Solvent-Free Synthesis of 5-Alkenyl-2,2-butylidene-1, 3-dioxane-4,6-diones under Ultrasonic Irradiation with o-Phthalimide-N-Sulfonic Acid as Catalyst

5-Alkenyl-2,2-butylidene-1,3-dioxane-4,6-diones were synthesized by the Knoevenagel condensation reaction of aromatic aldehydes with 2,2-butylidene-1,3-dioxane-4,6-dione using o-phthalimide-N-sulfonic acid as catalyst, without solvent under ultrasonic irradiation. The present method has some notable advantages such as mild reaction conditions, short reaction times, less catalyst dosage and high yields with the green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be reused for five times without any noticeable decrease in the catalytic activity.

Change of probability density distributions of summer temperatures in different climate zones

Extreme events have become increasingly frequent worldwide which are reflected in diverse changes in the shape of the temperature probability density function.However,few studies have paid attention to the heterogeneity of temperature at the scale of climate zones.Here,we use the ERA5-land data set to explore interdecadal summer temperature changes and the distribution across different climate zones from 1981 to 2019.Comparing the minimum(Tmin)and maximum(Tmax)temperature of 1982–1991 and 2010–2019,the results imply that Tmin and Tmax in summer maintained a notable upward trend over the past 40 years,especially Tmin.The effects of a simple shift toward a warmer climate contributed most to all climate zones,while the standard deviation,skewness and kurtosis had minor effects on extreme temperature except for tropics.Quantile analysis shows that the probability of extreme events in all climate zones is increasing in frequency and intensity,especially Tmin and Tmax in temperate climate zone.Understanding diverse reasons for climate change can assist us with taking different measures to address extreme climate in distinct climate zones.

Unequal urban heat burdens impede climate justice and equity goals

Extreme heat is among the deadliest of weather-related hazards,exerting far-reaching impacts on the natural environment and human society globally.Its risk has been rising worldwide over the past decades,particularly in densely populated urban settlements in which more than half the world’s population live.1,2 This rise is primarily attributed to anthropogenic greenhouse gas(GHG)emissions,of which the dominant share is contributed by the Global North.1 The Global North comprises economically developed countries with higher levels of industrialization,technology,infrastructures,energy consumption,and GHG emissions(e.g.,North America and West Europe)whose cities are major emission hotspots.1 Besides,emission transfers via international trade from the Global South,encompassing countries with lower economic development and energy consumption,higher poverty,and more vulnerable infrastructures(e.g.,India and Brazil)compared with the Global North,contribute a nonnegligible share of GHGs.

不同SSP-RCP情景下中国地区基于植被功能型分类的未来土地利用变化模拟

土地利用预测产品对于气候模型预测和评估未来土地利用变化的影响至关重要.但目前全球土地利用预测产品的空间分辨率仍太粗糙,难以满足区域气候模型在区域和局地尺度上的精度要求.因此,本研究旨在为中国区域提供一套基于最新SSP-RCP情景下可直接应用于区域气候变化研究的高分辨率土地利用变化预测产品.首先,基于LUH2数据集提取不同情景下中国地区不同用地类型数量的变化情况,并使用最新开发的土地利用模拟模型(FLUS)对2015~2100年期间1 km尺度下的未来土地利用变化进行模拟.在此基础上,对模拟结果按植被功能型进行重分类,并制作了不同情景下中国地区基于植被功能型分类的土地利用预测产品.该产品的空间分辨率为5 km,能更好地描述土地利用分布的细节,对于减少高分辨率区域气候模拟的不确定性将具有重要作用.

Quality Control and Evaluation of the Observed Daily Data in the North American Soil Moisture Database

The North American Soil Moisture Database (NASMD) was initiated in 2011 to assemble and homogenize in situ soil moisture measurements from 32 observational networks in the United States and Canada encompassing more than 1800 stations. Although statistical quality control (QC) procedures have been applied in the NASMD, the soil moisture content tends to be systematically underestimated by in situ sensors in frozen soils, and using a single maximum threshold (i.e., 0.6 m3 m-3) may not be sufficient for robust QC because of the diverse soil textures in North America. In this study, based on the in situ soil porosity and North American Land Data Assimilation System phase 2 (NLDAS-2) Noah soil temperature, the simple automated QC method is revised to supplement the existing QC approach. This revised QC method is first validated based on the assessment at 78 of the Soil Climate Analysis Network (SCAN) stations where the manually checked data are available, and is then applied to all stations in the NASMD to produce a more strict quality-controlled dataset. The results show that the revised automated QC procedure can flag the spurious and erroneous soil moisture measurements for the SCAN stations, especially for those located in high altitudes and latitudes. Relative to station measurements in the original NASMD, the quality-controlled data show a slightly better agreement with the manually checked soil moisture content. It should be noted that this quality-controlled dataset may be over-flagged for some valid soil moisture measurements due to potential errors of the soil temperature and soil porosity data, and validation in this study is limited by the availability of benchmark soil moisture data. The updated QC and additional validation will be desirable to boost confidence in the product when high-quality data become available in the future.