Variability of atmospheric circulation under the climate change in West Siberia in the late 20th–early 21st centuries

The estimates of spatiotemporal variability of climatic parameters in West Siberia are obtained over the period of 1976-2014. It is revealed that this variability is affected by the parameters of atmospheric circulation such as wind speed components, relative vorticity, and large-scale circulation indices. It is found that in winter the warming changed into the cooling that is particularly associated with the change in atmospheric circulation patterns described by the SCAND index.     

Potential impact of climate change on carbon in agricultural soils in Canada 2000–2099

Under the threat of global warming it is important to determine the impact that future changes in climate may have on the environment and to what extent any adverse effects can be mitigated. In this study we assessed the impact that climate change scenarios may have on soil carbon stocks in Canada and examined the potential for agricultural management practices to improve or maintain soil quality. Historical weather data from 1951 to 2001 indicated that semi-arid soils in western Canada have become warmer and dryer and air temperatures have increased during the spring and winter months. Results from the Canadian Center for Climate Modelling and Analysis (CCCma) Coupled Global Climate Model (CGCM1,2) under two climate change forcing scenarios also indicated that future temperatures would increase more in the spring and winter. Precipitation increased significantly under the IPCC IS92a scenario and agreed with historical trends in eastern Canada whereas the IPCC SRES B2 scenario indicated very little change in precipitation and better matched historical trends in western Canada. The Century model was used to examine the influence of climate change on agricultural soil carbon (C) stocks in Canada. Relative to simulations using historical weather data, model results under the SRES B2 climate scenario indicated that agricultural soils would lose 160 Tg of carbon by 2099 and under the IS92a scenario would lose 53 Tg C. Carbon was still lost from soils in humid climatic regions even though C inputs from crops increased by 10–13%. Carbon factors associated with changes in management practices were also estimated under both climate change scenarios. There was little difference in factors associated with conversion from conventional to no-till agriculture, while carbon factors associated with the conversion of annual crops to perennial grass were lower than for historical data in semi-arid soils because water stress hampered crop production but were higher in humid soils.     

Estimate of Hydrofluorocarbon Emissions for 2012–16 in the Yangtze River Delta,China

Hydrofluorocarbons(HFCs) have been widely used in China as substitutes for ozone-depleting substances,the production and use of which are being phased out under the Montreal Protocol.China is a major consumer of HFCs around the world,with its HFC emissions in CO_2-equivalent contributing to about 18% of the global emissions for the period2012-16.Three methods are widely used to estimate the emissions of HFCs-namely,the bottom-up method,top-down method and tracer ratio method.In this study,the tracer ratio method was adopted to estimate HFC emissions in the Yangtze River Delta(YRD),using CO as a tracer.The YRD region might make a significant contribution to Chinese totals owing to its rapid economic growth.Weekly flask measurements for ten HFCs(HFC-23,HFC-32,HFC-125,HFC-134 a,HFC-143 a,HFC-152 a,HFC-227 ea,HFC-236 fa,HFC-245 fa and HFC-365 mfc) were conducted at Lin'an Regional Background Station in the YRD over the period 2012-16,and the HFC emissions were 2.4±1.4 Gg yr~(-1) for HFC-23,2.8±1.2 Gg yr~(-1) for HFC-32,2.2±1.2 Gg yr~(-1) for HFC-125,4.8±4.8 Gg yr~(-1) for HFC-134 a,0.9±0.6 Gg yr~(-1) for HFC-152 a,0.3±0.3 Gg yr~(-1) for HFC-227 ea and 0.3±0.2 Gg yr~(-1) for HFC-245 fa.The YRD total HFC emissions reached 53 Gg CO_2-e yr~(-1),contributing 34% of the national total.The per capita HFC CO_2-equivalent emissions rate was 240 kg yr-1,while the values of per unit area emissions and per million GDP emissions reached 150 Mg km~(-2)yr~(-1) and 3500 kg yr~(-1)(million CNY GDP)-1,which were much higher than national or global levels.     

Recent (1980–2009) evidence of climate change in the upper Karakoram, Pakistan

We investigate here recent (1980–2009) climate variability in the upper Karakoram, Northern Pakistan, of particular interest given the peculiar glacier behavior during the last two decades. Differently from other glacierized regions in the Hindu Kush–Karakoram–Himalaya region, glaciers in the Karakoram display limited ice thinning, and in some cases advancing has been detected. Climate analysis is required to describe recent (i.e., last three decades) variability, to aid highlighting of the factors driving glacier evolution. Starting from monthly data, we analyze seasonal values of total precipitation, number of wet days, maximum (max) and minimum (min) air temperature, max precipitation in 24 h, and cloud cover for 17 weather stations in the upper Karakoram, clustered within three climatic regions as per use of principal components analysis. We detect possible nonstationarity in each of these regions by way of (1) linear regression, (2) moving window average, and (3) Mann–Kendall test, also in progressive form, to detect the onset date of possible trends. We then evaluate linear correlation coefficients between Northern Atlantic Oscillation (NAO) index and climate variables to assess effectiveness of teleconnections, claimed recently to affect climate in this area. Also, we compare temperature within the investigated zone against global temperature anomalies, to evidence enhanced warming within this area. We found mostly nonsignificant changes of total precipitation, unless for few stations displaying increase in Chitral-Hindu Kush region and Northwest Karakoram, or Gilgit area, and decrease in Western Himalaya, Kotli region. Max precipitation is mostly unchanged, unless for slight increase in Chitral and Gilgit areas, and slight decrease in Kotli region. Number of wet days is mostly increasing in Gilgit area, and decreasing in Chitral area, with no clear signal in Kotli region. Min temperatures increase always but during Summer, when decreasing values are detected, especially for Gilgit and Chitral regions. Max temperatures are found to increase everywhere. Cloud cover is significantly increasing in Gilgit area, but decreasing otherwise, especially in Kotli region. Max temperature regime is significantly positively correlated against global thermal anomaly, while min temperature regime is nonsignificantly negatively correlated. Max and min temperatures seem mostly negatively correlated to NAO. Some dependence of trend intensity for the considered variables against altitude is found, different for each region, suggesting that investigation of weather variables at the highest altitudes is warranted to discriminate further climate variability in the area.     

Possible impacts of climate change on extreme weather events at local scale in south–central Canada

Synoptic weather typing and regression-based downscaling approaches have become popular in evaluating the impacts of climate change on a variety of environmental problems, particularly those involving extreme impacts. One of the reasons for the popularity of these approaches is their ability to categorize a complex set of meteorological variables into a coherent index, facilitating the projection of changes in frequency and intensity of future daily extreme weather events and/or their impacts. This paper illustrated the capability of the synoptic weather typing and regression methods to analyze climatic change impacts on a number of extreme weather events and environmental problems for south–central Canada, such as freezing rain, heavy rainfall, high-/low-streamflow events, air pollution, and human health. These statistical approaches are helpful in analyzing extreme events and projecting their impacts into the future through three major steps or analysis procedures: (1) historical simulation modeling to identify extreme weather events or their impacts, (2) statistical downscaling to provide station-scale future hourly/daily climate data, and (3) projecting changes in the frequency and intensity of future extreme weather events and their impacts under a changing climate. To realize these steps, it is first necessary to conceptualize the modeling of the meteorology, hydrology and impacts model variables of significance and to apply a number of linear/nonlinear regression techniques. Because the climate/weather validation process is critical, a formal model result verification process has been built into each of these three steps. With carefully chosen physically consistent and relevant variables, the results of the verification, based on historical observations of the outcome variables simulated by the models, show a very good agreement in all applications and extremes tested to date. Overall, the modeled results from climate change studies indicate that the frequency and intensity of future extreme weather events and their impacts are generally projected to significantly increase late this century over south–central Canada under a changing climate. The implications of these increases need be taken into consideration and integrated into policies and planning for adaptation strategies, including measures to incorporate climate change into engineering infrastructure design standards and disaster risk reduction measures. This paper briefly summarized these climate change research projects, focusing on the modeling methodologies and results, and attempted to use plain language to make the results more accessible and interesting to the broader informed audience. These research projects have been used to support decision-makers in south–central Canada when dealing with future extreme weather events under climate change.     

The evolution of temperature extremes in the Gaspé Peninsula,Quebec, Canada (1974–2013)

The majority of natural hazards that affect Canadian territory are the result of extreme climate and weather conditions. Among these weather hazards, some can be calculated from the application of thresholds for minimum and maximum temperatures at a daily or monthly timescale. These thermal indices allowed the prediction of extreme conditions that may have an impact on the human population by affecting, for example, health, agriculture, and water resources. In this article, we discuss the methods used (RHtestsV4, SPLIDHOM, ClimPACT) then describe the steps followed to calculate the indices, including how we dealt with the problem of missing data and the necessity to identify a common methodology to analyze the time series. We also present possible solutions for ensuring the quality of meteorological data. We then present an overview of the results, namely the main trends and variability of extreme temperature for seven stations located in the Gaspé Peninsula from 1974 to 2013. Our results indicate some break points in time series and positive trends for most indices related to the rise of the temperatures but indicate a negative trend for the indices related to low temperatures for most stations during the study period.     

Six centuries of May–July precipitation in Cyprus from tree rings

A May–July precipitation nested reconstruction for the period AD 1415–2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Calibration and verification statistics for the period 1917–2010 show a good level of skill, and split-sample validation over 1917–2010 supports temporal stability of the tree-ring signal for precipitation. Smoothed annual time series of reconstructed precipitation and a tally of drought events in a moving time window indicate that the calibration period is not representative of the full range of drought variability. While convective precipitation in the warm season may be driven strongly by local factors, composite maps of geopotential height anomaly for dry years and wet years support large-scale atmospheric-flow influence related to height anomalies over the broader region of northeast Africa and the eastern Mediterranean. Emerging positive trend in reconstruction residuals may be an early sign of exacerbation of drought stress on trees by recent warming in May–July. Future warming expected from increases in greenhouse gases poses a threat to forest resources in Cyprus and elsewhere in the Mediterranean.     

Changes in the Proportion of Precipitation Occurring as Rain in Northern Canada during Spring–Summer from 1979–2015

Changes in the form of precipitation have a considerable impact on the Arctic cryosphere and ecological system by influencing the energy balance and surface runoff. In this study, station observations and ERA-Interim data were used to analyze changes in the rainfall to precipitation ratio(RPR) in northern Canada during the spring–summer season(March–July)from 1979–2015. Our results indicate that ERA-Interim describes the spring–summer variations and trends in temperature and the RPR well. Both the spring–summer mean temperature [0.4℃–1℃(10 yr)~(-1)] and the RPR [2%–6%(10 yr)~(-1)] increased significantly in the Canadian Arctic Archipelago from 1979–2015. Moreover, we suggest that, aside from the contribution of climate warming, the North Atlantic Oscillation is probably another key factor influencing temporal and spatial differences in the RPR over northern Canada.     

Characteristics, loss and gain of atmospheric carbonyl compounds in winters of 2008–2010 in Pearl River Delta region, China

Formaldehyde (HCHO), acetaldehyde (CH₃CHO) and acetone (CH₃COCH₃) were measured at Wanqingsha (WQS) in south China during November-December 2008–2010. Carbonyl compound pollution characteristics under the influence of the financial crisis (FC) were studied. Atmospheric carbonyl compound concentrations in the 2008 and 2009 sampling periods were affected by the 2008 FC. The industrial downturn plus the high closing down number of the small enterprises with limited emission treatment during the FC played an important role in the reduction of the industry-related CH₃CHO and CH₃COCH₃. In 2010, the recovery of industrial activities occurred, but affected by traffic restriction enforcement in Guangzhou over the Asian Games period, HCHO concentration (daytime 7.59?±?2.59 μg m^?3) was lower than expectation. Carbonyl compounds in WQS site were highly influenced by regional pollution transport from different upwind urban cities and industrial districts in the north-northwest to northeast wind sector in winter. Also, the interaction of the winter monsoon with the warm ocean along the coastline as well as day and night boundary layer mixing height variation affected carbonyl compound concentrations in WQS. The daytime mean dry deposition losses of HCHO and CH₃CHO were first time model-estimated for 2009 and 2010. For loss of HCHO in the early afternoon, photolysis was the dominant sink, followed by dry deposition and removal by OH radical (?OH), while for CH₃CHO, dry deposition was dominant. For the gain of HCHO and CH₃CHO, the production rates during early afternoon in 2009 and 2010 were estimated by an indirect approach.     

Analysis of a regional change in the sign of the SAM�Ctemperature relationship in Antarctica

This study examines regional atmospheric circulation changes associated with a reversal in the sign of the relationship between the Southern Annular Mode (SAM) and near-surface temperatures at Halley station, East Antarctica, during the 1980s. We show that the key factor affecting the regional SAM?Ctemperature relationship (STR) is the relative magnitude of two climatological low pressure centres to the west and east of the area, which determines the source region of air masses advected into the locality. The principal difference affecting the STR is shown to be a trend towards a significantly weaker climatological low (higher pressure) at ~20°E during a positive phase of the SAM. Specifically, it is variations in the phase and magnitude of the wave number three patterns of atmospheric circulation, the non-annular component of the SAM, which are the principal factors governing the regional STR. A similar reversal is observed in the sign of the correlation between the SAM and oxygen-isotope values from an ice core located some 1,200?km east of Halley. This relationship is examined throughout the 20th Century, by comparing the isotope data to SAM reconstructions, and demonstrates marked decadal variability. Thus, these data suggest that switches in the STR are more likely to reflect natural variability in the long-wave patterns over the Southern Ocean rather than the influence of an anthropogenic forcing. This finding is important when considering the potential utility of Antarctic isotope data as a proxy for the SAM.     

Interdecadal change in the Antarctic Circumpolar Wave during 1951–2010

In this study,we defined an index of the Antarctic Circumploar Wave(ACW) and analyzed its variability for the period 1951-2010.A regime shift of the circumpolar westerly in the Southern Ocean and an interdecadal change of the ACW,which occurred around the mid-1970s,were identified.Associated with these changes,the variations of the ACW show three distinct sub-periods:1951-1973,1974-1980,and 1981-2010.They are characterized by different speeds,amplitudes,and wave structures.We briefly investigated possible mechanisms responsible for the different behaviors of the ACW during the three periods.     

Climate change and crop yields in the Indian Cardamom Hills, 1978–2007 CE

In this study we analyzed climate and crop yields data from Indian cardamom hills for the period 1978–2007 to investigate whether there were significant changes in weather elements, and if such changes have had significant impact on the production of spices and plantation crops. Spatial and temporal variations in air temperatures (maximum and minimum), rainfall and relative humidity are evident across stations. The mean air temperature increased significantly during the last 30?years; the greatest increase and the largest significant upward trend was observed in the daily temperature. The highest increase in minimum temperature was registered for June (0.37°C/18?years) at the Myladumpara station. December and January showed greater warming across the stations. Rainfall during the main monsoon months (June–September) showed a downward trend. Relative humidity showed increasing and decreasing trends, respectively, at the cardamom and tea growing tracts. The warming trend coupled with frequent wet and dry spells during the summer is likely to have a favorable effect on insect pests and disease causing organisms thereby pesticide consumption can go up both during excess rainfall and drought years. The incidence of many minor pest insects and disease pathogens has increased in the recent years of our study along with warming. Significant and slight increases in the yield of small cardamom (Elettaria cardamomum M.) and coffee (Coffea arabica), respectively, were noticed in the recent years.; however the improvement of yield in tea (Thea sinensis) and black pepper (Piper nigrum L.) has not been seen in our analysis.     

Summertime warming in the European part of Russia and extreme heat in 2010 as manifestation of large-scale atmospheric circulation trends in the late 20th–early 21st centuries

Considered is a relationship between long-term variations of the surface air temperature and of the field of geopotential at the level of 500 hPa in the middle of summer in the European part of Russia and the variations of large-scale atmospheric circulation described by the indices of North Atlantic and North Pacific centers of atmospheric action. The considerable inhomogeneity in the course of average temperature in the European part of Russia in July divides it into two periods, before and after the 1980s. Unlike stationary fluctuations of temperature before the 1980s, the 6–10-year fluctuations are typical of the period of 1981–2010 against a background of its considerable rise by 0.8°C per 10 years with the contribution of 20% to the total variance. During this period, about 80% of temperature variability are caused by the circulation variations, and 55% of them are associated with the North Pacific centers of atmospheric action, in particular, with the WP index in July, May, and April. Revealed regression dependences between circulation indices and the air temperature in the European part of Russia explain rather accurately the linear trend, the fluctuations with the period of 6–10 years, and the extremes in 1988, 2001–2003, and 2010. The analysis of the time series (1950–2012) of WP, PDO, and SOI indices demonstrates that changes in the atmospheric circulation took place in the extratropical zone of the Northern Hemisphere at the turn of the 1980s and this caused the formation of blocking situations and, hence, steady heat and drought in summer in the mid-latitude zone including the European part of Russia. These variations can be interpreted as a change in the regimes of strong (1950–1980) and weak (1981–2012) circulation. The heat in July 2010 was an extreme display of weak circulation, and this is indicated by the unprecedented low values of the WP index in July and May.     

Analysis and farmers’ perception of climate change in the Kashmir Valley,India

Theoretical and Applied Climatology - Analysis of climatic variables is important for the detection and attribution of climate change trends and has received considerable attention from researchers...     

Climatology of thunderstorms in the Baltic countries, 1951–2000

This paper provides an overview of the thunderstorm climate of the Baltic countries during the period of 1951–2000. Our study area is in northeastern Europe and encompasses Estonia, Latvia, and Lithuania. Visual thunderstorm observations at 59 weather stations were used as a data source. The mean annual number of thunderstorm days was 12–29.5. The seasonal cycle of thunderstorm hours with a daily step unexpectedly showed two maxima, whereas the monthly numbers of thunderstorm days had one clear mid-latitude specific peak between June and August. The diurnal cycle of thunderstorm hours showed a peak between 1400 and 1800 local time and a minimum between 0400 and 1000 hours local time. The average annual duration of thunderstorm events was 112 min. The average number of thunderstorm events per thunderstorm day was around 1.1–1.2. Our results showed that the thunderstorm climate of the Baltic countries generally resembles that of other mid-latitude study sites.     

Variability of droughts in the Czech Republic, 1881–2006

We analyze droughts in the Czech Republic from 1881–2006 based on the Palmer drought severity index (PDSI) and the Z-index using averaged national temperature and precipitation series for the calculations. The standardized precipitation index (SPI), PDSI and Z-index series show an increasing tendency towards longer and more intensive dry episodes in which, for example, droughts that occurred in the mid-1930s, late 1940s–early 1950s, late 1980s–early 1990s and early 2000s were the most severe. Cycles at periods of 3.4–3.5, 4.2–4.3, 5.0–5.1 and 15.4 years exceeded 95% confidence levels in application of maximum entropy spectral analysis. These are expressed at different intensities throughout the period studied. The occurrence of extremely dry and severely dry months is associated with a higher frequency of anticyclonic situations according to the classification employed by the Czech Hydrometeorological Institute. Principal component analysis documents the importance of the ridge from the Siberian High over Central Europe when extreme and severe droughts in months of the winter half-year are considered in terms of sea-level pressure. In the summer half-year, the ridge of the Azores High over Central Europe is the most important. Drought episodes have a profound effect on national and regional agricultural production, with yields being consistently lower than in normal years, as is documented through the example of spring barley, winter wheat, forage crops on arable land, and hay from meadows. Seasons with pronounced drought during the April–June period (e.g., 1947 and 2000) show the most significant yield decreases. Forests appear to be very vulnerable to long-term drought episodes, as it was the case during the dry years of 1992–1994. This study clearly confirms the statistically significant tendency to more intensive dry episodes in the region, driven by temperature increase and precipitation decrease, which has already been suggested in other studies.     

Land cover change and soil organic carbon stocks in the Republic of Ireland 1851–2000

Using both historic records and CORINE land cover maps, we assessed the impact of land cover change on the stock of soil organic carbon (SOC) in the Republic of Ireland from 1851 to 2000. We identified ten principal land cover classes: arable land, forest, grassland, heterogeneous agricultural areas/other, nonvegetated semi-natural areas, peatland, suburban, urban, water bodies, and wetland. For each land cover class, the SOC stock was estimated as the product of SOC density and land cover area. These were summed to calculate a national SOC budget for the Republic of Ireland. The Republic of Ireland’s 6.94 million hectares of land have undergone considerable change over the past 150 years. The most striking feature is the decrease in arable land from 1.44 million ha in 1851 to 0.55 million ha in 2000. Over the same time period, forested land increased by 0.53 million ha. As of 2000, agricultural lands including arable land (7.85%), grassland (54.33%), and the heterogeneous agricultural areas/other class (7.91%) account for 70.09% of Irish land cover. We estimate that the SOC stock in the Republic of Ireland, to 1 m depth, has increased from 1,391 Tg in 1851 to 1,469 Tg in 2000 despite soil loss due to urbanization. This increase is largely due to the increase of forested land with its higher SOC stocks when compared to agricultural lands. Peatlands contain a disproportionate quantity of the SOC stock. Although peatlands only occupy 17.36% of the land area, as of 2000, they represented 36% of the SOC stock (to 1 m depth).