Showing papers in "Journal of Climate in 2018"
TL;DR: The Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) top-of-atmosphere (TOA), Edition 4.0 (Ed4.0) data product is described in this article.
Abstract: The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) top-of-atmosphere (TOA), Edition 4.0 (Ed4.0), data product is described. EBAF Ed4.0 is an update to EBAF Ed2.8, incorporating all of the Ed4.0 suite of CERES data product algorithm improvements and consistent input datasets throughout the record. A one-time adjustment to shortwave (SW) and longwave (LW) TOA fluxes is made to ensure that global mean net TOA flux for July 2005–June 2015 is consistent with the in situ value of 0.71 W m−2. While global mean all-sky TOA flux differences between Ed4.0 and Ed2.8 are within 0.5 W m−2, appreciable SW regional differences occur over marine stratocumulus and snow/sea ice regions. Marked regional differences in SW clear-sky TOA flux occur in polar regions and dust areas over ocean. Clear-sky LW TOA fluxes in EBAF Ed4.0 exceed Ed2.8 in regions of persistent high cloud cover. Owing to substantial differences in global mean clear-sky TOA fluxes, the net cloud radiative eff...
408 citations
TL;DR: The Simple Ocean Data Assimilation (SODA3) ocean reanalysis with enhancements to model resolution, observation, and forcing datasets, and the addition of a new forcing dataset is described in this paper.
Abstract: This paper describes version 3 of the Simple Ocean Data Assimilation (SODA3) ocean reanalysis with enhancements to model resolution, observation, and forcing datasets, and the addition of a...
340 citations
TL;DR: The algorithm to produce the Clouds and the Earth's Radiant Energy System (CERES) Edition 4.0 (Ed4) Energy Balanced and Filled (EBAF)-surface data product is explained in this article.
Abstract: The algorithm to produce the Clouds and the Earth’s Radiant Energy System (CERES) Edition 4.0 (Ed4) Energy Balanced and Filled (EBAF)-surface data product is explained. The algorithm forces...
264 citations
TL;DR: The Arctic Ocean is currently on a fast track toward seasonally ice-free conditions as discussed by the authors, and large changes are also occuring in the Arctic Ocean due to climate change and human activities.
Abstract: The Arctic Ocean is currently on a fast track toward seasonally ice-free conditions. Although most attention has been on the accelerating summer sea ice decline, large changes are also occu...
254 citations
TL;DR: In this paper, the first global coupled climate models to simulate and predict category 4 and 5 (Saffir-Simpson scale) tropical cyclones and their interannual variations were presented.
Abstract: As one of the first global coupled climate models to simulate and predict category 4 and 5 (Saffir–Simpson scale) tropical cyclones (TCs) and their interannual variations, the High-Resoluti...
153 citations
TL;DR: In this paper, the authors describe a fourth version of the Global Historical Climatology Network (GHCN)-monthly temperature dataset Version 4 (v4) fulfills the goal of aligning GHCNm temperature values w
Abstract: We describe a fourth version of the Global Historical Climatology Network (GHCN)-monthly (GHCNm) temperature dataset Version 4 (v4) fulfills the goal of aligning GHCNm temperature values w
147 citations
TL;DR: In this article, the role of transient Arctic sea ice loss in projected greenhouse gas-induced late-twentieth-to-late-twenty-first-century climate change was investigated using the Geophysical Fluid Dyn...
Abstract: The role of transient Arctic sea ice loss in the projected greenhouse gas–induced late-twentieth- to late-twenty-first-century climate change is investigated using the Geophysical Fluid Dyn...
142 citations
TL;DR: In this paper, changes in the seasonality of precipitation over Africa have high potential for detrimental socioeconomic impacts due to high societal dependence upon seasonal rainfall, and they have been shown to have negative socioeconomic impacts.
Abstract: Changes in the seasonality of precipitation over Africa have high potential for detrimental socioeconomic impacts due to high societal dependence upon seasonal rainfall. Here, for the first...
137 citations
TL;DR: There has been an accelerating interest in forecasting the weather and climate within the subseasonal time range as mentioned in this paper, and the Madden-Julian oscillation (MJO), an organized envelope of tropical conv...
Abstract: There has been an accelerating interest in forecasting the weather and climate within the subseasonal time range. The Madden–Julian oscillation (MJO), an organized envelope of tropical conv...
126 citations
TL;DR: In this article, the authors used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle.
Abstract: Leaf area index (LAI) is increasing throughout the globe, implying the Earth greening. Global modelling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, we used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement by 8% between the early 1980s and the early 2010s is modelled to have caused increases of 12.0 ±2.4 mm yr-1 in evapotranspiration and 12.1 ±2.7 mm yr-1 in precipitation — about 55 ±25% and 28 ±6% of the observed increases in land evapotranspiration and precipitation, respectively. In wet regions, the greening did not significantly decrease runoff and soil moisture because it intensified moisture recycling through a coincident increase of evapotranspiration and precipitation. But in dry regions including Sahel, West Asia, northern India, western United States and the...
123 citations
TL;DR: In this article, a high-resolution regional climate modeling experiment is presented using the Weather Research and Forecasting (WRF) Model to investigate possible changes in tropical cyclones, and the simulation reproduced 30 of the 32 named storms that entered the model domain during this period.
Abstract: Tropical cyclones have enormous costs to society through both loss of life and damage to infrastructure. There is good reason to believe that such storms will change in the future as a result of changes in the global climate system and that such changes may have important socioeconomic implications. Here a high-resolution regional climate modeling experiment is presented using the Weather Research and Forecasting (WRF) Model to investigate possible changes in tropical cyclones. These simulations were performed for the period 2001–13 using the ERA-Interim product for the boundary conditions, thus enabling a direct comparison between modeled and observed cyclone characteristics. The WRF simulation reproduced 30 of the 32 named storms that entered the model domain during this period. The model simulates the tropical cyclone tracks, storm radii, and translation speeds well, but the maximum wind speeds simulated were less than observed and the minimum central pressures were too large. This experiment i...
TL;DR: In this article, an atmospheric general circulation model (AGCM) is forced with patterns of observed sea surface temperature (SST) change and those output from atmosphere-ocean GCM (AOGCM) climate change simulations to demonstrate a strong dependence of climate feedback on the spatial structure of surface temperature change.
Abstract: An atmospheric general circulation model (AGCM) is forced with patterns of observed sea surface temperature (SST) change and those output from atmosphere–ocean GCM (AOGCM) climate change simulations to demonstrate a strong dependence of climate feedback on the spatial structure of surface temperature change. Cloud and lapse rate feedbacks are found to vary the most, depending strongly on the pattern of tropical Pacific SST change. When warming is focused in the southeast tropical Pacific—a region of climatological subsidence and extensive marine low cloud cover—warming reduces the lower-tropospheric stability (LTS) and low cloud cover but is largely trapped under an inversion and hence has little remote effect. The net result is a relatively weak negative lapse rate feedback and a large positive cloud feedback. In contrast, when warming is weak in the southeast tropical Pacific and enhanced in the west tropical Pacific—a strong convective region—warming is efficiently transported throughout the fr...
TL;DR: A convection-permitting multi-year regional climate simulation using the Met Office Unified Model (UM) has been run for the first time on an Africa-wide domain this paper, which is run as part of the Future Climate for Africa (FCFA) Improving Model Processes for African Climate (IMPALA) project.
Abstract: A convection-permitting multiyear regional climate simulation using the Met Office Unified Model has been run for the first time on an Africa-wide domain. The model has been run as part of the Future Climate for Africa (FCFA) Improving Model Processes for African Climate (IMPALA) project, and its configuration, domain, and forcing data are described here in detail. The model [Pan-African Convection-Permitting Regional Climate Simulation with the Met Office UM (CP4-Africa)] uses a 4.5-km horizontal grid spacing at the equator and is run without a convection parameterization, nested within a global atmospheric model driven by observations at the sea surface, which does include a convection scheme. An additional regional simulation, with identical resolution and physical parameterizations to the global model, but with the domain, land surface, and aerosol climatologies of CP4-Africa, has been run to aid in the understanding of the differences between the CP4-Africa and global model, in particular to ...
TL;DR: In this article, a quantitative evaluation of the Madden-Julian oscillation (MJO) prediction skill in state-of-the-art operational models, participating in the subseasonal-to-seasonal (S2S) prediction project was conducted.
Abstract: The Madden–Julian oscillation (MJO), the dominant mode of tropical intraseasonal variability, provides a major source of tropical and extratropical predictability on a subseasonal time scale. This study conducts a quantitative evaluation of the MJO prediction skill in state-of-the-art operational models, participating in the subseasonal-to-seasonal (S2S) prediction project. The relationship of MJO prediction skill with model biases in the mean moisture fields and in the longwave cloud–radiation feedbacks is also investigated.The S2S models exhibit MJO prediction skill out to a range of 12 to 36 days. The MJO prediction skills in the S2S models are affected by both the MJO amplitude and phase errors, with the latter becoming more important at longer forecast lead times. Consistent with previous studies, MJO events with stronger initial MJO amplitude are typically better predicted. It is found that the sensitivity to the initial MJO phase varies notably from model to model.In most models, a notable ...
TL;DR: In this paper, a seasonal perspective is adopted as it is more pertinent than an annual-average one, which can mask offsetting but agriculturally sensitive seasonal hydroclimate variations.
Abstract: Twentieth-century trends in seasonal temperature and precipitation over the African continent are analyzed from observational datasets and historical climate simulations. Given the agricultural economy of the continent, a seasonal perspective is adopted as it is more pertinent than an annual-average one, which can mask offsetting but agriculturally sensitive seasonal hydroclimate variations. Examination of linear trends in seasonal surface air temperature (SAT) shows that heat stress has increased in several regions, including Sudan and northern Africa where the largest SAT trends occur in the warm season. Broadly speaking, the northern continent has warmed more than the southern one in all seasons. Precipitation trends are varied but notable declining trends are found in the countries along the Gulf of Guinea, especially in the source region of the Niger River in West Africa, and in the Congo River basin. Rainfall over the African Great Lakes—one of the largest freshwater repositories—has, howeve...
TL;DR: In this article, the authors examined the joint influence of three oceanic interdecadal signals, i.e., Pacific Decadal Oscillation (PDO), Atlantic MultidecadalOscillation(AMO), and Indian Ocean Basin Mode (IOBM), on the EASMP, which was found not to be simply a linear combination of their individual effects.
Abstract: East Asian summer monsoon precipitation (EASMP) features complicated interdecadal variability with multiple time periods and spatial patterns. Using century-long datasets of HadISST, CRU precipitation and ERA-20C reanalysis, this study examines the joint influence of three oceanic interdecadal signals, i.e., Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and Indian Ocean Basin Mode (IOBM), on the EASMP, which, however, is found not to be simply a linear combination of their individual effects. When PDO and AMO are out of phase, the same sign SST anomalies occur in North Pacific and North Atlantic, and a zonally-orientated teleconnection wave train appears across the Eurasian mid-high latitudes, propagating from North Atlantic to northern East Asia along the Asian westerly jet waveguide. Correspondingly, the interdecadal precipitation anomalies are characterized by a meridional tripole mode over eastern China. When PDO and AMO are in phase, with opposite sign SST anomal...
TL;DR: In this paper, the authors explored the representation of low-frequency variability in the Atlantic region in historical large ensemble and preindustrial control simulations performed with the Community Earth System Model (CESM).
Abstract: There is observational and modeling evidence that low-frequency variability in the North Atlantic has significant implications for the global climate, particularly for the climate of the Northern Hemisphere. This study explores the representation of low-frequency variability in the Atlantic region in historical large ensemble and preindustrial control simulations performed with the Community Earth System Model (CESM). Compared to available observational estimates, it is found that the simulated variability in Atlantic meridional overturning circulation (AMOC), North Atlantic sea surface temperature (NASST), and Sahel rainfall is underestimated on multidecadal time scales but comparable on interannual to decadal time scales. The weak multidecadal North Atlantic variability appears to be closely related to weaker-than-observed multidecadal variations in the simulated North Atlantic Oscillation (NAO), as the AMOC and consequent NASST variability is impacted, to a great degree, by the NAO. Possible re...
TL;DR: In this paper, a teleconnection is nonlinear and nonstationary owing to the superposition of the El Nino-Southern Oscillation (ENSO) in the North Atlantic-European (NAE) region.
Abstract: El Nino–Southern Oscillation (ENSO) exerts an influence on the North Atlantic–European (NAE) region. However, this teleconnection is nonlinear and nonstationary owing to the superposition a...
TL;DR: Wang et al. as discussed by the authors showed that the loss of sea ice over the Barents Sea (SICBS) in March might have influenced the hot drought events over northeastern China (NEC).
Abstract: In July–August (JA) of 2016, northeastern China (NEC) suffered from the most severe hot drought event of the past 50 years, leading to profound impacts on agriculture, the ecosystem, and society. Results indicate that the loss of sea ice over the Barents Sea (SICBS) in March might have influenced the hot drought events over NEC in JA for the period of 1997–2016. Further analyses reveal that lower SICBS is closely related to thinner snow depth over western Eurasia (SDWEA) in April. The decline of SDWEA leads to drier soil from the Yangtze River valley to northern China during May–June, which is favorable for precipitation deficiency over NEC in JA. Besides, the loss of SICBS in March and decline of SDWEA in April are closely related to the polar–Eurasia teleconnection pattern and dry soil over NEC in JA, which provides favorable atmospheric circulation patterns for occurrences of hot droughts. The large ensemble simulations from the Community Earth System Model and the numerical experiments based ...
TL;DR: In this paper, the Ural blocking circulations have been recognized to play an important role in recent winter Eurasian cooling, and observations performed in the field of meteorological modeling have been performed.
Abstract: Winter atmospheric blocking circulations such as Ural blocking (UB) have been recognized to play an important role in recent winter Eurasian cooling. Observational analyses performed here r...
TL;DR: The authors analyzed gridded daily climate (temperature, precipitation, and climatic water deficit) data to identify and characterize the spatiotemporal evolution of the largest WUS droughts of the last 100 years, with an emphasis on severe cores within drought extents.
Abstract: Extensive drought in the western United States (WUS) during the twenty-first century and associated wildfire and tree mortality incidence has highlighted the potential for greater area of severity within widespread droughts. To place recent WUS droughts into a historical context, the authors analyzed gridded daily climate (temperature, precipitation, and climatic water deficit) data to identify and characterize the spatiotemporal evolution of the largest WUS droughts of the last 100 years, with an emphasis on severe cores within drought extents. Cores of droughts during the last 15 years (2000–02 and 2012–14) covered a greater area than in earlier droughts, driven by greater temperature and precipitation extremes. Comparing fire extent and severity before, during, and after drought events using the monitoring trends in burn severity dataset (1984–2014), the authors found fire size and high-severity burn extent were greater during droughts than before or after. Similarly, recent Sierra Nevada fores...
TL;DR: In this article, the verifications of ERA-Interim precipitation and temperature in mainland China were conducted using a global and regional scale model, which is a valid proxy for observations at local and regional scales.
Abstract: ERA-Interim has been widely considered as a valid proxy for observations at global and regional scales. However, the verifications of ERA-Interim precipitation and temperature in mainland C...
TL;DR: In this paper, a comprehensive 1971-2000 climatology of active layer thickness (ALT) and its changes across the entire Northern Hemisphere from 1850 through 2100 is provided, where the Stefan solution based on a thawing index, and the edaphic factor (E factor) are employed to calculate ALT.
Abstract: Variability of active layer thickness (ALT) in permafrost regions is critical for assessments of climate change, water resources, and engineering applications. Detailed knowledge of ALT variations is also important for studies on ecosystem, hydrological, and geomorphological processes in cold regions. The primary objective of this study is therefore to provide a comprehensive 1971–2000 climatology of ALT and its changes across the entire Northern Hemisphere from 1850 through 2100. To accomplish this, in situ observations, the Stefan solution based on a thawing index, and the edaphic factor (E factor) are employed to calculate ALT. The thawing index is derived from (i) the multimodel ensemble mean of 16 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) over 1850–2005, (ii) three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5) for 2006–2100, and (iii) Climatic Research Unit (CRU) gridded observations for 1901–2014. The results show significant spatial variab...
TL;DR: The role of sampling variability in ENSO composites of winter surface air temperature and precipitation over North America during the period 1920-2013 was assessed for observations and ensem....
Abstract: The role of sampling variability in ENSO composites of winter surface air temperature and precipitation over North America during the period 1920–2013 is assessed for observations and ensem...
TL;DR: In this article, a simple Monte Carlo example highlights the advantages of Granger causality, compared to traditional lagged linear regression analysis in situations with one or more highly autocorrelated variables.
Abstract: In climate variability studies, lagged linear regression is frequently used to infer causality. While lagged linear regression analysis can often provide valuable information about causal relationships, lagged regression is also susceptible to overreporting significant relationships when one or more of the variables has substantial memory (autocorrelation). Granger causality analysis takes into account the memory of the data and is therefore not susceptible to this issue. A simple Monte Carlo example highlights the advantages of Granger causality, compared to traditional lagged linear regression analysis in situations with one or more highly autocorrelated variables. Differences between the two approaches are further explored in two illustrative examples applicable to large-scale climate variability studies. Given that Granger causality is straightforward to calculate, Granger causality analysis may be preferable to traditional lagged regression analysis when one or more datasets has large memory.
TL;DR: It is demonstrated that, regardless of the AED dataset used, a log-logistic distribution most optimally fitted the ED time series, and the SEDI showed significant correlations with the standardized precipitation evapotranspiration index (SPEI) across a wide range of regions, particularly for short (<3 month) SPEI time scales.
Abstract: The dataset contains one zip file corresponding to the SEDI. The format of the file is netCDF3. The file contains 1440 longitudes, 720 latitudes and 444 times (from January 1980 to December 2016). Projection is Geographic (WGS84). The SEDI is in standardized units. The dataset is made available under the Open Database License. Any rights in individual contents of the database are licensed under the Database Contents License. Please, read the full ODbL 1.0 license text for the exact terms that apply. Users of the dataset are free to: Share: copy, distribute and use the database, either commercially or non-commercially. Create: produce derivative works from the database. Adapt: modify, transform and build upon the database. Under the following conditions: Attribution: You must attribute any public use of the database, or works produced from the database. For any use or redistribution of the database, or works produced from it, you must make clear to others the license of the original database. Share-Alike: If you publicly use any adapted version of this database, or works produced from an adapted database, you must also offer that adapted database under the ODbL.
TL;DR: In this article, a combination of external radiative forcing and internally generated variability is used to better contextualize these trends and forecast future ones, i.e., to better predict future ones.
Abstract: Recent observed climate trends result from a combination of external radiative forcing and internally generated variability. To better contextualize these trends and forecast future ones, i...
TL;DR: In this article, the authors studied the impact of precipitation over the Arctic Ocean on the basin-scale freshwater and energy budgets of the United States and found that precipitation is one of the most poorly constrained variables in atmospheric reanalyses.
Abstract: Precipitation over the Arctic Ocean has a significant impact on the basin-scale freshwater and energy budgets but is one of the most poorly constrained variables in atmospheric reanalyses. ...
TL;DR: In this paper, the authors compare over 1 million sounding measurements with ERA-Interim reanalysis for the 38-yr period from 1979 to 2016, and provide an improved insight into the spati...
Abstract: We compare over 1 million sounding measurements with ERA-Interim reanalysis for the 38-yr period from 1979 to 2016. The large dataset allows us to provide an improved insight into the spati...
TL;DR: In this paper, a 10-member ensemble from phase 5 of the Coupled Model Intercomparison Project (CMIP5) is used to analyze the Caribbean's future climate when mean global surface air temperatures are 1.5°, 2.0°, and 2.5ºC above preindustrial (1861-1900) values.
Abstract: A 10-member ensemble from phase 5 of the Coupled Model Intercomparison Project (CMIP5) is used to analyze the Caribbean’s future climate when mean global surface air temperatures are 1.5°, 2.0°, and 2.5°C above preindustrial (1861–1900) values. The global warming targets are attained by the 2030s, 2050s, and 2070s respectively for RCP4.5. The Caribbean on average exhibits smaller mean surface air temperature increases than the globe, although there are parts of the region that are always warmer than the global warming targets. In comparison to the present (using a 1971–2000 baseline), the Caribbean domain is 0.5° to 1.5°C warmer at the 1.5°C target, 5%–10% wetter except for the northeast and southeast Caribbean, which are drier, and experiences increases in annual warm spells of more than 100 days. At the 2.0°C target, there is additional warming by 0.2°–1.0°C, a further extension of warm spells by up to 70 days, a shift to a predominantly drier region (5%–15% less than present day), and a greater...