Extreme Minimum Temperature Research Articles

Changes of extreme high temperature and heavy precipitation in the Guangdong-Hong Kong-Macao Greater Bay Area

The changes of extreme high temperature and heavy precipitation events in the Guangdong-Hong Kong-Macao Greater Bay Area from 1961 to 2019 are analyzed in this paper. Based on the high-resolution climate projection simulations, this study also projects the future risks of heat and flood disasters. The results indicate that hot days, hot nights, heat wave durations, extreme daily maximum and minimum temperature have increased significantly at the rates of 3.6 d/10a, 6.0 d/10a, 2.1 d/10a, 0.23 °C/10a and 0.21 °C/10a, respectively. The heavy and very heavy precipitation days, extreme precipitation amount, maximum 1-day and 5-day precipitation amount have increased by 0.6 days, 0.2 days, 12.5 mm, 0.7 mm and 3.5 mm per 10 years, respectively. All the extreme indices will keep increase at similar rates. In the mid-21st, the area with highest heat and flood risks shows an increase by a factor of 10, mainly located in Guangzhou, Foshan, Dongguan, Shenzhen, Hong Kong and the northern part of Zhongshan. The area proportions of the highest two risk levels of heat and flood disasters will be as high as 66% and 60%, respectively. Considering both high climate risks and urbanization developments, it is necessary to improve the resistance to extremes and enhance the resilience of society to these extreme disasters.

中国欧亚种酿酒葡萄种植分布的主要气候影响因子与气候适宜性

开展酿酒葡萄气候适宜性研究对于优化酿酒葡萄布局、气候资源开发利用具有重要意义。基于欧亚种酿酒葡萄（Vitis vinifera L.）分布数据和影响其分布的气候因子，利用最大熵模型（MaxEnt）和地理信息系统（ArcGIS），研究影响欧亚种酿酒葡萄种植分布的主导气候因子及其气候适宜性。结果表明：MaxEnt模型能够很好地模拟我国欧亚种酿酒葡萄的潜在分布，模拟效果达到"非常好"（AUC平均值0.936）的水平。基于气候因子对欧亚种酿酒葡萄地理分布影响的贡献确定了主导气候因子，即无霜期、干燥度、极端最低气温、年降水量、生长季日照时数、≥10℃活动积温。当前，我国欧亚种酿酒葡萄种植分布的气候高适宜区、适宜区、次适宜区分别占次适宜及以上区域总面积的2.9%、20.4%和76.7%。欧亚种酿酒葡萄气候高适宜区主要分布在宁夏、山西、陕西、内蒙古、山东、河北、新疆、甘肃等省，只考虑气候因子，陕西、山西、内蒙古具有较大的发展空间。;Study of the climatic suitability for the wine grapes has great significance for optimizing the distribution of wine grapes and the utilization of climate resources. Based on the geographical distribution data of wine grapes (Vitis vinifera L.) and the climatic factors affecting the distribution of wine grapes, the Maximum Entropy model (MaxEnt) and Geographic Information Systems (ArcGIS) were used to identify the dominant climatic factors affecting the planting distribution and study the climatic suitability of wine grapes. The results indicated that the MaxEnt model could well simulate the potential distribution of wine grapes in China, and the assessment result was excellent with the average AUC 0.936. The contribution of climate factors to the geographical distribution of the wine grape was evaluated by Jackknife tests in the modeling analysis. The frost-free period, aridity index, annual extreme minimum temperature, annual precipitation, sunshine duration of growing season, and ≥10 ℃ accumulated temperature were the main dominant climatic factors affecting the spatial distribution for wine grapes. At present, the areas of optimum, suitable and sub-suitable subregions for growing wine grapes (Vitis vinifera L.) accounted for 2.9%, 20.4% and 76.7%, respectively, to the total climate suitable planting area. The optimum area was mainly distributed in Ningxia, Shaanxi, Shanxi, Inner Mongolia, Shandong, Hebei, Xinjiang, and Gansu, considering only climatic factors, Shaanxi, Shanxi and Inner Mongolia had a large development room.

Analysis of Climate Change and Extreme Climatic Events in the Lake Victoria Region of Tanzania

The understanding of climate change impacts and the associated climate extreme events at regional and local scales is of critical importance for planning and development of feasible adaptation strategies. In this paper, we present an analysis of climate change and extreme climate events in the Lake Victoria region of Tanzania, focusing on the Kagera and Geita regions. We use daily simulated climate variables (rainfall and minimum and maximum temperatures) from the Coordinated Regional Climate Downscaling Experiment Program Regional Climate Models (CORDEX_RCMs) for the analysis. Extreme climate event, rainfall, and minimum and maximum temperatures time series during historical (1971–2000) climate condition are compared to future climate projection (2011–2100) under two Representative Concentration Pathway (RCP): RCP 4.5 and RCP 8.5 emission scenarios. The existence, magnitude, and statistical significance of potential trends in climate data time series are estimated using the Mann–Kendall (MK) non-parametric test and Theil-SEN slope estimator methods. Results show that during historical (1971–2000) climate, the Lake Victoria region of Tanzania experienced a statistically significant increasing trend in temperature. The annual minimum and maximum temperatures in the Kagera and Geita regions have increased by 0.54–0.69°C, and 0.51–0.69°C, respectively. The numbers of warm days (TX90p) and warm nights (TN90p) during the historical climate have increased, while the numbers of cold days (TX10p) and cold nights (TN10p) have decreased significantly. However, in future climate condition (2011–2100) under both RCP 4.5 and RCP 8.5 emission scenarios, the Lake Victoria region is likely to experience increased temperatures and rainfall. The frequency of cold events (cold days and cold nights) is likely to decrease, while the frequency of warm events (warm days and warm nights) is likely to increase significantly. The number of consecutive wet days, the intensity of very wet days, and the number of extreme wet days are likely to increase. These results indicate that in future climate condition, socioeconomic livelihoods of people in the Kagera and Geita regions are likely to experience significant challenges from climate-related stresses. It is, therefore, recommended that appropriate planning and effective adaptation policies are in place for disaster risk prevention.

Extreme temperatures linked to the atmospheric blocking events in Turkey between 1977 and 2016

Extreme maximum (Tx) and extreme minimum temperature (Tn) frequency distributions during summer and winter for blocked conditions were analyzed within Turkey during the period from 1977 to 2016 by using observational data. The Tx (0.5–0.8%) and Tn (0.4–2.0%) frequencies vary between these values for the entire period during summer. However, Tx varies between 0.0 and 1.0, while Tn varies between 0.8 and 2.4 during winter. It is quite clear that atmospheric blocking has a greater cooling effect during winter. The maximum values for Tx and Tn are observed when the block center located within the easternmost sector impacting Turkey for summer. The maximum Tx frequency is observed in association with blocking in the westernmost sector, and the maximum Tn frequency is observed with blocking in the easternmost sector impacting Turkey during the winter season. Block intensity has almost no impact on Tx frequency although it has enhancing effect on Tn frequency during the summer. For winter, block intensity has a decreasing effect on both the maximum Tn and maximum Tx. The maximum Tx and Tn values increase with the block size for the summer. During the winter, the maximum Tx frequency decreases with the increase in the size of a blocking event; however, the greatest Tn frequency is observed within the 0°–30° E sector and lowest within the 30° E–60° E sector. The block duration has an enhancing influence on the maximum Tx value, while maximum Tn is observed during short-duration events and a minimum is observed during moderate-duration events during the summer season. For the winter season, the block duration has a decreasing effect for Tx frequencies and increasing effect for Tn.

Current agro-climatic potential of Patagonia shaped by thermal and hydric patterns

Changes in thermal and hydric patterns affect crop growth. This research is aimed to assess temporal and spatial trends of 18 climatic and agro-climatic thermal and hydric indices in the north of Argentine Patagonia (39°–44°, south latitude), to establish the current and potential suitability of this region for agriculture in a context of climate change. The period of study was 1970–2016, and it was focused on the last 20 years. Regional warming was indicated by the average increases of annual mean temperature (+ 0.2 °C decade−1), mean maximum temperature of the warm trimester (+ 0.3 °C decade−1), and extreme maximum temperature of the warmest month (+ 0.6 °C decade−1) during 1970–2016. This trend was also found in the 1996–2017 period. Mean minimum temperature of the cold trimester showed an uneven spatial and temporal trend, with increasing temperatures during 1970–2016 (+ 0.1 °C decade−1), but a negative trend (− 0.1 °C decade−1) over the last 20 years, which leads to an increasing regional trend in temperature amplitude. Negative trends in extreme minimum temperatures of April (− 0.3 °C decade−1), July and October (− 0.2 °C decade−1) imply more significant risks of cold damage for crops that exhibit sensitive phenological stages during this time. Thermal agro-climatic indices showed negative trends in winter chill (− 15.8 chill hours decade−1 considering the Weinberger method and − 20.8 chill hours decade−1 using Sharpe method) and higher accumulation of warm semester growing degree days (+ 38.8 GDD5 °C and + 32.3 GDD10 °C decade−1). Climatic and agro-climatic water indices showed that most of the region experienced decreasing water availability, mainly in the central-south and Andean subregions, showing annual precipitation trends of − 11.5 and − 31.2 mm decade−1, respectively). If these thermal and hydric trends are maintained in the future, the region will evolve into an area of greater energetic availability but with some restrictions: lower winter chill that would affect very high-chill cultivars cultivated in the warmest regions, higher risk of extreme thermal events during crucial phenological periods of specific crops, and decreasing water availability that would mainly affect dryland farming and river basin recharge.

Effects of Urbanization on Regional Extreme-Temperature Changes in China, 1960–2016

Urbanization in China has been expanding dramatically since 1978, significantly affecting the extreme temperature changes in cities, which is a vital indicator of urban climate change. To assess urban-related effect on regional extreme-temperature changes in China, this study employed high-resolution land use data to divide meteorological stations into rural stations, suburban stations, and urban stations, and evaluated the annual and seasonal changes in extreme minimum temperature (TNN), mean temperature (Tavg) and extreme maximum temperature (TXX) at each meteorological station. The result revealed that extreme temperature indices (TNN, TXX) and Tavg increased significantly from 1960 to 2016 with varied degrees in different seasons and different regions. Extreme temperature indices in high latitudes increased more rapidly than in low latitudes; while the trends in summer are slower than in other seasons. Urbanization effects on the trends of TNN, Tavg and TXX were all statistically significant, but urbanization effects on TNN and Tavg were more significant than TXX. The urbanization effects were more significant in low altitudes, especially in North, South, Northwest and Northeast China. In North, Northwest and Northeast China, the urban-related effects on temperature increase were mainly observed in spring and winter, but in South China, the urban-related effects were more evident in summer. This study is valuable for sustainable urban planning in China.

Comparison of Cold Hardiness Evaluation of Woody Species by ELLT and TTCLT

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT50) using electrolyte leakage test (ELLT50) and triphenyltetrazolium chloride test (TTCLT50) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT50 was lower than the xylem TTCLT50, and the two sds were similar. The ELLT50 showed no significant correlation with any TTCLT50. For most species, the ELLT50 was higher than the cambium and phloem TTCLT50 and was not significant different with the xylem TTCLT50. The ELLT50 showed higher sd than any tissue TTCLT50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT50.

Projected impacts of climate change on the range and phenology of three culturally-important shrub species.

Climate change is shifting both the habitat suitability and the timing of critical biological events, such as flowering and fruiting, for plant species across the globe. Here, we ask how both the distribution and phenology of three food-producing shrubs native to northwestern North America might shift as the climate changes. To address this question, we compared gridded climate data with species location data to identify climate variables that best predicted the current bioclimatic niches of beaked hazelnut (Corylus cornuta), Oregon grape (Mahonia aquifolium), and salal (Gaultheria shallon). We also developed thermal-sum models for the timing of flowering and fruit ripening for these species. We then used multi-model ensemble future climate projections to estimate how species range and phenology may change under future conditions. Modelling efforts showed extreme minimum temperature, climate moisture deficit, and mean summer precipitation were predictive of climatic suitability across all three species. Future bioclimatic niche models project substantial reductions in habitat suitability across the lower elevation and southern portions of the species' current ranges by the end of the 21st century. Thermal-sum phenology models for these species indicate that flowering and the ripening of fruits and nuts will advance an average of 25 days by the mid-21st century, and 36 days by the late-21st century under a high emissions scenario (RCP 8.5). Future changes in the climatic niche and phenology of these important food-producing species may alter trophic relationships, with cascading impacts on regional ecosystems.

Realised added value in dynamical downscaling of Australian climate change

Coarse resolution global climate models (GCMs) cannot resolve fine-scale drivers of regional climate, which is the scale where climate adaptation decisions are made. Regional climate models (RCMs) generate high-resolution projections by dynamically downscaling GCM outputs. However, evidence of where and when downscaling provides new information about both the current climate (added value, AV) and projected climate change signals, relative to driving data, is lacking. Seasons and locations where CORDEX-Australasia ERA-Interim and GCM-driven RCMs show AV for mean and extreme precipitation and temperature are identified. A new concept is introduced, ‘realised added value’, that identifies where and when RCMs simultaneously add value in the present climate and project a different climate change signal, thus suggesting plausible improvements in future climate projections by RCMs. ERA-Interim-driven RCMs add value to the simulation of summer-time mean precipitation, especially over northern and eastern Australia. GCM-driven RCMs show AV for precipitation over complex orography in south-eastern Australia during winter and widespread AV for mean and extreme minimum temperature during both seasons, especially over coastal and high-altitude areas. RCM projections of decreased winter rainfall over the Australian Alps and decreased summer rainfall over northern Australia are collocated with notable realised added value. Realised added value averaged across models, variables, seasons and statistics is evident across the majority of Australia and shows where plausible improvements in future climate projections are conferred by RCMs. This assessment of varying RCM capabilities to provide realised added value to GCM projections can be applied globally to inform climate adaptation and model development.

Changes in temperature and rainfall extremes across East Asia in the CMIP5 ensemble

We analyze annual extremes of daily maximum and minimum surface air temperature and of daily rainfall in East Asia and the Korean peninsula. This study made intensive use of the simulation data available from the CMIP5 (Coupled Model Intercomparison Project Phase 5) multimodels in historical and future experiments up to the year 2100, employing three different radiative forcings: RCP2.6, RCP4.5, and RCP8.5 (representative concentration pathways). Several reanalysis datasets are used to compare and evaluate the simulated climate extremes in the late twentieth century. We estimate the future changes in precipitation and temperature extremes in East Asia and Korea, and compare them to the global result, for the reference period 1986–2005. The rising rate of future cold extremes over East Asia and Korea is faster than that of warm extremes. This phenomenon appears more distinctly in Korea as a local scale, indicating more sensitivity of the Korean peninsula to global warming. The increase of the 20-year return level of maximum precipitation in the CMIP5 over East Asia by the end of twenty-first century is about 7% in the RCP2.6, 15% in the RCP4.5, and 35% in the RCP8.5 experiments, which exceed the corresponding global values. We also estimate the changes in precipitation extremes across East Asia as a function of the annual mean temperature variation at the same location. The CMIP5 sensitivity in maximum precipitation across East Asia is 5.5%/∘C, which is lower than the global figure (5.8%/∘C). The sensitivity for the Korean peninsula is 7.38%/∘C, indicating the strong impact of global warming to Korea. The results will be important in mitigating the detrimental effects of variations of climatic extremes and in improving the regional strategy for water resource and eco-environmental management, particularly for such areas in East Asia under significant changes in temperature and rainfall extremes.

ROUTINE, EXTREME AND ENGINEERING METEOROLOGY ANALYSIS FOR KARACHI COASTAL AREA

Pakistan’s largest city, Karachi, which is industrial centre and economic hub needs focus in research and development of every field of Engineering, Science and Technology. Urbanization and industrialization is resulting bad weather conditions which prolongs until a climate change. Since, Meteorology serves as interdisciplinary field of study, an analytical study of real and region-specific meteorological data is conducted which focuses on routine, extreme and engineering meteorology of metropolitan city Karachi. Results of study endorse the meteorological parameters relationship and establish the variability of those parameters for Karachi Coastal Area. The rise of temperature, decreasing trend of atmospheric pressure, increment in precipitation and fall in relative humidity depict the effects of urbanization and industrialization. The recorded extreme maximum temperature of 45.50C (on June 11, 1988) and the extreme minimum temperature of 4.5 0C(on January 1, 2007) is observed at Karachi south meteorological station. The estimated temperature rise in 32 years is 0.9 0C, which is crossing the Intergovernmental Panel on Climate Change (IPCC) predicted/estimated limit of 2oC rise per century. The maximum annual precipitation of 487.0mm appearing in 1994 and the minimum annual precipitation of 2.5mm appearing in 1987 is observed at same station which is representative meteorological station for Karachi Coast. Further Engineering meteorological parameters for heating ventilation air condition (HVAC) system design for industrial purpose are deduced as supporting data for coastal area site study for industrial as well as any follow-up engineering work in the specified region.

Evaluation of selected global climate models for extreme temperature events over India

Extreme temperature events derived from the global climate models (GCMs) are used for climate change impact studies in several sectors, especially in agriculture. Reducing the uncertainty in simulated crop yields based on extreme temperatures is an important task for reliable and relevant adaptation decisions. This study compared the performance of selected six global climate models in simulating temperature extreme events over Indian region for the 1976–2005 period. For this, performance statistics such as root mean square error, correlation coefficient, and agreement index were compared spatially and spatiotemporally. The study reveals that all the six models overestimate minimum and maximum temperature extremes for most parts of Central India, which resulted in hot bias. However, these models show a cold bias in simulating low temperature extremes over the Himalayan region. Further the study indicates that GFDL-ESM2M and MIROC-ESM-CHEM have performed relatively better in capturing temperature extreme events over Indian region among the six models that were found to closely simulate the observed climatology.

Selection for Winter Survivorship in Lowland Switchgrass

Development of switchgrass (Panicum virgatum L.) as a sustainable biomass crop for conversion to bioenergy requires substantial increases in biomass yield. Because switchgrass is highly photoperiodic, one approach toward this goal is to collect germplasm populations from the Southern USA, then screen and select them in northern environments where they represent a delay in flowering time of up to 6 weeks compared with local ecotypes. This delay in flowering has been linked to increases in biomass yield of up to 50%. The objective of this study was to conduct and evaluate selection progress for winter survivorship in 14 southern lowland populations of switchgrass. The populations originated from USDA Plant Hardiness Zones (PHZ) 7 or 8 (mean annual extreme minimum temperature = − 12.2 °C) and the selection and evaluation were conducted in PHZ 4 or 5 (mean annual extreme minimum temperature = − 28.8 °C). Seven of the 14 populations responded to selection, with increases in winter survivorship and/or biomass yield across four evaluation locations. Winter survivorship and biomass yield were highly correlated with each other, so that increases in survivorship usually translated to increases in biomass yield. The top-ranked population represented the third cycle of selection within the cultivar Kanlow, indicating that the greatest gains from selection represented longer-term efforts than a single generation of field-based selection. This study verified that alleles for winter survivorship and plants capable of surviving in PHZ 4 or 5 can be found across a broad geographic area in the Southern USA, albeit at very low frequencies in most populations.

Changes in the frequency of hot, humid days and nights in the Mississippi River Basin

AbstractThe severe impacts of climate change on human health will rise from the co‐occurrence of extreme humid and hot conditions. In this study, six indices associated with high humidity, maximum and minimum daytime and nighttime temperature and the heat index (HI) values were analysed to assess temporal changes in hot, humid conditions in the Mississippi River Basin (MRB), USA, for the period 1948–2017. The frequencies of extreme humid days and nights have significant upward trends over 97 and 93% of MRB, respectively. Trends of day‐time HI were mainly upward (63%), except for eastern regions of MRB. More of the upward trends for the frequency of hot nights were significant than the trends for hot days either for the entire period (72% of MRB for hot nights and 4% for hot days) or after a significant change‐point (26% of MRB for hot nights and 20% for hot days). Except for minimum HI, other indices including extreme maximum and minimum temperature and specific humidity as well as maximum HI had an upward trend after the 1980s and 1990s for the majority of grid‐cells. Central and southern areas of the MRB were identified as regions most at risk for an extreme HI value during both days and nights.

Climatic suitability for the distribution of Vitis heyneana and V. davidii in China

Vitis heyneana and V. davidii are two wild wine grape varieties that originate from China. In this study, we used the principle of maximum entropy in terms of sufficiency and necessity to identify the dominant climatic factors (among the many climatic factors that were brought up by previous relevant studies) affecting the planting distribution of both varieties in China. Based on the probability of planting distribution determined by the comprehensive effect of these dominant climatic factors, we further analyzed the climatic suitability in China for both wild varieties. The results showed that the four dominant climatic factors affecting the spatial distribution of both varieties were annual sunshine duration, precipitation during the flowering stage in May, annual extreme minimum temperature, and average temperature during the coldest month of January. The optimal wine grape-growing subregions for both varieties were mainly located in the western and southern parts of Hunan, the north-central part of Guangxi, the southeastern part of Guizhou, and the central part of Chongqing. The areas of optimal, suitable, and sub-suitable subregions for planting V. heyneana and V. davidii accounted for 2%, 14%, and 16% of the total area of the research region, respectively. In the optimal/suitable subregions for planting both varieties, annual sunshine duration was between 1200-1800 h, annual extreme minimum temperature was above -8 ℃, average temperature during the coldest month of January was between 2-13 ℃, and monthly precipitation in May was between 110-320 mm.

Estimation of mean annual extreme minimum temperature raster and predicting the potential distribution for <i>Ipomoea triloba</i> using Proto3 model in the Korean peninsula

Estimation of mean annual extreme minimum temperature raster and predicting the potential distribution for <i>Ipomoea triloba</i> using Proto3 model in the Korean peninsula

The Relationship between the Wintertime Cold Extremes over East Asia with Large-Scale Atmospheric and Oceanic Teleconnections

The influence of large-scale teleconnection patterns, Western Pacific (WP), Arctic Oscillation (AO) and El Niño-Southern Oscillation (ENSO), on the minimum surface air temperature (Tmin) anomalies and extremes over East Asia during the boreal winter from 1979 to 2017 were investigated by the composite analysis in terms of atmospheric and oceanic processes. The relationship between the Tmin and the geopotential height at 500 hPa (Z500) as well as sea surface temperature (SST) were first examined. Then we explored and estimated the contribution of the teleconnection patterns to the occurrence of extremely cold days and months quantitatively, and discussed other key factors in relation to the cold extremes. The WP and AO patterns play an important part in the prevalence of significant Tmin variability, whereas the effect of ENSO is relatively weak. Most of the cold extremes tend to appear in the negative phase of teleconnections, while there some extremes that occur in the opposite phase. In addition, the extreme months are more related to the preferred phase of the dominant pattern when compared to days. We conclude that the daily extremes are primarily triggered by the local-synoptic atmospheric circulations embedded in the large-scale teleconnection patterns, while the monthly extremes have a closer relationship with these low-frequency patterns.

Driving forces of changes in China’s wetland area from the first (1999–2001) to second (2009–2011) National Inventory of Wetland Resources

Based on the wetland areas recorded in the First National Inventory of Wetland Resources (FNIWR; 1999–2001) and the Second National Inventory of Wetland Resources (SNIWR; 2009–2011), as well as regional environmental parameters including meteorological conditions and land-use structure, the driving forces of changes in China’s wetland area from the FNIWR to the SNIWR were investigated. The total area of China’s wetlands larger than 1 km2 decreased from 384.8 × 103 km2 in the FNIWR to 350.8 × 103 km2 in the SNIWR. Natural wetland areas, including marshes, rivers, lakes, and coastal wetlands, decreased by 33.8 × 103 km2 over the study period, accounting for 99.4% of the decrease in the wetland area. Regions with decreased marsh and reservoir wetland areas were located mainly in Central and Eastern China, and those with increased river and lake wetland areas were located in Western China. There were no significant regression coefficients between the percentages of change in marsh and lake wetland areas and environmental parameters. However, changes in river wetland areas were positively regressed with changes in forest areas, mean annual temperature, and extreme minimum temperature, and changes in reservoir wetland areas were positively regressed with changes in city construction areas and mean annual temperature. Therefore, it seems that increased forest area and regional temperature alleviated the degradation of river wetland areas, while increased city construction areas and regional temperature alleviated the degradation of reservoir areas.

Change of extreme chilling and its impact on winter planting in Guangdong Province, China

Based on daily temperature data of 86 weather stations during winter producing season from 1961 to 2017 in Guangdong Province, the temporal and spatial distribution of extreme chilling was analyzed. The return periods of extreme chilling at county level were calculated with the theory of generalized extreme value distribution to provide technical support for extreme chilling risk assessment and early warning together with real-time meteorological disaster prevention and mitigation in winter planting areas. Results showed that there was a general downward trend of the extreme values of chilling accumulation in main winter planting zones. Zhanjiang and Meizhou had declined significantly since the mid-1980s, while Maoming, Shaoguan and Guangzhou had declined significantly since the 21st century. The extreme minimum temperature followed a curve trending generally downward first and upward later on, with a significant rising in Shaoguan from later 1980s while a descending in Guangzhou in the last five years. The order of the number of extreme value stations of chilling accumulation was 1970s ＞ the 21st century ＞ 1990s ＞ 1960s ＞ 1980s. The order of the number of stations of extreme minimum temperature was 1960s ＞ 1990s ＞ the 21st century ＞ 1970s ＞ 1980s. The theoretical forecast values of cold disaster of 2, 5, 10, 20, 50, and 100 year return period showed obvious zonal distribution characteristics. The chilling accumulation diminished from the north to the south and the extreme minimum temperature was higher in the south and lower in the north, which was consistent with the distribution trend in the actual occurrence of cold damage. Typical cases showed more extended chilling return periods in the south than in the north. In Zhanjiang and Maoming, the main producing areas of winter crops in Guangdong Province, the return period of cold damage was long, the probability of extreme cold damage was small but the damage was heavy, and the area of winter crops was in the front rank, which should be paid attention. Our results could provide scientific reference for local government and relevant departments in Guangdong Province to guide winter planting and develop countermeasures against climate change.

Development of a Submonthly Temperature Product to Monitor Near-Real-Time Climate Conditions and Assess Long-Term Heat Events in the United States

AbstractLand surface air temperature products have been essential for monitoring the evolution of the climate system. Before a temperature dataset is included in such analyses, it is important that nonclimatic influences be removed or changed so that the dataset is considered to be homogenous. These inhomogeneities include changes in station location, instrumentation, and observing practices. Many homogenized products exist on the monthly time scale, but few daily and weekly products exist. Recently, a submonthly homogenized dataset has been developed using data and software from NOAA’s National Centers for Environmental Information. Homogeneous daily data are useful for identification and attribution of extreme heat events. Projections of increasing temperatures are expected to result in corresponding increases in the frequency, duration, and intensity of such events. It is also established that heat events can have significant public health impacts, including increases in mortality and morbidity. The method to identify extreme heat events using daily homogeneous temperature data is described and used to develop a climatology of heat event onset, length, and severity. This climatology encompasses nearly 3000 extreme maximum and minimum temperature events across the United States since 1901. A sizeable number of events occurred during the Dust Bowl period of the 1930s; however, trend analysis shows an increase in heat event number and length since 1951. Overnight extreme minimum temperature events are increasing more than daytime maximum temperatures, and regional analysis shows that events are becoming much more prevalent in the western and southeastern parts of the United States.