scholarly journals Robust Future Changes in Temperature Variability under Greenhouse Gas Forcing and the Relationship with Thermal Advection

2016 ◽  
Vol 29 (6) ◽  
pp. 2221-2236 ◽  
Author(s):  
Caroline R. Holmes ◽  
Tim Woollings ◽  
Ed Hawkins ◽  
Hylke de Vries
Keyword(s):  
Greenhouse Gas ◽  
Temperature Gradients ◽  
Extreme Weather Events ◽  
Sea Temperature ◽  
Near Surface ◽  
Thermal Advection ◽  
Northern Latitudes ◽  
Projected Changes ◽  
The Tropics ◽  
Change In Mean

Abstract Recent temperature extremes have highlighted the importance of assessing projected changes in the variability of temperature as well as the mean. A large fraction of present-day temperature variance is associated with thermal advection, as anomalous winds blow across the land–sea temperature contrast, for instance. Models project robust heterogeneity in the twenty-first-century warming pattern under greenhouse gas forcing, resulting in land–sea temperature contrasts increasing in summer and decreasing in winter and the pole-to-equator temperature gradient weakening in winter. In this study, future changes in monthly variability of near-surface temperature in the 17-member ensemble ESSENCE (Ensemble Simulations of Extreme Weather Events under Nonlinear Climate Change) are assessed. In winter, variability in midlatitudes decreases whereas in very high latitudes and the tropics it increases. In summer, variability increases over most land areas and in the tropics, with decreasing variability in high latitude oceans. Multiple regression analysis is used to determine the contributions to variability changes from changing temperature gradients and circulation patterns. Thermal advection is found to be of particular importance in the Northern Hemisphere winter midlatitudes, where the change in mean state temperature gradients alone could account for over half the projected changes. Changes in thermal advection are also found to be important in summer in Europe and coastal areas, although less so than in winter. Comparison with CMIP5 data shows that the midlatitude changes in variability are robust across large regions, particularly high northern latitudes in winter and middle northern latitudes in summer.

scholarly journals Projected Changes in Climate Extremes Using CMIP6 Simulations Over SREX Regions

2021 ◽  
Vol 5 (3) ◽  
pp. 481-497
Author(s):  
Mansour Almazroui ◽  
Fahad Saeed ◽  
Sajjad Saeed ◽  
Muhammad Ismail ◽  
Muhammad Azhar Ehsan ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Extreme Events ◽  
First Century ◽  
Maximum Temperature ◽  
Annual Maximum ◽  
Temperature And Precipitation ◽  
Projected Change ◽  
Twenty First Century ◽  
Projected Changes ◽  
The Tropics

AbstractThis paper presents projected changes in extreme temperature and precipitation events by using Coupled Model Intercomparison Project phase 6 (CMIP6) data for mid-century (2036–2065) and end-century (2070–2099) periods with respect to the reference period (1985–2014). Four indices namely, Annual maximum of maximum temperature (TXx), Extreme heat wave days frequency (HWFI), Annual maximum consecutive 5-day precipitation (RX5day), and Consecutive Dry Days (CDD) were investigated under four socioeconomic scenarios (SSP1-2.6; SSP2-4.5; SSP3-7.0; SSP5-8.5) over the entire globe and its 26 Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) regions. The projections show an increase in intensity and frequency of hot temperature and precipitation extremes over land. The intensity of the hottest days (as measured by TXx) is projected to increase more in extratropical regions than in the tropics, while the frequency of extremely hot days (as measured by HWFI) is projected to increase more in the tropics. Drought frequency (as measured by CDD) is projected to increase more over Brazil, the Mediterranean, South Africa, and Australia. Meanwhile, the Asian monsoon regions (i.e., South Asia, East Asia, and Southeast Asia) become more prone to extreme flash flooding events later in the twenty-first century as shown by the higher RX5day index projections. The projected changes in extremes reveal large spatial variability within each SREX region. The spatial variability of the studied extreme events increases with increasing greenhouse gas concentration (GHG) and is higher at the end of the twenty-first century. The projected change in the extremes and the pattern of their spatial variability is minimum under the low-emission scenario SSP1-2.6. Our results indicate that an increased concentration of GHG leads to substantial increases in the extremes and their intensities. Hence, limiting CO2 emissions could substantially limit the risks associated with increases in extreme events in the twenty-first century.

scholarly journals Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations

2019 ◽  
Vol 32 (19) ◽  
pp. 6467-6490 ◽  
Author(s):  
Kimmo Ruosteenoja ◽  
Timo Vihma ◽  
Ari Venäläinen
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
Global Climate Models ◽  
Near Surface ◽  
Wind Speeds ◽  
The North ◽  
Seasonal Wind ◽  
Projected Changes

Abstract Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.

The stability of the stratospheric ozone layer during the end-Permian eruption of the Siberian Traps

2007 ◽  
Vol 365 (1856) ◽  
pp. 1843-1866 ◽  
Author(s):  
David J Beerling ◽  
Michael Harfoot ◽  
Barry Lomax ◽  
John A Pyle
Keyword(s):  
Organic Matter ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Ultraviolet B ◽  
Large Reservoir ◽  
Near Surface ◽  
Siberian Traps ◽  
Northern Latitudes ◽  
The Stability ◽  
Mutagenic Effects

The discovery of mutated palynomorphs in end-Permian rocks led to the hypothesis that the eruption of the Siberian Traps through older organic-rich sediments synthesized and released massive quantities of organohalogens, which caused widespread O 3 depletion and allowed increased terrestrial incidence of harmful ultraviolet-B radiation (UV-B, 280–315 nm; Visscher et al . 2004 Proc. Natl Acad. Sci. USA 101 , 12 952–12 956). Here, we use an extended version of the Cambridge two-dimensional chemistry–transport model to evaluate quantitatively this possibility along with two other potential causes of O 3 loss at this time: (i) direct effects of HCl release by the Siberian Traps and (ii) the indirect release of organohalogens from dispersed organic matter. According to our simulations, CH 3 Cl released from the heating of coals alone caused comparatively minor O 3 depletion (5–20% maximum) because this mechanism fails to deliver sufficiently large amounts of Cl into the stratosphere. The unusual explosive nature of the Siberian Traps, combined with the direct release of large quantities of HCl, depleted the model O 3 layer in the high northern latitudes by 33–55%, given a main eruptive phase of less than or equal to 200 kyr. Nevertheless, O 3 depletion was most extensive when HCl release from the Siberian Traps was combined with massive CH 3 Cl release synthesized from a large reservoir of dispersed organic matter in Siberian rocks. This suite of model experiments produced column O 3 depletion of 70–85% and 55–80% in the high northern and southern latitudes, respectively, given eruption durations of 100–200 kyr. On longer eruption time scales of 400–600 kyr, corresponding O 3 depletion was 30–40% and 20–30%, respectively. Calculated year-round increases in total near-surface biologically effective (BE) UV-B radiation following these reductions in O 3 layer range from 30–60 (kJ m −2  d −1 ) BE up to 50–100 (kJ m −2  d −1 ) BE . These ranges of daily UV-B doses appear sufficient to exert mutagenic effects on plants, especially if sustained over tens of thousands of years, unlike either rising temperatures or SO 2 concentrations.

Projected changes in pyroconvective conditions in the Iberian Peninsula at the end of the 21st century

2021 ◽  
Author(s):  
Martín Senande-Rivera ◽  
Gonzalo Miguez-Macho
Keyword(s):  
Iberian Peninsula ◽  
21St Century ◽  
Surface Wind ◽  
Atmospheric Stability ◽  
Weather Conditions ◽  
Fire Season ◽  
Fire Plume ◽  
Near Surface ◽  
Wildfire Spread ◽  
Projected Changes

<p>Extreme wildfire events associated with strong pyroconvection have gained the attention of the scientific community and the society in recent years. Strong convection in the fire plume can influence fire behaviour, as downdrafts can cause abrupt variations in surface wind direction and speed that can result in bursts of unexpected fire propagation. Climate change is expected to increase the length of the fire season and the extreme wildfire potential, so the risk of pyroconvection occurence might be also altered. Here, we analyse atmospheric stability and near-surface fire weather conditions in the Iberian Peninsula at the end of the 21st century to assess the projected changes in pyroconvective risk during favourable weather conditions for wildfire spread.  </p>

scholarly journals Chemical and climatic drivers of radiative forcing due to changes in stratospheric and tropospheric ozone over the 21<sup>st</sup> century

2017 ◽  
Author(s):  
Antara Banerjee ◽  
Amanda C. Maycock ◽  
John A. Pyle
Keyword(s):  
Greenhouse Gas ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Radiative Forcings ◽  
Climatic Drivers ◽  
Ozone Precursor ◽  
Ozone Depleting Substances ◽  
Projected Changes

Abstract. The ozone radiative forcings (RFs) resulting from projected changes in climate, ozone-depleting substances (ODSs), non-methane ozone precursor emissions and methane between the years 2000 and 2100 are calculated using simulations from the UM-UKCA chemistry-climate model. Projected measures to improve air-quality through reductions in tropospheric ozone precursor emissions present a co-benefit for climate, with a net global mean ozone RF of −0.09 Wm−2. This is opposed by a positive ozone RF of 0.07 Wm−2 due to future decreases in ODSs, which is mainly driven by an increase in tropospheric ozone through stratosphere-to-troposphere exchange. An increase in methane abundance by more than a factor of two (as projected by the RCP8.5 scenario) is found to drive an ozone RF of 0.19 Wm−2, which would greatly outweigh the climate benefits of tropospheric non-methane ozone precursor reductions. A third of the ozone RF due to the projected increase in methane results from increases in stratospheric ozone. The sign of the ozone RF due to future changes in climate (including the radiative effects of greenhouse gas concentrations, sea surface temperatures and sea ice changes) is shown to be dependent on the greenhouse gas emissions pathway, with a positive RF (0.06 Wm−2) for RCP4.5 and a negative RF (−0.07 Wm−2) for the RCP8.5 scenario. This dependence arises from differences in the contribution to RF from stratospheric ozone changes.

scholarly journals Uncertainty in water resources availability in the Okavango River Basin as a result of climate change

2010 ◽  
Vol 7 (4) ◽  
pp. 5737-5768 ◽  
Author(s):  
D. A. Hughes ◽  
D. G. Kingston ◽  
M. C. Todd
Keyword(s):  
Climate Change ◽  
Water Resource Management ◽  
Climate Models ◽  
Climate Model ◽  
Management Policy ◽  
Mean Flow ◽  
Considerable Uncertainty ◽  
Okavango River ◽  
Projected Changes ◽  
Change In Mean

Abstract. This paper assesses the hydrological response to scenarios of climate change in the Okavango River catchment in Southern Africa. Climate scenarios are constructed representing different changes in global mean temperature from an ensemble of 7 climate models assessed in the IPCC AR4. The results show a substantial change in mean flow associated with a global warming of 2 °C. However, there is considerable uncertainty in the sign and magnitude of the projected changes between different climate models, implying that the ensemble mean is not an appropriate generalised indicator of impact. The uncertainty in response between different climate model patterns is considerably greater than the range due to uncertainty in hydrological model parameterisation. There is also a clear need to evaluate the physical mechanisms associated with the model projected changes in this region. The implications for water resource management policy are considered.

scholarly journals Interannual response of global ocean hindcasts to a satellite-based correction of precipitation fluxes

2012 ◽  
Vol 9 (2) ◽  
pp. 611-648 ◽  
Author(s):  
A. Storto ◽  
I. Russo ◽  
S. Masina
Keyword(s):  
Ocean Circulation ◽  
Surface Current ◽  
Global Ocean ◽  
Surface Salinity ◽  
Near Surface ◽  
Convergence Zones ◽  
Circumpolar Current ◽  
The Tropics ◽  
Spatially Varying ◽  
The Antarctic

Abstract. We present a methodology to correct precipitation fluxes from the ECMWF atmospheric reanalysis (ERA-Interim) for oceanographic applications. The correction is performed by means of a spatially varying monthly climatological coefficient, computed within the period 1989–2008 by comparison between ERA-Interim and a satellite-based passive microwave precipitation product. ERA-Interim exhibits a systematic over-estimation of precipitation within the inter-tropical convergence zones (up to 3 mm d−1) and under-estimation at mid- and high- latitudes (up to −4 mm d−1). The correction has been validated within eddy-permitting resolution global ocean hindcasts (1989–2009), demonstrating the ability of our strategy in attenuating the 20-yr mean global EMP negative imbalance by 16%, reducing the near-surface salinity fresh bias in the Tropics up to 1 psu and improving the representation of the sea level interannual variability, with an SSH error decrease of 8%. The ocean circulation is also proved to benefit from the correction, especially in correspondence of the Antarctic Circumpolar Current, where the error in the near-surface current speed decreases by a 9%. Finally, we show that the correction leads to volume and freshwater transports that better agree with independent estimates.

scholarly journals Stratospheric ozone in the post-CFC era

2008 ◽  
Vol 8 (6) ◽  
pp. 20223-20237 ◽  
Author(s):  
F. Li ◽  
R. S. Stolarski ◽  
P. A. Newman
Keyword(s):  
Greenhouse Gas ◽  
21St Century ◽  
Crucial Role ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Advective Transport ◽  
Recent Past ◽  
Column Ozone ◽  
The Tropics

Abstract. Vertical and latitudinal changes in the stratospheric ozone in the post-chlorofluorocarbon (CFC) era are investigated using simulations of the recent past and the 21st century with a coupled chemistry-climate model. Model results reveal that, in the 2060s when the stratospheric halogen loading is projected to return to its 1980 values, the extratropical column ozone is significantly higher than that in 1975–1984, but the tropical column ozone does not recover to 1980 values. Upper and lower stratospheric ozone changes in the post-CFC era have very different patterns. Above 15 hPa ozone increases almost latitudinally uniformly by 6 Dobson Unit (DU), whereas below 15 hPa ozone decreases in the tropics by 8 DU and increases in the extratropics by up to 16 DU. The upper stratospheric ozone increase is a photochemical response to greenhouse gas induced strong cooling, and the lower stratospheric ozone changes are consistent with enhanced mean advective transport due to a stronger Brewer-Dobson circulation. The model results suggest that the strengthening of the Brewer-Dobson circulation plays a crucial role in ozone recovery and ozone distributions in the post-CFC era.

scholarly journals Spatial characteristics of aerosol physical properties over the northeastern parts of peninsular India

2005 ◽  
Vol 23 (10) ◽  
pp. 3219-3227 ◽  
Author(s):  
K. Niranjan ◽  
B. Melleswara Rao ◽  
P. S. Brahmanandam ◽  
B. L. Madhavan ◽  
V. Sreekanth ◽  
...  
Keyword(s):  
Physical Properties ◽  
Particle Growth ◽  
Back Trajectory ◽  
Peninsular India ◽  
Near Surface ◽  
Surface Mass ◽  
Accumulation Mode ◽  
Back Trajectory Analysis ◽  
Aerosol Mass ◽  
Northern Latitudes

Abstract. Measurements on aerosol spectral optical depths and near surface mass-size distributions made at several locations in the states of Andhra Pradesh, Orissa and Chattisgarh, constituting the northeastern part of the peninsular India during the ISRO-GBP land campaign-I show significant regional variations in aerosol physical properties. Higher spectral optical depths were observed in the coastal regions and over southern latitudes compared to interior continental regions and northern latitudes. The optical depths, size index "α" and the near surface aerosol mass concentrations indicate a relative abundance of nucleation mode aerosols in the northern latitudes, in contrast to the dominance of the accumulation mode aerosols at the eastern coastal and southern latitudes. The airmass pathways derived from the back trajectory analysis indicate that the higher aerosol population in the accumulation mode, and consequently the higher optical depths in the southern locations, could be due to the transport of aerosol from the polluted north Indian regions via the oceanic region over the Bay of Bengal, where significant particle growth is expected, increasing the population of accumulation mode aerosols over these regions.

scholarly journals Evaluation of the Sensitivity of SMOS L-VOD to Forest Above-Ground Biomass at Global Scale

2020 ◽  
Vol 12 (9) ◽  
pp. 1450
Author(s):  
Arnaud Mialon ◽  
Nemesio J. Rodríguez-Fernández ◽  
Maurizio Santoro ◽  
Sassan Saatchi ◽  
Stéphane Mermoz ◽  
...  
Keyword(s):  
Large Scale ◽  
Correlation Coefficients ◽  
Global Scale ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Northern Latitudes ◽  
Ocean Salinity ◽  
Good Proxy ◽  
Using Data ◽  
The Tropics

The present study evaluates the L band Vegetation Optical Depth (L-VOD) derived from the Soil Moisture and Ocean Salinity (SMOS) satellite to monitor Above Ground Biomass (AGB) at a global scale. Although SMOS L-VOD has been shown to be a good proxy for AGB in Africa and Tropics, little is known about this relationship at large scale. In this study, we further examine this relationship at a global scale using the latest AGB maps from Saatchi et al. and GlobBiomass computed using data acquired during the SMOS period. We show that at a global scale the L-VOD from SMOS is well-correlated with the AGB estimates from Saatchi et al. and GlobBiomass with the Pearson’s correlation coefficients (R) of 0.91 and 0.94 respectively. Although AGB estimates in Africa and the Tropics are well-captured by SMOS L-VOD (R > 0.9), the relationship is less straightforward for the dense forests over the northern latitudes (R = 0.32 and 0.69 with Saatchi et al. and GlobBiomass respectively). This paper gives strong evidence in support of the sensitivity of SMOS L-VOD to AGB estimates at a globale scale, providing an interesting alternative and complement to exisiting sensors for monitoring biomass evolution. These findings can further facilitate research on biomass now that SMOS is providing more than 10 years of data.

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