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

2017 ◽  
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 

scholarly journals On the suitability of current atmospheric reanalyses for regional warming studies over China

2018 ◽  
Vol 18 (11) ◽  
pp. 8113-8136 ◽  
Author(s):  
Chunlüe Zhou ◽  
Yanyi He ◽  
Kaicun Wang
Keyword(s):  
Spatial Patterns ◽  
Southern China ◽  
Regional Climate ◽  
Longwave Radiation ◽  
Northern China ◽  
Atmospheric Model ◽  
Precipitation Frequency ◽  
Regional Warming ◽  
Ensemble Technique ◽  
Downward Longwave Radiation

Abstract. Reanalyses are widely used because they add value to routine observations by generating physically or dynamically consistent and spatiotemporally complete atmospheric fields. Existing studies include extensive discussions of the temporal suitability of reanalyses in studies of global change. This study adds to this existing work by investigating the suitability of reanalyses in studies of regional climate change, in which land–atmosphere interactions play a comparatively important role. In this study, surface air temperatures (Ta) from 12 current reanalysis products are investigated; in particular, the spatial patterns of trends in Ta are examined using homogenized measurements of Ta made at  ∼  2200 meteorological stations in China from 1979 to 2010. The results show that  ∼  80 % of the mean differences in Ta between the reanalyses and the in situ observations can be attributed to the differences in elevation between the stations and the model grids. Thus, the Ta climatologies display good skill, and these findings rebut previous reports of biases in Ta. However, the biases in theTa trends in the reanalyses diverge spatially (standard deviation  =  0.15–0.30 °C decade−1 using 1°  ×  1° grid cells). The simulated biases in the trends in Ta 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 < 0.1) when the spatial patterns of these variables are considered. The biases in the trends in Ta over southern China (on the order of −0.07 °C decade−1) are caused by biases in the trends in Rs, Ld and precipitation frequency on the order of 0.10, −0.08 and −0.06 °C decade−1, respectively. The biases in the trends in Ta over northern China (on the order of −0.12 °C decade−1) result jointly from those in Ld and precipitation frequency. Therefore, improving the simulation of precipitation frequency and Rs helps to maximize the signal component corresponding to regional climate. In addition, the analysis of Ta observations helps represent regional warming in ERA-Interim and JRA-55. Incorporating vegetation dynamics in reanalyses and the use of accurate aerosol information, as in the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), would lead to improvements in the modelling of regional warming. The use of the ensemble technique adopted in the twentieth-century atmospheric model ensemble ERA-20CM significantly narrows the uncertainties associated with regional warming in reanalyses (standard deviation  =  0.15 °C decade−1).

scholarly journals Simultaneous and co-located wind measurements in the middle atmosphere by lidar and rocket-borne techniques

2016 ◽  
Vol 9 (8) ◽  
pp. 3911-3919 ◽  
Author(s):  
Franz-Josef Lübken ◽  
Gerd Baumgarten ◽  
Jens Hildebrand ◽  
Francis J. Schmidlin
Keyword(s):  
Middle Atmosphere ◽  
Systematic Difference ◽  
Horizontal Distance ◽  
In Situ Method ◽  
Time Period ◽  
Meridional Winds ◽  
Wind Measurements ◽  
In Situ Observations ◽  
Mean Differences

Abstract. We present the first comparison of a new lidar technique to measure winds in the middle atmosphere, called DoRIS (Doppler Rayleigh Iodine Spectrometer), with a rocket-borne in situ method, which relies on measuring the horizontal drift of a target (“starute”) by a tracking radar. The launches took place from the Andøya Space Center (ASC), very close to the ALOMAR observatory (Arctic Lidar Observatory for Middle Atmosphere Research) at 69° N. DoRIS is part of a steerable twin lidar system installed at ALOMAR. The observations were made simultaneously and with a horizontal distance between the two lidar beams and the starute trajectories of typically 0–40 km only. DoRIS measured winds from 14 March 2015, 17:00 UTC, to 15 March 2015, 11:30 UTC. A total of eight starute flights were launched successfully from 14 March, 19:00 UTC, to 15 March, 00:19 UTC. In general there is excellent agreement between DoRIS and the in situ measurements, considering the combined range of uncertainties. This concerns not only the general height structures of zonal and meridional winds and their temporal developments, but also some wavy structures. Considering the comparison between all starute flights and all DoRIS observations in a time period of ±20 min around each individual starute flight, we arrive at mean differences of typically ±5–10 m s−1 for both wind components. Part of the remaining differences are most likely due to the detection of different wave fronts of gravity waves. There is no systematic difference between DoRIS and the in situ observations above 30 km. Below ∼ 30 km, winds from DoRIS are systematically too large by up to 10–20 m s−1, which can be explained by the presence of aerosols. This is proven by deriving the backscatter ratios at two different wavelengths. These ratios are larger than unity, which is an indication of the presence of aerosols.

scholarly journals Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

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.

The Role of Horizontal Temperature Advection on Arctic Amplification

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.

scholarly journals Extreme Precipitation Spatial Analog: In Search of an Alternative Approach for Future Extreme Precipitation in Urban Hydrological Studies

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1032 ◽  
Author(s):  
Ariel Wang ◽  
Francina Dominguez ◽  
Arthur Schmidt
Keyword(s):  
Extreme Precipitation ◽  
General Circulation ◽  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Regional Climate Models ◽  
General Circulation Models ◽  
Precipitation Frequency ◽  
Spatio Temporal ◽  
Climate Change Assessment

In this paper, extreme precipitation spatial analog is examined as an alternative method to adapt extreme precipitation projections for use in urban hydrological studies. The idea for this method is that real climate records from some cities can serve as “analogs” that behave like potential future precipitation for other locations at small spatio-temporal scales. Extreme precipitation frequency quantiles of a 3.16 km 2 catchment in the Chicago area, computed using simulations from North American Regional Climate Change Assessment Program (NARCCAP) Regional Climate Models (RCMs) with L-moment method, were compared to National Oceanic and Atmospheric Administration (NOAA) Atlas 14 (NA14) quantiles at other cities. Variances in raw NARCCAP historical quantiles from different combinations of RCMs, General Circulation Models (GCMs), and remapping methods are much larger than those in NA14. The performance for NARCCAP quantiles tend to depend more on the RCMs than the GCMs, especially at durations less than 24-h. The uncertainties in bias-corrected future quantiles of NARCCAP are still large compared to those of NA14, and increase with rainfall duration. Results show that future 3-h and 30-day rainfall in Chicago will be similar to historical rainfall from Memphis, TN and Springfield, IL, respectively. This indicates that the spatial analog is potentially useful, but highlights the fact that the analogs may depend on the duration of the rainfall of interest.

scholarly journals Regional climate-model performance in Greenland firn derived from in situ observations

1969 ◽  
Vol 35 ◽  
pp. 75-78 ◽  
Author(s):  
Charalampos Charalampidis ◽  
Dirk Van As ◽  
Peter L. Langen ◽  
Robert S. Fausto ◽  
Baptiste Vandecrux ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Model Performance ◽  
Mass Conservation ◽  
Mass Budget ◽  
Run Off ◽  
In Situ Observations

Recent record-warm summers in Greenland (Khan et al. 2015) have started affecting the higher regions of the ice sheet (i.e. the accumulation area), where increased melt has altered the properties of firn (i.e. multi-year snow). At high altitudes, meltwater percolates in the porous snow and firn, where it refreezes. The result is mass conservation, as the refrozen meltwater is essentially stored (Harper et al. 2012). However, in some regions increased meltwater refreezing in shallow firn has created thick ice layers. These ice layers act as a lid, and can inhibit meltwater percolation to greater depths, causing it to run off instead (Machguth et al. 2016). Meltwater at the surface also results in more absorbed sunlight, and hence increased melt in the accumulation area (Charalampidis et al. 2015). These relatively poorly understood processes are important for ice-sheet mass-budget projections.

scholarly journals Radiative forcing associated with a springtime case of Bodélé and Sudan dust transport over West Africa

2010 ◽  
Vol 10 (4) ◽  
pp. 8811-8858 ◽  
Author(s):  
C. Lemaître ◽  
C. Flamant ◽  
J. Cuesta ◽  
J.-C. Raut ◽  
P. Chazette ◽  
...  
Keyword(s):  
West Africa ◽  
Heating Rate ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Regional Scale ◽  
Longwave Radiation ◽  
Heating Rates ◽  
Dust Layer ◽  
In Situ Observations

Abstract. The radiative forcing due to mineral dust over West Africa is investigated using the radiative code STREAMER, as well as remote sensing and in situ observations gathered during the African Monsoon Multidisciplinary Analysis Special Observing Period (AMMA SOP). We focus on two days (13 and 14 June 2006) of an intense and long-lasting episode of dust being lifted in remote sources in Chad and Sudan and transported across West Africa in the African easterly jet region, during which airborne operations were conducted at the regional scale, from the southern fringes of the Sahara to the Gulf of Guinea. Profiles of heating rates are computed from airborne LEANDRE 2 and space-borne CALIOP lidar observations using two mineral dust model constrained by airborne in situ data and ground-based sunphotometer obtained during the campaign. Complementary space-borne observations (from MODIS) and in-situ observations such as dropsondes are also used to take into account a realistic infrared contribution of the water vapour. We investigate the variability of the heating rate on the vertical within a dust plume, as well as the contribution of longwave radiation to the heating rate and the radiative forcing of dust during the nighttime. The sensitivity of the so-derived heating rate is also analyzed for some key variables for which the associated uncertainties are quite large. During daytime, the warming associated with the presence of dust was found to be between 1.5 K day−1 and 4 K day−1, on average, depending on altitude and latitude. Strong warming (i.e. heating rates as high as 8 K day−1) was also observed locally in some limited part of the dust plumes. Obviously, during nighttime much smaller values of heating/cooling are retrieved (less than ±1 K day−1) but large enough to modify the low tropospheric equilibrium. Furthermore, cooling is observed as the result of the longwave forcing in the dust layer, while warming is observed below the dust layer, in the monsoon layer.

scholarly journals Responsibility of major emitters for country-level warming and extreme hot years

2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Lea Beusch ◽  
Alexander Nauels ◽  
Lukas Gudmundsson ◽  
Johannes Gütschow ◽  
Carl-Friedrich Schleussner ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Policy ◽  
Regional Climate ◽  
Regional Climate Change ◽  
System Model ◽  
Regional Warming ◽  
Country Level ◽  
The Us ◽  
Per Capita ◽  
Second Year

AbstractThe contributions of single greenhouse gas emitters to country-level climate change are generally not disentangled, despite their relevance for climate policy and litigation. Here, we quantify the contributions of the five largest emitters (China, US, EU-27, India, and Russia) to projected 2030 country-level warming and extreme hot years with respect to pre-industrial climate using an innovative suite of Earth System Model emulators. We find that under current pledges, their cumulated 1991–2030 emissions are expected to result in extreme hot years every second year by 2030 in twice as many countries (92%) as without their influence (46%). If all world nations shared the same fossil CO2 per capita emissions as projected for the US from 2016–2030, global warming in 2030 would be 0.4 °C higher than under actual current pledges, and 75% of all countries would exceed 2 °C of regional warming instead of 11%. Our results highlight the responsibility of individual emitters in driving regional climate change and provide additional angles for the climate policy discourse.

scholarly journals A Long-Term, 1-km Resolution Daily Meteorological Dataset for Modeling and Mapping Permafrost in Canada

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1363
Author(s):  
Yu Zhang ◽  
Budong Qian ◽  
Gang Hong
Keyword(s):  
Land Surface ◽  
Climate Model ◽  
Regional Climate ◽  
Longwave Radiation ◽  
Historical Period ◽  
Air Temperatures ◽  
Downward Longwave Radiation ◽  
High Emission ◽  
Climate Station

Climate warming is causing permafrost thaw and there is an urgent need to understand the spatial distribution of permafrost and its potential changes with climate. This study developed a long-term (1901–2100), 1-km resolution daily meteorological dataset (Met1km) for modeling and mapping permafrost at high spatial resolutions in Canada. Met1km includes eight climate variables (daily minimum, maximum, and mean air temperatures, precipitation, vapor pressure, wind speed, solar radiation, and downward longwave radiation) and is suitable to drive process-based permafrost and other land-surface models. Met1km was developed based on four coarser gridded meteorological datasets for the historical period. Future values were developed using the output of a new Canadian regional climate model under medium-low and high emission scenarios. These datasets were downscaled to 1-km resolution using the re-baselining method based on the WorldClim2 dataset as spatial templates. We assessed Met1km by comparing it to climate station observations across Canada and a gridded monthly anomaly time-series dataset. The accuracy of Met1km is similar to or better than the four coarser gridded datasets. The errors in long-term averages and average seasonal patterns are small. The error occurs mainly in day-to-day fluctuations, thus the error decreases significantly when averaged over 5 to 10 days. Met1km, as a data generating system, is relatively small in data volume, flexible to use, and easy to update when new or improved source datasets are available. The method can also be used to generate similar datasets for other regions, even for the entire global landmass.

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

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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