Summertime Drought Research Articles

Farmers' perceptions of permanent grasslands and their intentions to adapt to climate change influence their resilience strategy

Abstract Climate change will increase average temperatures and the frequency and intensity of summertime droughts; those shifts will in turn affect forage production in grassland-based livestock farms. Farmers will accordingly likely have to implement adaptation strategies to cope with the effects of climate change. We hypothesized that farmers' resilience strategies would depend on (i) their intention to adapt to climate change, which partly results from previous climate risk exposure, (ii) how they perceive the values and disvalues of multi-species permanent grasslands (PGs), and (iii) that both of the aforementioned factors would vary according to the geographical context of each farm. We carried out 15 semi-structured interviews with dairy cattle farmers in the French Massif Central; the farms were distributed along a range of climatic and topographic conditions. We used (i) the Model of Proactive Private Adaptation to Climate Change to analyze farmers' individual process of adaptation, (ii) the Integrated Nature Futures Framework to analyze farmers' perception of multi-species PGs, and (iii) text analysis to identify the farmers' adaptation strategies. Nine of the farmers felt that they were already adapted to climate change or that they had a plan in place to implement new adaptations in the future. We observed straightforward relationships between these farmers' perception of PGs and their choice of adaptation strategy; those relationships varied, however, with the geographical context of each farm. Farmers in the northern Massif Central and southern uplands highlighted the values of PGs and considered PGs to be central to their adaption strategies. Conversely, farmers in the southern lowlands mostly referred to the disvalues of PGs; they based their adaptation strategies on temporary grasslands and forage crops. Three of the farmers believed that climate change posed a significant risk, but they foresaw little room to maneuver. Despite acknowledging the values of PGs, those individuals did not intend to use PGs to adapt to climate change. The final three farmers did not intend to adapt to climate change; their reasoning stemmed from either a mindset of fatalism or their acknowledged desire to retire soon. Extreme events such as the summertime drought of 2003 and human factors such as intergenerational transmission of farm can accordingly facilitate or inhibit climate change-related adaptation. It is accordingly important to take into account both socio-psychological and environmental factors when analyzing how grassland-based farmers transition to more climate change-resilient systems.

Effect of stockpiling time on donor-peat hydrophysical properties: Implications for peatland restoration

Northern peatlands are an important global climate regulator storing approximately one-third of the global carbon pool, however the degradation of these ecosystems from land-use change can switch peatlands to persistent and long-term sources of atmospheric carbon dioxide. Active restoration is often required to return degraded peatlands to a net carbon sink. The peat-block restoration technique, where intact peat blocks are extracted from a donor peatland and transferred to restore peatlands where the remnant peat is non-existent, contaminated, and/or undergoes seasonal flooding is increasingly being adopted as a peatland restoration technique given the carbon sequestration that can occur immediately post-restoration. However, donor peat blocks often need to be temporarily stockpiled during the restoration process due to logistical constraints. The dewatering of the peat blocks during this stockpiling period may alter hydrophysical peat properties that sustain critical peatland ecohydrological functionality and ultimately affect peatland restoration success. Yet, the hydrophysical evolution of stockpiled peat blocks remains unknown. Here, we examine how peat block stockpiling time (3, 7, 11, and 14 months and a reference site) impacts peat hydrophysical properties and sphagnum moss photosynthesis, both of which are critical for peatland restoration success. Stockpiling peat differentially impacted the hydrophysical properties between the shallower and deeper peats, where little to no impact from stockpiling was observed in the shallower peats, regardless of stockpiling time. Rather, as stockpiling time increased, there was a marked decrease in macroporosity (pores >75 μm) and mobile porosity (drainable porosity at approximately −100 hpa) at depths below 20 cm but the water conducting matrix porosity (defined as mobile porosity minus macroporosity) was not significantly different than the reference samples. However, stockpiling created inhospitable conditions for sphagnum mosses., as chlorophyll fluorescence ratio was below 0.3, indicating little to no photosynthesis of the stockpiled peat during summertime drought conditions. Taken together, we suggest limiting stockpiling time as much as possible would be advantageous for using the stockpiled peat blocks for the peat-block restoration technique or other restoration efforts, such as floating mat creation.

Extreme drought in the recent two decades in northern China resulting from Eurasian warming

The analysis of 55-year daily precipitation data reveals prolonging in consecutive dry-day (CDD) and extreme summertime droughts in northern China since the 1990s. Anomalous CDD corresponds to a persistent anticyclone anomaly, that has a significant correlation with enhancing in Eurasian forced waves including Eurasian teleconnection (EU) pattern and Silk Road pattern (SRP), which have response to the upward wave activity flux over the key region (40°N–70°N, 0°E–60°E) and other regions along the EU and SRP over Eurasia. Those are the partly significant forcing sources converting energy for the forced wave. It is hypothesized that increasing Eurasian heating is more notable with global warming, and it leads to increasing atmospheric baroclinicity in the lower troposphere, further for increasing wave activity flux, that is responsible for the enhancing EU and SRP, and finally contributes to enhancing anticyclone anomaly over northern China. These anomalous circulations may result in prolonging CDD and persistent summertime drought under anthropogenic warming as projected by global climate models.

Projections of Future Precipitation Extremes Over Europe: A Multimodel Assessment of Climate Simulations

AbstractProjections of precipitation and its extremes over the European continent are analyzed in an extensive multimodel ensemble of 12 and 50 km resolution EURO‐CORDEX Regional Climate Models (RCMs) forced by RCP2.6, RCP4.5, and RCP8.5 (Representative Concentration Pathway) aerosol and greenhouse gas emission scenarios. A systematic intercomparison with ENSEMBLES RCMs is carried out, such that in total information is provided for an unprecedentedly large data set of 100 RCM simulations. An evaluation finds very reasonable skill for the EURO‐CORDEX models in simulating temporal and geographical variations of (mean and heavy) precipitation at both horizontal resolutions. Heavy and extreme precipitation events are projected to intensify across most of Europe throughout the whole year. All considered models agree on a distinct intensification of extremes by often more than +20% in winter and fall and over central and northern Europe. A reduction of rainy days and mean precipitation in summer is simulated by a large majority of models in the Mediterranean area, but intermodel spread between the simulations is large. In central Europe and France during summer, models project decreases in precipitation but more intense heavy and extreme rainfalls. Comparison to previous RCM projections from ENSEMBLES reveals consistency but slight differences in summer, where reductions in southern European precipitation are not as pronounced as previously projected. The projected changes of the European hydrological cycle may have substantial impact on environmental and anthropogenic systems. In particular, the simulations indicate a rising probability of summertime drought in southern Europe and more frequent and intense heavy rainfall across all of Europe.

Seasonal Changes in Solar Radiation and Relative Humidity in Europe in Response to Global Warming*

Abstract Future seasonal changes in surface incident solar radiation and relative humidity (RH) over Europe and adjacent ocean areas were assessed based on phase 3 of the Coupled Model Intercomparison Project (CMIP3) model ensemble. Under the A1B scenario, by 2070–99, summertime solar radiation is projected to increase by 5%–10% in central and southern Europe. In winter, radiation decreases in most of northern and eastern Europe by 5%–15%. RH drops in summer in the southern European inland by 8%–12%, whereas in winter a small increase of 2%–3% is projected for northeastern Europe. In spring, the change is an intermediate between those in the extreme seasons, while in autumn the patterns resemble summer. Over the northern Atlantic Ocean, RH increases in all seasons by 1%–2%. The intermodel agreement on the sign of all these shifts is good, and the patterns recur in the responses to the A2 and B1 scenarios. Substantial changes are already simulated to occur before the midcentury, for example, in summer RH decreases by more than 5% in the inner Balkan Peninsula. Projected changes in these two variables agree well and are also mainly consistent with precipitation responses both in the multimodel mean and in individual models. According to all indicators, southern European summers become more arid, while winters, in the north particularly, become moister and darker. The increasing radiation and declining RH exacerbate summertime drought in southern Europe, whereas excessive humidity in the north may, for example, inflict moisture damages in constructions.

Drought and spring cooling induced recent decrease in vegetation growth in Inner Asia

The response of vegetation growth to current climate change in Inner Asia (35–55°N, 45–120°E) was investigated by analyzing time series of the Normalized Difference Vegetation Index (NDVI) data from the Advanced Very High Resolution Radiometer (AVHRR) from 1982 to 2009. We found that at the regional scale, the greening trend observed during the 1980s was stalled in the 1990s. Different seasons, however, show different changes and mechanisms. Among the three seasons (spring, summer and autumn), summer has the earliest turning point (from greening to non-greening) in the early 1990s, as a result of summertime droughts, as indicated by Palmer Drought Severity Index (PDSI). Consistent with the change in summer NDVI, summer PDSI and precipitation significantly increased in the 1980s, but strongly decreased since the early 1990s at the regional scale. The negative effect of summer drought is particularly significant over dry regions such as eastern Kazakhstan, Mongolia and Inner Mongolia. However, in high altitude or high latitude regions (>50°N), summer vegetation growth is more strongly correlated with summer temperature rather than with summer PDSI. In spring, changes in vegetation growth are closely linked with temperature changes rather than droughts. Both spring temperature and spring NDVI, for instance, increased until the late 1990s and then decreased. Statistical analyses also show that spring NDVI is significantly correlated with spring temperature at the regional scale (P<0.05), implying that temperature is the dominant limiting factor for spring vegetation growth in most regions of Inner Asia except Turkmenistan and Uzbekistan, where spring PDSI shows significant positive correlation with spring NDVI. Further analyses of the response of vegetation to extreme high spring temperature in 1997 and extreme summer drought in 2001 exhibit a highly heterogeneous pattern.

Reconstructed drought variability in southeastern Sweden since the 1650s

ABSTRACTIn this study, we present the first regional reconstruction of summer drought for southeastern Sweden. The June–July standardized precipitation index (SPI) was reconstructed over the period 1650–2002 based on Pinus sylvestris L. tree‐ring width data, where the reconstruction could account for 41.6% of the total variance in the instrumental record over 1901–2002. Our reconstruction suggests an overall wet 18th century and a dry 19th century. The most outstanding pluvial phase in the pre‐instrumental period took place in the mid‐1720s and lasted over 50 years, while multi‐decadal periods of below average moisture conditions were reconstructed in the 1660s–1720s, 1800s‐early 30s, and in the 1840s–50s. Several of these dry spells have previously been found in reconstructions from Sweden and Finland, indicating that our reconstruction reflects large‐scale moisture anomalies across eastern Fennoscandia. Comparison of the SPI estimates with mid‐tropospheric pressure patterns suggests that summertime drought is associated with positive pressure anomalies over British Isles and the North Sea, while an eastward movement of the Icelandic low‐pressure systems over the western part of central Fennoscandia results in wetter than normal June–July conditions over the region of interest.

Could anthropogenic soil erosion have influenced Mediterranean vegetation distribution over the Holocene?

The circum-Mediterranean region is characterized by a strongly seasonal climate with rainy winters and intense summertime drought, steep topography, and a multi-millennial history of intensive human land use, all of which make its soils vulnerable to erosion. The historical and stratigraphic record documents severe and long-term soil erosion in several locations in the Mediterranean. A forest-to-scrub transition in Mediterranean vegetation between the mid-Holocene (6,000 yr BP) and the present is evident in the observational palaeorecord. Debate as to the causes of this shift is ongoing. This study seeks to test the sensitivity of large-scale vegetation patterns to changes in soil physical properties such as depth, content of coarse fragments, and organic matter content using the Mediterranean region as a case study. We find that simulated biomes are sensitive to changes in some soil physical properties at some locations, but that threshold values for soil change to affect vegetation are very high. Additional work is required to analyze the role that other soil physical properties, and climate change, played in influencing Holocene land cover change in the Mediterranean, and to improve model representations of relevant processes.

CMA opposes gender discrimination against doctors

Global climate change is inevitable--the combustion of fossil fuels has resulted in a buildup of greenhouse gases within the atmosphere, causing unprecedented changes to the earth's climate. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change suggests that North America will experience marked changes in weather patterns in coming decades, including warmer temperatures and increased rainfall, summertime droughts and extreme weather events (e.g., tornadoes and hurricanes). Although these events may have direct consequences for health (e.g., injuries and displacement of populations due to thermal stress), they are also likely to cause important changes in the incidence and distribution of infectious diseases, including vector-borne and zoonotic diseases, water-and food-borne diseases and diseases with environmental reservoirs (e.g., endemic fungal diseases). Changes in weather patterns and ecosystems, and health consequences of climate change will probably be most severe in far northern regions (e.g., the Arctic). We provide an overview of the expected nature and direction of such changes, which pose current and future challenges to health care providers and public health agencies.

Europe's 2003 heat wave: a satellite view of impacts and land–atmosphere feedbacks

AbstractA combination of satellite imagery, meteorological station data, and the NCEP/NCAR reanalysis has been used to explore the spatial and temporal evolution of the 2003 heat wave in France, with focus on understanding the impacts and feedbacks at the land surface. Vegetation was severely affected across the study area, especially in a swath across central France that corresponds to the Western European Broadleaf (WEB) Forests ecological zone. The remotely sensed surface temperature anomaly was also greatest in this zone, peaking at +15.4 °C in August. On a finer spatial scale, both the vegetation and surface temperature anomalies were greater for crops and pastures than for forested lands. The heat wave was also associated with an anomalous surface forcing of air temperature. Relative to other years in record, satellite‐derived estimates of surface‐sensible heat flux indicate an enhancement of 48–61% (24.0–30.5 W m−2) in WEB during the August heat wave maximum. Longwave radiative heating of the planetary boundary layer (PBL) was enhanced by 10.5 W m−2 in WEB for the same period. The magnitude and spatial structure of this local heating is consistent with models of the late twenty‐first century climate in France, which predict a transitional climate zone that will become increasingly affected by summertime drought. Models of future climate also suggest that a soil‐moisture feedback on the surface energy balance might exacerbate summertime drought, and these proposed feedback mechanisms were tested using satellite‐derived heat budgets. Copyright © 2006 Royal Meteorological Society.

Hydrological and Dynamical Characteristics of Summertime Droughts over U.S. Great Plains

Abstract A drought pattern and its time evolution over the U.S. Great Plains are investigated from time series of climate divisional monthly mean surface air temperature and total precipitation anomalies. The spatial pattern consists of correlated occurrences of high (low) surface air temperature and deficit (excess) rainfall. The center of maximum amplitude in rain fluctuation is around Kansas City; that of temperature is over South Dakota. Internal consistency between temperature and precipitation variability is the salient feature of the drought pattern. A drought index is used to quantify drought severity for the period 1895–1996. The 12 severest drought months (in order) during this period are June 1933, June 1988, July 1936, August 1983, July 1934, July 1901, June 1931, August 1947, July 1930, June 1936, July 1954, and August 1936. Hydrological conditions are examined using National Centers for Environmental Prediction (NCEP) reanalysis precipitable water (PW) and monthly surface observations from K...

Dominant Factors Responsible for Interannual Variability of the Summer Monsoon in the Southwestern United States

Interannual variability of the summer monsoon in the southwestern United States is controlled by various ocean- and land-based conditions (e.g., SST, soil moisture, and snow cover) that provide sources of memory of antecedent climate anomalies such as ENSO. It is hypothesized that this interannual variability is also modulated by decade-scale fluctuations in the North Pacific SSTs. The following observations have been made in support of this hypothesis. First, the summer precipitation regime is dominated by a continental-scale precipitation pattern characterized by an out-of-phase relationship between precipitation in the southwestern United States and that in the Great Plains of the United States. Second, interannual fluctuations in the onset date of the monsoon in the southwestern United States are significantly correlated with interannual fluctuations in the intensity of summer rainfall in this region such that early monsoons are often very wet and late monsoons tend to be dry. Third, wet (dry) monsoons in the southwestern United States often follow winters characterized by dry (wet) conditions in the southwestern United States and wet (dry) conditions in the northwestern United States. Finally, interannual variability of the summer monsoon in the southwestern United States is modulated by long-term (decade scale) fluctuations in the North Pacific SSTs. The mechanism relating the North Pacific SST pattern to interannual variability in the summer monsoon appears to be via the impact of variations in the Pacific jet on West Coast precipitation regimes during the preceding winter. Multiyear fluctuations in the North Pacific SST pattern are consistent with multiyear fluctuations in the atmospheric circulation and in the West Coast precipitation regimes during Northern Hemisphere (NH) winter, hence with multiyear variability in the summer monsoon state. Influences on the summer monsoon during the preceding winter and spring are tied together using appropriate SST indices that capture decade-scale variability in the North Pacific during NH winter and interannual variability in the eastern tropical Pacific during NH spring. The results suggest that decadal variability in the North Pacific SSTs may be an important factor in determining long-term periods of summertime drought or rainy conditions both in the southwestern United States and in the Great Plains of the United States.

Spring Phenology: Nature's Experiment to Detect the Effect of “Green-Up” on Surface Maximum Temperatures

Abstract In spring many plants break dormancy and begin foliage production. The appearance of leaves (the “green-up” period) triggers a rapid increase in transpiration at the surface as well as changes in albedo. Subsequently, these processes alter the thermodynamic properties of the surface layer. Normally, seasonal variations in tropospheric thickness, and year-to-year variability in the green-up date, mask the impact of these effects on surface maximum temperatures. In this study we used first leaf phenological data (from the clone lilac Syringa chinensis in the central and eastern United States) as the indicator of transpiration onset, in order to reveal the effects of this change from a dormant vegetative surface, perhaps comparable to the worst summertime droughts, to an active foliage-producing and transpiring vegetative surface. Simple plots using average hypsometric layer-mean temperature (derived from geopotential thickness) and average surface daily maximum temperature were examined for variati...

Meteorological Conditions during Heat Waves and Droughts in the United States Great Plains

Abstract Summertime droughts and/or heat waves in the Kansas City area and their associated large-scale circulation patterns and land-surface moisture conditions are investigates, using climatological monthly mean surface data, rawinsonde data. Palmer drought severity indices, gridded monthly mean sea-level pressure data, and gridded 500 mb height data. Surface station data include monthly mean surface pressure, maximum/minimum temperature, temperature range, monthly total precipitation, dewpoint and relative humidity. Anomalies in monthly mean surface air temperature at Kansas City are used as a basis for objectively ranking the 276 months in the 92 summers, 1889–1980. The concentration of drought months in the decades of the 1910s, 1930s, and 1950s is evident. Many of the hot months during these periods exhibited negative anomalies in relative humidity, dewpoint, precipitation and Palmer index. Not all the hot summer months in the record at Kansas City appear to have been associated with drought (as def...

Woodland Breeding Bird Communities in Eastern Kansas

The deciduous woodlands of eastern Kansas are the westerly extensions of the North American deciduous forest. Environmental conditions clearly support a great number of tree species (e.g.? MacGregor? 1977), but the occurrence of periodic summertime drought is significant in limiting the distributions of a number of the dominant tree species to regions to the east, where more mesic conditions prevail. There are other ecological consequences of periodic dry spellssizes of trees are smaller (and canopy layering effects reduced) in Kansas relative to regions to the east. For these reasons the bird communities of the Kansas woodlands are less diverse and maintain lesser densities than in deciduous forests elsewhere (R. Johnston, ms.). Likewise, yearly variation in species composition of these bird communities occurs regularly, and it is the intent of this paper to assess the significance of that variation. Data on occurrence and abundance of the birds were obtained by censuses of the singing males and have been reported elsewhere (Zimmermann and Tatschl, 1975; Cink, 1975; Cink, 1976; Johnston, 1979). Such censuses are replicated several times in the course of being taken, and the reliability of the data on distribution and abundance is high.

SOME METEOROLOGICAL ASPECTS OF DROUGHT

The problem of drought is examined as a manifestation of anomalous patterns of the atmosphere's general circulation. Special consideration is given to the quasi-stationary planetary wave ensembles which are responsible for extensive summertime drought over the United States. The critical importance of the great Atlantic and Pacific anticyclones for encouraging or discouraging the development of the great North American upper level anticyclone, the immediate drought producing cell, is emphasized.