Increasing the urban tree cover percentage(TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter d...Increasing the urban tree cover percentage(TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter days, depending on the physiological response of urban trees to rising ambient temperature. However, the response of urban trees' cooling efficiency to rising urban temperature remains poorly quantified for China's cities. In this study, we quantify the response of urban trees' cooling efficiency to rising urban temperature at noontime [~1330 LT(local time), LT=UTC+8] in 17summers(June, July, and August) from 2003–19 in 70 economically developed cities of China based on satellite observations. The results show that urban trees have stronger cooling efficiency with increasing temperature, suggesting additional cooling benefits provided by urban trees on hotter days. The enhanced cooling efficiency values of urban trees range from 0.002 to 0.055℃ %-1 per 1℃ increase in temperature across the selected cities, with larger values for the lowTCP-level cities. The response is also regulated by background temperature and precipitation, as the additional cooling benefit tends to be larger in warmer and wetter cities at the same TCP level. The positive response of urban trees' cooling efficiency to rising urban temperature is explained mainly by the stronger evapotranspiration of urban trees on hotter days.These results have important implications for alleviating urban heat risk by utilizing urban trees, particularly considering that extreme hot days are becoming more frequent in cities under global warming.展开更多
[Objective] The research aimed to analyze variation characteristics of the precipitation in Zigong City in recent 50 years.[Method] Based on daily precipitation data at three observation stations in Zigong City from 1...[Objective] The research aimed to analyze variation characteristics of the precipitation in Zigong City in recent 50 years.[Method] Based on daily precipitation data at three observation stations in Zigong City from 1961 to 2010,linear tendency method and accumulative anomaly method were adopted to analyze climatic change characteristics of the annual,seasonal,monthly rainfalls and rain days in Zigong City in recent 50 years.[Result]The annual rainfall overall presented a decreasing trend at the variation tendency rate of-28.0 mm /10 a in Zigong City.The annual rain days obviously declined at the variation tendency rate of-5.6 d /10 a.The decline of rain days was more obvious than that of the rainfall.Decline of the light rain days was especially serious.Not only trends of summer,autumn and winter rainfalls were all negative,but also trends of the four-season rain days were all negative.Reductions of autumn rainfall and rain days were the most remarkable and the largest in magnitude.Monthly rainfall presented single-peak type distribution,and monthly rain days presented double-peak type distribution.Days of each-level precipitation within one year in each area of Zigong City were nearly consistent.Moreover,rain days decreased as magnitude increased.An obvious characteristic of the precipitation variation in Zigong City in recent 50 years was synchronal decrease of the annual rainfall and rain days.[Conclusion]In general,the natural rainfall resource in Zigong City was tending to reduce,and autumn drought was obvious.展开更多
[Objective] The research aimed to study climatic characteristics of the thunderstorm days in Heze in recent 51 years. [Method] Using observation data of the thunderstorm days in Heze from 1961 to 2011, interannual and...[Objective] The research aimed to study climatic characteristics of the thunderstorm days in Heze in recent 51 years. [Method] Using observation data of the thunderstorm days in Heze from 1961 to 2011, interannual and monthly change characteristics of the thunderstorm days, change trends of the first and final dates, interannual stage distribution were analyzed. [Result] Annual average thunderstorm days in Heze was 25 d. As decade increase, thunderstorm days decreased at 1.9 d/10 a. Thunderstorm days concentrated from April to September, and occurred most often in July. The minimum days from first date to final date was 86 d, and the most days was 264 d. Average first date of the thunderstorm was on April 16, and final date was on September 16. Climatic characteristics of the thunderstorm had significant stage. [Conclusion] The research provided scientific basis for prediction, assessment, prevention and reduction of the thunderstorm disaster in Heze.展开更多
Land suitability assessment is a prerequisite phase in land use planning; it guides toward optimal land use by providing information on the opportunities and constraints involved in the use of a given land area. A geo...Land suitability assessment is a prerequisite phase in land use planning; it guides toward optimal land use by providing information on the opportunities and constraints involved in the use of a given land area. A geographic information system-based procedure, known as rural settlement suitability evaluation(RSSE) using an improved technique for order preference by similarity to ideal solution(TOPSIS), was adopted to determine the most suitable area for constructing rural settlements in different geographical locations. Given the distribution and independence of rural settlements, a distinctive evaluation criteria system that differed from that of urban suitability was established by considering the level of rural infrastructure services as well as living and working conditions. The unpredictable mutual interference among evaluation factors has been found in practical works. An improved TOPSIS using Mahalanobis distance was applied to solve the unpredictable correlation among the criteria in a suitability evaluation. Uncertainty and sensitivity analyses obtained via Monte Carlo simulation were performed to examine the robustness of the model. Daye, a resource-based city with rapid economic development, unsatisfied rural development, and geological environmental problems caused by mining, was used as a case study. Results indicate the following findings: 1) The RSSE model using the improved TOPSIS can assess the suitability of rural settlements, and the suitability maps generated using the improved TOPSIS have higher information density than those generated using traditional TOPSIS. The robustness of the model is improved, and the uncertainty is reduced in the suitability results. 2) Highly suitable land is mainly distributed in the northeast of the study area, and the majority of which is cultivated land, thereby leading to tremendous pressure on the loss of cultivated land. 3) Lastly, 12.54% of the constructive expansion permitted zone and 8.36% of the constructive expansion conditionally permitted zone are situated in an unsuitable area, which indicates that the general planning of Daye lacks the necessary verification of suitability evaluation. Guidance is provided on the development strategy of rural settlement patches to support decision making in general land use planning.展开更多
基金supported by the Natural Science Foundation of Jiangsu Province (Grant No. BK20240170)Open fund by Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control (KHK2203)+2 种基金the Jiangsu Meteorological Bureau Youth Fund (KQ202314)the Fundamental Research Funds for the Central Universities (2024300330)Jiangsu Collaborative Innovation Center for Climate Change。
文摘Increasing the urban tree cover percentage(TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter days, depending on the physiological response of urban trees to rising ambient temperature. However, the response of urban trees' cooling efficiency to rising urban temperature remains poorly quantified for China's cities. In this study, we quantify the response of urban trees' cooling efficiency to rising urban temperature at noontime [~1330 LT(local time), LT=UTC+8] in 17summers(June, July, and August) from 2003–19 in 70 economically developed cities of China based on satellite observations. The results show that urban trees have stronger cooling efficiency with increasing temperature, suggesting additional cooling benefits provided by urban trees on hotter days. The enhanced cooling efficiency values of urban trees range from 0.002 to 0.055℃ %-1 per 1℃ increase in temperature across the selected cities, with larger values for the lowTCP-level cities. The response is also regulated by background temperature and precipitation, as the additional cooling benefit tends to be larger in warmer and wetter cities at the same TCP level. The positive response of urban trees' cooling efficiency to rising urban temperature is explained mainly by the stronger evapotranspiration of urban trees on hotter days.These results have important implications for alleviating urban heat risk by utilizing urban trees, particularly considering that extreme hot days are becoming more frequent in cities under global warming.
文摘[Objective] The research aimed to analyze variation characteristics of the precipitation in Zigong City in recent 50 years.[Method] Based on daily precipitation data at three observation stations in Zigong City from 1961 to 2010,linear tendency method and accumulative anomaly method were adopted to analyze climatic change characteristics of the annual,seasonal,monthly rainfalls and rain days in Zigong City in recent 50 years.[Result]The annual rainfall overall presented a decreasing trend at the variation tendency rate of-28.0 mm /10 a in Zigong City.The annual rain days obviously declined at the variation tendency rate of-5.6 d /10 a.The decline of rain days was more obvious than that of the rainfall.Decline of the light rain days was especially serious.Not only trends of summer,autumn and winter rainfalls were all negative,but also trends of the four-season rain days were all negative.Reductions of autumn rainfall and rain days were the most remarkable and the largest in magnitude.Monthly rainfall presented single-peak type distribution,and monthly rain days presented double-peak type distribution.Days of each-level precipitation within one year in each area of Zigong City were nearly consistent.Moreover,rain days decreased as magnitude increased.An obvious characteristic of the precipitation variation in Zigong City in recent 50 years was synchronal decrease of the annual rainfall and rain days.[Conclusion]In general,the natural rainfall resource in Zigong City was tending to reduce,and autumn drought was obvious.
文摘[Objective] The research aimed to study climatic characteristics of the thunderstorm days in Heze in recent 51 years. [Method] Using observation data of the thunderstorm days in Heze from 1961 to 2011, interannual and monthly change characteristics of the thunderstorm days, change trends of the first and final dates, interannual stage distribution were analyzed. [Result] Annual average thunderstorm days in Heze was 25 d. As decade increase, thunderstorm days decreased at 1.9 d/10 a. Thunderstorm days concentrated from April to September, and occurred most often in July. The minimum days from first date to final date was 86 d, and the most days was 264 d. Average first date of the thunderstorm was on April 16, and final date was on September 16. Climatic characteristics of the thunderstorm had significant stage. [Conclusion] The research provided scientific basis for prediction, assessment, prevention and reduction of the thunderstorm disaster in Heze.
基金Under the auspices of National Natural Science Foundation of China(No.41371429,41401196)
文摘Land suitability assessment is a prerequisite phase in land use planning; it guides toward optimal land use by providing information on the opportunities and constraints involved in the use of a given land area. A geographic information system-based procedure, known as rural settlement suitability evaluation(RSSE) using an improved technique for order preference by similarity to ideal solution(TOPSIS), was adopted to determine the most suitable area for constructing rural settlements in different geographical locations. Given the distribution and independence of rural settlements, a distinctive evaluation criteria system that differed from that of urban suitability was established by considering the level of rural infrastructure services as well as living and working conditions. The unpredictable mutual interference among evaluation factors has been found in practical works. An improved TOPSIS using Mahalanobis distance was applied to solve the unpredictable correlation among the criteria in a suitability evaluation. Uncertainty and sensitivity analyses obtained via Monte Carlo simulation were performed to examine the robustness of the model. Daye, a resource-based city with rapid economic development, unsatisfied rural development, and geological environmental problems caused by mining, was used as a case study. Results indicate the following findings: 1) The RSSE model using the improved TOPSIS can assess the suitability of rural settlements, and the suitability maps generated using the improved TOPSIS have higher information density than those generated using traditional TOPSIS. The robustness of the model is improved, and the uncertainty is reduced in the suitability results. 2) Highly suitable land is mainly distributed in the northeast of the study area, and the majority of which is cultivated land, thereby leading to tremendous pressure on the loss of cultivated land. 3) Lastly, 12.54% of the constructive expansion permitted zone and 8.36% of the constructive expansion conditionally permitted zone are situated in an unsuitable area, which indicates that the general planning of Daye lacks the necessary verification of suitability evaluation. Guidance is provided on the development strategy of rural settlement patches to support decision making in general land use planning.
