scholarly journals Amazon Deforestation and Climate Change in a Coupled Model Simulation

2009 ◽  
Vol 22 (21) ◽  
pp. 5686-5697 ◽  
Author(s):  
Paulo Nobre ◽  
Marta Malagutti ◽  
Domingos F. Urbano ◽  
Roberto A. F. de Almeida ◽  
Emanuel Giarolla
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Amazon Basin ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Circulation Model ◽  
Global Ocean ◽  
Spatial Continuity ◽  
The Pacific ◽  
Rainfall Reduction

Abstract The effects of Amazon deforestation on climate change are investigated using twin numerical experiments of an atmospheric general circulation model (AGCM) with prescribed global sea surface temperature and the same AGCM coupled to an ocean GCM (CGCM) over the global tropics. An ensemble approach is adopted, with 10-member ensemble averages of a control simulation compared with perturbed simulations for three scenarios of Amazon deforestation. The latest 20 yr of simulation from each experiment are analyzed. Local surface warming and rainfall reduction are simulated by both models over the Amazon basin. The coupled model presented a rainfall reduction that is nearly 60% larger compared to its control run than those obtained by the AGCM. The results also indicated that both the fraction of the deforested area and the spatial continuity of the vegetated area might be important for modulating global climate variability and change. Additionally, significant remote atmospheric responses to Amazon deforestation scenarios are detected for the coupled simulations, which revealed global ocean and atmosphere circulation changes conducive to enhanced ocean–atmosphere variability over the Pacific Ocean. This, in turn, is interpreted as a manifestation of enhanced El Niño–Southern Oscillation (ENSO) activity over the Pacific and a positive feedback contributing to the extra rainfall reduction over the Amazon on the coupled simulations.

scholarly journals The Effect of a Well-Resolved Stratosphere on Surface Climate: Differences between CMIP5 Simulations with High and Low Top Versions of the Met Office Climate Model

2012 ◽  
Vol 25 (20) ◽  
pp. 7083-7099 ◽  
Author(s):  
S. C. Hardiman ◽  
N. Butchart ◽  
T. J. Hinton ◽  
S. M. Osprey ◽  
L. J. Gray
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Circulation Model ◽  
Climate Simulation ◽  
Reanalysis Dataset ◽  
Quasi Biennial Oscillation ◽  
Surface Climate ◽  
The Impact

Abstract The importance of using a general circulation model that includes a well-resolved stratosphere for climate simulations, and particularly the influence this has on surface climate, is investigated. High top model simulations are run with the Met Office Unified Model for the Coupled Model Intercomparison Project Phase 5 (CMIP5). These simulations are compared to equivalent simulations run using a low top model differing only in vertical extent and vertical resolution above 15 km. The period 1960–2002 is analyzed and compared to observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset. Long-term climatology, variability, and trends in surface temperature and sea ice, along with the variability of the annular mode index, are found to be insensitive to the addition of a well-resolved stratosphere. The inclusion of a well-resolved stratosphere, however, does improve the impact of atmospheric teleconnections on surface climate, in particular the response to El Niño–Southern Oscillation, the quasi-biennial oscillation, and midwinter stratospheric sudden warmings (i.e., zonal mean wind reversals in the middle stratosphere). Thus, including a well-represented stratosphere could improve climate simulation on intraseasonal to interannual time scales.

scholarly journals Evaluation of a unique approach to high-resolution climate modeling using the Model for Prediction Across Scales – Atmosphere (MPAS-A) version 5.1

2019 ◽  
Vol 12 (8) ◽  
pp. 3725-3743 ◽  
Author(s):  
Allison C. Michaelis ◽  
Gary M. Lackmann ◽  
Walter A. Robinson
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Sea Ice ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Spatial Scales ◽  
Coupled Model ◽  
General Circulation Models

Abstract. We present multi-seasonal simulations representative of present-day and future environments using the global Model for Prediction Across Scales – Atmosphere (MPAS-A) version 5.1 with high resolution (15 km) throughout the Northern Hemisphere. We select 10 simulation years with varying phases of El Niño–Southern Oscillation (ENSO) and integrate each for 14.5 months. We use analyzed sea surface temperature (SST) patterns for present-day simulations. For the future climate simulations, we alter present-day SSTs by applying monthly-averaged temperature changes derived from a 20-member ensemble of Coupled Model Intercomparison Project phase 5 (CMIP5) general circulation models (GCMs) following the Representative Concentration Pathway (RCP) 8.5 emissions scenario. Daily sea ice fields, obtained from the monthly-averaged CMIP5 ensemble mean sea ice, are used for present-day and future simulations. The present-day simulations provide a reasonable reproduction of large-scale atmospheric features in the Northern Hemisphere such as the wintertime midlatitude storm tracks, upper-tropospheric jets, and maritime sea-level pressure features as well as annual precipitation patterns across the tropics. The simulations also adequately represent tropical cyclone (TC) characteristics such as strength, spatial distribution, and seasonal cycles for most Northern Hemisphere basins. These results demonstrate the applicability of these model simulations for future studies examining climate change effects on various Northern Hemisphere phenomena, and, more generally, the utility of MPAS-A for studying climate change at spatial scales generally unachievable in GCMs.

scholarly journals An objective tropical Atlantic sea surface temperature gradient index for studies of south Amazon dry-season climate variability and change

2008 ◽  
Vol 363 (1498) ◽  
pp. 1761-1766 ◽  
Author(s):  
Peter Good ◽  
Jason A Lowe ◽  
Mat Collins ◽  
Wilfran Moufouma-Okia
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
General Circulation ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Dry Season ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Sst Gradient

Future changes in meridional sea surface temperature (SST) gradients in the tropical Atlantic could influence Amazon dry-season precipitation by shifting the patterns of moisture convergence and vertical motion. Unlike for the El Niño-Southern Oscillation, there are no standard indices for quantifying this gradient. Here we describe a method for identifying the SST gradient that is most closely associated with June–August precipitation over the south Amazon. We use an ensemble of atmospheric general circulation model (AGCM) integrations forced by observed SST from 1949 to 2005. A large number of tropical Atlantic SST gradient indices are generated randomly and temporal correlations are examined between these indices and June–August precipitation averaged over the Amazon Basin south of the equator. The indices correlating most strongly with June–August southern Amazon precipitation form a cluster of near-meridional orientation centred near the equator. The location of the southern component of the gradient is particularly well defined in a region off the Brazilian tropical coast, consistent with known physical mechanisms. The chosen index appears to capture much of the Atlantic SST influence on simulated southern Amazon dry-season precipitation, and is significantly correlated with observed southern Amazon precipitation. We examine the index in 36 different coupled atmosphere–ocean model projections of climate change under a simple compound 1% increase in CO 2 . Within the large spread of responses, we find a relationship between the projected trend in the index and the Amazon dry-season precipitation trends. Furthermore, the magnitude of the trend relationship is consistent with the inter-annual variability relationship found in the AGCM simulations. This suggests that the index would be of use in quantifying uncertainties in climate change in the region.

Quantification of uncertainty in reference evapotranspiration climate change signals in Belgium

2016 ◽  
Vol 48 (5) ◽  
pp. 1391-1401 ◽  
Author(s):  
Parisa Hosseinzadehtalaei ◽  
Hossein Tabari ◽  
Patrick Willems
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Reference Evapotranspiration ◽  
Coupled Model ◽  
Circulation Model ◽  
Change Context ◽  
Intercomparison Project ◽  
Projected Changes ◽  
Availability Assessment ◽  
Comparable Magnitude

Projections of evapotranspiration form the basis of future runoff and water availability assessment in a climate change context. The scarcity of data or insufficiency of time/funds compels the application of simple reference evapotranspiration (ETo) methods requiring less meteorological inputs for ETo projections which adds uncertainty to the projected changes. This study investigates the bias in ETo climate change signals derived from seven simple temperature- and radiation-based methods (Blaney–Criddle, Hargreaves–Samani, Schendel, Makkink, Turc, Jensen–Haise, Tabari) compared with that from the standard Penman–Monteith FAO 56 method on the basis of 12 general circulation model (GCM) outputs from the Coupled Model Intercomparison Project Phase 5 for central Belgium for four future greenhouse gas scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5). The results show the lack of conformity on the amount of ETo changes between the simple and standard methods, with biases of over 100% for some simple methods. The uncertainty affiliated with ETo methods for monthly ETo changes is smaller but of comparable magnitude to GCM uncertainty, which is usually the major source of uncertainty, and larger for daily extreme ETo changes. This emphasizes the imperative of addressing the uncertainty associated with ETo methods for quantifying the hydrological response to climate change.

scholarly journals Experiments on the effect of tropical Atlantic heating anomalies upon GCM rain forecasts over the Americas

1990 ◽  
Vol 13 ◽  
pp. 57-67
Author(s):  
Julio Buchmann ◽  
Lawrence E. Buja ◽  
Jan Paegle ◽  
Robert E. Dickinson
Keyword(s):  
General Circulation ◽  
Amazon Basin ◽  
Circulation Model ◽  
Real Data ◽  
Forecast Model ◽  
South American ◽  
Tropical Atlantic ◽  
Heating Rates ◽  
The Pacific ◽  
Dominant Influence

A series of real data experiments is performed with a general circulation model in order to ascertain the sensitivity of extended range rain forecasts over the Americas to the structure and magnitude of tropical heating anomalies. The emphasis is upon heat inputs over the tropical Atlantic which have shown particularly significant drying influences over North America in our prior simulations. The heating imposed in the prior experiments is compared to the condensation heating rates that naturally occur in the forecast model, and shown to be excessive by approximately a factor of two. Present experiments reduce the imposed anomaly by a factor of three, and also incorporate sea-surface temperature decreases over the eastern tropical Pacific Ocean. The new experimental results are in many ways consistent with our prior results. The dry North American response is statistically more significant than the South American response, and occurs at least as frequently in the different members of the experimental ensembles as in our prior experiments. The drying effect is accentuated by the presence of East Pacific cooling, but this does not appear to be the dominant influence. Over tropical South America, the Pacific and Atlantic modifications produce compensating influences, with the former dominating dominant, and allowing increased rainfall over the Amazon Basin.

scholarly journals ENSO Amplitude Modulation Associated with the Mean SST Changes in the Tropical Central Pacific Induced by Atlantic Multidecadal Oscillation

2014 ◽  
Vol 27 (20) ◽  
pp. 7911-7920 ◽  
Author(s):  
In-Sik Kang ◽  
Hyun-ho No ◽  
Fred Kucharski
Keyword(s):  
Observational Data ◽  
Wind Stress ◽  
General Circulation ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Circulation Model ◽  
Atlantic Multidecadal Oscillation ◽  
Positive Phase ◽  
Central Pacific ◽  
Easterly Wind

Abstract The mechanism associated with the modulation of the El Niño–Southern Oscillation (ENSO) amplitude caused by the Atlantic multidecadal oscillation (AMO) is investigated by using long-term historical observational data and various types of models. The observational data for the period 1900–2013 show that the ENSO variability weakened during the positive phase of the AMO and strengthened in the negative phase. Such a relationship between the AMO and ENSO amplitude has been reported by a number of previous studies. In the present study the authors demonstrate that the weakening of the ENSO amplitude during the positive phase of the AMO is related to changes of the SST cooling in the eastern and central Pacific accompanied by the easterly wind stress anomalies in the equatorial central Pacific, which were reproduced reasonably well by coupled general circulation model (CGCM) simulations performed with the Atlantic Ocean SST nudged perpetually with the observed SST representing the positive phase of the AMO and the free integration in the other ocean basins. Using a hybrid coupled model, it was determined that the mechanism associated with the weakening of the ENSO amplitude is related to the westward shift and weakening of the ENSO zonal wind stress anomalies accompanied by the westward shift of precipitation anomalies associated with the relatively cold background mean SST over the central Pacific.

scholarly journals Ocean Circulation and Tropical Variability in the Coupled Model ECHAM5/MPI-OM

2006 ◽  
Vol 19 (16) ◽  
pp. 3952-3972 ◽  
Author(s):  
J. H. Jungclaus ◽  
N. Keenlyside ◽  
M. Botzet ◽  
H. Haak ◽  
J.-J. Luo ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Southern Oscillation ◽  
Surface Wind ◽  
Coupled Model ◽  
Circulation Model ◽  
Tropical Variability ◽  
Sst Variability ◽  
The Mean ◽  
Mean State

Abstract This paper describes the mean ocean circulation and the tropical variability simulated by the Max Planck Institute for Meteorology (MPI-M) coupled atmosphere–ocean general circulation model (AOGCM). Results are presented from a version of the coupled model that served as a prototype for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) simulations. The model does not require flux adjustment to maintain a stable climate. A control simulation with present-day greenhouse gases is analyzed, and the simulation of key oceanic features, such as sea surface temperatures (SSTs), large-scale circulation, meridional heat and freshwater transports, and sea ice are compared with observations. A parameterization that accounts for the effect of ocean currents on surface wind stress is implemented in the model. The largest impact of this parameterization is in the tropical Pacific, where the mean state is significantly improved: the strength of the trade winds and the associated equatorial upwelling weaken, and there is a reduction of the model’s equatorial cold SST bias by more than 1 K. Equatorial SST variability also becomes more realistic. The strength of the variability is reduced by about 30% in the eastern equatorial Pacific and the extension of SST variability into the warm pool is significantly reduced. The dominant El Niño–Southern Oscillation (ENSO) period shifts from 3 to 4 yr. Without the parameterization an unrealistically strong westward propagation of SST anomalies is simulated. The reasons for the changes in variability are linked to changes in both the mean state and to a reduction in atmospheric sensitivity to SST changes and oceanic sensitivity to wind anomalies.

scholarly journals The Global Ocean Mass Budget in 1993–2003 Estimated from Sea Level Change

2007 ◽  
Vol 37 (2) ◽  
pp. 203-213 ◽  
Author(s):  
Manfred Wenzel ◽  
Jens Schröter
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Mass Budget ◽  
Ocean Mass ◽  
The Pacific

Abstract The mass budget of the ocean in the period 1993–2003 is studied with a general circulation model. The model has a free surface and conserves mass rather than volume; that is, freshwater is exchanged with the atmosphere via precipitation and evaporation and inflow from land is taken into account. The mass is redistributed by the ocean circulation. Furthermore, the ocean’s volume changes by steric expansion with changing temperature and salinity. To estimate the mass changes, the ocean model is constrained by sea level measurements from the Ocean Topography Experiment (TOPEX)/Poseidon mission as well as by hydrographic data. The modeled ocean mass change within the years 2002–03 compares favorably to measurements from the Gravity Recovery and Climate Experiment (GRACE), and the evolution of the global mean sea level for the period 1993–2003 with annual and interannual variations can be reproduced to a 0.15-cm rms difference. Its trend has been measured as 3.37 mm yr−1 while the constrained model gives 3.34 mm yr−1 considering only the area covered by measurements (3.25 mm yr−1 for the total ocean). A steric rise of 2.50 mm yr−1 is estimated in this period, as is a gain in the ocean mass that is equivalent to an eustatic rise of 0.74 mm yr−1. The amplitude and phase (day of maximum value since 1 January) of the superimposed eustatic annual cycle are also estimated to be 4.6 mm and 278°, respectively. The corresponding values for the semiannual cycle are 0.42 mm and 120°. The trends in the eustatic sea level are not equally distributed. In the Atlantic Ocean (80°S–67°N) the eustatic sea level rises by 1.8 mm yr−1 and in the Indian Ocean (80°S–30°N) it rises by 1.4 mm yr−1, but it falls by −0.20 mm yr−1 in the Pacific Ocean (80°S–67°N). The latter is mainly caused by a loss of mass through transport divergence in the Pacific sector of the Antarctic Circumpolar Current (−0.42 Sv; Sv ≡ 109 kg s−1) that is not balanced by the net surface water supply. The consequence of this uneven eustatic rise is a shift of the oceanic center of mass toward the Atlantic Ocean and to the north.

scholarly journals The Climate of the MIS-13 Interglacial according to HadCM3

2013 ◽  
Vol 26 (23) ◽  
pp. 9696-9712 ◽  
Author(s):  
Helene Muri ◽  
André Berger ◽  
Qiuzhen Yin ◽  
Mehdi Pasha Karami ◽  
Pierre-Yves Barriat
Keyword(s):  
Summer Monsoon ◽  
General Circulation ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Coupled Model ◽  
Circulation Model ◽  
Stationary Wave ◽  
Ocean General Circulation Model ◽  
The Sea Of Japan ◽  
The North

The climate of the Marine Isotopic Stage 13 (MIS-13) is explored in the fully coupled atmosphere–ocean general circulation model the Hadley Centre Coupled Model, version 3 (HadCM3). It is found that the strong insolation forcing at the time imposed a strengthened land–ocean thermal contrast, resulting in an intensified summer monsoon over Asia. The addition of land ice over North America and Eurasia results in a stationary wave feature across the Eurasian continent. This leads to a high pressure anomaly over the Sea of Japan with increased advection of warm moist air onto the Chinese landmasses. This in turn reinforces the East Asian summer monsoon (EASM), highlighting the counterintuitive notion that, depending on the background insolation and its size, ice can indeed contribute to strengthening the EASM. The modeling results support the geological record indication of a strong EASM 500 000 years ago. Furthermore, Arctic Oscillation, El Niño–Southern Oscillation, and Indian Ocean dipole–like teleconnection features are discussed in the MIS-13 environment. It is shown that the change in the tropical Pacific sea surface temperature has the potential to impact the North Atlantic climate through an atmospheric “bridge.”

scholarly journals Optimization of dam's spillway design under climate change conditions

2020 ◽  
Vol 22 (4) ◽  
pp. 916-936
Author(s):  
Ahmad Ferdowsi ◽  
Sayed-Farhad Mousavi ◽  
Saeed Farzin ◽  
Hojat Karami
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
Cuckoo Search ◽  
Empirical Method ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Design Flood ◽  
Invasive Weed

Abstract The present research introduces a model to find the best shape of a dam's spillway under climate change impacts, considering a benchmark problem (i.e., Ute Dam's labyrinth spillway in the Canadian River watershed, New Mexico, USA). A spillway design is based not only on historical data but also on the future hydrologic events. Climate variables were predicted for the years 2021–2050 based on three representative concentration pathway (RCP2.6, RCP4.5, and RCP8.5) scenarios of the general circulation model from the fifth phase of the coupled model intercomparison project (CMIP5) using the statistical downscaling model. Streamflow at the USGS 07226500 streamgage was simulated by a rainfall–runoff model with predicted data. Instantaneous peak flow was estimated using an empirical method. Flood frequency analysis was used for the estimation of the design flood. The shuffled frog-leaping algorithm (SFLA) is used to optimize a labyrinth spillway design and its results were compared with two other nature-inspired algorithms: invasive weed optimization (IWO) and cuckoo search (CS). The spillway was optimized once with the actual design flood (16,143 m3/s) and again with the design flood under climate change (12,250 m3/s). Results revealed that optimization with realistic design flood reduced the concrete volume of the spillway by 37% and under climate change by 43% using the SFLA.

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