Models characterized by stronger present-day anti-correlation between cloud cover and temperature over land tend to simulate larger future decrease in cloud cover. Large model-to-model differences regarding land–sea warming contrast and its impacts are also found. Warming over land is expected to be larger than warming over sea, leading to a decrease in continental relative humidity and precipitation because of the discrepancy between the change in atmospheric moisture capacity over land and the change in specific humidity. Yet, it is not true for all the models over our domain of interest. Models in which evapotranspiration is not limited by soil moisture and with a weak present-day anti-correlation between cloud cover and temperature tend to simulate smaller land surface warming. In these models, change in specific humidity over land is therefore able to match the continental increase in moisture capacity, which leads to virtually no change in continental relative humidity and smaller precipitation change. Because of the physical links that exist between the response to anthropogenic forcing of important impact-related climate variables and the way some mechanisms are simulated in the context of present-day variability, this study suggests some potentially useful metrics to reduce summer European climate change uncertainties.     

Snow days? Snowmaking adaptation and the future of low latitude, high elevation skiing in Arizona, USA

Inter-annual snow reliability is a key short-term concern for Arizona’s high elevation, low latitude ski resorts. Variability is linked to the El Niño Southern Oscillation (ENSO)–warm phase conditions typically portend a good ski season and vice versa. To operate more consistently in the medium-term Arizona’s two largest ski resorts plan to expand snowmaking. Snowmaking is a water and temperature constrained adaptation. One of the two resorts has overcome its water constraint by contracting with a municipality for treated wastewater. To assess the temperature constraint downscaled global coupled climate model temperature projections were compared to technical thresholds for the manufacture of snow at three time steps. In 2030, a period coincident with the lifetime of the investments, snowmaking will likely remain feasible. However, by 2050, temperatures will likely exceed technical thresholds in the shoulder seasons meaning that in years when natural snowfalls are poor the ski season may be curtailed. By 2080, without snowmaking efficiency improvements, warmer temperatures will make snowmaking increasingly more expensive and resort managers may need to plan for a future where operations and snowmaking are shifted to higher elevation, shaded, more snow reliable runs.     

Seizing policy windows: Policy Influence of climate advocacy coalitions in Brazil,China, and India, 2000–2015

What drives the development of climate policy? Brazil, China, and India have all changed their climate policies since 2000, and single-case analyses of climate policymaking have found that all three countries have had climate coalitions working to promote climate policies. To what extent have such advocacy coalitions been able to influence national policies for climate-change mitigation, and what can explain this? Employing a new approach that combines the advocacy coalition framework (ACF) with insights from comparative environmental politics and the literature on policy windows, this paper identifies why external parameters like political economy and institutional structures are crucial for explaining the climate advocacy coalitions’ ability to seize policy windows and influence policy development. We find that the coalitions adjust their policy strategies to the influence-opportunity structures in each political context—resulting in confrontation in Brazil, cooperation in China, and a complementary role in India.     

Studies on the Northern Early Summer Teleconnection Patterns, Their Interannual Variations and Relation to Drought / Flood in China

By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.     

Quantitative relationships between precipitation and temperature over Northeast China, 1961–2010

This paper investigates monthly and seasonal precipitation–temperature relationships (PTRs) over Northeast China using a method proposed in this study. The PTRs are influenced by clouds, latent and sensible heat conversion, precipitation type, etc. In summer, the influences of these factors on temperature decrease are different for various altitudes, latitudes, longitudes, and climate types. Stronger negative PTRs ranging from ?0.049 to ?0.075 °C/mm mostly occur in the semi-arid region, where the cold frontal-type precipitation dominates. In contrast, weaker negative PTRs ranging from ?0.004 to ?0.014 °C/mm mainly distribute in Liaoning Province, where rain is mainly orographic rain controlled by the warm and humid air of East Asian summer monsoon. In winter, surface temperature increases owing to the release of latent heat and sensible heat when precipitation occurs. The stronger positive PTRs ranging from 0.963 to 3.786 °C/mm mostly occur at high altitudes and latitudes due to more release of sensible heat. The enhanced atmospheric counter radiation by clouds is the major factor affecting increases of surface temperature in winter and decreases of surface temperature in summer when precipitation occurs.     

A Forecasting Model of Vector Similarity in Phase Space for Flood and Drought over the Huanghe-Huaihe-Haihe Plain in China

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Anthropogenic heat in the city of S?o Paulo, Brazil

The main goal of this work is to describe the anthropogenic energy flux (Q _F) in the city of S?o Paulo, Brazil. The hourly, monthly, and annual values of the anthropogenic energy flux are estimated using the inventory method, and the contributions of vehicular, stationary, and human metabolism sources from 2004 to 2007 are considered. The vehicular and stationary sources are evaluated using the primary consumption of energy based on fossil fuel, bio fuel, and electricity usage by the population. The diurnal evolution of the anthropogenic energy flux shows three relative maxima, with the largest maxima occurring early in the morning (??19.9 Wm^?2) and in the late afternoon (??20.3 Wm^?2). The relative maximum that occurs around noontime (??19.6 Wm^?2) reflects the diurnal pattern of vehicle traffic that seems to be specific to S?o Paulo. With respect to diurnal evolution, the energy flux released by vehicular sources (Q _FV) contributes approximately 50% of the total anthropogenic energy flux. Stationary sources (Q _FS) and human metabolism (Q _FM) represent about 41% and 9% of the anthropogenic energy flux, respectively. For 2007, the monthly values of Q _FV, Q _FS, Q _FM, and Q _F are, respectively, 16.8?±?0.25, 14.3?±?0.16, 3.5?±?0.03, and 34.6?±?0.41?MJ?m^?2?month^?1. The seasonal evolution monthly values of Q _FV, Q _FS, Q _FM, and Q _F show a relative minimum during the summer and winter vacations and a systematic and progressive increase associated with the seasonal evolution of the economic activity in S?o Paulo. The annual evolution of Q _F indicates that the city of S?o Paulo released 355.2?MJ?m^?2?year^?1 in 2004 and 415.5?MJ?m^?2?year^?1 in 2007 in association with an annual rate of increase of 19.6?MJ?m^?2?year^?1 (from 2004 to 2006) and 30.5?MJ?m^?2?year^?1 (from 2006 to 2007). The anthropogenic energy flux corresponds to about 9% of the net radiation at the surface in the summer and 15% in the winter. The amplitude of seasonal variation of the maximum hourly value of the diurnal variation increases exponentially with latitude.     

Changes in extreme daily rainfall for São Paulo, Brazil

Significant positive trends are found in the evolution of daily rainfall extremes in the city of São Paulo (Brazil) from 1933 to 2010. Climatic indices including ENSO, PDO, NAO and the sea surface temperature at the coast near São Paulo explain 85 % of the increasing frequency of extremes during the dry season. During the wet season the climatic indices and the local sea surface temperature explain a smaller fraction of the total variance when compared to the dry season indicating that other factors such as the growth of the urban heat island and the role of air pollution in cloud microphysics need to be taken into account to explain the observed trends over the almost eight decades.     

Characteristics of extreme daily minimum and maximum temperature over Northeast China, 1961–2009

In this study, the multifractal detrended fluctuation analysis method is employed to determine the thresholds of extreme events. Subsequently, the characteristics of extreme temperatures have been analyzed over Northeast China during 1961–2009. Approximately 58 % of stations have negative interdecadal trends of ?2.2 days/10 years to 0 days/10 years in extreme low minimum temperature (ELMT) frequency. Notable positive trend of 0–2.5 days/10 years in extreme high maximum temperature (EHMT) frequency of about 94 % stations are found. Approximately 58 % of stations have decreasing trend in ELMT intensity, whereas 69 % of stations have increasing trend of EHMT intensity. The trends are the range of ?0.72 °C/10 years to 0 °C/10 years and 0–0.7 °C/10 years, respectively. We propose the extreme temperatures indices, ELMT index (ELMTI) and EHMT index (EHMTI), which combined the frequency and intensity of extreme temperatures to represent the order of severity of extreme temperatures. According to this approach, serious ELMT mainly occur in the Songliao Plain and the Sanjiang Plain, especially in the Songliao Plain. Serious EHMT distinctly occur in the Sanjing Plain, and the southwestern and northwestern regions of Northeast China in recent five decades.