联合国政府间气候变化专门委员会(IPCC) 于2019年8月8日正式发布《气候变化与陆地特别报告》(SRCCL)，贾根锁研究员作为报告的主要作者协调人(CLA)，负责协调和撰写报告第二章-陆地与气候相互作用(Land-climate interactions) (详见IPCC SRCCL | 联合国新闻)。

贾根锁研究员在国际科学理事会（ICSU）第118次执委会会议上当选其亚太区域委员会 (RCAP)委员，同时担任区域灾害风险工作组成员 (详见中国科协简讯 | 中国科学院简讯)。

第四次《气候变化国家评估报告》撰写工作近日启动。贾根锁研究员被聘任为报告首席专家之一，负责“土地覆盖变化以及对气候变化的影响”部分的编写协调工作。

中国科学院战略先导专项A类-地球大数据科学工程(CASEarth, 2018-2022)正式启动，贾根锁研究员担任专项方案规划工作组组长、以及项目三课题四负责人 (详见专项主页)。

2017年2月，联合国环境署启动了全球环境展望(GEO-6)全球评估报告进程，中国科学院大气物理研究所贾根锁研究员被遴选为主要作者协调人(CLA)，负责协调和撰写第八章-陆地环境。

数字一带一路（DBAR）国际科学计划启动，这一大型国际科学计划基于空间观测科学认知“一带一路”，旨在为“一带一路”建设提供科学、开放和合作的可持续发展信息决策支持。贾根锁研究员当选DBAR国际科学计划科学委员会委员和环境变化工作组共同主席（详见《数字一带一路科学规划》发布）。

1. Improving meteorological drought monitoring capability over tropical and subtropical water-limited ecosystems: evaluation and ensemble of the Microwave Integrated Drought Index
   Zhang, A., G. Jia*, H. Wang. Environmental Research Letters: 2019 ,14(4) ,044025, doi: 10.1088/1748-9326/ab005e 摘要  The monitoring of meteorological drought is critically important for tropical and subtropical water- limited ecosystems, which play key roles in the global carbon cycle and ecosystem services. Satellite remote sensing is the only practical approach for tracking drought changes with high resolution and an instantaneous response. However, the application of remote sensing drought indices derived from optical and infrared bands has been constrained due to cloud contamination. Here the Microwave Integrated Drought Index (MIDI), a multi-sensor microwave remote sensing drought index integrating state-of-the-art multiple satellite microwave-derived precipitation, soil moisture and land surface temperature information, was processed to improve the meteorological drought monitoring capability of satellite remote sensing. The index was evaluated against the 1 to 12 month field-based drought indicators Standardized Precipitation Index (SPI) and Standardized Precipitation Evapo- transpiration Index (SPEI) and anomalies in the satellite-derived Enhanced Vegetation Index (EVI) from 1998 to 2014. MIDI with an optimal ensemble of multiple satellite precipitation products showed a better improvement in meteorological drought monitoring capability than MIDI based on an individual satellite precipitation dataset, and had statistically strong correlation in particular with 1 month SPI/SPEI over a wide range of bio-climatic zones spanning from arid to humid. Moreover it showed significantly higher correlations with EVI anomalies than SPI/SPEI. The results demonstrated the reliability and superiority of MIDI in monitoring meteorological drought with the ability to work in all weather conditions. Therefore, MIDI provides a gateway to employing satellite microwave remote sensing for reliable meteorological drought monitoring, with the potential for long-term drought assessments as well as near-real-time drought monitoring using operational satellites.
2. Seasonal and interannual variations in carbon fluxes in East Asia semi-arid grasslands
   Zhao, H., G. Jia*, H. Wang, A. Zhang, X. Xu. Science of Total Environment: 2019 ,668 ,1128-1138, doi: 10.1016/j.scitotenv.2019.02.378 摘要  Semiarid regions have substantial interannual variation in carbon exchange between terrestrial ecosystem and atmosphere but the diverse responses of carbon fluxes to climate variability are poorly known. We compared carbon exchange processes and the responses to environmental factors in a meadow steppe at Tongyu (TY) and a typical steppe at Maodeng (MD) using long-term continuous eddy covariance measurements. TY precipitation was 25% greater than MD. Both grasslands had interannual fluctuations of carbon sink and source and acted as weak carbon sinks averagely (−22.9 ± 41.0 gCm−2 yr−1 for TY and − 11.8 ± 45.0 gCm−2 yr−1 for MD). The seasonal dynamics of carbon fluxes were significantly related to water availability at MD but more strongly related to air temperature at TY. During dry years, the controlling effect of water availability on carbon fluxes increased. Summer precipitation and soil moisture played key roles in the interannual variations in carbon fluxes in both grasslands. At MD, net carbon uptake was negatively related to summer air temperature likely because warming induced water deficit decreased photosynthesis. Greenness index derived from PhenoCam images captured key phenological phases and diverse magnitude of canopy dynamics. The index was correlated with seasonal and annual variations in carbon fluxes at both grasslands, suggesting the potential of PhenoCam for monitoring the spatial and temporal variations in canopy dynamics in different semiarid grasslands.
3. Heterogeneous spring phenology shifts affected by climate: supportive evidence from two remotely sensed vegetation indices
   Xu, X., W.J. Riley, C.D. Koven, G. Jia*. Environmental Research Communications: 2019 ,1(9) ,091004, doi: 10.1088/2515-7620/ab3d79 摘要  The Northern Hemisphere spring greenup (SG) has advanced between 0–12 days per decade since early 1980s as inferred from multiple satellite time series. The wide range of SG shifts is mainly due to the fact that these studies cover different periods and regions, and using different satellite records. Assessing the spatial heterogeneity of SG trends associated with different satellites is essential for robustly interpreting phenological dynamics and their responses to climate. We investigated the heterogeneity of the SG trends and their responses to climate variability with two satellite products (1) Terra Moderate Resolution Imaging Spectroradiometer (MODIS) and (2) Advanced Very High Resolution Radiometer (AVHRR) over the period 2001–2013. Both MODIS and AVHRR agreed in showing the spatial distribution of mean SG, and SG advancement in northern Canada, the eastern United States, and Russia, and SG delay in western North America, parts of Baltic Europe, and East Asia. However, we identified contrasting MODIS and AVHRR SG trends in the northern high latitudes. Our analyses of correlations between SG and preseason climate drivers indicated that temperature dominated the interannual variability of SG. Preseason, the period preceding SG and highly correlated with the timing of SG has experienced much stronger warming than the spring season. MODIS and AVHRR indicated consistent temperature sensitivity of SG across biomes, even though the MODIS inferred SG is better correlated and more sensitive to temperature across biomes as compared to AVHRR. The sensitivities of SG to temperature across biomes is stable but with a slight increase over 2001–2013, in comparison with that over 1988–2000. The increased SG-temperature sensitivity is associated with increased precipitation during the spring season, which regulated the sensitivity of SG to spring temperature.
4. The contribution of intensified urbanization effects on surface warming trend in China
   Shi, Z., G. Jia*, Y. Hu, Y. Zhou. Theoretical and Applied Climatology: 2019 ,in press ,doi: 10.1007/s00704-019-02892-y 摘要  Historical temperature records are often partially biased by the urban heat island (UHI) effect. However, the exact magnitude of these biases is an ongoing, controversial scientific question, especially in regions like China where urbanization has greatly increased in recent decades. Previous studies have mainly used statistical information and selected static population targets, or urban areas in a particular year, to classify urban-rural stations and estimate the influence of urbanization on observed warming trends. However, there is a lack of consideration for the dynamic processes of urbanization. The Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), and Pearl River Delta (PRD) are three major urban agglomerations in China which were selected to investigate the spatiotemporal heterogeneity of urban expansion effects on observed warming trends in this study. Based on remote sensing (RS) data, urban area expansion processes were taken into consideration and the relationship between urban expansion rates and warming trends was investigated using data from 975 meteorological stations throughout China. Although urban areas constitute less than 1% of land in China, more than 90% of the meteorological stations experienced urban land use change and the average urban expansion rate was 0.33%/a. There was also a significant positive relationship between observed warming trends and urban expansion rates. Background warming, without the influence of urbanization and extra warming induced by urbanization processes, was estimated using a linear regression model based on observed warming trends and urban expansion rates. On average, urbanization led to an additional annual warming of 0.034 ± 0.005 °C/10a. This urbanization warming effect was 0.050 ± 0.007 °C/10a for minimum temperatures and 0.008 ± 0.004 °C/10a for maximum temperatures. Moreover, it appeared that urbanization induced greater warming on the minimum temperature during the cold season and maximum temperature during the warm season.
5. Comparison of surface and canopy urban heat islands within megacities of eastern China
   Hu, Y., M. Hou, G. Jia*, C. Zhao, X. Zhen, Y. Xu. ISPRS Journal of Photogrammetry and Remote Sensing: 2019 ,156 ,160-168, doi: 10.1016/j.isprsjprs.2019.08.012 摘要  Urban heat island (UHI) can be characterized and quantified to understand the modification of urban surfaces on the local and regional climate. This study examines UHI variation across three megacities that are located in rapid urbanization regions in eastern China (Beijing, Shanghai and Guangzhou). These cities are located within a warm temperate climate zone, north subtropical climate zone, and lower subtropical climate zone, respectively. Satellite-based land surface temperature (LST) data and air temperature records from 2003 to 2016 were used to identify surface urban heat island (SUHI) and canopy urban heat island (CUHI), respectively. Generally, the average annual SUHI is higher than the CUHI, with the greatest UHIs appearing in Beijing (SUHI: 2.33 ± 0.18 °C, CUHI: 1.45 ± 0.54 °C). UHI changes across latitudes were negatively related to humidity variation, with higher UHI in drier climates. Seasonal UHI analysis suggests that a lower SUHI would occur in winter and a higher UHI in spring and summer, except for Guangzhou. CUHI in dry season was higher than in wet season for all three megacities, and the largest CUHI (2.10 ± 0.33 °C) appeared in winter in Beijing. Various patterns of seasonal cycles of SUHI and CUHI were related to monthly precipitation and solar insolation. Annual average daytime SUHI was higher than the nighttime SUHI, and larger daytime SUHI appeared in Guangzhou, contrasting with Shanghai and Beijing. The difference between SUHI and CUHI for all seasons was also high in Guangzhou. UHI changes were considered to be altered by warm and wet conditions in mega-cities of eastern China, and heat transportation from urban surface to urban canopy provided some possible understanding of the UHI change.