Autumn Drought Research Articles

Higher potential fire intensity at the dry range margins of European mountain trees

AbstractAimPotential fire intensity (PFI) is among the main drivers of fire–vegetation interactions, but how it varies across species ranges is unknown. We test whether PFI and crown fire likelihood (CFL) increase preferentially towards the warm/dry range margins of mountain trees.LocationThe western Alps.MethodsWe analysed PFI and CFL patterns across the environmental niches of major mountain forest tree species, using field observation data of surface fuels with fire simulations. Empirical relationships between PFI and climate and vegetation structure were identified in communities sampled for surface fuels, and then used to predict PFI in national forest inventory plots.ResultsSimulations indicate that autumn drought, spring precipitation, tree cover and tree basal area drove the variation in understorey fuels among communities, leading to different PFI among and within the environmental ranges of mountain tree species. PFI was consistently higher in the open‐canopy, dry margins of dominant tree species. The highest PFI values were found in the sub‐Mediterranean and subalpine forests in conjunction with higher CFL.Main conclusionsMountain trees are exposed to higher PFI and CFL at their dry range margins, suggesting higher potential fire impacts at their rear distribution edges. Moist montane species (Fagus sylvatica, Abies alba, Picea abies) are exposed to surface fires of lower intensities than sub‐Mediterranean (Quercus pubescens, Pinus nigra, P. sylvestris) and subalpine species (Larix decidua, P. uncinata, P. cembra) which may both experience higher likelihood of crown fires at their dry and flammable margins.

Spatial and Temporal Trend Analysis of Precipitation and Drought in South Korea

High spatial and temporal variation in precipitation in South Korea leads to an increase in the frequency and duration of drought. In this study, the spatial characteristics of temporal trends for precipitation and drought severity time series were analyzed at 55 stations across South Korea for the period 1980–2015. This study also reviewed the usefulness of different trend tests while addressing the issue of serial correlation, which has often received less attention in previous studies. Results showed that most significant trends in precipitation were detected along the south coast of South Korea, especially during winter, late spring and summer, whereas no significant trend was detected in annual precipitation. The Sen’s slope of the trends increased from January to August and decreased from August onward. Principal component analysis applied on Standardized Precipitation Index (SPI) at a 12-month time scale divides the whole of South Korea into four subregions with different temporal behaviors of drought severity. Moreover, drought severity showed a significant increasing trend, mainly on the northeast coast. Drought frequency analysis showed more frequent droughts in late winter, early spring and early autumn, with less frequent droughts in summer.

The Response of Vegetation Phenology and Productivity to Drought in Semi-Arid Regions of Northern China

A major disturbance in nature, drought, has a significant impact on the vulnerability and resilience of semi-arid ecosystems by shifting phenology and productivity. However, due to the various disturbance mechanisms, phenology and primary productivity have remained largely ambiguous until now. This paper evaluated the spatio-temporal changes of phenology and productivity based on GIMMS NDVI3g time series data, and demonstrated the responses of vegetation phenology and productivity to drought disturbances with the standardized precipitation evapotranspiration index (SPEI) in semi-arid ecosystems of northern China. The results showed that (1): vegetation phenology exhibited dramatic spatial heterogeneity with different rates, mostly presented in the regions with high chances of land cover type variation. The delayed onset of growing season (SOS) and advanced end of growing season (EOS) occurred in Horqin Sandy Land and the eastern Ordos Plateau with a one to three days/decade (p < 0.05) rate and in the middle and east of Inner Mongolia with a two days/decade rate, respectively. Vegetation productivity presented a clear pattern: south increased and north decreased. (2) Spring drought delayed SOS in grassland, barren/sparsely vegetated land, and cropland, while autumn drought significantly advanced EOS in grassland and barren/sparsely vegetated lands. Annual drought reduced vegetation productivity and the sensitivity of productivity regarding drought disturbance was higher than that of phenology.

Brief communication: Drought likelihood for East Africa

Abstract. The East Africa drought in autumn of year 2016 caused malnutrition, illness and death. Close to 16 million people across Somalia, Ethiopia and Kenya needed food, water and medical assistance. Many factors influence drought stress and response. However, inevitably the following question is asked: are elevated greenhouse gas concentrations altering extreme rainfall deficit frequency? We investigate this with general circulation models (GCMs). After GCM bias correction to match the climatological mean of the CHIRPS data-based rainfall product, climate models project small decreases in probability of drought with the same (or worse) severity as 2016 ASO (August to October) East African event. This is by the end of the 21st century compared to the probabilities for present day. However, when further adjusting the climatological variability of GCMs to also match CHIRPS data, by additionally bias-correcting for variance, then the probability of drought occurrence will increase slightly over the same period.

The weakening of autumn drought intensity in Korea after late 1990s

Using data of autumn (September–November) Palmer Drought Severity Index (PDSI) observed at 61 weather observation stations for 1974–2013 provided by Korea Meteorological Administration (KMA), the present study applies the statistical change-point analysis to the PDSI time-series in order to determine variability of autumn drought in Korea. The study result shows a trend that autumn drought in Korea has been weakened since 1998. This weakening trend is statistically significant at the 90% confidence level. Thus, a difference in autumn mean between 1998–2013 (PDSI: –1.6, which means ‘wetness’ condition) and 1974–1997 periods (PDSI: –0.6, which means ‘drought’ condition) is analyzed in order to determine the cause of the weakening of autumn drought in Korea in recent years. The analysis on 850 hPa stream flows shows that the Mascarene high (MH) is strengthened in the southeast sea of Madagascar and anomalous northeasterlies blown from this anomalous anticyclonic circulation are moved to the north along the eastern coast of Africa as the cross-equatorial flows and then move from India to the east towards the South China Sea (SCS) by the anomalous cyclone (Arabian low, AL) located in the south sea of the Arabian Peninsula. Then, the anomalous flows move to the north direction towards Korea and Japan by the anomalous anticyclone (western North Pacific subtropical high, WNPSH) located in the east of Japan and anomalous cyclone located in the East Asia continent thereby showing clear anomalous southerlies in those regions. The anomalous pressure system pattern of west low and east high type is a typical pressure system pattern revealed during summer in East Asia. That is, the anomalous southerlies played an important role in supplying warm and humid airs in the low latitude to mid-latitude regions in East Asia including Korea and Japan. In addition, the predictability for autumn drought in Korea is diagnosed using three anomalous pressure systems (MH, AL, WNPSH).

Agricultural autumn drought and crop yield in 2011 in Poland

Agricultural autumn drought and crop yield in 2011 in Poland

Effects of the human activities on the water level process of the Poyang Lake

The hydrological cycles in basin is profoundly affected by human activities. Yangtze River is a world class river with complex river-lake relations in the middle reaches. As the Three Gorges Reservoir (TGR) and other controlled reservoirs in the main stream and tributaries have been put into operation, the water regimes of the main stream in the middle reaches and Poyang Lake have been changed by water impounding and sediments trapping, clean water discharged from reservoirs, accelerating the evolution of the relationship of river and lake. After entering the 21st century, autumn droughts become more serious in Poyang Lake basin; the relationship between river and lake becomes tense. In light of the hydrological data in Poyang Lake since 2000s, this article made quantitative analyses of the influences of the human activities on the variation of the Poyang Lake level by authors. The results indicate that the main stream of Yangtze River, particularly the regulation of Three Gorges Reservoir, exerts a profound influence on the variation process of the Poyang Lake level. The regulation influence of the Upper Reach of the Yangtze River’s Reservoir Group (URYRRG) could spread to Tangyin area in the middle of the lake in October.

Spatial and temporal distribution of rainfall and drought characteristics across the Pearl River basin

Understanding rainfall trends as well as drought characteristics plays a key role in watershed development and management. In this study, the spatial and temporal characteristics of rainfall and drought based on temperature and precipitation data observed in 48 meteorological stations from 1959 to 2012 across the Pearl River Basin in China were analyzed. The possible influence of El Nino-Southern Oscillation (ENSO) and El Nino Modoki (ENSO_M) events on seasonal drought based on the Standardized Precipitation-evapotranspiration Index (SPEI) were also investigated. The results show that annual and seasonal rainfall decreased slightly in most areas, annual and seasonal daily precipitation concentration decreased in a few areas, monthly rainfall had an irregular distribution but with no significant trend detected, and rainfall seasonality increased in most areas. Drought tended to worsen during recent years, especially in the upper reaches, and seasonal drought also tended to become serious or occurred frequently across the Pearl River Basin. The drought patterns are not only related to the decreasing trends in rainfall but also to changes in the daily rainfall concentration, monthly rainfall heterogeneity, and rainfall seasonality. Both ENSO and ENSO_M events had an influence on summer drought in the middle-upper reaches. The ENSO events dominated the patterns of autumn drought in the Pearl River Delta, and the ENSO_M events strongly affected the changing patterns of autumn drought in the middle-upper reaches and northern parts of the middle-lower reaches.

Discrete seasonal hydroclimate reconstructions over northern Vietnam for the past three and a half centuries

We present a 350-year hydroclimatic year (HY) index for northern Vietnam derived from three discrete seasonal reconstructions from tree rings: an index of autumn rainfall from the earlywood widths of Chinese Douglas fir (Pseudotsuga sinensis), the first such record from this species, and two nearby published Palmer Drought Severity Index (PDSI) reconstructions from cypress (Fokienia hodginsii) tree rings for spring and summer, respectively. Autumn rainfall over the study region constitutes only around 9% of the annual total, but its variability is strongly linked to the strength of the atmospheric gradient over Asia during the transition from the boreal summer to winter monsoons. Deficit or surplus of autumn rainfall enhances or mitigates, respectively, the impact of the annual winter dry season on trees growing on porous karst hillsides. The most protracted HY drought (dry across all seasons) occurred at the turn of the twentieth century at a time of relative quiet, but a mid-to-late eighteenth century multi-year HY drought coincided with a period of great societal turmoil across mainland Southeast Asia and the Tay Son Rebellion in northern Vietnam. A mid-nineteenth century uprising accompanied by a smallpox epidemic, crop failure and famine, occurred during the worst autumn drought of the past two and a half centuries but only moderate drought in spring and summer. The “Great Vietnamese Famine” of the mid-twentieth century was dry only in autumn, with a wet spring and an average summer.

Increased Chances of Drought in Southeastern Periphery of the Tibetan Plateau Induced by Anthropogenic Warming

The southeastern periphery of the Tibetan Plateau (SEPTP) was hit by an extraordinarily severe drought in the autumn of 2009. Overall, the SEPTP has been gripped by a sustained drought for six consecutive years. To better understand the physical causes of these types of severe and frequent droughts and thus to improve their prediction and enhance the ability to adapt, many research efforts have been devoted to the disastrous droughts in the SEPTP. Nonetheless, whether the likelihood and strength of the severe droughts in the SEPTP, such as that in the autumn of 2009, have been affected by anthropogenic climate change remains unknown. This study first identifies the atmospheric circulation regime responsible for the SEPTP droughts and then explores how human-induced climate change has affected the severe droughts in the SEPTP. It is found that the drought conditions in the SEPTP have been driven by the Indian–Pacific warm pool (IPWP) sea surface temperature (SST) through strengthening of the local Hadley circulation and anomalously cyclonic motion over the South China Sea. Ensemble simulations of climate models demonstrate a robust increase in the dry and warm meteorological conditions seen during the 2009 SEPTP autumn drought due to anthropogenic global warming. Given that warming is expected to continue into the future, these results suggest that it is likely that drought conditions will become more common in the SEPTP.

Exposure of population to droughts in the Haihe River Basin under global warming of 1.5 and 2.0 °C scenarios

Based on outputs from regional climate model COSMO-CLM (CCLM), climate conditions in the Haihe River Basin (HRB) under the 1.5 and 2.0 °C global warming scenarios were projected. Drought characteristics were analyzed by the Standardized Precipitation Evapotranspiration Index (SPEI), and population exposure to regional droughts in the warming world were then assessed by a combination of the population in 2010. It was revealed that both annual precipitation and potential evapotranspiration will increase in the 1.5 °C warming level relative to the reference period of 1986–2005 in the HRB. But annual precipitation was projected to decrease in the 2.0 °C warming level, although potential evapotranspiration was projected to increase. The temperature in the HRB was projected to rise faster than the global mean, and the timing of the regional 2.0 °C warming level will come earlier. Under the global warming of 1.5 °C, intensity and coverage of droughts in the HRB exhibit no significant trends relative to 1986–2005, while the drought frequency might decrease to a certain degree. Under the global warming of 2.0 °C, intensity and coverage of droughts will increase notably. In particular, drought coverage in the 2.0 °C level will be 1.9 times larger than that of the 1.5 °C scenario. Drought frequency under the 2.0 °C warming scenario will increase relative to the 1.5 °C warming scenario but still be less than that of the reference period. As a result, population exposure to droughts in the 1.5 °C warming level could be reduced by 30.4% relative to the 1986–2005 period, but increase by 74.8% in the 2.0 °C warming level. Seasonally, an increasing trend of exposure to severe droughts in summer, autumn and winter was projected in the 1.5 °C global warming level, while that to extreme droughts in summer and winter will decrease. Under 2.0 °C global warming scenario, increasing trend of severe and extreme droughts was projected in spring, autumn and winter. And the exposure to extreme droughts in autumn and winter might be doubled relative to the reference period. Similar spatial distribution patterns were found for population exposure in 1.5 °C and 2 °C global warming levels with high values projected in south and central basin but low in north and west. But the difference is, less population will be exposed to droughts in most area of HRB under 1.5 °C warming scenario, while population exposure will be larger under 2.0 °C global warming scenario relative to 1986–2005. The additional 0.5 °C from 1.5 °C to 2.0 °C will obviously increase the drought risks, especially in the southern and central HRB. Considering the projections that more drought risks might exist under the 2.0 °C warming scenario than in the 1.5 °C level, a perspective to keep the increase in global mean temperature below 2.0 °C and limit it to 1.5 °C, has far-reaching implications to socioeconomic development in the HRB.

Correlation between hydrological drought, climatic factors, reservoir operation, and vegetation cover in the Xijiang Basin, South China

The Xijiang River is known as the Golden Watercourse because of its role in the development of the Pearl River Delta Regional Economic System in China, which was made possible by its abundant water resources. At present, the hydrological regime of the Xijiang River has now become complicated, the water shortages and successive droughts pose a threat to regional economic development. However, the complexity of hydroclimatological processes with emphasizes on drought has not been comprehended. In order to effectively predict and develop the adaptation strategies to cope with the water scarcity damage caused by hydrological droughts, it is essential to thoroughly analyze the relationship between hydrological droughts and pre/post-dependent hydroclimatological factors. To accomplish this, the extreme-point symmetric mode decomposition method (ESMD) was utilized to reveal the periodic variation in hydrological droughts that is characterized by the Standardized Drought Index (SDI). In addition, the cross-wavelet transform method was applied to investigate the correlation between large-scale climate indices and drought. The results showed that hydrological drought had the most significant response to spring ENSO (El Niño-Southern Oscillation), and the response lags in sub-basins were mostly 8–9months except that in Yujiang River were mainly 5 or 8months. Signal reservoir operation in the Yujiang River reduced drought severity by 52–95.8% from January to April over the 2003–2014 time period. Similarly, the cascade reservoir alleviated winter and spring droughts in the Hongshuihe River Basin. However, autumn drought was aggravated with severity increased by 41.9% in September and by 160.9% in October, so that the land surface models without considering human intervention must be used with caution in the hydrological simulation. The response lags of the VCI (Vegetation Condition Index) to hydrological drought were different in the sub-basins. The response lag for the Hongshuihe, Yujiang, and Liujiang River Basins were mostly 0–4months, 0–1months, and 2–3months, respectively, but there was no obvious regular change pattern in the Guijiang River Basin.

Extended autumn drought, but not nitrogen deposition, affects the diversity and productivity of a Mediterranean grassland

Global change is affecting ecosystems worldwide. Nitrogen (N) deposition is increasing globally and climate change scenarios forecast an increase of prolonged autumn droughts particularly in the Mediterranean regions. Mediterranean grasslands occupy 1.3 million km2 of the terrestrial surface, host high biodiversity values and generate important ecosystem services. Understanding the effects of N deposition and prolonged autumn drought on the productivity and dynamics of Mediterranean grasslands is crucial to support the conservation of these ecosystems in a global change context.We assessed the effects of extended autumn drought and N deposition on the productivity, species diversity, and phenology of a Mediterranean grassland through a manipulative, greenhouse, experiment. We simulated three levels of extended drought: no drought, 50days and 100days of drought and two levels of N deposition: no N and N addition, through a factorial design experiment.Severe drought (100days) affected negatively grassland productivity, through a reduction of the growing season duration and accumulated growing degree days. Moderate drought (50days) affected productivity negatively but productivity values recovered to levels similar to those of the non-drought treatment. Severe and moderate drought delayed plant phenology decreasing significantly the number of individuals with mature flowers and with fruits or seeds. Plant functional groups responded differently to drought with productivity of forbs, but not productivity of graminoids and legumes, being negatively affected by moderate and severe drought. N addition did not affect grassland productivity, diversity or phenology.Our results anticipate effects of climate change on the productivity and species composition of Mediterranean grasslands.

Hydrological impacts of precipitation extremes in the Huaihe River Basin, China

Precipitation extremes play a key role in flooding risks over the Huaihe River Basin, which is important to understand their hydrological impacts. Based on observed daily precipitation and streamflow data from 1958 to 2009, eight precipitation indices and three streamflow indices were calculated for the study of hydrological impacts of precipitation extremes. The results indicate that the wet condition intensified in the summer wet season and the drought condition was getting worse in the autumn dry season in the later years of the past 50 years. The river basin had experienced higher heavy rainfall-related flooding risks in summer and more severe drought in autumn in the later of the period. The extreme precipitation events or consecutive heavy rain day events led to the substantial increases in streamflow extremes, which are the main causes of frequent floods in the Huaihe River Basin. The large inter-annual variation of precipitation anomalies in the upper and central Huaihe River Basin are the major contributor for the regional frequent floods and droughts.

Integrated assessment for hydrometeorological drought based on Markov chain model

Drought assessment based on a single index cannot comprehensively reflect the characteristics of a drought affected by multiple factors. Therefore, the main purpose of this study is to accurately assess the drought by constructing an integrated drought assessment method (PDSI-SDI) that can combine the meteorological drought and hydrological drought at the same time. To better evaluate and forecast the drought, the Markov chain model is employed in this study to calculate the expected residence time, return period and transition probabilities of the drought. Furthermore, the Mann–Kendall method is adopted to predict the trend of the drought. The Weihe River Basin is selected as the study area, and according to the distribution characteristics of the water system, it is divided into five districts in order to better assess the drought. Results indicate that: (1) spatially, drought probabilities increase from south to north and west to east. (2) Temporally, probabilities of spring droughts are the highest, followed by summer droughts and autumn droughts, winter droughts have the lowest probabilities, extreme droughts are more likely to occur in autumn. (3) Drought preferentially transfers within the same scenario, except scenario 4 (meteorological drought with no hydrological drought) in autumn is prone to shift to scenario 1 (no meteorological drought with no hydrological drought). (4) There is a significant drying trend of the drought in the Weihe River Basin at the significance level of 95 %. The integrated drought assessment method and other methods adopted in this study can be applied in other regions as well.

Analysis of Changes in Spatial Pattern of Drought Using RDI Index in south of Iran

Drought is one of the main natural hazards affecting the economy and the environment of large areas. Droughts cause crop losses, urban water supply shortages, social alarm, degradation and desertification. In this study, the spatial characteristics of annual and seasonal drought were evaluated based on climate data from 16 synoptic stations during the period of 1980–2010 in south of Iran. To estimate the drought severity used modified Reconnaissance Drought Index (RDI) and to prepare maps, ArcGis10.2 software was used. Results showed in annual drought, percent of areas with normal condition, severe dry and extreme dry condition have had significant increasing trend (0.95 level). In winter drought, the percentage of areas with severe dry and extreme dry condition have had significant increasing trend (0.95 level). In spring drought, percent of areas with moderate dry has had significant increasing trend (0.95 level), in summer drought, percent of areas with moderate dry has had increasing trend (insignificant) and in autumn drought, percent of areas with severe dry has had significant increasing trend (0.95 level). Other classes of drought in different time scales had not significant trend. Result showed that the percentage of area with dry condition is increasing, this can be effective on the agricultural activities, agricultural productions, water resource management and other activities.

Adapting maize production to drought in the Northeast Farming Region of China

Abstract Maize (Zea mays L.) is the most prominent crop in the Northeast Farming Region of China (NFR), and drought has been the largest limitation for maize production in this area during recent decades. The question of how to adapt maize production to drought has received great attention from policy makers, researchers and farmers. In order to evaluate the effects of adaptation strategies against drought and examine the influences of policy supports and farmer households’ characteristics on adopting decisions, a large scale household survey was conducted in five representative maize production counties across NFR. Our survey results indicated that using variety diversification, drought resistant varieties and dibbling irrigation are the three major adaptation strategies against drought in spring, and farmers also adopted changes in sowing time, conservation tillage and mulching to cope with drought in spring. About 20% and 18% of households enhanced irrigation against drought in summer and autumn, respectively. Deep loosening tillage and organic fertilizer are also options for farmers to resist drought in summer. Maize yield was highly dependent on soil qualities, with yields on land of high soil quality approximately 1050 kg/ha and 2400 kg/ha higher than for normal and poor soil conditions, respectively. Using variety diversification and drought resistant varieties can respectively increase maize yield by approximately 150 and 220 kg/ha under drought. Conservation tillage increased maize yield by 438–459 kg/ha in drought years. Irrigation improved maize yield by 419–435 kg/ha and 444–463 kg/ha against drought in summer and autumn, respectively. Offering information service, financial and technical support can greatly increase the use of adaptation strategies for farmers to cope with drought. However, only 46% of households received information service, 43% of households received financial support, and 26% of households received technical support against drought from the local government. The maize acreage and the irrigation access are the major factors that influenced farmers’ decisions to apply adaptation strategies to cope with drought in each season, but only 25% of households have access to irrigation. This indicates the need for enhanced public support for farmers to better cope with drought in maize production, particularly through improving access to irrigation.

Probabilistic forecasting of seasonal droughts in the Pearl River basin, China

Forecasting of droughts is essential for developing measures for mitigation of drought hazards and for reducing drought-induced loss. In this study, droughts were characterized by the standardized precipitation-evapotranspiration index with a time scale of 3 months. Copula-based probabilistic forecasting models were developed to predict drought occurrences. Results indicated higher probability of occurrence of seasonal droughts after the occurrence of more severe seasonal droughts, and extreme drought in winter tended to persist with higher probability till spring, whereas extreme drought in autumn might not probably last to winter. Furthermore, results indicated high probability of occurrence of droughts in southeast parts of the Pearl River basin during spring to winter. Thus, droughts in the Pearl River basin are subject to lengthening duration, particularly in the southeastern part of the basin. It should be noted here that the southeastern part is densely populated with a high degree of socioeconomic development. Thus, higher probability of droughts in the southeastern part should attract considerable concern. Higher drought risk was also identified in the western part of the basin. Results of this study provide a theoretical framework for water resources management and conservation of eco-environment in the Pearl River basin in a changing climate, and may serve as a reference for evaluation of drought risk in other regions of the world.

Field Evaluation of Cocksfoot, Tall Fescue and Phalaris for Dry Marginal Environments of South‐Eastern Australia. 2. Persistence

AbstractPerennial grasses provide forage and environmental benefits in the agricultural systems of southern Australia, but persistent cultivars are lacking for the lower rainfall inland margins (<600 mm average annual rainfall). Potential new cultivars of cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb. = syn. Lolium arundinaceum (Schreb.) Darbysh.) and phalaris (Phalaris aquatica L.) have been developed in response to this need. These and older cultivars were evaluated for persistence at five sites in south‐eastern Australia from 2009 to 2013. A wide range in rainfall was experienced, but survival was principally reduced by a severe spring–summer–autumn drought in the final year in which all species began to decline in persistence once the spring 2012 to autumn 2013 cumulative climatic moisture deficit became higher than about 700 mm and declined very severely at deficits over 1000 mm. The highly summer‐dormant cocksfoot ssp. hispanica control cultivar Kasbah showed outstanding survival of this event in the cropping zone of southern New South Wales, but not at the drier of two sites with acidic soils in central Victorian where all cocksfoot cultivars showed similar survival. Potential new summer‐active tall fescue cultivars survived well at the higher rainfall Victorian site and under high rainfall in northern NSW. All tall fescue cultivars experienced high mortality during a period of high moisture stress in the spring of the establishment year in southern NSW, but the Mediterranean cultivar Grasslands Flecha MaxP gradually recovered. Differences among phalaris cultivars were not large with new cultivars of North African origin being marginally more persistent at the drier site in southern NSW. Comparisons with results from the Mediterranean Basin are discussed. Although there was no clear evidence of differences in persistence between the new and old cultivars, some of the new cultivars were considered to show potential for commercial release.

Teleconnected influence of tropical Northwest Pacific sea surface temperature on interannual variability of autumn precipitation in Southwest China

The interannual variation of autumn precipitation in Southwest China (SWC) and the possible influence of tropical Northwest Pacific (NWP) sea surface temperature (SST) are investigated. Statistical analysis shows that SWC precipitation is negatively correlated with concurrent NWP SST. The warm NWP SST that promotes dry conditions in SWC is linked to three dynamical processes: (1) Warm NWP SST excites an anomalous cyclone over the South China Sea, which is oriented against the climatological flow, weakening the transportation of moisture from the NWP. (2) Warm NWP SST strengthens the westerlies along the equatorial Indian Ocean. As a result, most of the moisture is transported over the maritime continent and thus the poleward flow carrying moisture from the Indian Ocean into SWC becomes weaker. (3) Warm NWP SST provokes anomalous ascent and upper-level divergence in situ, with one path of the outflow heading northwestward and converging over SWC, which induces compensating subsidence over the SWC region. The results of numerical experiments, forced by SST anomalies in the NWP alone, are found to reproduce the observed atmospheric response, indicating that the impact of NWP SST on SWC precipitation is physical and that the moisture conditions over SWC are triggered primarily by the fluctuation of NWP SST. Due to the persistent SST anomaly over NWP from summer to autumn, the NWP SST in the preceding summer can be considered a predictor for autumn drought in SWC. Furthermore, autumn precipitation in SWC has experienced a significant decrease since 1994, probably maintained by the long-lasting warm NWP SST in recent decades.