Attributing Observed SST Trends and Subcontinental Land Warming to Anthropogenic Forcing during 1979–2005

Abstract Attribution studies conclude that it is extremely likely that most observed global- and continental-scale surface air temperature (SAT) warming since 1950 was caused by anthropogenic forcing, but some difficulties and uncertainties remain in attribution of warming in subcontinental regions and at time scales less than 50 years. This study uses global observations and CMIP5 simulations with various forcings, covering 1979–2005, and control runs to develop confidence intervals, to attribute regional trends of SAT and sea surface temperature (SST) to natural and anthropogenic causes. Observations show warming, significantly different from natural variations at the 95% confidence level, over one-third of all grid boxes, and averaged over 15 of 21 subcontinental regions and 6 of 10 ocean basins. Coupled simulations forced with all forcing factors, or greenhouse gases only, reproduce observed SST and SAT patterns. Uncoupled AMIP-like atmosphere-only (prescribed SST and atmospheric radiative forcing) simulations reproduce observed SAT patterns. All of these simulations produce consistent net downward longwave radiation patterns. Simulations with natural-only forcing simulate weak warming. Anthropogenic forcing effects are clearly detectable at the 5% significance level at global, hemispheric, and tropical scales and in nine ocean basins and 15 of 21 subcontinental land regions. Attribution results indicate that ocean warming during 1979–2005 for the globe and individual basins is well represented in the CMIP5 multimodel ensemble mean historical simulations. While land warming may occur as an indirect response to oceanic warming, increasing greenhouse gas concentrations tend to be the ultimate source of land warming in most subcontinental regions during 1979–2005.

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On the Suitability of Current Atmospheric Reanalyses for Regional Warming Studies over China

10.5194/acp-2017-966 ◽

2017 ◽

Cited By ~ 1

Author(s):

Chunlüe Zhou ◽

Yanyi He ◽

Kaicun Wang

Keyword(s):

Regional Climate ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Regional Climate Change ◽

Precipitation Frequency ◽

Regional Warming ◽

Downward Longwave Radiation ◽

In Situ Observations ◽

Mean Differences

Abstract. Reanalyses have been widely used because they add value to the routine observations by generating physically/dynamically consistent and spatiotemporally complete atmospheric fields. Existing studies have extensively discussed their temporal suitability in global change study. This study moves forward on their suitability for regional climate change study where land–atmosphere interactions play a more important role. Here, surface air temperature (Ta) from 12 current reanalysis products were investigated, focusing on spatial patterns of Ta trends, using homogenized Ta from 1979 to 2010 at ~ 2200 meteorological stations in China. Results show that ~ 80 % of the Ta mean differences between reanalyses and in-situ observations are attributed to station and model-grid elevation differences, denoting good skill in Ta climatology and rebutting the previously reported Ta biases. However, the Ta trend biases in reanalyses display spatial divergence (standard deviation = 0.15–0.30 °C/decade at 1° × 1° grids). The simulated Ta trend biases correlate well with those of precipitation frequency, surface incident solar radiation (Rs), and atmospheric downward longwave radiation (Ld) among the reanalyses (r = −0.83, 0.80 and 0.77, p

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Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

10.5194/tc-2016-69 ◽

2016 ◽

Author(s):

Kwang-Yul Kim ◽

Benjamin D. Hamlington ◽

Hanna Na ◽

Jinju Kim

Keyword(s):

Heat Flux ◽

Sea Ice ◽

Air Temperature ◽

Surface Air Temperature ◽

Longwave Radiation ◽

The Arctic ◽

Turbulent Heat ◽

Arctic Amplification ◽

Ice Melting ◽

Downward Longwave Radiation

Abstract. Sea ice melting is proposed as a primary reason for the Artic amplification, although physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice melting in the Arctic Ocean and the Arctic amplification. While sea ice melting is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains to be thin in winter only in the Barents-Kara Seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice melting warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be ice free. A 1 % reduction in sea ice concentration in winter leads to ~ 0.76 W m−2 increase in upward heat flux, ~ 0.07 K increase in 850 hPa air temperature, ~ 0.97 W m−2 increase in downward longwave radiation, and ~ 0.26 K increase in surface air temperature. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort Seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara Seas and Laptev, East Siberian, Chukchi, and Beaufort Seas.

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The Role of Horizontal Temperature Advection on Arctic Amplification

Journal of Climate ◽

10.1175/jcli-d-19-0937.1 ◽

2021 ◽

pp. 1-54

Author(s):

Joseph P. Clark ◽

Vivek Shenoy ◽

Steven B. Feldstein ◽

Sukyoung Lee ◽

Michael Goss

Keyword(s):

Chukchi Sea ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Warming Trend ◽

Surface Energy Budget ◽

Arctic Amplification ◽

Self Organizing Maps ◽

Temperature Advection ◽

Downward Longwave Radiation ◽

Barents And Kara Seas

AbstractThe wintertime (December – February) 1990 - 2016 Arctic surface air temperature (SAT) trend is examined using self-organizing maps (SOMs). The high dimensional SAT dataset is reduced into nine representative SOM patterns, with each pattern exhibiting a decorrelation time scale about 10 days and having about 85% of its variance coming from intraseasonal timescales. The trend in the frequency of occurrence of each SOM pattern is used to estimate the interdecadal Arctic winter warming trend associated with the SOM patterns. It is found that trends in the SOM patterns explain about one-half of the SAT trend in the Barents and Kara Seas, one-third of the SAT trend around Baffin Bay and two-thirds of the SAT trend in the Chukchi Sea. A composite calculation of each term in the thermodynamic energy equation for each SOM pattern shows that the SAT anomalies grow primarily through the advection of the climatological temperature by the anomalous wind. This implies that a substantial fraction of Arctic amplification is due to horizontal temperature advection that is driven by changes in the atmospheric circulation. An analysis of the surface energy budget indicates that the skin temperature anomalies as well as the trend, although very similar to that of the SAT, are produced primarily by downward longwave radiation.

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The performance of CORDEX-EA-II simulations in simulating seasonal temperature and elevation-dependent warming over the Tibetan Plateau

Climate Dynamics ◽

10.1007/s00382-021-05760-6 ◽

2021 ◽

Author(s):

Xiaorui Niu ◽

Jianping Tang ◽

Deliang Chen ◽

Shuyu Wang ◽

Tinghai Ou ◽

...

Keyword(s):

Tibetan Plateau ◽

Radiative Forcing ◽

Regional Climate ◽

Great Influence ◽

Longwave Radiation ◽

Cumulus Parameterization ◽

The Tibetan Plateau ◽

Seasonal Temperature ◽

Temperature Changes ◽

Downward Longwave Radiation

AbstractTo explore the driving mechanisms of elevation-dependent warming (EDW) over the Tibetan Plateau (TP), the output from a suite of numerical experiments with different cumulus parameterization schemes (CPs) under the Coordinated Regional Climate Downscaling Experiments-East Asia (CORDEX-EA-II) project is examined. Results show that all experiments can broadly capture the observed temperature distributions over the TP with consistent cold biases, and the spread in temperature simulations commonly increases with elevation with the maximum located around 4000–5000 m. Such disagreements among the temperature simulations could to a large extent be explained by their spreads in the surface albedo feedback (SAF). All the experiments reproduce the observed EDW below 5000 m in winter but fail to capture the observed EDW above 4500 m in spring. Further analysis suggests that the simulated EDW during winter is mainly caused by the SAF, and the clear-sky downward longwave radiation (LWclr) plays a secondary role in shaping EDW. The models’ inability in simulating EDW during spring is closely related to the SAF and the surface cloud radiative forcing (CRFs). Furthermore, the magnitude and structure of the simulated EDW are sensitive to the choice of CPs. Different CPs generate diverse snow cover fractions, which can modulate the simulated SAF and its effect on EDW. Also, the CPs show great influence on the LWclr via altering the low-level air temperature. Additionally, the mechanism for different temperature changes among the experiments varies with altitudes during summer and autumn, as the diverse temperature changes appear to be caused by the LWclr for the low altitudes while by the SAF for the middle-high altitudes.

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The impact of a warm moist air intrusion on dynamic and thermodynamic sea ice tendencies in the Arctic.

10.5194/egusphere-egu2020-8418 ◽

2020 ◽

Author(s):

Evelien Dekker

Keyword(s):

Sea Ice ◽

Radiative Forcing ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Arctic Sea Ice ◽

The Arctic ◽

Moist Air ◽

Sea Ice Concentration ◽

Ice Concentration ◽

The Impact

Atmospheric blocking events in the Northern Hemishpere have been related to regional Arctic sea ice decline. During blocking events, pulses of warm and moist air enhance the radiative forcing on the sea ice in winter due to the increased longwave radiation associated with clouds. Several studies have shown that such events are related to regional sea ice concentration decline. Daily sea ice output with the latest version of CICE from the coupled Regional Arctic System model is used to study sea ice tendencies during January-February 2014. In this period there was a follow-up of a Atlantic warm moist air insturion and a Pacific warm moist air intrusion associated with surface air temperature perturbations up to 20 degrees locally.A decline in sea ice concentration during wintertime does not neccesarily mean that ice melt has occurred. The goal of this case study is to distinguish the sea ice response between a dynamic and a thermodynamic component. In this way, we learn how much of the sea ice is advected into another region during such an event and how much the sea ice is lost due to the enhanced forcing and temperature increase.&#160;&#160;&#160;

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Northern Hemisphere Winter Air Temperature Patterns and Their Associated Atmospheric and Ocean Conditions

Journal of Climate ◽

10.1175/jcli-d-19-0533.1 ◽

2020 ◽

Vol 33 (14) ◽

pp. 6165-6186 ◽

Cited By ~ 1

Author(s):

Jiechun Deng ◽

Aiguo Dai ◽

Dorina Chyi

Keyword(s):

Northern Hemisphere ◽

Air Temperature ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Arctic Sea Ice ◽

Northern Eurasia ◽

Self Organizing Map ◽

Downward Longwave Radiation ◽

Ocean Conditions ◽

Hemisphere Winter

AbstractThe Northern Hemisphere (NH) has experienced winter Arctic warming and continental cooling in recent decades, but the dominant patterns in winter surface air temperature (SAT) are not well understood. Here, a self-organizing map (SOM) analysis is performed to identify the leading patterns in winter daily SAT fields from 1979 to 2018, and their associated atmospheric and ocean conditions are also examined. Three distinct winter SAT patterns with two phases of nearly opposite signs and a time scale of 7–12 days are found: one pattern exhibits concurrent SAT anomalies of the same sign over North America (NA) and northern Eurasia, while the other two patterns show SAT anomalies of opposite signs between, respectively, NA and the Bering Sea, and the Kara Sea and East Asia (EA). Winter SAT variations may arise from changes in the SOM frequencies. Specifically, the observed increasing trends of winter cold extremes over NA, central Eurasia, and EA during 1998–2013 can be understood as a result of the increasing occurrences of some specific SAT patterns. These SOMs are closely related to poleward advection of midlatitude warm air and equatorward movements of polar cold airmass. These meridional displacements of cold and warm airmasses cause concurrent anomalies over different regions not only in SAT but also in water vapor and surface downward longwave radiation. Anomalous sea surface temperatures in the tropical Pacific, midlatitude North Pacific, and North Atlantic and anomalous Arctic sea ice concentrations also concur to support and maintain the anomalous atmospheric circulation that causes the SAT anomalies.

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Observations of Stratocumulus Clouds and Their Effect on the Eastern Pacific Surface Heat Budget along 20°S

Journal of Climate ◽

10.1175/jcli-d-11-00618.1 ◽

2012 ◽

Vol 25 (24) ◽

pp. 8542-8567 ◽

Cited By ~ 47

Author(s):

Simon P. de Szoeke ◽

Sandra Yuter ◽

David Mechem ◽

Chris W. Fairall ◽

Casey D. Burleyson ◽

...

Keyword(s):

Radiative Forcing ◽

Heat Budget ◽

Coupled Model ◽

Longwave Radiation ◽

Cloud Fraction ◽

Surface Radiation ◽

Cloud Base ◽

Diurnal Cycles ◽

Downward Longwave Radiation ◽

Stratocumulus Clouds

Abstract Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°–85°W in October–November of 2001–08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitude–vertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation. Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ. Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CB–lifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CB–LCL is 0–200 m and increases 400 m from dawn to 1600 LT, before collapsing in the evening. Despite zonal gradients in boundary layer and cloud vertical structure, surface radiation and cloud radiative forcing are relatively uniform in longitude. When present, clouds reduce solar radiation by 160 W m−2 and radiate 70 W m−2 more downward longwave radiation than clear skies. Coupled Model Intercomparison Project phase 3 (CMIP3) simulations of the climate of the twentieth century show 40 ± 20 W m−2 too little net cloud radiative cooling at the surface. Simulated clouds have correct radiative forcing when present, but models have ~50% too few clouds.

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The effect of realistic mathematics education on student achievement in 8th grades geometric objects teaching

African Educational Research Journal ◽

10.30918/aerj.91.20.205 ◽

2021 ◽

Vol 9 (1) ◽

pp. 20-31

Author(s):

Hasan Huseyin Aksu ◽

Keyword(s):

Academic Success ◽

Traditional Approach ◽

T Test ◽

Learning Activities ◽

Control Group ◽

Structured Interviews ◽

Significance Level ◽

8Th Grade ◽

And Control ◽

Dependent Samples

The purpose of this study is to answer if there is a reasonable difference on academical success of students who get education with traditional and RME approach question on “Teaching geometrical objects to 8th grade students” subject. Study group consists of 47 students which contains 21 experimental and 16 control group from “Ordu Anadolu İmam Hatip High School Project School” in Altinordu, Ordu. Experimental and control group have same academical success level, as the school which this study has runned is a school which accepts students with an exam only. After the experimental and control groups were created, a 25 question pre-test was performed to understand the level of knowledge of the group regarding geometrical objects. The same test was performed on the same groups 8 weeks later as retention test. To determine opinions of the students in experimental group regarding RME and related learning activities, semi-structured interviews are conducted. The data obtained from the pretest, posttest and retention tests were analyzed with t-test for independent samples and t-test for dependent samples and variance analysis for mixed measurements with 0.05 significance level. According to the results, it is seen that learning activities prepared according to RME approach are much more effective than learning activities prepared according to the traditional approach on students’ academic success.

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Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-3751-2014 ◽

2014 ◽

Vol 14 (7) ◽

pp. 3751-3769 ◽

Cited By ~ 21

Author(s):

T. M. Saeed ◽

H. Al-Dashti ◽

C. Spyrou

Keyword(s):

Optical Thickness ◽

Dust Storm ◽

Radiative Forcing ◽

Longwave Radiation ◽

Aerosol Optical Thickness ◽

Radiative Heating ◽

Dust Layer ◽

Surface Level ◽

Maximum Value ◽

Direct Radiative Forcing

Abstract. Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to −0.0234 and −0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude–longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2 and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day−1 between 3 and 5 km, dropped to 1.5 K day−1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day−1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of −0.1 K day−1 at 6 km.

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Air Temperature and Anthropogenic Forcing: Insights from the Solid Earth

Journal of Climate ◽

10.1175/2010jcli3500.1 ◽

2011 ◽

Vol 24 (2) ◽

pp. 569-574 ◽

Cited By ~ 13

Author(s):

Jean O. Dickey ◽

Steven L. Marcus ◽

Olivier de Viron

Keyword(s):

Air Temperature ◽

Decadal Variability ◽

Surface Air Temperature ◽

Radiation Budget ◽

Cloud Formation ◽

Length Of Day ◽

Anthropogenic Forcing ◽

The Core ◽

Earth’S Radiation Budget ◽

Gas Effect

Abstract Earth’s rotation rate [i.e., length of day (LOD)], the angular momentum of the core (CAM), and surface air temperature (SAT) all have decadal variability. Previous investigators have found that the LOD fluctuations are largely attributed to core–mantle interactions and that the SAT is strongly anticorrelated with the decadal LOD. It is shown here that 1) the correlation among these three quantities exists until 1930, at which time anthropogenic forcing becomes highly significant; 2) correcting for anthropogenic effects, the correlation is present for the full span with a broadband variability centered at 78 yr; and 3) this result underscores the reality of anthropogenic temperature change, its size, and its temporal growth. The cause of this common variability needs to be further investigated and studied. Since temperature cannot affect the CAM or LOD to a sufficient extent, the results favor either a direct effect of Earth’s core-generated magnetic field (e.g., through the modulation of charged-particle fluxes, which may impact cloud formation) or a more indirect effect of some other core process on the climate—or yet another process that affects both. In all three cases, their signals would be much smaller than the anthropogenic greenhouse gas effect on Earth’s radiation budget during the coming century.

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